Category: Application Notes

Scratch Resistance Testing of Phone Screen Protectors

Prepared by

Stacey Pereira, Jocelyn Esparza, and Pierre Leroux

Understanding Scratch Resistance in Phone Screen Protectors

Protective coatings on phone screens play a critical role in scratch resistance, adhesion strength, and long-term durability. Over time, scratches, micro-cracks, and coating delamination can reduce optical clarity and reliability — especially in high-use environments. To evaluate how different screen protectors resist mechanical damage, instrumented scratch testing provides quantifiable insight into coating failure mechanisms, including adhesion, cohesion, and fracture behavior.

In this study, NANOVEA PB1000 Mechanical Tester is used to compare TPU vs. tempered-glass screen protectors under controlled progressive loading. Using precise acoustic emission detection, we identify critical failure loads and characterize how each material responds to increasing mechanical stress.

Why Scratch Resistance Testing Matters for Screen Protectors

Many users assume that thicker or harder protectors automatically perform better, but real durability depends on how the material behaves under progressive load, surface deformation, and localized stress. Instrumented scratch testing allows engineers to measure coating adhesion, cohesive strength, surface wear resistance, and the exact loads at which failures initiate or propagate.

By analyzing crack initiation points, delamination behavior, and failure modes, manufacturers can validate screen-protector performance for R&D, quality control, or comparative benchmarking. Nano- and micro-scratch testing offer repeatable, data-driven insight into real-world durability far beyond traditional hardness ratings.

ℹ️ Learn more about scratch and adhesion testing services for coatings and screen protectors.

Scratch Testing Objective:
Measuring Failure Loads in Screen Protectors

The objective of this study is to demonstrate how the NANOVEA PB1000 Mechanical Tester performs repeatable, standardized scratch resistance testing on both polymeric and glass screen protectors. By progressively increasing the applied load, the system detects critical loads for cohesive and adhesive failure, captures acoustic emission signals, and correlates these events with scratch depth, friction force, and surface deformation.

This methodology provides a complete mechanical profile of each protective coating, allowing manufacturers and R&D teams to evaluate material formulations, coating adhesion strength, surface durability, and optimal coating thickness for improved product performance. These scratch evaluations are part of NANOVEA’s broader suite of mechanical testing solutions used to characterize coatings, films, and substrates across R&D, quality control, and production environments.

NANOVEA PB1000 Large-Platform
Mechanical Tester

Scratch Test Parameters and Instrument Setup

The scratch resistance evaluation of TPU and tempered-glass screen protectors was conducted under controlled conditions to ensure repeatability and accurate failure-load detection. The following parameters define the progressive-load scratch testing setup used on the NANOVEA PB1000 Mechanical Tester.

LOAD TYPE	PROGRESSIVE
INITIAL LOAD	0.1 N
FINAL LOAD	12 N
SLIDING SPEED	3.025 mm/min
SLIDING DISTANCE	3 mm
INDENTER GEOMETRY	ROCKWELL (120° CONE)
INDENTER MATERIAL (TIP)	DIAMOND
INDENTER TIP RADIUS	50 µm
ATMOSPHERE	AIR
TEMPERATURE	24 °C (ROOM TEMP)

TABLE 1: Test parameters used for scratch testing

Screen protector sample mounted on the NANOVEA PB1000 Mechanical Tester during progressive-load scratch measurement.

Screen Protector Samples Used for Scratch Resistance Testing

Two commercially available screen protector materials were selected to compare differences in scratch resistance, failure behavior, and mechanical durability. Both samples were mounted securely on the NANOVEA PB1000 Mechanical Tester and evaluated under identical progressive-load conditions to ensure a consistent and unbiased comparison.

The TPU screen protector represents a flexible polymeric film with high elasticity but lower abrasion resistance, while the tempered-glass protector represents a rigid, brittle material designed for high hardness and enhanced impact protection. Testing both materials under the same load profile allows a clear assessment of how material composition, elasticity, and hardness influence scratch failure modes.

TPU Screen Protector

Tempered Glass

FIGURE 1: TPU and tempered-glass screen protectors prepared for scratch resistance testing.

Scratch Test Results: Failure Modes in TPU vs. Tempered Glass Screen Protectors

TYPE OF SCREEN PROTECTOR	CRITICAL LOAD #1 (N)	CRITICAL LOAD #2 (N)
TPU	n/a	2.004 ± 0.063
TEMPERED GLASS	3.608 ± 0.281	7.44 ± 0.995

TABLE 2: Summary of critical loads for each screen protector sample.

Because TPU and tempered-glass screen protectors have fundamentally different mechanical properties, each sample exhibited distinct failure modes and critical load thresholds during progressive-load scratch testing. Table 2 summarizes the measured critical loads for each material.

Critical Load #1 represents the first observable point of cohesive failure under optical microscopy, such as crack initiation or radial fracture.

Critical Load #2 corresponds to the first major event detected through acoustic emission (AE) monitoring, typically representing a larger structural failure or penetration event.

TPU Screen Protector — Flexible Polymer Behavior

The TPU screen protector exhibited only one significant critical event (Critical Load #2). This load corresponds to the point along the scratch track where the film began to lift, peel, or delaminate from the phone screen surface.

Once Critical Load #2 (≈2.00 N) was exceeded, the indenter penetrated sufficiently to cause a visible scratch directly on the phone screen for the remainder of the test. No separate Critical Load #1 event was detectable, consistent with the material’s high elasticity and lower cohesive strength.

Tempered Glass Screen Protector — Brittle Failure Behavior

The tempered-glass screen protector showed two distinct critical loads, characteristic of brittle materials:

Critical Load #1 (≈3.61 N): Radial fractures and crack initiation were observed under the microscope, indicating early cohesive failure of the glass layer.
Critical Load #2 (≈7.44 N): A large AE spike and a sharp increase in scratch depth indicated protector penetration at higher loads.

Although the AE magnitude was higher than TPU, no damage was transferred to the phone screen, demonstrating the tempered-glass protector’s ability to absorb and distribute load before catastrophic failure.

In both materials, Critical Load #2 corresponded to the moment when the indenter broke through the screen protector, confirming the protective limit of each sample.

TPU Screen Protector: Scratch Test Data and Failure Analysis

SCRATCH	CRITICAL LOAD #2 (N)
1	2.033
2	2.047
3	1.931
AVERAGE	2.003
STANDARD DEVIATION	0.052

TABLE 3: Critical loads measured during TPU screen protector scratch testing.

FIGURE 2: Friction force, normal load, acoustic emission (AE), and scratch depth vs. scratch length for the TPU screen protector. (B) Critical Load #2

FIGURE 3: Optical microscopy image of the TPU screen protector at Critical Load #2 (5× magnification; image width 0.8934 mm).

FIGURE 4: Full-length post-scratch image of the TPU screen protector showing the complete scratch track following progressive-load testing.

Tempered Glass Screen Protector: Critical Load Data and Fracture Behavior

SCRATCH	CRITICAL LOAD #1 (N)	CRITICAL LOAD #2 (N)
1	3.923	7.366
2	3.382	6.483
3	3.519	8.468
AVERAGE	3.653	6.925
STANDARD DEVIATION	0.383	0.624

TABLE 4: Critical loads measured during tempered-glass screen protector scratch testing.

ℹ️ For comparison with non-silicate polymer coatings, see our study on PTFE coating wear testing, which highlights failure behavior in low-friction polymer films under similar progressive-load conditions.

FIGURE 5: Friction force, normal load, acoustic emission (AE), and scratch depth vs. scratch length for the tempered-glass screen protector. (A) Critical Load #1 (B) Critical Load #2

FIGURE 6: Optical microscopy images showing the failure locations for Critical Load #1 (left) and Critical Load #2 (right) at 5× magnification (image width: 0.8934 mm).

FIGURE 7: Post-test optical microscopy image of the tempered-glass scratch track, highlighting fracture initiation (CL#1) and the final penetration zone (CL#2) following progressive-load testing.

Conclusion: Scratch Performance Comparison of TPU vs. Tempered Glass Screen Protectors

This study demonstrates how the NANOVEA PB1000 Mechanical Tester delivers controlled, repeatable, and highly sensitive scratch resistance measurements using progressive loading and acoustic emission (AE) detection. By precisely capturing both cohesive and adhesive failure events, the system enables a clear comparison of how TPU and tempered-glass screen protectors behave under increasing mechanical stress.

The experimental results confirm that tempered glass exhibits significantly higher critical loads than TPU, providing superior scratch resistance, delayed fracture initiation, and reliable protection against indenter penetration. TPU’s lower cohesive strength and earlier delamination highlight its limitations in high-stress environments.

After identifying failure loads, the resulting scratch tracks can also be analyzed using a non-contact 3D optical profilometer to measure groove depth, residual deformation, and post-scratch topography. This helps complete the mechanical profile of each material.

The NANOVEA Mechanical Tester is engineered for accurate and repeatable indentation, scratch, and wear testing, and supports ISO- and ASTM-compliant nano and micro modules. Its versatility makes it an ideal solution for evaluating the full mechanical profile of thin films, coatings, polymers, glasses, and substrates across R&D, production, and quality control.

Frequently Asked Questions
About Scratch Resistance Testing

What is scratch resistance testing?

Scratch resistance testing evaluates how a material or coating responds when a diamond stylus applies a progressively increasing load. The test identifies the critical loads where cohesive or adhesive failures occur, providing a quantifiable measure of durability, adhesion strength, and resistance to surface damage.

What’s the difference between cohesive and adhesive failure?

Cohesive failure occurs within the coating or material, such as cracking, tearing, or internal fracture.
Adhesive failure happens when the coating detaches from the substrate, indicating insufficient bonding strength.

The NANOVEA PB1000 detects both using synchronized acoustic emission monitoring, scratch depth tracking, and friction analysis.

Why use a mechanical tester instead of manual methods?

A mechanical tester like the NANOVEA PB1000 provides precise, repeatable, and standardized measurements, ensuring reliable data for R&D, production validation, and quality control. It also offers advanced features, such as acoustic emission detection and real-time depth monitoring, that manual methods cannot deliver.

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Rock Abrasivity Testing with NANOVEA Tribometer

ROCK TRIBOLOGY:ROCK ABRASIVITY TESTING USING NANOVEA TRIBOMETER

Prepared by

DUANJIE LI, PhD

INTRODUCTION

Rocks are composed of grains of minerals. The type and abundance of these minerals, as well as the chemical bonding strength between the mineral grains, determine the mechanical and tribological properties of the rocks. Depending on the geological rock cycles, rocks can undergo transformations and are typically classified into three major types: igneous, sedimentary, and metamorphic. These rocks exhibit different mineral and chemical compositions, permeabilities, and particle sizes, and such characteristics contribute to their varied wear resistance. Rock tribology explores the wear and friction behaviors of rocks in various geological and environmental conditions.

IMPORTANCE OF ROCK ABRASIVE TESTING

Various types of wear against rocks, including abrasion and friction, occur during the drilling process of wells, leading to significant direct and consequential losses attributed to the repair and replacement of drill bits and cutting tools. Therefore, the study of drillability, boreability, cuttability, and abrasivity of rocks are critical in the oil, gas, and mining industries. Rock tribology research plays a pivotal role in the selection of the most efficient and cost-effective drilling strategies, thereby enhancing overall efficiency and contributing to the conservation of materials, energy, and the environment. Additionally, minimizing surface friction is highly advantageous in reducing the interaction between the drilling bit and the rock, resulting in decreased tool wear and improved drilling/cutting efficiency.

MEASUREMENT OBJECTIVE

In this study, we simulated and compared the tribological properties of two types of rocks to showcase the capacity of the NANOVEA T50 Tribometer in measuring the coefficient of friction and wear rate of rocks in a controlled and monitored manner.

NANOVEA T50 Compact
Free Weight Tribometer

THE SAMPLES

TEST PROCEDURE

The coefficient of friction, COF, and the wear resistance of two rock samples were evaluated by the NANOVEA T50 Tribometer using Pin-on-Disc Wear Module. An Al2O3 ball (6 mm diameter) was used as the counter material. The wear track was examined using the NANOVEA Non-Contact Profilometer after the tests. The test parameters are summarized below.

The wear rate, K, was evaluated using the formula K=V/(F×s)=A/(F×n), where V is the worn volume, F is the normal load, s is the sliding distance, A is the cross-sectional area of the wear track, and n is the number of revolutions. Surface roughness and wear track profiles were evaluated with the NANOVEA Optical Profilometer, and the wear track morphology was examined using an optical microscope.

Please note that the Al2O3 ball as a counter material was used as an example in this study. Any solid material with different shapes can be applied using a custom fixture to simulate the actual application situation.

TEST PARAMETERS

SAMPLES	Limestone, Marble
WEAR RING RADIUS	5 mm
NORMAL FORCE	10 N
TEST DURATION	10 min
SPEED	100 rpm

RESULTS & DISCUSSION

The hardness (H) and Elastic Modulus (E) of the limestone and marble samples are compared in FIGURE 1, utilizing the Micro Indentation module of the NANOVEA Mechanical Tester. The limestone sample exhibited lower H and E values, measuring at 0.53 and 25.9 GPa, respectively, in contrast to marble, which recorded values of 1.07 for H and 49.6 GPa for E. The relatively higher variability in the H and E values observed in the limestone sample can be attributed to its greater surface inhomogeneity, stemming from its granulated and porous characteristics.

The evolution of the COF during the wear tests of the two rock samples is depicted in FIGURE 2. The limestone initially experiences a rapid increase in COF to approximately 0.8 at the beginning of the wear test, maintaining this value throughout the duration of the test. This abrupt change in COF can be attributed to the penetration of the Al2O3 ball into the rock sample, resulting from a rapid wear and roughening process occurring at the contact face within the wear track. In contrast, the marble sample exhibits a notable increase in COF to higher values after approximately 5 meters of sliding distance, signifying its superior wear resistance when compared to the limestone.

FIGURE 1: Hardness and Young’s Modulus comparison between limestone and marble samples.

FIGURE 2: Evolution of Coefficient of Friction (COF) in limestone and marble samples during wear tests.

FIGURE 3 compares cross-sectional profiles of the limestone and marble samples after the wear tests, and Table 1 summarizes the results of the wear track analysis. FIGURE 4 shows the wear tracks of the samples under the optical microscope. The wear track evaluation aligns with the COF evolution observation: The marble sample, which maintains a low COF for a longer period, exhibits a lower wear rate of 0.0046 mm³/N m, compared to 0.0353 mm³/N m for the limestone. The superior mechanical properties of marble contribute to its better wear resistance than limestone.

FIGURE 3: Cross-section profiles of the wear tracks.

TABLE 1: Result summary of wear track analysis.

FIGURE 4: Wear tracks under optical microscope.

CONCLUSION

In this study, we showcased the capacity of the NANOVEA Tribometer in evaluating the coefficient of friction and wear resistance of two rock samples, namely marble and limestone, in a controlled and monitored manner. The superior mechanical properties of marble contribute to its exceptional wear resistance. This property makes it challenging to drill or cut in the oil and gas industry. Conversely, it significantly extends its lifetime when used as a high-quality building material, such as floor tiles.

NANOVEA Tribometers offer precise and repeatable wear and friction testing capabilities, adhering to ISO and ASTM standards in both rotative and linear modes. Additionally, it provides optional modules for high-temperature wear, lubrication, and tribocorrosion, all seamlessly integrated into one system. NANOVEA’s unmatched range is an ideal solution for determining the full range of tribological properties of thin or thick, soft or hard coatings, films, substrates, and rock tribology.

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Shot Peened Surface Analysis

SHOT PEENED SURFACE ANALYSIS

USING 3D NON-CONTACT PROFILOMETER

Prepared by

CRAIG LEISING

INTRODUCTION

Shot peening is a process in which a substrate is bombarded with spherical metal, glass, or ceramic beads—commonly referred to as “shot”—at a force intended to induce plasticity on the surface. Analyzing the characteristics before and after peening provides crucial insights for enhancing process comprehension and control. The surface roughness and coverage area of dimples left by the shot are especially noteworthy aspects of interest.

Importance of 3D Non-Contact Profilometer for Shot-Peened Surface Analysis

Unlike traditional contact profilometers, which have traditionally been used for shot-peened surface analysis, 3D non-contact measurement provides a complete 3D image to offer a more comprehensive understanding of coverage area and surface topography. Without 3D capabilities, an inspection will solely rely on 2D information, which is insufficient for characterizing a surface. Understanding the topography, coverage area, and roughness in 3D is the best approach for controlling or improving the peening process. NANOVEA’s 3D Non-Contact Profilometers utilize Chromatic Light technology with a unique capability to measure steep angles found on machined and peened surfaces. Additionally, when other techniques fail to provide reliable data due to probe contact, surface variation, angle, or reflectivity, NANOVEA Profilometers succeed.

MEASUREMENT OBJECTIVE

In this application, the NANOVEA ST400 Non-Contact Profilometer is used to measure raw material and two differently peened surfaces for a comparative review. There is an endless list of surface parameters that can be automatically calculated after the 3D surface scan. Here, we will review the 3D surface and select areas of interest for further analysis, including quantifying and investigating the roughness, dimples, and surface area.

NANOVEA ST400 Standard
Optical 3D Profilometer

THE SAMPLE

RESULTS

STEEL SURFACE

ISO 25178 3D ROUGNESS PARAMETERS

SA	0.399 μm	Average Roughness
Sq	0.516 μm	RMS Roughness
Sz	5.686 μm	Maximum Peak-to-Valley
Sp	2.976 μm	Maximum Peak Height
Sv	2.711 μm	Maximum Pit Depth
Sku	3.9344	Kurtosis
Ssk	-0.0113	Skewness
Sal	0.0028 mm	Auto-Correlation Length
Str	0.0613	Texture Aspect Ratio
Sdar	26.539 mm²	Surface Area
Svk	0.589 μm	Reduced Valley Depth

RESULTS

PEENED SURFACE 1

SURFACE COVERAGE 98.105%

ISO 25178 3D ROUGNESS PARAMETERS

Sa	4.102 μm	Average Roughness
Sq	5.153 μm	RMS Roughness
Sz	44.975 μm	Maximum Peak-to-Valley
Sp	24.332 μm	Maximum Peak Height
Sv	20.644 μm	Maximum Pit Depth
Sku	3.0187	Kurtosis
Ssk	0.0625	Skewness
Sal	0.0976 mm	Auto-Correlation Length
Str	0.9278	Texture Aspect Ratio
Sdar	29.451 mm²	Surface Area
Svk	5.008 μm	Reduced Valley Depth

RESULTS

PEENED SURFACE 2

SURFACE COVERAGE 97.366%

ISO 25178 3D ROUGNESS PARAMETERS

Sa	4.330 μm	Average Roughness
Sq	5.455 μm	RMS Roughness
Sz	54.013 μm	Maximum Peak-to-Valley
Sp	25.908 μm	Maximum Peak Height
Sv	28.105 μm	Maximum Pit Depth
Sku	3.0642	Kurtosis
Ssk	0.1108	Skewness
Sal	0.1034 mm	Auto-Correlation Length
Str	0.9733	Texture Aspect Ratio
Sdar	29.623 mm²	Surface Area
Svk	5.167 μm	Reduced Valley Depth

CONCLUSION

In this shot-peened surface analysis application, we have demonstrated how the NANOVEA ST400 3D Non-Contact Profiler precisely characterizes both the topography and nanometer details of a peened surface. It is evident that both Surface 1 and Surface 2 have a significant impact on all the parameters reported here when compared to the raw material. A simple visual examination of the images reveals the differences between the surfaces. This is further confirmed by observing the coverage area and the listed parameters. In comparison to Surface 2, Surface 1 exhibits a lower average roughness (Sa), shallower dents (Sv), and reduced surface area (Sdar), but a slightly higher coverage area.

From these 3D surface measurements, areas of interest can be readily identified and subjected to a comprehensive array of measurements, including Roughness, Finish, Texture, Shape, Topography, Flatness, Warpage, Planarity, Volume, Step-Height, and others. A 2D cross-section can quickly be chosen for detailed analysis. This information allows for a comprehensive investigation of peened surfaces, utilizing a complete range of surface measurement resources. Specific areas of interest could be further examined with an integrated AFM module. NANOVEA 3D Profilometers offer speeds of up to 200 mm/s. They can be customized in terms of size, speeds, scanning capabilities, and can even comply with Class 1 Clean Room standards. Options like Indexing Conveyor and integration for Inline or Online usage are also available.

A special thanks to Mr. Hayden at IMF for supplying the sample shown in this note. Industrial Metal Finishing Inc. | indmetfin.com

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Paint Surface Morphology

PAINT SURFACE MORPHOLOGY

AUTOMATED REAL-TIME EVOLUTION MONITORING
USING NANOVEA 3D PROFILOMETER

Prepared by

DUANJIE LI, PhD

INTRODUCTION

Protective and decorative properties of paint play a significant role in a variety of industries, including automotive, marine, military, and construction. To achieve desired properties, such as corrosion resistance, UV protection, and abrasion resistance, paint formulas and architectures are carefully analyzed, modified, and optimized.

IMPORTANCE OF 3D NON-CONTACT PROFILOMETER FOR DRYING PAINT SURFACE MORPHOLOGY ANALYSIS

Paint is usually applied in liquid form and undergoes a drying process, which involves the evaporation of solvents and the transformation of the liquid paint into a solid film. During the drying process, the paint surface progressively changes its shape and texture. Different surface finishes and textures can be developed by using additives to modify the surface tension and flow properties of the paint. However, in cases of a poorly formulated paint recipe or improper surface treatment, undesired paint surface failures may occur.

Accurate in situ monitoring of the paint surface morphology during the drying period can provide direct insight into the drying mechanism. Moreover, real-time evolution of surface morphologies is very useful information in various applications, such as 3D printing. The NANOVEA 3D Non-Contact Profilometers measure the paint surface morphology of materials without touching the sample, avoiding any shape alteration that may be caused by contact technologies such as a sliding stylus.

MEASUREMENT OBJECTIVE

In this application, the NANOVEA ST500 Non-Contact Profilometer, equipped with a high-speed line optical sensor, is used to monitor the paint surface morphology during its 1-hour drying period. We showcase the NANOVEA Non-Contact Profilometer’s capability in providing automated real-time 3D profile measurement of materials with continuous shape change.

NANOVEA ST500 Large Area
Optical 3D Profilometer

RESULTS & DISCUSSION

The paint was applied on the surface of a metal sheet, followed immediately by automated measurements of the morphology evolution of the drying paint in situ using the NANOVEA ST500 Non-Contact Profilometer equipped with a high-speed line sensor. A macro had been programmed to automatically measure and record the 3D surface morphology at specific time intervals: 0, 5, 10, 20, 30, 40, 50, and 60 min. This automated scanning procedure enables users to perform scanning tasks automatically by running set procedures in sequence, significantly reducing effort, time, and possible user errors compared to manual testing or repeated scans. This automation proves to be extremely useful for long-term measurements involving multiple scans at different time intervals.

The optical line sensor generates a bright line consisting of 192 points, as shown in FIGURE 1. These 192 light points scan the sample surface simultaneously, significantly increasing the scanning speed. This ensures that each 3D scan is completed quickly to avoid substantial surface changes during each individual scan.

FIGURE 1: Optical line sensor scanning the surface of the drying paint.

The false color view, 3D view, and 2D profile of the drying paint topography at representative times are shown in FIGURE 2, FIGURE 3, and FIGURE 4, respectively. The false color in the images facilitates the detection of features that are not readily discernible. Different colors represent height variations across different areas of the sample surface. The 3D view provides an ideal tool for users to observe the paint surface from different angles. During the first 30 minutes of the test, the false colors on the paint surface gradually change from warmer tones to cooler ones, indicating a progressive decrease in height over time in this period. This process slows down, as shown by the mild color change when comparing the paint at 30 and 60 minutes.

The average sample height and roughness Sa values as a function of the paint drying time are plotted in FIGURE 5. The full roughness analysis of the paint after 0, 30, and 60 min drying time are listed in TABLE 1. It can be observed that the average height of the paint surface rapidly decreases from 471 to 329 µm in the first 30 min of drying time. The surface texture develops at the same time as the solvent vaporizes, leading to an increased roughness Sa value from 7.19 to 22.6 µm. The paint drying process slows down thereafter, resulting in a gradual decrease of the sample height and Sa value to 317 µm and 19.6 µm, respectively, at 60 min.

This study highlights the capabilities of the NANOVEA 3D Non-Contact Profilometer in monitoring the 3D surface changes of the drying paint in real-time, providing valuable insights into the paint drying process. By measuring the surface morphology without touching the sample, the profilometer avoids introducing shape alterations to the undried paint, which can occur with contact technologies like sliding stylus. This non-contact approach ensures accurate and reliable analysis of drying paint surface morphology.

FIGURE 2: Evolution of the drying paint surface morphology at different times.

FIGURE 3: 3D view of the paint surface evolution at different drying times.

FIGURE 4: 2D profile across the paint sample after different drying times.

FIGURE 5: Evolution of the average sample height and roughness value Sa as a function of the paint drying time.

ISO 25178 - Surface Texture Parameters

Drying time (min)	0	5	10	20	30	40	50	60
Sq (µm)	7.91	9.4	10.8	20.9	22.6	20.6	19.9	19.6
Sku	26.3	19.8	14.6	11.9	10.5	9.87	9.83	9.82
Sp (µm)	97.4	105	108	116	125	118	114	112
Sv (µm)	127	70.2	116	164	168	138	130	128
Sz (µm)	224	175	224	280	294	256	244	241
Sa (µm)	4.4	5.44	6.42	12.2	13.3	12.2	11.9	11.8

TABLE 1: Paint roughness at different drying times.

CONCLUSION

In this application, we have showcased the capabilities of the NANOVEA ST500 3D Non-Contact Profilometer in monitoring the evolution of paint surface morphology during the drying process. The high-speed optical line sensor, generating a line with 192 light spots that scan the sample surface simultaneously, has made the study time-efficient while ensuring unmatched accuracy.

The macro function of the acquisition software allows for programming automated measurements of the 3D surface morphology in situ, making it particularly useful for long-term measurement involving multiple scans at specific target time intervals. It significantly reduces the time, effort, and potential for user errors. The progressive changes in surface morphology are continuously monitored and recorded in real-time as the paint dries, providing valuable insights into the paint drying mechanism.

The data shown here represents only a fraction of the calculations available in the analysis software. NANOVEA Profilometers are capable of measuring virtually any surface, whether it’s transparent, dark, reflective, or opaque.

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PTFE Coating Wear Test

PTFE COATING WEAR TEST

USING TRIBOMETER AND MECHANICAL TESTER

Prepared by

DUANJIE LI, PhD

INTRODUCTION

Polytetrafluoroethylene (PTFE), commonly known as Teflon, is a polymer with an exceptionally low coefficient of friction (COF) and excellent wear resistance, depending on the applied loads. PTFE exhibits superior chemical inertness, high melting point of 327°C (620°F), and maintains high strength, toughness, and self-lubrication at low temperatures. The exceptional wear resistance of PTFE coatings makes them highly sought-after in a wide range of industrial applications, such as automotive, aerospace, medical, and, notably, cookware.

IMPORTANCE OF QUANTITATIVE EVALUATION OF PTFE COATINGS

The combination of a super low coeﬃcient of friction (COF), excellent wear resistance, and exceptional chemical inert- ness at high temperatures makes PTFE an ideal choice for non-stick pan coatings. To further enhance its mechanical processes during R&D, as well as ensure optimal control over malfunction prevention and safety measures in the Quality Control process, it is crucial to have a reliable technique for quantity evaluating the tribomechanical processes of PTFE coatings. Precise control over surface friction, wear, and adhesion of the coatings is essential to ensure their intended performance.

MEASUREMENT OBJECTIVE

In this application, the wear process of a PTFE coating for a non-stick pan is simulated using NANOVEA Tribometer in linear reciprocating mode.

NANOVEA T50 Compact
Free Weight Tribometer

In addition, the NANOVEA Mechanical Tester was used to perform a micro scratch adhesion test to determine the critical load of the PTFE coating adhesion failure.

NANOVEA PB1000 Large Platform Mechanical Tester

TEST PROCEDURE

WEAR TEST

LINEAR RECIPROCATING WEAR USING A TRIBOMETER

The tribological behavior of the PTFE coating sample, including the coeﬃcient of friction (COF) and wear resistance, was evaluated using the NANOVEA Tribometer in linear reciprocating mode. A Stainless Steel 440 ball tip with a diameter of 3 mm (Grade 100) was used against the coating. The COF was continuously monitored during the PTFE coating wear test.

The wear rate, K, was calculated using the formula K=V/(F×s)=A/(F×n), where V represents the worn volume, F is the normal load, s is the sliding distance, A is the cross-sectional area of the wear track, and n is the number of strokes. The wear track proﬁles were evaluated using the NANOVEA Optical Proﬁlometer, and the wear track morphology was examined using an optical microscope.

WEAR TEST PARAMETERS

LOAD	30 N
TEST DURATION	5 min
SLIDING RATE	80 rpm
AMPLITUDE OF TRACK	8 mm
REVOLUTIONS	300
BALL DIAMETER	3 mm
BALL MATERIAL	Stainless Steel 440
LUBRICANT	None
ATMOSPHERE	Air
TEMPERATURE	230C (RT)
HUMIDITY	43%

TEST PROCEDURE

SCRATCH TEST

MICRO SCRATCH ADHESION TEST USING MECHANICAL TESTER

The PTFE scratch adhesion measurement was conducted using the NANOVEA Mechanical Tester with a 1200 Rockwell C diamond stylus (200 μm radius) in the Micro Scratch Tester Mode.

To ensure the reproducibility of the results, three tests were performed under identical testing conditions.

SCRATCH TEST PARAMETERS

LOAD TYPE	Progressive
INITIAL LOAD	0.01 mN
FINAL LOAD	20 mN
LOADING RATE	40 mN/min
SCRATCH LENGTH	3 mm
SCRATCHING SPEED, dx/dt	6.0 mm/min
INDENTER GEOMETRY	120o Rockwell C
INDENTER MATERIAL (tip)	Diamond
INDENTER TIP RADIUS	200 μm

RESULTS & DISCUSSION

LINEAR RECIPROCATING WEAR USING A TRIBOMETER

The COF recorded in situ is shown in FIGURE 1. The test sample exhibited a COF of ~0.18 during the ﬁrst 130 revolutions, due to the low stickiness of PTFE. However, there was a sudden increase in COF to ~1 once the coating broke through, revealing the substrate underneath. Following the linear reciprocating tests, the wear track proﬁle was measured using the NANOVEA Non-Contact Optical Proﬁlometer, as shown in FIGURE 2. From the data obtained, the corresponding wear rate was calculated to be ~2.78 × 10-3 mm3/Nm, while the depth of the wear track was determined to be 44.94 µm.

PTFE coating wear test setup on the NANOVEA T50 Tribometer.

FIGURE 1: Evolution of COF during the PTFE coating wear test.

FIGURE 2: Proﬁle extraction of wear track PTFE.

PTFE Before breakthrough

Max COF	0.217
Min COF	0.125
Average COF	0.177

PTFE After breakthrough

Max COF	0.217
Min COF	0.125
Average COF	0.177

TABLE 1: COF before and after breakthrough during the wear test.

RESULTS & DISCUSSION

MICRO SCRATCH ADHESION TEST USING MECHANICAL TESTER

The adhesion of the PTFE coating to the substrate is measured using scratch tests with a 200 µm diamond stylus. The micrograph is shown in FIGURE 3 and FIGURE 4, Evolution of COF, and penetration depth in FIGURE 5. The PTFE coating scratch test results are summarized in TABLE 4. As the load on the diamond stylus increased, it progressively penetrated into the coating, resulting in an increase in the COF. When a load of ~8.5 N was reached, the breakthrough of the coating and exposure of the substrate occurred under high pressure, leading to a high COF of ~0.3. The low St Dev shown in TABLE 2 demonstrates the repeatability of the PTFE coating scratch test conducted using the NANOVEA Mechanical Tester.

FIGURE 3: Micrograph of the full scratch on PTFE (10X).

FIGURE 4: Micrograph of the full scratch on PTFE (10X).

FIGURE 5: Friction graph showing the line of the critical point of failure for PTFE.

*Scratch*	*Point of Failure [N]*	*Frictional Force [N]*	*COF*
1	0.335	0.124	0.285
2	0.337	0.207	0.310
3	0.380	0.229	0.295
Average	8.52	2.47	0.297
St dev	0.17	0.16	0.012

TABLE 2: Summary of Critical Load, Frictional Force, and COF during the scratch test.

CONCLUSION

In this study, we conducted a simulation of the wear process of a PTFE coating for non-stick pans using the NANOVEA T50 Tribometer in linear reciprocating mode. The PTFE coating exhibited a low COF of ~0.18 the coating experienced a breakthrough at around 130 revolutions. The quantitative evaluation of the PTFE coating adhesion to the metal substrate was performed using the NANOVEA Mechanical Tester which determined the critical load of the coating adhesion failure to be ~8.5 N in this test.

The NANOVEA Tribometers oﬀer precise and repeatable wear and friction testing capabilities using ISO and ASTM-compliant rotary and linear modes. They provide optional modules for high-temperature wear, lubrication, and tribocorrosion, all integrated into a single system. This versatility allows users to simulate real-world application environments more accurately and gain a beer understanding of the wear mechanisms and tribological properties of diﬀerent materials.

The NANOVEA Mechanical Testers oﬀer Nano, Micro, and Macro modules, each of which includes ISO and ASTM compliant indentation, scratch, and wear testing modes, providing the widest and most user-friendly range of testing capabilities available in a single system.

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Progressive Wear Mapping of Flooring using Tribometer

Flooring Wear Testing

Progressive Wear Mapping of Flooring using Tribometer with integrated Profilometer

Prepared by

FRANK LIU

INTRODUCTION

Flooring materials are designed to be durable, but they often suﬀer wear and tear from everyday activities such as movement and furniture use. To ensure their longevity, most types of ﬂooring have a protective wear layer that resists damage. However, the thickness and durability of the wear layer vary depending on the ﬂooring type and level of foot traﬃc. In addition, diﬀerent layers within the ﬂooring structure, such as UV coatings, decorative layers, and glaze, have varying wear rates. That’s where progressive wear mapping comes in. Using the NANOVEA T2000 Tribometer with an integrated 3D Non-Contact Proﬁlometer, precise monitoring, and analysis of the performance and longevity of ﬂooring materials can be done. By providing detailed insight into the wear behavior of various ﬂooring materials, scientists and technical professionals can make more informed decisions when selecting and designing new ﬂooring systems.

IMPORTANCE OF PROGRESSIVE WEAR MAPPING FOR FLOOR PANELS

Flooring testing has traditionally centered on the wear rate of a sample to determine its durability against wear. However, progressive wear mapping allows analyzing the sample’s wear rate throughout the test, providing valuable insights into its wear behavior. This in-depth analysis allows for correlations between friction data and wear rate, which can identify the root causes of wear. It should be noted that wear rates are not constant throughout wear tests. Thus, observing the progression of wear gives a more accurate assessment of the sample’s wear. Progressing beyond traditional testing methods, the adoption of progressive wear mapping has contributed to significant advancements in the field of flooring testing.

The NANOVEA T2000 Tribometer with an integrated 3D Non-Contact Profilometer is a groundbreaking solution for wear testing and volume loss measurements. Its ability to move with precision between the pin and the profilometer guarantees the reliability of results by eliminating any deviation in wear track radius or location. But that’s not all – the 3D Non-Contact Profilometer’s advanced capabilities allow for high-speed surface measurements, reducing scanning time to mere seconds. With the capability of applying loads of up to 2,000 N and achieving spinning speeds of up to 5,000 rpm, the NANOVEA T2000 Tribometer offers versatility and precision in the evaluation process. It’s clear that this equipment holds a vital role in progressive wear mapping.

FIGURE 1: Sample set-up prior to wear testing (left) and post-wear test profilometry of the wear track (right).

MEASUREMENT OBJECTIVE

Progressive wear mapping testing was performed on two types of flooring materials: stone and wood. Each sample underwent a total of 7 test cycles, with increasing test durations of 2, 4, 8, 20, 40, 60, and 120 s, allowing for a comparison of wear over time. After each test cycle, the wear track was profiled using the NANOVEA 3D Non-Contact Profilometer. From the data collected by the profiler, the volume of the hole and wear rate can be analyzed using the integrated features in the NANOVEA Tribometer software or our surface analysis software, Mountains.

NANOVEA T2000 High Load
Pneumatic Tribometer

THE SAMPLES

WEAR MAPPING TEST PARAMETERS

LOAD	40 N
TEST DURATION	varies
SPEED	200 rpm
RADIUS	10 mm
DISTANCE	varies
BALL MATERIAL	Tungsten Carbide
BALL DIAMETER	10 mm

Test duration used over the 7 cycles were 2, 4, 8, 20, 40, 60, and 120 seconds, respectively. The distances traveled were 0.40, 0.81, 1.66, 4.16, 8.36, 12.55, and 25.11 meters.

WEAR MAPPING RESULTS

Wood Flooring

*Test Cycle*	*Max COF*	*Min COF*	*Avg. COF*
1	0.335	0.124	0.275
2	0.337	0.207	0.295
3	0.380	0.229	0.329
4	0.393	0.265	0.354
5	0.352	0.205	0.314
6	0.345	0.199	0.312
7	0.315	0.211	0.293

RADIAL ORIENTATION

*Test Cycle*	*Total Volume Loss (µm3*	Total Distance Traveled (m)	Wear Rate (mm/Nm) x10^-5	Instantaneous Wear Rate (mm/Nm) x10^-5
1	296247687	0.40	1833.746	1833.746
2	355245227	1.22	1093.260	181.5637
3	596371326	2.88	898.242	363.1791
4	883747767	7.04	530.629	172.5496
5	1207179951	15.40	360.889	96.69074
6	1472745318	27.95	293.329	52.89311
7	1851319210	53.06	184.343	37.69599

FIGURE 2: Wear rate vs total distance traveled (left)
and instantaneous wear rate vs test cycle (right) for wood flooring.

FIGURE 3: COF graph and 3D view of wear track from test #7 on wood flooring.

FIGURE 4: Cross-Sectional Analysis of Wood Wear Track from Test #7

FIGURE 5: Volume and Area Analysis of Wear Track on Wood Sample Test #7.

For full result details, click here.

WEAR MAPPING RESULTS

Stone Flooring

*Test Cycle*	*Max COF*	*Min COF*	*Avg. COF*
1	0.249	0.035	0.186
2	0.349	0.197	0.275
3	0.294	0.154	0.221
4	0.503	0.124	0.273
5	0.548	0.106	0.390
6	0.510	0.129	0.434
7	0.527	0.181	0.472

RADIAL ORIENTATION

*Test Cycle*	*Total Volume Loss (µm3*	Total Distance Traveled (m)	Wear Rate (mm/Nm) x10^-5	Instantaneous Wear Rate (mm/Nm) x10^-5
1	96278846	0.40	595.957	595.9573
2	804289731	1.22	2475.185	2178.889
3	1316147855	2.88	1982.355	770.9501
4	3136530215	7.04	1883.269	1093.013
5	10821732180	15.40	3235.180	2297.508
6	20174960343	27.95	4018.282	1862.899
7	42512063420	53.06	4233.081	2224.187

FIGURE 6: Wear rate vs total distance travelled (left)
and instantaneous wear rate vs test cycle (right) for stone flooring.

FIGURE 7: COF graph and 3D view of wear track from test #7 on stone flooring.

FIGURE 8: Cross-Sectional Analysis of Stone Wear Track from Test #7.

FIGURE 9: Volume and Area Analysis of Wear Track on Stone Sample Test #7.

For full result details, click here.

DISCUSSION

The instantaneous wear rate is calculated with the following equation:

Where V is the volume of a hole, N is the load, and X is the total distance, this equation describes the wear rate between test cycles. The instantaneous wear rate can be used to better identify changes in wear rate throughout the test.

Both samples have very different wear behaviors. Over time, the wood flooring starts with a high wear rate but quickly drops to a smaller, steady value. For the stone flooring, the wear rate appears to start at a low value and trends to a higher value over cycles. The instantaneous wear rate also shows little consistency. The specific reason for the difference is not certain but may be due to the structure of the samples. The stone flooring seems to consist of loose grain-like particles, which would wear differently compared to the wood’s compact structure. Additional testing and research would be needed to ascertain the cause of this wear behavior.

The data from the coefficient of friction (COF) seems to agree with the observed wear behavior. The COF graph for the wood flooring appears consistent throughout the cycles, complementing its steady wear rate. For the stone flooring, the average COF increases throughout the cycles, similar to how the wear rate also increases with cycles. There are also apparent changes in the shape of the friction graphs, suggesting changes in how the ball is interacting with the stone sample. This is most apparent in cycle 2 and cycle 4.

CONCLUSION

The NANOVEA T2000 Tribometer showcases its ability to perform progressive wear mapping by analyzing the wear rate between two different flooring samples. Pausing the continuous wear test and scanning the surface with the NANOVEA 3D Non-Contact Profilometer provides valuable insights into the material’s wear behavior over time.

The NANOVEA T2000 Tribometer with the integrated 3D Non-Contact Profilometer provides a wide variety of data, including COF (Coefficient of Friction) data, surface measurements, depth readings, surface visualization, volume loss, wear rate, and more. This comprehensive set of information allows users to gain a deeper understanding of the interactions between the system and the sample. With its controlled loading, high precision, ease of use, high loading, wide speed range, and additional environmental modules, the NANOVEA T2000 Tribometer takes tribology to the next level.

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Dynamic Mechanical Analysis of Cork Using Nanoindentation

DYNAMIC MECHANICAL ANALYSIS

OF CORK USING NANOINDENTATION

Prepared by

FRANK LIU

INTRODUCTION

Dynamic Mechanical Analysis (DMA) is a powerful technique used to investigate the mechanical properties of materials. In this application, we focus on the analysis of cork, a widely used material in wine sealing and aging processes. Cork, obtained from the bark of the Quercus suber oak tree, exhibits distinct cellular structures that provide mechanical properties resembling synthetic polymers. In one axis, the cork has honeycomb structure. The two other axes are structured in multiple rectangular-like prisms. This gives cork diﬀerent mechanical properties depending on the orientation being tested.

IMPORTANCE OF DYNAMIC MECHANICAL ANALYSIS (DMA) TESTING IN ASSESSING CORK MECHANICAL PROPERTIES

The quality of corks greatly relies on their mechanical and physical properties, which are crucial for their eﬀectiveness in wine sealing. Key factors determining cork quality include ﬂexibility, insulation, resilience, and impermeability to gas and liquids. By utilizing dynamic mechanical analysis (DMA) testing, we can quantitatively assess the ﬂexibility and resilience properties of corks, providing a reliable method for evaluation.

The NANOVEA PB1000 Mechanical Tester in the Nanoindentation mode enables the characterization of these properties, speciﬁcally Young’s modulus, storage modulus, loss modulus, and tan delta (tan (δ)). DMA testing also allows for the collection of valuable data on phase shift, hardness, stress, and strain of the cork material. Through these comprehensive analyses, we gain deeper insights into the mechanical behavior of corks and their suitability for wine sealing applications.

MEASUREMENT OBJECTIVE

In this study, perform dynamic mechanical analysis (DMA) on four cork stoppers using the NANOVEA PB1000 Mechanical Tester in the Nanoindentation mode. The quality of the cork stoppers is labeled as: 1 – Flor, 2 – First, 3 – Colmated, 4 – Synthetic rubber. DMA indentation tests were conducted in both the axial and radial directions for each cork stopper. By analyzing the mechanical response of the cork stoppers, we aimed to gain insights into their dynamic behavior and evaluate their performance under diﬀerent orientations.

NANOVEA

PB1000

TEST PARAMETERS

MAX FORCE	75 mN
LOADING RATE	150 mN/min
UNLOADING RATE	150 mN/min
AMPLITUDE	5 mN
FREQUENCY	1 Hz
CREEP	60 s

indenter type

Ball

51200 Steel

3 mm Diameter

RESULTS

In the tables and graphs below, the Young’s modulus, storage modulus, loss modulus, and tan delta are compared between each sample and orientation.

Young’s modulus: Stiﬀness; high values indicate stiﬀ, low values indicate ﬂexible.

Storage modulus: Elastic response; energy stored in the material.

Loss modulus: Viscous response; energy lost due to heat.

Tan (δ): Dampening; high values indicate more dampening.

AXIAL ORIENTATION

*Stopper*	*YOUNG’S MODULUS*	*STORAGE MODULUS*	*LOSS MODULUS*	*TAN*
#	*(MPa)*	*(MPa)*	*(MPa)*	*(δ)*
1	22.5675	22.27209	3.624947	0.162964
2	18.54664	18.27153	3.162349	0.17409
3	23.75381	23.47267	3.617819	0.154592
4	23.6972	23.58064	2.347008	0.099539

RADIAL ORIENTATION

*Stopper*	*YOUNG’S MODULUS*	*STORAGE MODULUS*	*LOSS MODULUS*	*TAN*
#	*(MPa)*	*(MPa)*	*(MPa)*	*(δ)*
1	24.78863	24.56542	3.308224	0.134865
2	26.66614	26.31739	4.286216	0.163006
3	44.07867	43.61426	6.365979	0.146033
4	28.04751	27.94148	2.435978	0.087173

YOUNG’S MODULUS

STORAGE MODULUS

LOSS MODULUS

TAN DELTA

Between cork stoppers, the Young’s modulus is not very different when tested in the axial orientation. Only Stopper #2 and #3 showed an apparent difference in the Young’s modulus between the radial and axial direction. As a result, the storage modulus and loss modulus will also be higher in the radial direction than in the axial direction. Stopper #4 shows similar characteristics with the natural cork stoppers, except in the loss modulus. This is quite interesting since it means the natural corks has a more viscous property than the synthetic rubber material.

CONCLUSION

The NANOVEA Mechanical Tester in the Nano Scratch Tester mode allows simulation of many real-life failures of paint coatings and hard coats. By applying increasing loads in a controlled and closely monitored manner, the instrument allows to identify at what load failures occur. This can then be used as a way to determine quantitative values for scratch resistance. The coating tested, with no weathering, is known to have a first crack at about 22 mN. With values closer to 5 mN, it is clear that the 7 year lap has degraded the paint.

Compensating for the original profile allows to obtain corrected depth during the scratch and also to measure the residual depth after the scratch. This gives extra information on the plastic versus elastic behavior of the coating under increasing load. Both cracking and the information on deformation can be of great use for improving the hard coat. The very small standard deviations also show the reproducibility of the technique of the instrument which can help manufacturers improved the quality of their hard coat/paint and study weathering eﬀects.

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Nano Scratch & Mar Testing of Paint on Metal Substrate

Nano Scratch & Mar Testing

of Paint on Metal Substrate

Prepared by

SUSANA CABELLO

INTRODUCTION

Paint with or without hard coat is one of the most commonly used coatings. We see it on cars, on walls, on appliances and virtually anything that needs some protective coatings or simply for aesthetic purposes. The paints that are meant for the protection of the underlying substrate often have chemicals that prevent the paint from catching on fire or simply that prevent it from losing its color or cracking. Often the paint used for aesthetic purposes comes in various colors, but may not be necessarily meant for the protection of its substrate or for a long lifetime.

Nevertheless, all paint suﬀers some weathering over time. Weathering on paint can often change the properties from what the makers intended it to have. It can chip quicker, peel oﬀ with heat, loose color or crack. The diﬀerent property changes of paint over time is why makers oﬀer such a wide selection. Paints are tailored to meet diﬀerent requirements for individual clients.

IMPORTANCE OF NANO SCRATCH TESTING FOR QUALITY CONTROL

A major concern for paint makers is the ability for their product to withstand cracking. Once paint begins to crack, it fails to protect the substrate that it was applied on; therefore, failing to satisfy their client. For example, if a branch happens to stroke the side of a car and immediately after the paint begins to chip oﬀ the makers of the paint would lose business due to their poor quality of paint. The quality of the paint is very important because if the metal under the paint becomes exposed it may begin to rust or corrode due to its new exposure.

Reasons like this apply to several other spectrums such as household and office supplies and electronics, toys, research tools and more. Although the paint may be resistant to cracking when they first apply it to metal coatings, the properties may change over time when some weathering has occurred on the sample. This is why it’s very important to have the paint samples tested at their weathered stage. Although cracking under a high load of stress may be inevitable, the maker must predict how weakening the changes may be over time and how deep the aﬀecting scratch must be in order to provide their consumers with the best possible products.

MEASUREMENT OBJECTIVE

We must simulate the process of scratching in a controlled and monitored manner to observe sample behavior eﬀects. In this application, the NANOVEA PB1000 Mechanical Tester in Nano Scratch Testing mode is used to measure the load required to cause failure to an approximately 7 year old 30-50 μm thick paint sample on a metal substrate.

A 2 μm diamond tipped stylus is used at a progressive load ranging from 0.015 mN to 20.00 mN to scratch the coating. We performed a pre and post scan of the paint with 0.2 mN load in order to determine the value for the true depth of the scratch. The true depth analyzes the plastic and elastic deformation of the sample during testing; whereas, the post-scan only analyzes the plastic deformation of the scratch. The point where the coating fails by cracking is taken as the point of failure. We used the ASTMD7187 as a guide to determine our testing parameters.

We can conclude that having used a weathered sample; therefore, testing a paint sample at its weaker stage, presented us with lower points of failure.

Five tests were performed on this sample in order to

determine the exact failure critical loads.

NANOVEA

PB1000

TEST PARAMETERS

following ASTM D7027

The surface of a Roughness Standard was scanned using a NANOVEA ST400 equipped with a high-speed sensor that generates a bright line of 192 points, as shown in FIGURE 1. These 192 points scan the sample surface at the same time, leading to significantly increased scan speed.

LOAD TYPE	Progressive
INITIAL LOAD	0.015 mN
FINAL LOAD	20 mN
LOADING RATE	20 mN/min
SCRATCH LENGTH	1.6 mm
SCRATCH SPEED, dx/dt	1.601 mm/min
PRE-SCAN LOAD	0.2 mN
POST-SCAN LOAD	0.2 mN

indenter type

Conical

Diamond 90° Cone

2 µm tip radius

RESULTS

This section presents the data collected on the failures during the scratch test. The first section describes the failures observed in the scratch and defines the critical loads that were reported. The next part contains a summary table of the critical loads for all samples, and a graphical representation. The last part presents detailed results for each sample: the critical loads for each scratch, micrographs of each failure, and the graph of the test.

FAILURES OBSERVED AND DEFINITION OF CRITICAL LOADS

CRITICAL FAILURE:

INITIAL DAMAGE

This is the first point at which the damage is observed along the scratch track.

CRITICAL FAILURE:

COMPLETE DAMAGE

At this point, the damage is more significant where the paint is chipping and cracking along the scratch track.

DETAILED RESULTS

* Failure values taken at point of substrate cracking.

CRITICAL LOADS
SCRATCH	INITIAL DAMAGE [mN]	COMPLETE DAMAGE [µm]
1	14.513	4.932
2	3.895	4.838
3	3.917	4.930

AVERAGE	3.988	4.900
STD DEV	0.143	0.054

FIGURE 2: Micrograph of Full Scratch (1000x magniﬁcation).

FIGURE 3: Micrograph of Initial Damage (1000x magniﬁcation).

FIGURE 4: Micrograph of Complete Damage (1000x magniﬁcation).

FIGURE 5: Friction Force and Coeﬃcient of Friction.

FIGURE 6: Surface Profile.

FIGURE 7: True Depth and Residual Depth.

CONCLUSION

The NANOVEA Mechanical Tester in the Nano Scratch Tester mode allows the simulation of many real-life failures of paint coatings and hard coats. By applying increasing loads in a controlled and closely monitored manner, the instrument allows to identify at what load failures occur. This can then be used as a way to determine quantitative values for scratch resistance. The coating tested, with no weathering, is known to have a first crack at about 22 mN. With values closer to 5 mN, it is clear that the 7 year lap has degraded the paint.

Compensating for the original profile allows obtaining corrected depth during the scratch and measuring the residual depth after the scratch. This gives extra information on the plastic versus elastic behavior of the coating under increasing load. Both cracking and the information on deformation can be of great use for improving the hard coat. The very small standard deviations also show the reproducibility of the instrument’s technique which can help manufacturers improve the quality of their hard coat/paint and study weathering eﬀects.

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Roughness Mapping Inspection using 3D Profilometry

ROUGHNESS MAPPING INSPECTION

USING 3D PROFILOMETRY

Prepared by

DUANJIE, PhD

INTRODUCTION

Surface roughness and texture are critical factors that impact the final quality and performance of a product. A thorough understanding of surface roughness, texture, and consistency is essential for selecting the best processing and control measures. Fast, quantifiable, and reliable inline inspection of product surfaces is in need to identify the defective products in time and optimize production line conditions.

IMPORTANCE OF 3D NON-CONTACT PROFILOMETER FOR IN-LINE SURFACE INSPECTION

Surface defects in products result from materials processing and product manufacturing. Inline surface quality inspection ensures the tightest quality control of the end products. NANOVEA 3D Non-Contact Optical Profilers utilize Chromatic Light technology with unique capability to determine the roughness of a sample without contact. The line sensor enables scanning of the 3D profile of a large surface at a high speed. The roughness threshold, calculated in real-time by the analysis software, serves as a fast and reliable pass/fail tool.

MEASUREMENT OBJECTIVE

In this study, the NANOVEA ST400 equipped with a high-speed sensor is used to inspect the surface of a Teﬂon sample with defect to showcase the capability of NANOVEA

Non-Contact Proﬁlometers in providing fast and reliable surface inspection in a production line.

NANOVEA

ST400

RESULTS & DISCUSSION

3D Surface Analysis of the Roughness Standard Sample

FIGURE 2 shows false color views of the Surface Height Map and Roughness Distribution Map of the Roughness Standard Sample. In FIGURE 2a, the Roughness Standard exhibits a slightly slanted surface as represented by the varied color gradient in each of the standard roughness blocks. In FIGURE 2b, homogeneous roughness distribution is shown in diﬀerent roughness blocks, the color of which represents the roughness in the blocks.

FIGURE 3 shows the examples of the Pass/Fail Maps generated by the Analysis Software based on diﬀerent Roughness Thresholds. The roughness blocks are highlighted in red when their surface roughness is above a certain set threshold value. This provides a tool for the user to set up a roughness threshold to determine the quality of a sample surface finish.

FIGURE 1: Optical line sensor scanning on the Roughness Standard sample

a. Surface Height Map:

b. Roughness Map:

FIGURE 2: False color views of the Surface Height Map and Roughness Distribution Map of the Roughness Standard Sample.

FIGURE 3: Pass/Fail Map based on the Roughness Threshold.

Surface Inspection of a Teﬂon Sample with Defects

Surface Height Map, Roughness Distribution Map and Pass/Fail Roughness Threshold Map of the Teﬂon sample surface are shown in FIGURE 4. The Teﬂon Sample has a ridge form at the right center of the sample as shown in the Surface Height Map.

a. Surface Height Map:

The diﬀerent colors in the pallet of FIGURE 4b represents the roughness value on the local surface. The Roughness Map exhibits a homogeneous roughness in the intact area of the Teﬂon sample. However, the defects, in the forms of an indented ring and a wear scar are highlighted in bright color. The user can easily set up a Pass/Fail roughness threshold to locate the surface defects as shown in FIGURE 4c. Such a tool allows users to monitor in situ the product surface quality in the production line and discover defective products in time. The real-time roughness value is calculated and recorded as the products pass by the in-line optical sensor, which can serve as a fast but reliable tool for quality control.

b. Roughness Map:

c. Pass/Fail Roughness Threshold Map:

FIGURE 4: Surface Height Map, Roughness Distribution Map and Pass/Fail Roughness Threshold Map of the Teﬂon sample surface.

CONCLUSION

In this application, we have shown how the NANOVEA ST400 3D Non-Contact Optical Profiler equipped with an optical line sensor works as a reliable quality control tool in an eﬀective and efficient manner.

The optical line sensor generates a bright line of 192 points that scan the sample surface at the same time, leading to significantly increased scan speed. It can be installed in the production line to monitor the surface roughness of the products in situ. The roughness threshold works as a dependable criteria to determine the surface quality of the products, allowing users to notice the defective products in time.

The data shown here represents only a portion of the calculations available in the analysis software. NANOVEA Profilometers measure virtually any surface in fields including Semiconductor, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.

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High Temperature Scratch Hardness using a Tribometer

HIGH TEMPERATURE SCRATCH HARDNESS

USING A TRIBOMETER

Prepared by

DUANJIE, PhD

INTRODUCTION

Hardness measures the resistance of materials to permanent or plastic deformation. Originally developed by a German mineralogist Friedrich Mohs in 1820, scratch hardness test determines the hardness of a material to scratches and abrasion due to friction from a sharp object¹. The Mohs’ scale is a comparative index rather than a linear scale, therefore a more accurate and qualitative scratch hardness measurement was developed as described in ASTM standard G171-03². It measures the average width of the scratch created by a diamond stylus and calculates the scratch hardness number (HSP).

IMPORTANCE OF SCRATCH HARDNESS MEASUREMENT AT HIGH TEMPERATURES

Materials are selected based on the service requirements. For applications involving significant temperature changes and thermal gradients, it is critical to investigate the mechanical properties of materials at high temperatures to be fully aware of the mechanical limits. Materials, especially polymers, usually soften at high temperatures. A lot of mechanical failures are caused by creep deformation and thermal fatigue taking place only at elevated temperatures. Therefore, a reliable technique for measuring hardness at high temperatures is in need to ensure proper selection of the materials for high temperature applications.

MEASUREMENT OBJECTIVE

In this study, the NANOVEA T50 Tribometer measures scratch hardness of a Teflon sample at different temperatures from room temperature to 300ºC. The capability of performing high temperature scratch hardness measurement makes the NANOVEA Tribometer a versatile system for tribological and mechanical evaluations of materials for high temperature applications.

NANOVEA

T50

TEST CONDITIONS

The NANOVEA T50 Free Weight Standard Tribometer was used to perform the scratch hardness tests on a Teflon sample at temperatures ranging from room temperature (RT) to 300°C. Teflon has a melting point of 326.8°C. A conical diamond stylus of apex angle 120° with tip radius of 200 µm was used. The Teflon sample was fixed on the rotative sample stage with a distance of 10 mm to the stage center. The sample was heated up by an oven and tested at temperatures of RT, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C.

TEST PARAMETERS

of the high temperature scratch hardness measurement

NORMAL FORCE	2 N
SLIDING SPEED	1 mm/s
SLIDING DISTANCE	8mm per temp
ATMOSPHERE	Air
TEMPERATURE	RT, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C.

RESULTS & DISCUSSION

The scratch track profiles of the Teflon sample at different temperatures are shown in FIGURE 1 in order to compare the scratch hardness at different elevated temperatures. The material pile-up on the scratch track edges forms as the stylus travels at a constant load of 2 N and ploughs into the Teflon sample, pushing and deforming the material in the scratch track to the side.

The scratch tracks were examined under the optical microscope as shown in FIGURE 2. The measured scratch track widths and calculated scratch hardness numbers (HSP) are summarized and compared in FIGURE 3. The scratch track width measured by the microscope is in agreement with that measured using the NANOVEA Profiler – the Teflon sample exhibits a wider scratch width at higher temperatures. Its scratch track width increases from 281 to 539 µm as the temperature elevates from RT to 300oC, resulting in decreased HSP from 65 to 18 MPa.

The scratch hardness at elevated temperatures can be measured with high precision and repeatability using the NANOVEA T50 Tribometer. It provides an alternative solution from other hardness measurements and makes NANOVEA Tribometers a more complete system for comprehensive high-temperature tribo-mechanical evaluations.

FIGURE 1: Scratch track profiles after the scratch hardness tests at different temperatures.

FIGURE 2: Scratch tracks under the microscope after the measurements at different temperatures.

FIGURE 3: Evolution of the scratch track width and scratch hardness vs. the temperature.

CONCLUSION

In this study, we showcase how the NANOVEA Tribometer measures the scratch hardness at elevated temperatures in compliance to ASTM G171-03. The scratch hardness test at a constant load provides an alternative simple solution for comparing the hardness of materials using the tribometer. The capacity of performing scratch hardness measurements at elevated temperatures makes the NANOVEA Tribometer an ideal tool for evaluating the high temperature tribo-mechanical properties of materials.

The NANOVEA Tribometer also offers precise and repeatable wear and friction testing using ISO and ASTM compliant rotative and linear modes, with optional high temperature wear, lubrication and tribo-corrosion modules available in one pre-integrated system. Optional 3D non-contact profiler is available for high resolution 3D imaging of wear tracks in addition to other surface measurements such as roughness.

1 Wredenberg, Fredrik; PL Larsson (2009). “Scratch testing of metals and polymers: Experiments and numerics”. Wear 266 (1–2): 76
2 ASTM G171-03 (2009), “Standard Test Method for Scratch Hardness of Materials Using a Diamond Stylus”

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Scratch Testing Objective:
Measuring Failure Loads in Screen Protectors

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