ASTM D 3363 test method: Pencil hardness of screen protectors and hybrid glass

by | May 20, 2024 | How-To, Technology and material

testing equipment surface hardness testing astm d3363 and iso 15184

ASTM D 3363 test method: Pencil hardness of screen protectors and hybrid glass

Introduction

In today's digital world, protecting the screens of electronic devices is of the utmost importance. Screen protectors and hybrid glass provide this necessary layer of protection, improving the life and functionality of devices. One of the most commonly used methods for evaluating the hardness of screen protector materials is the ASTM D 3363 test method, which determines the hardness of a surface by scratch hardness pencil testing.

What is ASTM D 3363 - What does surface hardness 3H, 9H mean?

ASTM D 3363 is a standardized test method developed by ASTM International (American Society for Testing and Materials). It specifies the procedures for determining the hardness of coatings and surfaces by using pencils of defined hardness. The test measures the ability of a coating to resist penetration and scratching by a specified pencil lead. The content of ASTM D 3363 corresponds to ISO 15184.

Test method

Sample preparation

The sample, be it a screen protector or hybrid glass, is stuck to a flat, solid surface. It is important that the sample is free of dirt and damage. The display film, bulletproof glass, real glass, tempered glass or hybrid glass must be applied flat and bubble-free to a flat surface. We use Plexiglas, also known as PMMA (polymethyl methacrylate).

durchführung der prüfung der härte der oberfläche von displayfolie und hybridglas

Display protection film or hybrid glass to be tested on a Plexiglas plate. Test equipment for the measurement according to ASTM D 3363 is prepared

setup for testing the surface hardness of screen protectors and hybrid glass

Pencil selection

The ASTM D 3363 test method uses a standardized selection of pencils whose leads have a defined hardness, from 6B (soft) to 9H (hard). At Neoxum, we use pencils from Staedtler with a hardness of 1H to 9H for quality assurance and testing the hardness of our display protection material. The higher the H number, the harder the pencil. Tests with soft pencils, such as HB or B, or softer make little sense from our point of view, as the surface of the screen protector must already have a certain hardness of 3H for screen protectors and 8-9H for hybrid glass.

 

Pencils with pencil hardness from 1H to 9H

Pencils with a pencil hardness of 1H, 2H, 3H, 4H, 5H, 8H and 9H

pencil with hardness grade 2h

Staedtler 2H pencil

Pencil with hardness grade 2H for testing the surface hardness of display films and hybrid glass

pencil for testing the pencil hardness according to astm d 3363

pencil for testing penfilm hardnessl values according to astm d 3363

Pencil for testing pencil hardness according to ASTM D 3363 or ISO 15184

pencil with 4h hardness for testing display protection material and glass

4H pencil from Staedtler

Pencil with 4H hardness for testing display protection material and glass

Execution of the ASTM D 3363 hardness test

Bleistiftvorbereitung

The pencil is held at an angle of 90 degrees to the surface and the lead is prepared by grinding to create a flat, rounded tip.

pencil for testing the pencil hardness according to astm d 3363

Pencil for testing pencil hardness according to ASTM D 3363 or ISO 15184

Test process

The pencil is pressed against the surface with a defined force (known from the standard) and drawn across it. In order to obtain comparable results, it is important to keep both the pencils and the weight pressing on the surface identical. Pencils from different manufacturers show significant differences in pencil hardness, even though they are labeled with the same pencil hardness H. It is therefore all the more important to understand that a pencil hardness of 9H is in principle a very good surface hardness. However, it should be noted that a comparative value is only valid with identical pencils. In addition, the pressure (weight) with which the test was carried out must always be specified. At Neoxum, we test our materials with Staedtler pencils and a weight of 500 g. The weight measured on the pencil tip with the test equipment is 553 g measured with a scale. For internal tests, we even test with a weight of 1000 g.
astm d 3363 pencil hardness test examination

ASTM D 3363 pencil hardness test Test equipment with 500 g

surface hardness display protection material test according to astm d 3363 with 1000 g

Surface hardness Display protection material Test according to ASTM D 3363 with 1000 g

test setup with 1000 g for scratch hardness test astm d 3363

Test setup with 1000 g for scratch hardness test ASTM D 3363

Testequipment

A PMMA sheet is placed on a solid horizontal surface. Strips of the display protection material to be tested are cut from the standard material (approx. 2-3 cm wide and 6-8 cm long). The pencil with a defined pencil hardness is held firmly against the film at an angle of 45° (tip away from the operator) and pushed away from the operator in a stroke of at least 6.5 mm. in order to be able to carry out and repeat this scratch hardness test in exactly the same way without the influence of the tester, we at Neoxum use a sled apparatus (ASTM D3363 test equipment).

Carriage for holding the pencils for ASTM D 3363 and ISO 15184 testing

Carriage for holding the pencils for ASTM D 3363 and ISO 15184 testing

In contrast to the original ASTM regulation, at Neoxum we start with pencil hardness 1H and if the display protection material is not scratched, the test is continued with the post-hardened pencil. The following pencil hardnesses are used at Neoxum: 1H, 2H, 4H, 4H, 5H, 8H and 9H. If no scratches appear on the surface of the film or hybrid glass during the pencil hardness test, the material has at least this degree of surface hardness. The result is validated by a second test. The test is then continued with the next hardest pencil and checked again to see whether the harder pencil scratches the material. If this is not the case again, the material has at least this degree of hardness. If the material is scratched, the display protection material offers the previous pencil hardness.

scratch hardness test astm 3363 iso 15184 howto

Scratch hardness test ASTM 3363 iso 15184 howto

setup for testing the surface hardness of screen protectors and hybrid glass

Setup for testing the surface hardness of the display protection film and hybrid glass - in this case with 1000 g (normally tested with 500 g)

weight with 250 g ft astm d 3363 and iso 15184 with 1000 g scratch proof tests

Weight with 250 g. For internal tests, the pencil hardness test is carried out with 2x 250 g + 500 g = 1000 g in addition.

test surface hardness of hybrid glass according to astm d3363

Test surface hardness of hybrid glass according to ASTM D3363

Results

Our PET-based display film material achieves a hardness of at least 3H. When tested with a 4H pencil, only minimal, non-visible scratches are missed with a fresh, sharp pencil. The second post-test is consistently OK, so that a 4H surface hardness is also valid. We therefore describe the surface hardness of our display film material as 3H to 4H.

 

Comparison of the surface hardness of screen protectors and hybrid glass

Screen protection films

Neoxum display protection films in industrial quality are made of PET (polyethylene terephthalate). The same resistant material that beverage bottles are made of. The extremely robust material in matt anti-reflective for anti-reflective display films offers a certain degree of protection against scratches and impacts, but is generally softer than glass. The scratch resistance of Neoxum screen protectors is 3H to 4H.

 

OnScreen® Hybridglass

Hybrid glass is a mixture of plastic and glass that combines the flexibility of plastic with the hardness of glass. Neoxum OnScreen® Hybrid glass offers superior scratch resistance compared to conventional films and has a scratch hardness of 9H, similar to tempered glass. The clear version of hybrid glass, for example, is very suitable for optical applications that require extremely high scratch resistance.

 

Conclusion

The ASTM D 3363 test method provides a standardized and reliable method for measuring the surface hardness of coatings and materials such as screen protectors and hybrid glass. These tests allow consumers to make better informed decisions about the protection of their devices. Hardness is assessed by determining the hardest pencil that leaves no visible marks. This provides information about the material's resistance to mechanical influences. It should always be noted that comparisons can only be made if pencils from the same manufacturer are used and are measured with an identical weight load, e.g. 500 g.
Harder materials, such as Neoxum OnScreen® hybrid glass, offer even better protection and are even more resistant to scratches compared to screen protectors, which already provide excellent protection against scratches and damage.
en_USEnglish
de_DEGerman en_USEnglish