Transparent materials such as acrylic (PMMA), polycarbonate (PC) and glass play an important part in our every day life. They are commonly used in a wide range of industries including electronics, packaging, building, medical, automotive and aerospace.
According to their function, these materials are generally required to allow an undistorted and visually clear image of the content that is behind. In some applications it can be critical for safety reasons and for others, to allow excellent viewing quality of products and/or information. Indeed some applications require a combination of obscurity and full transparency for instance smart glass. For each application the correct selection of polymers and resins used to manufacture the material is essential in ensuring optimum mechanical and physical properties.
Abrasion resistance of PMMA and PC presents challenges to the manufacturer and may require modifications to be made to the polymers or the use of coatings on the surface to improve wear characteristics.
To simulate wear, a test method – the Taber Abrasion test to ASTM D1044 utilising CS-10F wheels was adopted. Taber tests involve mounting a flat to a turntable platform that rotates on a vertical axis at a fixed speed. Two abrasive wheels, applied at a specific pressure, traverse a complete circle on the specimen surface. The resulting abrasion marks form a pattern of crossed arcs in a circular band that cover an area approximately 30 cm2. At the end of the test, the change in transparent quality, mainly haze, is measured using a hazemeter.
As the orientation of a hazemeter conforming to ASTM D1003 is typically horizontal, a special mounting adaptor needs to be used to hold the sample to the measurement port. The Rhopoint ID, thanks to its high correlation to ASTM D1003 is a vertically oriented instrument making sample mounting quick and very easy allowing compatible measurements to now be made.
Example – PMMA
STEP 1: Customer supplied samples of rotary abraded (using Taber Model 1700) and non-abraded PMMA material were tested. The Abrasion Adaptor, available as an optional accessory, allowed the samples to be mounted and easily rotated over the graticule for ASTM equivalent haze (HASTM) measurement.
STEP 2: The abraded sample was mounted onto the table and a measurement taken.
STEP 3: The table was then sequentially rotated 90 degrees each time and further measurements made. This process was then repeated for the non-abraded sample for comparison.
Example – PMMA
The measurement data shows the reduction in optical quality due to Taber abrasion. The abraded sample shows a higher Haze and lower Sharpness value indicating surface roughness is present; the hardness of the material surface being insufficient over the test cycle to withstand the abrasion. Matching the material formulation to the application allows quality improvements and cost savings.
Bespoke cutter die - 1 or 2 of the same shape
