Transparent Windows
"Taber Test" is industry standard for abrasion resistance of transparent materials
Situation:
As material advancements continue, the automotive industry is incorporating lighter weight materials into car designs for weight savings. Exatec LLC was founded in 1998 with the mandate to develop polycarbonate glazing solutions for the automotive and transportation industries.
Analysis:
Transparent materials, when used as windows or enclosures, are subjected to wiping and cleaning. Thus, it is useful to know how resistant the material or applied coatings are to surface abrasion. The industry standard to evaluate this property is the ‘Taber test’. For transparent plastics, the standard is ASTM D1044 (Standard Test Method for Resistance of Transparent Plastics to Surface Abrasion). To ensure that glass or other window glazing materials (e.g. plasma coated plastics) meet a minimum performance standard, the automotive industry references ANSI / SAE Z26.1 (Safety Glazing Materials for Glazing Motor Vehicles and Motor Vehicle Equipment).
Using a patented polycarbonate coating system (plasma-enhanced CVD hardcoat), Exatec offers a polycarbonate product that provides “weathering, durability and glass-like abrasion performance”. To qualify Exatec’s material for use in automobiles, the company was required to satisfy stringent abrasion resistance requirements as specified by the industry. Tested on the Taber Rotary Platform Abraser (modified with 11mm vacuum pick-up orifices vs. the nominal 8mm), specimens are subjected to the rub wear action of CS-10F wheels. To accurately measure the optical properties of the transparent material, a “hazemeter” quantifies the amount of light transmitted through the specimen before and after the abrasion test. Recorded as initial haze and final haze, the difference is calculated to determine the “delta haze” and represents the light scatter that results from abrasion.
Benefit:
In October 2005, the United States Department of Transportation’s National Highway Traffic Safety Administration, responding to an official request by Exatec, confirmed the Exatec E900 Polycarbonate Glazing System can be used in automotive glazing applications if the prescribed test requirements are met. Automotive companies intrigued by the styling freedom this light weight alternative to glass offers, have already incorporated polycarbonate in side and rear window applications as well as panoramic roofs. Exatec E900 is the only transparent polycarbonate glazing system that can meet the Taber abrasion resistance requirements for driver visibility applications.
Transparent materials are used in numerous places where it is important that the surface does not wear or mar. Examples include visors; appliance panels; windows; bus shelters; machine guards; automotive bezels; headlamps; motorcycle windshields; etc. Using the Taber test reassures the design engineer that the materials being considered have the necessary abrasion resistance properties.
