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Why replace glass with plastics?


Frequently Asked Questions

Transparent plastics such as polycarbonate and acrylic have many advantageous properties. They are tough, lightweight, easily moulded and formed into complex shapes, are highly transparent and available at relatively low cost. These materials are widely used, substituted for glass, across many industries, including:

  • Aerospace
  • Automotive
  • Consumer/healthcare goods
  • Construction

The primary application area for these plastics is as optical windows, where the material behaves in either an active sense (such as spectacle lenses where the refractive index of the material is of primary importance) or passively, such as headlamp covers. The scale of use of these materials can be put into perspective by considering that transparent plastic items are a multi-billion dollar market.

The materials are used because of their transparency, but also because they have other significant advantages over glass, their main competitor for transparent products. These advantages include lower density, typically 1.2 gcm-3 compared to 2.2 gcm-3, higher toughness and lower processing temperatures. The drive to replace glass with these plastics is based on these properties.

Spectacle lenses are a good example of the transition from traditional to newer materials, where the higher toughness of the plastic materials is of considerable benefit from a health and safety perspective. Another area where this change is happening is the automotive industry. The potential weight saving from using polycarbonate instead of glass is considerable, leading to higher fuel efficiencies and considerable economic and environmental benefits.

The properties of the polymer materials also lend them to more radical design. This has been seen with the advent of bolder headlamps on many recent vehicles, and it has been estimated that over 80% of all automotive vehicles manufactured in the US now have plastic headlamp lenses.

One major limitation of these materials however, is their inherent softness and vulnerability to abrasion and scratch damage. The protection of these materials against abrasion is essential if they are to be more widely utilised in demanding environments. Protection is mainly via coatings deposited onto the formed plastic component.

Further information

FAQ: Why do plastics need hardcoats?

FAQ: What protective hardcoats are available for plastics?

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