以前頭燈都是玻璃製造.....可以造型透明度硬度也不錯..尤其是耐熱性特優...

不過蠻重...所以汽車頭燈現多為塑膠材質..............

就是因為輕....

頭燈塑膠除了要透明之外...還要求耐衝擊硬度...還有耐高熱..

一般是用PC(聚碳酸酯Polycarbonate)材質...具有彈性...PMMA打到石頭比較會裂......

Polymethyl methacrylate(PMMA)聚甲基丙烯酸甲酯也是一種頭燈材質...聽說抗UV比上面那個強(SAE J576測試)...所以如果使用在投射式(Reflex Reflectors)最好...

也有一說用PP聚丙烯(Polypropylene)?........

既然是塑膠..那當然耐磨性就不如玻璃..所以汽車後市場也有研磨拋光劑....以使發黃的燈殼回春...

http://calcoast-itl.com/assets/Plastic%20Material%20In%20Automotive%20Lenses.pdf

PLASTIC MATERIAL IN AUTO LENSES. There are two types of plastic used in lamps: Polycarbonate (PC) and Polymethyl ... PC is used in headlamp lenses because it will not crack as easily as PMMA when hit by a stone while driving.

http://zh.wikipedia.org/wiki/%E8%81%9A%E7%A2%B3%E9%85%B8%E9%85%AF

聚碳酸酯（Polycarbonate，簡稱PC）是一種無色透明的無定性熱塑性材料。其名稱來源於其內部的 $C O 3$ 基團。

密度：1.20－1.22 g/cm³ 線膨脹率：3.8×10^-5 cm/cm°C 熱變形溫度：135 °C

聚碳酸酯是日常常見的一種材料。由於其無色透明和優異的抗衝擊性，日常常見的應用有CD/VCD光碟，桶裝水瓶，嬰兒奶瓶，防彈玻璃，樹脂鏡片、銀行防子彈之玻璃、車頭燈罩、動物籠子、登月太空人的頭盔面罩等等。

High-Impact Polymer Material

Composilite

Polymer material based on high-impact polyphenylene ether mixture.

The invention relates to a polymer material based on a high-impact polyphenylene ether mixture which comprises aluminium-methyl-methyl phosphonate as a flame retardant and also a fatty acid having 12-20 carbon atoms or a salt thereof with a metal from the group IIA or IIB of the Periodic Table of the Elements or a compound of the formula RO-(C2H4O)nCH2COOM, wherein R is a hydrocarbon radical having 12-18 carbon atoms, n is an integer having an average value of 1-10 and M is a metal from the group II of the Periodic Table of the Elements, in a quantity from 1 to 10% by weight related to the polymer mixture.

Transparent - Tough and Heat Resistant polymer

Polycarbonate is a transparent amorphous polymerwhich exhibits outstanding physical properties such as outstanding impact resistance(almost unbreakable), heat resistance up to 125°C and excellent clarity, although opaque and translucent grades are also available. Polycarbonate is often used to replace glass or metal in demanding applications when the temperature does not exceed 125°C

汽車工業之運用....
拜耳AG2677.....

Automotive Lighting and Glazing

The automotive industry requires materials that allow lightweight construction and are absolutely reliable in continuous service. Materials should also offer a high potential for integrating different functions in order to permit all-in components or systems to be produced. Freedom of design is also of major importance.

Thanks to high impact strength and good heat resistance combined with good durability suitable for outdoor conditions, Makrolon^® is intensively used as glass replacement in applications such as headlamps or glazing with excellent transparency required.