【文章內(nèi)容簡介】 4] 鄒國明主編李光副主編高分子材料加工工藝學(xué)北京中國紡織出版社 1982 [15] 羅河勝主編塑料材料手冊廣州廣東科技出版社 20213 [16] 吳智華楊其高分子材料成型工藝學(xué)成都四川大學(xué)出版社 20219 [17] 機械工業(yè)部橡膠塑料機械產(chǎn)品樣本北京機械工業(yè)出版社 1996 外文資料翻譯 Polycarbonate Polycarbonates known by the trademarked names Lexan Makrolon Makroclear and others are a particular group of thermoplastic polymers They are easily worked moulded and thermoformed Because of these properties polycarbonates find many applications Polycarbonates do not have a unique plastic identification code and are identified as Other Structure Polycarbonates received their name because they are polymers containing carbonate groups O C O O Most polycarbonates of mercial interest are derived from rigid monomers A balance of useful features including temperature resistance impact resistance and optical properties position polycarbonates between modity plastics and engineering plastics Production The main polycarbonate material is produced by the reaction of bisphenol A and phosgene COCl2 The overall reaction can be written as follows The first step of the synthesis involves treatment of bisphenol A with sodium hydroxide which deprotonates the hydroxyl groups of the bisphenol A HOC6H4 2CMe2 2 NaOH → NaOC6H4 2CMe2 2 H2O The diphenoxide NaOC6H4 2CMe2 reacts with phosgene to give a chloroformate which subsequently is attacked by another phenoxide The reaction from the diphenoxide is NaOC6H4 2CMe2 COCl2 → 1n [OC OC6H4 2CMe2]n 2 NaCl In this way approximately one billion kilograms of polycarbonate is produced annually Many other diols have been tested in place of bisphenol A eg 11bis 4hydroxyphenyl cyclohexane and dihydroxybenzophenone including some eg tetramethylcyclobutanediol that are unlikely endocrine disruptors An alternative route to polycarbonates entails transesterification from BPA and diphenyl carbonate HOC6H4 2CMe2 C6H5O 2CO → 1n [OC OC6H4 2CMe2]n 2 C6H5OH The diphenyl carbonate was derived in part from carbon monoxide this route being greener than the phosgene method Properties and processing Polycarbonate is a very durable material Although it has high impactresistance it has low scratchresistance and so a hard coating is applied to polycarbonate eyewear lenses and polycarbonate exterior automotive ponents The characteristics of polycarbonate are quite like those of polymethyl methacrylate PMMA acrylic but polycarbonate is stronger usable in a wider temperature range but more expensive This polymer is highly transparent to visible light and has better light transmission characteristics than many kinds of glass Polycarbonate has a glass transition temperature of about 150 176。C 302 176。F so it softens gradually above this point and flows above about 300 176。C 572 176。F Tools must be held at high temperatures generally above 80 176。C 176 176。F to make strain and stressfree products Low molecular mass grades are easier to mould than higher grades but their strength is lower as a result The toughest grades have the highest molecular mass but are much more difficult to process Unlike most thermoplastics polycarbonate can undergo large plastic deformations without cracking or breaking As a result it can be processed and formed at room temperature using sheet metal techniques such as forming bends on a brake Even for sharp angle bends with a tight radius no heating is generally necessary This makes it valuable in prototyping applications where transparent or electrically nonconductive parts are needed which cannot be made from sheet metal Note that PMMAPlexiglas which is similar in appearance to polycarbonate is brittle and cannot be bent at room temperature Main transformation techniques for polycarbonate resins extrusion into tubes rods and other profiles extrusion with cylinders into sheets 05– 15 mm 0020– 059 in and films below 1 mm 0039 in which can be used directly or manufactured into other shapes using thermoforming or secondary fabrication techniques such as bending drilling routing laser cutting etc injection molding into ready articles Applications Polycarbonate is a versatile tough plastic used for a variety of applications from bulletproof windows to pact disks CDs The main advantage of polycarbonate over other types of plastic is unbeatable strength bined with light weight While acrylic is 17 stronger than glass polycarbonate is nearly unbreakable Bulletproof windows and enclosures as seen inside banks or at drivethroughs are often made of polycarbonate Add to this the advantage that polycarbonate is just onethird the weight of acrylic or onesixth as heavy as glass and the only drawback is that it is more expensive than either acrylic or glass Compact disks and digital versatile discs DVDs are perhaps the most readily recognized examples of polycarbonate If youve ever archived files on a writable CD then later tried to break it before throwing it away you know just how tough polycarbonate can be Clear polycarbonate is used to make eyeglasses because of its excellent transparency durability and high refractive index This means that it bends light to a far greater degree than g