Polycarbonate properties

Polycarbonate Properties General-Purpose and Application-Specific Grades... 

Informative and valuable sections of the chapter are Reengineering the Molecule and the previous sections to which this section refers, Commercial Production of Polycarbonate, Polycarbonate Properties General-Purpose and Apphcation-Specific Grades, Applications using Polycarbonates and Processing Polycarbonate. ... 

Polycarbonate properties that contribute to automotive applications include resistance to brittle fracture, clarity and optical precision, dimensional stabihty, impact strength, scratch resistance, and temperature resistance. 

Properties Poly(aryl ether), unfilled Polycarbonate Thermoplastic polyester ... 

Thermal Properties. ABS is also used as a base polymer in high performance alloys. Most common are ABS—polycarbonate alloys which extend the property balance achievable with ABS to offer even higher impact strength and heat resistance (2). 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Polyesters. Polyesters containing carbonate groups have been prepared from this diol (see Polycarbonates) (99). Films of this polymer, formed from an acetone or ethyl acetate solution, exhibit exceUent adhesive properties. 

The first HFIP-based polycarbonate was synthesi2ed from bisphenol AF with a nonfluorkiated aromatic diol (bisphenol A) and phosgene (121,122). Incorporation of about 2—6% of bisphenol AF and bisphenol A polycarbonate improved the dimensional stabkity and heat-distortion properties over bisphenol A homopolycarbonate. Later developments in this area concern the flame-retardant properties of these polymers (123,124). 

Fig. 23. Correlation between properties (general characteristics), melt flow index (MFI), and mol wt for standard BPA polycarbonate and CD-modified...

Table 7. Properties of TMC-Polycarbonate and its Copolymers with BPA-Polycarbonate ...

Table 10. Comparison of Characteristic Properties of CD-Modified BPA-Polycarbonate with UV-Curing Duromer...

Of practical interest are detailed studies to influence the magnetooptical properties of RE-TM materials by the substrate material and the substrate adhesion of RE-TM layers by the selected deposition technique (226). Accordingly, measurements have been performed on glass, BPA-polycarbonate, and poly(ethylene terephthalate) (as a flexible substrate). 

Polycarbonates are an unusual and extremely useful class of polymers. The vast majority of polycarbonates are based on bisphenol A [80-05-7] (BPA) and sold under the trade names Lexan (GE), Makrolon (Bayer), CaUbre (Dow), and Panlite (Idemitsu). BPA polycarbonates [25037-45-0] having glass-transition temperatures in the range of 145—155°C, are widely regarded for optical clarity and exceptional impact resistance and ductiUty at room temperature and below. Other properties, such as modulus, dielectric strength, or tensile strength are comparable to other amorphous thermoplastics at similar temperatures below their respective glass-transition temperatures, T. Whereas below their Ts most amorphous polymers are stiff and britde, polycarbonates retain their ductiUty. 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

Structure and Crystallinity. The mechanical—optical properties of polycarbonates are those common to amorphous polymers. The polymer may be crystallized to some degree by prolonged heating at elevated temperature (8 d at 180°C) (16), or by immersion ia acetone (qv). Powdered amorphous powder appears to dissolve partially ia acetone, initially becoming sticky, then hardening and becoming much less soluble as it crystallizes. Enhanced crystallization of polycarbonate can also be caused by the presence of sodium phenoxide end groups (17). 

Automotive appHcations account for about 116,000 t of woddwide consumption aimuaHy, with appHcations for various components including headlamp assembHes, interior instmment panels, bumpers, etc. Many automotive appHcations use blends of polycarbonate with acrylonitrile—butadiene—styrene (ABS) or with poly(butylene terephthalate) (PBT) (see Acrylonitrile polymers). Both large and smaH appHances also account for large markets for polycarbonate. Consumption is about 54,000 t aimuaHy. Polycarbonate is attractive to use in light appHances, including houseware items and power tools, because of its heat resistance and good electrical properties, combined with superior impact resistance. 

Electrical, electronic, and technical appHcations use polycarbonates for a variety of purposes. The woddwide market is about 156,000 t aimuaHy. Because of exceHent electrical properties (dielectric strength, volume resistivity), and resistance to heat and humidity, polycarbonate is used for electrical connectors (qv), telephone network devices, oudet boxes, etc. Polycarbonate had been popular for use in computer and business machine housings, but the use of neat resin has been largely supplanted by blends of polycarbonate with ABS. OveraH, however, the total use of polycarbonate continues to increase. 

Copolymers. The copolymer of tetrabromoBPA and BPA was one of the first commercially successhil copolymers. Low levels of the brominated comonomer lead to increased flame resistance (V-0 rating by UL 94) while having htde effect on other properties. The polycarbonate of bis(4-hydtoxyphenyl)-l,l-dichlotoethylene, prepared from chloral and phenol, followed by dehydrohalogenation, was investigated as another flame-resistant polymer which retained good impact properties. 

Blends with good mechanical properties can be made from DMPPO and polymers with which DMPPO is incompatible if an appropriate additive, compatibilizing agent, or treatment is used to increase the dispersion of the two phases. Such blends include mixtures of DMPPO with nylon, polycarbonate, polyester, ABS, and poly(phenylene sulfide). 

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