Plastics Materials 7 Episode 11 doc

General Properties 561 is very restricted because of the high processing temperatures involved. It has been found that benzophenone and benzotriazole ultraviolet absorbers are only effective if the polycarbonate composition is treated to become slightly acidic. Very small amounts (ca 0.005%) of stabilisers such as metaphosphoric acid, boron phosphate and phenyl neopentyl phosphite may also be used. Glass fibre is now used in special grades. Depending on the concentration and type of glass fibres, mouldings have increased hardness, flexural strength, modulus of elasticity and fatigue strength but lower moulding shrinkage and coefficient of thermal expansion. The last two properties in particular permit the production of mouldings with high dimensional accuracy and stability. As with all instances involving reinforcement with glass fibres it is necessary to treat the fibre surfaces with a finish to promote adhesion between resin and glass. In the case of polycarbonates very good results are reported with (~-3,4-epoxycyclohexylethyl) trimethoxy silane. The addition of carbon fibre to polycarbonate can lead to composites with flexural strength three times and flexural modulus seven times that of unfilled resin. Notched Izod impact values are amongst the highest for any fibre-filled thermoplastics material. Flexural creep after 2000 hours loading at 10 000 psi (68.97 MPa) is also minimal. Carbon-fibre-reinforced grades also exhibit enhanced deflection temperatures (149°C for 30% fibre loading under 1.8 MPa loading), low volume and surface resistivities, facilitating dissipation of static charge, lower coefficient of friction and increased wear resistance. Incorporation of PTFE, silicone resins and glass or carbon fibres can lead to important internally lubricated composites. One grade available from LNP containing 13% PTFE, 2% silicone and 30% glass fibre showed a 100-fold improvement in wear resistance, a 45% reduction in static coefficient of friction, and a 36-fold increase in PV value compared with an unmodified polymer. Traditionally not considered good bearing materials, such modified grades may be used effectively in demanding gear, cam and sliding applications. Flame retardant grades may not only use additives such as sodium 2,4,5-trichlorobenzene sulphonate but also an anti-dripping agent which can cause cross-linking as the polymer burns, thus reducing the tendency to drip. 20.5 GENERAL PROPERTIES Although somewhat more expensive than the general purpose thermoplastics, polycarbonates have established themselves in a number of applications. The desirable features of the polymer may be listed as follows: (1) Rigidity up to 140°C. (2) Toughness up to 140°C. (3) Transparency. (4) Very good electrical insulation characteristics. (5) Virtually self-extinguishing. (6) Physiological inertness. The principal disadvantages may be listed as: (1) More expensive than polyethylene, polystyrene and PVC. (2) Special care required in processing. [...]... CALKINS, T R., Mod fiaslics, 36, 115 (1959) Bibliography w F and FOX, D w., Polycarbonates, Reinhold, New York (1962) Polycarbonates-Recent Developmenfs (Patent Review), Noyes Data Corporation, New Jersey (1 970 ) SCHNELL, H., Chemistry and Physics of Polycarbonates, Interscience, New York (1964) CHRISTOPHER, JOHNSON, K., Reviews Kunstoffe, 11, 993 (19 87) KUnStOffe, 80, 111 3 (1990) KIRCHER, K., KUnSlOffe,... At 280°C one standard grade (Noryl 110 ) has a viscosity of 675 Ns m-2 at 100 s-l but a value of only 7 N s m-2 at 100 000 s-' The flow depends considerably on the grade but flow path ratios tend to be in the same range as for ABS materials (6) A low moulding shrinkage (0.005-0.0 07 cm/cm) in unfilled grades down to about 0.002 cm/cm in 30% glass-fibre-filled grades (7) To reduce strains in mouldings,... 11) was offered in 1965 by Union Carbide as Bakelite Polysulfone, now renamed Udel In 19 67 Minnesota Mining and Manufacturing introduced Astrel 360 (Table 21.3, V), which they referred to as a polyarylsulfone In 1 972 IC1 brought a third material onto the market which they called a polyethersulphone (111 ) and which they then marketed as Victrex They also introduced a material intermediate between I11... poly~ulphone'~ 14 Units Property I Unfilled 1.24 10 200 70 370 000 2600 400-500 1.05 Ibflin' MPa Ibffin' MPa ft Ib in-' % at 2000 Ibf in-' at 22.2"C n ' Heat distortion temperature (264 Ib i) Coefficient of linear expansion Moulding shrinkage "C 174 5.58 x 10-5 0.0 07 cm cm-'"C-' cm/cm I I 40% Glass-filled I I - I 1 , 1.54 18000 124 1500000 11 000 60-100 0.29 , 1 87 1.98 x 10-5 0.002 ~ I Polysulphones 601 Higher... SCHNELL, H., Trans Plastic Znst., 28, 143 (1960) 5 U S Patent, 2,468,982 6 U S Patent, 2,936, 272 7 SCHNELL, H., Angew Chem., 68, 633 (1956) 8 German Patent, 959,4 97 9 PRIETSCHK, A,, Kolloid-2 156, (I), 8, Dr Dietrich Steinkopff Verlag, Darmstadt (1958) 10 PEILST~CKER,G., Kunstoffe Plastics, 51, 509 (September 1961) 11 STANNETT, v T and MEYERS, A w., Unpublished, quoted in reference 12 12 CHRISTOPHER, w... Polysulphones 5 97 Table 21.3 Aromatic polysulphones - Tyre rrade name Tg (“C) I - (melts with decomposition above 500°C) -@so:- 190 Udel 11 1 230 Victrex IV 250 Polyethersulphone I1 CH, 72 0P 285 V VI Astrel 260 Radel - determine the heat distortion temperature (or deflection temperature under load, since the materials are also amorphous) It is also to be noted that all of the commercial materials mentioned... Water absorption 24 h Saturation at 23°C PPSIGF I PAS-I (60140) - 265 150 33 2 10 500 350 - 47 3.8 0.00 37 0.01 1.01 PAS-2 145 170 I1 215 190 92 - - 3400 223 21 46 >10 3200 1200 50 46 - - - - - - - - Polyphenylene Sulphides 595 plastics, the poly(pheny1ene sulphides) do not possess the toughness of amorphous materials such as the polycarbonates and the polysulphones and are indeed somewhat brittle On... 160°C The range of blends now available comprises a broad spectrum of materials superior in many respects, particularly heat deformation resistance, to the general purpose thermoplastics but at a lower price than the more heat-resistant materials such as the polycarbonates, polyphenylene sulphides and polysulphones At the present time the materials that come closest to them in properties are the ABS/ polycarbonate... and Block Copolymers 579 Table 20.9 Selected properties of PC-ABS and PC-PBT alloys PC-ABS Grade High Low ABS (20% glass) Vicat softening point (“C) Notched impact (kJ/m2) Specific gravity Water absorption (IS0 62) (%) Oxygen index (%) Tensile strength (MPa) Elongation at break(%) Flexural modulus (MPa) Ball hardness (H30 (IS0 2039) (N/mm2) Vol resistivity (ohm.cm) 111 25 1.1 0 .7 21 40 60 2000 80 10l6... require high processing temperatures One disadvantage of many of these materials, however, is their rather poor electrical tracking resistance Although the first two materials discussed in this chapter, the polyphenylenes and poly-p-xylylenes, have remained in the exotic category, most of the other materials have become important engineering materials In many cases the basic patents have recently expired, . in Modern Plastics International) Western Europe 506 000 28 .7 21.8 17. 8 8 .7 5.2 4.3 3.6 2.6 2.6 4 .7 Consumption (tonnes) USA 358 000 23.5 1.5 16.2 2.5 8.4 17. 0 4.2 1.3. resistivity (ohm.cm) 111 25 1.1 0 .7 21 40 60 2000 80 10l6 130 35 1.16 0.6 24 50 85 2200 90 1Ol6 130 125 8 46 1.2 1.22 0.6 0.35 24 <2 1 75 55 2 75 6000 2200 125. Polycarbonates, Interscience, New York (1964) Jersey (1 970 ) Reviews KIRCHER, K., Kunstoffe, 11, 993 (19 87) KIRCHER, K., KUnStOffe, 80, 111 3 (1990) KIRCHER, K., KUnSlOffe, 86(10), 1490-1