Plastics Materials 7 Episode 10 pdf

Other Aliphatic Polyamides 507 HOOC . (CH,),. CH = CH-CH-CH- (CHJ,- COOH /\ CH, . (CHJ5 CH CH \/ CH, . (CHJ- CH- CH Figure 18.21 A typical example of this class of polymer may be obtained by reacting ethylenediamine and ‘dimer fatty acid’, a material of inexact structure obtained by fractionating heat-polymerised unsaturated fatty oils and esters. An idealised structure for this acid is shown in Figure 18.21. These materials are dark coloured, ranging from viscous liquids to brittle resins and with varying solubility. They have found use as hardeners-cum-flexibilisers for epoxide resins (see Chapter 26) and are of interest in the production of thixotropic paints and adhesives. Related higher molecular weight materials are tough and flexible and find use as hot melt adhesives (Versalons). As has been mentioned earlier, a number of copolymers such as nylon 66/610/6 are available. Such a copolymer has an irregular structure and thus interchain bonding and crystallisation are limited. As a consequence the copolymer is soluble in alcohols and many other common polar solvents. 18.1 1 OTHER ALIPHATIC POLYAMIDES7 Although less than a dozen aliphatic polyamide types together with a few miscellaneous copolymers have become available commercially, a very large number have been prepared and investigated. Of the many diamine-dibasic acid combinations those based on intermediates with less than four carbon atoms are unsuitable either because of the tendency to form ring structures or because the melting points are too high for melt spinning (important in fibre production). The many nylons based on amines and acids with 6-10 carbon atoms might also be of interest as fibres and plastics but are not yet attractive commercially because of the costs of synthesis. Similar remarks must also apply to nylons 8,9 and 10. Polyamides have also been produced from intermediates with lateral side groups. The effect of such groups is similar to that of N-substitution in that there is a decrease in intermolecular cohesion and reduction in the ability of the molecules to pack in a crystal lattice. In some cases the polymers are still fibre- forming but they have much lower melting points. For example the polymer from 12-aminostearic acid (Figure 18.22) is fibre-forming but has a low melting point (109OC) and a low moisture-absorbing capacity. C,H,, I NH, . CH(CH,) ,,COOH Figure 18.22 One particular type of polyamide produced from intermediates containing lateral side groups are the poly-(a-amino acids). The a-amino acids have the structure shown in Figure 18.23 (I) and give polymers of the type shown in Figure 18.23 (11). The proteins may be considered as a special class of such 508 Polyamides and Polyimides k Figure 18.23 polymers in that they are long chain molecules containing the residues of some 25-30 amino acids arranged in a highly specific way in the molecular chain. Table 18.10 gives the structure of some of the a-amino acids that are produced by breakdown of proteins. Where R # H the amino acids may incorporated in either a D- or L- configuration and so it is possible for configurational polymers to be produced. There do not, however, show the same mechanical properties as the configura- tional homopolymers, which are more regular in structure. Table 18.10 Name R Glycine Alanine Phenylalanine Cysteine Glutamine Glutamic acid Leucine Lysine Currently, a-amino acids are prepared by several routes such as by the fermentation of glucose, by enzyme action on several substances and by the hydrolysis of proteins. Many methods for synthesising the polymers are known, of which the polymerisation of N-carboxyanhydrides is of particular interest, as it yield-products of high molecular weight (Figure 18.24). These polymers, typical of polyamides with fewer than four main chain carbon atoms in the repeating unit, decompose before melting and have to be processed from solution. Several of the polymers may, however, be spun into fibres. Over thirty years ago Courtaulds produced silk-like fibres on an experimental commercial scale from poly-(L-alanine) and from poly-(a-methyl-L-glutamate). The latter material is also said to be in use as a 'synthetic leather' in Japan. The H I R-CH-CO 0 - -NH.CO.C- + CO, I I R N- CO' Figure 18.24 Aromatic Polyamides 509 Japanese have also shown interest in poly-(L-glutamic acid) for the manufacture of silk-like fibres. Other polyamides produced experimentally include polymers with active lateral groups (hydroxy, keto groups etc.), polymers with heteroatoms (sulphur and oxygen) in the polyamide-forming intermediates, polymers with tertiary amino groups in the main chain and polymers with unsaturation in the main chain. There does not, however, appear to have been any serious attempt to develop unsaturated polyamide analogues to the polyester laminating resins. 18.12 AROMATIC POLYAMIDES Until the early 1960s the aromatic and cycloaliphatic polyamides were largely laboratory curiosities. By 1980 they were still only of minor importance to the plastics industry but of rapidly expanding interest as fibre-forming materials with a particular potential as tyre cord materials. The slow development of these materials is generally ascribed to the slow amidation reactions, the inability of many of the polymers to melt without decomposition and the tendency to colour during polymerisation. The commercial importance of aromatic polyamides has, however, grown considerably in recent years. These may be classified into three groups: (1) Copolymers of high Tg but which are amorphous and thus glassy (the 'glass- (2) Crystalline polymers used as plastics. (3) Crystalline polymers primarily of interest as fibres, including some grades clear polyamides '). which may be considered as liquid crystal polymers. 18.12.1 Glass-clear Polyamides These materials are also often referred to as glass-clear nylons, which is different from the normal usage of the term nylon for fibre-forming polyamides and their immediate chemical derivatives. Three commercial types are of interest. They are copolymers of a somewhat irregular structure and are thus non-crystalline and glassy, relying on a fairly high Tg brought about by in-chain ring structures to give reasonable heat deformation resistance. It is reasonable to expect that if these polymers had been regular and crystalline their T, would have been higher than the decomposition temperature so typical of aromatic polyamides. The oldest of these materials, a poly (trimethylhexamethylene terephthal- amide) was first marketed by Dynamit Nobel in the mid-1960s (Trogamid T). It is a condensation product of trimethylhexamethylenediamine and terephthalic acid (or its dimethyl ester) (Figure 18.25). In practice a 1:l mixture of 2,2,4- and 2,4,4-trimethyldiamines is used, this being produced from acetone via iso- phorone, trimethyladipic acid and trimethyladiponitrile. The irregular structure of the polymer indicates that it will be amorphous and glass-like. The presence of the p-phenylene group in the main chain and the lone methyl group leads to a high Tg of about 150°C. There is, somewhat surprisingly, a further transition in the range 220-228"C, the nature of which is not really understood. The polymer is more soluble than the crystalline aliphatic nylons. For example it will dissolve in 80/20 chlorofom/methanol mixtures. 5 10 Polyamides and Polyiniides CH, CH, I I I CH, H,N . CH, . C . CH, . CH . CH, CH,.NH, + n HOOC COOH CH, CH, I I I H N. CH, . C . CH, . CH . CH, . CH, . NHOC t CH, Figure 18.25 Compared with aliphatic nylons it also shows greater rigidity and hardness, lower water absorption, low temperature coefficient of expansion, good resistance to heat and moisture, better electrical insulation properties, particularly under hot and damp condition, and of course transparency. For transparent applications it is competitive with poly(methy1 methacrylate), polycarbonate, polysulphone and MBS. In terms of toughness it is like polycarbonate, polysulphone and MBS and much better than the acrylic materials whilst in terms of heat resistance only the polycarbonate and polysulphone are better. Its good electrical tracking resistance, together with high light and aging resistance and an appropriate chemical resistance, often leads to the aromatic polyamide being the preferred material. Typical properties are given in Table 18.11. Applications include flow meter parts, transparent housing for electrical equipment, sight glasses, X-ray apparatus windows, gear wheels, racks, counters and containers for solvents. Table 18.11 Comparison of two glass-clear polyamides Property Test method Units Grilamid TR-55 Trogamid T Density DIN 53479 g/cm3 1.06 1.12 Water absorption IS0 R62 mg 20 Refractive index DIN 53491 1.535 1.566 - 40 Tg DTA “C 155 145-153 Deflection temperature IS0 75 OC 155 130 Vicat temperature DIN 53460 “C 155 145 Coefficient of expansion VDE 030414 1r6 68-78 60 Tensile yield strength MPa 75* 85 Elongation at break % 8* 70 Tensile modulus MPa 2300* 3000 Ball indentation hardness VDE 0302 120* 125 Notched impact DIN 50453 U/m2 5* 10-15 Moulding shrinkage cdcm 0.005 0.007 *The mechanical propertier for Trogamid T are for dry material at 20°C those for Grilamid TR-55 at standard atmosphere at 23°C. This will account, in part, for the differences in the figures for mechanical properties of the two polymers. - DIN 53472 mg (1.82MPa) Volume resistivity DIN 50482 Cl cm 10’3 >io14 Aromatic Polyamides 5 11 Another glass-clear polyamide was announced in the mid-1970s by Hoechst; a polynorbornamide, it was marketed as Hostamid. The basic patent suggests that this material is a copolyamide of a mixture of isomeric bisamino- methylnorbornanes (Figure 18.26 (I) and (11)) with aliphatic or cycloaliphatic dicarboxylic acids with 2-20 carbon atoms or aromatic dicarboxylic acids with 7-20 carbon atoms as well as diamines, amino acids of lactams. The properties of this polymer are similar in many respects to those of Trogamid T, with a Tg of about 150"C, a specific gravity of 1.17 and an apparently somewhat higher tensile strength of 91-95 MPa. It is also glass clear. The material, Hostamid, LP700, is said to be a melt polycondensate of the diamines (I) and (11) above with terephthalic acid and up to 70% of ecaprolactam but has never been commercially marketed. A third transparent amorphous polyamide is Grilamid TR55 (Emser Werke). This is also a copolymer, in this case involving both lactam ring opening and the use of a 'nylon-type' salt. It is synthesised by reacting laurinlactam (111) with the salt of isophthalic acid (11) and the diamine, bis-(4-amino-3-methylcyclohexyl)- methane (V) (Figure 18.27). Its Tg of about 160°C is about 10°C above the other commercial glassy polyamides and furthermore it has the lowest specific gravity (1.06). Grilamid TR is also marketed by Mitsubishi and by Union Carbide (as Amidel). Of the transparent polyamides the Grilamid material has the lowest density and lowest water absorption. It is also claimed to have the best resistance to hydrolysis, whilst transparency is unaffected by long-term exposure to boiling water. The properties of Trogamid T and Grilamid TR55 are compared in Table 18.11. The transparent polyamides have increased significantly in importance in recent years. For transparent applications they are competitive with poly(methy1 methacrylate), polycarbonates, polysulphones and MBS. In terms of toughness they are like polycarbonates, polysulphones and MBS and much better than the 5 12 Polyamides and PoEyimides acrylics. In terms of heat resistance only the polycarbonates and polysulphones are superior. The materials have good tracking resistance and are resistant to a wide range of solvents and chemicals. Some stress cracking may occur on constant exposure to certain liquids, although it is claimed that many of these materials are significantly better than alternative materials in this respect. Grilamid TR55 meets a number of requirements for use in contact with foodstuffs. Uses for glass-clear polyamides include flow meter parts, filter bowls (air, oil and water), pump casings, sanitary fittings, sight glasses, X-ray apparatus windows, gear wheels, milking machine covers and water gauges for kettle jugs. Modified grades with improved resistance to alcoholic cleaning agents are used for the manufacture of spectacle frames. In addition several other materials have been reported by industrial companies, but have not at the time of writing been commercialised. These include the product of condensation of 2,2-bis-(p-aminocyclohexyl)propane (VI) (Figure 18.28) with a mixture of adipic and azelaic acid (Phillips Petroleum), a research material produced in the old German Democratic Republic obtained by melt condensation of trans-cyclohexane-l,4-dicarboxylic acid (VII) (Figure 18.28) and the two trimethylhexamethylenediamine isomers used in the manufacture of Trogamid T, and another amorphous material (Rilsan N by Ato Chimie). A polyether-amide with a heat distortion temperature of 198°C has been prepared by Hitachi by interfacial polycondensation of 2,2-bis-[4-(4-aminophen- oxy)phenyl]propane (VIII) with a mixture of isophthaloyl- and terephthaloyl- chloride (IX and X) (Figure 18.29). I COCI The polymer is reported to have a heat deflection temperature of 198"C, and a tensile yield strength of 93.2MPa, and to be flame retardant. Another polyetheramide has been produced by another Japanese company, Teijin, under the designation HM-50. The polymer is obtained by condensing Aromatic Polyamides 5 13 terephthalic acid chloride with a mixture of p-phenylene diamine and 3,4'- diaminodiphenylether in polar solvents. The main interest in this polymer, which melts at 515"C, is as a fibre to compete with poly-p-phenylene terephthalamide. 18.12.2 Crystalline Aromatic Polyamides 18.12.2.1 Poly-m-xylylene adipamide A rare example of a crystallisable aromatic polyamide used as a plastics material is poly-m-xylylene adipamide. The polymer is produced by condensation of m-xylylene diamine with adipic acid (Figure 18.30). The polymer was introduced by Mitsubishi as MXD-6 and is also now marketed by Solvay and by Laporte as Ixef. The polymer has a Tg variously reported in the range 85-1OO0C, and a crystalline melting point T, in the range 235-240°C. This is a somewhat lower figure than might be expected in view of the structure and from the glass transition value, with the ratio Tg/Tm having a surprisingly high value of about 0.73 instead of the more usual value of about 0.66. HZN-CHI CH,-NH, + HOOC-(CH,), -COOH - -NH-CH, CH,-NH-OC- (CH,),CO - Figure 18.30 As with the aliphatic polyamides, the heat deflection temperature (under 1.82 MPa load) of about 96°C is similar to the figure for the Tg. As a result there is little demand for unfilled polymer, and commercial polymers are normally filled. The inclusion of 30-50% glass fibre brings the heat deflection temperature under load into the range 217-23loC, which is very close to the crystalline melting point. This is in accord with the common observation that with many crystalline polymers the deflection temperature (1.82 MF'a load) of unfilled material is close to the Tg and that of glass-filled material is close to the T,. Commercial grades of polymer may contain, in addition to glass fibre, fire retardants, impact modifiers and particulate reinforcing fillers. Carbon fibre may be used as an alternative to glass fibre. The glass-filled grades have a high tensile strength (approx. 185MPa) and flexural modulus (approx. 10 000 MPa). These two properties, together with their low moulding shrinkage (0.003-0.006 cm/cm) and good surface finish, are emphasised when making comparisons with the aliphatic nylons. In the absence of fire retardants the material has a limiting oxygen index of 27.5 and may burn slowly. Only some grades will achieve a UL 94 V-1 rating. The Underwriters' Laboratories continuous use temperature index is also somewhat low and similar to the polyarylates with ratings of 135-140°C (electrical) and 105°C (mechanical with impact). Initial marketing has emphas- ised comparisons with the aliphatic nylons for the reasons given in the previous 5 14 Polyamides and Polyimides paragraph. They have also been favourably compared with poly(buty1ene terephthalate) in respect of chemical resistance, and poly(pheny1ene sulphides) because of the lower cost of the polyamide. Because of their rigidity they are being looked at particularly as replacements for metals such as die-cast zinc alloys. Early uses to become established include portable stereo cassette recorders. Other applications include mowing machine components, electrical plugs, sockets, TV tuner blocks, pulleys, shafts and gears. 18.12.2.2 Aromatic polyamide fibres. In recent years there has been considerable interest in aromatic polyamide fibres, better known as aramid fibres. These are defined by the US Federal Trade Commission as 'a manufactured fibre in which the fibre-forming substance is a long chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings.' The first significant material of this type was introduced in the 1960s by Du Pont as HT-1, later re-named Nomex; a poly-(m-phenyleneisophthalamide), it is prepared by condensation of 1,3-phenylenediamine with isophthalic acid (Figure 18.31 ). It may be spun from solution in dimethylformamide containing lithium chloride. It possesses fibre mechanical properties similar to those of nylons 6 and 66 but these are coupled with some very good high-temperature properties. It is claimed to retain half of its room temperature strength at 260°C, resist ignition and be free of after-glow. One disadvantage is that it undergoes pronounced shrinkage when exposed to flame. Although this is acceptable in very loose fitting protective clothing it is not suitable for tailored clothing such as military uniforms. @yrnH ~H,N @NH~ + ~HOOC Figure 18.31 In 1973 Du Pont commenced production of another aromatic polyamide fibre, a poly-(p-phenyleneterephthalamide) marketed as Kevlar. It is produced by the fourth method of polyamide production listed in the introductory section of this chapter, namely the reaction of a diamine with a diacid chloride. Specifically, p-phenylenediamine is treated with terephthalyl chloride in a mixture of hexamethylphosphoramide and N-methylpyrrolidone (2: 1) at -10°C (Figure 18.32). H,N -@ NH, + CIOC~ COCI+-HN * NHOC* CO - Figure 18.32 Aromatic Polyamides 5 15 The Kevlar polymer may be regarded as a liquid crystal polymer (see Chapter 25) and the fibres have exceptional strength. They are thus competitive with glass, steel and carbon fibres. Compared with glass fibres, early grades were similar in strength but had twice the stiffness and half the density. The fibres are strong in tension but somewhat weak in compression. Composites have excellent creep resistance and better fatigue resistance than glass-fibre composites. Since their initial availability the tensile strengths achieved with Kevlar polymers have increased from 2.75 to 3.8 GPa, with Kevlar HT, announced in 1987, claimed to be 20% stronger than earlier grades. Announced at the same time was Kevlar HM, claimed to be 40% stiffer than earlier grades. Originally developed for tyre cords, Kevlar-type materials have also become widely used in composites. Uses include filament-wound rocket motors and pressure vessels, metal-lined Kevlar-overwrapped vessels in the space shuttle, boat and kayak hulls, Kevlar-epoxy helmets for the US military, and as one of the reinforcements in composite lorry cabs. Rather similar materials have been made available by Monsanto, made by reacting p-aminobenzhydrazide with terephthaloyl chloride (Figure 18.33). The fibre is marked as PABH-T X-500. H*N*coNHN"* + CIOC -@ COCI - -2HCI -HN-@)CONHN"OC 0 0 co- Figure 18.33 Yet another heat- and flame-resistant fibre is the Bayer product AFT-2000. This is classed as a polyquinazolinedione and contains the structural element in Figure 18.34. Figure 18.34 Polymers have also been prepared from cyclic amines such as piperazine and bis-(p-aminocyclohexy1)methane. An early copolymer, lgamid IC, was based on the latter amine. This amine is also condensed with decanedioic acid, HOOC (CH2)&OOH, to produce to silk-like fibre Quiana (Du Pont). In addition to the commercial aromatic polyamides described above many others have been prepared but these have not achieved commercial viability. There are, however, a number of other commercial polymers that contain amide groups such as the polyamide-imides. The latter materials are discussed in Section 18.14. 5 16 Polyamides and Polyimides 18.12.2.3 Polyphthalamide plastics As with the aliphatic polyamides such as nylons 6 and 66, the polyphthalamides were developed as plastics materials only after their sucessful use in the field of fibres. Such materials were introduced in 1991 by Amoco under the trade name of Amodel. As might be expected of a crystalline aromatic polar polymer, the material has a high T, of 310°C and a high Tg of 127"C, the ratio of the two having a value close to the 2/3 commonly found with crystalline polymers (see Section 4.4). Also, as to be expected, the material exhibits high strength and rigidity and good chemical resistance, particularly to hydrocarbons. A typical glass-reinforced grade has a continuous use temperature of 18O"C, similar to that of polysulphone and only exceeded by a small number of polymers (see Table 9.1). Commercial polymers are generally modified by glass- or mineral-fibre reinforcement. Standard grades have a UL94 Flammability Rating of HB but the use of flame retardants allows grades to be produced with a V-0 rating at 0.8 mm thickness. Also of note are such good electrical properties as a high Comparative Tracking Index of 550 V and an ASTM D495 Arc resistance of about 140 s. The manufacturers stress ease of processing as a particular feature of the material. Recommended melt temperatures are in the range 320-340°C and mould temperatures are 135-165°C. Mould shrinkage of glass-filled grades is usually of the order of 0.2-0.4% in the flow direction and up to twice this value in the transverse direction. The materials are notable for their ability to withstand vapour phase and infrared soldering processes. 18.13 POLYIMIDES~~J~ The polyimides have the characteristic functional group below and are thus closely related to the polyamides. However, the branched nature of the ,cow 'cow wN functional group facilitates the production of polymers with a backbone that consists predominantly of ring structures and hence high softening points. Furthermore, many of the structures exhibit a high level of thermal stability so that the polymers have become of some importance in applications involving service at higher temperatures than had been hitherto achieved with plastics materials. The first commercial materials were introduced by Du Pont in the early 1960s when they marketed a range of products obtained by condensing pyromellitic dianhydride with aromatic amines, particularly di-(4-aminophenyl) ether. These included a coating resin (Pyre ML) film (originally H-film, later named Kapton) and in machinable block form (Vespel). In spite of their high price these materials have found established uses because of their good performance at high temperature. Unfortunately, by their very nature, these polymers cannot be moulded by conventional thermoplastics techniques and this led in the early 1970s to the availability of modified polyimides such as the polyamide imides typified by Torlon (Amoco Chemicals), the polyester imides (e.g. Icdal Ti40 by Dynamit Nobel) and the polybismaleinimides such as Kine1 (Rhone-Poulenc). [...]... 90 63 93 970 0 6030 150°C 67 42 5000 3890 315°C 35 27 2.5 D.638 6-8 5 Elongation at break D .79 0 Flexural modulus 23°C 7 10 000 450 000 6 27 000 26 800 450 000 26O-30O0C 4300 4900 3100 Deflection temperature under 282 3 57 D.648 load (heat distortion temperature) Water absorption (24 h) 0.28 0.32 0.2 0.35 Coefficient of friction 73 -75 H 104 (E-scale) 83-89H Rockwell hardness D .78 5 5 x IO'S 406 3 x 101 4 Volume... Table 1 93 ASTM Value test method Dielectric strength (short time) D.149 Volume resistivity D.2 57 Surface resistivity Dielectric constant (73 °F) Power factor (0.125 in thick) 1 97 kV/cm (0. 010 in thick) 670 kV/cm 6 X 1OI6 C m (0.2% water) L 4.6 X C m (0.9% water) L low 3 .7( 10 - 1O4 Hz) 0.004 (102 -104 ~z) D.2 57 D 150 D.150 cause staining Acetal copolymer resins are somewhat more resistant to hot alkalis... These materials do have sufficient regularity to be crystallisable and are of interest as biodegradable plastics and are discussed further in Chapter 31 References 1 Plastics, 17, 64 (1952) 2 FREIDLNA, R K and KARAPETYAN, s A , , Telomerization and New Synthetic Materials, Pergamon, Oxford (1961) 3 KRALICEK, J., SEBENDA, J., ZADAK, z and WICHTERLE, o., Chem Prumsyl., 11, 377 (1961); NEUHAUSL, E R , Plastics. .. IJnnotched Dielectric strength $ (v/mil) Dielectric constant at 1 kHz SO% RH Dissipation factor at 1 kHz SO% RH Volume resistivity (ohm cm) (inreinforced 1. 27 10s 3000 7- 8 60 145 1 25 71 0 3.15 0.0013 6 .7 X 10 30% Glass-fibre reinforced 165 9000 - 3 230 2 8 630 3 .7 0.0015 3.0 X loL6 The markets for polyetherimides arise to an extent from stricter regulations concerning flammability and smoke evolution coupled... carbon fibre polyimide laminate Property Specific gravity Flexural strength (R.T.) After 100 h at 200°C tested at R.T After 1550h at 220°C tested at 200°C After 177 0h at 300°C tested at 300°C Flexural modulus (R.T.) Interlaminar shear strength (R.T.) Units 1. 67 120 000 70 3 120000 70 3 1ooooo 690 50 OOO 345 22 x 106 151600 6400 44 Ibf/ in MPa Ibf/in2 MPa Ibf/in2 MPa Ibf/in2 MPa Ibf/in2 MPa Ibf/in2 MPa... Technology, Vol 1Or3 47- 615 Wiley-Interscience, New York (1965) ADROVA, N A BESSONOV, M I., LAIUS, L A Reviews and PRIEBE, E., Kunstoffe, 77 , 988-93 (19 87) Chapter 9B of Thermoplastic Elastomers (Eds LEGGE, E.), Hanser, Munich (19 87) BLINNE, G DELEENS, D H N R., HOLDEN, G ~ ~ ~ S C H R O E D E R , 530 Polyumides and Polyimides Chapters 8, 9 and 10 of New Commercial Polymers 1969-1 975 , Gordon and Breach,... break % Stress to 25% ext (MPa) Youngs modulus (MPa) 6333 1.01 63 5533 1.01 55 4033 1.01 40 3533 1.01 35 2533 1.01 25 4011 1 .10 40 0.5 1.2 173 90 51 380 17. 6 260 0.5 1.2 168 66 44 455 11.9 145 0.5 1.2 168 52 36 485 6.5 50 0.5 1.2 152 46 34 71 0 2.35 14.6 0.5 1.2 148 42 29 71 5 1.85 10. 4 4.5 120 195 - - 528 Polyamides and Polyimides to have withstood 36 X lo6 cycles in a de Mattia flexing test Softer grades... and creep resistance (see Table 18.13) After 100 h at 23°C and a tensile load of 70 MPa the creep modulus drops only from 4200 to 3000 MPa whilst at a tensile load of 105 MPa the corresponding figures are 3500 and 2500 MPa respectively If the test temperature is raised to 150°C the creep modulus for a tensile load of 70 MPa drops from 2400 to 170 0MPa in 100 h Three months immersion in water leads to... (23°C) D .79 2 D.638 Flexural modulus (23°C) Eb(23"C) Deflection temperature 264 Ibf/in2 (13 2 MPa) 66 lbf/in2 (0.48 MPa) Vicat softening point Impact strength (23°C) Crystalline melting point Water immersion (24 h immersion) (50% RH equilibrium) (continuous immersion-equilibrium) Coefficient of friction D .79 0 D.638 D.648 D.569 D.256 - D. 570 - - Acetal homopolymer Acetal copolymer 1.425 100 00 70 4100 00... (continuous immersion-equilibrium) Coefficient of friction D .79 0 D.638 D.648 D.569 D.256 - D. 570 - - Acetal homopolymer Acetal copolymer 1.425 100 00 70 4100 00 2800 15 -75 1. 410 8500 58 360 000 2500 23-35 100 170 185 1.4-2.3 175 0.4 0.2 0.9 0.1-0.3 110 158 162 1.1 163 0.22 0.16 0.8 0.2 Unit lbf/in2 MPa lbf/in2 MPa % "C "C "C ft Ibf in-' notch O C Acetal Resins 539 Although in many respects acetal resins are . 27 5 6 27 000 4300 - - - - 73 -75 H 406 - - -~ Torlon 2000, unfilled 1.41 13 500 93 - - - - 2.5 7 10 000 450 000 4900 282 0.28 0.2 104 (E-scale) 3 x 101 4 3 .7. SO% RH Volume resistivity (ohm. cm) 1. 27 10s 3000 60 145 7- 8 1 25 71 0 3.15 0.0013 6 .7 X 10 165 9000 3 230 - 2 8 630 3 .7 0.0015 3.0 X loL6 The markets for pol. ASTM test __ D.638 D.638 D .79 0 D.648 D .78 5 D.2 57 D.150 D.495 - Vespel, unfilled 1.42 13 000 90 970 0 67 5000 35 6-8 450 000 26 800 3100 3 57 0.32 0.35 83-89H 5 x IO'S