Plastics Materials 7 Episode 16 ppsx

Shellac 867 30.6 SHELLAC The importance of shellac to the plastics industry has declined rapidly since 1950. Before that time it was the principal resin employed in 78 rev/min gramophone records. The advent of the long playing microgroove record meant that mineral fillers could no longer be tolerated because any imperfections in the microgroove led to a high background noise on the record. The record industry therefore turned towards alternative materials which required no mineral filler, and vinyl chloride-vinyl acetate copolymers eventually became pre-eminent. It is, however, still used for a number of purposes outside the normal realm of plastics. 30.6.1 Occurrence and Preparation Shellac is the refined form of lac, the secretion of the lac insect parasitic on certain trees in India, Burma, Thailand and to a minor extent in other Asian countries. The larvae of the lac insect, Luccifer lucca (Kerr), swarm around the branches and twigs of the host trees for 2-3 days before inserting their probosces into the phloem tissues to reach the sap juices. There may be as many as 100-150 larvae on each inch of twig. This is followed by secretion of the lac surrounding the cells. Whereas the male insects subsequently move out of their cells the female insects become entombed for life. After about eight weeks of life the male insects fertilise the females and die within a few days. The fertilised females subsequently exude large quantities of lac and shed eyes and limbs. The female gives birth to 200-SO0 further insects and finally dies. In commercial practice the crop is taken from the tree shortly before emergence of the new brood. Some of these twigs are then tied to new trees to provide future sources of lac but the rest, sticklac, is subjected to further processing. The average yield per tree is about 20 Ib per annum, usually one crop being allowed per tree per year. Subsequent treatment of the sticklac carried out by hand or by mechanical methods first involves removal of woody matter and washing to remove the associated lac dye to produce seedlac, containing 34% of impurities. This may be further refined by various methods to produce the shellac flakes of commerce. The hand process for producing shellac has been used since ancient times and is carried on largely as a cottage industry. It has been estimated that 3-4 million people were dependent for their livelihood on this process. The lac encrustation is first separated from woody matter by pounding with a smooth stone, the latter being removed by a winnowing process. The lac dye is then removed by placing the lac in a pot together with a quantity of water. A villager, known as a ghasander, then stands in the pot and with bare feet treads out the dye from the resin. At one time lac dye was of commercial value but is today a worthless by- product. The product, seedlac, is then dried in the sun. The next stage may best be described as a primitive hot-filtration process. Two members of the village sit across the front of a simple fire resembling a Dutch oven, holding between them a bag about 30 feet long and about two inches in diameter. The lac inside the bag melts and, through one of the operators twisting the end of the bag, the lac is squeezed out. The lac is then removed from the outside of the bag and collected into a molten lump which is then stretched out 868 Miscellaneous Plastics Materials by another operator using both hands and feet until a brittle sheet is produced. This is then broken up to produce the shellac of commerce. In the factory processes the sticklac is first passed through crushing rollers and sieved. The lac passes through the sieve but retains the bulk of the woody matter. The sieved lac is then washed by a stream of water and dried by a current of hot air. A second mechanical cleaning process removes small sticks which have not been removed in the earlier roller process. The product, seedlac, now contains 3-8% of impurities. The seedlac may then be converted to shellac by either a heat process or by solvent processes. In the heat process the resin is heated to a melt which is then forced through a filter cloth which retains woody and insoluble matter. In the solvent process the lac is dissolved in a solvent, usually ethyl alcohol. The solution is filtered through a fine cloth and the solvent recovered by distillation. Variation in the details of the solvent processes will produce different grades of shellac. For example, when cold alcohol is used, lac wax which is associated with the resin remains insoluble and a shellac is obtained free from wax. Thermally processed shellacs were greatly favoured for gramophone records as they were free from residual solvent and also contained a small quantity of lac wax which proved a useful plasticiser. 30.6.2 Chemical Composition The lac resin is associated with two lac dyes, lac wax and an odiferous substance, and these materials may be present to a variable extent in shellac. The resin itself appears to be a polycondensate of aldehydic and hydroxy acids either as lactides or inter-esters. The resin constituents can be placed into two groups, an ether- soluble fraction (25% of the total) with an acid value of 100 and molecular weight of about 550, and an insoluble fraction with an acid value of 55 and a molecular weight of about 2000. Hydrolysis of the resins will produce aldehydic acids at mild concentration of alkali (-iN); using more concentrated alkalis (5N) hydroxy acids are produced, probably via the aldehydic acids. Unfortunately most of the work done in order to analyse the lac resin was carried out before the significance of the hydrolysis conditions was fully appreciated. It does, however, appear to be agreed that one of the major constitutents is aleuritic acid (Figure 30.9). HO*(CH2),*CH-CH-(CH2)TCOOH AH AH Figure 30.9 This is present to the extent of about 30-40% and is found in both the ether- soluble and ether-insoluble fractions. Both free hydroxyl and free carboxyl groups are to be found in the resin. 30.6.3 Properties The presence of free hydroxy and carboxyl groups in lac resin makes it very reactive, in particular to esterification involving either type of group. Of particular interest is the inter-esterification that occurs at elevated temperatures (>7OoC) and Shellac 869 leads to an insoluble 'polymerised' product. Whereas ordinary shellac melts at about 75"C, prolonged heating at 125-150°C will cause the material to change from a viscous liquid, via a rubbery state, to a hard horny solid. One of the indications that the reaction involved is esterification is that water is evolved. The reaction is reversible and if heated in the presence of water the polymerised resin will revert to the soluble form. Thus shellac cannot be polymerised under pressure in a mould since it is not possible for the water to escape. 'Polymerisation' may be retarded by basic materials, some of which are useful when the shellac is subjected to repeated heating operations. These include sodium hydroxide, sodium acetate and diphenyl urea. 'Polymerisation' may be completely inhibited by esterifying the resin with monobasic saturated acids. A number of accelerators are also known, such as oxalic acid and urea nitrate. Unmodified lac polymerises in about 45 minutes at 150°C and 15 minutes at 175°C. Shellac is soluble in a very wide range of solvents, of which ethyl alcohol is most commonly employed. Aqueous solutions may be prepared by warming shellac in a dilute caustic solution. The resin is too brittle to give a true meaning to mechanical properties. The thermal properties are interesting in that there appears to be a transition point at 46°C. Above this temperature, specific heat and temperature coefficient of expansion are much greater than below it. The specific heat of hardened shellac at 50°C is lower than that of unhardened material, this no doubt reflecting the disappearance, or at least the elevation, of the transition temperature. Table 30.4 Some properties of shellac Property Condition Units Value Specific gravity Refractive index Colour Specific heat Volume resistivity Surface resistivity Dielectric constant Dielectric loss (50 Hz) (SO Hz) 15.S"C - - 10-40°C 45-50°C (heat hardened) 20°C 20%RH 40%RH 30°C 80°C 30T 80°C c.g.s. c.g.s. Rm R R - 1.20 1 .S 1-1.53 pale yellow-dark red 0.36-0.38 0.56 1.8 X 10l8 2.2 x 1014 1.1 x 1014 3.91 7.85 0.02 0.435 From the point of view of the plastics technologist the most important properties of shellac are the electrical ones. The material is an excellent room temperature, low-frequency insulator and particular mention should be made of the resistance to tracking. Some typical physical properties of shellac are given in Table 30.4. 30.6.4 Applications Until 1950 the principal application of shellac was in gramophone records. The resin acted as a binder for about three times its weight of mineral filter, e.g. slate 870 Miscellaneous Plastics Materials dust. The compound had a very low moulding shrinkage and was hard-wearing but not suitable for the microgroove records because of the effect of the filler on the background noise. Today the most important applications are in surface coatings, including some use as French polish, as adhesives and cements, including valve capping and optical cements, for playing card finishes and for floor polishes. The material also continues to be used for hat stiffening and in the manufacture of sealing wax. Although development work on shellac in blends with other synthetic resins has been carried out over a period of time, the only current use in the plastics industry is in the manufacture of electrical insulators. At one time electrical insulators and like equipment were fabricated from mica but with increase in both the size and quantity of such equipment shellac was introduced as a binder for mica flake. For commutator work the amount of shellac used is only 3-5% of the mica but in hot moulding Micanite for V-rings, transformer rings etc., more than 10% may be used. The structures after assembly are pressed and cured, typically for two hours at 150-160°C under pressure. In recent years the dominance of shellac in mica-based laminates has met an increasing challenge from the silicone resins. 30.7 AMBER In addition to shellac a number of other natural resins find use in modern industry. They include rosins, copals, kauri gum and pontianak. Such materials are either gums or very brittle solids and, although suitable as ingredients in surface coating formulations and a miscellany of other uses, are of no value in the massive form, i.e. as plastics in the most common sense of the word. One resin, however, can be considered as an exception to this. Although rarely recognised as a plastics material it can be fabricated into pipe mouthpieces, cigarette holders and various forms of jewellery. It may also be compression moulded and extruded. It is the fossil resin amber. Amber is of both historical and etymological interest as its property of attracting dust was known over 2000 years ago. From the Greek word for amber, elektron, has come the word electricity. Pliny in his works makes an interesting and informative dissertation on the occurrence and properties of amber. Amber is a fossil resin produced in the Oligocene age by exudation from a now extinct species of pine. It occurs principally in the region known before World War I1 as East Prussia. It may be obtained by mining and also by collecting along the seashore. Small amounts of amber may also be found off the coasts of England, Sweden, Holland and Denmark. Similar resins are found in Burma, Rumania and Sicily but only the Baltic variety, known also as succinite, is considered a true amber. At one time a Royal Amber Works existed in Konigsberg (now Kaliningrad) and in 1900 annual production was approximately 500 tons. 30.7.1 Composition and Properties The chemical nature of amber is complex and not fully elucidated. It is believed not to be a high polymer, the resinous state being accounted for by the complexity of materials present. The empirical formula is C10H160 and true amber yields on distillation 3-8% of succinic acid. Bituminous Plastics 871 The resin is fairly soluble in alcohol, ether and chloroform and is decomposed by nitric acid. It becomes thermoplastic at temperatures above 150°C and decomposes at a temperature rather below 300"C, yielding an oil of amber and leaving a residue known as amber colophony or amber pitch. X-ray evidence shows the material to be completely amorphous as might be expected from such a complex mixture. The specific gravity ranges from 1.05 to 1.10. It is slightly harder than gypsum and therefore just not possible to scratch with a fingernail. Yellow in colour, it is less brittle than other hard natural resins and may therefore be carved or machined with little difficulty. The refractive index is 1.54. Amber has been a much prized gem material for many millennia and has been found at Stonehenge, in Mycenaen tombs and in ancient European lake dwellings. In modern times it is used for beads and other ornaments, cigarette holders and pipe mouthpieces. At one time the small fragments of amber produced during the fabrication and machining operations were used to produce varnishes. In 1880 they were first used in the production of Ambroid. This is made by pressing the fragments in a hydraulic press at temperatures somewhat above 160°C. The moulded product has a close resemblance to amber. A form of extrusion has also been used to produce amber rods for subsequent conversion into pipe and cigarette-holder mouthpieces. 30.8 BITUMINOUS PLASTICS Although generally ignored in plastics literature the bituminous plastics are still of interest for specific applications. The moulding compositions consist of fibrous and mineral fillers held together by a bituminous binder together with a number of minor ingredients. A number of types of bituminous material exist and terminology is still somewhat confusing. The term bitumens in its widest sense includes liquid and solid hydrocarbons but its popular meaning is restricted to the solid and semisolid materials. The bitumens occur widely in nature and may be considered to be derived from petroleum either by evaporation of the lighter fraction under atmospheric conditions or by a deeper seated metamorphism. The purer native bitumens are generally known as asphaltites and include Gilsonite, extensively used for moulding, which occurs in Utah. Where the bitumens are associated with mineral matter the mixture is referred to as native asphalt. These are widely distributed in nature, the best known deposit being the asphalt lake in Trinidad which covers an area of about 100 acres (40 hectares). The terms asphalt or asphaltic bitumen are applied to petroleum distillation residues and these today form the bulk of commercial bituminous matter. Related chemically and in application but not in origin are the pitches. These are the industrial distillation residues. They inc!ude wood tar, stearin pitch, palm oil pitch and coal tar pitch. The last varies from soft semisolid to hard brittle products. Of these materials those most useful in moulding compositions are coal tar pitches with a softening range of llS-130"C and natural bitumens such as Gilsonite and Rafaelite with softening points in the range 130-160°C. The bitumens are complex mixtures of paraffinic, aromatic and naphthenic hydrocarbons. A small amount of unsaturation is usually present which accounts 872 Miscellaneous Plastics Materials for the slow oxidation which occurs on exposure to ultra violet light and the ability to bring about a form of vulcanisation on heating with sulphur. The bulk of bituminous materials are used for road making and building applications which are outside the scope of this book. Only a very small percentage is used in moulding compositions and few data have been made publicly available concerning the properties of these compositions. The bitumens have a good order of chemical corrosion resistance, have reasonably good electrical insulation properties and are very cheap. Their main disadvantages are their black colour and their somewhat brittle nature. Moulding compositions contain a number of ingredients. These may include: (1) Bituminous binder. (2) Fibrous filler. (3) Inert filler. (4) Softener. (5) Drying oil and drier. Of the fibrous fillers which greatly reduce the brittleness, blue asbestos fibre is normally used for battery boxes, the principal outlet. Other materials that may be used include cotton fibres, ground wood, slag wool and ground cork. Mineral fibres are incorporated to reduce cost and to raise the softening point. China clay, natural silicas, talc and slate dust are frequently used. To facilitate moulding a softener is incorporated. These may include soft industrial pitches or heavy tars, coumarone-indene resins or waxes. In the United States softer stocks have been employed using a drying oil which is incorporated with a drier such as cobalt naphthenate to harden the oil. The compositions are mixed in heated trough mixers, the mixing tem- perature being in the range of 150-200°C. Skill is required in order to achieve good dispersion of the fibrous filler without charring the butuminous matter. Moulding is carried in compression moulds using prewarmed doughs. For battery boxes the mould temperature on charging the composition is about 1OO"C, which is reduced to at least 50°C before extraction of the moulding. Some simple mouldings can be carried out using prewarmed mixes but cold moulds. The largest outlet for the bituminous plastics has been for automobile battery boxes. Bituminous battery boxes do, however, have a susceptibility to electrical breakdown between the cells and in Europe their use has been mainly confined to the cheaper batteries installed initially in new cars. Bituminous compositions have also been used for toilet cisterns and to some extent for cheap containers. They are no longer important. Bibliography Casein COLLINS, J. H., Casein Plastics, Plastics Institute Monograph No. C5, 2nd Edn, London (1952) PINNER, s. H., Brit. Plastics, 18, 313 (1946) SUTERMEISTER, F., and BROWNE, F. L., Casein and its industrial Applications, American Chemical Society, Monograph No 30, New York (1939) Rubber, Derivatives of Rubber and Similar Polymers BLOW, c. M., and HEPBURN, c. (Eds.), Rubber Technology and Manufacture (2nd Edition), Butterworths, London (1982) Bibliography 873 BRYDSON, I. A., Rubber Chemistry, Applied Science, London (1978) BRYDSON, J. A,, Rubbery Materials and their Compounds, Applied Science, London (1988) DAVIES, B. L., and GLAZER, J., Plastics derived from Natural Rubber, Plastics Institute Monograph No. NAUNTON, w. J. s. (Ed.), The Applied Science of Rubber, Arnold, London (1961) SCOTT, J. R., Ebonite, MacLaren, London (1958) Shellac CIDVANI, B. s. Shellac and Other Natural Resins, Plastics Institute Monograph No. S1, 2nd Edn. Shellac, Angelo Brothers Ltd., Calcutta (1956) Amber HERBERT SMITH, G. F., Gemstones, Methuen, London (1952) LEY, WILLY, Dragons in Amber, Sidgwick and Jackson, London (1951) Pliny, Book 37, Chapter 3 C8, London (1955) London ( 1954) 31 Selected Functional Polymers 3 I. 1 INTRODUCTION Chapters 10 to 29 consisted of reviews of plastics materials available according to a chemical classification, whilst Chapter 30 rather more loosely looked at plastics derived from natural sources. It will have been obvious to the reader that for a given application plastics materials from quite different chemical classes may be in competition and attempts have been made to show this in the text. There have, however, been developments in three, quite unrelated, areas where the author has considered it more useful to review the different polymers together, namely thermoplastic elastomers, biodegradable plastics and elec- trically conductive polymers. All three types of material have now been available for some years and it is probably also true that none have yet realised their early promise. In the case of the thermoplastic elastomers most of the commercial materials have received brief mention in earlier chapters, and when preparing earlier editions of this book the author was of the opinion that such materials were more correctly the subject of a book on rubbery materials. However, not only are these materials processed on more or less standard thermoplastics processing equipment, but they have also become established in applications more in competition with conventional thermoplastics rather than with rubbers. The concept of degradable polymers arose largely from concern about the large quantities of plastics materials used for packaging and which, having fulfilled their function, were then discarded and unwanted. Interest has, however, now moved on to include medical and related applications. Electrically conductive polymers are just one of a number of esoteric possible uses for synthetic polymers. These materials are now being considered for a variety of applications. 3 1.2 THERMOPLASTIC ELASTOMERS It was pointed out in Chapter 3 that conventional vulcanised rubbers were composed of highly flexible long chain molecules with light cross-linking 874 Thermoplastic Elastomers 875 (covalently) which enabled the chains to coil and uncoil but prevented them slipping past each other. This gives a highly extensible network structure. Once cross-linking has taken place, such materials cannot be reprocessed (at least without severe degradation). In addition, the ‘setting’ operation involves a chemical reaction rather than the, apparently, simpler setting brought about by cooling as used with thermoplastics materials. For this reason, many attempts have been made over the years to produce a rubbery material which has a network structure over a useful temperature range but which, if heated further, loses this structure. In many cases this involves a form of cross-linking that is said to be heatfugitive. In Section 3.4 four types of heat-fugitive cross-link were identified, namely: (1) Ionic cross-links. (2) Hydrogen bonding. (3) Triblock copolymers. (4) Multiblock copolymers. A further important class of thermoplastic elastomer has been obtained by blending a rubbery material (usually an ethylene-propylene rubber) with a polyolefin (usually polypropylene, sometimes in conjunction with polyethyl- ene). In this case the thermoplastic material tends to be the continuous phase and the rubbery material (which is often subjected to a cross-linking operation during the mixing stage (dynamic vulcanisation) the discrete phase. It is conceptually difficult to see why a system consisting of tiny vulcanised rubbery spheres embedded in a rigid thermoplastics material should be capable of showing rubbery behaviour. The explanation lies in the fact that the morphology is more complex, and it is better to consider the hard phase as a reticulated structure which allows large-scale deformations to occur (rather like that in a human skeleton), with the rubbery phase facilitating the recovery from deformation. The main commercial types of thermoplastic elastomers are: (I) Styrene-butadiene-styrene triblocks and the related S-I-S and SEBS (2) Polyester-based thermoplastic polyurethane elastomers (Section 27.4). (3) Polyether-based thermoplastic polyurethane elastomers (Section 27.4). (4) Thermoplastic polyester elastomers (Section 25.10). (5) Thermoplastic polyamide elastomers (Section 18.15). (6) Thermoplastic polyolefin rubbers (Section 11.9). materials (Section 11.8). It may also be argued that plasticised PVC may be considered as a thermoplastic elastomer, with the polymer being fugitively cross-linked by hydrogen bonding via the plasticiser molecules. These materials were, however, dealt with extensively in Chapter 12 and will not be considered further here. The ionomers are also sometimes considered as thermoplastic elastomers but the commercial materials are considered in this book as thermoplastics. It should, however, be kept in mind that ionic cross-linking can, and has, been used to fugitively cross- link elastomeric materials. This section is intended to summarise some basic principles of the chemistry of such materials and to compare the various types. 876 Selected Functional Polymers Although there will be specific requirements for specific applications, the principal properties of importance with the thermoplastic elastomers are: (1) The minimum temperature at which the material will be a serviceable (2) The maximum service temperature. (3) Oil resistance and chemical resistance. (4) The range of hardness possible. (5) Recovery from deformation and general high-elasticity properties. (6) Density. (7) Cost, not simply raw material cost, but the cost of making, installing and rubber. servicing the product. The minimum service temperature is determined primarily by the Tg of the soft phase component. Thus the SBS materials can be used down towards the Tg of the polybutadiene phase, approaching -100°C. Where polyethers have been used as the soft phase in polyurethane, polyamide or polyester, the soft phase Tg is about -6O"C, whilst the polyester polyurethanes will typically be limited to a minimum temperature of about 40°C. The thermoplastic polyolefin rubbers, using ethylene-propylene materials for the soft phase, have similar minimum temperatures to the polyether-based polymers. Such minimum temperatures can also be affected by the presence of plasticisers, including mineral oils, and by resins if these become incorporated into the 'soft' phase. It should, perhaps, be added that if the polymer component of the soft phase was crystallisable, then the higher T, would also affect the minimum service temperature, this depending on the level of crystallinity. It should also be pointed out that the Tg of the soft blocks, which consist of fairly short polymer chains, will be somewhat lower than for a corresponding homopolymer of high molecular weight, for the reasons given in Section 4.2. This effect may, however, be more than compensated by the loss of molecular freedom due to the presence of and interaction with the hard phase polymer present. Providing the polymer is thermally stable in the range under consideration, the maximum service temperature is largely determined by the Tg of the hard phase (or the T, if the hard phase is crystallisable). As a general rule, thermoplastic elastomers with a crystallisable hard phase will be usable to higher temperatures, although some amorphous thermoplastic polyamide elastomers with a high hard phase Tg can have good maximum service temperatures. As pointed out in the previous paragraph, the effective Tg (and for that matter T,) of the short polymer blocks may differ somewhat from the transition points of a high molecular weight homopolymer. Oil resistance demands polar (non-hydrocarbon) polymers, particularly in the hard phase. If the soft phase is non-polar but the hard phase polar, then swelling but not dissolution will occur (rather akin to that occurring with vulcanised natural rubber or SBR). If, however, the hard phase is not resistant to a particular solvent or oil, then the useful physical properties of a thermoplastic elastomer will be lost. As with all plastics and rubbers, the chemical resistant will depend on the chemical groups present, as discussed in Section 5.4. Most of the thermoplastic elastomers can be produced in a wide hardness range without resort to additives. If it is practical to use soft and hard phases in any proportions, then the hardness range will be from that of the soft phase [...]... resins, 675 -7, 679 -80 vinyl chloride polymers, 355-8 Aramid fibres, 9, 514-15, 77 3 Arc resistance, 110, 122 Ardel, 72 9 Ardil, 9, 860 Ametal, 528 Amite, 6 07 Arnitel, 73 8 Amite PBTP, 72 4 Amite PETP, 72 0, 72 1 Aromatic diamines, 78 7 Aromatic polyamide fibres, 514-15 Aromatic polycarbonates, 72 Aromatic polyester, 55 Aromatic polyimides, 72 Arrhenius equation, 1 67 Arylef, 608, 73 1 Arylon T, 4 47, 602, 73 1 Aryloxa,... Binary copolymers, 27 Biocellat, 6 27 Bioceta, 6 27 Biodegradable plastics, 13, 880 Biodegradation, 153, 880-84 Biomax 881, 886 Biopol, 883, 885, 886 Birefringence methods, 48 Bis-phenol A polycarbonates, 51, 72 , 86, 5. 57, 558 alloys based on, 577 -8 applications, 575 -7 glass transition temperature, 62, 114 Bitumen, 1-2, 19, 871 -2 Bituminous plastics, 871 -2 Biuret links, 78 5, 79 0, 79 4 Bleeding, 125, 140,... compositions, 71 1-2 N-Alkyl compounds, 505 Alkyl, 2-cyanoacrylate, 4 19 Alkylene oxides, 546 -7 n-Alkyl groups, 59 Alkyl lithium, 36 Allyl resins, 70 8 -70 9 Alphanol, 79 , 331 Alternating copolymers, 27 Aluminium chloride, 34 Aluminium hydroxide, 1 27 Aluminium stearate, 3 37 Aluminium triethyl, 209 Amber, 2, 19, 870 -1 composition and properties, 870 - 1 Ambroid, 871 Amine flexibilisers, 77 0-1 Amine hardening... colorants, 124, 149-50, 79 7 coupling agents, 128-31 cross-linking agents, 124, 153-4 epoxide resins, 76 8 -72 fillers, 124, 126-9, 279 , 280, 79 8 flame retarders, 104-109, 124, 145-9, 229, 496, 4 97 flow promoters, 124, 132-4 fungicides, 496 heat stabilisers, 496, 4 97 isotactic polypropylene, 2 6 G 6 I light stabilisers, 496, 4 97 lubricants, 124, 132-4, 496, 4 97 nucleating agents, 496, 4 97 2-Oxazolines, 155-8... 27 1 polypropylene, 265 -7, 878 , 894-5 polysulphones, 601-2 polytetrafluoroethylene, 372 -3 polyurethane rubbers, 78 8-9 poly(viny1 alcohol), 395, 882, 898 poly(viny1 chloride) (PVC), 355-8 shellac, 869 -70 silicone fluids, 826-8 silicone resins, 829-32 silicone rubbers, 838-9 styrene-based plastics, 461-3 styrene-butadiene rubber (SBR), 863 thermoplastic elastomers, 878 -80 urea-formaldehyde resins, 675 -7, ... resorcinol-formaldehyde, 662 urea-formaldehyde resins, 677 -8 Adipic acid, 9, 21 480 Adiprene C 78 7, 78 8 Aerodux, 189, 662 Aflas, 382 Aflon, 374 AFT-2000, 5 15 Aggregation states, 43-58 cross-linked structures, 53-5 crystalline polymers, 49-53 linear amorphous polymers, 43-9 polyblends, 55-9 Aging, 76 , 99, 231, 342, 878 Agriculture, 14 Air-dried sheet (ADS), 282 Alcoholysis, 390 Alcryn, 879 Aldehydes, 5, 546, 639 Algoflan,... Barex, 416, 4 17 Barytes, 338 BASF process, 456 Basic lead carbonate (white lead), 3 27 Bayblend, 4 47, 578 Baymid, 808 Baypren, 295 BDS K-resin, 438 Bead processes, 456 -7 Beckamides, 506 Bell test, 226 Benzene, 9, 10, 112 Benzene rings, 95, 562, 572 Benzoates, 328 Benzoyl peroxide, 25 Benzyl cellulose, 632 Beta-conidendrol, 535 Biapen, 589 Biaxial orientation, 192 Biaxial stretching, 48, 52, 2 57, 460, 71 9... related materials, 143 -7 Anti-blocking agents, 229 Antimony oxide, 148-9, 342, 70 1 Antioxidants, 98, 134-43, 230-31, 279 , 866 chain-breaking, 135-42 in polypropylene, 156, 258 preventive, 135, 140 Antiozonants, 134, 279 , 284 Antiplasticisation, 89 APE, 73 1 Apec HT, 565 Applications: ABS plastics, 448 acetal resins, 544-6 his-phenol A polycarbonates, 575 -8 casein, 859 cellulose acetate, 626 -7 Index... branching, 64, 72 Chain coiling, 44-5 Chain degradation, 97 Chain ends, 62-3 Chain flexibility, 59, 72 Chain growth, 27, 28, 34 Chain mobility, 62, 64 Chain separation, 62 Chain stiffness, 70 Chain transfer, 26 Chain transfer agents, 26, 209 Chain uncoiling, 44-5, 47, 172 , 195, 202 Charpy test, 192-4 Chelating agents, 1 4 0 4 1 Chemical blowing agents, 153 Chemical bonds, 76 -80 Chemical nature of plastics, ... strength (ft I b h notch)* Ball-drop impact strength (J) Shrinkage across flow ( m m h m ) Shrinkage with flow ( m m h m ) Stiffness modulus (MPa) 698-1 120 35- 57 1.4-4.0 0.113-6.666 0-0.005 0-0.006 15 17- 21 37 578 -898 16- 28 0.9-8.3 5.1 97- 13.558 0.0 07- 0. 016 0.0 10-0.014 620-1241 ~ ~ ~ ~ *Imd figures cannot realistically be converted from the f.p.s units of the original data 32.2 ESTABLISHING OPERATIONAL REQUIREMENTS . 190 (T,) Good 190 (T,) Good 190 (T,) Good 120- 275 (T,) Good 14O -165 (Tm) Poor 60-90A 30-40A 65 -75 A 70 A -70 D 40-90A 75 A-65D 60A -75 D 35 -75 D 0.94 0.92 0.91 1.18-1.24 1.1 1.15-1.45. reasonable rate, plastics materials have been particularly criticised. For more than 20 years, polymer scientists and plastics technologists have been working to develop plastics materials that. for by the complexity of materials present. The empirical formula is C10H160 and true amber yields on distillation 3-8% of succinic acid. Bituminous Plastics 871 The resin is fairly soluble