Plastics Materials 7 Episode 8 ppt

Poly(viny1 acetate) 387 - 1 18 kJ/mole CHrCH + CH,COOH - CH,=CH I OOC . CH, CH,=CH + CH,COOH - CH, . COO CH . CH, I \ / OOC . CH, CH, . COO Figure 14.1 In a typical system the reaction vessel is at 75-80°C and the vinyl acetate formed is swept out into a condenser at 72-74°C by means of circulating excess acetylene. This prevents distillation of higher boiling components but allows the vinyl acetate and acetylene through. The former is separated out by cooling and the acetylene recycled. Vapour phase synthesis may be carried out by passing a mixture of acetylene and acetic acid through a reaction tube at 210-215°C. Typical catalysts for this reaction are cadmium acetate, zinc acetate and zinc silicate. The monomer in each of the above mentioned processes is purified by distillation. Purified monomer is usually inhibited before shipment by such materials as copper resinate, diphenylamine or hydroquinone, which are generally removed before polymerisation. The monomer is a sweet-smelling liquid partially miscible with water and with the following properties: boiling point at 760mmHg, 72.5"C; specific gravity at 20"C, 0.934; refractive index nD20, 1.395; vapour pressure at 20°C 90mmHg. In 1953 the Celanese Corporation of America introduced a route for the production of vinyl acetate from light petroleum gases. This involved the oxidation of butane which yields such products as acetic acid and acetone. Two derivatives of these products are acetic anhydride and acetaldehyde, which then react together to give ethylidene diacetate (Figure 14.2.) OC-CH, OOC . CH, Figure 14.2 Exposure of the ethylidene diacetate to an aromatic sulphonic acid in the presence of five times its weight of acetic anhydride as diluent at 136°C will yield the following mixture: 40% vinyl acetate; 28% acetic acid; 20% acetic anhydride; 4% ethylidene diacetate; 8% acetaldehyde. The latter four products may all be reused after separation. In recent years vinyl acetate has been prepared in large quantities by oxidation of ethylene. If ethylene is passed into a solution of palladium chloride in acetic acid containing sodium acetate, then vinyl acetate, ethylene diacetate and acetaldehyde are produced, the vinyl acetate being obtained in good yields by the reaction shown in Figure 14.3 388 Poly(viny1 acetate) and its Derivatives CH,=CH, + 2CH,COONa + PdC1, CH, COOH - CH,= CH + Pd + 2NaC1 + CH, COOH I OOC . CH, Figure 14.3 The ethylene oxidation process can be carried out in either a liquid or a vapour phase but the latter method is often preferred because it avoids corrosion problems and the use of solvents. A one-stage process for producing vinyl acetate directly from ethylene has also been disclosed. In this process ethylene is passed through a substantially anhydrous suspension or solution of acetic acid containing cupric chloride and copper or sodium acetate together with a palladium catalyst to yield vinyl acetate. 14.2.2 Polymerisation Vinyl acetate may be easily polymerised in bulk, solution, emulsion and suspension. At conversions above 30%, chain transfer to polymer or monomer may occur. In the case of both polymer and monomer transfer two mechanisms are possible, one at the tertiary carbon, the other (illustrated in Figure 14.4) at the acetate group. H I CH, - CH - + CH,-C I OOC . CH, I OOC . CH, Radical Polymer H I I - wCH, - CH, + CH,-C OOC . CH,- I OOC . CH, Polymer Radical Figure 14.4 The radical formed at either the tertiary carbon atom or at the acetate group will then initiate polymerisation and form branched structures. Since poly(viny1 acetate) is usually used in an emulsion form, the emulsion polymerisation process is commonly used. In a typical system, approximately equal quantities of vinyl acetate and water are stirred together in the presence of a suitable colloid-emulsifier system, such as poly(viny1 alcohol) and sodium lauryl sulphate, and a water-soluble initiator such as potassium persulphate. Polymerisation takes place over a period of about 4 hours at 70°C. The reaction is exothermic and provision must be made for cooling when the batch size exceeds a few litres. In order to achieve better control of the process and to Poly(viny1 alcohol) 389 obtain particles with a smaller particle size, part of the monomer is first polymerised and the rest, with some of the initiator, is then steadily added over a period of 3-4 hours. To minimise the hydrolysis of vinyl acetate or possible comonomers during polymerisation, it is necessary to control the pH throughout reaction. For this purpose a buffer such as sodium acetate is commonly employed. 14.2.3 Properties and Uses Poly(viny1 acetate) is too soft and shows excessive 'cold flow' for use in moulded plastics. This is no doubt associated with the fact that the glass transition temperature of 28°C is little above the usual ambient temperatures and in fact in many places at various times the glass temperature may be the lower. It has a density of 1.19g/cm3 and a refractive index of 1.47. Commercial polymers are atactic and, since they do not crystallise, transparent (if free from emulsifier). They are successfully used in emulsion paints, as adhesives for textiles, paper and wood, as a sizing material and as a 'permanent starch'. A number of grades are supplied by manufacturers which differ in molecular weight and in the nature of comonomers (e.g. vinyl maleate) which are commonly used (see Section 14.4.4) The polymers are usually supplied as emulsions which also differ in the particle size, the sign of the charge on the particle, the pH of the aqueous phase and in other details. Being an amorphous polymer with a solubility parameter of 19.4 MPa'12, it dissolves in solvents with similar solubility parameters (e.g. benzene 6 = 18.8MPa1", chloroform 6 = 19.0MPa'/2, and acetone 6 = 20.4MPa'12. 14.3 POLY(V1NYL ALCOHOL) Vinyl alcohol does not exist in the free state and all attempts to prepare it have led instead to the production of its tautomer, acetaldehyde. CH,=CH + CH,CHO I OH Poly(viny1 alcohol) is thus prepared by alcoholysis of a poly(viny1 ester) and in practice poly(viny1 acetate) is used (Figure 14.5). - CH,- CH- + CH,OH CH,-CH* I I OCC . CH, Figure 14.5 OH + CH,COOCH, The term hydrolysis is sometimes incorrectly used to describe this process. In fact water does not react readily to yield poly(viny1 alcoho1)s and may actually retard reaction where certain catalysts are used. Either methanol or ethanol may be used to effect alcoholysis but the former is often preferred because of its miscibility with poly(viny1 acetate) at room 390 temperature and its ability to give products of better colour. Where methanol is employed, methyl acetate may be incorporated as a second solvent. It is also formed during reaction. The concentration of poly(viny1 acetate) in the alcohol is usually between 10 and 20%. Either acid or base catalysis may be employed. Alkaline catalysts such as caustic soda or sodium methoxide give more rapid alcoholysis. With alkaline catalysts, increasing catalyst concentration, usually less than 1% in the case of sodium methoxide, will result in decreasing residual acetate content and this phenomenon is used as a method of controlling the degree of alcoholysis. Variations in reaction time provide only a secondary means of controlling the reaction. At 60°C the reaction may takes less than an hour but at 20°C complete ‘hydrolysis’ may take up to 8 hours. The use of acid catalysts such as dry hydrochloric acid has been described in the literature but are less suitable when incompletely ‘hydrolysed’ products are desired as it is difficult to obtain reproducible results. Commercial poly(viny1 alcohol) (e.g. Gelvatol, Elvanol, Mowiol and Rhodo- viol) is available in a number of grades which differ in molecular weight and in the residual acetate content. Because alcoholysis will cause scission of branched polymers at the points where branching has proceeded via the acetate group, poly(viny1 alcohol) polymer will have a lower molecular weight than the poly(viny1 acetate) from which it is made. Poly(viny1 acetate) and its Derivutives 14.3.1 Structure and Properties Poly(viny1 acetate) is an atactic material and is amorphous. Whilst the structure of poly(viny1 alcohol) is also atactic the polymer exhibits crystallinity and has essentially the same crystal lattice as polyethylene. This is because the hydroxyl groups are small enough to fit into the lattice without disrupting it. The presence of hydroxyl groups attached to the main chain has a number of significant effects. The first effect is that the polymer is hydrophilic and will dissolve in water to a greater or lesser extent according to the degree of ‘hydrolysis’ and the temperature. Polymers with a degree of ‘hydrolysis’ in the range of 8749% are readily soluble in cold water. An increase in the degree of ‘hydrolysis’ will result in a reduction in the ease of solubility and fully ‘hydrolysed’ polymers are only dissolved by heating to temperatures above 85°C. This anomalous effect is due to the greater extent of hydrogen bonding in the completely ‘hydrolysed’ polymers. Hydrogen bonding also leads to a number of other effects, for example, unplasticised poly(viny1 alcohol) decomposes below its flow temperature. The polymer also has a very high tensile strength and is very tough. Films cast from high molecular weight grades, conditioned to 35% humidity, are claimed2 to have tensile strengths as high as 180001bf/in2 (I 25 MPa). The properties will be greatly dependent on humidity; the higher the humidity, the more the water absorbed. Since water acts as a plasticiser there will be a reduction in tensile strength but an increase in elongation and tear strength. Figure 14.6 shows the relationship between tensile strength, percentage ‘hydrolysis’ and humidity. Because of its high polarity, poly(viny1 alcohol) is very resistant to hydrocarbons such as petrol. Although the polymer will dissolve in lower alcohol- water mixtures, it does not dissolve in pure alcohols. As it is crystalline as well as The Poly(viny1 acetals) 39 1 I 50 40 DEGREE OF HYDROLYSIS IN o/r Figure 14.6. Relation between tensile strength and degree of ‘hydrolysis’ for unplasticised poly(viny1 alcohol) film. (After Davidson and Sittig’) highly polar only a few organic solvents, such as diethylenetriamine and triethylenetetramine, are effective at room temperature. As might be expected, the hydroxyl group is very reactive and many derivatives have been prepared. The polymer may be plasticised by polar liquids capable of forming hydrogen bonds with the hydroxyl groups. Glycerin has been used for this purpose. 14.3.2 Applications Poly(viny1 alcohol) is employed for a variety of purposes. Film cast from aqueous alcohol solution is an important release agent in the manufacture of reinforced plastics. Incompletely ‘hydrolysed’ grades have been developed for water-soluble packages for bath salts, bleaches, insecticides and disinfectants. Techniques for making tubular blown film, similar to that used with polyethylene, have been developed for this purpose. Moulded and extruded products which combine oil resistance with toughness and flexibility are produced in the United States but have never become popular in Europe. Poly(viny1 alcohol) will function as a non-ionic surface active agent and is used in suspension polymerisation as a protective colloid. In many applications it serves as a binder and thickener is addition to an emulsifying agent. The polymer is also employed in adhesives, binders, paper sizing, paper coatings, textile sizing, ceramics, cosmetics and as a steel quenchant. Japanese workers have developed fibres from poly(viny1 alcohol). The polymer is wet spun from warm water into a concentrated aqueous solution of sodium sulphate containing sulphuric acid and formaldehyde, the latter insolubilising the alcohol by formation of formal groups. 14.4 THE POLY(V1NYL ACETALS) Treatment of poly(viny1 alcohol) with aldehydes and ketones leads to the formation of poly(viny1 acetals) and poly(viny1 ketals), of which only the former products are of any commercial significance (Figure 14.7). 392 Poly(viny1 acetate) and its Derivatives wCH,-CH-CH,-CH-CHz-CH-CHz-CH-CHz-CH~ I OH I OH I OH I OH I OH 0 II C 0 II C wCH,-CH-CH,-CH-CH,-CH-CH,-~~-~~z-~~w I I I I I A Poly(Viny1 Acetal) Figure 14.7 The products are amorphous resins whose rigidity and softening point depend on the aldehyde used. Poly(viny1 butyral), with the larger side chain, is softer than poly(viny1 formal). Since the reaction between the aldehyde and the hydroxyl groups occurs at random, some hydroxyl groups become isolated and are incapable of reaction. A poly(viny1 acetal) molecule will thus contain: (1) Acetal groups. (2) Residual hydroxyl groups. (3) Residual acetate groups, due to incomplete 'hydrolysis' of poly(viny1 acetate) to poly(viny1 alcohol). 14.4.1 Poly(viny1 formal) The poly(viny1 acetals) may be made either from poly(viny1 alcohol) or directly from poly(viny1 acetate) without separating the alcohol. In the case of poly(viny1 formal) the direct process is normally used. In a typical process, 100 parts of poly(viny1 acetate) are added to a mixture of 200 parts acetic acid and 70 parts water, which has been warmed to about 70°C, and stirred to complete solution. Sixty parts of 40% formalin and 4 parts sulphuric acid (catalyst) are added and reaction is carried out for 24 hours at 70°C. Water is added to the mixture with rapid agitation to precipitate the granules, which are then washed free from acid and dried. A number of grades of poly(viny1 formal) are commercially available (Formvar, Mowital) which vary in degree of polymerisation, hydroxyl content and residual acetate content. Table 14.13 shows the influence of these variables on some properties. The residual hydroxyl content is expressed in terms of poly(viny1 alcohol) content and residual acetate in terms of poly(viny1 acetate) content. The Poly(viny1 acetals) 393 Table 14.1 Influence of structure variables on the properties of poly(viny1 formal) 500 5-6 9.5-13 160-170 88-93 10 69 7-20 1.2-2.0 0.75 Av. D. of P. Poly(viny1 alcohol) (%) Poly(viny1 acetate) (%) Flow temperature (“C) Deflection temperature Tensile strength (lo-’ under load Ibfhn’) (MPa) Elongation (%) Impact strength (hod f in X f in) (ft lbf in -’) Water absorption (%) 500 7-9 9.5-13 160-170 88-93 10 69 10-50 1.2-2.0 1.1 ASTM test - - - D.569-48T D.648-49T D.638-41T - D.638-41T D.256-43T D.570-40T Various grades of poly(vinyl formal) 350 7-9 9.5-13 140-145 88-93 10 69 10-50 1.0-1.4 1.1 430 5-7 20-27 145-150 75-80 10 69 4-5 0.5-0.7 1.5 350 5 -7 40-50 50-60 - 10 69 3-4 0.4-0.6 1-5 It will be observed that molecular weight has little effect on mechanical properties but does influence the flow temperature. The hydroxyl content of commercial material is kept low but it is to be observed that this has an effect on the water absorption. Variation in the residual acetate content has a significant effect on heat distortion temperature, impact strength and water absorption. The incorporation of plasticisers has the usual influence on mechanical and thermal properties. The polymer, being amorphous, is soluble in solvents of similar solubility parameter, grades with low residual acetate being dissolved in solvents of solubility parameter between 19.8 and 22 MPa’”. The main application of poly(viny1 formal) is as a wire enamel in conjunction with a phenolic resin. For this purpose, polymers with low hydroxyl (5-6%) and acetate (9.5-13%) content are used. Similar grades are used in structural adhesive (e.g. Redux) which are also used in conjunction with phenolic resin. Poly(viny1 formal) finds some use as a can coating and with wash primers. Injection mouldings have no commercial significance since they have no features justifying their use at current commercial prices. 14.4.2 Poly(viny1 acetal) Poly(viny1 acetal) itself is now of little commercial importance. The material may be injection moulded but has no particular properties which merit its use. It is occasionally used in conjunction with nitrocellulose in lacquers, as a vehicle for wash primers and as a stiffener for fabrics. 14.4.3 Poly(viny1 butyral) As a safety glass interleaver, poly(viny1 butyral) (Butacite, Saflex) is extensively used because of its high adhesion to glass, toughness, light stability, clarity and moisture insensitivity. It also finds miscellaneous applications in textile and metal coatings and in adhesive formulations. Where it is to be used as a safety glass interleaver, a very pure product is required and this is most conveniently prepared from 394 poly(viny1 alcohol) rather than by the direct process from poly(viny1 acetate). In a typical process 140 parts of fully ‘hydrolysed’ poly(viny1 alcohol) are suspended in 800 parts of ethanol; 80 parts of butyraldehyde and 8 parts of sulphuric acid are added and the reaction is carried out at about 80°C for 5-6 hours. The solution of poly(viny1 butyral) is diluted with methanol and the polymer precipitated by the addition of water during vigorous agitation. The polymer is then stabilised, washed and dried. Highly ‘hydrolysed’ poly(viny1 alcohol) is normally used as a starting point. For safety glass applications about 25% of the hydroxyl groups are left unreacted. In this application the polymer is plasticised with an ester such as dibutyl sebacate or triethylene glycol di-2-ethyl butyrate, about 30 parts of plasticiser being used per 100 parts of polymer. The compound is then calendered to a thickness of 0.015 in and coated with a layer of sodium bicarbonate to prevent blocking. To produce safety glass the film is washed and dried and then placed between two pieces of glass which are then subjected to mild heat and pressure. Bulletproof glass is made by laminating together several layers of glass and poly(viny1 butyral) film. Laminated safety glass has now become standard for automobile wind- screens and is used for aircraft glazing. Poly(viny1 acetate) and its Derivatives 14.5 ETHYLENE-VINYL ALCOHOL COPOLYMERS If ethylene is copolymerised with vinyl acetate, and the vinyl acetate component ‘hydrolysed’ to vinyl alcohol, a material is produced which is in effect a copolymer of ethylene and vinyl alcohol. The material is produced by Kurardy and Nippon Gohsei in Japan and was also produced up until 1993 by Du Pont. Global nameplate capacity has increased from about 30 000 t.p.a. early in the 1990s to 60 000 t.p.a. at the end of the millenium. The material is commonly referred to in the abbreviated form EVOH but occasionally also as EVAL and EVOL. Certain copolymers of this type have been found to have excellent gas barrier properties, with the dry polymer having an oxygen permeability only about 1 /I 0th that of polyvinylidene chloride. Unsurprisingly, the copolymer has a high moisture absorption and a high moisture vapour transmission rate. Where the material is swollen by water, gas permeability is also higher. For reasons explained below, the effect of increasing the ‘vinyl alcohol’ content in EVOH is quite different to that of increasing the vinyl acetate content in EVA. In the case of ethylene-vinyl acetate (EVA) copolymers, increasing the vinyl acetate content up to about 50% makes the materials less crystalline and progressively more flexible and then rubbery. In the range 40-70% vinyl acetate content the materials are amorphous and rubbery, whilst above 70% the copolymers become increasingly rigid and brittle. Commerical grades of EVOH typically have ‘vinyl alcohol’ contents in the range 56-71%, but in contrast to the corresponding EVA materials these copolymers are crystalline. Furthermore, an increase in the ‘vinyl alcohol’ content results in an increase in such properties as crystalline melting point, tensile strength and tensile modulus together with a decrease in oxygen permeability. This is a reflection of the fact that the ethylene and vinyl alcohol units in the chain are essentially isomorphous (see Sections 4.4 and 14.3.1). Poly(viny1 cinnamate) 395 Table 14.2 Typical properties of EVOH copolymers (For purposes of comparison the grades selected all have a MFI (2.16kg, 190OC) of 1.7-1.8. Grades with other MFI values are also available) Specific gravity r, (by DW ("C) Tg (by DSC) ("C) Tensile strength (MPa) Elongation at break (%) Tensile modulus (MPa) Oxygen permeability cc.20 p/m2 0% RH, 20°C 25% RH, 25°C 24 h atm. I Ethylene content (mole %) 1.21 188 62 96 75-150 3900 0.23 0.8 100-200 3700 0.30 1.17 173 58 75 >180 3100 0.53 1.4 1.14 164 55 62 >280 2700 1.20 2.6 Some typical properties of some commercial EVOH polymers (Soamol- Nippon Gohsei) are given in Table 14.2. As is to be expected, the table shows that as the humidity is increased, causing swelling and an increase in the interchain separation, so the oxygen permeability increases. Also, as expected, the percentage increase is greater the higher the vinyl alcohol content. Because of the excellent gas barrier properties, EVOH is of interest as a packaging material. However, because of its high water absorption it is usually used as an internal layer in a co-extruded film, sheet, bottle or tube. For example, the system HDPE-EVOH-EVA may be used as a barrier film for packaging cereals, and the system polystyrene-EVOH-polystyrene for packag- ing coffee and cream, whilst the system polystyrene-EVOH-polyethylene has the additional advantage of heat sealability. In the case of EVOH being used as an interlayer with polyethylene or polystyrene, it is necessary to use additional adhesive layers such as an ethylene-vinyl acetate-maleic anhydride terpolymer (e.g. Orevac- Atochem). While EVOH is of interest primarily for food packaging applications attention is now being turned to non-food outlets such as automotive fuel tanks, floor heating pipes and toothpaste tubes. 14.6 POLY(V1NYL CINNAMATE) Poly(viny1 cinnamate) is not used in the traditional areas of plastics technology but its ability to cross-link on exposure to light has led to important applications in photography, lithography and related fields as a photoresist. The concept of a Photoresist is of great antiquity and has a number of features of interest relating to plastics. In Ancient Egypt mummies were wrappted in linen cloths dipped in a solution of oil of lavender containing high molecular mass bituminous material (Chapter 30) which was known variously as Syrian Asphalt or Bitumen of Judea. On exposure to light the product hardened and became insoluble. The evidence is that some form of cross-linking occurred. 396 Poly(viny1 acetate) and its Derivatives At the beginning of the nineteenth century, an amateur Egyptologist, J. Nictphore Niepce, became interested in the process and in 1822 he adapted it to produce the first permanent photograph. It also played an important role in the development of lithography. In essence surfaces exposed to light become insoluble and cannot be removed by solvents whilst unexposed surfaces remain soluble and can be so removed. This is the concept of a negative photoresist. (There also exist positive photoresists, including some phenolic resins, which become more soluble on exposure to light). Today photoresists are used in the fabrication of solid-state electronic components and integrated circuits and poly(vin1y cinnamate) is one of the longest established materials of this type. As with poly(viny1 alcohol), poly(viny1 cinnamate) is prepared by chemical modification of another polymer rather than from ‘monomer’. One process is to treat poly(viny1 alcohol) with cinnamoyl chloride and pyridine but this is rather slow. Use of the Schotten Baumann reaction will, however, allow esterification to proceed at a reasonable rate. In one example4 poly(viny1 alcohol) of degree of polymerisation 1400 and degree of saponification of 95% was dissolved in water. To this was added a concentrated potassium hydroxide solution and then cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl alcohol-vinyl cinnamate copolymer Figure 14.8) +CH2 - CH-ft CH,- CH j +CH2- CH-ftCH,- CH+ I I I I OH OH OH 0 I Unchanged co - Vinyl I + KCI + H,O CH II + KOH Alcohol Units + @-CH=CH.COCI Cinnamoyl Chloride Figure 14.8 To make a photoresist poly(viny1 cinnamate), or a high vinyl cinnamate copolymer, is dissolved in a solvent such as methylene dichloride and the solution is coated uniformly over the substrate by a process such as spin casting. After evaporation of the solvent a masking material (which in the case of a simple demonstration could be a paper clip) is placed on the resist and the assembly is exposed to ultraviolet light. The exposed surfaces are then insolubilised. After exposure the mask is removed and soluble matter dissolved in a solvent such as cellosolve acetate and this exposes the substrate in the shape of the mask. This may then be etched or otherwise treated as required. By the use of appropriate sensitisers such as, 1,2-benzanthraquinone or Michler ’s ketone the cross-linking may be brought about by visible light. The cross-linking is believed to involve the production of a four-membered cyclobutane ring (Figure 14.9). Figure 14.9 [...]... Moulding composition? - - - D .79 2 D.6 38 -106 1.19 -60 000 1. 18 10.5 (72 .5) -350 (2400) - 18 10' Ibf/in2 MPa lo3Ibf/in' MPa Io" Ibf/in2 MPa lo3Ibf/in* MPa - - D . 78 5 -430 (3000) -20 (140) -400 ( 275 0) M.lOO % D. 570 0.2 ft Ibf in-' (B.S.) 2 78 2 - - D.6 48 am 0.3 1. 17 -400 ( 275 0) - 18 (130) - 0.25 0.40 100 109-112 85 -95 1.49 >loL6 1.49 >io 17 3 O 3.1 OC "C - -400 ( 275 0) MI03 2-3 Copolymer$ 80 1.49 - Diakon M (ICI)... alcohol to methacrylic acid, which is then separated and esterified Figure 1 5 5 ~ ) Poly(methy1 methacrylate) 401 CH, I CH,=C CH, + ROH- I CH,=C COOH I I + H,O COOR (a) (Japan Koka 74 1 174 25, 77 95609, 79 3000 08, 78 10 988 9, USP 3 9 28 462) CH3 CH, - C=CH, I Nitrogen * Oxides I CH3- C-COOH I -H,O CH3 I CH,=C-COOH OH CH3 CH OH I 3CH=C I COOCH, (b) Figure 15.5 This process appears to be very similar to the process... Wiley-Interscience, New York f (1 971 ) KAINER, F., LEONARD, E Polyvinyl Acetate WHEELER, o.L., LAVIN E., and CROZIER, R.N., J Polymer Sci., 9 1 57 (1952) Polyvinyl Alcohol Brit Plastics 16, 77 , 84 , 122 (1944) DAVIDSON R.L., and SITI-IG, M., Water-soluble Resins (2nd Ed.), Reinhold, New York (19 68) RNCH, C.A (Ed.), Polyvinyl alcohol: Properties and Applications, Wiley New York (1 973 ) PRITCHARD, J.c., Poly(Viny1... % “C 85 60 4500 40 3 90 80 80 5.5 3300 12 2 92 115 m m m m " N mmrnmrnm m m m m m e U 8 -u 8 c U Nitrile Resins 415 DR (Rohm and Haas) and Plex 85 35-F (Rohm GmbH) Some typical properties of these materials compared with straight PMMA and with the competitive ABS and ASA polymers (discussed in Chapter 16) are given in Table 15.3 In comparison with the styrene-based and better known ABS and ASA materials. .. prepared in 1 87 3 by Caspary and Tollens,’ and of these materials the last was observed to polymerise In 188 0 Kahlbaum2 reported the polymerisation of methyl acrylate and at approximately the same time Fittig”‘ found that methacrylic acid and some of its derivatives readily polymerised In 1901 Otto Rohm reported on his studies of acrylic polymers for his doctoral dissertation His interest in these materials, ... J.c., Poly(Viny1 alcohol): Basic Properties and Uses, Macdonald, London (1 970 ) Properties and Applications of Polyvinyl Alcohol (SCI Monograph No 30), Society of the Chemical Industry, London (19 68) Polyvinyl Acetals PITZHUGH, A.F and LAWN, E., J Electrochem Soc., 100 (8) , 351 (1953) PLATZER N Mod Plastics, 28, 142 (1951) 15 Acrylic Plastics 15.1 INTRODUCTION Poly(methy1 methacrylate) (Figure 15.1, I) is,... other thermoplastics used for packaging Table 15.4 Permeability ( P ) of nitrile resins compared with other polymers Polymer I O2 I Poly( acrylonitrile) Nitrile resins Poly(viny1idene chloride) Poly(viny1 chloride) High-density polyethylene 0.14 2.3-3.6 3.6 23-32 900 0.23 4.5-9 14-23 40-1 80 2000 In the mid-1 970 s many major plastics materials producers marketed or were actively developing materials of... Union Carbide and Vistron (Sohio) The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73 -77 parts acrylonitrile and 23- 27 parts by weight of methyl acrylate in the presence of a 8- 10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber)... copolymer of 28- 34 parts styrene and 66 -72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile This polymer contained no rubbery component The main interest in these materials lay in their potential as beverage containers although other suggested uses included such, presumably, diverse materials as barbecue sauces, pesticides and embalming fluids However, in 1 977 the US Food... other major thermoplastics For example, UK production in 1950 was about the same as that for polystyrene, in 1965 (when the first edition of this book was being completed) it was about 40% and by the end of the 1 970 s it was down to about 10%.There was, however, an upsurge in the late 1 980 s and early 1990s and world production capacity was estimated at 1 .7 X 106t.p.a in 1996 This is about 17% of the capacity . Ethylene content (mole %) 1.21 188 62 96 75 -150 3900 0.23 0 .8 100-200 370 0 0.30 1. 17 173 58 75 > 180 3100 0.53 1.4 1.14 164 55 62 > 280 270 0 1.20 2.6 Some typical properties. I I CH, CH,=C + ROH- CH,=C + H,O COOH COOR (a) (Japan Koka 74 1 174 25, 77 95609, 79 3000 08, 78 10 988 9, USP 3 9 28 462) CH3 I CH3 Nitrogen I -H,O CH, - C=CH, * CH3- C-COOH CH,=C-COOH. -60 000 1. 18 10.5 (72 .5) -350 (2400) - 18 -400 ( 275 0) MI03 - 2-3 0.3 0.40 109-112 85 -95 1.49 >io 17 3.1 Copolymer$ - 1. 17 - -400 ( 275 0) - 18 (130) - 0.25 80 1.49 -