Plasticizers in polymers

K. L. Houghton and M. E. Moss "Chlorinated Paraffins as Plasticizers in Polymer Sealant Systems," A.SC Supplier Short Course Nashville, Term., May 14-17,1990. 

Plasticizers. Plasticizers are materials that soften and flexibilize inherently rigid, and even britde polymers. Organic esters are widely used as plasticizers in polymers (97,98). These esters include the benzoats, phthalates, terephthalates, and trimeUitates, and aUphatic dibasic acid esters. Eor example, triethylene glycol bis(2-ethylbutyrate) [95-08-9] is a plasticizer for poly(vinyl butyral) [63148-65-2] which is used in laminated safety glass (see Vinyl POLYMERS, poly(vinyl acetals)). Di(2-ethyUiexyl)phthalate [117-81-7] (DOP) is a preeminent plasticizer. Variation of acid and/or alcohol component(s) modifies the efficacy of the resultant ester as a plasticizer. In phthalate plasticizers, molecular sizes of the alcohol moiety can be varied from methyl to tridecyl to control permanence, compatibiUty, and efficiency branched (eg, 2-ethylhexyl, isodecyl) for rapid absorption and fusion linear (C6—Cll) for low temperature flexibiUty and low volatility and aromatic (benzyl) for solvating. Terephthalates are recognized for their migration resistance, and trimeUitates for their low volatility in plasticizer appHcations. 

Organophosphate triesters (OPERs) are used as flame retardants and/or plasticizers in a wide range of polymers, in furniture upholstery, insulation, wall coverings, and floor finishing products. Triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), tri-iso-butyl phosphate (T/BP), tris(2-ethylhexyl) phosphate (TEHP), and tris(2-butoxyethyl) phosphate (TBEP) are commonly used as plasticizers in polymers,... 

In his chapter, Mobility of Plasticizers in Polymers, R. Kosfeld describes his recent finding that a portion of a liquid plasticizer remains in the liquid-like state in the plasticized resin even below its glass transition temperature. 

In the manufacture of unsaturated polyester resins the polyester is synthesized and then diluted with a vinyl reactive monomer such as styrene (see POLYESTERS, UNSATURATED). A portion of the dibasic acid of the polyester is maleic or some other vinyl reactive diacid that can be polymerized with the styrene to yield a highly cross-linked, high performance polymer system. Other esters made with propylene glycol, dipropylene glycol, and tripropylene glycol are used as emulsifiers in foods, as plasticizers in polymer systems, and as part of acrylate resin systems. 

Y. Tateoka, T. Sagawa, and M. Kawasaki, Photochromic materials containing photochromic substance and plasticizer in polymer matrix for quick response, Jap. Pat. Appl. JP 6327,837A to Nissan Motor and Unitika (1988). 

The author is well aware of the fact that many aspects which have been treated in the extensive literature on extrinsic crazing have not been considered in this article and that more information is needed for a comprehensive account of the observed craze phenomenon. For instance the recent work on the intrinsic crazing of PC and on related phenomena which has been re wed here has primarily been based on structural considerations. It is believed that future work on the kinetics of craze formation and on the underlying molecular dynamics of the system may contribute considerably to a more detailed account of this phenomenon. Nevertheless, it is hoped that this work has opened up some new paths which may lead to a better understanding of the phenomenon of cavitational plasticity in polymers. 

Kambour, R. P., Robertson, R. E. The mechanical properties of plastics, in Polymer Science, (ed. Jenkins, A. D.), Amsterdam—London, North-Holland Publ. Co. 1972, p. 687... 

Some results, which were considered supporting the lubricity theory, were also found Verhoek, who measured vapor pressures of plasticizers in polymers, found that plasticizers reduce solvent retention, which was considered to support these theories (plasticizers fill voids and so they exclude solvents). Rententivity and permeability of cellulose acetate plasticized with different sulfonamides, phthalates and phosphates, were measured by Kirkpatrick who concluded that these properties depended on the attractive forces resulting between the plasticizer and the polymer. Houwink measured swelling of some butadiene-acrylonitrile copolymers with different acrylonitrile content when these were mixed with solvents of different polarities, and proved the importance of the polarity of the plasticizer and the polymer. Moreover, Houwink measured the brittle point of ethyl... 

This behavior can be expected from systems in which entropic factors can be neglected. ABS/PMMA blend plasticized with a mixtme of ethylene and propylene carbonates is an example of system where entropic factors play a role. PMMA is plasticized in polymer electrolytes to increase ionic conductivity. Addition of a plasticizer in an amount sufficient to achieve required conductivity decreases the mechanical performance of the gel to the level that it needs to be reinforced. ABS is added as reinforcing polymer and sufficient mechanical properties are obtained. Two phases are obtained plasticizer-reach phase giving pathway for ion transportation and ABS-rich phase which acts as a matrix increasing mechanical performance. ABS is miscible with PMMA forming transparent blends if no plasticizer is added. Addition of the plasticizer results in phase separation (opaque materials) because of incompatibility between ABS and the plasticizer. This is an example of a system in which the plasticizer is not uniformly distributed among participating polymers but the plasticizer is found in the PMMA-rich phase. ... 

The large strain response in the glassy or semicrystalline state is that of a nonlinear viscoelastic solid. However, both engineering and theoretical approaches to plasticity in polymers have largely developed as an independent discipline, in which (Ty plays a central role, in spite of its somewhat arbitrary definition (indeed it is not always possible to associate cty with a maximum in the force-deformation curve [5]). This is because in practice the yield point, rather than the ultimate strength, is usually considered to be the failure criterion for ductile materials. 

As LB. Rabinovich and his research team noted [2-5, 73], in the samples of polymer mixtures with plasticizers containing an excess of a low-molecular component over its solubility in the polymer the amoimt of the surplus plasticizer can be so large that its formed crystals will reinforce the saturated solution of the plasticizer in polymer thus preventing it from devitrification. In this case devitrification of the saturated solution will take place in the temperature range of the plasticizer surplus pre-melting phase. The ehitin-water sample containing 89,6 mass% of H2O (Figure 18) [4, 5, 72, 73] can serve as an example. 

Due to their volatility the esters used as plasticizers in polymers such as flexible PVC can be determined by gas chromatographic analysis of a solvent extract of the polymer. Most published me ods of analysis are based on this technique and this is the favoured technique for determining such substances (see Table 1.10)... 

From R. P. Kambour and R. E. Robertson, The Mechanical Properties of Plastics, in Polymer Science, A Materials Science Handbook, A. D. Jenkins, Editor. Reprinted with permission of Elsevier Science Publishers.)... 

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