The Effect of Plasticisers

Plasticisers are substances with relative molar masses well below those of polymers, usually liquids that, when added to polymers, give apparently 

The main mode of action of plasticisers appears to be to act as spacers at the molecular level. Hence less energy is required to free the molecules sufficiently to allow substantial rotation about the C—C bonds thus is lowered. So, too, is the temperature at which the polymer begins to flow. 

---

Many other liquids have been found to be effective plasticisers for PVC but are of limited commercial value, at least in Britain. The effect of plasticisers on the properties of PVC is illustrated in Figure 12.20 (a-e). 

Felton LA, McGinity JW. Influence of plasticisers on the adhesive properties of an acrylic resin copolymer to hydrophilic and hydrophobic tablet compacts. Int J Pharm 1997 154(2) 167—178. Okarter TU, Singla K. The effects of plasticisers on the release of metoprolol tartrate from granules coated with a polymethacrylate film. Drug Dev Ind Pharm 2000 26(3) 323—329. 

A plasticiser is a material incorporated in a plastic to increase its workability and flexibility or distensibility. The melt viscosity, elastic modulus and Tg of a plastic are lowered by a plasticiser addition. There are several theories to explain plasticiser effects such as the lubricity, gel, and free volume. Plasticisers are essentially nonvolatile solvents and therefore, polymer and plasticiser compatibility is very important and the solubility parameter difference (A8) should be less than 1.8. When present in small amounts plasticisers generally act as antiplasticisers, (i.e., they increase the hardness and decrease the elongation of polymers). Figure 6.12 illustrates the effect of plasticiser on modulus. Increasing concentration of the plasticiser shifts the transition from the high modulus (glassy) plateau region to the low, i.e., to occur at lower temperature [9]. 

THE EFFECTS OF PLASTICISERS, IMPACT MODIFYERS AND "COMPATTBIUSERS" ON PVC PERFORMANCE... 

Figure 1.11 Diagrams showing the effect of plasticiser or molecular weight on the gl lss transition temperature. Increasing molecular weight will increase 7g whereas the inclusion of plasticiser will reduce 7g.

In the present work we have found that Equation (13) adequately describes the reduction in friction of PET fibres in water and SDS/salt solutions only on the basis of the wetting characteristics of the liquid. The model can be readily extended to determine the level of boundary lubrication since the equation contains interfacial shear strength terms. In the same way it should be possible to determine the effect of plasticising substances. ... 

In summary, then, design with polymers requires special attention to time-dependent effects, large elastic deformation and the effects of temperature, even close to room temperature. Room temperature data for the generic polymers are presented in Table 21.5. As emphasised already, they are approximate, suitable only for the first step of the design project. For the next step you should consult books (see Further reading), and when the choice has narrowed to one or a few candidates, data for them should be sought from manufacturers data sheets, or from your own tests. Many polymers contain additives - plasticisers, fillers, colourants - which change the mechanical properties. Manufacturers will identify the polymers they sell, but will rarely disclose their... 

From Table 5.7 it will be seen that plasticisers for PVC such as the octyl phthalates, tritolyl phosphate and dioctyl sebacate have solubility parameters within 1 cgs unit of that of the polymer. Dimethyl phthalate and the paraffinic oils which are not PVC plasticisers fall outside the range. It will be noted that tritolyl phosphate which gels the most rapidly with PVC has the closest solubility parameter to the polymer. The sebacates which gel more slowly but give products which are flexible at lower temperatures than corresponding formulations from tritolyl phosphate have a lower solubility parameter. It is, however, likely that any difference in the effects of phthalate, phosphate and sebacate plasticisers in... 

Since the incorporation of plasticisers into a polymer compound brings about a reduction in glass temperature they will also have an effect on the electrical properties. Plasticised PVC with a glass temperature below that of the testing temperature will have a much higher dielectric constant than unplasticised PVC at the same temperature (Figure 6.6). 

For electrical insulation china clay is commonly employed whilst various calcium carbonates (whiting, ground limestone, precipitated calcium carbonate, and coated calcium carbonate) are used for general purpose work. Also occasionally employed are talc, light magnesium carbonate, barytes (barium sulphate) and the silicas and silicates. For flooring applications asbestos has been an important filler. The effect of fillers on some properties of plasticised PVC are shown in Figure 12.21 (a-d). 

Figure 12.21. Effect of filler content on the properties of plasticised PVC compounds. (a) Tensile strength, (b) BS softness number.

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. 

Figure 18.11 shows the influence of temperature on the tension modulus of nylons 66 and 6 and Figure 18.12 the effect of temperature on impact strength of nylon 66. Figure 18.13 shows the profound plasticising influence of moisture on the modulus of nylons 6 and 66, while Figure 18.14 illustrates the influence of moisture content on impact strength. 

Nitration of cellulose followed by plasticisation of the product with camphor has the effect of reducing the orderly close packing of the cellulose molecules. Hence whereas cellulose is insoluble in solvents, except in certain cases where there is chemical reaction, celluloid is soluble in solvents such as acetone and amyl acetate. In addition the camphor present may be dissolved out by chloroform and similar solvents which do not dissolve the cellulose nitrate. 

Also, as might be expected, the use of plasticiser has a similar effect to that of increasing the hydroxyvalerate content. It also has a more marked effect on depressing the glass transition temperature and therefore improves properties such as impact strength and ductility at lower temperatures. 

Brown D, Croudance CP, Williams NJ, Shearing JM, Johnson PA (1998) The effect of phthalate ester plasticisers tested as surfactant stabilized dispersions on the reproduction of the Daphnia Magna. Chemosphere 36 1367-1379... 

The enforcement in Denmark of EU Directives on food packaging materials is discussed. Enforcement activities considered include studies of total migration from food contact materials, migration from kitchen-and tableware made of melamine plastics and migration of di(2-ethylhexyl)adipate from plasticised PVC films. Activities which need to be undertaken to increase the effectiveness of enforcement activities in the field of migration are described, including development of selfinspection programmes in industry, European network of enforcement, more rapid analysis and provision of information to the consumer. 2 refs. 

By way of alternative to UBS plastisols, an underbody hard shell not only reduces the release of plasticisers during the usage phase. Due to reduced weight and reduced air resistance (CW value) fuel consumption of vehicles is also reduced, which has a positive effect as part of a life-cycle assessment. After dismantling the plastic part can be recycled separately. 

With regard to the case studies contained in the SubChem project, the effects of the different requirements placed on new substances and existing substances can best be illustrated using the case study of plasticisers for PVC (DINCH as a substitute for DEHP). 

The effects of interfacial monolayers on the extraction from drops are particularly striking. Early work showed that traces of either impurity or surface-active additives can drastically reduce extraction rates even plasticiser, in subanalytical quantities dissolved from plastic tubing by benzene, reduces the mass-transfer rate by about ten times by retarding... 

Cadogan DF, Papez M, Poppe AC, et al. 1994. An assessment of the release, occurrence and possible effects of plasticisers in the environment. Prog Rubber Plast Technol 10 1-19. 

Recent investigations covering S-PVC polymerisation are to be found in (35,166,318,345,429). Topics cover improved reactor economics, polymerisation in the presence of calcium carbonate, secondary stabilisers to impart higher grain porosity to assist in improving VCM removal and plasticiser uptake, initiator stabilisers and an investigation on the effects of polymerisation conditions on PVC particles. 

Plasticisers are added to PVC to achieve flexibility and workability. The flexibility or softness is determined by the type of plasticiser and level used in relation to the PVC (phr). They also operate as an internal lubricant between the PVC molecules. Based on organic esters, e.g., phthalates, adipates, trimellitates, phosphates, etc., addition levels can be as low as 20 phr for semi-rigid to 100 phr for very flexible applications. The effect on the thermal stability significantly depends on the physical state of the PVC-plasticiser system (260). The relative amount of crystalline PVC in PVC/diethylhexyl phthalate has been identified on the basis of a combination of carbon-13 solution and solid state nuclear magnetic resonance (NMR) (361). 

A study of the effects of several different plasticisers on the density, elasticity and degree of expansion of foams, produced from different PVC plastisols, has been reported (120). A three-dimensional and high resolution quantitative image technique has been proposed for the investigation of the internal microstructure of foams. This provides a tool to study the relationships between foam structure and physical properties (18). 

---