Plasticiser-polymer ratio

In the early days of the commercial development of PVC, emulsion polymers were preferred for general purpose applications. This was because these materials exist in the form of the fine primary particles of diameter of the order of 0.1-1.0 p,m, which in the case of some commercial grades aggregate into hollow secondary particles or cenospheres with diameters of 30-100 p,m. These emulsion polymer particles have a high surface/volume ratio and fluxing and gelation with plasticisers is rapid. The use of such polymers was, however, restricted because of the presence of large quantities of soaps and other additives necessary to emulsion polymerisation which adversely affect clarity and electrical insulation properties. 

Early suspension polymers, although less contaminated, were supplied as more or less spherical particles with a diameter in the range 50-100 p,m. Such materials had a much lower surface/volume ratio than the emulsion polymers and, being of low porosity, the materials were much slower in their gelation with plasticisers. The obvious requirement was to produce more porous particles and these became available about 1950 as easy-processing resins. 

If PVC polymer particles are mixed, at room temperature, with plasticisers the immediate product may take one of two forms. If there is insufficient plasticiser to fill all the gaps between the particle a mush will be produced. If all the voids are filled then the particles will become suspended in the plasticiser and a paste will be formed. In the case of conventional granular polymer, or with emulsion polymer cenospheres, the particles are too large to remain in suspension and will settle out. Therefore compounds used in paste-processes must use polymers with a small particle size. On the other hand there is a lower limit to this, since small particles will have a very high surface/volume ratio and measurable plasticiser absorption will occur at room temperature to give a paste whose viscosity will increase unduly with time. As a consequence paste polymers have an average particle size of about 0.2-1.5 ptm. 

It is found that the viscosity of a paste made from a fixed polymer/plasticiser ratio depends to a great extent on the particle size and size distribution. In essence, in order to obtain a low-viscosity paste, the less the amount of plasticiser required to fill the voids between particles the better. Any additional plasticiser present is then available to act as a lubricant for the particles, facilitating their general mobility in suspension. Thus in general a paste polymer in which the pastes have a wide particle size distribution (but within the limit set by problems of plasticiser absorption and settling out, so that particles pack efficiently, will... 

As the majority of stabilisers has the structure of aromatics, which are UV-active and show a distinct UV spectrum, UV spectrophotometry is a very efficient analytical method for qualitative and quantitative analysis of stabilisers and similar substances in polymers. For UV absorbers, UV detection (before and after chromatographic separation) is an appropriate analytical tool. Haslam et al. [30] have used UV spectroscopy for the quantitative determination of UVAs (methyl salicylate, phenyl salicylate, DHB, stilbene and resorcinol monobenzoate) and plasticisers (DBP) in PMMA and methyl methacrylate-ethyl acrylate copolymers. From the intensity ratio... 

Whereas the use of conventional fast atom bombardment (FAB) in the analysis of polymer/additive extracts has been reported (see Section 6.2.4), the need for a glycerol (or other polar) matrix might render FAB-MS analysis of a dissolved polymer/additive system rather unattractive (high chemical background, high level of matrix-, solvent- and polymer-related ions, complicated spectra). Yet, in selected cases the method has proved quite successful. Lay and Miller [53] have developed an alternative method to the use of sample extraction, cleanup, followed by GC in the quantitative analysis of PVC/DEHP with plasticiser levels as typically found in consumer products (ca. 30 %). The method relied on addition of the internal standard didecylphthalate (DDP) to a THF solution of the PVC sample with FAB-MS quantitation based on the relative signal levels of the [MH]+ ions of DEHP and DDP obtained from full-scan spectra, and on the use of a calibration curve (intensity ratio m/z 391/447 vs. mg DEHP/mg DDP). No FAB-matrix was added. No ions associated with the bulk of the PVC polymer were observed. It was... 

Automatic polymer waste sorting plants based on NIR identification are operative (c/r. Chp. 1.2.2). For identification and sorting of carpets a portable NIR spectroscopic system - CarPID - was developed [139]. Other reported NIRS applications are to be found in the quantitative analysis of copolymers or blends the near-IR range allows for accurately monitoring of the monomer ratio and residual monomer content. Ikeda [140] used near-IR spec-trochemical analysis in controlled manufacture of polyester plasticisers. Jones et al. [141] similarly described the use of NIR analysis for controlling plasticiser ester formation the esterification of phthalic anhydride by isodecyl alcohol was exemplified. 

All studies discussed in this chapter deal with thermoplastic starch (TPS) which is manufactured through destructurisation in presence of specific amounts of plasticisers and under certain extrusion conditions. Depending on the type of application either pure starch polymers or various types of blends with different ratios of petrochemical copolymers are used. 

The GPE was composed of a PEG-based acrylate macromonomer, photoinitiator, plasticiser, glass beads and the electrolyte to compensate for the charge injected into or extracted from the conducting polymer. The ionic conductivity of lithium-PEO has been reported to be at a maximum for a Li/O ratio of 0.04 and hence the composition of the GPE with no plasticiser was prepared with this ratio. The different compositions of the GPEs used in this study are shown in Table 12.1. 

The star network polymer was dissolved adequately in acetonitrile, then LiC104 and plasticisers of EC/PC (mass ratio = 1 1) were added to the polymeric solution and stirred vigorously at 40 °C. The acetonitrile was driven out finally under vacuum at 60°C.The resulting polymer electrolytes were stored in a nitrogen-filled drybox. 

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