Poly extraction resistance

Poly(vinyl chloride) has a good resistance to hydrocarbons but some plasticisers, particularly the less polar ones such as dibutyl sebacate, are extracted by materials such as iso-octane. The polymer is also resistant to most aqueous solutions, including those of alkalis and dilute mineral acids. Below the second order transition temperature, poly(vinyl chloride) compounds are reasonably good electrical insulators over a wide range of frequencies but above the second order transition temperature their value as an insulator is limited to low-frequency applications. The more plasticiser present, the lower the volume resistivity. 

Low molecular weight liquid polyester resins are useful as plasticisers, particularly for PVC, where they are less volatile and have greater resistance to extraction by water than monomeric plasticisers. Examples of such plasticisers are polyfpropylene adipate) and poly(propylene sebacate). In some cases monobasic acids such as lauric acid are used to control the molecular weight. 

A mixture of powdered poly(vinyl chloride), cyclohexanone as solvent, silica, and water is extruded and rolled in a calender into a profiled separator material. The solvent is extracted by hot water, which is evaporated in an oven, and a semiflexible, microporous sheet of very high porosity ( 70 percent) is formed [19]. Further developments up to the 75 percent porosity have been reported [85,86], but these materials suffer increasingly from brittleness. The high porosity results in excellent values for acid displacement and electrical resistance. For profiles, the usual vertical or diagonal ribs on the positive side, and as an option low ribs on the negative side, are available [86],... 

Cobalt(II) chloride was dissolved in poly(amide acid)/ N,N-dimethylacetamide solutions. Solvent cast films were prepared and subsequently dried and cured in static air, forced air or inert gas ovens with controlled humidity. The resulting structures contain a near surface gradient of cobalt oxide and also residual cobalt(II) chloride dispersed throughout the bul)c of the film. Two properties of these films, surface resistivity and bullc thermal stability, are substantially reduced compared with the nonmodified condensation polyimide films. In an attempt to recover the high thermal stability characteristic of polyimide films but retain the decreased surface resistivity solvent extraction of the thermally imidized films has been pursued. 

This indicates that polymeric stabilizers having M > 800 have high resistance against extraction by components of foods, and, moreover, they do not enter into the metabolic cycle. Public concern over the contamination of the human environment can be thus satisfied. As a consequence, stabilizers like Poly AO-79 (97), Chimassorb 944 (161a) or Tinuvin 622 (146) may be legally used in stabilization of polymers in contact with food. Possibilities for application of other polymeric stabilizers for articles used in the home are open. Extractability problems may be thus overcome. Articles made from weather resistant butadiene based multiphase systems like ABS, MBS or MABS [84] stabilized in the most sensitive BR phase with polymer bound stabilizers may serve as an example. 

In contrast when the cell extracts from the [ H]MTX(poly-D-lysine) experiment were applied to the Sephadex 6-75 column only the undegraded complex with Blue Dextran 200 was observed. When the experiment was repeated with the non-resistant H35 cells, similar results were obtained. 

Amylose is a polysaccharide from plant extracts and a component of starch. It consists of D-glucopyranose residues linked by a(l-4) bonds. It is a poly(l,4 a-D-glucopyranose) (Figure 19.9). They have the ability to form films that are water swellable and are potentially resistant to pancreatic a-amylase [27], but... 

GeH,i B2H6, PH3) SiH4 Figure 2. Dopant concentration in poly-Si films versus dopant SiH4 volume ratio in the gas phase for (1) Ge, (2,3) B, and (4,5) P (lines 2 and 3 coincide). (2,4) data extracted from resistivity measurements, (1,3,5) SIMS results. 

The synthetic suede, Alcantara (Ultrasuede in the USA, Escaine in Japan, Australia, and South Africa), on the other hand, consists of extremely fine poly(ethylene terephthalate) fibers in a poly(styrene) matrix. These matrix-fibrillar fibers form a felt that is impregnated with polyurethanes. Finally, the poly(styrene) matrix is extracted with dimethyl formamide so that the fibrils in the system have relatively free movement. This synthetic suede is significantly lighter and more wrinkle resistant than natural suede, and in addition, it is completely washable. Table 38-7 compares the properties of some leathers. 

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