Subject Plastisols

Closed-cell foams result when the decomposition and gelation are carried out in a closed mold almost filled with plastisol. After the heating cycle, the material is cooled in the mold under pressure until it is dimensionally stable. The mold is then opened, and the free article is again subjected to heat (below the previous molding temperature) for final expansion. Protective padding, life jackets, buoys, and floats are some items made by this process. 

Selection of plasticizer or plasticizing system goes beyond lowering the viscosity. The amount of form coating, its nniformity, and appearance depend on rheological properties of plastisols. Forms are subjected to a controlled movement which has several steps ... 

Deaerate de- ar- at (1791) vt. To remove air from a substance. Deaeration is an important step in the production of vinyl plastisols and most casting operations accomplished by subjecting the liquid to a moderate vacuum with or without agitation, to remove air that would cause objectionable bubbles or blisters in finished products. 

The main uses of montmorillonite stem from its characteristic expansion, and it is used to control viscosity or impart thixotropy to a variety of liquid polymers based on unsaturated polyesters, PVC plastisols, polysulfides, alkyds, etc. It has also been reported to control the melt rheology of thermoplastics and to reinforce polyamides. There has, over the last few years, been enormous industrial and research interest, with many papers and patents, published on montmorillonite, especially as an organoclay as the basis of polymer nanocomposites. Because of the delamination process described above plastic-organoclay nanocomposites have been reported to have very high rigidity, low permeability to fluids, and fire resistance. This subject is covered in more detail in Chapter 10. 

Ba/Cd stabilisers are fatty acid soaps and the choice of organic acid (lauric, stearic, ricinoleic, etc) is critical in calendering application to minimise the risk of plate-out. Ba/Cd and Ba/Cd/Zn stabilisers are often sold as a tailor-made complex package for a particular application, and may contain antioxidants such as diphenylol propane, phosphite chelators and other ingredients in addition to the metal soaps. Usual levels of addition are 1-3 phr, the lower levels being used in certain plastisols subject to fairly mild curing conditions. 

Plasticization occurs as a result of the action of plasticizer on PVC. The physical properties of PVC gradually changes from a rigid solid to a soft gel or viscous liquid. The action of plasticizer on PVC is a complex phenomena and involves many interactions. Four principal theories have been proposed to account for the main effects plasticizers produce. These are lubricity, gel, mechanistic and free volume theories (22). For more detailed theories the reader is referred to several textbooks which cover the subject in more detail (23-25). Plasticization occurs in a number of steps. The steps of plasticization may not occur for every polymer-plasticizer combination but various steps of plasticization for two main PVC applications, namely plastisol and dry blending are shown in Figure 1. 

VINYZENE BP-5-2 MEK and BP-5-2 MS are recommended for organosols, plastisols, solvent solution coatings, adhesives and sealants. Plastic compounds protected with BP-5-2 MEK and BP-5-2 MS include coatings for fabrics metal and wood automotive and construction sealants adhesives and other products subject to microbiological deterioration. 

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