Plastisol variations

Ref 7 reviews the characteristics and manuf of PVC plastisol proplnts. Information is given on compn, uncured proplnt flow, curing time, variation of physical properties with temp of... 

For the relative viscosity of emulsions, in the absence of deformation and coalescence, Eqs 7.24-7.30 may also be used, provided that the intrinsic viscosity is calculated from Eq 7.50 and that the maximum packing volume fraction is treated as an adjustable parameter, dependent on the interphase. This pragmatic approach has been successfully used to describe [r]] vs. (() variation for such complex systems as industrial lattices (at various stages of conversion), plastisols and organosols. 

Three important variations of the plastisol casting, are dip casting, slush casting, and rotational... 

The relationships between Pr and cj) have been derived for suspensions of monodispersed hard spheres in Newtonian liquids. However, most real systems are polydispersed in size and do not necessarily consist of spherical particles. It has been found that here also Simha s Eq. 7.24, Mooney s Eq. 7.28, or Krieger-Dougherty s Eq. 7.8 are useful, provided that the intrinsic viscosity and the maximum packing volume fraction are defined as functions of particle shape and size polydispersity. For example, by allowing with composition, it was possible to describe the Pr versus cj) variation for bimodal suspensions (Chang and Powell 1994). Similarly, after values of [q] and (j)i were experimentally determined, Eq. 7.24 provided good description for the versus cj) dependence of several multiphase systems, e.g., PVC emulsions and plastisols, mica-reinforced polyolefins, and sealant formulations (Utracki 1988, 1989). 

PlaStiSOlS. Plastisol-forming pol5rmers are produced by microsuspension polymerization or dispersion polymerization (9). Microsuspension produces very fine particles of monomer to ensure that small particle sizes of polymer are produced. In emulsion or dispersion polymerization the vinyl chloride is dispersed in a water-soluble initiator the vinyl chloride particles are small and stabilized using surfactants. There are also several variations of these two basic techniques. 

In a variation of emulsion polymerisation, the process can be operated continuously, in which fresh VCM, emulsifiers and an initiator are fed into the reactor and PVC latex is withdrawn continuously. Such processes tend to require greater quantities of emulsifiers than the batch process. They produce latexes with a wide particle size distribution and thus low plastisol viscosities suitable for a wide range of applications, but the higher levels of emulsifier will preclude them from applications where water absorption or clarity of the final coating is important. 

Slush molding is a mnq>le variation of the casting process. The low-viscosity material, such as, plastisol is poured into a hot mold and after a thick casting is formed on the wall of the mold cavity, the excess material is poured out. In order to ensure uniform coating, the mold is often rotated. 

Structural adhesives, for the present purposes, may be defined as those which transmit significant mechanical loads. They are typically thermosetting and are generally epoxies, phenolics, polyurethanes, polyesters, or some variation thereof, although certain plastisols are an important exception. 

Epoxidized tall oil esters (EPT) can be compatibihzed with some overbased liquid stabilizers to form convenient blends. Epoxidized mixed (mainly octyl) alkyl esters of tall oil (mainly oleic and linoleic acids) are useful in lowering plastisol viscosity as compared with ESO or ELO. This results from their lower oxirane content (4-5 percent). They are mobile, more or less colorless liquids, SpG 0.92, with a flash point of 220-230 °C. Trade names include Drapex 4.4, Flexol EP-8, PlasthaU S-73, and Vikoflex 4050. Because of being mostly monofunctional in oxirane, heat and light aging of the pure epoxide is considerably better than with ESO or ELO. Because of variation in the alcohol used to form the ester, these products are listed under CAS 61789-01-3 (PlasthaU S-73 and Drapex 4.4) and 68082-34-8... 

Both cold- and hot-dipped parts are fused as with powder coatings. There is much variation in industrial practice regarding plastisol fusion cycles. Glass bottles coated... 

Slush molding of plastisols is primarily used to produce rainboots and overshoes, and secondarily for toy and doU parts, and for automotive interior skin coats. The secondary uses are popular where circumstances such as short mns of many variations militate against rotational molding. The molds, typically low-cost aluminum, are preheated to a temperature at which the plastisol will gel rapidly, then filled with plastisol. After a brief gelation time, the molds are emptied of excess plastisol and placed in a fusion oven, then cooled to permit demolding. 

A second variation of commercial importance is the in-place plastisol molding of automotive air filter components. Here, the paper air filter and supporting stmcturcs are placed in a ring mold (on one side of the assembly), and plastisol is added and fused. After demolding, the other side of the assembly is placed in the ring mold and similarly attached. With design ingenuity, the process mns semi-automaticaUy. 

In an interesting variation, plastisol can be injected into a closed mold with a positive displacement pump operating under low pressure. The mold(s) may then be placed in an oven, or may already be in a compression press equipped for heating and cooling. The major articles so manufactured are shoe soles, where the process competes with injection molding from pelletized compound. 

Wire dish drainers, coat hangers, and other industrial and household metal items can be coated with a thick layer of flexible vinyl plastic by the simple process of dipping and fusion. A more elaborate artifact is a plastic glove, which could be produced either by dipping a hand-shaped mandrel or by slush molding in a hoUow mold for the same shape. Several variations of plastisols have been developed to alter the properties of the liquid as well as the final solid. 

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