Plasticizers in Various Processing Methods

George Wypych ChemTec Laboratories, Inc., Toronto, Canada 

The following aspects of plasticizer incorporation are analyzed in this chapter  

These influences of plasticizers are important determinants of process design and they are discussed within the framework of the existing information and data. 

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Processing is the final step that converts the compounded material into a useful plastic product. Basically, the compounded resin needs to be melted into a liquid and heated to a temperature that allows easy handling of the fluidized plastic or the melt. This melt is fed into molds or dies to force the material into required shapes and quickly cooled to obtain the product. Usually, some minor finishing is needed before the product is made available to the consumer. The different processes used and the equipment employed are determined by the type of product being manufactured. A detailed discussion of the various processing techniques available for common thermoplastics is beyond the scope of this discussion. However, the basic principals involved in common processing methods associated with high-volume products will be discussed briefly below. 

Charcoal, A black amorphous substance a form of carbon derived from the incomplete combustion of animal or vegetable matter (Ref 2). When a pure form of charcoal is desired, it is derived from sugar. Its method of prepn by calcination of sugar heated to ca 800° is described in Ref 3 This method is considered superior to the treatment of sugar with coned HjSO. Toxicity, fire Sc expl hazards of charcoal are discussed in Ref.4 Charcoal is used in various chem processes, as a decolorizing Sc filtering medium, as absorbent, in pharmaceutical prepns Sc plastics and as a component of propellants, BkPdr, pyrotechnics Sc of other expls(Refs 1 5). Charcoals used by the US Armed Forces must comply with die applicable specifications (Ref 6)... 

Polymeric chips have been fabricated with various methods, as developed from the plastics industry. These processes include casting, injection molding, laser ablation, imprinting, and compression molding. The physiochemical properties of various polymeric materials and their molding methods have been summarized in a recent review article [7],... 

Standard analyses are described in ASTM and Bureau of Mines publications, but nonstandard methods must be acquired from publications dealing with the specific area of interest. For example, the plastic properties of coal, which are important considerations in many process designs, can be characterized by various techniques, each having its own advantages and disadvantages (Table 19.4). 

Foamed plastics can be prepared by various methods. The most widely used, called the dispersion process, involves the dispersion of a gaseous phase throughout a fluid polymer phase, and the preservation of the resultant state. Other methods of producing cellular plastics include leaching out solid or liquid materials dispersed in the plastic, sintering small dispersed particles, and dispersing small cellular particles in the plastic. The latter processes are relatively straightforward techniques of lesser commercial importance. 

It has been shown that fracture is a very complex process and the fracture performance depends on both the initiation and the propagation of a defect [6-10] in the material. Under impact, most polymers break in very distinct manners. Several types of fracture have been identified depending on the amount of plastic deformation at the crack tip and the stability of crack propagation. For each type, an appropriate analysis has been developed to determine the impact fracture energy of the material. These methods have also been verified in various plastics [11,12]. The different fracture behaviors in most polymers are illustrated in Figure 27.1, which shows a schematic drawing of the load-deflection diagram of Charpy tests on HIPS [13] under an impact velocity of 2 m/s at various temperatures. 

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