Plastics primary processing

These are the primary process interactions that the designer must be aware of in order to determine process interference in product performance and design. Specific materials may introduce other problem areas as, for example, air entrapment, differential expansion, and the problem of a level of crystallinity in a crystalline plastic that exceeds the allowed level for stability of a product. 

Electrophysiologic and behavioral observations in LSD-treated animals may give some hint as to the switch in attentiveness in the presence of a moderately high state of arousal, which is characteristic of LSD in man. One would expect further clarification of the physiologic role of the raphe with respect to REM sleep because, in nature, this is one state in which a natural shift to primary process thinking and plastic and sensory thought and perceptual processes (with a compelling sense of conviction) can occur. 

Figure 41 Primary process of plastic granules at company C.

Mutual miscibility between plasticizers and polymers is an important criterion from a practical point of view. If a polymer is soluble in a plasticizer at a high concentration of the polymer, the plasticizer is said to be a primary plasticizer. Primary plasticizers should gel the polymer rapidly in the normal processing temperature range and should not exude from the plasticized material. Secondary plasticizers, on the other hand, have lower gelation capacity and limited compatibility with the polymer. In this case, two phases are present after plasticization process—one phase where the polymer is only slightly plasticized, and one phase where it is completely plasticized. Polymers plasticized with secondary plasticizers do not, therefore, deform homogeneously when stressed as compared to primary plasticizers. The deformation appears only in the plasticizer-rich phase and the mechanical properties of the system are poor. Unlike primary plasticizers, secondary plasticizers cannot be used alone and are usually employed in combination with a primary plasticizer. 

Plasticizers comprise the largest volume additives in today s plastics industry. Their primary functions are to impart flexibility, softness and extensibility to rigid polymers. In addition, plasticizers facilitate processability by reducing viscosity and lubricating thus allowing a lower processing temperature. Plasticizers also increase impact resistance and reduce the brittleness of plastics, particularly at low temperatures (Table 3.4). General purpose plasticizers... 

Our redesigned book features major changes and additions. The Modern Plastics World Encyclopedia now contains a chapter on each primary process and articles on the latest industry trends and developments. Each chapter contains machinery charts in U.S. and metric standards as well as a comprehensive global Buyers Guide by process, including sales and service offices and sales agents. 

The polymer in plastics undergo some primary processing such as distillation, cracking, or solvent extraction to produce ethylene (C2H4),... 

Injection molding is a primary processing method. In other words, the material must exist in a plastic state so that it can be processed. This plastic state is characterized by the viscous flow properties exhibited by raw plastic materials such as powders or granulates. 

Requirements of special performance of plasticizers used in the injection molding process are seldom. In optical disk molding, the material requites mote plasticization during processing than ditring the product use. For this reason carbon dioxide was used as an additional plasticizer. Primary plasticizers were selected in such a manner that they will facilitate dissolution of carbon dioxide in melt. Figitre 14.17 shows that the more carbon dioxide dissolves, the lower is the glass transition tern-process, melt viscosity is decreased and... 

The fracture of practical adhesive joints involves two primary processes— cohesive or adhesive failure at or near the joint and work (reversible and irreversible) involved in plastic, elastic, or viscoelastic deformation of one or all of the components of the joint—one of the two solid surfaces or the adhesive (Fig. 19.4). As indicated in the preceding chapter on friction, cohesive failure of the weaker of two solids in contact is common. The same can be said for normal adhesive joints, in that actual adhesive failure (i.e., exactly at the interface) is less common that cohesive failure, of, for example, the adhesive material, near the interface. What, then, are the necessary conditions for obtaining good adhesion between two surfaces ... 

Lubricants. Lubricants represent a broad class of materials that are used to improve the flow characteristics of plastics during processing. Besides this primary task of improving flow properties, lubricants can act as melt promoters, antiblock, antitack, and antistatic agents as well as color and impact improvers. They can be used in conjunction with metal release agents and heat stabilizers. Lubricants are widely... 

Successful material recycling is dependent upon the purity and uniformity of the plastics waste. The properties of the recycled material depend upon the history of the synthesised polymer, the primary processing and application, and finally the recovery methods/equipment. Sorted, single polymer waste exhibiting low... 

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