ADDITIVES, FILLERS AND REINFORCEMENTS

Compounding to change and improve the physical and mechanical properties of plastics makes use of a wide variety of 

Filler or Reinforcement Chcmicul Resistance i 8 u i i Electrical Insulation Impact Strength Tensile Strength Dimensional Stability Stiffness Hardness Lubricity Electrical Conductivity Thermal Conductivity 1 8 C s TS 1 X I I h 11 

In general adding reinforcing fibers significantly increases mechanical properties. Particulate fillers of various types usually increase the modulus, plasticizers generally decrease the modulus but enhance flexibility, and so on. These RPs can also be called composites. However the name composites Utterly identifies thousands of different combinations with very few that include the use of plastics (Table 6-18). In using the term com- 

Many ingredients, especially those that are conductive, may affect electrical properties. Most plastics, which are poor conductors of current, build up a charge of static electricity. Antistatic agents can be added to attract-moisture, reducing the likelihood of a spark or discharge. 

Sacrifice (from Base Resin) Amorphous Crystalline 

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In addition to the broad categories of TPs and TSs, TPs can be further classified in terms of their structure, as either crystalline, amorphous, or liquid crystalline. Other classes (terms) include elastomers, copolymers, compounds, commodity resins, engineering plastics, or neat plastics. Additives, fillers, and reinforcements are other classifications that relate directly to plastics properties and performance. 

For applications having only moderate thermal requirements, thermal decomposition may not be an important consideration. However, if the product requires dimensional stability at high temperatures, it is possible that its service temperature or processing temperature may approach its temperature of decomposition (Tj) (Table 7-12). A plastic s decomposition temperature is largely determined by the elements and their bonding within the molecular structures as well as the characteristics of additives, fillers, and reinforcements that may be in them. 

In the past engineering TPs have replaced metal in numerous products in many industries by providing improvements in thermal properties.146 The ability to prepare and compound material properties through the choice of plastics with additives, fillers and reinforcements, has allowed the development of the flexibility inherent in TPs to meet the performance requirements required in these different applications. 

Additives, Fillers and Reinforcements 283 Commonly used in LDPE, EVA and... 

Additives, Fillers and Reinforcements 303 MOLD-RELEASE AGENTS (PARTING AGENTS)... 

Polypropylene is not one or even 100 products. Rather it is a multidimensional range of products with properties and characteristics interdependent on the type of polymer (homopolymers, random, or block copolymer), molecular weight and molecular weight distribution, morphology and crystalline structure, additives, fillers and reinforcing fillers, and fabrication techniques. 

The plastics polymerize after entering a mold. Mixing two or more components (additives, fillers, and reinforcements) in the proper chemical ratio is accomplished by a high-pressure impingement-type mixing head. This mix is directed into the mold cavity at low pressure, where it chemically reacts to form a plastic. The components are mixed together at a given ratio and then directed or basically poured into a mold under controlled temperature, pressure, and rate of flow. They polymerize and cure in... 

Compounding to change and improve the physical and mechanical properties of plastics makes use of a wide variety of materials as reviewed throughout this book. The major and large market for these materials, such as additives, fillers, and reinforcements, continues to expand as the demand for reducing the cost of plastics, plastics to function in wider or extreme markets, and under stricter regulatory regimes continue to expand. 

Table 9.5 Additive, filler, and reinforcement symbols with tolerances ...

Engineering plastics n. Plastics which are modified by using modifiers, additives, fillers and reinforcements. 

Up until World War II, almost all elastomers were based on natural rubber. During the war, synthetic rubbers began to replace the scarce natural rubber. Since that time production of synthetics has increased until it now far surpasses that of natural rubber. There are thousands of different elastomer compounds. Not only are there many different classes of elastomers, but also individual types can be modified with a variety of additives, fillers, and reinforcements. In addition, curing temperatures, pressures, and processing methods can be varied to produce elastomers tailored to the needs of specific applications. 

The applications of UFs include sanitary wares such as toilet seats, and knobs, closures, buttons, electrical accessories like housings and switches, laminates, and so on. Compounds of UFs use different additives, fillers, and reinforcements to provide different characteristics and permit processing in different equipment, principally by compression, transfer, and injection molding. Like many other TSs, such as the phenolics and melamines, they are easily preformed and preheated, either by RF preheaters or with screw... 

Twin-screw extrusion is used to blend additives, fillers, and reinforcements to polymers as well as blending of two or more polymers. For instance, additives are combined with biopolymers in a twin-screw extruder to increase the strength and mechanical properties. PHA materials are compounded with acrylic impact modifiers and boron nitride nucleating agent in a twin-screw extruder to improve the strength of PHA and increase the crystallinity percentage (Greene 2013). 

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