Additives and Fillers

In addition to monomers, polymers can also incorporate in their structures additives and fillers that enhance some specific properties of the polymer. Usually, additives are chemical compounds that affect chemical properties. The major additives categories are  

Therefore, plasticizers must exhibit a good chemical affinity to the polymer, and they should not be easily removable or volatile to insure good stability of the polymer. Usually, plasticizers are organic esters made from alcohol and ortho-phosphoric acid or organic acids (e.g., phthalic, stearic, adipic). Diisooctyl phthalate is a common plasticizer. 

Fillers are different from additives, in the sense that they are only mixed with the polymer matrix to impart specific physical properties instead of chemical properties such as mechanical strength, electrical conductivity or dielectric properties, thermal insulation and they never take part in the macromolecule chain. Because fillers together with the polymer matrix are considered as composite materials they will be discussed in detail in the corresponding chapter. The major categories of filler, with some example, are however given briefly here  

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Dicyclopentadiene is also polymerized with tungsten-based catalysts. Because the polymerization reaction produces heavily cross-Unked resins, the polymers are manufactured in a reaction injection mol ding (RIM) process, in which all catalyst components and resin modifiers are slurried in two batches of the monomer. The first batch contains the catalyst (a mixture of WCl and WOCl, nonylphenol, acetylacetone, additives, and fillers the second batch contains the co-catalyst (a combination of an alkyl aluminum compound and a Lewis base such as ether), antioxidants, and elastomeric fillers (qv) for better moldabihty (50). Mixing two Uquids in a mold results in a rapid polymerization reaction. Its rate is controlled by the ratio between the co-catalyst and the Lewis base. Depending on the catalyst composition, solidification time of the reaction mixture can vary from two seconds to an hour. Similar catalyst systems are used for polymerization of norbomene and for norbomene copolymerization with ethyhdenenorbomene. 

Various additives and fillers may be employed. Calcium carbonate, talc, carbon black, titanium dioxide, and wollastonite are commonly used as fillers. Plasticizers are often utilized also. Plasticizers may reduce viscosity and may help adhesion to certain substrates. Thixotropes such as fumed silica, structured clays, precipitated silica, PVC powder, etc. can be added. Adhesion promoters, such as silane coupling agents, may also be used in the formulation [69]. 

Whether a plastic gives off light or heavy smoke and toxic or noxious gases depends on the basic plastic used, its composition of additives and fillers, and the conditions under... 

Table 7-7 Applications for conductive plastics where different additives and fillers are used...

Also, nylon-6 waste may be hydrolyzed in the presence of an aqueous alkali metal hydroxide or acid5 to produce an alkali metal or acid salt of 6-aminocaproic acid (ACA). The reaction of nylon-6 waste with dilute hydrochloric acid is rapid at 90- 100°C. The reaction mixture is poured into water to form a dilute aqueous solution of the ACA salt. Filtration is used to remove undissolved impurities such as pigments, additives, and fillers followed by treatment of the acid solution with a strong cation exchange resin. A sulfonic acid cationic exchanger absorbs ACA salt and pure ACA is eluted with ammonium hydroxide to form a dilute aqueous solution. Pure ACA is obtained by crystallization of die solution. 

Equation (15) has a standard deviation of 0.0871 and a correlation coefficient of 0.979. It is based on a data set containing 61 polymers chosen in such a way as to avoid incorporation of the effects of additives and fillers. Further analysis of the data set gave the following results ... 

UHMWPE can be formulated with additives and fillers. However,... 

The particular absorber to be used in a given application depends on several factors. One important criterion is whether the absorber will strongly absorb that portion of the ultraviolet spectrum responsible for degradation of the plastic under consideration. Compatibility, volatility, thermal stability, and interactions with other additives and fillers are other items that must be considered. When used in food wrappings, Food and Drug Administration approval must be obtained. While one or more of these considerations may rule out a given stabilizer or influence llie choice of one class over another, the final selection must await the results of extensive accelerated and long-term tests. 

Many studies use infrared spectroscopy for quality control and quality analysis in polymer production. It is particularly used for the determination of the composition of copolymers and polymer blends and also for determination of additive and filler contents [90, 91, 92]. 

Plastics as technical materials are based on polymers (or macromolecular substances), but in most cases they contain a number of added components. Such an added material may be another polymer in this case we have a polymer blend. Moreover, there is a large variety of additives and fillers, compounded into the polymer for various purposes, which are roughly categorized below ... 

In the assortment of technically used materials we also meet a broad variability of additives and fillers, added by the manufacturer. 

As noted earlier, a great variety of additives and fillers may be used in plastic compositions. A recent review report about fillers lists common minerals as... 

These low-intensity units are less energy-intensive, requiring lower horsepower, but they do not achieve mixing of the same quality in comparable cycle times. They are limited in use to such jobs as blending additives and fillers into low- to medium-viscosity... 

Solubility of fillers is also important in dental cements and biomaterials. Unlike in construction cements, the cost of the end product is not a major issue in dental cements, but purity, biocompatibility, and performance of the final product is very important. Each filler component has its own role in modifying the behavior of the final product. As we shall see later in Chapter 18, wollastonite improves the flexural strength and toughness of the dental cements because the grains of wollastonite have elongated needle shape (acicular). Hydroxyapatite is added to provide biocompatibiUty to the product. Attributes of these fillers govern the final properties of the products and hence it is necessary that, not only one understands detailed properties of the binder components, but also that of the additives and filler components. For this reason, this chapter is devoted to describe the genesis and properties of the binder and important filler components. 

Plastics. Plastics are the polymeric materials with properties intermediate between elastomers and fibers. In spite of the possible differences in chemical structure, the demarcation between fibers and plastics may sometimes be blurred. Polymers such as polypropylene and polyamides can be used as fibers and plastics by a proper choice of processing conditions. Plastics can be extruded as sheets or pipes, painted on surfaces, or molded to form countless objects. A typical commercial plastic resin may contain two or more polymers in addition to various additives and fillers. Additives and fillers are used to improve some property such as the processability, thermal or environmental stability, and mechanical properties of the final product. 

Various additives and fillers (especially polar substances) introduced into the polymer matrix in order to increase strength, reduce flammability, etc., may drastically reduce the dielectric properties of foams. 

Additives and Fillers for Structural Foam Chemical Blowing Agents Processing Structural Foam Tooling... 

Synergistic effects when used in conjunction with other additives and fillers. 

The tasks of polymer compounding can be the mixing of the polymer with additives and fillers (such as glass fibers), and the degassing of volatile components such as monomers. It can even mean to carry out chemical reactions in the extruder. Usually extruders with two intermeshing screws, so called co-rotating twin screw extruders, are used. 

A dataset containing the dielectric constants of 61 polymers measured at room temperature was prepared by careful comparison and combination of the data provided by many sources [3,14-20]. For polar polymers, special care was exercised to select values of e which represented, whenever possible, the "intrinsic" properties of the polymers, rather than the effects of the additives and fillers used. It will be seen in Section 9.D that the dielectric constants of typical commercial grades of many polar polymers, which contain significant amounts of additives, are considerably higher than the "intrinsic" values used in this section. 

Certain types of additives and fillers can improve TTOS and/or fire resistance. 

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