Commercial Plastic Additives

The principal chemical uses of BTX are illustrated in Figure 1 and Hsted in Table 1 (2). A very wide range of consumer products from solvents to fibers, films, and plastics are based on BTX. The consumption of BTX is approximately in the proportions of 67 5 28, respectively. However, no BTX process gives BTX in these proportions. The economic value of benzene and xylenes (especially -xylene) is normally higher than that of toluene. Because of this, processes that convert toluene to benzene by hydrodealkylation (3) and disproportionate toluene to benzene and xylenes (4) have been commercialized. In addition, reforming processes that emphasize production of either benzene or -xylene [106 2-3] have been described (5). Since these are not classified as BTX processes they are not discussed in detail here. 

In a commercial plastics material there are also normally a number of other ingredients present and these may also be affected by the above agencies. Furthermore they may interact with each other and with the polymer so that the effects of the above agencies may be more, or may be less, drastic. Since different polymers and additives respond in different ways to the influence of chemicals and radiant energy, weathering behaviour can be very specific. 

There are at the present time many thousands of grades of commercial plastics materials offered for sale throughout the world. Only rarely are the properties of any two of these grades identical, for although the number of chemically distinct species (e.g. polyethylenes, polystyrenes) is limited, there are many variations within each group. Such variations can arise through differences in molecular structure, differences in physical form, the presence of impurities and also in the nature and amount of additives which may have been incorporated into the base polymer. One of the aims of this book is to show how the many different materials arise, to discuss their properties and to show how these properties can to a large extent be explained by consideration of the composition of a plastics material and in particular the molecular structure of the base polymer employed. 

For standard or proprietary polymer additive blends there is the need for analytical certification of the components. Blend technology has been developed for two- to six-component polymer additive blend systems, with certified analytical results [81]. Finally, there exist physical collections of reference additive samples, both public [82] and proprietary. The Dutch Food Inspection Service reference collection comprises 100 of the most important additives used in food contact plastics [83-85]. Reference compounds of a broad range of additives used in commercial plastics and rubber formulations are generally also available from the major additive manufacturers. These additive samples can be used as reference or calibration standards for chromatographic or spectroscopic analysis. DSM Plastics Reference Collection of Additives comprises over 1400 samples. 

Whatever the approach, the result is a difficult-to-analyse system. Such options suit polymer producers better than additive suppliers. Aromatic polymers (PPO) have been mentioned as char-forming FRs. Polymeric UV absorbers, blended in proper proportions with commercial plastics, have potential use as stabilisers for fibres, films and coatings. Several monomeric stabilisers containing a vinyl group were homopolymerised and used as stabilisers for PE, PVC, acrylates, polystyrene, cellulose acetate and several vinyl polymers [55]. 

Table II.l Classes of commercial plastic, mbber and coatings additives and polymerisation aids (including references to databases by trade name, chemical, function, application and manufacturer)...

Since many synthetic plastics and elastomers and some fibers are prepared by free radical polymerization, this method is important. Table 6.1 contains a listing of commercially important addition polymers including those that will be emphasized in this chapter because they are prepared using the free radical process. 

Clear impact-resistant polystyrene is a commercial plastic with the desirable combination of toughness and exceptional clarity. It is a styrene-1,3-butadiene multiblock copolymer containing more than 60% styrene. Most of these products are mixtures of block copolymers formed by incremental additions of initiator and monomers followed by coupling (Sec. 5-4c). The products generally have a tapered and multiblock composition with branching (due to the coupling agent). 

In addition to the polymer, copolymers of vinyl chloride with other vinyl monomers are important commercial plastics. Copolymers with vinyl acetate, which is produced from acetylene and acetic acid, are widely used in sheeting, surface coating, and filaments, being less brittle and more readily soluble in organic solvents than is pure polyvinyl chloride. Copolymers with acrylonitrile are also of importance for the production of... 

Murray [91] has described a gas chromatographic method for the determination in water of triarylphosphate esters (lmol S-140, tricresyl phosphate, cresol phosphate). These substances are used commercially as lubricant oil and plastic additives, hydraulic fluids and plasticisers. The method involves extraction from the samples, hydrolysis and measurement of the individual phenols by gas chromatography as the trimethylsilyl derivatives. The lower detection limit was about 3ppm. 

BASF s BASIL process [15] and the Dimersol process [16] have both been commercialized. The former uses the ionic liquid as a phase transfer catalyst to produce alkoxyphenylphosphines which are precursors for the synthesis of photoinitiators used in printing inks and wood coatings. The imidazole acts as a proton scavenger in the reaction of phenyl-chlorophosphines with alcohols to produce phosphines. The Dimersol process uses a Lewis acid catalyst for the dimerization of butenes to produce Cs olefins which are usually further hydroformylated giving C9 alcohols used in the manufacture of plasticizers. Several other processes are also at the pilot plant scale and some ionic liquids are used commercially as additive e.g. binders in paints. 

It was discovered in the twenties by Dr Waldo Semon when attempts were being made to dissolve PVC that it could be plasticized to give elastomer-like compounds, and since then an extensive variety of plasticizers has been suggested and many introduced commercially. The addition of plasticizers provides materials with a considerable range of flexibility and softness those used most commonly today are esters of C8 to C10 alcohols, such as phthalates, phosphates, and sebacates—particularly dioctyl phtha-late (known also as 2-ethylhexyl phthalate), di-iso-octyl phthalate, and dial-phanyl phthalate. 

Five different batches of a commercial plastic are sampled to determine the variation of inert additives between batches. Since each batch consists of several thousand pounds of material, several samples are taken from each batch to determine the variation in the batch With the following informatioa determine whether or not the variability of the separate batches forms a homogeneous test. Use a 95 percent probability level in the statistical analysis. 

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. 

Plastic materials are widely used in numerous industries. The physiochemical nature of these materials provides a multitude of diverse products with their necessary, desirable performance characteristics. Commercial plastics are very complex materials. In addition to the various base polymers, commercially viable plastics contain a number of compounding ingredients (additives) whose purpose is to give the material its desired physical and/or chemical properties. Table 1 provides a brief summary of the types of additives typically encountered in commercial polymer systems. 

The monomer that we have used as a backbone for our work toward flame retardant polymers is commonly called bisphenol C (BPC) or l,l-dichloro-2,2-bis(4-hydroxyphenyl) ethylene. As has been shown by many research groups, BPC can be used as a blendable additive in a commercial plastic or as part of a polymer backbone to effectively impart flame resistance to certain polymeric materials.When thermally decomposed, BPC exothermically produces volatile products such as HCl and CO2, and the unique structure formed upon thermal degradation leads to a very stable carbon structure (char). It is this pyrolysis byproduct and the high char forming nature of BPC that give inherently low flammability and flame retardancy (Fig. 3) in these polymers and blends. 

Typical commercial plastics contain a number of low molecular weight additives that develop or maintain particular properties In the plastic. The migration and loss of additives used to prolong the useful life of plastics Is a major mode of failure. The migration of these components also raises the possibility of harmful contamination of food by plastic packaging. 

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