Applications thermoplastics

Commercially available flame retardants include chlorine- and bromine-containing compounds, phosphate esters, and chloroalkyl phosphates. Recent entry into the market place is a blend of an aromatic bromine compound and a phosphate ester (DE-60F Special) for use in flexible polyurethane foam (8). This paper describes the use of a brominated aromatic phosphate ester, where the bromine and phosphorus are in the same molecule, in high temperature thermoplastic applications. 

The lack of mechanical strength for thermoplastic hyperbranched polymers makes them more suitable as additives in thermoplast applications. Hyperbranched polyphenylenes have been shown to act successfully as rheology modifiers when processing linear thermoplastics. A small amount added to polystyrene resulted in reduced melt viscosity [31]. (Sect> 3.1). 

The consumption of thermoplastics predominates (as indicated by Table 2.3) but the market share distribution of the thermoplastic application sectors (see Table 2.8 and Figure 2.7) is nevertheless somewhat different from that of plastics as a whole. Figures vary broadly according to geographical area. 

Table 2 Market shares for the eight main thermoplastic application sectors...

Figure 2.26 shows the versatility of thermoplastic applications by some examples for interior building use. 

Considerable attention is also given to the methods that need to be used to adequately characterise a filler for use in thermoplastic applications, particularly the determination of particle shape and size. 

It is estimated that over one million tons of mineral fillers were used in thermoplastic applications in western Europe in 1986 [2], and the figure is doubtless much greater today. Mineral fillers are used to some extent in virtually all the commercially important thermoplastic polymers but, in volume terms, the principal markets are in PVC and polyolefins, where calcium carbonate dominates the filler types with over 80% of the volume consumption [2]. 

Filler surface treatments are of considerable use in thermoplastic applications and are often applied as part of the production process. The various methods used to apply such treatments are therefore covered in this article. 

Dry coating is probably the main method used in preparing products for thermoplastic applications. Due to the cost of additional drying operations, it is the method of choice when the filler itself is produced by a dry process. It is also useful where wet coating procedures would give rise to effluent problems. 

The hardness of mineral fillers is of considerable importance in thermoplastics applications. In general soft fillers are preferred, as the harder ones tend to cause... 

Aluminium hydroxide has a Moh hardness of about 3 and a specific gravity of 2.4. It decomposes endothermically with the release of water at about 200 °C and this makes it a very useful flame retardant filler, this being the principal reason for its use in polymers. The decomposition temperature is in fact too low for many thermoplastics applications, but it is widely used in low smoke P VC applications and finds some use in polyolefins. For these applications low aspect ratio particles with a size of about 1 micron and a specific surface area of 4-10 m g are preferred. The decomposition pathway can be diverted through the mono-hydrate by the application of pressure, and this may reduce the flame retardant effect [97]. This effect can be observed with the larger sized particles. Although it is chemically the hydroxide, it has for many years been known as alumina trihydrate and by the acronym ATH. 

PCC is normally used in fatty acid coated form in thermoplastic applications. The means by which the coating is applied is treated as proprietary by most producers but it is probably by the wet coating method, with a solution of the fatty acid salt added to an aqueous slurry of the filler, followed by filtration and drying. As described earlier, the use of fatty acid coatings can improve product filtration and drying characteristics. 

Styrene-acrylonitrile (SAN) resins possess many physical properties desired for thermoplastic applications. They are characteristically hard, rigid, and dimensionally stable with load bearing capabilities. They are also transparent, have high heat distortion temperatures, possess excellent gloss and chemical resistance, and adapt easily to conventional thermoplastic fabrication techniques. 

Regarding the use of preformed particles, the main advantages are the initial control of particle size, volume fraction, and composition of the disperse phase. Also important is the possibility of extending the use of these particles for thermoplastic applications, which means a large expansion of the market. 

This is the second most widely used fire-retardant filler. It is more expensive than aluminum hydroxide, but has a higher decomposition temperature (about 300°C), making it more suitable for use in thermoplastic applications where elevated processing temperatures are encountered. 

The term carbon black describes a group of industrial carbons created through the partial combustion or the thermal decomposition of hydrocarbons. Carbon black is unique in that it possesses the smallest particle size and highest oil absorption among the commercially available pigments for plastics. These characteristics help explain carbon black s excellent color strength, cost-effectiveness, and ultraviolet (UV) performance and place it as the most widely used black pigment for thermoplastic applications. 

Additive used for thermoplastic applications requiring lubrication, slip and anti-blocking properties. Commonly used in polyethylene and polypropylene films, as a lubricant in polyvinyl chloride, mold release agent, dyestuff dispersant for printing inks and surface coatings, and a blending agent for polyamide resins. 

The simplest technique is to dissolve the polymer in the appropriate solvent add the peroxide initiator, which abstracts a hydrogen radical and generates a radical on the polymer chain and then add fresh monomer for grafting onto this site. This technique has been employed in grafting methylacrylate onto natural rubber and synthetic polyisoprene. In this manner, several commercially useful products such as ABS resins have been prepared however, tire elastomers are not made in this manner because of the generation of micro and macro gel particles, which are detrimental to physical properties. In many cases when latex grafting has been used, the product has usually been targeted toward thermoplastic applications rather than rubber applications. 

Problem Progress toward more affordable long-glass-fiber thermoplastic applications is limited by conventional com-pounding/moldlng practices. 

Fig. 2 Temperature-dependence of the modulus of elasticity (Young s modulus) of plastics (diagram). As an alternative to this modulus, tension a can also be plotted against constant elongation e or viscosity i), or other properties [2]. MSRe x,d- main softening range of elastomers, thermoplastics, duroplastics, Tgt associated glass transition temperature, Tfi flow point of the amorphous thermoplastic, //////// application range, application range...

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