Nonpolar thermoplastics

Carbon black is the most widely used conducting filler in composite industry. Carbon black filled immiscible blends based on polar/polar (65), polar/nonpolar (63,66), nonpolar/nonpolar thermoplastics (67,68), plastic/rubber and rubber/mbber blends (69,70) have already been reported in the literature. The properties of carbon black filled immiscible PP/epoxy were reported recently by Li et al. (60). The blend system was interesting because one of the components is semicrystalline and the other is an amorphous polar material with different percolation thresholds. The volume resistivity of carbon black filled individual polymers is shown in Fig. 21.23. 

Solution Though polar, PVC-like nonpolar thermoplastics can be used as insulation for electrical wires in low-frequency applications. Prolonged use of hotrsehold electronic appliances has a tendency to generate heat. Therefore, these appliances can be a potential sotrrce of fire hazard. Unlike other thermoplastic polyolefins, PVC has inherent (built-in) fire retardancy because of its 57% chlorine content. This reduces the susceptibility to fire outbreak arising from prolonged use of household electronic apphances. 

A typical cured aerospace epoxy resin is highly cross-linked and may contain a dispersed nonpolar thermoplastic or rubber which reduces the equilibrium moisture content and hmits the reduction in Tg. As shown in Table 12.2, more advanced systems, such as an epoxy—cyanate ester blend, absorb lower concentrations of water at equilibrium. However, the water is not uniformly distributed so that the epoxy phase is stiU plasticised to the same extent. Figure 12.12 shows that the different component epoxies and/or hardeners are plasticised differentially with the development of additional relaxation peaks. We discussed the different degrees of water molecule hydrogen bonding as a function of network polarity in this chapter. 

Uses Softener, primary plasticizer in hot-melts, adhesives, coatings, and rubber compd., food-pkg. and processing operations Features Low m.w. nonpolar thermoplastic offers It. color, and solubility, and wide compatibility... 

Cellulosic fibres used for reinforcement in nonpolar thermoplastics, such as PP, have to be modified because effective wetting of fibres and strong interfacial adhesion are required to obtain composites with optimised mechanical properties [31, 32]. Several methods for improvement in the adhesion between polymer and cellulosic fibres have been developed. 

HOPE geomembranes are manufactured from a nonpolar thermoplastic polymer which is chemically very stable but forms a melt above 140 °C, and so can be extruded at approximately 200 °C. Therefore in practice, HDPE geomembranes cannot be glued by chemical processes and welding by a thermal process is the jointing technology of choice. 

Bark fibers, which would be expected to have a non-polar (ligninlike) surface gave good results when used as a filler in nonpolar thermoplastics. Likewise, peanut hull flour and walnut shell flour, which are rich in phenolic, lignin-like material, are relatively good fillers. Treatment of the surface of rice hull flour to increase its compatability with thermoplastic resins has been shown to greatly enhance its value as a filler. None of the shell flours are fibrous. 

Properties. Ethyl cellulose [9004-57-3] (EC) is a nonionic, organo-soluble, thermoplastic cellulose ether, having an ethyl DS in the range of 2.2-2.7. Actually, EC is water-soluble at DS 1.2, but only those products that are thermoplastic and soluble in organic solvents are of commercial importance, because of thek abiUty to form tough, stable films. Above a DS of about 2.5, EC is soluble in many nonpolar solvents. 

Polyether-based thermoplastic copolyesters show a tendency toward oxidative degradation and hydrolysis at elevated temperature, which makes the use of stabilizer necessary. The problem could be overcome by incorporation of polyolehnic soft segments in PBT-based copolyesters [31,32]. Schmalz et al. [33] have proposed recently a more useful technique to incorporate nonpolar segments in PBT-based copolyesters. This involves a conventional two-step melt polycondensation of hydroxyl-terminated PEO-PEB-PEO (synthesized by chain extension of hydroxyl-terminated hydrogenated polybutadienes with ethylene oxide) and PBT-based copolyesters. 

Schmalz H., Abetz V., Lange R., and Soliman, M. New thermoplastic elastomers by incorporation of nonpolar soft segments in pbt-based copolyesters, Macromolecules, 34, 775, 2001. 

As with most nonpolar hydrocarbon-intense polymers, bitumens exhibit good resistance to attack by inorganic salts and weak acids. They are dark, generally brown to black, and their color is difficult to mask with pigments. They are thermoplastic materials with a narrow service temperature range unless modified with fibrous fillers and/or synthetic resins. They are abundant materials that are relatively inexpensive, thus their use in many bulk applications. 

As shown in Table 15.8, polyaryl sulfones have excellent mechanical properties. The commercial products differ somewhat in properties, but all have high heat deflection temperatures (at least 175 C). These thermoplastic engineering polymers have excellent resistance to nonoxidizing acids, salts, and alkalis, and to polar solvents. They are attacked by nonpolar solvents such as benzene. 

Polymer chemistry is important in obtaining adhesion to the glass surface (Figure 10). The tensile reinforcement factor—the ratio of tensile strengths of the reinforced system to the matrix resin—is used as a measure of adhesion. Two dissimilar polymers, polypropylene and nylon, are used to illustrate the importance of polymer chemistry. Polypropylene is an inherently difficult polymer to reinforce because of its nonpolar nature and lack of reactivity. Nylon, on the other hand, is highly polar and is one of the easiest thermoplastics to reinforce. The modified poly-... 

A variation of the sequential monomer addition technique described in Section 9.2.6(i) is used to make styrene-diene-styrene iriblock thermoplastic rubbers. Styrene is polymerized first, using butyl lithium initiator in a nonpolar solvent. Then, a mixture of styrene and the diene is added to the living polystyryl macroanion. The diene will polymerize first, because styrene anions initiate diene polymerization much faster than the reverse process. After the diene monomer is consumed, polystyrene forms the third block. The combination of Li initiation and a nonpolar solvent produces a high cis-1,4 content in the central polydiene block, as required for thermoplastic elastomer behavior. 

Very few CPs are produced in bulk quantities. Polyphenylene sulfide, a member of the third generation of polymers, was produced in bulk quantities many years before CPs were established and its dopability was elucidated. Polyethylenedioxythiophene is commercially available as a water-based colloidal dispersion (Baytron P water dispersion), and presumably as dispersible powders. The powders with a conductivity of 5-10 S/cm can be dispersed in thermoplastic polymers and in organic solvents such as xylene. Polyaniline doped with dodecylbenzene sulfonic acid and complexed with zinc dodecylbenzene sulfonate is commercially available as a powder, which can be dispersed in polyolefins. The same polymer doped with p-toluenesulfonic acid is also available as a dispersible powder, Ormecon, and in a predispersed form for solution processing in polar and nonpolar media. Based on Ormecon PANi, there are many commercial products marketed for many different applications. 

This is an example of the preparation of ABA-type thermoplastic elastomer. Styrene is polymerized first since styryl initiation of isoprene is faster than the reverse reaction. The reaction is carried out in a nonpolar solvent with Li" " as the counterion to enable predominantly cis-l,4-polyisoprene to be formed in the second growth stage. The living polystyrene-6/ocfc-polyisoprene AB di-block copolymer resulting from the second stage is then coupled by a double nucleophilic displacement of Cl ions from a stoichiometric equivalent of dichloromethane to give a polystyrene-61ock-polyisoprene-/)/ock-polystyrene triblock copolymer. 

Polyolefin - Polyolefins are a large class of carbon-chain elastomeric and thermoplastic polymers usually prepared by addition (co)polymerization of olefins or alkenes such as ethylene. The most important representatives of this class are polyethylene and polypropylene. There are branched and linear polyolefins and some contain polar pendant groups or are halogenated. Unmodified polyolefins are characterized by relatively low thermal stability and a nonporous, nonpolar surface with poor adhesive properties. Processed by extrusion, injection molding, blow molding, and rotational molding. Other thermoplastic processes are used less frequently. This class of plastics is used more and has more applications than any other. Also called olefinic resin, olefinic plastic. 

One key factor for producing acceptable WPCs is the interaction between the wood and thermoplastic components (wood-polymer interface). It is difficult to achieve wood/plastic interaction because the hydrophobic thermoplastic (nonpolar) and hydrophilic wood (polar) are energetically different [2, 4]. During wood/plastic mixing, the thermoplastic must first coat or spread over the wood fiber surface to interact [4]. It is observed in Figure 26.2 that the polymer-fiber interface and a poor surface adhesion lead to fiber slipping from the matrix. 

The well-known examples of blends are impact modified, toughened polymers, where polymers with different glass transition temperatures are blended, such as a rubber with a thermoplastic. Many other blends are known, such as barrier polymers for packaging, where specific polar or nonpolar polymers improve the properties of polymer blends, combined to increase the resistance against transport of water and a certain gas (oxygen, carbon dioxide, etc.), such as PA (barrier to oxygen) with a polyolefin (barrier to water vapor). 

The cured or fully imidized polyimide, unlike the poly(amic acid), is insoluble and infusible with high thermooxidative stability and good electrical-insulation properties. Thermoplastic polyimides that can be melt processed at high temperatures or cast in solution are now also available. Through an appropriate choice of the aromatic diamine, phenyl or alkyl pendant groups or main-chain aromatic polyether linkages can be introduced into the polymer. The resulting polyimides are soluble in relatively nonpolar solvents. 

High density PE is a milky-white, nonpolar, linear thermoplastic. Its density ranges from 0.940 to 0.965 g/cm, and it has a melting temperature of about 128 to 138°C. It is one of the most versatile polymers, and is the second most commonly used plastic in the packaging industry. Typical applications include ... 

Neutralization of ethylene copolymers containing up to 5%-10% acrylic or methacrylic acid copolymer with a metal salt such as the acetate or oxide of zinc, magnesium, and barium yields products referred to as ionomers. (Commercial products may contain univalent as well as divalent metal salts.) lonomers are marked by Du Pont under the trade name Surlyn. These have interesting properties compared with the nonionized copolymer. Introduction of ions causes disordering of the semicrystalline structure, which makes the polymer transparent. lonomers act like reversibly cross-linked thermoplastics as a result of microphase separation between ionic metal carboxylate and nonpolar hydrocarbon segments. The... 

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