Carbonate polymer physical properties

Polymers can be made that contain more than one type of repeat unit. For example, the R group on the asymmetric carbon in Figure 1.56 could be chlorine in some of the monomer units and fluorine in the rest. Such polymers are called copolymers. The ratio of the two types of monomers can vary from 0 to 1, and there can be more than two types of monomers in a copolymer. The presence of more than one type of repeat unit opens up many possibilities for variation in the structure of the polymer, or chain architecture as it is sometimes called. We will not describe the myriad of possible variations and the important consequences in terms of polymer physical properties, but here merely categorize copolymers in some broad, structural terms. 

Figure 45 shows another example of the dependence of polymer physical properties on the branch length. Copolymers were made with Cr/silica catalyst to have the same approximate density and MI. Various comonomers were used, ranging from propylene to 1-octene. The ESCR of each polymer was then determined and is plotted against the number of carbon atoms in the comonomer. There is a clear advantage associated with longer branch lengths. 

Besides reinforcement for rubber, the principal functions that carbon black imparts to a compoimd material are color, ultraviolet damage resistance, electrical conductivity, nondegradation of polymer physical properties, and ease of dispersion. The carbon blacks used for these purposes are classified as special-grade blacks. Smaller volume applications exploit other principal attributes, such as chemical inertness, thermal stability, and an open porous structure. The secondary attributes include chemical and physical purity, low affinity for water adsorption, and ease of transportation and handling. 

Chivrac F, Pollet E, Averous L (2009) Progress in nano-biocomposites based on polysaccharides and nanoclays. Mater Sci Eng R Rep 67(1) 1-17 Crosthwaite JM, Aid SNVK, Maginn EJ, Brennecke JF (2004) Liquid phase behavior of imidazolium-based ionic liquids with alcohols. J Phys Chem B 108(16) 5113-5119 De Silva RT, Pasbakhsh P, Goh KL, Chai S-P, Ismail H (2013) Physico-chemical characterisation of chitosan/halloysite composite membranes. Polym Testing 32(2) 265-271 Debelak B, Lafdi K (2007) Use of exfoliated graphite filler to enhance polymer physical properties. Carbon 45(9) 1727-1734... 

B. Debelak and K. Lafdi, Use of exfoliated graphite filler to enhance polymer physical properties. Carbon, 45(9) 1727-1734, August 2007. 

The carbon black in semiconductive shields is composed of complex aggregates (clusters) that are grape-like stmctures of very small primary particles in the 10 to 70 nanometer size range (see Carbon, carbon black). The optimum concentration of carbon black is a compromise between conductivity and processibiUty and can vary from about 30 to 60 parts per hundred of polymer (phr) depending on the black. If the black concentration is higher than 60 phr for most blacks, the compound is no longer easily extmded into a thin continuous layer on the cable and its physical properties are sacrificed. Ionic contaminants in carbon black may produce tree channels in the insulation close to the conductor shield. 

Nittile mbber is much like SBR in its physical properties. It can be compounded for physical strength and abrasion resistance using traditional fillers such as carbon black, siUca, and reinforcing clays. The primary benefit of the polymer is its oil and solvent resistance. At a medium ACN content of 34% the swell in IRM 903 oil at 70°C is typically 25—30%. Nitrile mbber processes on conventional mbber equipment and can be compression, transfer, or injection molded. It can also be extmded easily. 

Chlorinated Polyethylene. Chlorinating polyethylene under pressure results in a polymer having a chlorine content varying from 25 to 42%. The polymer requires the incorporation of carbon black and minerals for achieving good physical properties. The polymers handle like conventional polymers and can be mixed and processed on conventional mbber equipment. 

Styrene is a colorless Hquid with an aromatic odor. Important physical properties of styrene are shown in Table 1 (1). Styrene is infinitely soluble in acetone, carbon tetrachloride, benzene, ether, / -heptane, and ethanol. Nearly all of the commercial styrene is consumed in polymerization and copolymerization processes. Common methods in plastics technology such as mass, suspension, solution, and emulsion polymerization can be used to manufacture polystyrene and styrene copolymers with different physical characteristics, but processes relating to the first two methods account for most of the styrene polymers currendy (ca 1996) being manufactured (2—8). Polymerization generally takes place by free-radical reactions initiated thermally or catalyticaHy. Polymerization occurs slowly even at ambient temperatures. It can be retarded by inhibitors. 

The carbon blacks used in plastics are usually different from the carbon blacks used in mbber. The effect of carbon black is detrimental to the physical properties of plastics such as impact strength and melt flow. Electroconductive grades of carbon black have much higher surface areas than conventional carbon blacks. The higher surface areas result in a three-dimensional conductive pathway through the polymer at much lower additive levels of the carbon black. The additive concentrations of electroconductive carbon blacks is usually j to that of a regular carbon black (132). 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

Most commercial polymers are substantially linear. They have a single chain of mers that forms the backbone of the molecule. Side-chains can occur and can have a major affect on physical properties. An elemental analysis of any polyolefin, (e.g., polyethylene, polypropylene, poly(l-butene), etc.) gives the same empirical formula, CH2, and it is only the nature of the side-chains that distinguishes between the polyolefins. Polypropylene has methyl side-chains on every other carbon atom along the backbone. Side-chains at random locations are called branches. Branching and other polymer structures can be deduced using analytical techniques such as NMR. 

Physical properties of carbon black-filled EPR and EPDM elastomers have been found to be comparable with the suUur-cured analogues [372]. Aromatic oils increase the optimum dose requirement for these compounds due to the reaction of the transient intermediates formed during radiolysis of the polymer with the oil as well as energy transfer which is particularly effective when the oil contains aromatic groups. The performance and oxidative stability of unfilled EPDM as well as its blend with PE [373], and the thermal stabdity and radiation-initiated oxidation of EPR compounds are reported by a number of workers [374,375]. 

Chemicals like polyorthoaminophenol, diphenylamine in small amounts have been found to decrease the yield of cross-linking [388]. The tensile strength of the carbon black-filled polychloroprene compounds has been found to be comparable to the conventional thermally cured one. The physical properties [389] have been observed to improve on adding cross-linking promoters like A,A -hexamethylene-bis-methacrylamide into the polymer matrix. 

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