Poly engineering materials

Although the first two materials discussed in this chapter, the polyphenylenes and poly-p-xylylenes, have remained in the exotic category, most of the other materials have become important engineering materials. In many cases the basic patents have recently expired, leading to several manufacturers now producing a polymer where a few years ago there was only one supplier. Whilst such competition has led in some cases to overcapacity, it has also led to the introduction of new improved variants and materials more able to compete with older established plastics materials. 

The use of PBT as an engineering material is more a consequence of a balance of good properties rather than of a few outstanding ones. It does not possess the toughness of polycarbonate, the abrasion resistance of an aliphatic polyamide, the heat resistance of a polysulphone, polyketone or poly(phenylene sulphide) or... 

With a somewhat lower level of heat resistance but with many properties that make them of interest as engineering materials alongside the polycarbonates, polysulphones, poly(phenylene sulphides) and polyketones are the so-called polyarylates which are defined as polyester from bis-phenols and dicarboxylic acids. 

In 1938, while attempting to prepare fluorocarbon derivatives, Roy J. Plunkett, at DuPont s Jackson Laboratory, discovered that he had prepared a new polymeric material. The discovery was somewhat serendipitous as the TFE that had been produced and stored in cylinders had polymerized into poly(tetra-fluoroethylene) (PTFE), as shown in Eigure 4.2. It did not take long to discover that PTFE possessed properties that were unusual and unlike those of similar hydrocarbon polymers. These properties include (1) low surface tension, (2) high Tm, (3) chemical inertness, and (4) low coefficient of friction. All of these properties have been exploited in the fabrication of engineering materials, wliich explains the huge commercial success of PTFE. 

The important feature of polymers based on vinyl monomers is their transparency in the visible part of the spectrum. This is why the most important articles produced from these materials are organic glasses, which are used in the aircraft, automobile and ship-building industries as engineering materials, and also in civil engineering, and the optical, chemical, food industries, etc. The main technical characteristics of poly (methyl methacrylate) are given in Table 1.1. 

Mixtures of liquid vinyl monomers and polymer powders serve as a basis for a special group of engineering materials. Vinyl acetate and acrylonitrile monomers are injected into polymer powders to accelerate swelling and gel formation. Styrene is added to improved the molding characteristics of reactive mixtures. Polystyrene, poly(vinyl acetate), poly(vinyl chloride), etc. are the most commonly used polymer powders. 

Acyl cations are involved as propagating species in the synthesis of poly-(ether ketone)s. Poly (ether ketone)s are a class of thermoplastic crystalline polymers that have many desirable properties that make them useful as high-performance engineering materials [153,154]. The poly(ether ke-tone)s with the most useful properties are actually para-linked poly(aryl-ether ketone)s (PAEKs). They have excellent chemical resistance to oxidation and hydrolysis, high thermal stability, and many useful mechanical properties. Unlike some other materials with similar properties they are readily melt processable using conventional equipment. In addition, their mechanical properties are not affected deleteriously by most solvents. These polymers are usually crystalline. PAEKs contain arene groups joined by ether and carbonyl linkages. For example, two commercial poly-(ether ketone)s are PEK and PEEK (Fig. 36). 

Later, the same methodology was applied by Wallow and Novak for the synthesis of water-soluble poly(p-phenylene) derivatives via the poly-Suzuki reaction of 4,4 -biphenylylene bis(boronic acid) with 4,4 -dibromodiphenic acid in aqueous di-methylformamide [26]. These aromatic, rigid-chain polymers exhibit outstanding thermal stability (decomposition above 500 °C) and play an important role in high-performance engineering materials [27] conducting polymers [28] and nonlinear optical materials [29]. 

S. Wang, L. Lu, M.J. Yaszemski, Bone-tissue-engineering material poly(propylene fiimarate) corelation between molecular weight, chain dimensions, and physical properties. Biomacromolecules 7 (6) (2006) 1976-1982, doi 10.1021/bm060096a. 

P. Karimi, A.S. Rizkalla, K. Mequanint, Versatile biodegradable poly (ester amide)s derived from a-amino acids for vascular tissue engineering. Materials 3 (4) (2010) 2346-2368. 

Perez-Rigneiro, J. Viney, C. Llorca, J. Elices, M. Silkworm silk as an engineering material. /. Appl Poly. Sci. 70 2439-2447 (1998). 

Aromatic rigid-rod polymers play an important role in a number of diverse technologies including high-performance engineering materials, conducting polymers, and nonhnear optical materials. The cross-coupling reaction of aryldiboronic acids and dihaloarenes for the synthesis of poly(p-phenylenes) was first reported by Rehahn et al. The method has been extensively applied to water-soluble poly(p-phenylene), planar poly(p-phenylenes) fixed with the ketoimine bonds, poly(phenylenes) fused with polycyclic aromatics,and nonlinear optical materials (Scheme 14). 

S. P. Nunes, K.-V. Peinemann, Poly-imide asymmetric membranes for hydrogen separation influence of formation conditions on gas transport properties. Submitted to Advanced Engineering Materials. 

CeccomUi G, PizzoU M, Scandola M (1993) Effect of a low-molecular-weight plasticizer on the thermal and viscoelastic properties of miscible blends of bacterial poly(3-hydroxybutyrate) with cellulose acetate butyrate. Macromolecules 26 6722-6726 Chanprateep S, Kikuya K, Shimizu H, Shioya S (2(X)2) Model predictive controller for biodegradable polyhydroxyalkanoate production in fed-batch culture. J Bacterid 95 157-169 Chen GQ, Wu Q (2005) The application of polyhydroxyalkanoates as tissue engineering materials. Biomaterials 26 6565-6578... 

Lei, Y., Rai, B., Ho, K.H., Teoh, S.H., 2007. In vitro degradation of novel bioactive poly-caprolactone-20% tricalcium phosphate composite scaffolds for bone engineering. Materials Science and Engineering C-Biomimetic and Supramolecular Systems 27, 293-298. 

Aydin, H.M., Kourush, S., Yilmaz, M., Turk, M., Rzayev, Z., Piskin, E., 2012. The catalyst assisted two stage synthesis of poly(glycerolco-sebacate-co-e-capiolactone) elastomers as potential tissue engineering materials. Journal of Tissue Engineering and Regenerative Medicine. 

Developments in genetic engineering have raised the possibility of producing poly(hydroxyalkanoate) polymers in plants. The plant Arabidopsis thaliana has accepted genes from the bacterial species Alcaligenes eutrophus, which has resulted in plant leaves containing as much as 14% poly(hydroxybutyric acid) on a dry mass basis. Transgenic Arabidopsis thaliana and Brassica napus (canola) have shown production of the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate. If yields can be raised to acceptable levels, plant-synthesized poly(hydroxyalkanoate) materials would represent a tremendous advance in the biosynthesis of polymers because of the ability of photosynthesis to provide the raw materials used to make the polymers. 

Ren L., Tsuru K., Hayakawa S., Osaka, A. In vilro evaluation of osteoblast response to sol-gel derived gelatin-sUoxane hybrids. J. Sol-Gel Sci. Technol. 2003 26 1137 1140 Rhee S.-H. Effect of calcium salt content in the poly(e-caprolactone)/sihca hybrid on the nucleation and growth behavior of apatite layer. In Key Engineering Materials, Vols. 240-242, Bioceramics Vol. 15. Switzerland Trans. Tech. Publ., 2003a, pp. 171 174 (Refer also to the succeeding three papers 175 182, 179-182, 187-190 (2003))... 

Choi, N.Y, S. Kelch and A. Lendlein (2006), Synthesis, shape-memory functionality and hydrolytical degradation studies on polymer networks from poly(rac-lac-tide)b-poly(propylene oxide)-b-poly(rac-lactide) dimethacrylates. Advanced Engineering Materials, 8(5) pp. 439-445. 

Baldwin, D. R, M. Shimbo, and N. P. Suh. 1995. The role of gas dissolution and induced crystallization during microceUular polymer processing A study of poly (ethylene terephthalate) and carbon dioxide systems. Journal of Engineering Materials and Technology 117 (1) 62. doi 10.1115/1.2804373. http //link.aip.org/link/JEMTA8/vll7/ il/p62/sl Agg=doi. 

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