Poly processing techniques

The easy processibility of hydroxyproline-derived polyesters is in marked contrast to the unfavorable material properties of most conventional poly (amino acids) that cannot usually be processed into shaped objects by conventional polymer-processing techniques (7). Furthermore, since the synthesis of poly(N-acylhydroxyproline esters) does not require the expensive N-carboxyanhydrides as monomeric starting materials, poly(N-acylhydroxyproline esters) should be significantly less expensive than derivatives of conventional poly(hy-droxyproline). 

The first member of this series, poly(CTTE), was a high-melting and virtually insoluble polymer that could not be processed into shaped objects by any one of the conventional polymer-processing techniques. In this respect, poly(CTTE) was highly reminiscent of conventional poly(L-tyrosine). 

The corresponding polyiminocarbonates (Figure 5) were prepared first, using recently developed polymerization procedures (5). Poly(Dat-Tym iminocarbonate), the polymer carrying no pendent chains at all, was an insoluble material. Thermal processing techniques could not be used due to the low thermal stability of the polymer in the molten state. Thus poly(Dat-Tyr iminocarbonate) was a virtually non-processible material without practical applications. 

World-wide consumption of PVC [poly(vinyl chloride)] has increased dramatically in the past few years. It has now exceeded 8 billion lbs annually. The production of VCM (vinyl chloride monomer) has also been expanded to meet the PVC demand. Future trends for VCM and PVC pro-ductions for the next five years can be forecast on the basis of the raw materials sources, the different process techniques in manufacturing VCM and PVC, and their relative economics, technical merits, and limitations. VCM will be produced principally through the ethylene route by fluid-bed oxyhydrochlorination of ethylene and thermal cracking of ethylene dichloride. PVC will be produced by various processes resulting in more specialized PVC varieties tailored for specific end markets and new processing technologies. 

The Octol process, developed jointly at Marl by Hals and UOP for the specific production of octenes from /i-butenes. is a more recent version of the technique employing phosphoric acid, the so-called Catalytic Condensation Process or Poly Process The silica/alumina catalyst always appears to be used in a fixed bed in this case, but... 

Boland ED et al (2001) Tailoring tissue engineering scaffolds using electrostatic processing techniques a study of poly(glycolic acid) electrospinning. J Macromol Sci, Pure Appl Chem 38(12) 1231-1243... 

FIGURE 5.2.3 Two-dimensional grazing incidence x-ray diffraction patterns of poly(3-octyl thiophene) thin films cast on SiOj/Si substrates with various solution processing techniques from different solvents (a) chloroform (CHCI3) (b) toluene (c) tetrahydrofuran (THF) (d) methylene chloride (CH2CI2). (From Yang, H., unpublished data, 2006. With permission.)... 

Polyferrocenylsilanes can be fabricated into films, shapes, and fibers using conventional polymer processing techniques. The dimethyl derivative 3.22 (R=R = Me), which has been studied in the most detail, is an amber, film-forming thermoplastic (Fig. 3.7a) which shows a Tg at 33°C and melt transitions (T ) in the range 122-145 °C. The multiple melt transitions arise from the presence of crystallites of different size, which melt at slightly different temperatures [65, 100). Poly(ferrocenyldimethylsilane) 3.22 (R=R =Me) can be melt-processed above 150°C (Fig. 3.7b) and can be used to prepare crystalline, nanoscale fibers (diameter 100 nm to 1 pm) by electrospinning. In this method, an electric potential is used to produce an ejected jet from a solution of the polymer in THF, which subsequently stretches, splays, and dries. The nanofihers of different thickness show different colors due to interference effects simUar to those seen in soap bubbles... 

Using appropriate anhydrous processing techniques, which prevent the hydrolysis of the active ester end groups, then allows for the manufacture of biomimetic scaffolds for tissue engineering.Further commonly used processing techniques for the overall class of poly(a-hydroxy esters) include electro-spinning for the manufacture of fibers and emulsion/solvent... 

Poly(vinylidene chloride) (PVDC). The homopolymer is intractable in the conventional plastics processing techniques. For this reason, copolymers of vinylydene chloride with vinyl chloride or terpolymers with vinyl chloride and acrylonitrile are used. Due to its exceptionally low vapour, gas, and aroma permeability, PVDC films are used for packaging and for the barrier layer in composite films. Paper varnished by PVDC is a widespread packaging material. Trade names Diofan (FRG), Ixan (B), Saran (USA). 

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