Polyesters cross-linking

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

Polyester blends Polyester carbonates Polyester containers Polyester-cotton blends Polyester, cross-linked Polyester diols... 

Cross-linked polyester composites have a relatively low coefficient of thermal conductivity that can provide beneficial property retention in thick laminates at high temperatures as well as remove the need for secondary insulation. The coefficient of thermal expansion of glass-reinforced composites is similar to aluminum but higher than most common metals. 

In order to become useful dmg delivery devices, biodegradable polymers must be formable into desired shapes of appropriate size, have adequate dimensional stability and appropriate strength-loss characteristics, be completely biodegradable, and be sterilizahle (70). The polymers most often studied for biodegradable dmg delivery applications are carboxylic acid derivatives such as polyamides poly(a-hydroxy acids) such as poly(lactic acid) [26100-51-6] and poly(glycolic acid) [26124-68-5], cross-linked polyesters poly(orthoesters) poly anhydrides and poly(alkyl 2-cyanoacrylates). The relative stabiUty of hydrolytically labile linkages ia these polymers (70) is as follows ... 

Shellac [124,125] is a natural resin used in very old times for varnishes and moulding compounds. The resin secreted by the lac insect, Kerriar paca, is collected by scraping the shellac-encrusted trees found in southern parts of Asia. It consists of a complex mixture of cross-linked polyesters derived from hydroxy acids, principally aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). From a structural point of view, it appears that this material can be used as a crosslinking agent and/or as a monomer for developing dentrite-like polymers. The question is whether it is possible to produce this material from shellac by controlled hydrolysis. 

Table 5. Values of the parameters and in Eq. (91) for linear and cross-linked polyester chains and for various fractions of amylopectin fractions obtained by a controlled acid hydrolysis [177]...

Fig. 34. Plot of the scaled forward scattering intensity (see Eq. 89) as a function of X=A2-M c for some selected molecular architectures [165]. linear polyester O, A cross-linked polyesters near the ge-point, V weakly cross-linked polyester (see Table 5)...

Figure 35 shows the result for the scaled forward scattering from randomly cross linked polyester chains which were prepared by anhydride curing of phe-nylglycidylether in the presence of bisphenol A diglycidylether [173-175]. The data could be fitted with Eq. (91) with values for g and which are collected in Table 5. 

Phthalic anhydride + Glycerol Cross-linked polyester... 

To produce cross-linked polyesters what is normally present ... 

Allylic plastics, which are produced by the polymerization of diallyl phthalate, have high heat deflection temperatures and high strengths. These cross-linked polyesters have solvent- and corrosion-resistant properties similar to those cited for alkyds. The properties of allylic plastics are shown in Table 15.3. 

Polyesters [2] find use in fibers [poly(ethylene terephthalate), poly(ethylene oxybenzoate), poly(ester ethers), poly(ester amides), etc.] [1], coatings (especially unsaturated polyesters) [4], plasticizers, adhesives, polyurethane base resins, films, etc. Cross-linked polyesters prepared from glycerol and phthalic anhydride (alkyd resins) have been reviewed [20], High-melting poly aryl esters have been investigated for high-temperature applications. 

G 5. Ghanem, N. A. Studies in the cross-linked polyesters. III. The composition of styrene cross-linked polyester using 14C-labelled maleic anhydride. Makromol. Chem. 36, 109 (1960). 

The most important polymeric matrices are linear and cross-linked polyesters, epoxy resins and linear and cross-linked polyimides the most important reinforcements are high-performance polymeric fibres and filaments (for polymeric composites), filaments of refractory metals and inorganic materials (E-glass, A12C>3, B, BN, SiC and Carbon) and whiskers (fibrillar single crystals of A1203, B4C, WC, SiC and C, exclusively for reinforcement of metals). 

B glass fibre varnish treated glass fibre textiles synthetic resin varnishes cross-linked polyester resins... 

J. A. Hiltz, Pyrolysis-gas chromatography mass-spectrometry identification of styrene cross-linked polyester and vinyl ester resins, J. Anal. Appl. Pyrolysis, 22, 113-128, (1991). 

FDA 1998 regulates BP as an indirect food additive. It is permitted as a catalyst not exceeding 2% of the finished resin, and as an optional adjuvant in the production of cross-linked polyester resins intended for repeated use in contact with food 21CFR177.2420. EPA Reportable Quantity lOlbs. For MEK Peroxide ACGIH TLV (ceiling) 0.2 ppm (1.5 mg/m3) and OSHA PEL (ceiling) of 0.7 ppm (5 mg/m3). 

Considered a priority pollutant and is regulated by the federal Clean Water Act, RCRA and Superfund. FDA approved under 21CRF175.105 - Adhesives 175.300 - Resinous and Polymeric Coatings 176.170 - Components of Paper Paper-board in Contact with Fatty or Aqueous Food 175.180 - Components of Paper Paperboard in Contact with Dry Food 177.2420 - Cross-linked Polyester Resins (as solvent) and 178.3740 - Polymeric Substances (Extraction limitations). 

Photooxidation and Photostabilization of Unsaturated Cross-linked Polyesters... 

In the TEM samples, the rubber domains are uniformly distributed and on the order of a few hundred angstroms in size. The micrographs also show the presence of domains that have no rubber in them. The rubber-free domains probably contain polyester and epoxy that have reacted, but it is not possible to confirm this possibility. Styrene-cross-linked polyester has a Tg of 185 °C. When the epoxy is introduced in a 1 2 ratio (epoxy-.polyester), Tg de-... 

The technique is also applicable to cross-linked polyesters made from unsaturated polyesters and styrene, as in the sheet-molding compounds used in cars and boats.165 The ester linkages were broken by treatment with ethanolic potassium hydroxide or by ethanolamine. The latter was preferred, because no waste salts were formed by neutralization, as they were with the potassium hydroxide. The filler and glass fibers could be removed at this stage, if desired. The alcohol-soluble product was suitable for use in new bulk-molding compounds. A method that allows the cross-linked polyester to recycled back into the same use... 

The large variety of PHAs, which is due to the many constituents that are incorporated, can be further diversified by chemical reactions or by irradiation. These measures chemically modify the side chains or cross-link polyester chains (for review see [15]). 

Solvents used for paint removal are able to dissolve or considerably swell physically drying binders (e.g., vinyl chloride copolymers, cellulose nitrate, polyacrylates) and chemically cross-linked coatings (e.g., oil-based paints, dried alkyd resins, cross-linked polyester-melamine resins, cross-linked epoxy and isocyanate coatings) [14.237]. A combination of dichloromethane with low-boiling ketones or esters is particularly suitable. Small amounts of high-boiling solvents with a low volatility (e.g., tetrahydronaphthalene, solvent naphtha, methyl benzyl alcohol, or benzyl alcohol) are added to these mixtures to retard evaporation and increase the solvency. Modern paint removers do not contain chlorinated hydrocarbons, they are formulated on the basis of high boilers (e.g., dimethylformamide, dimethyl sulfoxide, propylene carbonate, and yV-methylpyrrolidone) in combination with alcohols and aromatics, or consist of aqueous, frequently alkaline or acidic systems. 

By adjusting postpolymerization temperature and cross-linking (curing) time, the mechanical properties, degradation profiles, and surface energies of the cross-linked polyester networks, POC can be tuned to fit a wide range of tissue engineering applications (see Table 16.2) [2,16-18,35,50-56]. An increase in postpolymerization temperature and cross-... 

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