Polyesters description

However, dendrimeric and hyperbranched polyesters are more soluble than the linear ones (respectively 1.05, 0.70, and 0.02 g/mL in acetone). The solution behavior has been investigated, and in the case of aromatic hyperbranched polyesters,84 a very low a-value of the Mark-Houvink-Sakurada equation 0/ = KMa) and low intrinsic viscosity were observed. Frechet presented a description of the intrinsic viscosity as a function of the molar mass85 for different architectures The hyperbranched macromolecules show a nonlinear variation for low molecular weight and a bell-shaped curve is observed in the case of dendrimers (Fig. 5.18). 

A description is given of a comparative study of the glycolysis of PETP waste soft drinks bottles by various mixtures of EG and DEG with subsequent polyesterification of the glycolysed products by maleic anhydride in order to obtain unsaturated polyesters suitable for the production of varnishes. The processing characteristics such as viscosity, exotherm temperatures of curing, compatibility of resins with monomers was investigated with respect to the type and amount of reactive monomers. The mechanical properties of varnishes produced were analysed. 13 refs. 

The reinforcement of rubbers using nylon, rayon, vinyl, and polyester fibers was reported by various authors [10,58,73-75]. Because of the design flexibility and suitable end-use applications, high-performance fibers such as glass, carbon, and aramid also find extensive applications in short fiber-reinforced mbbers. A brief description of some of the major high-performance fibers commonly used in short fiber-rubber composites is given below ... 

For those familiar with polymer chemistry, polyurethane may be a confusing term. Unlike polyethylene, the polymerization product of ethylene, a polyurethane is not the result of the polymerization of urethane. To add to the confusion, a urethane is a specific chemical bond that comprises a very small percentage of the bonds of a polyurethane. Since we are interested in chemical and physical effects, polyether or polyester is a more descriptive term for the most common bond in a polyurethane. Despite this complication, it is instructive to begin by talking about the methane bond from which the polyurethane name is derived. The general structure or bond that forms the basis of this chemistry is the urethane linkage shown in Figure 2.1. 

The dynamic RIS formalism is used to calculate the rate of first passage from non-excimer-forming conformations to excimer-formlng conformations in seven aromatic polyesters with different flexible spacers between the aromatic rings. The equilibrium chain statistics provides a good description of the relative excimer population for these polyesters, even at times where the dynamic contribution is significant. 

Parameters required for the description of polyesters I are taken from a recent paper (Abe, A, J. Am. Chem. Soc. 1984, 106, 14) which dealt with the dipole moments of dialkyl esters of dicarboxylic acids. Since the ester groups are all assumed to be in the trans configuration, short-range interactions between consecutive rigid cores are unimportant. As for the rotation around the O-C — C-C bond, the six-state scheme (termed model I in the above paper) is employed. The statistical weight parameter a representing the relative importance of the reversed ester conformations with respect to the normal ones is set equal to unity. The three-state scheme (termed model II) proposed alternatively in the above reference is examined for chains with n = 5 and 6 for comparison. In this model the C O /CC eclipsed form is assumed to be intrinsically more stable than the C 0 /CH form a stabilzation energy E( 1) of 5.0 kj mol-1 is adopted. 

For commodity applications, there are four major classes of resins that are used in FRP applications. They are phenolic resin, epoxy resin, unsaturated polyester resin, and epoxy vinyl ester resins. A more complete description of these types of resins and their many variations can be found in Handbook of Thermoset Plastics. This is not a comprehensive list of resins used in composite manufacture, as commodity materials like polyurethanes and isocyanurate resins are sometimes used as well to make FRP parts. However, these materials are not covered in this chapter owing to their limited use, but, the principals of fire safety that apply for the resins described subsequently apply to these materials as well. 

The oxidation of cyclohexanone by nitric acid leads to the generation of nitrogen dioxide, nitric oxide, and nitrous oxide. The first two gases can be recycled for the synthesis of nitric acid. Nitrous oxide, however, is an ozone depleter and cannot be recycled. Indiscriminate nitrous oxide emission from this process is therefore the cause of considerable concern. As shown by 8.9, part of the cyclohexanone can also be converted to the corresponding oxime and then to caprolactam—the monomer for nylon 6. Phthalic acids are one of the monomers for the manufacture of polyesters. As shown by Eq. 8.10, it is made by the oxidation of p-xylene. A general description of polyamides (nylons) and polyesters are given in Section 8.4. 

Chemical Description Aromatic Bromine Aliphatic Chlorine Lower smoke and lower cost than brominated flame retardants, used to flame retard polypropylene, polyethylene, SBR, unsaturated polyesters and fabrics. 

In a similar report utilizing triethylene glycol dimethacrylate, the polymer was described as a linear polyester.330 Again, this description is probably incomplete, though it is possible at high catalyst loadings to prepare methacrylic dimers. Under ideal conditions, this would lead to the linear, unsaturated polymer 97. 

Description The common method for the production of DMT from p-xylene and methanol consists of four major steps oxidation, esterification, distillation and crystallization. A mixture of paraxylene (PX) and PT-ester is oxidized with air in the presence of a heavy metal catalyst. All useful organics are recovered from the offgas and recycled to the system. The acid mixture resulting from the oxidation is esterified with methanol to produce a mixture of esters. The crude ester mixture is distilled to remove all the heavy boilers and residue produced the lighter esters are recycled to the oxidation section. The raw DMT is then sent to the crystallization section for removal of DMT isomers and aromatic aldehydes. This purification produces DMT that meets world-market specifications and is preferred in some polyester applications. Byproducts are recovered for sale or burned for fuel value, and usable intermediate materials are recycled. 

Source description Dried deposit ofbarium chloride on a filter-paper disk sealed between two layers of polyester tape that are supported on an aluonnuna annulus ... 

We can classify the different biodegradable and bio-based polymers into two major families agropolymers (categoiy a) and biodegradable polyesters (categories b and c). To illustrate the latter, the next section focuses on the description of biodegradable polyesters, from synthesis to application. 

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