High-molecular-weight resins

These resins are referred to as cationic resins . Paper with improved wet strength may be obtained by adding an ionic resin at the beater stage of a papermaking operation. For the best results a high molecular weight resin is required. 

Epoxy ester Epoxy esters are a type of alkyd where a high molecular weight resin is reacted with alkyd resin. The curing mechanism remains primarily through the oil-oxidation reaction and their properties are in no way similar to the chemically reacted epoxies. They have similar properties to alkyds although with improved chemical resistance but inferior appearance. They form a reasonably hard, oil-resistant coating, which can sometimes be suitable for machinery enamels, but are primarily for interior use, since they tend to chalk rapidly on exteriors. Their best use is for chemical or water resistance where circumstances dictate that finishes that are more superior cannot be used. 

Generally, systems developed in the USA favour a combination of polyethylene with either butyl-rubber or hot-applied mastic adhesives, the latter consisting of a blend of rubber, asphalt and high molecular weight resins. In European and Far East coating plants, epoxy type primers and hard ethylene copolymer adhesives have been successfully employed. 

Molecular weight increase is performed by modification of the molar balance between the reactants so BTDE, MDA, NE and PMR-30, PMR-50, PMR-75 with respective theoretical Mns of 3000,5000,7500 Da were prepared and compared (Table 4) [104]. The Tg of the crosslinked material decreases as the Mn increases but the oxidative stability is better for the high molecular weight resins. 

High-molecular-weight resins to lower crosslink density... 

Chemical functionalization of the thermoplastics was found to improve toughness without such detractions. High-molecular-weight resins based on amine-terminated PES oligomers or chain extension of bismaleimide resin with the same amine-terminated PES were found to have improved fracture resistance and reduced thermal shrinkage.14 Also a mechanism was found to toughen cyanate esters by incorporating epoxy resins, which can react with the ester.15... 

There is some tendency for the 6-aminohexanoic acid to recyclize, which contributes to a crude product containing about 90% useful high-molecular weight resin and 10% caprolactam and oligomers. To obtain optimum properties the crude product may be heated at 180-200°C in a partial vacuum to form useful polymer from the residual oligomers. Or the mixture may be leached with water at 80-85°C to wash out the somewhat soluble caprolactam and oligomers from the product. Einished nylon 6 resin, poly (6-aminohexanoamide), has a melting point of 223°C, somewhat lower than... 

If the hydroxyl groups present are not very reactive, as in the high molecular weight resins, then it would be assumed that the first group on the diamine would react first, followed by the secondary amine and the second primary amine group. 

Finally, there are very high molecular weight resins and asphaltenes which contain a variety of aromatic and heterocyclic structures. Resins are the lower molecular weight, <1000 amu, species, whilst asphaltenes result from linking together many other structures and have exceptionally high molecular weights. 

Although attempts to prepare high-molecular-weight resins for fibers [4] have been reported, no commercial use of polythioesters for this or any other applications is known. 

Since ancient times, naturally occurring polymers have been used by mankind for various purposes. Meat (protein, see Chapter 31) and corn (polysaccharide, see Chapter 32) are important sources of food. Wool and silk, both proteins, serve as clothing. Wood, the main component of which is cellulose, a polysaccharide, is used for building and fire-making. Amber, a high-molecular-weight resin, was worn by the Greeks as a jewel. The use of asphalt as an adhesive is mentioned in the Bible. 

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