Polymer stabilization their esters

Stability of the polymers at usual storage conditions depends on their molecular structure. Several studies have documented that methacrylic acid copolymers are the most stable polymers as bulk and finished dosage form (Figure 3) [24], The limiting factor of stability of the polymers is their ester function, which tends to... 

Aromatic amorphous or semicrystalline polyamides, PARA, such as copolyamide from caprolactam, hexamethylenediamine and iso- and tere-phthalic acids, PA-6IT6, or copolyphthalamide, PPA, are frequent components of polymer blends. Their advantage is low permeability to liquids and gases, stiffness and high HDT. Several blends of PP with PARA have been described, e.g. with either PP-MA, PE-MA, or PP grafted either with acrylic acid or GMA. Usually, these blends must be heat stabilized with phosphite ester or hydrazine. The alloys are often reinforced by addition of glass fibers and talc. 

Lefevre, C-, et al, Comparative degradation by micro-oiganisms of tere-phthalic acid, 2,6-naphthalene dicarboxylic acid, their esters and polyesters. Polymer Degradation and Stability, 64(1) p. 9.1999. 

Block copolymers can contain crystalline or amorphous hard blocks. Examples of crystalline block copolymers are polyurethanes (e.g. B.F. Goodrich s Estane line), polyether esters (e.g. Dupont s Hytrel polymers), polyether amides (e.g. Atofina s Pebax grades). Polyurethanes have enjoyed limited utility due to their relatively low thermal stability use temperatures must be kept below 275°F, due to the reversibility of the urethane linkage. Recently, polyurethanes with stability at 350°F for nearly 100 h have been claimed [2]. Polyether esters and polyether amides have been explored for PSA applications where their heat and plasticizer resistance is a benefit [3]. However, the high price of these materials and their multiblock architecture have limited their use. All of these crystalline block copolymers consist of multiblocks with relatively short, amorphous, polyether or polyester mid-blocks. Consequently they can not be diluted as extensively with tackifiers and diluents as styrenic triblock copolymers. Thereby it is more difficult to obtain strong, yet soft adhesives — the primary goals of adding rubber to hot melts. 

In a most recent paper [418] the preparation of corn fiber arabinoxylan esters by reaction of the polymer with C2-C4 anhydrides using methanesul-fonic acid as a catalyst is described. The water-insoluble derivatives with high molecular weight showed glass-transition temperatures from 61 to 138 °C, depending on the DS and substituent type. The products were thermally stable up to 200 °C. Above this temperature their stability rapidly decreased. 

Lipases can catalyze hydrolysis of esters, synthesis of esters, trans-esterification, and synthesis of some polymers. They have been applied in many fields including the food industry, fine chemistry, and the pharmaceutical industry. The low stability of native lipases makes them unsuitable for industrial applications. In order to use them more economically and efficiently, their operational stability can be improved by immobilization. Numerous efforts have been focused on the preparation of lipases in immobilized forms involving a variety of both support materials and immobilization methods [278],... 

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