Ageing process polyesters

In conclusion, the different thermal histories imposed to PTEB have a minor effect on the /3 and y relaxations, while the a. transition is greatly dependent on the annealing of the samples, being considerably more intense and narrower for the specimen freshly quenched from the melt, which exhibits only a liquid crystalline order. The increase of the storage modulus produced by the aging process confirms the dynamic mechanical results obtained for PDEB [24], a polyester of the same series, as well as the micro-hardness increase [22] (a direct consequence of the modulus rise) with the aging time. 

Polycondensation, 10 189-190, 191 as an aging mechanism, 23 64 of polyamide plastics, 19 781-782 polyester formation by, 20 390-391 silicone polymerization via, 22 556-558 in the sol-gel process, 23 61-62 Polycrystalline alloys, 13 523 Polycrystalline diamond films, deposition of, 24 744-745... 

Aging does not modify the value of E significantly (except in the close vicinity of Tg), so that aging effects on fracture properties are relatively low in the brittle regime, except if defects are created. This is the case in polyesters (osmotic cracks), where durability is controlled by this process rather than by chain scission or any other structural change at the molecular or macromolecular scale. 

The Arrhenius treatment has been applied to aging studies on rubber (13), to predict the life of a polyester-glass laminate (14), to predict product stability of a thermosetting resin alone and in combination with two additives (15), in permanence tests on paper (16), to multi-component systems in which the principal component is paper (17), and to study the influence of temperature on the relative contributions of the oxygen-independent and oxygen-dependent processes to the total rate of newsprint deterioration (18-20). 

In Table 2 is presented the modulus evolution between 2 to 6 ageing weeks, after processing, for different multiphase systems. We can show that the introduction of fibres into the TPS matrix provokes a drastic decrease of this ageing. This is due to the fibre-matrix interactions which can create a physical 3D network (hydrogen network). These H bonds may stabilize the materials. Besides, we have tested the T PS-fi bres-polyester system to obtain a better water... 

Chem. Descrip. Sat., aliphatic, linear, hydroxyl-terminated polyester diol Uses Polyester for thermoplastic elastomers, laminating adhesives, hot melt and sol n. coatings, and one-shot and prepolymer castables Features PUs exhibit hydrolysis resistance, heat aging and weathering, strong, resilient elastomers, thermoplastic processability, and low temp, properties melts at mod. temps. 

Lactic acid (LA) is one of the top carbohydrate-derived chemicals and it was recently included in BozeU and Petersen s revised selecticai of the top ten sugar-based chemicals [10, 24]. The conversion of carbohydrates into LA via anaerobic fermentation has been known for ages [25]. The first industrial fermentation was developed by A. Boehringer in 1895 and at the present time the global installed production capacity is estimated at 0.5 Mton year [10, 26, 27]. The current fermentation process and its issues will be critically discussed in Sect. 3 in light of the major application of LA today, i.e., as monomer for commercial bioplastic PLA [28]. Besides being used for polyester synthesis, LA is seriously considered as a platform chemical for the synthesis of a diverse range of chemicals such as pyruvic acid, 2,3-pentanedione, and acrylic acid [10, 29]. 

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