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In this contribution, the use of glycidyl methacrylate and styrene copolymers synthesized by nitroxide-mediated polymerization (NMP) as chain extenders of postconsumer Polyethylene terephthalate) waste (r-PET) is described. Our observations revealed that the copolymers synthesized by NMP act as efficient chain extenders for the regeneration of PET waste. Epoxide groups in the copolymers react with PET end reactive groups producing chain extended PET with higher molecular weight and improving performance. The increase in molecular weight of PET waste results in important improvement in both, elongation-at-break, and strength impact. r-PET complex viscosity and rheological moduli are also greatly improved as the epoxide content in the chain extenders increases. The loss tangent and phase angle versus angular frequency plots for chain-extended r-PET reveal that melt elasticity is also improved. These results confirm that use of NMP-synthesized copolymers is a plausible solution for the recycling of PET., INTRODUCTION Polyethylene terephthalate) (PET) is one of the most widely used engineering polymers because of its lightness, low-cost and processing low energy requirements [1]. However, the worldwide excessive production of [...]

This article deals with the characterization of high trans-1,4-poly (butadiene) (TPBD) prepared by means of an anionic polymerization using an initiator composed of alkyl aluminum, n-butyl lithium, and barium alkoxide. By controlling both initiator composition and polymerization temperature, a set of TPBD was prepared with well-known number of 1,4-trans units, molecular weight distribution, and average molecular weight. Analyses by differential scanning calorimetry and diffraction of wide-angle X-rays showed a direct relationship between the microstructure of the polymer and its thermal properties. By increasing the number of 1,4-trans units (70-90%), the crystallinity of the polymer was increased (10-30%); polymers with less than 65% of 1,4-trans units were amorphous, whereas TPBD with a number of 1,4-trans units greater than 80% were polymorphous and presented two endothermic transitions. Summing up, the results presented in this article indicate that cyclohexane solutions of alkyl aluminum, n-butyl lithium, and barium alkoxide allow produce polybutadienes with enough amount of 1,4-trans units to display a regular microstructure that makes the, susceptible to experience-induced crystallization, likewise at a reaction rate similar to that observed for the commercial production of poly (butadiene) with n-butyl lithium. POLYM. ENG. SCI., 49:1-10, 2009. © 2008 Society of Plastic Engineers, INTRODUCTION Poly (butadiene)-Containing polymers are widely used to improve the viscoelastic properties of composed materials such as tires (1-3), engineering plastics (4), adhesives (5), (6), and modified asphalt (7). The [...]

The article discusses the characterization of high trans-1,4-poly(butadiene) (TPBD), examining the synthesis of TPBD via anionic polymerization in determining the effects of 1,4-trans units of the polymers' properties. Poly(butadiene)-containing polymers improve viscoelastic properties of modified asphalt and engineering plastics, the authors state. Other topics include experience-induced crystallization and the direct relationship between a polymer's microstructure and its thermal properties.

A series of controlled microstructure polybutadiene rubbers (PBs) was synthesized via anionic polymerization. Their structure and properties are analyzed by means of GPC, 13C NMR, DSC, and DMA, and compared to the behavior of some commercial high cis rubbers. Thermal analyses results indicate the presence of crystalline domains of different nature in PBs with high cis-1,4 and high trans-1,4 isomers content, while rubbers with high content of vinyl-1,2 units do not show evidence of crystals. A shift in Tg to higher temperatures as vinyl content increases is observed; an expression was found for predicting Tg of rubber from microstructure data. [ABSTRACT FROM AUTHOR]