Preparation And Performance Study Of Recycled Polyester Industrial Yarn

With the rapid development of polyester industry, the recycling of largequantities of polyester waste pruducing during processing and post-consumer drawsworldwide attention. The main recovery methods are physical and chemical method.The physical method is widely used in industry due to its crafs simple and lessinvestment. While only a few foreign polyester companys achieved commercialoperation using chemical method due to its process complex and large investment.At present our country，s recycling polyester products are mainly fiber.AlthoughChina is the top producing country of recycled polyester, however, due to thehomogeneity of products and blind expansion of production capacity the profits ofrecycled polyester fiber reduces greatly.In order to increase the added value,it isurgent to enhance its differences. At present the reports of pruducing industrial yarnusing polyester waste fiber is few. In this paper, the research of producing industrialyarn using polyester waste fiber is studied in order to make it meet the standard ofindustrial yarn.In this thesis, we adopted advanced granulation equipment from European forgranulation of polyester industrial waste fiber, and studied the influence of screwtemperature, vacuum and screw speed on the intrinsic viscosity, the carboxyl endgroup and b values. Studies indicated that the temperature was too high or too lowwould result in poor physical properties of recycled polyester, and the better thevacuum the better the effect of suction of oil and water, the screw speed was too fastor too slow would lead to poor physical properties. Integrating three factors, gotoptimum granulation process:270℃,0.05bar and165r/min. In this condition,intrinsic viscosity was0.72dl/g, carboxyl end group was35.4mol/t, b is9.5. Thethermal properties of recycled polyester was investgated by DSC and TGA, resultsshowed that the differences of thermal transition temperature is small betweennative and recycled polyester, indicating its physical properties consistent withnative polyester,the degradation temperature of recycled polyester was near350℃,and slightly lower than native polyesters, meeting the subsequent processing requirementsTackifying reaction of recycled polyester was acted in vacuum drum andthe crystallization properties of the recycled polyester after Tackifyed were studied. The results showed that the intrinsic viscosity increases with the extension of reaction time. the reaction temperature was higher, the faster the reaction rate, needing less time for abtaining the same intrinsic viscosity, but the latter spinning processing and the fiber properties indicated that the reaction should be acted in relatively low temperatures with longer time to get good quality.The non-isothermal crystallization kinetics was investgated by Jeziorny equation,the results showed that Rami exponent of recycled polyester wasbetween2.4to3.03, while the native polyester is between2.0to2.6, indicating that the crystal nucleation of the recycled and native polyesters was homogeneous and heterogeneous nucleation, and the crystallization of recycledpolyester was more complex due to with more impurities,even in a high cooling rate the crystallization could occur.The influences of stretch ratio, intrinsic viscosity, spinneret specificationsand mixing ratio between recycled and native polyester on the fiber performance were investgated. The results showed that the fracture strength of polyester yarn could be effectively improved by increasing draw ratio, so as to the intrinsic viscosity increas-ing.because of some flaws in recycled polyester, the spinning of the same specifications yarn using recycled polyester should be used spinneret with smaller draw down ratio. so the spinning of1000Dyarn uses0.45*1.35/192f specifications spinneret,0.6*1.2/192f for1300D. The join of native sliced can effectively improve the quality of the melt. when the ratio increased to1:1, the intensity increased from7.04cN/dtex to7.45cN/dtex, the strength of recycled polyester filament has reached the requirements for the industrial polyester yarn, but the properties of the same specifications is poor compared with native polyeser yarn.