International audienceThis work aims at simulation by particle tracking the local residence time distributions (RTDs) of a co-rotating twin-screw extruder using computational fluid dynamics. Simulated results follow reasonably well the trend of experimental results obtained by an in-line measuring instrument for different screw configurations and feed rates. To analyze the distributive mixing performance and overall efficiency of different types of kneading discs (KDs), mixing parameters such as area stretch ratio, instantaneous efficiency, and time-average efficiency are calculated. Among KDs with stagger angles 45°, 60°, and 90°, the 90/10/64 with disc gaps is most efficient in terms of distributive mixing. The effects of the disc width and disc gap on the local RTD and distributive mixing are also discussed. This provides a numerical tool for assessing point-by-point information on the local RTD, flow, and mixing along the screw extruder. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineer

The structure−property evolution of commercial poly(ethylene terephthalate) (PET) fibers obtained from the different drawing and heat-setting stages in industrial processing was systematically investigated. Upon combination of thermal analysis (DSC and DMA) with crystallization and orientation (WAXD and SAXS), the variation of crystallization and microstructures mainly containing lamellar and microfibrillar crystals following the processes were discussed in connection with properties. Results indicate the significant tenacity increase of fiber in the drawing process is mainly attributed to the orientation development of the interlamellar amorphous region, the interfibrillar extension of amorphous molecular chains, and its entanglement with the lamellae. Accordingly, a decline of shrinkage can be seen as a fact of the coiling of amorphous molecular chains, the formation of rigid amorphous fraction, and the increase of crystallinity. Thus, a new four-phase model has been proposed to clarify the structure−property relationships of the commercial PET industrial fibers.

A nonwoven fabrics based on 3‐isopropenyl‐α,α′‐dimethylbenzene isocyanate grafting polypropylene (PP‐g‐TMI) was modified with dopamine both by covalent reaction and by polymer layer deposition involving straightforward self‐polymerization (PP‐PDA) to improve the hydrophilic property of polypropylene nonwoven fabrics. The functionalized surfaces were characterized by structural and morphological analysis combined with the rheological property to confirm the location and dispersion of PDA. The water contact angle, water absorption ability, and the vapor transmission rate were examined to evaluate the hydrophilicity performance of modified materials. It was found that the aggregated small particles on PP nonwoven fabric could result in a heterogeneous surface, and the modified PP nonwoven fabric with dopamine indicated a lower water contact angle and better hydrophilicity that the water absorption ability nearly soared to ten times that of PP nonwoven fabric without PDA.

Abstract:The blending of aliphatic polyolefins and aromatic poly(ethylene terephthalate) (PET) based on different intrinsic viscosities (IV) was conducted in a torque rheometer. The comparison of blend components in terms of low density polythene (LDPE) and polypropylene (PP) in blending with PET was investigated, and the effects of the IV and proportion of PET on polymer blends are discussed in detail. Polymer blends with or without compatibilizer were examined by using a differential scanning calorimeter, thermogravimetric analyzer, rotary rheometer, field-emission scanning electron microscopy and a universal testing machine. It was found that the blending led to an increase in processability and a decrease in thermal stability for blends. The morphological analysis revealed that the incompatibility of blends was aggravated by a higher IV of PET, while this situation could be improved by the addition of compatibilizer. Results showed that there was an opposite effect for the tensile strength and the elongation at break of the polymer blend in the presence of a compatibilizer, wherein the influence of IV of PET was complicated.

Stress analysis and deformation prediction have always been the focuses of the field of mechanics. The accurate force prediction in plate deformation plays important role in the production, processing and performance analysis of materials. In this paper, we propose an ARIMA-FEM method, which can be used to solve some mechanical problems of 2D porous elastic plate. We have given a detailed theory and solving steps of ARIMA-FEM. In addition, three numerical examples are given to predict the stress–strain of thin porous elastic metal plates. This article uses CST, LST and Q4 elements to discrete the rectangular plates, square plates and circle plates with holes. As for variable force prediction, this paper compared with linear regression, nonlinear regression and neural network prediction, and the results show that the ARIMA method has a higher prediction accuracy. Furthermore, we calculate the numerical solution at four mesh scales, and the numerical convergence is consistent with the theoretical convergence, which also shows the effectiveness of our method. The image smoothing algorithm is applied to keep edge information with high resolution, which can more concisely describe the plate internal changes. Finally, the application scope of ARIMA-FEM, model expansion, superconvergence analysis and other issues have been given enlightening views in the discussion section. In fact, this algorithm combined statistics and mechanics. It also reflects the knowledge integration of interdisciplinary and uses it better to serve practical applications.