SYNOPSISPoly(viny1 chloride) (PVC), PVC/chlorinated polyethylene (CPE), PVC/oxidized polyethylene (OPE), and PVC/CPE/OPE compounds were prepared in a Haake torque rheometer at various temperatures, rotor speeds, and totalized torques (TTQ). The fusion characteristics of these PVC compounds (fusion time, fusion torque, and fusion temperature) were studied. Longer fusion time results in higher fusion temperature. Higher fusion temperature results in lower fusion torque. The fusion time of PVC/OPE compounds is the longest among these PVC blends. However, the fusion time of PVC/CPE/OPE compounds is the shortest among these PVC blends. The fusion time of the PVC/CPE/OPE compound is significantly different from those of PVC, PVC/OPE, and PVC/CPE compounds at the medium starting temperature and the medium rotor speed. Scanning electron microscopy (SEM) analyses successfully revealed the surface morphological changes of the fusion of PVC, PVC/OPE, PVC/CPE, and PVC/CPE/OPE compounds. The lubrication mechanisms of these PVC compounds have also been postulated. 0 1995 John Wiley & Sons, Inc. I NTRO DUCT10 NPoly(viny1 chloride) (PVC) was first found and characterized more than 120 years ago, but, due to its poor thermal stability, making processing diEcult, it was not until about 1930 that people began producing commercial PVC products.' To overcome its poor thermal stability and photochemical degradation, researchers developed suitable stabilizer systems,' heat stabilizers (e.g., lead compounds, organotin compounds, and other metal compounds), and light stabilizers ( e.g., phenyl salicylate, oxalic anilide, and phenyl formamidine) to solve these problems and PVC is now one of the world's highestvolume synthetic polymers.Chlorinated polyethylene (CPE) is commonly used as an impact modifier of PVC. The CPE used as impact modifiers in PVC are produced by chlorinating high-density polyethylene in aqueous ~l u r r y .~The chlorine distribution and chlorine content of CPE are major factors in the mixing of CPE
SYNOPSISRigid poly(viny1 chloride) (PVC) compounds were prepared in a Haake torque rheometer using various blending conditions. The fusion levels of processed compounds were evaluated by a capillary rheometer and differential scanning calorimetry (DSC), based on the entrance pressure drop and the heat of fusion, respectively. S-shaped fusion curves were obtained. Starting temperature of the mixer, rotor speed, and totalized torque are the three major factors that affect the fusion level of PVC compounds blended in the Haake torque rheometer. All three parameters have a significant effect; however, totalized torque has the greatest effect and this can be characterized using a torque rheometer. Both capillary rheological and DSC thermal analysis can be applied to determine the fusion level of a PVC compound. The morphological changes of the various fusion processes were characterized by scanning electron microscopy (SEM). crystallinity. To achieve good mechanical properties, grain boundaries must be eliminated and the microparticles must be altered and compacted together. After significant interdiffusion, the boundaries of submicroparticles disappear, and a three-dimensional network of polymer chains is formed. This is referred to as the fusion, or gelation, of poly(viny1 chloride) (PVC) -2,3 Benjamin4 reported that a PVC product with the fusion level between 60 and 80% has an optimum value of impact ductility.
The crystallization kinetics of syndiotactic polystyrene (SPS) were studied using nonisothermal DSC analysis. Crystallization rates and half‐times were determined from the glass transition temperature (∼ 100°C) up to the melt temperature (∼ 270°C) for various molecular weight SPS polymers. The results suggest that the crystallization rate of SPS is molecular weight dependent. These results are also compared with previously determined crystallization kinetics of high density polyethylene. The maximum crystallization rate of high density polyethylene is approximately ten times greater than that of SPS.
In 2012, the National Science Foundation (NSF) created a new cross-directorate initiativeSustainable Chemistry, Engineering, and Materials (SusChEM)within its Science, Engineering and Education for Sustainability (SEES) portfolio. SusChEM aims to support the discovery of new science and engineering that will provide humanity with a safe, stable, and sustainable supply of chemicals and materials sufficient to meet future global demand. While NSF has historically supported research in this area, the SusChEM effort elevates this interest to a priority. In particular, NSF will support the discovery of new science and engineering that will (1) improve the harvesting and processing of natural resources, (2) develop replacement and substitute chemicals and materials for those that are scarce, toxic, and/or expensive, (3) extend the lifetime of materials through improved durability, (4) reduce energy consumption through improved catalysis, and (5) discover low-energy means of recycling, repurposing, recovering, and reusing chemicals and materials. This article provides an overview of the sustainability challenges that the mathematical, physical, and geological science and engineering communities are well poised to address and presents the National Science Foundation's vision of the SusChEM initiative.
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