Polymer Engineering and Science
1548-2634
0032-3888
Mỹ
Cơ quản chủ quản: WILEY , John Wiley & Sons Inc.
Lĩnh vực:
Polymers and PlasticsMaterials ChemistryChemistry (miscellaneous)
Các bài báo tiêu biểu
Structure‐Property relationships in polyacrylate‐poly(urethane‐urea) interpenetrating polymer networks Abstract Interpenetrating polymer networks of polyacrylate (A) and poly (urethane‐urea) (U) were prepared by mixing lattices of self‐curing polyacrylate and urethane‐urea prepolymer followed by subsequent curing of each network. The structures of the mixtures were analyzed by the dynamic viscoelasticity and the electron microscopy. It was found that a phase inversion occurred from the “U‐phase particles in A‐phase matrix” to the “A‐phase in U‐phase matrix” at A/U ≑ 30/70 as the U‐phase content increases. With increasing A‐phase content, tensile strength started to increase and elongation‐to‐break becomes almost constant after the A‐phase formed a continuous phase. This implies that the tensile properties are closely related to the morphological features.
Tập 10 Số 6 - Trang 327-331 - 1970
Smart sunglasses based on electrochromic polymers Abstract Smart sunglasses based on electrochromic polymers are proposed and developed in this study. This article discusses the design, processing, and the optical and electrical performance of a prototype smart sunglasses based on cathodic electrochromic (EC) polymers, which show several merits compared with traditional materials for sunglasses lens as well as other smart window materials. It is a multilayer design of device. The conjugated polymer, poly[3,3‐dimethyl‐3,4‐dihydro‐2H‐thieno [3,4‐b] [1,4]dioxepine] (PProDOT‐Me2 ), is utilized as the electrochromic working layer. The counter layer of the device is vanadium oxide (V2 O5 ) film, which serves as an ion storage layer. There is also a polymer gel electrolyte acting as the ionic transport layer, sandwiched between the working and counter layers. The characteristics of the prototype device are reported, including transmittance (%T ), driving power, response time, open circuit memory, and lifetime. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Tập 48 Số 11 - Trang 2224-2228 - 2008
Chain extension and degradation during reactive processing of PET in the presence of triphenyl phosphite Abstract Poly(ethylene terephthalate) (PET) is chemically degraded during processing and/or using by a number of sources including temperature, humidity, and ultraviolet radiation. As a consequence, a large loss in engineering properties is observed when PET products are recycled. To overcome this problem, various types of chain extenders were developed in an attempt to recover the polymer molecular sizes by chemical reactions during processing. This work investigates the use of triphenyl phosphite (TPP) as a chain extender of virgin and recycled PET. Compounds with 1 and 3% of TPP were prepared and processed under various conditions using a torque rheometer. An increase in torque during mixing was associated with chain extension reactions whereas the observed decrease in torque afterwards was due to chemical degradation. The optimum processing conditions were reached (260°C, 1% chain extender), with a maximum in chain extension and a minimum in subsequent degradation. An important finding of this work was that the chemical degradation of chain extended PET occurs very easily during storage and it was considered to be a result of the influence of by‐products of TPP reaction with PET. The extraction of these products with acetone was shown to be quite effective, with a considerable stability during storage. This work also showed that the recycled PET is much less able to react with TPP in comparison with the virgin polymer. POLYM. ENG. SCI., 47:2155–2163, 2007. © 2007 Society of Plastics Engineers
Tập 47 Số 12 - Trang 2155-2163 - 2007
Crystallization kinetics of poly(L‐lactide) in contact with pressurized CO<sub>2</sub> Abstract The effect of CO2 on the isothermal crystallization kinetics of poly(L‐lactide), PLLA, was investigated using a high‐pressure differential scanning calorimeter (DSC), which can perform calorimetric measurements while keeping the sample polymer in contact with pressurized CO2 . It was found that the crystallization rate followed the Avrami equation. However, the crystallization kinetic constant was changed depending upon the crystallization temperature and concentration of CO2 dissolved in the PLLA. The crystallization rate was accelerated by CO2 at the temperature in the crystal‐growth rate controlled region (self‐diffusion controlled region), and depressed in the nucleation‐controlled region. CO2 has also decreased the glass transition temperature, T g T m 2 ‐induced change in the crystallization rate can be predicted from the magnitudes of depression of both T g 2 were also investigated using a wide angle X‐ray diffractometer (WAXD). The resulting crystallinity of the sample was increased with the pressure level of CO2 , although the presence of CO2 did not change the crystalline structure.
Tập 44 Số 1 - Trang 186-196 - 2004
Chain extension behavior and thermo-mechanical properties of polyamide 6 chemically modified with 1,1′-carbonyl-bis-caprolactam
Tập 54 Số 1 - Trang 158-165 - 2014
Rheology and extrusion foaming of chain‐branched poly(lactic acid) Abstract In this study, the effect of macromolecular chain‐branching on poly(lactic acid) (PLA) rheology, crystallization, and extrusion foaming was investigated. Two PLA grades, an amorphous and a semi‐crystalline one, were branched using a multifunctional styrene‐acrylic‐epoxy copolymer. The branching of PLA and its foaming were achieved in one‐step extrusion process. Carbon dioxide (CO2 ), in concentration up to 9%, was used as expansion agent to obtain foams from the two PLA branched using chain‐extender contents up to 2%. The foams were investigated with respect to their shear and elongational behavior, crystallinity, morphology, and density. The addition of the chain‐extender led to an increase in complex viscosity, elasticity, elongational viscosity, and in the manifestation of the strain‐hardening phenomena. Low‐density foams were obtained at 5–9% CO2 for semi‐crystalline PLA and only at 9% CO2 in the case of the amorphous PLA. Differences in foaming behavior were attributed to crystallites formation during the foaming process. The rheological and structural changes associated with PLA chain‐extension lowered the achieved crystallinity but slightly improved the foamability at low CO2 content. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers
Tập 50 Số 3 - Trang 629-642 - 2010
Reactive modification of polyethylene terephthalate with polyepoxides Abstract In attempts to produce modified poldified polyethlene terephthalate (PET) ressins with improved rheology for applications requiring high viscosity and elasticity (e.g., lowdensity extrusion foaming, extrusion blow molding), a novel dimidodiepoxide of low molecular weight was evaluated aschain extender/branching ageent. Its reactivity was compared with that of an ethylene/glycidy1 methacrylate copolymer. The diepoxide showed higher reactivity than the copolymer and could be used at muchlower concentrations. The complex chain extension/degradation reactions occurring in the melt were followed in a batch mixer by torque changes, and by analyzing the prouducts for residual carboxy1 and hydroxy1 content, intrinsic viscosity, insoluble content and melt viscoelastic properties. The perliminary results of this work indicated an overall decrease in carboxy1 content, increase in hydroxy1 content, increase in intrinsic viscosity ans melt viscosity and storage modulus values depending on mixing time and the type and concentration of the additive. It is shown that under certain conditions. reaction of PET with less than 1 wt% diimidodiepoxide may produce materials with rheological characteristics similar to thouse of PET grades that are extrusion foamable by gas injection to low densities.
Tập 41 Số 4 - Trang 643-655 - 2001
Microstructure and crystallography in microcellular injection‐molded polyamide‐6 nanocomposite and neat resin Abstract The effects of adding nanoclay to polyamide‐6 (PA‐6) neat resin, and the effects of processing parameters on cell density and size in microcellular injection‐molded components were investigated. In addition, the crystal sizes, structures, and orientation were analyzed with the use of x‐ray diffraction (XRD) and a polarized optical microscope. The standard ASTM D 638‐02 tensile bars for the analyses were molded according to a fractional four‐factor, three‐level, L9 Taguchi design of experiment (DOE) with varying melt temperature, injection speed, supercritical fluid (SCF) concentration, and shot size. It was found that the presence of montmorillonite (MMT) nanoclay greatly reduced the size of the cells and crystals, but increased their density in comparison with neat resin processed under identical molding conditions. In addition, at the sprue section downstream of the machine nozzle, cell size gradually decreased from the part center toward the skin for both the neat resin and the nanocomposite. It was also found that shot size was the most important processing parameter for both the neat resin and nanocomposite in affecting cell density and size in microcellular injection molding components. Weakly preferred crystal orientations were observed on the surface of microcellular injection‐molded PA‐6/MMT tensile bars. Finally, the addition of nanoclay in PA‐6 neat resin facilitated the formation of γ‐phase crystals in the molded components. Polym. Eng. Sci. 45:52–61, 2005. © 2004 Society of Plastics Engineers.
Tập 45 Số 1 - Trang 52-61 - 2005
Study of injection molded microcellular polyamide‐6 nanocomposites Abstract This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The microcellular nanocomposite processing was performed on an injection‐molding machine equipped with a commercially available supercritical fluid (SCF) system. The molded samples produced based on the Design of Experiments (DOE) matrices were subjected to tensile testing, impact testing, Dynamic Mechanical Analysis (DMA), and Scanning Electron Microscope (SEM) analyses. Molding conditions and nano‐clays have been found to have profound effects on the cell structures and mechanical properties of polyamide‐6 (PA‐6) base resin and nanocomposite samples. The results show that microcellular nanocomposite samples exhibit smaller cell size and uniform cell distribution as well as higher tensile strength compared to the corresponding base PA‐6 microcellular samples. Among the molding parameters studied, shot size has the most significant effect on cell size, cell density, and tensile strength. Fractographic study reveals evidence of different modes of failure and different regions of fractured structure depending on the molding conditions. Polym. Eng. Sci. 44:673–686, 2004. © 2004 Society of Plastics Engineers.
Tập 44 Số 4 - Trang 673-686 - 2004
Crystallization and thermal behavior of microcellular injection-molded polyamide-6 nanocomposites
Tập 46 Số 7 - Trang 904-918 - 2006