ISSN:0032-3888    

DOI:10.1002/pen.760350102

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractPolymer blends are defined as mixtures of at least two polymeric species. Thus, the first patent polymer blend was a mixture of natural rubber, NR, with gutta percha patented by Alexander Parkes, an artist of Birmingham, in 1846. The first man‐made polymer, nitrocellulose, NC was prepared by Braconnot in 1833. The resin was commercialized in 1868, but its first blends (with NR) were patented three years earlier. The first patent on blends of two synthetic polymers was granted in 1928 for poly(vinylchloride)/poly(vinylacetate), PVC/PVAc (latex blending). During the intervening 65 years, the polymer blend patent literature grew at an exponential rate; since 1983 the annual output has doubled, to exceed 3000 patents/year in 199

ISSN:0032-3888    

DOI:10.1002/pen.760350103

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractSolid‐catalyzed copolymerization reactions of ethylene and α‐olefins can produce complex mixtures generally regarded as “polyethylenes” (including linear low‐density polyethylene). The selective nature of those catalysts can lead to block‐like character in segments of polymer molecules, and these segments are sufficiently dissimilar (from a thermodynamic viewpoint) to allow for the possibility of microphase separation in the melt. Such a molecular‐level phase separation would substantially alter the melt rheology, the crystallization process, and hence the mechanical and optical properties of the resulting product. It would, in principle, be identical to those occurring in conventional well‐defined block copolymers, allowing the thermodynamic models developed for those systems to be extended to block

ISSN:0032-3888    

DOI:10.1002/pen.760350104

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractPositron annihilation lifetime spectroscopy (PALS), capable of probing free volume, is used to study the effect of compatibilizer concentration, compatibilizer type, and the effect of blend processing on the morphology and properties of an immiscible linear low‐density polyethylene/polypropylene system. It is proposed that improvement of fracture toughness due to compatibilization can be attributed to the packing (and bonding) at interfaces. Improved interfacial packing and bonding result in lower free volume concentration than expected from component additivity, with a concomitant increase in plastic deformation on impac

ISSN:0032-3888    

DOI:10.1002/pen.760350105

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractAn automated, solid‐state small‐angle light scattering apparatus has been constructed for the investigation of polymers; the main features of this system are a bidimensional CCD (charge coupled device) detector with 12‐bit resolution and custom‐made, user‐friendly software for the acquisition and treatment of the scattering data. The miscibility and phase separation kinetics of several bisphenol‐A polycarbonate/poly(methyl methacrylate) blends have been investigated using this apparatus. It was found that the rate of phase separation can be altered significantly by replacing part of the polydisperse poly(methyl methacrylate) (PMMA) in the blends by monodi

ISSN:0032-3888    

DOI:10.1002/pen.760350106

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractStudies of the microstructure and permeability of extruded ribbons of polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) and polyethylene (PE)/polyamide‐6 (PA‐6) blends have shown that it is possible to control the flow‐induced morphology to generate discontinuous overlapping platelets of EVOH or PA‐6 dispersed phase in a PP or HDPE matrix phase. The effects of the following factors on morphology development and blend properties were considered: blending sequence, melt temperature, composition, compatibilizer level, die design, screw type, and cooling conditions. The impact properties and interfacial adhesion of laminar blends of PP and EVOH were improved without diminishing the barrier properties. The oxygen and toluene permeability of extruded samples with EVOH content of 25 vol% resembled values obtained with multilayer systems. Processing conditions had a major influence on the morphology of blends of high density polyethylene and polyamide‐6 (HDPE/PA‐6), and, under special processing conditions, laminar morphology was obtained in this system. The toluene permeability of extruded ribbons of HDPE/PA‐6 blends was in the range obtained with multi

ISSN:0032-3888    

DOI:10.1002/pen.760350107

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractRelationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber‐reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formatio

ISSN:0032-3888    

DOI:10.1002/pen.760350108

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, blends of virgin and recycled polyethylene (PE) and poly(vinyl chloride) (PVC), with a methylmethacrylate‐ethylacrylate copolymer as a processing aid, were prepared in the molten state. Different additives such as ethylenevinylacetate copolymers, ethylene‐methacrylic acid ionomer, and two peroxides (dibenzoyl and dicumyl), in the presence of a coupling agent, were used to compatibilize the blend or possibly induce graft structures. The blends' morphologies, tensile properties, and impact properties were studied. For blends with low copolymer concentration (below 3 wt%) the mechanical test data indicated a good performance. In the case of blends with ethylene methacrylic acid ionomer, improvements in the mechanical properties were obtained also at higher additive concentrations. Of the two peroxides, better results were obtained using the dibenzoyl one. The morphological studies indicated that the blends that showed good mechanical properties were better dispersed and had improved interphase adhes

ISSN:0032-3888    

DOI:10.1002/pen.760350109

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe recent growth in the post‐consumer recycling of plastics presents an opportunity for developing new, value‐added blend products from the recycled polymers. However, in order to develop blends with useful performance characteristics, suitable techniques of compatibilization and impact modification must be employed. In this study, reactive toughening and compatibilization techniques have been found to be particularly useful in achieving high thermal embrittlement resistance in the blends of recycled poly(ethylene terephthalate) containing functionalized ethylene copolymers and polycarbonate. Reactive compatibilization of recycled polyolefin blends with poly(ethylene terephthalate) and polyamide has also been investiga

ISSN:0032-3888    

DOI:10.1002/pen.760350110

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring the last few years, improvements in control strategies became a necessity, with controls being targeted on material properties. The ever‐increasing demand for polymer blends spells the need for in‐line instrumentation capable of monitoring blend properties such as morphology. Since ultrasonics have proved to be sensitive to properties of multiphase materials, their performance for discriminating blend morphology was explored here. In‐line and off‐line (static, with no flow) ultrasonic measurements were made on different blends of polystyrene (PS), polyethylene (PE), and polypropylene (PP) for various viscosity ratios, and over the entire range of composition. Blends were compounded on a ZSK‐30 Werner&Pfleiderer intermeshing co‐rotating twin‐screw extruder. In‐line ultrasonic measurements were performed on both single‐screw and twin‐screw extruders. Ultrasonic properties (velocity and attenuation) were found to vary approximately linearly with composition. Mixing rules were evaluated for the description of ultrasonic behavior. For the attenuation measurements, the positive deviations from these rules were found significant. The additional attenuation was attributed to scattering generated by the presence of the min

ISSN:0032-3888    

DOI:10.1002/pen.760350111

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY