摘要:

AbstractThe chemical modification of high density polyethylene (HDPE) in a counter‐rotating nonintermeshing twin screw extruder is modeled using a simultaneous random scission and cross‐linking integro‐differential equation. The roles of mixing and kinetics in the free‐radical reaction are investigated. The modification experiments use a masterbatch feed of HDPE with various concentrations of 2,5‐dimethyl‐2,5‐(t‐butylperoxy)‐3‐hexyne. The extruder operating parameters studied were barrel temperature, screw speed, and the degree of screw flight stagger. The reaction model is fit using the molecular weight averages and the gel content measured experimentally. The reaction time for HDPE is determined by use of the residence time distribution of the extruder with a segregation (macromixing) assumption. The segregation model is compared against the plug flow assumption, where the mean residence time of the measured distribution is used for the length of reaction of all polymer species within the extruder. The calculated molecular weight distributions are insensitive to the mixing model used. © 1995

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA chemical modification method has been developed to convert lignin into lignin–styrene graft copolymers. The graft products are macromolecular surface active agents because, within each molecule, a hydrocarbon sidechain has been grown off of a natural oxyphenylpropyl backbone. Surface activity of the graft copolymers was indicated by their capacity to form stable emulsions between incompatible fluid phases and to adhesively bond to wood surfaces. Dynamic contact angle measurement using the Wilhelmy plate technique showed that the graft copolymers changed the contact angle of water on wood from 50° to 110°. Coating birch wood (Betula papyrifera) with lignin–styrene graft copolymerization product increases the water contact angle and the binding strength of polystyrene on the wood. Lap shear strengths increased 56%, from 1826 to 2840 kPa, when the wood was coated with a graft copolymer containing 51.7% lignin. Binding was tested by coating the birch with a solution of graft copolymer, drying the wood, injection molding polystyrene onto the surface of the wood, and pulling the polystyrene off the wood surface in a lap shear brace. These properties of the copolymers were used to design a process for forming wood‐thermoplastic composites. © 1995 John Wiley&S

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFive, ten, and twenty percent by weight blends of polysulfone in polycarbonate and polyetherimide in polycarbonate were produced by melt blending. The materials were injection molded into plaques. Mechanical analysis consisting of tensile, pendulum impact, and ballistic impact testing was conducted using the plaques or samples machined from the plaques. The average impact strength and percentage of ductile failures decreased with increasing composition of polysulfone and polyetherimide. The tensile test results indicate that a relationship exists between the percent composition and the yield strength for the blends with the blends showing an improvement in tensile strength. The ballistic testing results show that a possibly linear relationship exists between the percent composition and the critical velocity for complete penetration. Differential scanning calorimetry was conducted to measure the glass transition temperatures of the materials. The presence of two glass transition temperatures and lack of transparency have indicated that the blends are immiscible. © 1995 John Wiley&Sons, Inc

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, the morphologies and the mechanical properties of the ternary blend of PA (polyamide)6/SEBS(styrene–[ethylene–butylene]–styrene triblock copolymer)/maleated SEBS were investigated. Maleated SEBS compatibilizers of various maleic anhydride (MA) content were prepared in the laboratory. The compatibilizer significantly influenced the dispersion of the rubber as well as the crystalline form and spherulites of the polyamide. The effects of the compatibilizer on mechanical properties were correlated with the observations of morphology and stress–strain behavior. The toughness of the blends was found to be increased for those undergoing additional yielding during cold drawing. Finally, a compatibilization mechanism of maleated SEBS for the blends was proposed. © 1995 John Wiley&S

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe objective of this article is to review the use of conductive plastics in the shielding of electromagnetic interference (EMI). The theory of EMI shielding and evaluation methods of EMI materials are discussed. Different approaches in achieving high conductivity of plastics are reviewed. Emphasis is placed on filled plastics which are a promising way for shielding and do not require a secondary process. Literature on properties and processing of several common conducting plastics is reviewed. Design and processing requirements of such filled plastics are also given. © 1995 John Wiley&Sons, Inc

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractOn‐line/in‐line measurement technologies are increasingly finding uses for controlling the quality of polymeric materials during all phases of production and for minimizing waste in the form of off‐spec materials. In addition to commercial/developmental sensors for rheological or spectroscopic monitoring of extrusion processes, prototype instruments have been recently developed for in‐line optical monitoring of multiphase polymer melts. In this article, examples of developments in in‐line/on‐line Fourier Transform Infrared (FTIR) and Near Infrared (NIR) spectroscopy and optical microscopy and their applications to extrusion processes will be presented. © 1995 John Wil

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY