摘要:

Flame retardance properties of 1,3 propylene glycol based unsaturated polyester containing 40% styrene and 20% acrylonitrile were investigated. The polyester with 12% Br content is self-extinguishing while others with lower bromine contents burn slowly. The high decrease in mechanical strength due to the presence of bromine is highly compensated by acrylonitrile.

ISSN:0360-2559    

DOI:10.1080/03602559408013091

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A convenient method for the synthesis of a new series of polyarylketones with relatively high molecular weights has been investigated. The polymers were prepared readily by direct polycondensation of terephthalic acid with a series of diaryl compounds using phosphorous pentoxide/trifluoromethanesulfonic acid (w/w = 1/10), phosphorous pentoxide/methanesulfonic acid (w/w = 1/10), and aluminum chloride/phosphorous oxychloride (w/v = 1/3) as condensing agents. Among the three, the phosphorous pentoxide/trifluoromethanesulfonic acid pair was found to be most efficient and was studied in detail. The thermal and crystalline properties of the resulting polyarylketones were characterized. All of the polyketones prepared in the present study are crystalline and their glass transition temperatures and melting points depend greatly on the structure of the diaryl compounds employed.

ISSN:0360-2559    

DOI:10.1080/03602559408013092

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Phenol lignin formaldehyde (PLF) was formed within bagasse pulp fibers, and the thermal degradation of the sheets was traced using the DTA technique. Other kinetic parameters were also calculated. An attempt was made to elucidate the mechanism of PLF formation in the pulp using data obtained from both kinetic and infrared measurements.

ISSN:0360-2559    

DOI:10.1080/03602559408013093

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Poly(vinyl chloride) (PVC) is a commodity plastic that is frequently used in geosynthetic applications. Its performance is important to the safety of landfills, where potentially dangerous chemicals must be segregated from the outside environment, such as groundwater, for considerable lengths of time. This review paper describes PVC and the modes of degradation that can affect its properties when it is used as a geosynthetic. These modes of degradation must be addressed by the PVC producers, the manufacturers of the geosynthetics, and the landfill operators.

ISSN:0360-2559    

DOI:10.1080/03602559408013094

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The paper reviews the kinetics and morphology of the various phase-segregation processes that may be encountered in multiphase polymer flow systems. A primary aim of this review has been to investigate how certain processing variables influence the polymer structure and the degree of phase segregation in various geometries of interest. A pronounced distinction is made between the terms “diffusion” and “field-induced segregation.” The former is conventionally regarded as the mass transfer resulting from Brownian motion and, in any case, is a randomizing process. The latter, on the other hand, implies “flow” of matter subject to a “driving potential.” As opposed to diffusion in the classical sense, field-driven transport may be affectedagainstthe concentration gradient. It is seen that the application of an appropriate lateral field generates transversal migration of suspended material or additive and, in certain cases, the segment domains in the “matrix” polymer. In particular, the potential of shear fields to generate locally segregated flow structures, which might be preserved during the fabrication procedure, has been assessed. It has been shown that with an expression for the lateral “drift” velocity, the time and space evolution of the cross-flow concentration profile may be obtained from the continuity relation. Even though one finds a surprisingly large variety of driving forces available for segregation transport, the efficacy of highly specific processes lies in the novel application of boundary conditions. Convection promoted shear transport has been cited as a relevant example with an initial condition which specifies a cross-flow velocity component in an existing shear field. Other promising configurations include the sequential flow in two-phase flow and rheological segregation. The investigation reveals that migratory transport in polymer processing channels has the potential to generate localized changes in the polymer morphology and structure, apart from affecting phase redistribution of additive species (both solid and liquid systems) on a more global scale. Experimental evidence obtained on the phase fractionation in polydispersed low-density polyethylene (LDPE) and thermosetting polyurethane (PU) clearly demonstrates the phenomenon.

ISSN:0360-2559    

DOI:10.1080/03602559408013095

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of suspended particles on the thermal instability of an Oldroydian viscoelastic fluid in hydromagnetics in porous medium is considered. The magnetic field, suspended particles, viscoelasticity, and porous medium effects create oscillatory modes in the system which did not exist previously. For stationary convection, the viscoelastic fluid behaves like a Newtonian fluid and the magnetic field has a stabilizing effect, whereas medium-permeability, suspended particles have destabilizing effects on the system. The sufficient conditions for the avoidance of overstability are obtained, and these also hold good for the case of a Maxwellian viscoelastic fluid.

ISSN:0360-2559    

DOI:10.1080/03602559408013096

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A polypropylene (PP)-grafted polyhydroxybutyrate (PHB) copolymer was synthesized by a three-step procedure. The existence of the PP-g-PHB copolymer was confirmed by IRFT analysis. Blends at different ratios of PP and PHB, in the presence and in absence of the grafted copolymer, were prepared. The mechanical properties of the blends were determined by tensile test and solid-state spectroscopy. Morphology studies were also conducted using scanning electron microscopy. The presence of only 5% of the copolymer in a PP-PHB blend affects dramatically the morphology as the domains of PHB seem to vanish into the PP matrix. The copolymer affects favorably the yield stress but affects negatively the properties at break. The calculated rheological properties using Dickie's model are compared with the experimental values.

ISSN:0360-2559    

DOI:10.1080/03602559408013097

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The equations of motion and continuity of a fully developed, steady-state, isothermal, incompressible laminar flow of power law fluids within a toroidal-type coiled tube geometry have been solved numerically using the successive overrelaxation method. Numerical solutions have been obtained for curvature ratios from 5 to 100, Dean number from 1 to 300, and power law index from 0.5 to 1.5. Dean's constraint has been relaxed and the numerical solutions for primary and secondary flow, and the numerical results of the friction factor for different values of Dean number, curvature ratio, and power law index have been computed. The solutions have been carefully checked for accuracy and the results are compared with previous studies. The numerical results are found to be consistent with the published results for the case of Newtonian fluids. The ratio of friction factor of a curved tube to a straight tube increases with the Dean number and also with the power law index.

ISSN:0360-2559    

DOI:10.1080/03602559408013098

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Poly(vinyl chloride) is one of the world's most important bulk thermoplastics. Approximately 15 million tons are produced annually. About 80% of this is made by the suspension process. Suspension polymerization of vinyl chloride is almost invariably accompanied by the formation of scale on the internal surfaces of the polymerization reactor, including moving surfaces such as those of the impeller. The formation of scale, or deposits of PVC, on the internal surfaces of reactors has always been a problem in the manufacture of PVC because of reduced heat transfer, large alteration of the agitation regime present in the reactor, and broken-off scale fragments that block transfer systems and contaminate the product. Therefore scale must be cleaned periodically. Until the early 1970s these deposits were removed manually; PVC workers were exposed to high levels of VCM and considerable production time was lost. The introduction of large reactors in 1975 made it practical to mechanize the cleaning. High-pressure water sprays are employed for this purpose. However, such devices remove only the slightly adherent sandy deposits. For strongly attached deposits, a thorough manual cleaning is necessary after a series of polymerization batches. Manual cleaning requires extensive safety measures to protect the workers from VCM vapor inside the reactor. In addition, such cleaning is costly and undesirable. In more recent years, methods have been developed to suppress or inhibit the formation of scale on the reactor walls. Proposed solutions in this field are sparese. The patient literature claims many chemical treatments to resuce reactor fouling. Many PVC producers have developed effective buildup-suppressant treatments, which significantly reduce the need for reactior cleaning. They vary from treatments to render the reactor wall hydrophilic and reduce the adsorption of VCM (e.g., application of a sulfonic acid polymer to the reactor surface [1]) to systems containing polymerization inhibitors and radical traps (e.g., organic dyes and phenolic resins). The most successful of these probably work by a combination of both mechanisms. In this paper the soultions are reviewed brifly and emphasis is given to suspension polymerization where the initiator is monomer soluble.

ISSN:0360-2559    

DOI:10.1080/03602559408013099

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The Fourth Meeting on Fire-Retardant Polymers was held from September 9 to September 11, 1992, at Albert-Ludwige-University, Freiburg im Breisgau, Germany. The meeting was organized by the Freiburg Materials Research Center (FMF) in close collaboration with the University of Torino, Department of Chemistry, IPM (Torino, Italy); University Louis Pasteur and Ecole d' Application des Hauts Polymer (EAHP—Strasbourg, France), and University of Kaiserslautern (Germany), and was supported by EPF (European Polymer Federation) of GPF (Group Fransais des Polymers). The Organizing Committee included R. Mulhaupt (Chairman, Germany), G. Camino (Italy), W. Becker (Germany), J. Brossas (France), and L. Costa (Italy). The Scientific Committee included W. Becker (BASF AG, Germany), G. Camino (University of Torino), P. Flury (Ciba-Geigy AG, Switzerland), I. C. McNeill (University of Glasgow, UK), R. Mulhaupt (University of Freiburg, Germany), J. Otton (Rhone-Poulenc, France), J.-C. Robinet (Norsolor, France), J. Troitzsch (Wiesbaden, Germany), J. Brossas (EAHP, Strasbourg), L. Costa (University of Turin), R. Locatelli (Himont, Ferrara, Italy), C. Moye (Centre Scientifique et Technique du Batiment, Name-la-Valle, France), S. Russo (University of Sassart, Italy), A. Sainrat (Lab. Nat. d'Essais, Paris, France), and D. Woolley (Fire Research Station, Borehamwood, UK).

ISSN:0360-2559    

DOI:10.1080/03602559408013100

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor