ISSN:0360-2559    

DOI:10.1080/03602559308020150

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Wood-plastic composite (WPC) has been made by impregnating methylmethacrylate (MMA) monomer into simul, a native timber of Bangladesh, under Co-60 γ radiation. The effect of moisture and heat and humidity on simul and its WPC is investigated as a simulating phenomenon of the sunlight, rain, and moisture to which timber is generally exposed. Mechanical properties measured under variable conditions of moisture, heat, and humidity reveal that the WPC is a much improved product, suitable for use as a substitute for the good-quality timber normally applied for household goods.

ISSN:0360-2559    

DOI:10.1080/03602559308020151

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new polyurethane was prepared by polycondensation reaction of the α, 4-diisocyanate anisole with polypropylene glycol. Synthetic procedures for the preparation of the new diisocyanate are described. The monomers and the polymers formed therefrom are characterized by IR and NMR spectral data. Thermal stability of the polymer was studied by thermogravimetry.

ISSN:0360-2559    

DOI:10.1080/03602559308020152

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Dielectric relaxation measurements have been performed on 75 μm thick polyethylene terephthalate (PET) films. At 1 kHz frequency, samples treated by 55% and 100% relative humidity (RH) showed loss tangent increase of 28% and of 56%, respectively. Confirmed by the dielectric constant results, the increased strengths of the relaxation were linearly related to the percentage RH within experimental error. The activation energy of molecular polarization at 100% RH was determined by the Arrhenius relation to be 97.9 kJ/mol. This value is 36% greater than that of the dry and 55% RH samples, indicating that the water molecules are restricted between the polymeric chains. Possible mechanisms including van der Waals bonding of the water molecules to the terminal ends of the polymer chains or to carbonyl groups are suggested.

ISSN:0360-2559    

DOI:10.1080/03602559308020153

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In view of the high potential of polyacetal (polyoxymethylene, POM)/thermoplastic polyurethane (TPU) elastomer blends in engineering applications, greater emphasis is placed on long-term properties of these blends. Though the creep behavior of pure viscoelastic polymers has been extensively studied and the temperature effect within the linear viscoelastic range has been explained on the basis of time–temperature superposition principle, only a little information is available about these blends. This work was carried out in pursuit of workable theories for actual engineering applications with their applicability defined, and secondly, to seek comprehension of the physical mechanisms which control the manifestation of nonlinear viscoelastic behavior in these blends. Validity of an equation of the type ε = ε° + ε+tnhas been analyzed. The blends creep more than POM and the tendency to creep increases as the TPU content increases. It is found thatnis a constant for a given blend and is independent of stress over the stress range considered. For all the blends, ε° is approximately a linear function of stress, whereas ε+is a nonlinear function of stress irrespective of the composition of the blend. Monotonic tension tests have been carried out at three different strain rates and both POM and blends are found to be rate sensitive. Activation volume of POM and its blends with TPU has been evaluated and is found to increase as stress increases, in both cases.

ISSN:0360-2559    

DOI:10.1080/03602559308020154

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Epoxy resins are essentially prepolymers that contain on an average two or more epoxide groups per molecule. The object of the present review article is to give up-to-date information regarding the reactions of these resins with various curing agents leading to crosslinked or thermoset resins with excellent strength, toughness, and chemical resistance. The end-use consumption of epoxy resins covers a broad range of applications such as adhesives, bonding, construction materials (flooring, paving, and aggregates), composites, laminates, coating, molding, and textile finishing. Recently these resins have penetrated into the aero- and spacecraft industry. It is expected that anybody engaged in industry or academic research will find enough material in this review to start work, and need not search the literature before 1990.

ISSN:0360-2559    

DOI:10.1080/03602559308020155

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Photooxidative aging of high-impact polystyrene sheets at 25°C was followed for different intervals of 25, 40, 50, 75, and 80 h. Five different types of samples were used, viz. virgin, and recycled once, twice, three, and four times. The optical properties of exposed samples exhibited changes as a result of discoloration. The transmittance and reflection deceases whereas absorbance increases with increasing recycling of high-impact polystyrene.

ISSN:0360-2559    

DOI:10.1080/03602559308020156

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A comparative study was conducted on three commercial water-soluble polymers: partially hydrolyzed polyacrylamide (Separan AP30—Dow Chemicals), polyethylene oxide (Polyox Coagulant—Union Carbide), and xanthan gum (Keltrol—Kelco). Both the steady shear and the dynamic properties were examined. The presence of salt significantly reduces the viscous and elastic properties of Separan AP30. Negligible changes were observed for Polyox Coagulant. However, some marginal reduction in these properties was evident for xanthan gum at low salt concentration up tocsof 0.05 M, beyond which no effect was observed. The relationship between the rheological properties of the polymers and the salt concentration is governed by the charged characteristics of the polymer chains. The present study suggests that it is more desirable to use xanthan gum than polyacrylamide in a high-salt environment. Polyethylene oxide is usually avoided due to its cost and low resistance to mechanical degradation.

ISSN:0360-2559    

DOI:10.1080/03602559308020157

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Glass fiber reinforced epoxy composites were prepared using tetra-N-glycidyl-p,p′-diaminodiphenyl methane (TGDDM) as a resin matrix with/without fortifier PGEHA/VCDRC (at 20 phr level) using DDM/DDS as curing agent; the composites were evaluated for their various physical, mechanical, chemical, and electrical properties. Carbon fiber (i.e., unidirectional, bidirectional, and chopped) reinforced composites of TGDDM with/without epoxy fortifier PGEHA/VCDRC (at 20 phr level) were also prepared and evaluated for their physical and some mechanical and chemical properties. It is observed that incorporation of fortifier (at 20 phr level) improves these properties significantly.

ISSN:0360-2559    

DOI:10.1080/03602559308020158

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Number average molecular weight,Mnis dependent on the stoichiometry of a reaction in the case of polycondensation. Flory (D. J. Flory, Principles of Polymer Chemistry, Cornell University Press, Ithaca, NY, 1953, p. 92) has developed a relationship connecting the extent of reaction with the number average degree of polymerization for bifunctional reactants. An attempt is made here to extend this approach to reactants whose functionality is between 1 and 2, and also to arrive at a formula to calculate the number average molecular weight of such a system.

ISSN:0360-2559    

DOI:10.1080/03602559308020159

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor