摘要:

Polyurethanes were obtained by the reaction of the hydroxyl group of castor oil with isophorone diisocyanate under different stoichiometric ratios of NCO/OH. A series of polyurethane-poly(methyl methacrylate) simultaneous interpenetrating polymer networks (PU/PMMA IPNs) of different compositions were synthesized as tough films by casting from glass molds. These IPNs were investigated using their resistance to chemical reagents, thermal behavior, tensile strength, Young's modulus, elongation at break (%), and Shore A hardness. The dielectric properties (σ, ε′, ε″ and tan δ) at different temperatures were studied. Electron microscopy confirmed the phase separation.

ISSN:0360-2559    

DOI:10.1080/03602558908048582

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The importance of branching degree and its distribution in a polymer has been broadly recognized in polymer processing. Characterization with GPC-LALLS is becoming popular in the industry currently due to its instrumental and theoretical development. A recently published computer simulation supports strongly the hypothesis that the momentarily eluted polymer is essentially monodisperse on molecular weight distribution even in case of a real GPC. The relationship between intrinsic viscosity [η] and branching degree is not comprehensively understood although it is most fundamental in any approach to the branching structure with GPC. Therefore, the semiempirical exponential relationship between [η] and another property well correlated to the branching degree is investigated. The mean square radius of gyration is representative of such properties. Anyway, the exponent should be determined by the experiments using model polymers with known branching degrees. The relationships between [η] and the Stokes radius or the second virial coefficient are also studied but their completeness is less satisfactory. The modern renormalization group method makes a great success of the quantitative treatment of chain conformation of branched polymers of various kinds in good solvents, although the solution for the randomly branched polymers in most industrial applications is not yet given.

ISSN:0360-2559    

DOI:10.1080/03602558908048583

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The use of stiffening ribs for automotive exterior parts such as deck lids and hoods has been studied extensively in the past for panels made from sheet molding compound (SMC). These studies show that the presence of the ribs causes some kind of deformation (rib readout) on the cosmetic side which deprives the parts from having a class A surface. These surface deformations are sometimes in the form of protuberances (“hills”) and sometimes in the form of depressions (“valleys”). A review of the literature confirms that there are a multitude of parameters that can cause the formation of rib readout on the surface of SMC panels. In this paper, and for the first time, the role of each of these parameters in terms of contribution to the formation of hills or valleys on the cosmetic surface is identified and discussed. For instance, the polymerization shrinkage of the resin and the thermal contraction of resin-rich regions are recognized to be the factors that cause valleys on the surface. The compressibility of resin-rich regions and the thermal contraction of glass-rich regions and regions with misaligned fibers, on the other hand, are the parameters that cause the formation of hills on the surface. The role of in-mold coating is also examined and an explanation is given of its contribution to the formation of hills on the surface. The effect of the painting process is also discussed, and it is concluded that cure of the paint at elevated temperatures brings out traces of rib readout even when the surface of the part is sanded smooth prior to paint application. In light of this analysis, a proposed set of characteristics is given for an ideal resin with a low profile agent, the polymerization of which will not contribute to the formation of rib readout.

ISSN:0360-2559    

DOI:10.1080/03602558908048584

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

There is growing interest in the development and applications of composites in building industries. Composite action, for example, is based on the concept of combining dissimilar materials to form a composite fulfilling specific design requirements.

ISSN:0360-2559    

DOI:10.1080/03602558908048585

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Prerequisite to any meaningful discussion regarding the scratch resistance of plastics and glass, we must define “scratching” and understand something about the chemistry of the surfaces involved, namely glass and plastics.

ISSN:0360-2559    

DOI:10.1080/03602558908048586

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0360-2559    

DOI:10.1080/03602558908048587

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0360-2559    

DOI:10.1080/03602558908048581

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor