摘要:

AbstractChain extended perfluoroether oligomers were found to be miscible with bisphenol epoxy resins at all concentrations. These were evaluated as modifiers for anhydride cured resin systems, taking advantage of the carboxylic acid functionality at the chain ends. By altering the mixing and curing procedure different two‐phases morphologies could be obtained varying from fine co‐continuous networks, which produced transparent castings, to opaque systems consisting of precipitated heterogeneous particles. While theTgand flexural modulus were found to be slightly lower than the control cure resin, the addition of the fluoroligomer modifier produced large increases in flexural strength, ductility, and fracture toughness. Samples with an IPN type morphology were found to exhibit an increase in ductility after aging at 200°C for three weeks proportionally to the concentration of fluoroligomer

ISSN:0032-3888    

DOI:10.1002/pen.760351302

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractDouble yield points before necking were observed in injection molded specimens of poly(tetramethylene terephthalate) (PTMT) and its copolymers under tensile loading. The first yield is associated with deformation of the amorphous region and the second yield is caused by the alpha to beta transition of PTMT crystallites. The first yield point became less apparent with an increase of crystallinity of the specimens. The second yield point became more apparent with an increase of crystallinity. Annealing of injection molded specimens increased the crystallinity and increased the second yield point on stress‐strain curves. Copolymerization decreased the crystallinity and made the first yield point more prominent. Effects of annealing on mechanical and thermal properties of the specimens were also measured. The specimens changed their properties from ductile to brittle during annealing. Their change during annealing was mainly attributed to the increase of crystallinity and not to thermal degradation and/or crosslinkin

ISSN:0032-3888    

DOI:10.1002/pen.760351303

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractA comprehensive study of toughening unsaturated polyster and vinyl ester resins by addition of liquid rubbers was carried out by considering the effects of cure temperature and gel time on final resin/rubber morphology. The objective was to produce a dispersed rubber phase consisting of particles less than 15 μm in diameter with the addition of limited amounts of rubber, so as not to seriously reduce the modulus and strength of the base resin. A variety of liquid rubbers was used including those based on poly(butadiene acrylonitrile), poly(epichlorohydrin), and two poly(acrylates). Fracture toughness of unmodified and rubber modified materials was measured using the compact tension (CT) test geometry. Significant improvements in fracture toughness were achieved with little to no change in Young's modulus or glass transition temperature. With modest rubber additions, the fracture toughness increased up to 62% for the polyester resin and up to 116% for the vinyl ester resin. In general, fracture toughness increases with increases in volume fraction of rubbery second‐phase particles. However, results suggest that two‐phase particles may be more effective tougheners than single‐phase particles. The toughening mechanism appears to depend on the type of rubbery particle morphology p

ISSN:0032-3888    

DOI:10.1002/pen.760351304

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractEvaporation behavior of water/solvent blends was estimated using the universal functional activity coefficient, UNIFAC, method. The evaporation rate from a free surface of a waterborne coating, WBC, containing a co‐solvent was experimentally determined. These results were used to estimate the evaporation rate from wet films of a WBC containing a variety of co‐solvents with a range of initial thickness. Knowing the composition of the WBC during the drying process, the change in the viscosity and the surface tension was determined. The results strongly support the development of a surface tension gradient in the film. It is also suggested that a surface tension gradient would accelerate the leveling of the ribs if a proper co‐solvent were emp

ISSN:0032-3888    

DOI:10.1002/pen.760351305

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe present paper explores an effective means of characterizing structural changes of poly(vinyl chloride) (PVC) particles during gelation and fusion of PVC plastisols with small angle light scattering (SALS). The SALS method was shown to provide anin situobservation of swelling of PVC particles as well as quantitative information of average size of swollen particles while they are in progress of gelation and fusion. In addition, the SALS method enabled one to evaluate the relative solvent power of plasticizers from the manner of increase in the correlation distances.

ISSN:0032-3888    

DOI:10.1002/pen.760351306

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe miscibility window of the 50/50 w/w poly(styrene‐co‐4‐vinylphenyl)‐dimethylsilanol/poly(n‐butyl methacrylate) (ST‐VPDMS/PBMA) blends prepared from toluene was studied and determined to be in the VPDMS composition range of 4 to 18 mole% in the copolymers. The observed miscibility window was to be compared to the range of 9 to 34 mole% found for the blends prepared from methyl ethyl ketone which was capable of competing for hydrogen bonding. The fact that the observed miscibility windows are influenced by the choice of solvents illustrates that an equilibrium state of polymer mixing is not always attained in solvent casting films and that caution needs to be exercised in studying polymer miscibility when solvent cast fil

ISSN:0032-3888    

DOI:10.1002/pen.760351307

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractDouble yields, as well as other complex yielding behavior, that are observed during the tensile deformation of the polyethylenes have been studied in a systematic manner. The conditions under which such yielding is observed were established by studying a set of linear polyethylenes and well‐characterized ethylene copolymers of narrow molecular weight and composition distributions. A wide range in crystallinity levels were developed and the rate of deformation and the deformation temperature were varied. These experimental results make clear why such complex yielding processes are not always observed. A qualitative explanation, based on the postulate of a partial melting‐recrystallization process during deformation, is given that encompasses all of the experimental d

ISSN:0032-3888    

DOI:10.1002/pen.760351308

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe fracture behavior of polypropylene reinforced with 30% by weight of short glass fibers was studied using single and double feed plaque moldings. Plaques were injection molded using several gate types and gate positions. Fracture toughnessKc, was calculated at different positions in the plaque moldings using single edge notched tension specimens. Fracture toughness was assessed in the directions parallel and perpendicular to the mold fill direction through measurements of the load to produce complete fracture. Results indicated that the value of fracture toughness is affected by the type of gate as well by size of gate. Position of the specimen also affected fracture toughness. Generally, specimens taken from positions near cavity walls gave higher toughness values than those taken from the center of the moldings. Furthermore, fracture toughness in the transverse direction was consistently higher than in the melt flow direction. Finally, in the case o double feed moldings, a much higher fracture toughness was obtained when the initial crack was perpendicular to the weld line than when it was placed inside the weld line.

ISSN:0032-3888    

DOI:10.1002/pen.760351309

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760351301

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY