摘要:

AbstractA fatigue fracture diagram for BPA polycarbonate has been created from fatigue lifetime data obtained from knit line notched samples. This fatigue fracture diagram maps out stress‐temperature zones where fatigue fracture is dominated by crack growth through leading crazes and zones where fatigue fracture occurs through shear fracture at 45 degrees to the load direction. Both craze and shear planes coexist in the fatigue crack tip plastic zone, and both compete to determine the ultimate crack growth behavior. The shear planes preferentially develop (and fracture) at higher temperatures and stresses, but this fracture process is quite slow. Consequently, an inversion in the fatigue lifetime curve is observed, with longer lifetimes at higher stresses. This inversion is easily understood as a transition between a craze branch and a shear branch on the fatigue lifetime plot. When the fatigue lifetime curve is plotted for data at different temperatures, with the stresses normalized to the yield stress at the respective test temperatures, the craze branch data from different temperatures overlap. This overlap can be explained by theN= 2 power law dependence of crack growth in the discontinuous crack growth regim

ISSN:0032-3888    

DOI:10.1002/pen.760281002

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe influence of fillers like clay, silica, and carbon black on the rheological properties of 1,2 polybutadiene has been studied using a capillary rheometer. Silica filled compound exhibited the highest viscosity and clay filled compound the lowest viscosity at all shear rates. The effect of filler loading and temperature on the Theological behavior has also been studied. Smooth extrudates were obtained in most of the cases and die swell was lower for silica and carbon black filled compounds than for clay filled compounds. Rheograms of different 1,2 polybutadiene systems have been found to merge into a master curve using modified viscosity and shear rate functions that contain melt flow index as a parameter.

ISSN:0032-3888    

DOI:10.1002/pen.760281003

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractRelatively simple forms have been derived for obtaining the total force required to deflect a circular rubber disk of arbitrary dimensions between two rigid platens which offer Coulomb frictional resistance to flow of the rubber. The calculation of the critical radius which separates the regions of frictional adherence and restrained flow is a necessary step in the solution process. Although it cannot be solved for explicitly, an implicit form given herein converged rapidly. The solutions for force can involve differences between very large numbers as the coefficient of friction becomes small. Care should be used to evaluate these quantities in order to avoid round off errors.

ISSN:0032-3888    

DOI:10.1002/pen.760281004

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractPolyureas have the potential for Improving reaction Injection molding (RIM) productivity through shorter demo Id times and elimination of external mold release agents and post‐cure. Kinetics of urea formation are necessary for process modeling of polyurea RIM systems. Adiabatic temperature rise measurements were used to monitor the extent of reaction of an aliphatic diamine and an aromatic diamine reacting competitively with a single diisocyanate. The aliphatic diamine reacted much faster; essentially complete polymerization occurred in the RIM mixhead. A similar three‐component system was studied in dimethylacetamide and diethylene glycol dimethyl ether, and the sequential nature of the two competing reactions was confirmed. The RIM polymerization of the aromatic diamine, 3,5 diethyltoluene (2,4 and 2,6) diamine and;4,4′‐diphenylmethane diisocyanate was studied using an unreactive poly ether as the solvent. The exotherms could be fit with a third order model. Adiabatic temperature rises for all RIM experiments were in good agreement with the values predicted by heats of reaction measured in s

ISSN:0032-3888    

DOI:10.1002/pen.760281005

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe dynamic shear viscosity and the morphology of polypropylene homopolymer and copolymer blended with linear low density polyethylene are studied. A maximum in the dynamic shear viscosityvs.blend composition is reported for the polypropylene copolymer, linear low density polyethylene system. The increasing dynamic shear viscosity is in accordance with the occurrence of a morphology of polyethylene inclusions in rubber surrounded by a polypropylene matrix. Comparing calculations of the dynamic shear viscosities—based on a shell model with interlayer—and experimental results supports this v

ISSN:0032-3888    

DOI:10.1002/pen.760281006

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA block Copolyurethane was synthesized by using a hydroxy‐terminated 1,2‐polybutadiene (HPBD) having vinyl side chains and a molecular weight of 2000 to 5500 as a rubber‐affinitive component, a hydroxy‐terminated poly(ethylene terephthalate) as a PET‐affinitive component, and 4,4′‐diphenylmethane diisocyanate as a chain extender. The block copolymer was mixed with a curing agent and used for the adhesion of PET cord of 1100 denier and rubber. The peak of adhesive strength was observed at the HPBD molecular weight of 4500 within the molecular weight range of

ISSN:0032-3888    

DOI:10.1002/pen.760281007

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractHydroxy‐terminated copoly(fstyrene‐b‐1,2‐butadiene) (HPSB) containing rubber‐affinitive vinyl side chains and having a molecular weight of 2000 to 4000 were prepared, and block copolyurethanes were synthesized by using a low molecular weight hydroxy‐terminated poly (ethyl en e terephthalate) as a PET‐affinitive component and 4,4′‐diphenylmethane diisocyanate as a chain extender. The relationships between the molecular weight of HPSB, copolymerization ratio of styrene to butadiene and the adhesive strength of PKT/rubber in high temperature atmospheres were examined. A peak of adhesive strength was observed at styrene copolymerization ratio of 20 wt percent and a HPSB molecular weight of 3000. The adhesion mechanism was estimated from the behavior of the characteristic infrared absorption of block Copolyur

ISSN:0032-3888    

DOI:10.1002/pen.760281008

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe development of the mechanical properties and stresses during the formation of polyamic acid (PAA) coatings has been studied using methods such as a “propagating wave technique.” The shrinkage stress due to solvent removal in PAA coatings under a one dimensional constraint was determined to be 8 MPa. A coupling between the residual stress and solvent removal process has been obser

ISSN:0032-3888    

DOI:10.1002/pen.760281009

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760281001

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY