摘要:

AbstractThe electrical properties of a number of filled and coated plastics were examined after subjecting the materials to rigorous thermal cycling between −20 and 80°C. Filled compounds that obtained their conductivity through the addition of carbon based conductive fillers maintained their conductivity throughout the thermal cycling. Compositions which contained metal fillers were able to maintain their conductivity only when a high temperature thermally stable polymer was used as the polymer matrix. Plaques coated by a zinc arc spray or with acrylic paints containing graphite, silver, and nickel particles were unaffected by thermal cycling. Plaques coated with an acrylic paint containing copper particles lost most of their conductivity during the changes in sample temperatu

ISSN:0272-8397    

DOI:10.1002/pc.750070202

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractShort glass fiber orientation in a center gated molded disc of polyamide is studied using optical microscopy techniques. The very different orientation between the core and the surface of the molding is quantified with an orientation function. The influence of the molding conditions is investigated. A numerical scheme is used for modeling the mold filling with a viscous melted polymer. A computation method is introduced to describe the fiber movement during the flow. The theoretical results are in good agreement with the experimental ones. In particular, the very different orientation between the skin and the core of the disc is well predicted.

ISSN:0272-8397    

DOI:10.1002/pc.750070203

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractGraphite epoxy composites which are exposed to high humidity environments suffer a loss in their shear and transverse properties. In addition to the effect of moisture on the matrix, thermodynamic theories suggest that the interface may suffer irreversible damage. In this study, we investigated if fiber surface treatments could improve fiber matrix adhesion as well as the wet composite properties. Plasma polymerization was used to generate very thin coatings with the polar component of the surface energy varying from 1.8 to 5.3 (dyne/cm)1/2. These coatings were characterized by ESCA and SEM, and a micro‐Wilhelmy technique was used to determine the dispersive and polar components of the surface energy. The uniaxial composites made with the treated fibers were tested wet and dry in short beam shear. It was found, as is well known, that the dry shear properties could be improved by up to 40 percent. Two effective treatments were oxygen etching and polymerization with methylmethacrylate monomer. However, all the wet samples failed at the same stress regardless of the surface treatment used. These results strongly suggest that the shear and transverse properties of the wet composites are dominated by the epoxy and cannot be improved by interface treatment

ISSN:0272-8397    

DOI:10.1002/pc.750070204

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractMultilayer printed circuits are a prime example of complex polymer composites. One of the critical steps in manufacturing of the circuit boards is the lamination process, which is frequently simulated by the aborted flows test (AFT). In order to obtain a composite free of voids and good interlaminar adhesion, it is imperative for the resin to flow into metal interfaces as well as intermix in the resin interfaces. On an empirical basis, the AFT is used as a process monitor for making prepreg, the glass fiber reinforced dielectric which supports the circuitry. Under a given set of conditions (temperature profile, pressure, layup), AFT measures advancement and reactivity of prepreg. By using a given batch of prepreg, the optimum laminating conditions can be identified, which are mainly a function of the temperature profile. Here, a calorimetric and rheological study of prepreg cure kinetics during lamination is presented. The flow process is being modeled by calculating the viscosity from combining a temperature dependent viscosity term with a kinetically controlled molecular weight term.

ISSN:0272-8397    

DOI:10.1002/pc.750070205

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractQuantitative estimation of matrix‐filler interaction in highly loaded ferrite filled Styrene‐isoprene‐styrene block copolymer has been attempted through dynamic viscoelastic melt studies. A correlation between the interaction parameter in the melt state and that in the solid state at comparable frequency of deformation has been shown to exist so that the matrix‐filler affinity at any temperature of interest can be estimated. Such a correlation eliminates the need for generating solid state dynamic data in order to check matrix‐filler compatibility as the results obtained in the melt could be extrapolated to the behavior in the so

ISSN:0272-8397    

DOI:10.1002/pc.750070206

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractStudies were performed to synthesize new ether modified, flexibilized aromatic diamine hardeners for curing epoxy resins. The effect of moisture absorption on the glass transition temperatures of a tetraglycidyl epoxy, MY 720, cured with flexibilized hardeners and a conventional aromatic diamine was studied. Unidirectional composites, using epoxy‐sized Celion 6000 graphite fiber as the reinforcement, were fabricated. The room temperature and 300°F mechanical properties of the composites, before and after moisture exposure, were determined. The Mode I interlaminar fracture toughness of the composites was characterized, using a double cantilever beam technique to calculate the critical strain energy release rate,G

ISSN:0272-8397    

DOI:10.1002/pc.750070207

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractPolypropylene (PP) compositions containing CaCO3filler, EPDM (ethylene‐propylene‐ethylidenenorbornene) elastomer, and a non‐reactive surfactant were investigated in the mixing chamber of a plastograph. Rheological properties were determined from the registered torque (M)vs.time and temperature (T)vs.time curves, while tensile characteristics of the blends were measured on compression molded plates. The homogenization process can be followed with the aid of 1n M vs.1/Tdiagrams. In the first few minutes of the mixing, beside homogenization, a significant breaking down of the elastomer takes place, and the size of the particles attains an equilibrium value. Dispersion time increases with increasing amount of EPDM and surface active‐agent. Morphological investigations indicate the presence of a continuous PP phase containing dispersed CaCO3and elastomer particles. The rheological and tensile characteristics are seemingly determined by the total amount of additives, which imply that the elastomer and the filler has the same effect on the properties of the composite. Separation of the effects proved, however, that the effect of the two components are dissimilar, the filler exerts a larger influence on the investigated pro

ISSN:0272-8397    

DOI:10.1002/pc.750070208

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Weibull distribution is presented as a physically consistent description of strength distribution in brittle composites. Methods are developed for obtaining point and one‐sided interval estimates for the parameters of the Weibull distribution. Strength data are obtained for 25 replicates of nine different sheet molded and injection molded composites, and the developed statistical methods are applied to these data. Details of the materials and processing are given. Strength results indicate that the reliability calculations using the one‐sided interval estimates are uniformly conservative for all materials. In addition, it is shown that composites produced with a less automated production process show more strength variability. Machining of an injection molded composite surface appears to lower strength and increase strength variability by introducing flaws which act as fracture initiation si

ISSN:0272-8397    

DOI:10.1002/pc.750070209

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750070201

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY