摘要:

AbstractThe toughness of polymer composites based on low‐density polyethylene (LDPE)/polypropylene (PP) blends and filled with talcs of different particle size and particle size distribution was studied applying the two‐variable Box‐Hunter method of optimization. The effect of the polymer matrix composition and percent talc on the Charpy impact strength of the composites, at –30°C, was investigated. The results show a change in the polymer matrix behavior at PP contents of 60% and 75%, depending on talc particle size. At these percentages of PP, toughness exhibits a minimum that becomes lower as the filler content is increased. Optical microscopy shows a nucleating effect of the talc particles for the crystalline polymer. The larger the talc particle size, the higher the nucleation density. The minimum toughness arises at higher PP content in the matrix. At PP contents in the matrix below 35%, the filler has a minimal effect on composite t

ISSN:0272-8397    

DOI:10.1002/pc.750090202

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe tensile behavior of polyethylene/ethylene vinyl acetate (PE/EVA) polymer blends filled with calcium carbonate (CaCO3) was studied using tensile and viscoelastic tests. The relations between tensile properties (modulus, strength, etc) of oriented and unoriented PE/EVA‐CaCO3, and void volume of polymer/CaCO3interface, PE/EVA blend ratio, and CaCO3content were investigated. The results indicated that the tensile strength and elongation of PE/EVA‐CaCO3decreased with CaCO3content and PE blend ratio for unoriented PE/EVA‐CaCO3systems. In the case of oriented samples, the relative modulus (E dc/E dp, whereE dcandE dpare the modulus of oriented composites and the modulus of oriented matrix, respectively) of PE/EVA‐CaCO3is larger than that of PE/CaCO3by increasing the EVA content relative to PE and CaCO3. The value ofE dc/E dpcan be simply expressed as the function of void volume and CaCO3modulus to pol

ISSN:0272-8397    

DOI:10.1002/pc.750090203

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe theory of coalescence in melts of polymer blends was derived on the basis of the Smoluchowski theory for colloid systems. An approximation for a flux of particles used for solutions of colloids in water was analyzed. It is shown that this approximation cannot be used for polymer blends, and an approximation is suggested that could be justifiably used for them. A system of equations was derived for the time dependence of the number of individuali‐mers, using the relation suggested for the diffusion flux of particles. In an approximation of the uniform increase in particle size, equations were found for the time dependence of the number of particles, the average radius of the particle, and the interface area in the volume unit of the blend. The suggested theory predicts measurable coalescence in considerably more viscous systems than mechanically applied relations of the Smoluchowski theory for aqueous colloid solution

ISSN:0272-8397    

DOI:10.1002/pc.750090204

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA nondestructive method is proposed to analyze the internal stresses of a circular bilayered laminate glassresin. It is based on the measurement by optical interferometry of small deformations of the laminate under the influence of temperature, time, or applied mechanical stresses of known value. For example, the stress induced by the curing of the thermosetting resin layer is determined and the postcuring relaxation of the stress is measured. Other possibilities or improvements of the method are indicated: The determination of the Young's modulus of the thermosetting resin as a function of time, the determination of the work‐hardening rate, and the determination of the ultimate properties of the laminate are just a few of the

ISSN:0272-8397    

DOI:10.1002/pc.750090205

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractAlthough impact and flexural strength of injectionmolded bulk molding compounds increase initially with glass fiber content, these properties level out at a glass volume fraction between 0.1 and 0.2, limiting the achievable properties. Use of “special purpose” polyester resins gives no significant improvement in impact. The impact strength limitation is not worsened, however, by using the maximum processable level of filler, this being true for all fillers commonly used in polyester compounds. Replacement of a fraction of the glass by poly(ethylene terephthalate) fibers results in a substantial improvement in impact stren

ISSN:0272-8397    

DOI:10.1002/pc.750090206

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of filler content and applied electrical field on the electrical resistivity of poly(methyl methacrylate) (PMMA) filled with aluminum particles was investigated. The resistivity of such composite suddenly decreases by several orders of magnitude at a critical volume concentration ϕc. In addition, for filler contents lower than ϕc, the PMMA/Al composite undergoes a transition from a high to a low resistance material in correspondence of a critical value of the external applied electrical field. This value has been related to thermal breakdown occurring in the regions between conductive particles. Moreover, the permittivity spectrum as a function of frequency is reported for composites of several filler contents, and the Lal and Parshad law was used to correlate the experimental dat

ISSN:0272-8397    

DOI:10.1002/pc.750090207

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractPoly(p‐phenyleneterephthalamide) (PPTA) reinforced molecular composites that utilize a thermosetting epoxy as the matrix polymer have been prepared by anin situpolymerization process. The properties of these molecular composites were compared with those of Kevlar pulp‐filled composites that utilized the same matrix formulation. Study of the curing reactions of these systems using Fourier transform infrared, dynamic mechanical analysis, and nuclear magnetic resonance spectroscopy indicated some differences in the reactivity and ultimate polymer structure of these two systems. A comparison of the properties indicated increased tensile strength, modulus, and heat resistance for the molecularly reinforced material over the conventional fiber‐filled system. Examination of the morphology of the molecular composite system showed that aggregated PPTA molecules are formed during theinsitupolymerization process. This aggregation phenomenon was found to be due to formation of a liquid crystalline polymer solution during processing and final cure. These findings indicate the possibilities that exist in molecular composite processing for simultaneous control of the properties of the matrix and the reinforc

ISSN:0272-8397    

DOI:10.1002/pc.750090208

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry, Fourier transform infrared, and solid‐state carbon 13 nuclear magnetic resonance were used to study the silane coupling agent/epoxy resin interface. Penetration of epoxy into the hydrolyzed silane has been shown. The addition of a solvent can further increase the penetration of epoxy into the hydrolyzed silane by decreasing the viscosity of the epoxy. Bulk models of the gradient in the silane coupling agent/epoxy interface have shown that the concentration of silane and the degree of hydrolysis of the silane can determine the rigidity or mobility of the interphase region. When the silane is hydrolyzed, the possible formation of entanglements may increase the rigidity of the system and decrease the degree of phase separation through the formation of an interpenetrating networ

ISSN:0272-8397    

DOI:10.1002/pc.750090209

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA new boundary element method has been developed for analyzing the flow of sheet molding compound (SMC) during compression molding. The boundary element equations can be used to determine the velocities on the perimeter of the charge. Successive flow front configurations are then generated by a simple explicit updating procedure. This approach was used to predict the flow front progression for elliptical, rectangular, and L‐shaped charges. Comparisons with experimental data for elliptical and rectangular charges were encouraging. The fact that it was possible to obtain reasonable agreement for charges with different shapes and thicknesses lends support to the underlying flow model. Furthermore, valuable insight regarding knit line formation was acquired by analyzing the L‐shaped charge. Results from the boundary element analysis showed that the initial thickness of the charge has a pronounced effect on knit line development. Even though there is considerable industrial experience in making SMC parts, the important role of charge thickness on knit line formation appears to have been largely overlooked. Prior analyses gave no indication of this effect because they were based on lubrication models that were independent of charge thickn

ISSN:0272-8397    

DOI:10.1002/pc.750090210

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750090201

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY