摘要:

AbstractExperiments aimed at studying the mechanisms of agglomerate breakup due to the application of a simple shear flow field were performed in a cone and plate transparent device. Spherical compacts of carbon black (diameters 1‐2 mm) in a range of different porosites were used in the experiments. Two distinct breakup mechanisms, denoted as “rupture” and “erosion”, were observed. The critical stress for erosion was found to be smaller than that for rupture. Once erosion starts, it continues for very long times. Rupture occurs shortly after reaching a critical stress and concludes abruptly. For this analysis of rupture, the dimen‐sionless group\documentclass{article}\pagestyle{empty}\begin{document}$\alpha {\rm = \{ }\eta {\rm .}\mathop \gamma \limits^{\rm .} {\rm /K'}\phi ^{\rm 4} {\rm \} }$\end{document}, which is the ratio of applied stress to cohesive strength, was found to be a significant parameter for determining the final particle size distribution. The size analysis of fragments produced by shearing pellets for 1 minute showed a lognormal distributi

ISSN:0032-3888    

DOI:10.1002/pen.760301202

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe composition dependence of tensile yield stress (σyc), and the effects of filler particle shape and surface treatment were investigated for polypropylene (PP) filled with CaCO3or with Mg(OH)2. Poor adhesion between PP and CaCO3accounted for a decrease of σycwith increasing σf. In spite of the poor adhesion between PP and Mg(OH)2, σyceither slowly decreased with increasingVfor remained constant up toVf= 0.25. Surface treatment of the fillers facilitated better dispersion in PP. On the other hand, σycwas reduced due to the lower thermodynamic work of adhesion (WA). The semiempirical one‐parameter equation proposed by Turczanyi, Pukanszky, and Tüdüs (TPT) was considered plausible and was employed in the study of the effects of matrix‐filler i

ISSN:0032-3888    

DOI:10.1002/pen.760301203

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractEffects of the variation of adhesion strength σAon the tensile yield behavior of particulate filled polypropylene (PP) were investigated. To enhance adhesion of PP toward calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2), maleated PP (MPP) was added to PP in various ratios. σAvaried from 10‐46 MPa. σAcalculated from the Leidner‐Woodhams model are in good agreement with SEM micrographs of the composite fracture surfaces. Dependences σycvs. σA, at constantVf= 0.18, were investigated and analyzed in terms of existing models. Using the Turczanyi, Pukanszky, Tüdös model (TPT) for the PP/CaCO3composite, an effective interlayer “thickness” (teff) and the yield stress of the immobilized PP (σyi) were calculated. Bothteffand σyiincreased with enhancing

ISSN:0032-3888    

DOI:10.1002/pen.760301204

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(ethylene 2,6, naphthalene dicarboxilate), PEN, is very similar to poly(ethylene terephthalate), PET, in its chemical structure and was, therefore, expected to exhibit similar processing characteristics. We, however, observed a few problems during stretching of PEN, the most important of which was necking behavior at 145°C, which is betweenTg(117°C) andTcc(195°C). This is usually observed in PET only when it is stretched close to or belowTg. At temperatures betweenTgandTcc(cold crystallization temperature) PET stretches rather uniformly. The temperature window for film stretching appears to be rather wide, but our results indicate that this is not the case. Films stretched to high stretch ratios become uniform due to propagation and final disappearance of necks as a result of stress hardening. Our attempts at stretching these films at higher temperatures indicated that necking is eliminated, but so is stress induced crystallization, which causes stress hardening (unless high stretching rates are employed). The presence of stress hardening is essential for obtaining high quality, uniform films of these polymers. In addition, at high temperatures thermally activated crystallization which starts dominating the structure development, detrimentally affects the general appearance of the films. In brief, the PEN films we investigated have a narrower processing window than was anticipated based on their thermal behavior alone. At elevated temperatures the films are sensitive to the rate of stretching even more than typical PET processed at comparable conditions. The uniformity of the films depends on the stretch ratio, stretching mode, ratio(s) and rates and temperature. WAXS studies on the films indicate that the macromolecules packed into the low temperature crystal modification. In addition, WAXS pole figure studies suggest that naphthalene planes preferentially orient parallel to the film surface during biaxial stretching. The biaxially stretched films were observed to exhibit a bimodal chain orientation as evidenced by pole figure analysis of the (010) plan

ISSN:0032-3888    

DOI:10.1002/pen.760301205

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe behavior of epoxy mortar was studied under various curing conditions, temperature and strain rate. The effect of aggregate size and distribution on the mechanical properties of epoxy mortar was also studied. Epoxy mortar with a uniform fine sand was cured at various temperatures to determine the optimum curing condition. The strain rate was varied between 0.01 to 6 percent strain per minute and the testing temperature between 22°C and 80°C. The strength, modulus, and compressive strain‐strain relationship of polymer mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of epoxy mortar are quantified. Compared to the uniformly graded fine aggregate fillers the gap‐graded aggregates produced polymer mortar with better mechanical properties. The compressive modulus and splitting tensile strength of epoxy mortar are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress‐strain behavior of epoxy mortar. The constitutive relationship parameters are also related to the testing temperature and logarithmic stra

ISSN:0032-3888    

DOI:10.1002/pen.760301206

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractIn theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a “model” LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Doirain size was found to go through a minimum as mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that an abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion‐coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene a

ISSN:0032-3888    

DOI:10.1002/pen.760301207

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760301201

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY