ABS Composites Research Articles

Structural searches using isopointal sets as generators: densest packings for binary hardsphere mixtures

Algorithms to search for crystal structures that optimize some extensive property(energy, volume, etc) typically make use of random particle reorganizations in thecontext of one or more numerical techniques such as simulated annealing, geneticalgorithms or biased random walks, applied to the coordinates of every particle in theunit cell, together with the cell angles and lengths. In this paper we describe therestriction of such searches to predefined isopointal sets, breaking the problem intocountable sub-problems which exploit crystal symmetries to reduce the dimensionalityof the search space. Applying this method to the search for maximally packedmixtures of hard spheres of two sizes, we demonstrate that the densest packedstructures can be identified by searches within a couple of isopointal sets. For theA2B system, the densest known packings over the entire tested range0.2 < rA/rB < 2.5, including some improvements on previous optima, can all be identified by searcheswithin a single isopointal set. In the case of the AB composition, searches of twoisopointal sets generate the densest packed structures over the radius ratio range0.2 < rA/rB < 5.0.

Mechanical Properties of PVC/ABS Composite Material

We investigate the mechanical properties of Poly Vinyl Chloride (PVC)/ acrylnitrile-butadiene-styrene copolymer (ABS) composite material with an impact testing machine，a material testing machine and other accessory devices. The result shows that the mechanical properties of PVC/ABS composite are a function of composition, the addition of ABS improved the mechanical properties of PVC/ ABS composite，the impact strength and elongation at break rise significantly with increasing ABS content in PVC/ABS composite and appears maximum value，While the tensile strength and modulus almost decrease monotonously with increasing ABS content in PVC/ABS composite.

Effect of Co-Monomer Content on Rheological Property of Sawdust/ABS Composites

Effect of co-monomer content in Acrylonitrile-Butadiene-Styrene copolymer (ABS) on the rheological property of sawdust reinforced ABS composites was investigated using capillary die rheometer. Three grades of commercial ABS resin were used. Sawdust from Para rubber tree treated with N-2(aminoethyl) 3-aminopropyl trimethoxy silane was blended with ABS by melt blending process using twin-screw extruder. From the results, shear thinning behavior was found for all of composites in the same shear rate ranges for testing that were investigated. At the low shear rate, the composites which contain higher acrylonitrile content, showed higher viscosity. At high shear rate, the viscosity of each co-monomer dependent composites tends to come close to each other on the curves. In this study, Carreau’s model was used for curve fitting and those parameters were also determined. Die swell ratio of the composites tended to increase at the initial ranges of shear rate of 10-500 s-1, and then the swelling ratio value decreased dramatically once the shear rate were further applied. The molecular weight has more effects than comonomer content on the die swell behavior i.e., at the same molecular weight, composites with higher butadiene content show higher swelling ratio.

Tensile and flexural properties of injection-moulded short glass fibre and glass bead ABS composites in the presence of weldlines

The effect of weldline on tensile and flexural properties of ABS reinforced with short glass fibres (ABS/GF) and spherical glass beads (ABS/GB) was investigated as a function of glass fibre and glass bead concentrations. The weldline was formed in the moulded specimens by direct impingement of two opposing melt fronts (i.e. cold weld). It was found that elastic modulus of ABS/GF composites, with or without weldlines increased linearly with increasing volume fraction of fibres (ϕf), according to the rule-of-mixtures for moduli. The presence of weldline reduced tensile and flexural modulus of the ABS/GF composites. Weldline integrity factor for elastic modulus of ABS/GF composites decreased linearly with increasing ϕf. Results showed that tensile and flexural strength of ABS/GF increased with increasing ϕf in a nonlinear fashion. Flexural strength was consistently greater than tensile strength for the same ϕf. Weldline affected both strengths in a significant way; weldline integrity factor decreased with increasing ϕf and was independent of loading mode. Tensile and flexural modulus of ABS/GB composites increased linearly with increasing volume fraction of glass beads (ϕb), showing no loading mode dependency. Although modulus of the ABS/GB system was not affected significantly by the weldline, its strength was affected, and more so in flexure than in tension. Weld and unweld strengths decreased with increasing ϕb in both tension and flexure according to Piggott and Leidner relationship; for the same ϕb, flexural strength was always greater than tensile strength. Weldline integrity factor for tensile strength of ABS/GF system was considerably lower than that for ABS/GB system but weldline integrity factor for flexural strength was almost the same for the two composite systems.

Evolutionary Approach in Copolymer Sequence Design

AbstractSummary: In this work, we discuss a simple evolutionary algorithm that introduces a “selection pressure” under which two‐letter (AB) copolymer sequences can mutate and transform into the sequences tuned to microphase separation transition (MIST). In particular, we are interested in determining how a sequence of A and B units should be organized in order to reach maximum length scale for MIST at a given AB composition. It is found that such sequences are similar to those known for tapered or gradient copolymers exhibiting strong composition inhomogeneity along their chain. The problems of the evolution of copolymer sequences are considered from the viewpoint of emerging of information complexity in the sequences in the course of this evolution.

Reduced Susceptibility of Recombinant Polyclonal Antibodies to Inhibitory Anti-Variable Domain Antibody Responses

The immunogenicity of therapeutic Abs is a concern as anti-drug Abs may impact negatively on the pharmacodynamics and safety profile of Ab drugs. The factors governing induction of anti-drug Abs are not fully understood. In this study, we describe a model based on mouse-human chimeric Abs for the study of Ab immunogenicity in vivo. Six chimeric Abs containing human V regions and mouse C regions were generated from six human anti-Rhesus D Abs and the Ag-binding characteristics of the parental human Abs were retained. Analysis of the immune response toward the individual chimeric Abs revealed the induction of anti-variable domain Abs including anti-idiotypic Abs against some of these, thereby demonstrating the applicability of the model for studying anti-drug Ab responses in vivo. Immunization of BALB/c, C57, and outbred NMRI mice with a polyclonal composition consisting of all six chimeric Abs demonstrated that the immunogenicity of the individual Abs was haplotype dependent. Chimeric Abs, which were nonimmunogenic when administered individually, did not become immunogenic as part of the polyclonal composition, implying the absence of epitope spreading. Ex vivo Ab-binding studies established a clear correlation between the level of immunogenicity of the Abs comprised in the composition and the impact on the pharmacology of the Abs. These analyses demonstrate that under these conditions this polyclonal Ab composition was generally less susceptible to blocking Abs than the respective mAbs.

Application of Statistic Estimation to Weldline Strength of Injectionmolded Thermoplastic Composites

The injection molding of thermoplastic composite materials has become an important process in industry, due to the possibility of producing near shape article having exceptional physical and mechanical properties. However there are still some problems that confound the overall success of this technology. The forming of weldlines wherever polymer flow fronts meet is one of them. In this report, an L’18 experimental matrix design based on the Taguchi method was conducted to study the effect of different processing parameters on the weldline strength of injection-molded thermoplastic composites. Experiments were carried out on a 4.1 oz reciprocating injection molding machine. The materials used were acrylonitrile–butadiene–styrene, and 20 and 30% glass-fiber-filled ABS composites. A plate cavity with an obstacle in the center was used to create a weldline. After molding, the weldline strength of the composites was determined by a tensile tester. Various processing variables were studied in terms of their influence on the weldline strength of injectionmolded composites: melt temperature, mold temperature, melt filling speed, melt filling pressure, packing pressure, and size of the obstacle. For the factors selected in the experiments, size of obstacle and melt temperature were found to be the important parameters affecting the weldline strengths of injection-molded composites. The weldline strength of virgin material increased with the distance from the obstacle, while the weldline strength of composites decreased with the distance.

MINORITY STUDENT SUCCESS: THE ROLE OF TEACHERS IN ADVANCED PLACEMENT PROGRAM® (AP®) COURSES

ABSTRACTThis project described the characteristics and teaching behaviors of those successfully teaching AP® Calculus AB and AP English Literature and Composition to underrepresented minority students. Its purpose was to assist educators in improving the participation and performance of underrepresented minority students in AP classes. Study results showed successful teachers of minority students are good teachers for all groups. They express a high opinion of students, both majority and minority, and hold them to high standards. They make sure that students understand and can apply the fundamental concepts in the discipline. They also help students and parents understand and feel comfortable about college.

Investigation of some physicochemical properties of camphor sulfonic acid (CSA)-doped poly(o-anisidine) (PoAN) and CSA-doped PoAN/ABS composites

Camphor sulfonic acid (CSA)- doped poly(o-anisidine) (PoAN) has been found to possess the electrical conductivity of 10 S/cm. This value is rather low compared to that of ('200 S/cm) CSA-doped polyaniline, which may arise from a limited transformation of coil-like conformation to an expanded one. Viscosity data and optical absorption spectra provided strong evidence for the existence of coil-like CSA-doped PoAN chains in m-cresol. The shift of IR bands of benzenoid and quinoid rings toward a lower wave number and the appearance of the bands at '1600 and 1173 cm 21 (the IR is inactive but becomes active on doping) suggested the protonation of CSA-doped PoAN. The thermogravimetric profile of CSA-doped PoAN showed a five-step decom- position pattern with the thermal stability up to 134 °C. The mass spectra taken simultaneously with the thermogram revealed that dopant CSA is completely elimi- nated around 360 °C, but the breakdown of polymer chains does not occur very briskly at this temperature. Composites of CSA-doped PoAN with insulating acrylonitrile- butadiene-styrene copolymer (ABS) were fabricated, and it was found that the com- posites showed a percolation behavior in which the electrical conductivity rose sharply at about 4 weight % of CSA-doped PoAN in the ABS composite. The STM data demonstrated the formation of a continuous path at the percolation threshold. The Poole-Frenkel effect was observed for the conduction scheme in the CSA-doped PoAN/ ABS composite. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4596 - 4604,

Fracture Mechanisms of Short-Fiber-Reinforced ABS Composites by AE Technique. Effect of Fiber Content.

Two specified loads, Pb and Pc, of short-fiber-reinforced ABS composites with various fiber contents are determined by the stress intensity factor method. The loads of Pb and PC determined by this method are in good agreement with loads determined by the AE energy gradient method. The damage at the notch tip is observed through a monitor microscope at or near the loads of Pb and PC. The fiber breakage estimated from AE frequency analysis at the loads is considered to be the dominant factor of the damage mode. It was found that the loads of Pb and Pc are important parameters to clarify the fracture mechanisms of the composites.

A dielectric relaxation study of self and heteroassociation in binary liquid mixtures of three pyrrolidinones with alcoholes and water

AbstractNine binary mixture systems AB are considered, where A = 2‐pyrrolidinone, N‐methyl‐2‐pyrrolidinone or N‐cyclohexyl‐2‐pyrrolidinone and B = water, methanol or ethanediol. Their complex permittivity, as measured in the 20 MHz to 36 GHz range at 20°C, is interpreted by a model supported analysis. It applies in particular an empirical correlation between relaxation time and viscosity as established for the case of rigid molecules, relaxing by rotational tumbling. From this, constraints are obtained for those spectral components which are due to species of that category. The procedure yields, among others, for any system a spectral component which can be ascribed to heteroassociates of probably definite AB or AB2 composition. Again with any system, self association of B type molecules is observed, which is strongly affected by addition of A. Special relaxation features of some substances are also considered.