摘要:

Fourier—transform infrared (FT-IR) with digital subtraction method has been applied to investigate the molecular interactions of immiscible polystyrene (PS)/bisphenol A polycarbonate (PC) blends and miscible PS/tetra-methyl PC (TMPC) blends. The FT-IR results show that there are no interactions for PS/PC, and the miscibility of PS/TMPC blends is mainly due to the intermolecular interaction between the phenyl ring of PS and the carbonate group of TMPC. The phenyl ring band of PS is linearly shifted to higher wave number with increasing concentration of TMPC, and the bandwidth at half maximum intensity of the carbonyl band of TMPC is linearly decreased with increasing concentration of PS. The amplitude of the interactional bands is decreased with increasing temperature consistent with LCST behavior of the blend. The miscibility of PS/TMPC and immiscibility of PS/PC has also been discussed in terms of local free-volume, self-interactions, and intermolecular interactions based on the chemical structures of PC and TMPC. Furthermore, the immiscibility behavior for blends of methyl-substituted PS and TMPC, and blends of PS and halogen-substituted PC has been explained in terms of intra and intermolecular interactions caused by steric and/or induction effects.

DOI:10.1163/156855493X00185

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fixation of silane coupling agents to glass fiber was quantitatively determined using pyrolysis-GC/FT-IR to explore the formation of chemical-bonded and physisorbed silanes. The silane coupling agent used was N-phenyl-1-aminopropyltrimethoxysilane (AnPS). In silane treatment, E-glass fiber was dipped into acetic acid solution containing AnPS and was cured under different temperature and time. The fixation of silane was obtained by determining the amount of AnPS at the glass surface after and before washing the treated fiber with methanol. The silane fixation increased with decrease in the silane concentration, but it fell significantly below a lower silane concentration. The change of fixation in curing temperature gave an optimum temperature for the fixing. The dependence of curing time on the fixing ratio showed that the fixation was depressed below the curing temperature of 100°C. These results suggested that more than a specific amount of AnPS deposit on glass fiber was necessary to form silane networks fixed to glass fiber through siloxane bonds. The networks formation was interpreted in terms of the competitive reaction of the silanol group of silane to hydroxyl of glass fiber and to other silane molecules.

DOI:10.1163/156855493X00194

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The achievement of the potential of composites for demanding applications where high specific strength and stiffness are required together with useful toughness is often limited by the available materials processing capabilities to develop specific reinforcement-matrix interface characteristics. Similarly, the elevated temperature stability of advanced composites is dominated by the behavior of internal interfaces. In order to develop effective processing strategies and stable composite designs, it is essential to consider the relevant phase diagrams which for most composites are at least of ternary order. On the basis of these diagrams, it is possible to select compositions of phases which possess desirable properties. In addition to phase diagram data, kinetic data such as the interdiffusion pathway and rates are required to understand and to control the possible interfacial chemical reactions in a composite system. From this basis, reinforcement coatings and barrier layers can be developed to control reactions and allow for in-service lifetime analysis. With solidification processing of composites, melt-reinforcement interactions involved in wetting, solidification reactions, and matrix microstructure evolution can also be evaluated in terms of the phase equilibria and kinetic pathways. Some applications of this approach have been demonstrated in the development of Ti- and A1-based composite systems.

DOI:10.1163/156855493X00202

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An analytical methodology is presented to study the effects of fiber-matrix interfacial bonding strength on global failure and the reliability of graphite/epoxy composite laminates under general multidirectional loadings. It utilizes strength data of laminae, and a micromechanical model of unidirectional tensile strength which is verified by data in the literature on graphite/epoxy laminae with different interfacial strengths (AU-4/828, AS-4/828, and AS-4C/828). The model and data are combined with the Tsai-Hill failure criterion and a method of reliability analysis to evaluate the global reliability of general composite laminates under multidirectional loadings. The strength of composite materials changes remarkably by changing the load angle with respect to reinforcing fibers and stacking sequences. Therefore, optimum material design can be performed under a given loading condition. The proposed method of reliability is utilized in determining the load angle for maximum reliability, and the sensitivity of reliability on the fiber-matrix interfacial shear strength. It is shown that for a [0/90]s graphite/epoxy laminate, if the load is fixed and only its angle with respect to fiber of 0° ply, called , changes, the reliability increases as the interfacial shear strength increases for all values of . The angle 0 is called the load angle. There exists an angle at which the reliability is most sensitive to the fiber-matrix interfacial shear strength. This angle of maximum sensitivity changes when the ratio of applied shear stress to applied tensile stress changes. Furthermore, for any fixed interfacial shear strength, the reliability of the composites changes as a function of the load angle 0, and has a maximum value at a certain angle. This 'optimum' angle shifts from right to left, and approaches 0° as the ratio of shear loading to tension loading (τxy/σx) decreases. On the other hand, the 'optimum' angle approaches 45°.

DOI:10.1163/156855493X00211

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Polymers are responsible for a large proportion of audio/video/computer tape characteristics. Several years ago, the polymers used as a binder were selected only empirically without fundamental study. From this standpoint, the authors have systematically investigated the different effects of functional groups of various polymer binders on electromagnetic performance. As a result, it was found that the proper design of polymer binders offers significant potential for further improvement in magnetic performance. With the recent introduction of high dispersion and high durability binders, it has become clear that the particulate media like a metal tape dominates in the field of higher density recording media such as an 8 mm and Hi-8 video tape, a professional video tape like a Beta CAM SP, D2, D3, UNIHI and 1.2 Gb/s HD, and a DAT streamer tape.

DOI:10.1163/156855493X00220

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor