ISSN:0032-3888    

DOI:10.1002/pen.760281202

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA series of polyurethane‐urea/polyvinyl simultaneous interpenetrating polymer networks (SINs) were prepared starting from a mixture of isocyanate prepolymer blocked with N‐(1‐1′‐dimethyl‐3‐cxobutyl) acrylamide oxime, chain extender, vinyl monomers, and catalysts. Their physical properties and morphology were investigated using differential scanning calorimetry, dynamic mechanical measurements, and small‐angle X‐ray scattering. The polyurethane‐urea networks examined were two‐phase in nature. The vinyl network was formed with diacetone acrylamide oxime, trimethylolpropane trimethacrylate, and N‐vinyl‐pyrrolidone. Calorimetric analyses revealed that the polyether soft segment phase separated within the SINs. At higher temperature, dynamic mechanical measurements demonstrated the presence of only one glass transition temperature (Tg) intermediate in temperature to theTgof the vinyl network and theTgof the urethane hard phase. This is indicative of chain entanglement (interpenetration) between the vinyl network and the polyurethane hard segments resulting in a two‐phase morphology. Small‐angle X‐ray scattering analyses provided measurements of diffuse phase boundary thickness, phase mixing, and domain size distribution. Appreciable interfacial thickness was not observed and thus phase mixing occurred within the phases. Domain size distribution indicated that high network constraints hindered the development of domains an

ISSN:0032-3888    

DOI:10.1002/pen.760281203

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractMolecular composites, also called polymeric liquid crystals (PLC), are contrasted with the traditional composites; the name heterogeneous composites is proposed for the latter. Advantages of blending PLCs with ordinary engineering polymers are discussed. Results reported for blends of poly(ethylene terepthalate) (PET) with a PLC containing sequences of PET and p‐hydroxybenzoic acid (PHB) include thermophysical properties, melt rheology, mechanical properties of solid blends, and scanning electron microscopy of fracture surfaces. A model called the island model was developed to explain the results: One assumes that the lines of force as well as propagating cracks tend to concentrate in the phase rich in the more flexible engineering polymer, avoiding the islands rich in the liquid‐crystalline phase. This prevails until the phase inversion occurs. Predictions from the model are fully confirmed by the experimental evide

ISSN:0032-3888    

DOI:10.1002/pen.760281204

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractPhase continuity has been explored as a function of composition for three two‐phase polymer blends produced by mixing in the melt: polystyrene/poly(methyl methacrylate), polystyrene/cis‐polybutadiene, and poly(methyl methacrylate)/ethylene‐propylene rubber. The condition for dual phase continuity Is the application of shear close to phase inversion and this can be predicted fairly accurately using the relation\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{\eta _1 (\mathop {\gamma)}\limits^.}}{{\eta _2 (\mathop {\gamma)}\limits^.}}\sim\frac{{\varphi _1}}{{\varphi _2}} $$\end{document}where 1 and 2 are the blend components, η is viscosity,\documentclass{article}\pagestyle{empty}\begin{document}$\mathop \gamma \limits^.$\end{document}is the shear rate in the mixing device used to produce the blend and ϕ is volume fraction. The co‐continuous materials, which we call Interpenetrating polymer blends (IPBs) are non‐equilibrium structures and are subject to disruption by changes in

ISSN:0032-3888    

DOI:10.1002/pen.760281205

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe impact strength to stiffness balance of a toughened polypropylene copolymer was modified through the addition of mineral fillers. The stiffness was improved over the base resin value for all formulations. However, the impact strength exhibited complex behavior. The fracture toughnessGccalculated using the linear elastic fracture mechanics theory was indicative of the materials resistance to crack propagation. TheGcvalues were modified significantly with the addition of fillers and for some formulations was greater than the base resin value. The LEFM analysis indicates that this is due to an increase in the damage zone sizerpwhere the energy absorbing mechanisms are concentrated. However, the specific energy absorbed per unit volume decreased with the addition of fillers. The total energy to fracture measured using unnotched samples was indicative of crack initiation and crack propagation energies. This upper bound value decreased for all formulations indicating a reduction in the crack initiation resistance, in the presence of stress concentrating heterogeneities in the filled systems.

ISSN:0032-3888    

DOI:10.1002/pen.760281206

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractDirect photo‐patterning of polyimide (PI) films was done in two ways, both based upon the modification of the PI‐precursor, the polyamic acid (PAA), by derivatives of methacrylic amide. In the first method, a photoreactive PAA is prepared by partially (25 mole percent) neutralizing PAA with N‐(N′N′‐dimethylarnino)propylmethacrylic amide and completing the neutralization with methacrylic amide (75 mole percent). In the second method the PAA is esterified, e.g. with N‐hydroxyethyl‐N‐methylmethacrylic amide, through its isourea derivative. The modified PAAs are processed like conventional negative photoresists. In the first method, the photopolymer formed by selective UV exposure is bound to the PAA by intermaeromolecular complexation, causing insolubility in the developer. The second method, which was investigated only qualitatively, provides crosslinked patterns. In both cases a pure PI film is left upon imidization at 350°C. The first method proved to be well‐suited to making the potential well structure in an electrophoretic image display. These wells must have strictly vertical walls (12 μm high) with metallized top faces. It was found that mask contact at “molecular distance” is not needed for the exposure of the photosensitive PAA: vertical walls could be made by simply adapting the developer after contact exposure. This is explained, tentatively, by the typical characteristics of the polymer‐polymer complex upon development. The potential well structure could now be made i

ISSN:0032-3888    

DOI:10.1002/pen.760281207

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractFluid absorption studies have been made for a polyetherimide thermoplastic film and a unidirectional composite of the thermoplastic with graphite fibers immersed in water, JP4 jet fuel, ethylene glycol, and hydraulic fluid. The changes in the weight, thickness, and tensile properties were measured for the film. The changes in the flexural properties of the composite were measured for specimens whose fiber orientation was transverse to their length. Only the hydraulic fluid, which caused an erosion or dissolving of the resin at the specimen surface, affected the film's properties. Both the water and the hydraulic fluid affected the flexural properties of the composite, due to capillary absorption along the fiber‐resin interfac

ISSN:0032-3888    

DOI:10.1002/pen.760281208

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760281201

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY