摘要:

AbstractA semi‐empirical expression for predicting phase continuity and inversion in polymer blends and simultaneous interpenetrating networks (SINs) was developed and examined experimentally. A rheological model based on the volume fraction, ϕ, and viscosity, η, led to the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{{\rm \eta }_{\rm 1} }}{{{\rm \eta }_{\rm 2} }} \cdot \frac{{\phi _{\rm 2} }}{{\phi _{\rm 1} }} \cong 1 $$\end{document}as the criteria for dual phase continuity for phases 1 and 2. This relation was evaluated for two systems: a castor oil polyester‐urethane/polystyrene SIN, and a mechanical blend of polystyrene and polybutadiene. Literature data was also examined. A gradual phase inversion was found, with a region of dual phase continuity in between. While predictions of phase continuity were confirmed for the mechanical blends, they were not confirmed for the SIN system. This was probably due to rapid gelation at the point of phase inve

ISSN:0032-3888    

DOI:10.1002/pen.760260802

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA water‐displacement method was used to measure the specific volume of three styrene‐butadiene‐styrene (SBS) block copolymers over the temperature range 4°C to 65°C. The polymers contained 0.268. 0.293, and 0.482 weight fraction polystyrene, varied in molecular weight, and are known to be phase‐separated at these temperatures. Coefficients of thermal expansion were also obtained and found to be constant over this temperature range. Results are compared with various models of composite behavior, the most successful of which is the linear mixing rule which gives good predictions over this composition range. Deviations for specific volume are negative, and for expansion coefficient positive, from the linear rules. More complex behavior is suggested, however, and this is interpreted in terms of microstructural characteristics. Some apparent contradictions in data reported by other workers are explained. Results are presented also for samples stretched uniaxially up to 300 percent strain; only slight evidence of dilation is seen at 22°C. but increase of the expansion coefficient is mor

ISSN:0032-3888    

DOI:10.1002/pen.760260803

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of pressure on the densification of amorphous polymers in the Injection‐molding process is examined. Density distributions in molded polystyrene slabs were measured for several well‐defined molding histories. In all cases the density of the molded part was spatially inhomogeneous, and its distribution in the slab was closely related to the pressure and temperature histories that prevailed in the molding cavity during the process cycle. The density profile in the gapwise direction followed a characteristic “parabolic” pattern with a minimum at the midplane of the slab. A simple phenomenological model, based on the pressure‐induced densification effect, was constructed to explain the observed density profiles, and close agreement with experimental data was found. Annealing of the molded article at a high temperature (

ISSN:0032-3888    

DOI:10.1002/pen.760260804

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA systematic design of the classical “coat hanger” die is proposed and tested experimentally. The objectives of the design are 1. distribution of the polymer over the width of the die before it reaches the final lip section for thickness adjustment, 2. invariance of distribution to flow rate, 3. invariance to changes in polymer viscosity, and 4. uniform average residence time. The die design is based on a flow model which assumes power‐law viscosity, steady shear flow In each cross‐section, uniform temperature, and separation of the flows into a manifold component and a component in a slit section of uniform height. The design corrects for an oversimplification of the pressure gradient that was applied in previous studies; and it differs from previous designs by suggesting a rectangular cross‐section for the manifold. Applications to side‐fed dies for extrusion blow molding and to a sheet extrusion die achieved uniform distribution and did not require any additional flow corrections (such as choker bars or flexible lips). With the new design, the lip region of the die can freely be used for thickness control, fine tuning, or further shaping of th

ISSN:0032-3888    

DOI:10.1002/pen.760260805

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractUniaxial tension tests to the yield point were performed on polyethylene as a function of temperature from 21 to 117°C at a strain rate of 2 min−1. At 21, 45, and 69°C, measurements were also made at strain rates from 0.02 to 8 min−1. Yield energy was found to be a linear function of temperature extrapolating to zero at the melting point (140°C). The ratio of thermal to mechanical energy to produce yielding is about three times smaller than for glassy amorphous polymers. The ratio of yield stress to (initial) Young's modulus is 0.021 at room temperature and increases to 0.059 at 117°C. Also this ratio was found to decrease with log strain rate. For instance, at 21°C for a strain rate of 0.02 min−1the value was 0.023, while at 8 min−1this value decrea

ISSN:0032-3888    

DOI:10.1002/pen.760260806

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe preparation of Nylon‐6 via the initiated anionic polymerization of EE‐caprolactam is characterized by rapid reaction rates displaying marked auto‐acceleration. A mechanistic approach has been taken to analyze the kinetics of this system and has resulted in the postulation that the auto‐acceleration is directly linked to a polymer chain degradation reaction. This reaction is significant even in the early stages of the polymerization and in many cases becomes the dominant mechanism for the production of reactive end groups, thereby controlling the overall reaction rate. A kinetic model is presented which is capable of differentiating between polymerizations carried out with different levels and ratios of catalyst and initiator, and contains but two rate constants—one for the propagation reaction and one for the degradation reaction. Predictions of the model are compared to experimental rate data derived from using both mono‐and difunctional initiators and close agreeme

ISSN:0032-3888    

DOI:10.1002/pen.760260807

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe optical properties of conventional, free‐radical polymerized low density polyethylene (LDPE) blown films are due essentially to surface irregularities that develop during fabrication. Past studies have shown that the extent to which these irregularities occur (and therefore optical properties) correlates well with the melt elasticity of the resin. Specifically, it has been shown that resins with higher melt elasticity result in films with poorer optical properties. However, it was recently reported that the optical properties of film blown from a Sci of three generically similar LDPE resins were found to correlate with the crystallization kinetics of the resins. Specifically, it was reported that the resins that exhibited faster crystallization rates produced films with better optical properties. This present work shows, however, that this apparent correlation is only coincidental. It has been shown that resins exhibiting faster crystallization rates do not necessarily result in films with better optical properties. On the other hand, it has been shown that resins with higher melt elasticity consistently result in films with poorer optical propertie

ISSN:0032-3888    

DOI:10.1002/pen.760260808

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThein situpolymerization of glycidyl methacrylate in wood, in the presence of uranyl nitrate, (UN), and/or 2,2′‐azo‐bis‐isobutyronitrile, (AIBN), has been investigated in the temperature range 55°‐72°C. The course of the polymerization reaction was followed by measurement of tan 5 in an automated Rheovibron viscoelastometer. The kinetics, studied by applying the Guggenheim method to the data, showed the polymerization to be first order whether catalyzed by UN or initiated by AIBN. The activation energy (Eα) for AIBN‐initiated polymerization was 121 kJ/mol, and was unaffected by varying monomer concentration in acetone. On the other hand,Eαfor the UN‐catalyzed polymerization was found to be 59.1 and 73.5 kJ/mol respectively for the neat and 50 percent monomer concentration reaction mixture. The enhancement inEαis attributed to the complexatton of the dioxouranium (VI) ion in the presence of solvent acetone, with consequent reduction in

ISSN:0032-3888    

DOI:10.1002/pen.760260809

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760260801

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY