摘要:

AbstractWe studied solvent‐induced crystallization (SINC) in a compatible blend of poly (butylene terephthalate) (PBT) and a polyarylate (PAr) over a range of blend compositions and temperatures; liquid acetone was the crystallizing agent. Acetone transport kinetics were followed by mass uptake measurements in thin films and by optical microscopy. Crystallization kinetics were followed by density measurements. For the 0.2 mm thick films used, those with higher weight fractions of PST (50 to 60 percent by weight) exhibit diffusion controlled transport and crystallization over the entire range of temperatures studied (0 to 55°C). Those with lower weight fractions of PBT (∼30 percent by weight) display Case II sorption and crystal growth controlled crystallization at 0°C. The latter is rare for SINC in homopolymers and results from a sharp reduction in the PBT crystallization rate in the presence of the noncrystallizabl

ISSN:0032-3888    

DOI:10.1002/pen.760271702

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractMultiordering parameter models have been quite successful in rationalizing volume and enthalpy behavior of glasses subjected to various thermal histories in the glass transition range and even at lower temperatures. In the past we suggested a generalization of such models to encompass what is now termed physical aging, i.e., recovery as monitored by mechanical experiments such as creep and stress relaxation. Our initial investigation indicated qualitative agreement between the generalized model and experimental behavior. We have now more completely investigated this area and found a convenient approximation through which behavior can be calculated in most situations without using a distribution of mechanical relaxation or retardation times. Using this technique, we find that essentially quantitative agreement between this model and experimental results is possible only when a very sharp distribution of volumetric recovery times, like that of a single ordering parameter model, is used, Broader distribution functions result in aging behavior which is much more sluggish than observed experimentally. This result is particularly disturbing since such sharp distribution functions have been shown to be incompatible with direct observations of volume recovery.

ISSN:0032-3888    

DOI:10.1002/pen.760271703

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractCompatible polymer blends can be used to test critically the viability of the damped Debye lattice (DDL) model of relaxation in the primary (glass‐to‐rubber) transition region. Since these blends form because of specific intermolecular interaction, the force constants that characterize intermolecular elastic interactions can be controlled to some extent by varying blend composition. The model predicts an unusual sharpening of the stress relaxation master curve of a marginally two‐dimensional DDL upon dilution with a plasticizer. We have prepared an appropriate two‐dimensional DDL by adding modest amounts of partially brominated poly(2,6‐dimethyl 1,4‐phenylene oxide) to polystyrene to form compatible blends. As predicted by the model, sharpening of the stress relaxation behavior upon dilution was observed for all blend compositions and for all diluents used. However, at higher brominated poly(phenylene oxide) concentrations, the anticipated diluent concentration dependence was not always observed and the sharpening of the stress relaxation behavior was less than expected. In similar experiments carried out on diluted homopolymers, the relative values of the solubility parameters of the polymers and the diluents strongly influenced the effectiveness of the diluent in changing the stress relaxation behavior. In this blend system, the particular chemical nature of the diluent was found to be much less important; in fact, the three diluents used all evoked approximately the same behavior despite their having solubility parameters that differed si

ISSN:0032-3888    

DOI:10.1002/pen.760271704

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA novel high pressure polymer solution viscometer has been experimentally evaluated using the polystyrene/ethylbenzene system. The polymer solutions range in concentration from 60 weight percent polystyrene to the pure melt. The overall temperature range is 132°C to 240°C. The shear rates range from roughly 5 s−1to 2000 s−1. It has been concluded that the present method is useful in determining the shear dependent behavior of these volatile solutions, The shear dependent nature of this system is consistent with accepted non‐Newtonian viscosity

ISSN:0032-3888    

DOI:10.1002/pen.760271705

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractTerpolymers containing polybutadiene as a central segment and diblock or random copolymer terminal units of equimolar amounts of styrene andp‐tert‐butylstyrene have been synthesized and evaluated. The structure property relationships were examined by a combination of transmission electron microscopy (morphology), dynamic viscoelasticity measurements, and melt rheological evaluations. The presence ofp‐tert‐butylstyrene was found to lead, under certain circumstances, to thermoplastic elastomers exhibiting good phase separation and mechanical properties at ambient temperature along with Newtonian melt viscosities at low shear rates at elevated temperatures. This latter behavior is in contrast with that exhibited by conventional poly(styrene‐diene‐styrene) triblock

ISSN:0032-3888    

DOI:10.1002/pen.760271706

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA model of a granular bed is used to obtain an estimate of the speed of propagation of intergranular stress waves. In the analysis, a simple elastic contact between neighboring grains is assumed. The model may be extended to include more complex Intergranular interaction mechanisms, but at the expense of such a simple analytical solution as that obtained here. The predicted dependence of compression of a granular bed on compressive load is compared with experimental measurements and is found to describe the relationship very well. The simplified analysis gives a general insight into the dependency of wave speed on bed geometry, indicating for example that while wave speed is independent of grain size, it does depend on the Initial porosity of the bed.

ISSN:0032-3888    

DOI:10.1002/pen.760271707

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA fractional‐life method coupled with dynamic differential scanning calorimetry (DSC) scan was employed to study the kinetics of the isothermal polymerization of the DGEBA (diglycidyl ether bisphenol A)/HHPA (hexahydrophthalic anhydride)/BDMA (benzyl dimethyl amine) resin system. This method avoids the problem of uncertainty in the total heat evolution in the isothermal DSC scan, The reaction orders obtained for this epoxy resin vary from 1.05 to 1.44 in the temperature range 118–135°C and are believed to be more accurate than those determined in previous stu

ISSN:0032-3888    

DOI:10.1002/pen.760271708

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIntegral‐skin foams of rigid polyurethane are sandwich structures consisting of a core layer of closed cells enclosed in rigid surface layers on both sides. We examined the layer composition of integral‐skin foam with the objective of maximum flexural strength, and then studied possibilities of reconciling the strength and thermal insulating properties in housings for evaporators in car air conditioners; i.e., unit cases. This examination showed that the most practical density range (250 ≦ ρpall≦ 500 kg/m3) provides vibratile resistance and thermal insulating properties. In actual car‐running tests, a maximum 0.1 MPa stress was generated on unit cases with overall densities of 350 kg/m3, We found this to be 0.4% of the flexural strength of an integral‐skin foam and 2% of the fatigue strength. In the forcible vibratile test, a stress of 0.5 to 1.0 MPa was generated at the resonance point of a unit case with 250 to 500 kg/m3overall density. We found that these values are 2 to 5% of integral‐skin foam's flexural strength and 10 to 25% of its fatigue strength. These values are of the same level as the conventional unit case made of polypropylene blended with talc. An integral‐skin foam with an overall density of 250 kg/m3, nearly equal to half the weight of polypropylene, has the same level of resista

ISSN:0032-3888    

DOI:10.1002/pen.760271709

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe chain orientation, induced by hot drawing, decreases the sorption capacity of polystyrene due to the tighter packing of macromolecules in the oriented material. Density measurements and decay of birefringence indicate that the loss of orientation Is a much more rapid phenomenon than the thermal shrinkage of the polymer.

ISSN:0032-3888    

DOI:10.1002/pen.760271710

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractAn approach has been developed to estimate the solubility and diffusivity of toxic phosphonofluoridates in high molecular weight polymeric matrices based upon experimentation with nontoxic simulants. This approach is based on Gee's relation for estimating solubility (equilibrium swelling) from knowledge of the solubility parameters for the polymer and the simulant liquids concerned and on Van Krevelen's relation between diffusivity and activation energy of diffusion. The latter is interpolated from a standard plot of activation energy of diffusion against penetrant molar volume. Equilibrium swelling values and diffusivities for toxic alkyl phosphonofluoridates in styrene‐butadiene rubber (SBR) and low density polyethylene (LDPE) were estimated from results of swelling measurements (as a function of time and at three different temperatures) involving the two polymers and a series of nontoxic liquids, similar to the toxic alkyl phosphonofluoridate

ISSN:0032-3888    

DOI:10.1002/pen.760271711

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY