摘要:

AbstractGlassy crosslinked networks were prepared by copolymerization of methyl methacrylate with up to 5.2 mole‐percent of ethylene and triethylene dimethacrylates. The moduli of these materials were measured by tensile and two dynamics methods: forced resonance vibration and ultrasonic. Impact strength were measured using the Izod geometry and Sharpy notched samples to induce brittle fracture. The increase in the length of the crosslinking agent caused an increse in the deformability and impact strength of these materials without any effects in the modul

ISSN:0032-3888    

DOI:10.1002/pen.760211202

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractA capillary rheometer has been designed and built which is capable of making measurements in the shear rate range: 100 s−1<\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}<3 × 106s−1. The rheometer uses the injection unit of an injection molding machine. A modification of this rheometer has been built which consists of two dies in series. Both dies may be used for rheometric purposes, but the second die is intended primarily to act as a valve to allow the mean pressure to be varied in the first die, while keeping the pressure drop constant. In this way the pressure dependence of viscosity may be measured in the injection molding shear rate range. Measurements have been made on unfilled and short glass fiberreinforced polypropylene melts and flow curves covering seven decades of shear rate are presented for the unfilled material. The temperature of the extrudate may be as much as 70°C higher than the barrel temperature. Two effects, shear heating and compression heating, contribute towards this temperature rise, and calculations of the extrudate temperature are in good agreement with measured values. At high shear rates the viscosity is affected by the pressure needed to drive the flow. The effect of pressure on the viscosity outweighs the effect of temperature on the viscosity at high shear rates. A value for the pressure coefficient of viscosity of unfilled polypropylene β = 0.0058 m2MN−1has been

ISSN:0032-3888    

DOI:10.1002/pen.760211203

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper describes the results of a theoretical and experimental study on the rheology of thermoplastics subjected to mechanical effects at extrusion conditions. The spiral flow of non‐Newtonian systems has been studied and quantitative relationships obtained for its description, which are suitable for engineering. The effect of rotational low‐frequency large‐amplitude vibrations on the flow of melts in the extruder's head of simple (circular) and complex cross sections has been studied and an analysis provided for flow with small‐amplitude high‐frequency (ultrasonic) superimposed vibrations. The energy efficiency of cyclic deformation upon extrusion has been estimated. The investigation has provided recommendations for the application of complex shear as a method of directed action on the relaxation and, hence, rheological characteristics of polymers. This opens up new possibilities for the intensification of the extrusion processes and compositions based on therm

ISSN:0032-3888    

DOI:10.1002/pen.760211204

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractNon‐monotonic continuous curves of torque as a function of shaft speed,M(N), have been obtained for a high molecular weight high density polyethylene (HDPE) from measurements obtained with a torque rheometer (Haake Rheocord). Previous papers have given theoretical demonstration of the non‐monotonic character of the shear stress‐shear rate function,s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}), which makes it possible to explain the extrusion behavior of a high molecular weight HDPE. In capillary rheometry, it is not possible to obtain the values ofs(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) into the “well zone” of this function because the compressibility of the polymer creates a phenomenon of oscillation in the barrel affecting the die output flow rate and the pressure loss. TheM(N) function measured by the Haake Rheocord is a complete representation of thes(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function, although the capillary rheometer only gives a partial representation of this function. The transformation of theM(N)function intos(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) is quite difficult because of the complex geometry of the Haake Rheocord measuring head. The “critical points” of thes(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function in the capillary rheometer (appearance of oscillations), can be correlated to the maximum points of theM(N) function in the Haake Rheocord at constant temperature. The non‐monotonic aspect of thes(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function provides an important technological application: extrusion of a high molecular weight HDPE at an increased flow rate at l

ISSN:0032-3888    

DOI:10.1002/pen.760211205

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe microstructural changes in isotactic polypropylene (PP), subsequent to quench from the melt to aroundTgwere studied using dynamic mechanical loss, volume dilatometry, small and wide angle X‐ray scattering, infrared and NMR spectroscopy. The β‐transition loss tangent and the specific volume decreased linearly with logarithm of aging time. Dynamic mechanical loss and NMR spectroscopy results established that amorphous chain mobility reduced during aging. X‐ray and IR techniques showed that the crystallinity, the crystalline density, and the average chain conformation do not change during aging. Tensile tests indicated that diffusion of air or moisture into the polymer is not a competitive mechanism for the aging phenomenon. A simple free‐volume model is quantitatively consistent with these observations. The fraction of the material which cannot age increased as the quench temperature decreased. Further, at lower temperatures a portion of the nonageable fraction is shown to reside in the amorphous

ISSN:0032-3888    

DOI:10.1002/pen.760211206

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractExperimental results on flow birefringence and thermal conductivity measured under shearing strain conditions for liquid polydimethylsiloxane are presented. Both phenomena show similar dependency on strain rate, and this dependency is attributed to net orientation of the macromolecules. An orientation model is presented and is shown to be qualitatively correct.

ISSN:0032-3888    

DOI:10.1002/pen.760211207

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractPrevious experiments have shown thatTgof a partially cured thermosetting system can be measured with conventional thermal scan methods only if no appreciable additional cure occurred during the scan. For high temperature performance systems, the partially curedTgis often at a temperature where kinetics rate is very rapid, causing either an observation of a more advanced curedTg, or only the completely cured system'sTg[Tg(∞)]. Two methods to interpolate theTginformation in spite of additional cure are presented and illustrated with an epoxy resin as a testing material. The Isocure State Curve method is demonstrated with a two‐step curing experiment with the Torsion Impregnated Cloth Analysis (TICA) technique, which is a forced torsion measurement on the Rheometrics mechanical spectrometer, with the resin impregnated on a glass cloth specimen. The calibration method is demonstrated by the post cure experiments of TICA, using the time to loss modulus maximum, and the softening parameterRas the calibration paramet

ISSN:0032-3888    

DOI:10.1002/pen.760211208

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe reaction kinetics at 70°C were investigated for the suspension polymerization of methyl methacrylate initiated by benzoyl peroxide in the presence of variable amounts of dodecyl mercaptan. A dilatometric method designed to follow a suspension polymerization was used. It showed that the autoacceleration of the rate of polymerization begins at higher conversions and becomes less pronounced as the concentration of chain transfer agent is increased. The investigations focused on the determination of the viscosities of the reaction mixtures at the onset of autoacceleration. It was concluded from the flow curves obtained for different reaction mixtures that there exists a critical solution viscosity at which the autoacceleration begins, which supports the accepted theory about the nature of this phenomenon. Measured at a shear rate of 10,000 s−1and at 25°C this viscosity was found to equal 0.6 poise regardless of the molecular weight of the growing poly

ISSN:0032-3888    

DOI:10.1002/pen.760211209

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of polyester and nylon carriers on the durability of metal joints bonded with the modified epoxide adhesive BSL 312 has been examined. Joints have been exposed to air at 50°C and 100 percent RH for periods of up to 10,000 h. Some joints were under tensile stress and this seems to have no effect on durability. Carriers cause a slight lowering of the strength of dry joints, but they appear to have negligible effect on joint durability. An analysis of water distribution in exposed joints implies that the rate of strength loss is dependent upon the rate at which water enters joints by diffusion

ISSN:0032-3888    

DOI:10.1002/pen.760211210

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractMany commercial polymers contain water which must be reduced to a lower level for application. The drying behavior of polystyrene (PS), molecular weight 12,000, and flow characteristics suitable for extrusion and injection molding, have been studied. A laboratory tray dryer was used at temperatures below the glass transition temperature of PS (Tg∼ 373 K). Effects of air flow rate (from 0.5 to 3.5 liters/s), temperature (from 323 to 373K) and relative humidity (from 0.5 to 25 percent) on retained water in PS were measured, and from those effects the effective diffusion coefficients (D) have been deduced as:\documentclass{article}\pagestyle{empty}\begin{document}$$ D\left(T \right) = D_0 \cdot e^{{{ - \Delta E} \mathord{\left/ {\vphantom {{ - \Delta E} {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} = 3.6 \times 10^{ - 5} \cdot e^{{{ - 294} \mathord{\left/{\vphantom {{ - 294} T}} \right. \kern-\nulldelimiterspace} T}} \ln D\left({X\%} \right) = \ln D_{X\%= 0} + aX\%= - 19.30 + 4.0\left({X\%} \right) $$\end{document

ISSN:0032-3888    

DOI:10.1002/pen.760211211

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY