摘要:

AbstractThe capillary flow instability resulting in extrudate distortion has been studied for ethylene polymer melts using a molecular structure approach. It is found that the instability initiates at a critical value of elastic strain energy independent of (average) molecular weight for linear polyethylene. Once the flow breaks down, a slip interface within the melt is formed near the capillary wall, causing an abrupt increase in volumetric throughput. The velocity gradient within the melt remains continuous through the instability, however. Low molecular weight species present in the molecular weight distribution of linear polyethylene tend to suppress slip. Blends of linear and branched polyethylene exhibit instability behavior characteristic of both components throughout the entire range of composition. Results are discussed in terms of specific molecular mechanisms.

ISSN:0032-3888    

DOI:10.1002/pen.760100402

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractDynamic mill stability tests of PVC powder blends at the equiviscous temperatures were correlated with the clarity and color obtained in extrusion and blow molding of bottles. Copolymers of vinyl chloride with alkyl vinyl ether and propylene in a calcium‐zinc stabilizer, impact modified formulation had better processability than a homopolymer and produced bottles having lower values of absorbance and yellowness index. Product imperfections which were evident in blow molding of dry blends, but not during milling or capillary rheometer extrusion, were found to be related to the particle size distribution and volatile content of the resi

ISSN:0032-3888    

DOI:10.1002/pen.760100403

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThis paper illustrates a numerical simulation of polymer flow as applied to the injection molding fill process. The simulation model considers heat conduction and viscous heat generation along with the temperature dependence of the flow parameters to predict fill lengths and fill times of thin constant crossection cavities. This simulation is designed for molding situations where fill is difficult, such as thin cavity sections, long flow length requirements, or difficult‐to‐process materials. The simulation sensitivity is explored by performing experimental molding trials with two different cavity thicknesses. The thinner cavity illustrated a short shot in all cases with the thick cavity completely filling. The simulation accurately distinguishes between the short shot and fill conditions, although significant error is noted for the length prediction of the short shot and the time‐to‐fill of the full shot co

ISSN:0032-3888    

DOI:10.1002/pen.760100404

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA new method of treating torque rheometer test data has been developed. First, it involves converting the torque values measured over a range of temperatures to torques corresponding to a constant reference temperature. Then the log of the calculated torques is plotted against time. The method has been applied to several polypropylene grades, and the effects of numerous test variables have been explored. Correlations have been developed between torque rheometer data and fundamental polymer properties of viscosity and molecular weight. The method should also be applicable to polymers other than polypropylene.

ISSN:0032-3888    

DOI:10.1002/pen.760100405

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe solubility parameter of polyisobutylene has been determined from intrinsic viscosity measurements in a single solvent as a function of temperature. The change in solubility parameter of the solvent as a function of temperature was calculated form the equation\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{d{\rm}ln \delta s}}{{d{\rm}ln Vs}} = - \frac{{n + 1}}{2} $\end{document}whereVs, the molal volume, changes with temperature. The vlaue for the solubility parameter thus obtained compares well with values reported in the literature for intrinsic viscosity measurements in a series of solvents. Similar measurements were made with an ethylenepropylene copolymer. The solubility parameter of 87 mole % C2ethylene‐propylene copolymer was determined to be 8.1‐8.6 in either toluene or methylcyclohex

ISSN:0032-3888    

DOI:10.1002/pen.760100406

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe thermal stability of elastomers containing siloxane linkages has been compared using the technique of chemical stress relaxation in an inert environement. Enhancement of the already high stability of the basic poly (dimethyl siloxane) silicone rubber by the substitution of hetero groups in and on the main chain was proved, with the exception of the pendent trifluoroporopyl group. Particulary dramatic was the effect of the mcarborane moiety in the SiB‐2 elastomers which elevated the stability of the siloxane chain by more than 100°C relative to silicone rubb

ISSN:0032-3888    

DOI:10.1002/pen.760100407

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractWhen plastics are used for outdoor applications, they often deteriorate fairly rapidly. Theoretical explanation is based upon absorption of ultraviolet energy, raising some bonds to an energy level which exceeds their stability, and thus initiating their breakdown, usually involving atmospheric oxidation and sometimes hydrolysis as well. This theory is satisfactory for many polymers, but does not explain the instability of some polymers which are transparent to ultraviolet, nor the stability of some polymers which contain ultraviolet‐absorbing and/or unstable groups. Plastics are often stabiliized by addition of ultraviolet reflectors, absorbers, or deactivators, increasing stability sufficiently for outdoor use; theoretical explanation of their protective action is satisfactory when they work, but does not explain their specificity or their failure

ISSN:0032-3888    

DOI:10.1002/pen.760100408

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA phenomenological treatment has been developed for correlations between melt flow properties of high‐density polyethylenes and the processability of bottles. Defining two parameters for the flow properties, it was found experimentally that linear relationships hold satisfactorily between these flow parameters for the raw materials and those of corresponding extrudates. Several kinds of defects in high‐density polyethylene bottles can be represented in terms of the flow parameters. These parameters may provide useful measures in predicting good appearance of bottles blow‐molded with high‐density polye

ISSN:0032-3888    

DOI:10.1002/pen.760100409

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe results of a study to determine the biological stability of clear, colorless, biocide‐treated PVC film are presented. With the exception of a resistant control, all the PVC film samples tested contained a plasticizer susceptible to biological deterioration. Biocide‐treated and control PVC film samples were subjected to biological attack in soil burial. Portions of each sample were exposed to leaching and to weathering in a weatherometer followed by soil burial to test the stability of each biocide to loss by water and weathering exposure. Of the 32 biocide preparations tested only 2, N‐(trichloromethylthio) phthalimide and copper 8‐quinolinolate, a known effective reference compound, were found to provide good protection for treated film in direct soil burial and in soil burial following leaching and weatherometer exposure. Natural weathering outdoors confirmed the results found with weatherometer exposed samples. The N‐(trichloromethylthio) phthalimide was less effective than the reference compound in suppressing surface growth. In addition, N‐(trichloromethylthio) phthalimide may not be compatible with all PVC f

ISSN:0032-3888    

DOI:10.1002/pen.760100410

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA new quantitative thermal analysis technique was attempted on ABS and Noryl‐type polyblends. A particular component within a polyblend was identified by its glass transition temperature and the amount of the component was determined from the increase in specific heat at the glass transition temperature.Two commercial Noryl resins were determined to be blends of high impact polystyrene and polyphenylene oxide in 47‐47 and 69‐17 proportions by weight, respectively. Polystyrene appears to be cosoluble with polyphenylene oxide without the formation of any complex. The PS‐PPO polyblends yield single sharp glass transitions which are a function of concen

ISSN:0032-3888    

DOI:10.1002/pen.760100411

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY