摘要:

AbstractThe du Pont 980 dynamic mechanical analyzer has been interfaced with a Hewlett‐Packard 9825A calculator. This permits the resonant frequency and loss to be converted automatically into the engineering quantities of modulus, loss modulus, and tan δ presented in both tabular and graphical form as functions of temperature. Productivity is much greater than with previous ways of taking and processing data, and subtle features of the dynamic mechanical spectrum are more easily reveal

ISSN:0032-3888    

DOI:10.1002/pen.760200502

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractFlow crystallization experiments which utilized the Instron rheometer in conjunction with convergent dies were conducted for the purpose of producing high‐modulus poly(ethylene terephthalate) filaments directly from the melt. A temperature gradient was imposed on the lower extremity of the dies in an attempt to control the site of the fluid‐solid phase transformation, and “freeze in” any orientation derived from the elongational flow regime. Comparative studies were made using dies with included angles of 20, 30, and 40°, and extrusion temperatures ranging from 255 to 270°C. Die angle influenced the pressure at which maximum die swell and the onset of extrudate distortion occurred; however, barrel temperature showed little effect on this pressure. The minimum temperature produced by the temperature gradient was the over‐riding factor involved with cessation of flow. In each experiment, the fluid‐solid phase transformation produced by the temperature was always accompanied by extrudate distortion. Thus, only minimal comparative studies of the extrudates could be performed. In view of the above, it appears that utilizing a temperature gradient, by itself, to “freeze in” preferred orientation within the confines of the die presents difficulties. A modification which combines a temperature gradient with external tension and a rapid after‐quench outside the die, now holds appeal for

ISSN:0032-3888    

DOI:10.1002/pen.760200503

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractPolymeric films, chiefly polyethylenes, were subjected to corona‐discharge treatment in a continuous treater at commercial rates in a program covering wide ranges of the main processing factors (2). Electron‐spin‐resonance measurements on freshly treated films found no free radicals. Reactions of the treated surfaces with a free‐radical compound, diphenyl picryl hydrazyl (DPPH) were studied, focusing mainly on the rate effects. The evidence indicates that corona treatment produces fairly stable peroxide structures of the forms RO2R and RO3R on polyethylene surfaces. RO3R reacts rapidly with DPPH alone, while RO2R undergoes a slower reaction after addition of the catalyst, triethylene diamine. DPPH is capable of detecting as few as 1013peroxide groups per square centimeter. Activation energies were 12 kcal/mole for the uncatalyzed reaction and 16 kcal/mole for the amine‐catalyzed reaction. As with the physical effects reported earlier (2), the production of peroxides is most strongly dependent on the energy delivered to the film during treatment. This energy is proportional to the quotient of corona current and web speed, I/S, Regression analysis showed that air‐gap thickness, relative humidity, and number of electrodes used also were significant factors, while dielectric thickness and corona frequency were not. We found that‐γ SP, the polar component of surface energy of the treated film, which is nearly zero for untreated polyethylenes, is exponentially related to the concentrations of both RO2R and RO3R with a correlation coefficient for 92 specimens tested of 0.88. We believe this is the first strong evidence linking treatment factors, at commercial levels of treatment, to chemistry of the treated surface and linking both of those to changes in physical behavio

ISSN:0032-3888    

DOI:10.1002/pen.760200504

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractSlow developed flow in an extruder channel has been set up as a two‐dimensional, variational problem using a helical coordinate system, thus avoiding the usual geometrical simplification. Continuity is enforced by an integral form of constraint, and solutions for isothermal, Newtonian flow are obtained by a finite element method for both shallow and deep, highly curved channels. The performance of the solution procedure as a function of Lagrangian multiplier is discussed. Convergence to correct solutions is demonstrated for the shallow channel case. Deep channel results are compared with analytic predictions, curvature corrected according to Booy. Further testing of deep channel results will be made against experimental dat

ISSN:0032-3888    

DOI:10.1002/pen.760200505

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractData have been obtained on the operation of a deep‐channel single‐screw extruder, pumping a Newtonian liquid under isothermal, developed flow conditions. Flow rate, screw speed, and pressure gradient characteristics were measured, and a tracer particle technique was employed to determine channel velocity profiles. The data were required for the testing and development of a computer model for flow in the extruder, which takes into consideration channel curvature. Results confirm the correctness of the computer solutions previously repor

ISSN:0032-3888    

DOI:10.1002/pen.760200506

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractExperiments are reported concerning the performance of an extrusion crosshead used in the three‐layer covering of high voltage electrical cables. Both extrusion pressure requirements and circumferential distributions of polymer layer thicknesses in the finished cable were measured and compared with the results of a previously published finite element method of melt flow analysis within the crosshead. While agreement on pressure is good, it is necessary to allow for the effects of both gravity and slight misalignments of crosshead components if the thickness distributions are to be correlated satisfactorily. The latter effect emphasizes the need for a high degree of accuracy in crosshead design and manufactur

ISSN:0032-3888    

DOI:10.1002/pen.760200507

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractBlends of polypropylene (PP) and low density polyethylene (LDPE) were prepared by both batch mixing followed by compression molding and extruder compounding followed by injection molding. Compression molded PP‐LDPE blends were found to have very poor toughness, whereas extruded blends, injection molded without weld lines, were quite tough. Injection molded blend specimens with weld lines were found to be weaker and failed at very low elongations at break. A simple adhesion analysis is presented which explains well the weakness at the weld line expected for incompatible blends. Addition of an ethylene‐propylene polymer with residual ethylene crystallinity was found to be a more effective “compatibilizer” for blends deficient in toughness than a related copolymer with less crystallinity. This effect is attributed to the more block‐like character of the former which permits it to play more nearly the interfacial role required of the ideal blend compatibiliz

ISSN:0032-3888    

DOI:10.1002/pen.760200508

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractViscometry, gel permeation chromatography (GPC) and diffusion measurements on three samples of poly(vinylpyrrolidone) (PVP) were made. The diffusion measurements were carried out by means of a Stokes cell. An equation with five parameters was derived, linking the difference in PVP amount between the two compartments of the cell to the time of the experiment: three parameters are related to the diffusional behavior of the macromolecules and the other two define the molecular weight distribution (the Tung expression has been chosen). A least‐squares procedure allowed us to obtain the five parameters and the calculated weight average molecular weights agree with the ones evaluated by viscometry and GPC. The ratioMw/Mn(heterogeneity of the polymer) calculated from the parameterzof the Tung expression is very different from the one obtained from GP

ISSN:0032-3888    

DOI:10.1002/pen.760200509

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe effect of recycling on the properties of injection molded polycarbonate was investigated. One unreinforced and two glass‐reinforced grades were studied. Fiber degradation was distinguished from molecular scission by spiral flow measurements and molecular weight analysis. During the first cycles the average fiber length was significantly reduced, but at later stages it approached an equilibrium. The number of scission per original polymer molecule increased linearly with the number of recycles for all systems studied, but the degradation reaction did not follow random scission kinetics. The glass reinforced grades exhibited degradation rates which were at least twice as high as that of an unreinforced polymer. This discrepancy was most probably the result of a more extensive viscous heating in the glass‐reinforced systems. The decrease in molecular weight as well as in fiber length greatly affected the impact strength of the material. The effect of processing temperature on polymer degradation during recycling was evaluated. The fraction of virgin material that has to be added to the regrind to maintain a certain property level was determined. On a 90 percent property level, an icrease in melt temperature by 1°C corresponded to an increase of 1 percent in the required amount of virgin material. Aging tests indicated that there was no significant difference in degradation rate between recycled and virgin material, although the former certainly exhibited lower absolute values of the measured property (impact stren

ISSN:0032-3888    

DOI:10.1002/pen.760200510

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760200501

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY