摘要:

AbstractProper drying techniques prior to molding can eliminate the overall effects of moisture on the physicochemical properties of polycarbonate. Problems associated with moisture in polycarbonate during molding are described in detail. Moisture absorption is very rapid with the maximum allowable moisture content of 0.03 percent reached within 30 minutes at 49 percent RH and 75°F. Molding with excess moisture content causes a chemical and physical degradation resulting in reduction in tensile impact strength, tensile elongation, ultimate tensile strength, proportional limit and molecular weight. New and existing techniques and procedures for degradation detection were investigated, such as intrinsic viscosity, infrared spectrometry, and thermal methods of analysis. Gel permeation chromatography (GPC) proved the most satisfactory. GPC provided information on the average molecular weight and polydispersity

ISSN:0032-3888    

DOI:10.1002/pen.760141202

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractSeveral types of amorphous polymers have been cold‐rolled to various thickness reductions and the notched Izod impact behavior has then been studied. It has been determined that whereas some polymers exhibit large increases in impact strength with modest reductions in thickness other polymers only exhibit small increases in impact strength. For example, PVC, ABS, poly (phenylene oxide), and polysulfones show large increases in impact strength whereas rubber‐toughened acrylics show only a small increase in impact stren

ISSN:0032-3888    

DOI:10.1002/pen.760141203

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractTernary phase diagram for several polybutene‐1 and polystyrene resins in carbon tetrachloride have been determined. These show:Almost the entire phase diagram is a two‐phase region.The composition of each phase is mainly of one polymer type.Increasing the molecular weight of either polymer diminishes compatibility.To our knowledge, this is the first example of phase separation in common solvent polymer solutions that involves a poly α‐olefin. Viscosity and surface tension data on the equilibrium phases indicate the phases have the same surface tensions but far different viscosities. The upper phase is mainly polybutene‐1 and is much more viscous than the lower phase which is mainly polystyrene. Slight agitation of the phases gives an “emulsion” that may be cast into a polymer film. The film has a continuous phase of Form III polybutene‐1 and a dispersed phase of polystyrene. The polystyrene may be extracted from the film by immersion in methyl ethyl ketone to give a porous pol

ISSN:0032-3888    

DOI:10.1002/pen.760141204

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of an isopropanol environment on the deformation characteristics of copoly (acrylonitrile‐butadiene‐styrene) (ABS) and poly (vinyl chloride) (PVC) have been investigated. Creep tests were performed in tension and torsion both in air and in isopropanol. It was noted that accelerated rates of creep were encountered during the tensile tests in isopropanol as compared with air but no differences were noted during the torsion tests. An explanation is proposed that the greatly increased creep strains encountered in tension result from diffusion of the fluid into the polymer. The rate of diffusion is controlled by changes in the free volume which occur on application of uniaxial tensile stresses. The existence of the fluid molecules in the polymer matrix reduce its local creep resistance and produce swelling, both of which are manifested as increased creep strains. The fact that no effects were noted during torsion tests (where the free volume remains constant) or when an unstressed specimen was immersed in the fluid indicates that no significant absorption occurs at the equilibrium (unstressed) free vol

ISSN:0032-3888    

DOI:10.1002/pen.760141205

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIn a reciprocating‐screw injection‐molding machine, the screw or plunger forces the plastic into the mold. It remains in the forward position under pressure for a fixed time during which plastic flow into the mold or ‘packing’ takes place. After the timer runs out, the screw moves back while rotating thus releasing the pressure on the plastic in the mold. At this time, if the gate has not frozen, flow of plastic out of the mold or ‘discharge’ takes place. In this study, clear rigid PVC, poly (vinyl chloride), was molded with varying amounts of packing and discharge. Photoelastic stress patterns for parts observed between cross‐polaroids suggested that packing and discharge give rise to high frozen stresses due to molecular orientation in the gate area. Mechanical strength tests on the molded parts show that these high stresses are a source of weakness. Short forward times for the plunger significantly improve the mechanical properties of the parts in the gate area and at the same time have a significant influence on part dimensions, especially in the gate vicinity. Laminations observed at the gate interface can also be reduced by controlling the extent of molecular orientation introduced by packing

ISSN:0032-3888    

DOI:10.1002/pen.760141206

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThis paper reviews a series of high‐melting thermoplastic polyether esters prepared by transesterification from dimethyl terephthalate, polytetramethylene ether glycol (MW 600–2000), and 1,4‐butanediol. The resulting copolyesters exhibit a two‐phase domain structure consisting of amorphous polyether ester soft segments and crystalline tetramethylene terephthalate hard segments. By proper selection of the relative amounts of soft and hard segments, polymers ranging from relatively soft elastomers to impact resistant elastoplastics may be obtained. The preparation, polymer structure as well as the physical and environmental properties of polyether esters are discussed. The combination of good melt flow properties, excellent melt stability, and rapid hardening rates permits the processing of these polymers by a wide variety of methods. The excellent processing characteristics in conjunction with the unusual physical and mechanical properties of segmented polyether esters has led to their wide acc

ISSN:0032-3888    

DOI:10.1002/pen.760141207

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractComputer simulation technology is used to define the problems in scale‐up of extruders from 2.5 to 3.5, 4.5, 6.0, and 8.0 inches in diameter. It is shown that the conventional practice of scaling‐up channel depths by the square root of the diameter ratio does not take full advantage of the potential output capacity of larger extruders and a faster rate of channel depth increase is proposed. It is also shown that inherent limitations resulting from decreasing barrel surface area and increasing flight clearance with increasing screw diameter will always result in a higher discharge temperature from the larger machine at any practical output rate. Frictional heat generation and heat removal requirements increase with increasing diameter, regardless of the scale‐up system used, and these limit the output capability of the larger sizes at low discharge tempera

ISSN:0032-3888    

DOI:10.1002/pen.760141208

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA simple method for predicting the primary normal stress function, θ, from viscosity data is proposed. A relation between θ and the viscosity function, θ, based on the Goddard‐Miller rheological equation of state, is given. An easy‐to‐use generalized chart for estimating θ from θ is presented; in order to use this chart, viscosity data must be available from the zero‐shear‐rate value of the “power law region.” The method was applied to six polymer melts, three polymer solutions, and an aluminum soap solution for which θ had been measured experimentally. Even though θ varied by a factor of 103over the examined range of shear rate, the theory and experiment seldom differed by more than a factor of 2. The generalized chart for θ was combined with Tanner's theory to prepare a graph which may be used to estimate jet swell from viscosity data. Comparison with experimental data of jet swell for 4 polymer melts

ISSN:0032-3888    

DOI:10.1002/pen.760141209

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe Contraves balance rheometer has been used in a study of the gelation and fusion process of three DOP‐based PVC‐plastisols and the results compared with those obtained with the Brabender plastograph. The tensile properties of samples fused at different temperatures have also been determined. The rheometer results relate to the temperature dependence of the viscosity, shear modulus, and loss angle of the plastisols used. The viscosity‐ and modulus‐temperature curves are to some extent reminiscent of the torque‐temperature curves obtained with the plastograph; the fusion temperatures are slightly different. The loss‐angle‐temperature curves measured with the rheometer exhibit sharp maxima in the vicinity of theTg‐point of the base polymer. The shear modulus decreases with time when the temperature is kept constant (above the fusion point). This effect is possibly associated with crystallite melting. The temperature necessary to reach the maximum strength plateau of films fused at various temperatures was found to agree (within 10°C) with the maximum in the modulus‐temperature curves (minimum in loss‐angle‐temperature curves) when the rheometer shear rate was sufficiently low. On the whole, the rheometer allows for better temperature control. Also, the fact that the results are given in terms of viscosity and shear modulus may have some advantage in interpreting ge

ISSN:0032-3888    

DOI:10.1002/pen.760141210

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe spiral mold method (moldability test) was used in a study of phase separation occurring in glass‐containing polyethylene and polyamide melts. Pronounced separation effects were recorded for low density polyethylene containing 25 percent glass spheres with diameters ranging approximately from 50 to 100 μm, the glass concentration at the tip of the spiral exceeding 40 percent by weight. For melts containing smaller spheres or fibers the effect was of the order of a few percent. There was a decrease in glass concentration near the center of the spir

ISSN:0032-3888    

DOI:10.1002/pen.760141211

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY