摘要:

AbstractThe biochemistry and stereochemistry of proteins are reviewed and related to molecular structure and specifically to the properties governing fiber formation. The conformation of amino acids, polypeptides and proteins are discussed. The amino acid composition of protein is considered in relation to structure, chain length and molecular weight. General descriptions are also given for typical synthetic polypeptides as well as for non‐fibrous natural proteins used in fiber manufacture. Mechanisms and modes are presented for fiber formation including a discussion of molecular criteria involving intermolecular cohesive and crystalline configurational forces which are involved in the fiber forming process. These effects are related to treatments and processes, including thermal, mechanical and chemical modifications, which can be applied to protein for the purpose of forming fiber

ISSN:0032-3888    

DOI:10.1002/pen.760140202

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe electret potentials developed by reverse osmosis electret membranes help control the undesirable deposition of charged colloidal particles on the membrane surfaces during membrane desalination. These antifouling electret membranes should help prevent the costly flux declines normally associated with deposition of colloidal iron oxides on the reverse osmosis membrane surfaces.Homocharge and heterocharge behavior of cellulose acetate membrane electrets have been studied. Asymmetric reverse osmosis membranes and dense membrane films were studied. The homocharge and heterocharge of cellulose acetate reverse osmosis electret membranes have been explained.

ISSN:0032-3888    

DOI:10.1002/pen.760140203

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe melt flow of a plastic as measured by the standard method (ASTM D‐1238) is at a high enough stress so that the flow is non‐Newtonian. If the die in the plastometer is replaced by a nonstandard, tapered die of large orifice, a lower stress can be used and the flows are shown to be comparable to Newtonian viscosities measured in a cone and plate rheometer. Under these conditions the plastometer can be used as a sensitive measure of the melt stability of a plas

ISSN:0032-3888    

DOI:10.1002/pen.760140204

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA mathematical representation of the plasticating process in a reciprocating‐screw injection‐molding machine has been formulated as a design tool for simulating the effect of processing parameters on the melting performance, the melt temperature, and the pressure profile. Comparisons with experimental data on low density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC) under a wide variety of processing conditions are descri

ISSN:0032-3888    

DOI:10.1002/pen.760140205

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical model for the simulation of dynamic operation of a plasticating extruder is proposed. The model can be recommended as a tool to study various dynamic situations of interest in the operation of an extruder. Several responses to changes in operating conditions are discussed. They indicate the occurrence of transient maximas and occasional oscillations. The controlling of flow rate by adjusting a valve at the die seems to cause temporary local high peaks in pressure, whereas its control through screw speed seems to be satisfactory.

ISSN:0032-3888    

DOI:10.1002/pen.760140206

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe porosity of poly (vinyl chloride) (PVC) resin particles produced in bulk polymerization is sensitive to polymerization conditions. Using scanning electron microscopy, 60μ spherical beads of PVC are shown to be composed of loosely packed 1μ spherical subparticles. This complex morphology is characterized by a variability in surface area. The surface area of bulk PVC materials can be measured by a chromatographic technique. The elution time of n‐octane as a probe molecule on PVC packed columns is simply related to PVC surface area. At approximately constant particle size (measured by Coulter counter and optical microscopy), surface areas measured by argon adsorption are correlated to chromatographic elution times. The bulk density, plastisol viscosity and pore volume (from mercury penetration porosimetry) are determined and related to specific surface a

ISSN:0032-3888    

DOI:10.1002/pen.760140207

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA rheological analysis of a wire‐coating die is presented. The rheological forces which might play a role in the stability of the wire are estimated. In particular, consideration is given to lateral forces related to the secondary normal stress function acting on the wire which is in an eccentric position, and the hydrodynamic force related to the viscosity function acting on the wire which moves at an angle to the die axis. For the former a simple, yet general, expression was derived by solving the flow problem (without axial pressure gradient) with the Ericksen equation in bipolar coordinates. Results indicate that normal stresses stabilize the wire, i.e., tend to restore it to the central location, provided the secondary normal stress function is negative. The hydrodynamic effect tends to reduce the angle between wire and die axes, thus drawing attention to the need of perfect mechanical centering of the guider tip, since in this case this effect also reduces eccentricity. The need is stressed for further work, in particular, experimental measurement of the secondary normal stress functio

ISSN:0032-3888    

DOI:10.1002/pen.760140208

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractCapillary rheometry of four butadiene‐acrylonitrile copolymer raw elastomers was performed at 125°C over a wide shear rate range. The data were corrected for the effect of pressure on viscosity, for pressure loss in the barrel and at the capillary entrance, for the non‐Newtonian velocity profile (Rabinowitsch correction) and for the temperature rise at high shear rates (shear heating). The corrected results were compared to the tensile stress strain data obtained at comparable strain rates. The agreement between the capillary flow data and the tensile stress strain data was quite good, however, some slight systematic differences were noted. The difference was interpreted as the consequence of slipping of materials at the capillary wall. Die swell values were measured and presented as functions of shear rate and capillary length. Extrudate distortions are descr

ISSN:0032-3888    

DOI:10.1002/pen.760140209

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractLow profile polyesters and sheet molding compounds, SMC, are two of many resin‐glass composites that have been commercialized in the past few years. They have evolved through application of earlier technologies and have opened up possibilities for fiber‐reinforced plastics. Because of rapid growth, insufficient time has been spent documenting the technical aspects of making SMC. Techniques are thus described that we have used to characterize the rheological properties of the resin mix during its transition from liquid‐like (viscous) behavior of the initial formulation through the solid‐like (elastic) behavior of the result

ISSN:0032-3888    

DOI:10.1002/pen.760140210

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe solubility parameters and molar volumes of substances can be used, in conjunction with suitable theory, to provide estimates of the thermodynamic properties of solutions; the solubility characteristics of polymer‐solvent systems and the estimation of the equilibrium uptake of liquids by polymers are examples of the type of practical problems that are amenable to treatment.For low molecular weight liquids, the solubility parameter, δ, is conveniently calculated using the expression δ = (ΔEv/V)½, where ΔEvis the energy of vaporization at a given temperature andVis the corresponding molar volume which is calculated from the known values of molecular weight and density.For high molecular weight polymers, the volatility is much too low for ΔEvto be obtained directly and hence recourse must be made to indirect methods for estimating δ for these materials. One such widely used method is based on Small's additive group “molar‐attraction constants” which when summed allow the estimation of δ from a knowledge of the structural formula of the material; however, the density must still be determined experimentally.The proposed method of estimating δ, also based on group additive constants is believed to be superior to Small's method for two reasons: (1) the contribution of a much larger number of functional groups have been evaluated, and (2) the method requires only a knowledge of the structural formula

ISSN:0032-3888    

DOI:10.1002/pen.760140211

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY