摘要:

AbstractAn experimental study of the co‐extrusion of polyethylene and TiO2‐filled polyethylene through capillary and rectangular cross‐section dies has been carried out. The influence of viscosity ratio, cross‐section type, die length and duration of flow has been studied. Low viscosity melts will encapsulate high viscosity melts during flow through cylindrical and rectangular dies. Low viscosity unfilled melts can encapsulate higher viscosity filled melts and low vicosity filled melts can encapsulate higher viscosity unfilled melts. However, the rate and extent of encapsulation seems to be greater for the former case. This may be due to differences in the viscosity‐shear stress behavior of the filled and unfilled melts. In rectangular dies, the extent of encapsulation for any pair is greater when the interface is initially perpendicular to the shorter cross‐section dimension. The results are consistent with the idea that encapsulation primarily depends upon the ratio of die length to initial inter

ISSN:0032-3888    

DOI:10.1002/pen.760151202

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractIt is now possible to do molecular weight distribution of polymeric material almost as fast as you can put them in solution. μSYRAGEL® has opened a new era in the determination of molecular weight distribution of polymers. With operational efficiencies of 800 plates/min., one can obtain a molecular weight distribution in 15 mins. Combining three of the newest advances in liquid chromatography—solvent delivery, septumless injection, and μSYRAGEL—now makes it possible to use molecular weight distribution as a quality control tool in polymerization and fabrication. The reproducibility of the molecular weight distribution is now good enough that overlays can be done from the raw data. The chromatograms can be used right off the recorder. The reproducibility of the weight average and number average molecular weight is 2–3

ISSN:0032-3888    

DOI:10.1002/pen.760151203

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractTheoretical calculations based on a mathematical model of cellulose acetate dry spinning were compared with experimental data. Both experiment and theory indicate that the velocity in the spin line becomes essentially constant and equal to the take‐up speed at relatively short distances from the jet. Spin line diameter, however, continues to decrease with increasing axial position. Theory predicts that the filament diameter decreases rapidly at very short distances from the jet, but that the rate of this decrease tends to level off at greater distances. The experimental data exhibit similar trends. In addition, the theoretical and photographically observed spin line die swells are in good agreement. For a typical set of cellulose acetate extrusion conditions, computations show that within relatively short distances from the jet neither the diffusional resistance within the spin line nor the gas side mass transfer resistance in controlling. Both are significant. Calculations also indicate that both the filament and the gas side thermal resistances are importan

ISSN:0032-3888    

DOI:10.1002/pen.760151204

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractStudies have been published relating the mechanical properties of ethylene copolymers with short chain branching structures. Other work has emphasized that crystallites in these copolymer systems participate in superstructures and that stress distribution during mechanical testing depends on the arrangement of these structures, the morphology. While developing structure‐property correlations, morphologies of some random and non‐random olefin copolymers have been examined. Surprising morphological differences were found depending on the length, concentration and degree of randomness of then‐alkyl branch and on vicinal substitution with norbornene derivatives as comonomers. X‐ray diffraction yielded unexpected results which can be explained by a change in the direction of chain folding. Linear side chains randomly introduced into an otherwise high density polyethylene result in a two to three fold increase in the 110:200 x‐ray intensity ratios, a slight reduction in the 110:020 intensity and a 5 to 10 fold decrease in the 200:02 intensities. These results cannot be explained by orientations introduced in sample preparation. There are associated morphological changes. Vincinal substitution with norbornene comonomers has little effect on crystal habit but does change the morphology, tending to shift superstructures from lamellar to fibrillar

ISSN:0032-3888    

DOI:10.1002/pen.760151205

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractSteady‐state fracture techniques were used to investigate the surface fracture patterns and surface fracture energies of poly(methyl methacrylate) at low velocities (10 cm/sec to 10−5cm/sec). Several anomalies were discovered: (1) Small surface cracks, running parallel to the crack front, which were initiated by imperfections; (2) a “zero velocity” transition from the normal surface fracture patterns to a “laminar” pattern; and (3) a subsequent transition from the laminar pattern to a “turbulent” pattern. The velocities at which these anomalous fracture patterns occurred were of the order of 10−4to 10−6cm/sec. The corresponding surface fracture energies were a

ISSN:0032-3888    

DOI:10.1002/pen.760151206

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA brief review of papers dealing with the formation, physical properties, and characterization of foams is given. Since the number of such articles on structural foamsper seis small, an attempt is made to summarize a number of related studies which contain information of general relevance or which may be extended to provide a base for more extensive work in thermoplastic structural foams. Several critical research areas are identified.

ISSN:0032-3888    

DOI:10.1002/pen.760151207

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractTwo models are presented for simulating the injection molding of thermoplastics in thin, rectangular cavities. One is a much simplified bounded‐radial‐flow model that utilizes an existing numerical model for semi‐circular cavities to adjust for the non‐radial flow region bounded by the lateral walls. The other is a two‐dimensional analysis which assumes that both viscosity and temperature change strongly across the narrow gap but vary weakly in the directions of flow. The latter analysis allows application of the potential theory and the determination of streamlines and progressing front shapes. Both models deal with a non‐Newtonian viscosity with temperature variation. Comparisons between experimental and computational result

ISSN:0032-3888    

DOI:10.1002/pen.760151208

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA series of tests was conducted to measure the failure strengths of notched polymethylmethacrylate tensile specimens in air and n‐propanol. Tests were conducted on specimens which had been subjected to creep stresses of various magnitudes and for different times. The resulting data indicate that two opposing factors contribute to the fracture strength in n‐propanol. The presence of fluid during crack propagation increases the nominal fracture failure stress. Diffusion of the fluid into the polymer produces crazing resulting in the provision of a preferential crack path and consequent lowering of the fracture strength. The former mechanism dominates at small pre‐stresses or at short creep times, resulting in an increase in strength in n‐propanol over that in air. However, the latter mechanism is dominant at higher creep stresses and longer creep times with a resulting decrease in strength in n‐propanol compared to th

ISSN:0032-3888    

DOI:10.1002/pen.760151209

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760151201

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY