摘要:

AbstractTo obtain further details of the unusual behavior of the “hard elastic,” “springy” form of polypropylene (SPP), various loading conditions were studied with an Instron model 1130. Specifically, the variation of the elongation at rupture with change in gauge length and strain rate has been determined. The nature and degree of the specimen hysteresis resulting from various loading cycles have been characterized. The ability of this material to recover from large extensions customarily expected to be permanent deformation has been identified and the time dependency of this recovery has been determined for strain levels of 10, 25, 50, and 100 percent of the original sample length. The effects of submitting the material to conditioning treatments, e.g., immersing in saline solutions of various electrolyte concentrations and autoclaving for 30 min at 250°F and 15 psig have been studied. Characterization of the stress relaxation behavior of the polymer has been made. Fatigue behavior has been identified utilizing a novel testing apparatus which permits load‐cycling of the fiber. Rheovibron work has facilitated calculation of the activation energy of the second order relaxation of SPP from tan δ vs temperature data. Stoll abrasion testing results on SPP tubular knit fabric and multifilament yarn have been compared to normal polypropylene

ISSN:0032-3888    

DOI:10.1002/pen.760150902

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe dynamic mechanical properties of a series of thermoplastic urethane elastomers have been studied as a function of molecular composition and temperature. Polymers based on polycaprolactone diol, an isomeric mixture of tolylene diisocyanate and hydrogenated Bisphenol‐A as the chain extender were prepared at various relative concentrations of hard and soft segments. The glass transition temperatures of these polymers progressively shifted to higher temperatures as the relative hard segment content was increased. This variation was accurately described by the Fox relationship for amorphous copolymers. These results can be interpreted in terms of the relative degree of segregation between the segment of the block copolymer

ISSN:0032-3888    

DOI:10.1002/pen.760150903

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractElastomeric bearings which consist of cylindrical rubber layers bonded on their inner and outer curved surfaces to metal cylinders are investigated theoretically and experimentally. Emphasis is placed on two asymmetic loading modes, radial loading and bending or tilting moments. An approximate theoretical treatment based on linear elastic behavior is proposed. Experimental spring constants are compared to the theoretical predictions for thin elastomer layers of various lengths. It was found that for highly confined layers, the theoretical spring constants must be modified to obtain agreement with experimental results. The importance of elastomer bulk deformation, shrinkage stresses from elastomer cure, and tension‐compression stress‐strain behavior is also evalua

ISSN:0032-3888    

DOI:10.1002/pen.760150904

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractExperimental studies of structure development in melt spinning of polyethylene and polypropylene fibers are described. Emphasis is given to the influence of applied stresses on the rates of crystallization and on the development of crystalline morphology. The relationship of fiber morphology to mechanical properties, especially “hard elastic fibers” is considered. The relevance of such studies to other polymer processing operations such as film extrusion is discus

ISSN:0032-3888    

DOI:10.1002/pen.760150905

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractReinforcement can improve the modulus, heat distortion temperature and thermal expansion coefficient of rubber modified polypropylene. These improvements canbe obtained with a minimum sacrifice in resin ductility and impact toughness. Our studies have shown that reinforcement with small discontinuous fibers can provide a material with a good balance of stiffness and impact strength. The combination of small potassium titanate fiber reinforcement, polypropylene homopolymer and an impact modifier can produce a material with a tensile modulus of 470,000 psi, a notched Izod impact strength of 4.6 ft‐lb/in. and a Gardner imact strength of 320 in‐lb. Glass fiber reinforcement produces similar improvements in stiffness and retains Izod impact strength but drastically reduces Gardner impact strength. Polypropylene resin viscosity has a profound effect on composite impact strength. Transmission electron microscopy showed that a correlation exists between EPDM rubber particle size and impact strength: as rubber particle size is reduced, impact strength is increased. A 5 melt flow rate polypropylene was found to have the viscosity required to adequately shear and disperse the impact modifier. The paper describes an approach to broadening the utility of polypropylene homopolymers. The properties and flow of these materials compare very favorably with medium impact

ISSN:0032-3888    

DOI:10.1002/pen.760150906

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractPrevious studies have evaluated low molecular weight crystalline materials as latent heat sinks for passive thermal protection systems. This study evaluated crystalline polymers as heat storage materials. Differential scanning calorimetry and Instron thermomechanical analysis are applied in dynamic studies of cumulative histories of melting and recrystallization. Commercially available crystalline polymers with melting temperaturesTm≥ 100°C can provide fully reversible heats of fusion ΔHm≥ 35 cal/gm under programmed heating‐cooling cycles. A linear polyethylene (Marlex 6050) is modified by radiation crosslinking to retain shape stability aboveTmwith‐out loss of heat storage capability. The essentially zero vapor pressure and inherent shape stability of crosslinked crystalline polymers may provide unique advantages as uncontained, non‐expendable, heat storag

ISSN:0032-3888    

DOI:10.1002/pen.760150907

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA ‘tubeless syphon’ was used as an elongational viscometer for the purpose of measuring elongational viscosities of glass bead suspensions in dilute polymer solutions. It was found that while the shear viscosities increased, the elongational viscosities decreased very sharply with increasing bead concentration. The conclusions from the present data are then compared with the observed changes in the elastic properties of two phase molten polymer systems. A double shift procedure has been successfully adopted to correlate the experimental d

ISSN:0032-3888    

DOI:10.1002/pen.760150908

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe mixing of polymers is an important subject which has received considerable and recent attention. This study shows that residence time distribution curves give information on the distribution of material along the primary flow direction, but do not quantify in polymer flow systems. Several polymer processing systems have been analyzed and the degree of mixing has been related to strain in each of these systems. Strain correlates directly with transverse mixing, which is the most important aspect of polymer mixing. Mixer design is shown to influence the amount of strain needed to achieve a specified degree of mixedness.

ISSN:0032-3888    

DOI:10.1002/pen.760150909

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractOne dimensional transient heat conduction analysis of reactive, unfilled polyesters and epoxies shows that care must be taken during curing to minimize large temperature excursions due to internal heat generation. Isothermal heat generation rates have been shown to underestimate the non‐isothermal values by more than an order of magnitud

ISSN:0032-3888    

DOI:10.1002/pen.760150910

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760150901

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY