摘要:

AbstractProblems associated with single‐lap shear testing of a structural epoxy adhesive are discussed relative to analyses of the epoxy by infrared spectroscopy, gel permeation chromatography, scanning electron microscopy and other instrumental methods. The value of analytical techniques for assessing the adhesive's cure are shown, including a peculiar correlation of lap shear bond strength with the adhesive's initial uncured state as defined by infrared spectroscopy and gel permeation chromatography. This resulted in the development of definitive batch‐to‐batch adhesive quality control methods and specifications involving the water content, curing agent, and oxirane concentrations of the uncured s

ISSN:0032-3888    

DOI:10.1002/pen.760140902

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractParticulate‐filled thermosetting composites are widely used, yet little systematic work has been done on their long‐term strength characteristics. In this study short‐term tensile, flexural, and impact tests as well as tensile creep‐rupture tests were made for unfilled and filled epoxy to clarify the effects of filler size, filler content, and temperature. Fillers used were silica, alumina particles, and glass beads. Test temperatures were varied from 25 to 110°C. As a result of short‐term testing, it was found that the Petch relation held between strength and filler size if brittle fracture occurred, while a strength and filler size if brittle fracture occurred, while a strengthening effect existed when ductile fracture occurred. On creeprupture testing, a strengthening is observed with filler size and content for silica and glass beads. The Arrhenius plot of rupture time for various filler sizes and contents converges to a characteristic point corresponding to the glass transition temperature of the material. Using this relation, a modified Larson‐Miller master rupture curve is proposed which can predict the long‐term strength of particulate‐filled thermosetting composites as functions of rupture time, temperature, filler s

ISSN:0032-3888    

DOI:10.1002/pen.760140903

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractStrain recovery of polyester and nylon 66 monofilaments, following stress relaxation at constant strain, has been measured under two types of temperature history. In the first (experiments here called type A), the monofilament, extended at an elevated temperature, was held at constant strain at that temperature, and then air‐quenched to room temperature while still under stress. The stress was later removed with the fiber at ambient temperature, and the recovery from strain determined. In the second (experiments of type B), the monofilament was also extended at an elevated temperature, but it was then allowed to recover, under zero load, at the same temperature,priorto quenching. A cylindrical heater is described which surrounded the fiber specimen and which could be removed suddenly to permit rapid air quenching of the specimen. Recovery was characterized by the percent of applied strain which was recovered 100 sec after load removal. The percent recovery, in type A experiments, decreased to low values with increasing stretch temperature. Recovery in type B experiments, however, was markedly different, and showed a minimum value at stretch temperatures in the vicinity of the glass transition. At higher temperatures, recovery was high, but it decreased rapidly asTMwas approached due to the onset of viscous flow. There was thus a discontinuity in recovery behavior as the time of quenching increased through the time of unloading (transition between type A and type B conditions). The results were interpreted to show that the achievement of good heat setting (poor recovery) is critically dependent on the temperature of the fiber during both stretching and recovery period

ISSN:0032-3888    

DOI:10.1002/pen.760140904

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractDetailed studies have been carried out on the anisotropy of creep and creep rupture behavior of thermoplastics oriented by the imposition of a large permanent deformation. This deformation is usually such as to produce simple fiber symmetry within the specimen. Experimental techniques have been devised for the accurate measurement of all three principal strains during tensile creep on small samples which are cut from the oriented specimens at various angles to the symmetry axis. In this way a full characterization of the creep behavior up to strains of 5 percent has been obtained at room temperature.Results are presented for work on rigid poly (vinyl chloride), poly(methyl methacrylate), and low density polyethylene. The results are discussed in terms of the time dependence and nonlinearity of the anisotropy. Creep rupture results on similar specimens are also presented and discussed. Anisotropy due to orientation is shown to be important in determining engineering properties and in understanding structure‐properties relationship

ISSN:0032-3888    

DOI:10.1002/pen.760140905

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe morphology of isotactic polypropylene in molded plaques containing a knit line is described in detail. The effects of mold temperature and flow on the size and orientation of spherulitic and transcrystalline regions are discussed. Deformation at the weld line under uniaxial tensile stress is analyzed by optical microscopy.

ISSN:0032-3888    

DOI:10.1002/pen.760140906

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractDuring extrusion the main deformation and orientation of macromolecules is achieved by the flow component with longitudinal gradient. The orientation increases drastically if some solidification occurs during flow, yielding row‐nucleated cylindrites and even fully oriented hard elastomers. In all cases the basic elements are stacks of very thin (∼100Å) folded‐chain lamellae connected by very few tie molecules. The plastic deformation of the solid transforms the original lamellar material into the extremely well oriented fibrous structure with high anisotropy of physical properties. The basic element are the highly aligned, very long and thin microfibrils bundled into fibrils. The axial strength of microfibrils is caused by the great many taut tie molecules connecting as almost crystalline bridges the crystalline blocks across the interposed amorphous layers. In plastic deformation of fibrous material the fibrils are sheared and longitudinally displaced. The latter mode is responsible for almost all the observed elongation. It smooths the structural defects on the surface of fibrils caused by the ends of microfibrils and thus produces a better lateral fit of fibrils resulting in rapidly increasing resistance to plastic deformation. The former mode extends the interfibrillar tie molecules and hence drastically increases their fraction per amorphous

ISSN:0032-3888    

DOI:10.1002/pen.760140907

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe mechanical properties of a series of thermoplastics reinforced with unidirectionally oriented short fibers are reported. Both organic and inorganic fiber reinforcements were used in fiber volume fractions of 0.10 to 0.50. A number of these composites were found to have excellent strength and stiffness properties combined with good toughness and low density. The dependence of composite properties on the properties of the constituent materials is discussed. Fiber efficiency factors for strength and modulus are presented and models for predicting composite mechanical behavior are reviewed.

ISSN:0032-3888    

DOI:10.1002/pen.760140908

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractSolid state processing of polyethylene (SS60‐050) by hydrostatic extrusion is investigated. Measurements are also reported for the tensile properties of polyethylene 60–050 under superposed hydrostatic pressure. With the latter data an estimate is made of the pressure required for extrusion of polyethylene in the absence of losses due to friction and redundant work. The limiting conditions for successful extrusion are discus

ISSN:0032-3888    

DOI:10.1002/pen.760140909

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractTwo component topologically‐interpenetrating polymer networks were made of the SIN type (simultaneous interpenetrating network) composed of two polyurethanes (a polyether‐based and a polyester‐based) in combination with an epoxy resin, a polyacrylate and two unsaturated polyesters. The linear polymers and/or prepolymers were combined in solution and in bulk together with the necessary crosslinking agents and catalysts. Films were cast and chains extended and crosslinkedin situ. All of the IPN's exhibited one glass transition (Tg) intermediate in temperature to theTg's of the component networks, and as sharp as theTg's of the components. This suggests that phase separation may not occur and thus some chain entanglement (interpenetration) of the two networks is involved. The observedTg's are always several degrees lower than the arithmetic means of the componentTg's. A theory based on interpenetration is developed to account for

ISSN:0032-3888    

DOI:10.1002/pen.760140910

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractProcessing involves complex polymer flow problems, either in the melt or in solution. Rheologists have developed many studies with the aim of correlating polymer structure with flow properties and polymer processing. Most of these studies, however, have had relatively little impact on practical processing because of the difficulty in solving the mathematical equations involved. Recently, a relatively few papers have been published with the aim of bridging the gap between theoretical rheology and technology. The first part of the paper presents an account of works which have dealt with the process of filling a mold cavity. The second part discusses briefly some experimental results which provide a correlation between moldability and rheological properties. By analogy with the terms “electrology” and “electrotechnics,” the term “rheotechnics” is suggested for this new ar

ISSN:0032-3888    

DOI:10.1002/pen.760140911

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY