摘要:

AbstractThe presence of additives influences the state of segregation of filler particles in the polymer matrix which in turn controls the electrical and mechanical properties of poly(vinyl chloride)‐copper composites. The liquid plasticizer seems to form a coating on the filler surface which introduces quasirandomness in the segregated network. In accordance with the mathematical model proposed earlier, the strength properties were found to be proportional todm−½wheredmis the mean free path between the filler particles. Calculations ofdmwere based on two different models, one for segregated network (unplasticized and low plasticized composites) and the other for quasi‐random distribution of filler particles (plasticized composites). Extruded samples in general show more randomness in the filler distribution than the compression molded s

ISSN:0032-3888    

DOI:10.1002/pen.760190802

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractScanning electron microscopy (SEM) studies of fracture surfaces of poly(vinyl chloride)—copper composites at various metal loadings and different processing conditions reveal characteristic features. In general, metallic fillers introduce brittleness, while plasticizers increase the ductility of the composites. Results of the fracture studies have been correlated with the properties of the composites reported earlie

ISSN:0032-3888    

DOI:10.1002/pen.760190803

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractFiber reinforced composite structures have gained a significant position as materials of construction for the aerospace industry. It thus follows that large expenditures of funds and human lives are dependent on the reliability of these products. An important step in gaining confidence in a part is knowing that the starting prepreg has the same chemical formulation in each lot of material and that each lot has been processed in the same manner. This can be accomplished by physiochemical characterization. The techniques described herein were developed for 177°C (350°F) epoxy matrix systems. However, the methods form a basis for developing similar procedures for other types of matrice

ISSN:0032-3888    

DOI:10.1002/pen.760190804

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA commercial heat‐resistant polystyrene (M̄n= 7 × 104, M̄w= 3 × 105), containing 9 percent cis‐1, 4‐polybutadiene, was extruded either repeatedly (2 to 8 times) at 220°C, or else only once at a higher temperature (up to 290°C). Neither treatment significantly altered the melt rheology at 220°C (pseudoplastic, withn= 0.39), or the tensile modulus (1.5 GPa) and yield stress (20 MPa), or the material's rubber content, determined by both infrared spectrophotonietry and Wijs iodometry. Other properties, only slightly affected by recycling at 220°C, were changed after one extrusion at 290°C: elongation at tensile failure was reduced by 57 percent; in impact testing the strength was 29 percent less, and the mode of fracture (revealed by scanning electron microscopy of the surfaces) became brittle instead of ductile; the rubber particles seen in the transmission electron microscope had agglomerated and lost sphericity; and the ratio of weight‐to‐number‐average molecular weight of the polystyrene component, calculated from gel permeation chromatograms, increased by 93 percent. Mechanical spectra (Rheovibron), from −120 to + 120°C at 110 Hz, changed gradually with increasingly harsh treatment of the material, a peak emerging at ∼50°C due to a beta relaxation of the polystyrene. Thus, good properties were retained after normal processing, but were lost after shearing at too high a temperature, probably because of destruction of entanglements and of the bonds betw

ISSN:0032-3888    

DOI:10.1002/pen.760190805

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe ultimate properties of injection‐molded thermoplastics articles are controlled to a large extent by flow and heat transfer phenomena that take place during the injection‐molding process. In fact, the thermo‐mechanical history of the melt during the molding process leads to a non‐uniform distribution of many of the critical properties of the molding. Birefringence has been employed as an indirect measure of the distribution of frozen stresses or strains in amorphous polymers. The present study employs birefringence to study the development of frozen stresses in injection‐molded polystyrene. In general, orientation in the flow direction is much greater than the orientation in the transverse direction of the moldings. In the vicinity, of the gate, where mold filling is characterized by spreading radial flow of the melt, the hoop stresses (planar deformation) at the melt front give rise to high orientation in the transverse direction. It appears that relaxation phenomena are not very important during the filling stage; however, they become more, important in the packing and pressure holding stages. With the aid of the appropriate rheo‐optical relationship, it is shown that the distribution of frozen‐in orientation in injection‐molded polystyrene may be estimated on the basis of data relating to pressure variations during th

ISSN:0032-3888    

DOI:10.1002/pen.760190806

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe ductile‐brittle transitions of nylon‐66 compositions were studied by Izod and falling weight tests. Samples included unmodified and impact modified compositions. Brittle breaks did not occur in the toughest resin with changes in rate of loading, notch radius, thickness, or distance and orientation to the gate. A fracture mechanism is propo

ISSN:0032-3888    

DOI:10.1002/pen.760190807

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractIn order to clarify the crystal structure and intermolecular cohesion forces of ethylene‐vinyl alcohol copolymers (EVA), the elastic modulus (Et) of EVA copolymers was measured. We proposed that EVA copolymers are crystallizable over the entire range of copolymer composition and can produce, an isomorphous crystallite. On the basis of these crystal structures, the value ofEtwas expected to be dependent on the copolymer composition.Etvalues are indeed closely dependent on composition and decrease with decreasing VA segment. From the anisotropy ofEtfor (100) and (002) planes, which means the anisotropy of the intermolecular interaction, the direction of hydrogen bonding seems to be in thea‐axis direct

ISSN:0032-3888    

DOI:10.1002/pen.760190808

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe basic relationships are presented for predicting the creep and stress relaxation as a function of physical aging, loading time, and temperature of amorphous polymers processed under such conditions that their thermal treatment amounts to a quench from the melt to the glassy state. A nomogram construction, based on these relations, is proposed and developed for a particular polymer, namely an extrusion type acrylonitrile‐butadiene‐styrene (ABS), RONFALIN EST. The applicability of the procedure is restricted to theisothermalviscoelastic behavior atlowstresses and strains of unplasticisedamorphousplastic materialsquenchedfrom the melt to the glassy st

ISSN:0032-3888    

DOI:10.1002/pen.760190809

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA detailed study was made of the thermal behavior of poly(vinyl chloride) (PVC) homopolymers, whose chain length and structure were independently manipulated. Normal PVC polymerizations are made at temperatures, the selection of which determines the polymer chain length. In the case of PVC, this choice of temperature also determines its syndiotacticity, and so, its glass transition temperature, and in many ways, its processibility. The ability to understand how to control chain structure and length in PVC is critical in designing polymers for selected specific end use conditions. The thermal spectrum is known to be one measure of how polymers will perform. This study reveals how such controlled chain length/structure PVCs are characterized by thermal methods, and how one can separate individually the effects of syndiotacticity and molecular weight on thermal properties of poly(vinyl chloride).

ISSN:0032-3888    

DOI:10.1002/pen.760190810

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA number of techniques have been developed in the past for the prediction of the dependence of the creep rupture life of polyethylene pipe on applied stress and temperature. It is now proposed that, using a modified form of the activated rate procss equation in which the activation volume varies predictably with temperature, a generalized equation may be derived which describes the “brittle” creep rupture curve over a range of temperatures, and also allows the use of a Larson‐Miller type equation. Since the known “ductile” creep rupture curve at 20°C can be extrapolated from measurements carried out over a short period at room temperature in the laboratory, the intersection point between the extrapolated “ductile” curve and the calculated “brittle” curve can easily be calculated. If the proposed method is applied to creep rupture data obtained from Hoechst AG (GM5010, HDPE pipe) as an example, a transition at about 11

ISSN:0032-3888    

DOI:10.1002/pen.760190811

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY