摘要:

AbstractA novel technique utilizing the dynamic Poisson's ratio to measure the strength of adhesion in fiber‐filled polymeric composites is described. This technique is based on the observation that glass‐filled composites exhibit a large drop in Poisson's ratio as a function of prestrain at very low prestrains. This drop, which indicates additional volume dilation, is interpreted as due to debonding or void formation at the filler‐matrix interface. This interpretation is consistent with the results obtained by using three very different glass surface treatments, with a description of the debonding process using two simplified models and with mechanical properties data. The dynamic Poisson's ratio technique is insensitive to filler orientation and has high resolution, since very small volume changes are reflected as large drops in Poisson's

ISSN:0032-3888    

DOI:10.1002/pen.760181602

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIt is shown that the mechanical properties of polycarbonate are controlled by the state of stress of the test specimen. Whereas the yield stress of the material is relatively insensitive to the state of stress, the tendency of the material to microcavitate is strongly dependent on the residual stresses in the surfaces of a test specimen. The effects of quenching, annealing, post notching, solvent swelling and rate of testing on the modulus of toughness are all related to the state of compression on the free surfaces. The mechanism of deformation is shown by cinematography to consist of the nucleation of a shear band followed by microcavitation along the propagating band. Maximum toughness is obtained by suppressing microcavitation so as to promote shear yielding. When microcavitation occurs, it is the competition between propagating the microcavitation throughout the material and the generation of microcracks in the advancing shear band that controls the ultimate elongation.

ISSN:0032-3888    

DOI:10.1002/pen.760181603

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractChopped aramid fiber reinforced ionomer formulations were investigated as prototypes of military armor materials effective in providing protection against munition fragments. The dependence of ballistic impact resistance upon fiber openness was demonstrated by radiographs. Concentrations of 30 percent or less by volume of 1/4 and 1/2 in. fibers were injection moldable, However, the greater than optimum dispersion of fibers as a result of extrusion compounding or of the injection molding itself resulted in lower ballistic resistance and in usually lower tensile and flexural strength properties than were achieved by compression molding: Compression molding of suitably opened 1/4, 1/2 and 2 in. fibers produced rigid materials with fiber contents as high as 90 percent by volume. Ballistic impact resistance increased linearly with fiber content.

ISSN:0032-3888    

DOI:10.1002/pen.760181604

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIn‐plane mechanical properties, coefficients of thermal and hygroscopic expansion, and dimensional changes due to stress relaxation were measured as a function of direction in one, three, and five‐mil polyimide films. Although these films were made by a casting process, they exhibited significant anisotropy in the properties tested. This anisotropy was apparently due to preferential orientation of the polymer which occurred during the manufacturing proc

ISSN:0032-3888    

DOI:10.1002/pen.760181605

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractTo further investigate the nature of the specific interaction leading to the miscibility of poly(vinylidene fluoride), PVF2, with certain oxygen containing polymers, blends of PVF2with poly(ε‐caprolactone), PCL, with poly(vinyl methyl ether), PVME, and with poly(vinyl methyl ketone), PVMK, were prepared. PVMK/PVF2blends were found to be miscible while blends of PVME/PVF2and PCL/PVF2were found not to be miscible. These results show that the specific interaction with PVF2involves mainly the carbonyl group rather than the entire ester group. The relative effectiveness of having this group in the chain or pendant to it is not yet resolv

ISSN:0032-3888    

DOI:10.1002/pen.760181606

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA summary of the transitional behavior of blends containing poly(vinylidene fluoride), PVF2, and various oxygen‐containing polymers is presented. These data are used to establish the presence of a single miscible amorphous phase. The depression of the PVF2melting point in those blends judged to be miscible is analyzed using standard thermodynamic arguments to determine the heats of mixing between the amorphous diluents and the PVF2. These heats of mixing are exothermic indicating the presence of strong interactions between the binary pairs. A comparison between the observed interaction strengths and the dipole moments of the various diluents suggests that the exothermic heats of mixing are the result of strong dipole‐dipole interactions. Nearly all the miscible blends with PVF2show Lower Critical Solution Temperature (LCST) behavior. The direct correlation between the temperature location of this phase instability and the observed interaction strength suggests that the instability is more the result of enthalpic considerations than entropic o

ISSN:0032-3888    

DOI:10.1002/pen.760181607

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractPolystyrene (PS), high‐impact polystyrene (HIPS), and polyethylene (PE) have been investigated studying the pressure dependence of stress‐elongation behavior in tension over the range from atmospheric pressure to four kilobars at room temperature. The effect of strain rate was also observed for PS specimens. Tensile deformation of PS and HIPS has shown that the pressure‐transmitting fluid (silicon oil) acts as a stress crazing and cracking agent. Non‐sealed specimens of PS showed a brittle‐to‐ductile transition at 2.95 kbar while specimens sealed from the environment showed the same transition at only 0.35 kbar. Scales HIPS and PE specimens exhibited ductile behavior at all pressures. The extent of plastic deformation for PE was affected when specimens where exposed to the silicon oil environment. Surprisingly, HIPS exposed to the oil exhibited two transitions as the applied hydrostatic pressure was raised: a ductile‐to‐brittle followed by a brittle‐to‐ductile transition. Analysis of the stress‐elongation curves for sealed PS and HIPS specimens indicated that the pressure dependency of craze‐initiation stress differs from that of shear band initiation stress. The brittle‐to‐ductile transition occurred when the initiation stresses of both processes became equal. The principal stress for craze initiation showed almost no pressure dependency, suggesting that crazes initiate when the principal stress level of the tensile specimen reaches a critical value irrespective of the a

ISSN:0032-3888    

DOI:10.1002/pen.760181608

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect of molecular weight and polymerization temperature on thermal stability is critically examined. The concept of flow‐stability is introduced as a new method of evaluating the thermal stability of poly(vinyl chloride). In the processing temperature range 200 to 220°C, the viscosity decreases by a factor of two while the thermal stability decreases by a factor greater than thr

ISSN:0032-3888    

DOI:10.1002/pen.760181609

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760181601

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY