摘要:

AbstractPlastics in solid wastes is a problem of growing concern. Recycling of wastes is currently believed to be the most acceptable form of disposal in the long run; however, this route is known to be especially difficult for plastics. Recycling would be easier if the various generic types present in solid wastes, mainly polyethylene, polystyrene and poly (vinyl chloride), could be isolated; however, this would be very difficult and expensive. This is a first report on research aimed at evaluating the potential of recycling plastics as a polymer blend of the various generic types. This approach suffers from the difficulty that the different plastics are incompatible and the blend has poor mechanical properties. The extent of this problem is documented with data on many ternary blends employing virgin polyethylene, polystyrene and poly (vinyl chloride) of numerous grades likely to be found in solid wastes. Property degradation was found to be more severe as the complexity of the blend increased, indicating that general municipal wastes could be reused only in very low grade applications, whereas certain commercial wastes might have brighter prospects. Strategies for improving blend properties are outlined.

ISSN:0032-3888    

DOI:10.1002/pen.760120302

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractAn experimental program was conducted to study the thermochemical and flammability characteristics of an improved polyisocyanurate foam, uncoated and coated either with fluorinated copolymer or an intumescent material. Testing methods included thermal analysis; scanning electron microscopy; infrared photography; infrared spectroscopy; HLT‐15, ASTM D‐1692, Bureau of Mines Penetration, and XP‐2 smoke chamber flammability tests; limiting oxygen index (LOI); and a moderate‐scale fire simulation test. The uncoated and coated foams were found to have excellent flammability and insulation characteristics, although smoke development was subs

ISSN:0032-3888    

DOI:10.1002/pen.760120303

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractBased upon known polymerization kinetics, the extent and rate of re‐equilibration of nylon 6 have been analyzed. Relationships have been developed for the calculation of the rates of molecular weight change and monomer regeneration as functions of initial water concentration, degree of polymerization, and type and concentration of end groups. The results are in good agreement with published dat

ISSN:0032-3888    

DOI:10.1002/pen.760120304

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe phenomenon of extrudate distortion, which is called melt fracture, was studied for polystyrene samples of narrow and broad molecular weight distribution, and commerical samples of polypropylene and linear and branched polyethylene. It was experimentally found that the shear stress at the onset of melt fracture (τcr) is of the order of 106dynes/cm2and independent of the distribution of molecular weights. As the weight average molecular weight increases the shear stress τcrdecreases. For polystyrene extruded at τcrthe recoverable shear strain, which is defined to be half the ration (first normal stress difference/shear stress), was found proportional to the factorMzMz+1/Mw2which represents the distrubution of molecular weights. The proportionality is expected to hold for other polymer systems. The polymer behavior at the onset of melt fracture was explained in terms of Graessley's entanglement theory and his correlation between true and Rouse shear complian

ISSN:0032-3888    

DOI:10.1002/pen.760120305

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe rapid increase in the rate of application of thermoplastics in engineering design problems and the interest in the structural use of these materials have resulted in the requirement of comprehensive information about the behaviour of thermoplastics when subjected to cyclic loading conditions. In addition to the “total fatigue life” data already available for many materials, attempts have been made to analyse the crack initiation and steady crack growth processes and determine the effects of parameters such as mean load, frequency and crack geometry on the rate of crack propagation. The results of an investigation of these aspects of fatigue crack growth in a brittle thermoplastic, polymethylmethacrylate (PMMA), have already been reported. In this paper, the results of a test program devised to study the behaviour, at room temperature and in air, of a polycarbonate, (PC), under similar loading conditions, are presented. Fracture Mechanics concepts have been used to analyse the results. It was found that a relationship of the form ȧN= β λnalready shown to predict the cyclic fatigue crack propagation rate in PMMA, is also applicable to polycarbonate. However, when the effects of frequency and loading rate were studied, it was found that after the magnitude of parameter K̇( = ΔK/half the periodic time) exceeded 4000 lbf in.−3/2s−1, the influence of the mean level of stress intensity factor,Km, became negligible in comparison to the

ISSN:0032-3888    

DOI:10.1002/pen.760120306

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractIt has been recognized recently that suspension polyvinyl chloride granules consist of particles ca 1μ in diam which are linked together to form a three‐dimensional, sponge‐like lattice. This paper deals with the fusion process of this particulate structure of PVC resin during powder extrusion. Extrudates prepared under various extrusion conditions are investigated through the electron microscope using a methyl methacrylate (MMA) embedding method followed by ultrathin sectioning. The MMA embedding method has been proven to be an effective means of revealing the detailed structure of molded PVC. Results showed that the 1μ‐particles were subjected to breakdown due to heat and shear into fibrils 100‐300 Å in thickness, which were the final structure attainable by extrusion. Discussion was focused on the fibrillar structure especially in relation to the elasticity in plast

ISSN:0032-3888    

DOI:10.1002/pen.760120307

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThermal conductivity measurements were made on polyethylene samples which had been crystallized at different temperatures in order to vary density and lamellar crystal thickness. Tests were also made on polyethylenes which were oriented by mechanical shearing and by crystallization in a temperature gradient. The thermal conductivity increased linearly by 50% as the density went from 0.96 to 0.99 gm/cc. By orientation the conductivity was increased ten fold in the direction of molecular orientation and decreased two fold in the perpendicular direction. For samples oriented by deformation at different temperatures, the conductivity apparently correlates with birefringence.

ISSN:0032-3888    

DOI:10.1002/pen.760120308

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractPolymeric films deposited from the vapor of C4Cl6by the surface‐photopolymerization technique are electrically and mechanically continuous on various substrates when very thin. The thickness of the films depends upon irradiation time with wavelengths in the region 2000‐3000Å. Re‐irradiation in oxygen (air) of the polymeric films with light of these low wavelengths leads to patterned removal of the films. Since films 500Å thick and less can resist etchants for various substrates, a new and extremely thin positive photoresist system is possible. Resolution of etched substrates to lines a few microns wide has been demonstrated. If the polymeric films from C4Cl6are deposited from the monomeric vapor at lower substrate temperatures they are soluble in various solvents. Re‐irradiation with UV light with the films in vacuum produces a patternedfixingof the polymer with respect to acetone. A negative photoresist system is therefore possible. Again, films of thickness 500Å and less can resist various etchants such that substrates can be etched to high

ISSN:0032-3888    

DOI:10.1002/pen.760120309

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of rubber particle size on the tensile properties of rolled and unrolled acrylonitrile‐butadiene‐styrene has been studied by considering model systems consisting of mixtures of a small particle (0.1 micron diam) rubber,S, and a large particle (0.56 micron diam) rubber,L, in an SAN matrix. Before rolling, tensile toughness is characterized by crazing. While both rubber induce matrix crazing, ABS systems containing only theSrubber exhibits early failure due to crack formation, before crazing is propagated very far along the tensile axis. The inefficiency of the small particle rubber is interpreted in terms of high composite yield stress and insufficient distance between particles to allow craze branching. The efficiency of the small particle rubber is improved via the addition of a small amount of large particle,L, rubber to the composite or by a slight degree of cold rolling, both of which enhance craze propagation in the tensile direction. With further rolling, the tensile deformation mode changes from one of localized crazing, which is propagated, to one of uniform deformation, which occurs without craz

ISSN:0032-3888    

DOI:10.1002/pen.760120310

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractA stability analysis of fiber spinning of isothermal power‐law fluids has been carried out. The analysis for purely viscous fluids indicates that the critical extension ratio increases with an increase in power‐law constantqabove 1. Forqgreater than approximately 1.5, very high values of critical extension ratio are obtained. A stability analysis in the presence of viscous and inertial forces indicates that forq>1 critical extension ratio can be correlated to a quantityRq=q− 1 + 3Re, whereinReis the Reynolds number. For the values ofRqgreather than approximately 0.5, very high values of critical extension ratios are obt

ISSN:0032-3888    

DOI:10.1002/pen.760120311

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY