摘要:

AbstractUniaxial tension tests to, the yield point were performed on poly(hexamethylene adipamide) (nylon 6,6) as a function of temperature from 21 to 200°C at a strain rate of 2 min−1. At 21 and 60°C, measurements were also made at strain rates from 0.02 to 8 min−1. Using simple rate theory, reasonable values of activation volume were obtained, but the simple theory is inadequate to determine the activation energy. The yield‐strain temperature dependence changes at 160°C as a result of a reversible crystal‐crystal transition. Because of this behavior of the yield strain, the yield energy is not a linear function of temperature, as observed for several othe

ISSN:0032-3888    

DOI:10.1002/pen.760250202

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThermal conductivity measurements with a modified Couette flow cell were obtained as a function of shear rate for two linear polyethylene melts of weight‐average molecular weights 27,300 and 56,700, respectively. The lower‐molecular‐weight polyethylene revealed a maximum decrease in thermal conductivity of 55 percent at 150s−1. After shearing at 400s−1, approximately 90 minutes was required to recover the value corresponding to the zero shear condition. This was considered consistent with molecular orientation into the flow direction during shear with a subsequent relaxation upon the removal of stress. The higher‐molecular‐weight polyethylene gave a similar decrease in thermal conductivity at 50s−1. Unlike the lower‐molecular‐weight melt, an increase was observed at higher shear rates. Enhancement of energy transport via cluster flow mechanism was presented as a possible interpretation of these results. A theory of molecular orientation of liquid poly(dimethylsiloxane) (PDMS) under shear flow was previously developed from thermal conductivity and birefringence data of this material. An attempt to clarify the difference in behavior between the two melts examined in this work, and between the polyethylene melts and the PDMS previously s

ISSN:0032-3888    

DOI:10.1002/pen.760250203

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA semiquantitative bubble formation mechanism is presented for the baking of polymer films, utilizing poly(methyl methacrylate) (PMMA)‐ethyl acetate (EA) solutions as the model system. It is shown that bubble growth phenomena can he accounted for in terms of the competition between vapor pressure buildup and the rate of vapor dissolution. According to the proposed mechanism, the local pressure buildup of solvent in the polymer film is controlled by the solvent partial pressure above a solution having a planar interface at the corresponding temperature and solvent concentration. This pressure can he estimated by Raoult's law. The vapor dissolution rate, on the other hand, is dominated by the liquid‐phase diffusion of the solvent. A method of obtaining the diffusion coefficient as a function of temperature and solvent concentration from isothermal thermogravimetric analysis (TGA) is also gi

ISSN:0032-3888    

DOI:10.1002/pen.760250204

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractTo develop polymer systems with improved lithographic resist properties, terpolymers of methyl methacrylate/methacrylonitrile/methyl α‐chloroacryate (MMA/MCN/MCA), methyl methacrylate/methacrylonitrile/α‐chloroacrylonitrile (MMA/MCN/ACAN), and methyl methacrylate/methacrylonitrile/vinylidene chloride (MMA/MCN/VDC) were prepared by emulsion polymerization. Also one methyl methacrylate/ methyl α‐chloroacylate/α‐chloroacrylonitrile (MMA/MCA/ ACAN) terpolymer was prepared. The radiation susceptibilities of these terpolymers were measured using the60Coγ‐irradiation method. Molecular weights were determined both by membrane osmometry and gel permeation chromatography. All terpolymers exhibited higher radiation‐degradation susceptibilities than poly(methyl methacrylate). TheGsvalues did not follow the general trend, previously observed with MCN/MCA copolymers, of being directly proportional to the respective terpolymer compositions. In some cases, the addition of small quantities of α‐chlorine‐containing monomers causedGxto increase. This observation greatly differs from those observed for copolymer systems such as MMA/MCA, MCN/MCA, MMA/ ACAN, etc. studied previously. Terpolymerization gives highly soluble polymers especially suitable for wet development by many solvents. This is an important consideration for polymers with high mole fractions of methacrylonitrile (MCN) or vinylidene chloride (VDC) which are rendered soluble in development solvents. The electron‐beam sensitivities were obtained for samples of three classes of the terpolymers and they were higher than that of PMMA. For example, at 20Kev a 62/34/4 MMA/MCN/MCA terpolymer exhibited a sensitivity of 1.3 × 10−5coulombs cm−2atl/lo= 1. The introduction of ACAN narrows the working range for positive resist behavior. For example MMA/MCN/ACAN(41/40/19) has a sensitivity of 8.3 × 10−6coulombs cm−2at l/l0= 0.6 but it crosslinks at 1 − 1.3 × 10−coulombs cm2. The MMA/MCN/VDC(21/76/3) polymer was about 25 times more sensiti

ISSN:0032-3888    

DOI:10.1002/pen.760250205

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn extruding thick polymeric objects such as bars, voids may form as a consequence of fast cooling. As is well known, this phenomenon is due to volume contraction of the inner zone which takes place when the external “shell” is already solidified. Recent experimental results on this effect show the influence of various parameters such as polymer melt viscosity, bar diameter, and operating pressure upon a critical extrusion velocity above which voids are detected. A detailed analysis of the phenomena which are thought to be relevant is presented and compared with the experimental resu

ISSN:0032-3888    

DOI:10.1002/pen.760250206

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe subject of crazing in crystalline polymers is reviewed and specific consideration given to crazing in polypropylene (PP). Tensile tests conducted over a wide spectrum of temperatures and strain rates indicate that, for a given test temperature, there exists a critical strain rate above which crazing is the dominant deformation mode of PP. Similarly, for a given strain rate, there exists a critical temperature which demarcates crazing from shear yielding as the characteristic process of deformation. High deformation rates and low temperatures favor crazing, while low rates and high temperatures favor shear yielding. Crazes in crystalline PP were found to be morphologically similar to those in glassy polymers: high reflectivity, large area‐to‐thickness ratio, and planarity. They have a higher tendency to bifurcate than those in glassy polymers. Two types of craze fibrils could be identified: those parallel to σ11, and the randomly oriented interconnecting fibrils. It is demonstrated that microtome‐trimming at low temperature followed by suitable chemical treatment is an effective technique of sample preparation for SEM examination of craze morphology in crystalline polymers. Further evidence has been provided that crazes in spherulitic polymers do not in general follow an interspherulitie path, but propagate through spherulites. The length of a craze in PP is not restricted to one spherulite diameter, nor does it grow ra

ISSN:0032-3888    

DOI:10.1002/pen.760250207

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe frequency dependence of the complex‐shear modulus of a nonbrominated flame‐retardant polycarbonate has been successfully represented from 1 hertz (hz) to 1 gigahertz (ghz) at 190°C using a mechanical analog of the Cole‐Cole dielectric analysis. Two sets of retardation times were required centered about 74 msec and 16 μsec. The β value for the short time response was 0.83 and for the longer time response was 0.58. The values ofJ oNdetermined from the common point at which the terminal‐zone arc and the transition‐zone arc touch theJc″ = 0 axis yields an entanglement molecular weight,Me

ISSN:0032-3888    

DOI:10.1002/pen.760250208

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractRandom multiblock copolymers of bisphenol‐A‐polycarbonate and poly(dimethylsiloxane) were hot‐pressed or solvent cast into films which were studied by dynamic mechanical methods over the range 11 to 110 hertz (Hz) and 100 to more than 2200 Hz, respectively. The samples were studied also by differential‐scanning calorimetry. The two phases are separated well in spite of the low‐molecular weights of the blocks. This separation is altered by thermal history and by the solvent medium when solvent casting is used to prepare the films. The damping properties do not vary greatly with frequency. Damping is greatest near the glass‐transition temperatures of the two components. The expansion of the block copolymer with heat appears to be retarded by the polycarbonate phase until the glass transition of that phase is

ISSN:0032-3888    

DOI:10.1002/pen.760250209

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe flow of molten polymers in the calender bank has been computed using a finite‐element method with stream function and vorticity. Two nonsymmetrical‐recirculating regions have been obtained fully in agreement with the experimental observations on poly(vinyl chloride) melt banks. The pressure distribution along the flow axis is very close to the one obtained using the classical‐lubrication approxim

ISSN:0032-3888    

DOI:10.1002/pen.760250210

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA method is developed by which polymer molecular weight and its distribution can be accurately determined by deconvolution of dynamic melt viscoelastic properties in the terminal and plateau zones. The method is illustrated with a series of monodisperse (narrow‐distribution) and polydisperse (broaddistribution) polystyrenes. TheMn,Mw, andMn/Mwvalues obtained are in excellent agreement with those determined by light scattering, osmometry and gel permeation chromatography with less than 5 to 10 percent error. The differential molecular‐weight distribution curves obtained coincide wall with those obtained by gel permeation chromatography. The method is applicable to insoluble as well as soluble polym

ISSN:0032-3888    

DOI:10.1002/pen.760250211

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY