摘要:

AbstractSteady‐state permeation rates for pure CO2, CH4, and O2through two kinds of homogeneous dense membranes, copolymer of methyl methacrylate andn‐butyl acrylate and poly(methyl methacrylate), were measured at three temperatures between 20 and 40°C and upstream pressures up to 3 MPa. The logarithms of the mean permeability coefficients for CO2in both membranes increased linearly or quadratically with increasing upstream pressure, whereas the mean permeabilities for CH4and CO2were independent of pressure. The pressure dependence of the mean permeability coefficient for CO2was interpreted in terms of a modified free‐volume model of diffusion for a Henry's law population in glassy polymers. © 1993 John Wiley&So

ISSN:0021-8995    

DOI:10.1002/app.1993.070480601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMelt blends of SAN with SAN‐graft‐polybutadiene (PB) (g‐ABS) were prepared in a Brabender plasticorder. The effect ofg‐ABS on the morphology and mechanical and viscoelastic properties of the blends was studied up to 60 wt %g‐ABS. The brittle‐tough (BT) transition occurred around 20 wt %g‐ABS, and the viscosity increased monotonically withg‐ABS, showing yield behavior at ≥ 20%. The lower and higher glass transition temperatures (Tg) ofg‐ABS, each corresponding to theTgof PB and grafted SAN, decreased and increased with the addition of free SAN, and this was interpreted in terms ofgraftSAN—PB phase separation. © 199

ISSN:0021-8995    

DOI:10.1002/app.1993.070480602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractSemi‐interpenetrating networks have been synthesized from vernonia oil‐sebacic acid polyester network and poly(ethylene terephthalate) (PET). Bond interchange reactions during mixing of the two materials led to the formation of a miscible copolymer mixture, in which the vernonia oil was then cross‐linked with sebacic acid. The materials were phase‐separated, exhibiting two glass transitions, when the network was synthesized at 160°C, below the crystallization temperature of PET: however, a single stable glass transition (Tg) results after the material is heated to above the melting temperature of PET and cooled. When the vernonia polyester network was completely formed at 250°C, above the crystallization temperature of PET, noncrystalline, single‐Tgmaterial was created. The two‐phase semi‐IPNs were much tougher than were their constituent materials, with the 50% semi‐IPN over 15 times tougher than the PET from which it was made and over 50 times tougher than the neat vernonia oil elastomer, with tensile energy to break of 1780 kJ/m3. The single‐Tgmaterial was nearly 2.5 times as tough as the two‐phase material, with energy to break of 4400 kJ/m3. The microstructure of the two‐phase 50% semi‐IPN was investigated by transmission electron microscopy, which showed regularly shaped spherulites of 10–20 μm in diameter, as compared to irregularly shaped spherulites observed in a similar 50/50 castor oil urethane/PET semi‐IPN, in which the network formed simultaneously with PET crystallization. Scanning electron microscopy of the semi‐IPN fracture surfaces showed microscopic fibrils several hundred nanometers in diameter in both the two‐phase and single‐Tgmaterials, although only the two‐phase semi‐IPN had a macroscopically ro

ISSN:0021-8995    

DOI:10.1002/app.1993.070480603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe sensitivity of a low temperature slow rate penetration test to the dynamic mechanical response of ethylene‐vinyl acetate (EVA) copolymers with different compositions is clearly evidenced. The β‐molecular relaxation process occuring around −10°C controls the slow puncture behavior. The penetration resistance reaches a maximum value at this temperature and the type of rupture involved in the perforation mechanism varies on both sides of this critical temperature (brittle or ductile rupture). The parallel variations of the slow puncture resistance and of the high speed tensile impact strength with temperature, as well as with the vinyl acetate content, point to the reliability of the low temperature slow rate penetration test. This test thus appears as an efficient tool to simulate static mechanical deformations undergone by polymer films used in the sealed packaging of frozen food. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070480604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of peroxide and coagent, alone and together, on the crosslinking of HDPE during melt extrusion was studied. The melt flow index decreased rapidly with peroxide (1,3‐bis (t‐butylperoxy‐isopropyl) benzene), and smoothly with trimethylolpropanetriacrylate (TMPTA), but showed a small increase with parabenzoquinone (PBQ).Melt viscosity of 0.3 phr peroxide‐treated PE responded elastically, whereas that of 0.3 phr TMPTA showed yield behavior.Tm(crystalline melting temperature) andTc(crystallization temperature) increased with peroxide,Tmdecreased, andTcincreased with TMPTA. ΔHf(heat of fusion) increased at 0.05 phr followed by a sharp drop, more with peroxide and less with TMPTA. Hardness and preyield properties increased with TMPTA, and peroxide (except hardness) with the loss of elongation at break. The most significant improvement was obtained with impact strength, over 5 times with peroxide and 7 times with TMPTA.When the TMPTA was used in combination with peroxide, more redution in MI, followed by a further increase of hardness, modulus, and strength, was obtained, but impact strength was decreased below that of TMPTA alone. © 1993 John Wiley&

ISSN:0021-8995    

DOI:10.1002/app.1993.070480605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe transitions occurring in gutta‐percha (transpolyisoprene) below the melting point were determined with DMTA and DSC. A comparison of the results obtained with these two methods showed satisfactory agreement. The thermal properties of native and commercial gutta‐percha samples (Tg= 38 ± 2°C andTm= 69 ± 3°C) were investigated, both before and after annealing (at different times and temperatures), and at environments of different relative humidities. An increase in the draw ratio also proved to enhance the percentage crystallinity (%K) and improve the thermal stability (higherTgs andTms) of gutta‐percha. Finally, the activation energies ΔE(33.9–40.2 kj/mol ×K) at glass transition temperature were determined and correlated to the percentage content (%) of the commercial gutta‐percha samples in native gutta‐percha. © 1993 Jo

ISSN:0021-8995    

DOI:10.1002/app.1993.070480606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractSeparation of acetic acid/water mixtures by pervaporation was attempted by silicone rubbercoated polyetherimide membranes. In particular, the effect of the pore size of the polyetherimide membrane and the condition of silicone rubber coating on the performance of the composite membrane was investigated. It was found that the composite membrane could become either water selective or acetic acid selective, depending on the pore size of the support membrane and the condition of the silicone rubber coating. Thus, the overall performance of the composite membrane can be governed, either by the top coated layer or by the bottom support layer.

ISSN:0021-8995    

DOI:10.1002/app.1993.070480607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn order to promote chemical linkage between polyester PET fibers and thermoplastic or elastomer matrices, a diazide derivative has been synthetized and reacted with the free hydroxyl groups of the fibers. The completion of the reaction was controlled by means of IR spectroscopy and chemical analysis, and fiber characterization was carried out by thermogravimetric and DSC techniques. The obtained results permit the determination of the suitability of the synthetized diazide to functionalize PET fibers that could be used as reinforcing fibers for polymer matrices composites. © 1993 John Wiley&Sons, Inc

ISSN:0021-8995    

DOI:10.1002/app.1993.070480608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractUrethane prepolymer was prepared by reacting two moles of tolylene diisocyanate with one mole of poly(ethylene glycol) (mol wt 400), followed by end‐capping with two moles of 2‐hydroxyethyl methacrylate at room temperature (30 ± 1°C) in the presence of stannous octoate as catalyst. Different proportions of methyl methacrylate (MMA) were added to the urethane prepolymer in order to study the effect of composition on mechanical properties. Sheets were fabricated by adding 1% azobis (isobutyronitrile) (w/w) to this solution. All the copolymer sheets had a transmittance similar to the PMMA sheet, in the wavelength range of 400–800 nm. Tensile strength and modulus decreased with decreasing MMA content, whereas percent elongation at break increased. All the samples showed 2–3 stages of degradation. Initial decomposition temperature increased with increasing carbamate content. © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070480609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThree new series of poly(bisbenzoylamine imide)s, incorporating different aromatic diamines, have been synthesized. The polymers, obtained by the two‐step procedure, have been characterized by DSC, TGA, X‐ray, FTIR, and1H‐NMR methods. Thermal analysis showed glass transition temperatures in the range of 200°–250°C and decomposition at 430°–495°C. Most DSC runs displayed an exothermic event aboveTgthat was due to cold crystallization of the polymer molecules. A melting point was not observed. The new polymers, even before annealing, showed sharp X‐ray diffraction patterns, evidence of semicrystallinity. The polymers, soluble in polar solvents, were analyzed by NMR in solution. Typical chemical shifts for the bisbenzoylamine protons were reported; FTIR spectra showed the characteristic imide peaks. Due to a near overlap of the carbonyl vibration of the imide group with the bisbenzoylamine carbonyl, the latter vibration was detected in only one series. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070480610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY