bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal conductivity of a polymer composite
Authors: Agari Y. , Ueda A. , Nagai S.
Published: April 2003

A prediction equation for thermal conductivity of polymer composites reported in our previous papers has been revised in terms of two view points: (1) estimation of thermal conductivity of a composite using an idea of reduced thermal conductivity; and (2) the effect of ease in forming conductive filler chains on thermal conductivity is related to the CVF value in electric conductivity of the composite. The new equation was confirmed to be adaptable to thermal conductivities of varieties of polymer composite systems filled with spherical or irregular fillers. The equation was also considered to explain thermal conductivity of polymer composites filled with fibers. Further, it was found that thermal conductivities of fiber composites can be estimated by introducing a factor of the CVF value or aspect ratio (L/D) into the new equation. © 1993 John Wiley & Sons, Inc.
Physical properties of 2‐hydroxyethyl methacrylate‐grafted silk fibers
Authors: Tsukada Masuhiro , Freddi Guiliano , Monti Patrizia , Bertoluzza Alessandro , Shiozaki Hideki
Published: April 2003

This paper deals with the physical properties of silk fibers grafted with 2‐hydroxyethyl methacrylate (HEMA). Both tensile strength and elongation measured in the dry and wet states gradually decreased with increasing weight gain. The initial modulus of the grafted silk fibers in the dry state sharply increased in the weight gain range of 0–16%, then decreased to a lower value than the reference untreated sample. The refractive indices parallel and perpendicular to the fiber axis decreased, though the former showed a steeper slope. Accordingly, birefringence and isotropic refractive index also decreased, suggesting a lower degree of crystallinity and molecular orientation of grafted silk fibers. DSC, TMA, and TGA curves of the HEMA‐grafted silk fibers indicated an increased higher thermal stability of silk fibers due to the HEMA grafting. The dynamic mechanical measurements showed that the thermally induced molecular movement of both amorphous and crystalline domains of silk fibers was enhanced by HEMA grafting. X‐ray diffraction curves, however, implied that the crystalline structure of the silk fibroin remained unchanged regardless of HEMA polymerization. The introduction of HEMA polymer in silk fibers was evidenced by the infrared spectra, exhibiting the absorption bands characteristic of either the grafted HEMA polymer and the fibroin molecules with ordered β structure. © 1993 John Wiley & Sons, Inc.
Kinetics of epoxy resins formation from bisphenol‐A, tetrabromobisphenol‐A, and epichlorohydrin
Authors: Gao Jungang
Published: April 2003

The kinetics of formation of epoxy resins derived from bisphenol‐A, tetrabromobisphenol‐A, and epichlorohydrin under stoichiometric conditions was considered. The kinetics of reaction was studied by taking into account the consumption of the added alkali and epoxide group of epoxide oligomers. The obtained results satisfactorily explained that the reactivity of bisphenol‐A with epichlorohydrin is higher than that of tetrabromobisphenol‐A. The rate of dehydrochlorination of chlorohydrin ether in the presence of alkali and water is much higher than that of the rate of condensation of phenolic hydroxyl group with epichlorohydrin. The apparent reaction order of phenolic groups with epichlorohydrin and terminal epoxide groups in the oligomer are second order. The rate constants and reaction activation energy were determined. The results are discussed. © 1993 John Wiley & Sons, Inc.
The mechano‐sorptive behavior of flexible water‐blown polyurethane foams
Authors: Dounis Dimitrios V. , Moreland J. Cal , Wilkes Garth L. , Dillard Dave A. , Turner Robert B.
Published: April 2003

Samples of flexible water‐blown slabstock polyurethane foams were compressed under constant load to study the effects of cycling moisture content on creep behavior and compare this behavior with the creep response where either a constant high or low moisture environment existed at the same temperature. Three sets of foams were tested: (1) 4 pph water content slabstock foam; (2) 5 pph water content slabstock foam; and (3) 2 pph water content molded foam. As the moisture conditions were cycled from low to high humidity while maintaining constant temperature in an environmental chamber, the compressive strain increased in subsequent steps with larger increases observed during the desorption portion of the humidity cycling. All three sets of foams showed similar behavior at a given temperature. At a temperature of 40°C, the strain levels under cyclic moisture conditions surpassed those levels observed at the highest constant relative humidity. During the first absorption step, the creep level increased. During any subsequent absorption step, the creep level either increased very little or none at all. Finally, during any desorption step, the creep level increased. This overall phenomenon of enhanced creep under cyclic moisture levels is attributed to water interacting with the hydrogen bonded structure within the foam. These hydrophillic interactions, principally promoted within the hard segment regions due to high hydrogen bonding, are disrupted causing slippage and increased in strain. As the foam is rapidly dired, regions of free volume are induced by the loss of water thus causing further increases in strain Prior to the reestablishment of well ordered hydrogen bonding. Further support to this proposition was given by the results obtained at a temperature of 90° C where it is well known that hydrogen bonds are much more mobile. Here, the strain levels under cyclic moisture conditions were nearly the same as those under constant high relative humidity. Weakening of the hydrogen bonds by means such as increased temperature resulted in similar strain levels to those under cyclic moisture levels. © 1993 John Wiley & Sons, Inc.
Effect of γ‐irradiation and temperature on the structure of metal chloride treated poly(acrylamide)
Authors: Moharram M. A. , Rabie S. M. , Daghistani A. Y.
Published: April 2003

The gamma‐induced changes in the structure of Poly(Acrylamide) (PAAm) treated with metal chlorides were investigated by following the corresponding variations in their ultra‐violet spectra. Careful examination of UV spectra revealed that irradiation of the specimens results in the appearance of an absorption peak at 275 nm whose intensity depends on the applied dose and the nature of the metal ions. This band is ascribed to the formation of the carbonyl group. The results indicate that the dependence of the intensities of the band at 275 nm on the nature of the metal used provides strong evidence for the formation of metal polymer complexes. It was found that the pretreatment of PAAm with the appropriate concentration of ZnCl2, CoCl2, or NiCl2 reduces the effects of heating and the oxidation effects of γ‐irradiation. These results show that these metal ions can be used as stabilizers against thermal degradation of PAAm in the temperature range up to 160°C. © 1993 John Wiley & Sons, Inc.
Investigation of the formation of physical damage on automotive finishes due to acidic reagent exposure
Authors: White D. F. , Fornes R. E. , Gilbert R. D. , Speer J. A.
Published: April 2003

Automotive paints with clear‐coat surfaces can be physically damaged by exposure to acidic reagents produced in a smog chamber designed to reproduce real environmental conditions. Visual and reflectance microscopy observations show that deposition of material formed from the reaction of the clear coat and the reagent drop occurs on the paint surface after the drop evaporates to a critical size, with the greatest deposition occurring at the edge of the drop. This type of deposition suggests a free‐energy minimization process favoring the formation of stable nuclei at the reagent drop edge. With heating after the drop evaporation to simulate exposure to the sun, a damaged area containing sulfur that is in the shape of a circular ring is observed at the location of the deposits. The majority of the visual damage appears to result from an interaction between the deposit and the paint at elevated temperatures. Results from profilometry, scanning electron microscopy, and reflectance microscopy show that the damaged areas are ring‐shaped cracked blisters on the surface resulting from the clear coat separating into layers. © 1993 John Wiley & Sons, Inc.
Specialty polyurethane soft segments. IV. Reactions of aminated poly(propylene glycols) with isatoic anhydride
Authors: Harris Robert F. , Lopez Karen M.
Published: April 2003

Although it has been reported that aminated poly(propylene glycols) react with isatoic anhydride to cleanly yield the corresponding o‐aminophenyl amide (II), this paper shows that a competing reaction leads to the formation of about 10% of the corresponding urea carboxylic acid (III). This impurity (unreactive toward polyisocyanates) limits the use‐fulness of (II) in urethane/urea polymers. A procedure has been developed to quantify (II) and (III). Based on the insight gained, a process has been developed to produce the corresponding o‐aminophenyl amide derivatives of aminated poly(propylene glycols) in a state of high purity (˜100%). A given aminated poly(propylene glycol) is added dropwise to a siurry of isatoic anhydride in an inert fluid (such as toluene or a previously prepared product) at a temperature (60–100°C) at which reaction is rapid. Local excesses of unreacted amine are minimized to prevent formation of urea carboxylic acid impurities. This process has been applied to the preparation of the corresponding derivatives of a variety of aminated poly(propylene glycols). © 1993 John Wiley & Sons, Inc.
Interpenetrating polymer networks from hydroxy‐terminated polybutadiene‐based polyurethanes and poly(methyl methacrylate)
Authors: Choudhary Veena , Gupta Rajni
Published: April 2003

Isocyanate‐terminated urethane prepolymer was prepared by reacting 2 mol of tolylene diisocyanate (TDI) with 1 mol of hydroxy‐terminated polybutadiene (HTPB, mol. wt. = 3000) at room temperature (30 ± 1°C) in the presence of stannous octoate as the catalyst. Urethane prepolymer was subsequently mixed with 1,4‐butane diol: glycerol (6 : 1 ratio), methyl methacrylate (MMA), and ethylene glycol dimethacrylate (EGDMA) to give an interpenetrating polymer network. Stannous octoate was used as a catalyst to give network I, and azobisisobutyronitrile (AIBN), as an initiator to give network II. Different proportions of MMA were added to the prepolymer for studying the effect of composition on mechanical properties, thermal behavior, and optical properties. The mechanothermal behavior was analyzed using a dynamic mechanical thermal analyzer. Tensile strength and modulus decreased with decreasing MMA content, whereas percent elongation at break increased. Thermal stability of the sample increased with increasing urethane content. © 1993 John Wiley & Sons, Inc.
Synthesis of poly(chloroprene‐co‐isobutyl methacrylate) and its compatibilizing effect in polychloroprene/poly(isobutyl methacrylate) blends
Authors: Park Choon Keon , Ha Chang Sik , Lee Jin Kook , Cho Won Jei
Published: April 2003

A copolymer of chloroprene (CP) and isobutyl methacrylate (iBMA) [poly(CP‐co‐iBMA)] was prepared in benzene by radical copolymerization. For comparison, the graft copolymer of iBMA onto polychloroprene (CR) [poly(CR‐g‐iBMA)] was also prepared. The glass transition temperature of the poly(CP‐co‐iBMA) was about −32.4°C. The monomer reactivity ratios determined by the Finneman‐Ross method were given as r1 (CP) = 1.80 and r2 (iBMA) = 0.74 in the copolymerization of CP and iBMA, respectively. Miscibility of blends of CR and poly(isobutyl methacrylate) (PiBMA), prepared by casting from tetrahydrofuran (THF) solution, was investigated by their glass transition temperature behaviors and morphologies. Although the blends of CR and PiBMA were incompatible, the addition of poly(CP‐co‐iBMA) or poly(CR‐g‐iBMA) enhanced miscibility between the two base polymers. It was found that the extent of partial miscibility becomes larger when adding poly(CP‐co‐iBMA) than poly(CR‐g‐iBMA) as a third component to the CR/PiBMA blend of 50/50 wt % composition. © 1993 John Wiley & Sons, Inc.
Some filler effects on cross‐linking of unsaturated polyesters
Authors: Paauw M. , Pizzi A.
Published: April 2003

The effect of five fillers on the cross‐linking macro‐and microcharacteristics of simple unsaturated polyester resins was investigated by differential scanning calorimetry (DSC), reactivity tests, and gel time tests. Glass beads and silica flour appeared to have little influence on the cross‐linking reaction of the resin itself, their effect being comparable to mere dilution of the resin. Kaolin presented some interaction with the resin due to its absorption characteristics and acid groups. Reground polyester/glass fiber powder and especially wood flour appeared to present clear chemical interactions with the curing behavior of the resin. Wood flour, in particular, was shown by DSC analysis to strongly co‐react with the resin during cross‐linking and altered markedly the resin enthalpy change and energy of activation during curing. The wood flour component causing the altered behavior of the resin appears to be lignin. DSC analysis of resins filled with three different types of isolated lignins indicated that this wood flour component reacts in a heterogeneous phase reaction with the resin during cross‐linking. It appears that it is the lignin unsaturated carbon–carbon double bonds at the polyester/wood flour and at the polyester/lignin interphases that are likely to co‐react by heterogeneous phase radical cross‐linking with the polyester resin and styrene unsaturation, markedly changing the resin curing behavior. © 1993 John Wiley & Sons, Inc.
Dynamic viscoelasticities for short fiber‐thermoplastic elastomer composites
Authors: Guo Wuyun , Ashida Michio
Published: April 2003

Dynamic moduli, E′ and E″, and loss tangent tan δ were investigated for thermoplastic elastomers (TPEs), styrene‐isoprene‐styrene copolymers (SISs), styrene‐butadiene‐styrene copolymer (SBS), and Hytrel and composites reinforced by poly(ethylene terephthalate) (PET) short fibers. The styrenic TPEs have a typical rubbery behavior and the Hytrel TPE has medial characteristics between rubber and plastic. Both E′ and E″ of the composites depended on the matrix as well as the fiber loading and fiber length. Based on the viewpoint of different extensibility between the fiber and the matrix elastomer, a triblock model was considered for estimating the storage modulus of the short fiber‐TPE composites as follows: Ec = αVfEf + β (1 − Vf) Em, where α and β are the effective deformation coefficients for the fiber and the matrix elastomer, respectively. They can be quantitatively represented by modulus ratio M (= Em/Ef) and fiber length L: α = ( Ln + k) M/ ( LnM + k), β = (1 − α Vf)/ (1 − Vf), where the constants n and k are obtained experimentally. When k = 0.022 and n = 0.45, Ec of the TPE composites agreed well with the prediction of the proposed model. The relaxation spectrum of the composites showed a distinct main peak ascribed to the matrix elastomer, but no peak to the PET fiber. The relative damping of main relaxation, (tan δmax)c/(tan δmax)m, decreased monotonously with increasing fiber loading and fiber length and with decreasing modulus of matrix elastomer. Thus, the relative damping may be attributed not only to the volume effect of matrix, but also to the unevenness of the strain distribution in the matrix phase, which depends on the fiber length and the matrix's modulus. The findings prove that the different extensibility between fiber and matrix and the uneven distribution of strain in matrix were important for the short‐fiber reinforcement of the TPE composites. © 1993 John Wiley & Sons, Inc.
Oxidation induction time correlations with radiation dose and antioxidant concentration in EPR and XLPE polymers
Authors: Mason L. R. , Doyle T. E. , Reynolds A. B.
Published: April 2003

Oxidation induction time (OIT), as measured by differential scanning calorimetry, is useful in assessing the extent of degradation in polymeric materials. Values of OIT for typical EPR and XLPE polymer insulation materials used for electric cable insulation in nuclear power plants were measured as a function of both radiation dose and antioxidant concentration after accelerated aging. Irradiations were performed at the University of Virginia Cobalt Irradiation Facility. OIT was found to decrease exponentially with increasing radiation dose and with decreasing antioxidant concentration for both ethylene‐propylene rubber (EPR) and cross‐linked polyethylene (XLPE) insulations. It was determined experimentally that, when polymers are subjected to a constant radiation dose rate, antioxidant concentration decreases linearly with time, and it was shown that this variation is consistent with theoretical autoxidation kinetics. © 1993 John Wiley & Sons, Inc.
Time–temperature viscoelastic behavior of an interlaminar‐toughened epoxy composite
Authors: Woo E. M.
Published: April 2003

Viscoelastic deformation of an interlaminar‐toughened laminated composite was investigated, and effects of the interlaminar heterogeneity were examined. Dynamic mechanical experiments were performed on the laminates and neat matrix resins of the laminated composite in the temperature range of 82–210°C to probe linear time‐temperature behavior. The reason for using torsional shear deformation for probing was that it usually is more dominated by the matrix. In the relatively low‐temperature regime, time‐temperature superposition was applicable, and the effect of the interlaminar heterogeneity was found to be not pronounced. A methodology based on the Arrhenius activation energy approach was proposed for predictions of long‐term viscoelasticity of the heterogeneous‐phase composite. The effects of the interlaminar toughening phase became more significant at temperatures greater than the Tg of the toughening phase and presented some limitations for accurate predictions of time‐dependent behavior. © 1993 John Wiley & Sons, Inc.
Phase separation phenomena of polysulfone/solvent/organic nonsolvent and polyethersulfone/solvent/organic nonsolvent systems
Authors: Wang Dongliang , Li K. , Sourirajan S. , Teo W. K.
Published: April 2003

The precipitation values (PVs) of several organic nonsolvents in polysulfone (PSf)/solvent and polyethersulfone (PESf)/solvent systems were measured in temperatures ranging from 10 to 80°C by the direct titration method and compared with those of water in the same systems. The solvents used were N‐methyl‐2‐pyrrolidone (NMP) and N,N‐dimethylacetamide (DMAC); the organic nonsolvents employed were methanol, ethanol, 1‐propanol, 1‐butanol, 1‐pentanol, ethylene glycol, and diethylene glycol as well as acetic acid and propionic acid. The compositions of nonsolvent, polymer, and solvent at the precipitation points for different polymer concentrations up to 10 wt % were also determined at 30°C with respect to both the polymers and six nonsolvents presented. These results were used to obtain the polymer precipitation curves in the polymer‐solvent‐nonsolvent triangular phase diagrams and to determine the theta composition of solvent‐nonsolvent for a polymer. The results show that the precipitation value of nonsolvent in polymer/solvent systems depends on both the nature of polymer, solvent, and nonsolvent used and the temperature. The effect of temperature on the precipitation value was observed to be dramatically different for different polymer/solvent/nonsolvent systems. These results were explained on the basis of polar and nonpolar interactions of the polymer, solvent, and nonsolvent system. The results indicate that the precipitation values of the type presented in this paper not only give a relative measure of the nonsolvent tolerance of the polymer/solvent system involved and the strength of solvent and nonsolvent for the polymer, but also determine the relative location of the polymer precipitation curve in the triangular phase diagram. © 1993 John Wiley & Sons, Inc.
Novel UV absorbers prepared from 2,4‐dihydroxybenzophenone and hexachlorocyclotriphosphazene
Authors: Inoue Kenzo , Takahata Hiroaki , Tanigaki Teiichi
Published: April 2003

The UV‐stabilizing ability and thermal loss from the polystyrene film of novel UV absorbers, 2‐[(3‐hydroxy‐4‐benzoyl) phenoxy] pentachlorocyclotriphosphazene (HBPC) and hexakis[ (2‐hydroxy‐4‐benzoyl) phenoxy] cyclotriphosphazene (HBPP), were investigated. The UV‐stabilizing ability of HBPC estimated by the formation of carbonyl groups in polystyrene was comparable to that of 2,4‐dihydroxybenzophenone (DHB), suggesting that the phosphazene moiety does not affect the efficiency of the stabilizing ability of DHB units. No significant difference of efficiency per stabilizing units between HBPC and HBPP was observed. HBPC and HBPP are noteworthy for their low thermal losses from the polystyrene film, i.e., the thermal loss of HBPP was completely suppressed and the diffusion coefficient of HBPC at 160°C was two orders of magnitude smaller than that of DHB. The thermogravimetric analysis and differential scanning calorimetry measurement showed that HBPC and HBPP are nonvolatile and stable up to 230 and 300°C, respectively. © 1993 John Wiley & Sons, Inc.
Melt viscosity increase during rheological testing of poly(phenylene sulfide)
Authors: Fagerburg D. R. , Watkins J. J. , Lawrence P. B.
Published: April 2003

Poly(phenylene sulfide) (PPS) made via the melt polymerization of p‐diiodobenzene and sulfur has previously been reported to increase in melt viscosity with time during rheological testing. Analysis of the oligomer from cleavage of PPS chains at the disulfide bonds via solution in 1‐chloronaphthalene demonstrated that the disulfide content of the polymer decreased with rheological testing time. DSC of the polymer before and after rheological testing in combination with the Tcc and Tm of the chain fragments after the dissolution/cleavage in 1‐chloronaphthalene showed that many samples exhibited primarily chain extension rather than chain branching, whereas for many others, some degree of chain branching occurred. This is currently only qualitatively understood. Chain branching as the exclusive mechanism of melt viscosity increase during rheological testing appears untenable in light of the Tm, in particular, of the chain fragments and also the polymer prior to chain cleavage. © 1993 John Wiley & Sons, Inc.
Optimal operations of semibatch solution polymerization of acrylamide with molecular distribution as constraints
Authors: Jang Shi‐Shang , Tan Di‐Ming , Wei I‐Jen
Published: April 2003

In this work, optimal control profiles of a semibatch solution polymerization of an acrylamide system are investigated for the first time. The control variables are the monomer and initiator feed rates. The objective function is the operating time of each batch. One of the operating constraints is the maximum of the polymerization rate of the reaction, which is important due to the limitation of the heat‐removal equipment. The expected number‐average molecular weight and molecular weight distribution are also included as constraints in order to guarantee the quality of the products. A nonlinear programming approach developed by Jang and Yang is used for solving the equations. Several simulation and experimental runs show that the operation of this semibatch system is very smooth and conversions are fitted well by the model. The molecular weights and molecular weight distributions of the polymer products are also well controlled. © 1993 John Wiley & Sons, Inc.
Pressure–volume–temperature relationships for poly(vinylidene fluoride) and polyamide‐11
Authors: Rodgers Patrick A.
Published: April 2003

Experimental specific volume data as a function of temperature (30–269°C) and pressure (0–2000 bar) are presented for two semicrystalline polymers, namely, poly(vinylidene fluoride) and polyamide‐11. Data for the melt state were used to determine the characteristic parameters for six theoretical equations of state as well as the empirical Tait equation. The theories employed were the cell models of Flory–Orwoll–Vrij, of Prigogine et al., and of Dee and Walsh, the latticefluid theory of Sanchez and Lacombe, the hole theory of Simha and Somcynsky, and the semiempirical model of Hartmann and Haque. Solid‐state data were also fit using the Hartmann–Haque and Tait equations. © 1993 John Wiley & Sons, Inc.
Pentavalent vanadium ion–cellulose thiocarbonate redox‐system induced grafting of methyl methacrylate and other vinyl monomers onto cotton fabric
Authors: Hebeish A. , El‐Rafie M. H. , Zahran M. K.
Published: April 2003

Cellulose thiocarbonate was prepared by reacting cotton cellulose fabric with carbon disulphide in the presence of sodium hydroxide. The treated fabric formed, with pentavalent vanadium ion, an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other monomers no+o the cotton fabric. The dependence of grafting on vanadium concentration, pH of the polymerization medium, temperature and duration of grafting, nature and concentration of monomer, and solvent/water ratio was studied. The results indicated that increasing the pentavalent vanadium (Vv) concentration up to 60 mmol/L was accompanied by enhancement in the rate of grafting; the latter was not affected by further increase in Vv concentration. Maximum grafting yield was achieved at pH 2; grafting fell greatly at higher pH. The rate of grafting followed the order: 70° > 60° > 50°C. The graft yield increased significantly by increasing the MMA concentration from 0.5 to 5%. Of the solvents studied, n‐propanol and isopropanol enhanced the grafting rate provided that a solvent/water ratio of 5 : 95 was used; a higher solvent ratio decreased the magnitude of grafting. Other solvents, namely, methanol, ethanol, n‐butanol, and acetone, in any proportion, decreased the rate of grafting. With the monomer used, the graft yield followed the order: methyl methacrylate > methyl acrylate > methacrylic acid > ethyl methacrylate > acrylic acid. Also reported was a tentative mechanism for vinyl‐graft copolymerization onto cotton fabric using cellulose thiocarbonate‐Vv. © 1993 John Wiley & Sons, Inc.
Infrared spectroscopy study of powder celluloses modified by Lewis acids
Authors: Sultankulova A. S. , Sarybaeva R. I. , Afanasev V. A.
Published: April 2003

It is shown that modified powder celluloses distinguish from microcrystal cellulose produced by a hydrolytic method by the presence of the modification of cellulose II and by a low index of crystallinity. © 1994 John Wiley & Sons, Inc.
Branching measurement by analytical TREF: A fully quantitative technique
Authors: Pigeon Michael G. , Rudin Alfred
Published: April 2003

Conversion of analytical TREF data to accurate branching distributions of polyethylene requires a calibration of branching frequency as a function of elution temperature. It has been found that the elution temperature of a semicrystalline polymer such as polyethylene depends on molecular weight, branch content, branch length, and branch clustering. It stands to reason that every polymer will have its own unique relation of branch frequency and elution temperature. Ideally, the polymer would be fractionated by a preparative TREF technique and the fractions analyzed by NMR or IR to determine branch frequency with respect to elution temperature. This method is tedious and time‐consuming. An alternative method is described here to determine the relation between branch frequency and TREF elution temperature and to generate a calibration from analytical TREF data only. A twodetector system is used to simultaneously measure both concentration and branching frequency as a function of elution temperature. Each polymer is analyzed using analytical TREF data alone, eliminating the need for preparative TREF fractionation and NMR analysis of the fractions. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of amidoxime resins based on poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinylbenzene)
Authors: Kabay Nalan , Egawa Hiroaki
Published: April 2003

The poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinylbenzene) beads with macroporous morphology were synthesized by suspension polymerization. The use of dichloroethane as a solvating diluent resulted in copolymer beads having highly porous structures. These have been reacted with hydroxylamine in methanol, which generates amidoxime groups. The precursory resins were readily functionalized within 0.5–1 h. A detailed analysis is made of the pore structure of resins in the anhydrous state including pore size distribution and specific surface area. © 1994 John Wiley & Sons, Inc.
Crystallization kinetics of pure and fiber‐reinforced poly(phenylene sulfide)
Authors: Auer C. , Kalinka G. , Krause Th. , Hinrichsen G.
Published: April 2003

Isothermal DSC investigations on pure as well as glass, carbon, and aramid fibre‐reinforced poly(phenylene sulfide) (PPS) were carried out in order to obtain informations on the crystallization kinetics, that is, the Avrami exponent, constant, half‐time of crystallization, and (final) degree of crystallinity. PPS is a typical representative of semicrystalline polymers with a maximum degree of crystallinity of about 60%. The Avrami exponent reaches values from n = 2.1–2.7 depending on fibre type but independent of crystallization temperature. The system aramid fibre/PPS has a much shorter half‐time of crystallization than the other three systems that could be attributed to the high nucleation effect of the aramid fibre surface to PPS. As a consequence of the high nuclei density a transcrystalline zone is built up around the aramid fibre. The relatively low value of the Avrami constant was discussed and a computer simulation attempt was made to understand the measured value quantitatively. © 1994 John Wiley & Sons, Inc.
Evidence for chemical bond formation between surface treated carbon fibres and high temperature thermoplastics
Authors: Hüttinger K. J. , Krekel G. , Zielke U.
Published: April 2003

The interaction between surface‐treated carbon fibres and high temperature thermoplastics (polyethersulfone and polycarbonate) was studied by measuring the interlaminar shear strength of unidirectionally reinforced composites with a fibre volume content of 60%. The ILSS‐values were correlated with the surface concentration of the acidic functional groups of the carbon fibres, as analysed by temperature programmed desorption and contact angle measurements using basic aqueous solutions (pH ≥ 12). Linear relationships were found with both the amount of carbon dioxide desorbed by decomposition of carboxylic surface groups and the work of adhesion calculated from the measured contact angles. This result could be interpreted as a consequence of acid–base interactions with the basic polymers. However, strongly acidic carboxylic groups are decomposed during processing of the composites. Therefore, the high ILSS‐values can only be explained by chemical bonds being formed with the functional groups of the polymers during decomposition of the carboxylic surface groups. © 1994 John Wiley & Sons, Inc.
Reaction condition effects in the melt preparation of poly(phenylene sulfide) from p‐lodophenyl disulfide
Authors: Fagerburg D. R. , Van Sickle D. E.
Published: April 2003

High melt viscosity poly(phenylene sulfide) (PPS) can be prepared via melt condensation of p‐iodophenyl disulfide analogous to the solution condensation previously reported by other investigators. Depending upon reaction conditions, the material contained varying amounts of gels, whereas under all conditions, anywhere from 1 to 3 mol % disulfide linkages were present. Solution in 1‐chloronaphthalene allowed separation of soluble and gel fractions and also cleaved the disulfide linkages, which allowed better quantitation of the disulfide content than did elemental analysis. Cleavage of the disulfides with 1‐chloronaphthalene was verified via a model reaction. Branching in the preparations was related to the level of iodine in the melt reaction and also the reaction temperature. A branching mechanism is proposed based on model experiments that showed a complex reaction order and an initial rate of branching that was dependent on iodine concentration. © 1994 John Wiley & Sons, Inc.
Design of an extrusion die with a variable choker bar
Authors: Wu Ping‐Yao , Liu Ta‐Jo , Chang Hsu‐Ming
Published: April 2003

A novel approach is proposed to adjust flow nonuniformities caused by production variations from an extrusion die. A mathematical model that is based on the lubrication approximation was developed, and the effect of four types of production variations was examined separately. To each production variation, a specially designed choker bar was constructed and inserted into the extrusion die to correct flow nonuniformities. © 1994 John Wiley & Sons, Inc.
Hydrophilic foams containing corn products for horticultural use
Authors: Cunningham R. L. , Carr M. E. , Bagley E. B. , Gordon S. H. , Greene R. V.
Published: April 2003

Polyurethane foams containing equal amounts of commercial unmodified cornstarch and a polyisocyanate‐terminated polyether exhibit properties suitable for horticultural applications. The use of cornstarch in the foam formulation increased the volume by one‐fourth as compared to the foam without cornstarch. This volume increase represents an economic advantage of 20% savings based on material cost. When cornstarch or corn flour is added to the foam formulation, the foams are more resistant to compressive force. Upon wetting and draining, the foams prepared with no auxiliary blowing agent and containing corn products exhibit higher volumes than do the unfilled foams. Radish seeds planted inside 25 mm cubes of foams began to sprout after 1 day. Early developmental growth for the plants was similar in the control and cornstarch‐filled foams. Spectroscopic analyses of the starch‐containing foams revealed that 60–70% of the cornstarch was metabolized within 4–5 weeks by a microbial consortium. Control polyurethane foams were not affected by the microorganisms tested. © 1994 John Wiley & Sons, Inc.

This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
Natural rubber–HDPE blends with liquid natural rubber as a compatibilizer. I. Thermal and mechanical properties
Authors: Ahmad Sahrim , Abdullah Ibrahim , Sulaiman Che Som , Kohjiya S. , Yoon J. R.
Published: April 2003

The measurement of physical properties of thermoplastic natural rubber (TPNR) of NR–HDPE blends have been made at various compositions of high‐density polyethylene (HDPE). The tensile properties and hardness of TPNR improve significantly with the addition of liquid natural rubber (LNR) to the blend. The degree of cross‐linking also increases with increasing amount of LNR added. The LNR with molecular weight (Mw) of 50,000 and reactive terminals promotes cross‐linking within the rubber phase and grafting of the polyethylene chains onto the rubber matrix system. The maximum stress and strain of the blends measured are about 7.5 MPa and 1000%, respectively. Dynamic mechanical analysis results indicate a single Tg on a tan δ trace at about −50 and −55°C for the two types of blends, respectively. © 1994 John Wiley & Sons, Inc.
Hemolglobin encapsulation in chitosan/calcium alginate beads
Authors: Huguet M. L. , Groboillot A. , Neufeld R. J. , Poncelet D. , Dellacherie E.
Published: April 2003

A mild chitosan/calcium alginate encapsulation process, as applied to encapsulation of hemoglobin, was investigated. The first procedure consisted of adding dropwise a hemoglobin‐containing sodium alginate mixture in a chitosan solution, then hardening the interior of capsules thus formed, in the presence of CaCl2. In the second method, the droplets were directly pulled off in a chitosan–CaCl2 mixture. Both procedures led to beads containing a high concentration in entrapped hemoglobin as more than 90% of the initial concentration (150 g/L) were retained inside the beads provided that the chitosan concentration was great enough. The molecular weight of chitosan (M̄u 245,000 or 390,000) and the pH of its solution (2, 4, or 5.4) had only a slight effect, the best retention being obtained with beads prepared at pH 5.4. The hemoglobin release during the bead storage in water was found to depend on the conditions of their formation and especially on the chitosan molecular weight. The best retention during storage in water was obtained with beads prepared with the high M̄u chitosan solution at pH 2. Considering the total loss in hemoglobin during the bead formation and after 1 month of storage in water, the best results were obtained by preparing the beads in an 8 g/L solution of a 390,000 chitosan at pH 4 (less than 7% of loss with regard to the 150 mg/L initial concentration). © 1994 John Wiley & Sons, Inc.
Interfacial tension of poly(p‐phenylene sulfide) with other polymer melts
Authors: Yoon Pil Joong , White James L.
Published: April 2003

The interfacial tension of poly(p‐phenylene sulfide) (PPS) with various thermoplastics of different compostion and polarity has been carried out using the breaking thread and pendent drop methods. The value of the polyethylene (PE)/PPS interfacial tension is found to be intermediate between PE/polysulfone and PE/polycarbonate. The highest interfacial tension for PPS found in the systems studied was with polyamide‐6 followed by PE. The lowest values were with polysulfone followed by polystyrene. The effects of small additions of polysulfone and polystyrene in PPS on interfacial tension is studied with various thermoplastics. © 1994 John Wiley & Sons, Inc.
Polyacrylonitrile (PAN)‐grafted jute fibres: Some physical and chemical properties and morphology
Authors: Ghosh Premamoy , Ganguly Prasanta K.
Published: April 2003

Grafting of polyacrylonitrile (PAN) on (dewaxed and bleached) jute fibres was done by aqueous polymerization of acrylonitrile (AN) in the presence of the fiber samples employing a sodium periodate (IO4−) and copper sulfate (Cu2+) combination as the initiator. Effect of PAN grafting to different extents on X‐ray crystallinity, tensile properties, thermal behavior, whiteness index, dyeability, light‐fastness rating, and moisture regain properties of the fiber samples were studied and analyzed. Their rot resistance, determined by a standard soil burial test, were also examined and compared. Twenty to thirty percent PAN‐grafting was found to impart a most desirable balance of physical properties including fiber strength and modulus, moisture regain, whiteness index, and light‐fastness rating. PAN grafting also makes the otherwise nonresistant jute fiber significantly rot‐resistant. Morphology of the different fiber samples as studied and compared using scanning electron microscopy indicates that PAN grafting occurs on surfaces and intercellular regions as well as within the lumens of the multicellular jute fibers. © 1994 John Wiley & Sons, Inc.
Microstructure of polyurethane ionomers derivatized with dodecylamine and polyethylene oxide in the hard segment
Authors: Santerre J. P. , Brash J. L.
Published: April 2003

Segmented polyether‐polyurethanes containing sulfonate groups in the hard segment were modified by the grafting of polyethylene oxide and C12 hydrocarbon chains. The grafts were attached via the sulfonate groups. The physical properties of the materials, including stress–strain behavior, thermal behavior, and water uptake were studied. Grafting was found to alter material behavior significantly. Both the alkyl and polyethylene oxide grafts appear to alter the packing of the hard segments in microdomains because the grafted materials, in contrast to their sulfonated precursor, do not exhibit a melting transition. However, the polyethylene oxide chains appear to interact with the hard segments, probably through hydrogen bonding. For the C12 grafted materials, differential scanning calorimetry showed that a third microphase, consisting largely of C12 chains, may be formed by annealing. Stress–strain and water uptake data support these interpretations. The grafted materials were found to absorb more water than the sulfonated precursor. Most of the water taken up by the C12 material appears to be bulk water whereas for the PEO materials the absorbed water behaves as if it is bound. © 1994 John Wiley & Sons, Inc.
Phototackification of polymer blends
Authors: Simmons H. E. , Hertler W. R. , Sauer B. B.
Published: April 2003

A direct single‐layer phototackification scheme is demonstrated making use of chemical amplification and photo‐induced microphase separation in an initially nontacky miscible blend of acid‐labile poly(2‐tetrahydropyranyl methacrylate) and poly(2‐tetrahydropyranyl acrylate), tacky poly(2‐phenylethyl acrylate), and a photoacid generator. The mechanism involves four process: photoacid generation, acid migration, acetal ester cleavage, and phase separation. Thin film in situ IR studies showed the rate of acid migration and acetal ester cleavage to be strongly dependent on the presence of ambient water and polymer matrix (Tg) effects. The rate of phase separation is affected by polymer molecular weight. A number of approaches to minimize humidity sensitivity are discussed. The system has been sensitized to both UV and near‐IR radiation. © 1994 John Wiley & Sons, Inc.
Fast pyrolysis of cellulose with reactive methane gas in a single‐pulse shock tube
Authors: Öztürk Zihni , Merklin Joseph F.
Published: April 2003

A shock tube technique was employed to study the fast pyrolysis of cellulose with methane under conditions of high temperature, high heating rate, short reaction time, and rapid quenching. The effects of temperature, methane atmosphere, and reaction time are investigated. Experiments were carried out at temperatures between 700 and 2200°C in 1% methane (diluted in argon), and comparisons in the yields of major gas products are made with the results obtained in pure argon atmosphere. The total gas yield decreased about 25–30% in methane. The principal gas products—carbon monoxide, carbon dioxide, and acetylene, except ethylene—were significantly decreased in methane as compared to the yields in pure argon. An increase of about 25% in ethylene yield in methane over argon was observed. The onset of the decomposition of cellulose and the evolution of major pyrolysis products were changed with the reaction times, which also affected the amplitude and the distribution of the pyrolysis products. © 1994 John Wiley & Sons, Inc.
Strong buffering characteristics and swelling behavior of cationic copolymers
Authors: Peppas Nikolaos A. , Foster Lisa K.
Published: April 2003

The swelling behavior of crosslinked cationic copolymers of 2‐hydroxyethyl methacrylate with (3‐methacryloylamino propyl) trimethylammonium chloride was investigated in various buffered solutions as a function of ionic strength and pH. The equilibrium degree of swelling increased as the pH decreased or as the cationic group‐containing comonomer in the polymer increased. The water transport in such copolymers was controlled by a non‐Fickian mechanism. These results can be used in the development of physiologically sensitive controlled drug delivery systems. © 1994 John Wiley & Sons, Inc.
Preparation and structure of cross‐linked asymmetric membranes based on polystyrene and divinylbenzene
Authors: Byun H. S. , Burford R. P.
Published: April 2003

Asymmetric polystryene‐based membranes were prepared by photocross‐linking with divinylbenzene (DVB) combined with phase‐inversion steps. The primary variables examined were original polystrene concentration in the membrance casting solution and degree of cross‐linking. The effects of these upon membrane morphology and reverse osmosis performance were determined. At higher DVB concentration, skin was formed at the top due to phase separation and at the bottom due to preferential polymer absorption at the support interface. An attempt was made to increase membrane ductility by incorporating low levels of liquid polybutadiene or styrene‐butadiene block copolymer, but no significant change was measured. © 1994 John Wiley & Sons, Inc.
Interpenetrating hydrogel networks based on gelatin and polyacrylamide: Synthesis, swelling, and drug release analysis
Authors: Ramaraj B. , Radhakrishnan Ganga
Published: April 2003

Interpenetrating hydrogel network has been synthesized from gelatin and polyacrylamide by cross‐linking with their respective cross‐linking agents. The swelling behavior of this Interpenetrating polymer network (IPN) system was analyzed in water and in citric acid‐phosphate buffer solution at various pH. The effect of temperature on swelling behavior of these gels has been analyzed by variation from 25 to 60°C at physiological pH. The drug release behavior of these gels was also analyzed with temperature variation at physiological pH. © 1994 John Wiley & Sons, Inc.
Preparation and physical properties of polyurethane modified with poly(4,4′‐diphenylsulfone terephthalamide)
Authors: Wang Huei‐Hsiung , Shiao Kai‐Rhen
Published: April 2003

Three conventional polyurethane (PU) elastomers were blended physically with various ratios of high molecular weight of poly(4,4′‐diphenylsulfone terephthalamide) (PSA) to form 12 PU/PSA polyblends in order to modify their physical properties. Also three new polyurethanes were synthesized with a low‐molecular‐weight PSA prepolymer as a hydrogen donor for chain extending. From dynamic properties, it showed that both the blends and the new polyurethanes (or polyurethane‐ureas) exhibited a glass transition temperature (Tg) below 0°C and had a higher modulus E′ than those of the conventional PU. Based on the analysis of X‐ray diffraction of the conventional and the new PU, it was shown that the degree of stress‐induced crystallization was dependent on the segmental composition of the soft and hard segments and also the degree of its stretching. On the morphological observation, it was revealed that both the blends and the new polyurethanes were in a dispersed phase structure, although new PU exhibited a better compatible state. For tensile properties, it was found that both tensile strength and elongation of the new polyurethanes were better than those of the blends and conventional PU. © 1994 John Wiley & Sons, Inc.
Comb‐type polymers and their interaction with wax crystals in waxy hydrocarbon fluids: Wide‐angle X‐ray diffraction studies
Authors: Chatterjee Alok K. , Phatak Sadanand D. , Murthy Pappu S. , Joshi Girish C.
Published: April 2003

We report the results of our wide‐angle X‐ray diffraction (WAXD) studies on the interaction of various comb‐type acrylate polymers, synthesized in our laboratories, with waxes crystallizing out below the cloud point of an indigenously available high‐wax commercial diesel fuel. These copolymers were made from monomers from C8 to C24 carbon numbers, which covers the average carbon number, viz., C16–C22, of most of the commercial diesel fuels. The influence of the pendant chain on the crystallization process of n‐alkanes below the cloud point of the fuel has been assessed, for the first time, to the best of our knowledge, by this method. Wax crystals, isolated by this procedure, are basically hexagonal, with some features relating to mal‐structures and have similarity to the comb‐type polymers with more than eight carbon atoms in their side chains. Effective pour‐point depressants showed distinctive changes in the diffraction pattern of the low‐angle, i.e., larger than van der Waals (LVDW) peaks, usually a general shift to higher angles, and in some cases, a distinct split. © 1994 John Wiley & Sons, Inc.