bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of cellulose accessibility by differential scanning calorimetry
Authors: Bertran Maria Silvia , Dale Bruce E.
Published: April 2003

The thermal behavior of various cellulose samples with different degrees of crystallinity as measured by X‐ray diffraction techniques was studied with a differential scanning calorimeter (DSC). The broad endothermic peak which appears between 110 and 160°C is due to loss of absorbed (bound) water. Since a direct relationship was observed between the area of this peak and the crystallinity of the sample, a new procedure for estimating cellulose accessibility (which is related to crystallinity) was proposed and developed. DSC curves obtained on cellulose samples preconditioned at certain constant relative humidities were used to determine sample accessibilities by the proposed method. The accessibility values obtained by DSC showed excellent agreement with crystallinity values determined by more traditional techniques. Completely amorphous cellulose was obtained by anhydrous deacetylation of cellulose triacetate and was used as the standard amorphous cellulose material.
Dynamic mechanical properties of thermoplastic elastomers from polypropylene–natural rubber blend
Authors: Kuriakose Baby , De S. K. , Bhagawan S. S. , Sivaramkrishnan R. , Athithan S. K.
Published: April 2003

The dynamic mechanical properties of thermoplastic elastomers from polypropylene natural rubber blends have been evaluated with special reference to the effect of blend ratio and extent of dynamic crosslinking of the elastomer phase. The effects of HAF black and silica fillers have also been studied. It has been found that increasing the proportion of elastomer phase reduced the storage modulus and increased the loss tangent values of the blends. The effect of dynamic crosslinking was found to be more prominent in blends containing higher proportion of elastomer phase. The improvement in storage modulus and decrease in loss tangent values were quite remarkable with increase in extent of crosslinking in these blends. The 70:30 NR:PP blend was found to exist as a two‐phase system, both the components forming continuous phases of the blend.
Qualitative and quantitative analysis of methyl acrylate or methyl methacrylate of acrylonitrile fibers by pyrolysis gas chromatography
Authors: Saǧlam Mehmet
Published: April 2003

Degradation gases evolved from methyl acrylate or methyl methacrylate of acrylonitrile fibers were analyzed by pyrolysis gas chromatography. For determining polymer composition, optimum pyrolysis conditions were determined and calibration was accomplished by using acrylonitrile–methylacrylate and acrylonitrile–methyl methacrylate model copolymers. Out of the 23 samples examined, 10 were found to contain methyl acrylate and five methyl methacrylate comonomers, in the range of 3.5–8.0%. The reproducibility of the method was good, the coefficient of variations was ±2% for methyl acrylate and ±2.5% for methyl methacrylate. Compositions were in agreement with those determined by other methods.
Structure and properties of dynamically cured EPDM/PP blends
Authors: Ha Chang Sik , Ihm Dong Joon , Kim Sung Chul
Published: April 2003

The structure and properties of polyolefin blends of ethylene–propylene–diene terpolymer (EPDM) and polypropylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured with PP under shear with dicumyl peroxide (DCP) at different shear conditions (blend–cure). Blends were also prepared for comparison from EPDM which were dynamically cured in the absence of PP and blended later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastic composition were studied. In blend–cure, the melt viscosity increased with increasing DCP concentration in blends of 75% EPDM and 25% PP, but it decreased with increasing DCP concentration in blends of 75% PP and 25% EPDM. In cure–blend, however, the melt viscosity increased with increasing DCP concentration for all compositions. The melt viscosity decreased with increasing intensity of the shear mixing presumably due to the formation of the smaller segregated microdomain of the crosslinked EPDM gels in both blend–cure and cure–blend materials. The crystallization rate was higher in EPDM/PP blends than in PP homopolymer. The crystallization rates for various blending conditions were also compared.
Synthesis, characterization, and properties in aqueous solution of poly(starch‐g‐[1‐amido‐ethylene)‐co‐(sodium 1‐(2‐methylprop‐2N‐yl‐1‐sulfonate)amidoethylene)])
Authors: Meister John J. , Patil Damodar R. , Jewell Margaret C. , Krohn Kyle
Published: April 2003

Graft terpolymers of starch, 2‐propenamide, and sodium 2‐methyl‐3‐imino‐4‐oxohex‐5‐ene‐1‐sulfonate can be made by cerium‐IV‐initiated, free‐radical polymerization of an aqueous monomer mixture on starch. Synthesis is conducted on aqueous, gelled, lintnerized potato starch at 30°C under a nitrogen atmosphere. Yields range from 50 to 100 wt % and products contain 9–52 wt % starch, 1–51 wt % 1‐acidoethylene, and 18–65 wt % sodium 1‐(2‐methylprop‐2N‐yl‐1‐sulfonate)amidoethylene. Repeat unit ratios in the reaction product approximate monomer ratios in the reaction mixture. Fraction of starch grafted in a reaction decreases as the mole fraction of sulfonated monomer in the reaction mixture increases. No proof has been found for grafting of synthetic side chains to starch in monomer mixtures containing only sulfonated monomer. Starch graft copolymers with side chains composed of 1‐amidoethylene units and a sulfonated 1‐amidoethylene unit derivative, 1‐(sodium[2‐methylprop‐2N‐yl‐1‐sulfonate])amidoethylene, are water‐soluble, thickening agents. The rheology of solutions of these copolymers is a function of the ratio of nonsulfonated to sulfonated repeat units in the synthetic chains of the molecule. Aqueous solutions of these products are shear thinning and have power law exponents which decrease 1) with increasing product concentration or 2) as the nonsulfonated to sulfonated repeat unit ratio moves toward 3/1. Limiting viscosity number of product in water decreases with increasing shear rate of measurement or with increasing salt concentration of the solvent. Formulas are derived from the theories of Kirkwood and Flory which show that for copolymers with constant molecular weight, expansion coefficient, and limiting viscosity number increase as the fraction of sulfonate‐containing repeat units in the chain increase. This theoretical requirement and the limiting viscosity data for groups of samples prepared under identical synthesis conditions are used to show that molecular weight of the graft copolymer decreases as the fraction of sulfonated repeat units in the copolymer increases. Screen factor measurements show product solutions to be viscoelastic.
Thermal effects in poly(hexamethylene adipamide) and polyoxymethylene at high hydrostatic pressures
Authors: Rodriguez E. L. , Filisko F. E.
Published: April 2003

The temperature changes as a result of rapid hydrostatic pressure applications are reported for poly(hexamethylene adipamide) (nylon 66) and poly(oxymethylene) (POM) in the reference temperature range from 298 to 423 K and in the pressure range from 13.8 to 200 MN/m2. The adiabatic temperature changes were found to be a function of pressure and temperature. A curve fitting analysis showed that the empirical curve (∂T/∂P) = ab(ΔP)b−1 described the experimental thermoelastic coefficients obtained from the experiments. The data were analyzed by determining the predicted thermoelastic coefficients derived from the Thomson equation (∂T/∂P) = αT0/ρCp. The experimental and predicted Grüneisen parameter γT were also determined. The relationship between the thermal effects and the chain molecular motion is discussed by including dynamic mechanical analysis and DSC measurements for the nylon 66 and POM samples.
In vitro chemical degradation of poly(glycolic acid) pellets and fibers
Authors: Ginde Rajiv M. , Gupta Rakesh K.
Published: April 2003

The influence of macroscopic dimensions, heat treatment, and polymer morphology on the chemical degradation of poly(glycolic acid) (PGA) fibers and pellets was examined in media of different pH values by monitoring the sample mass, dimensions, crystallinity, mechanical strength, and surface character. The degradation was found to be chemically controlled and independent of fiber size. The rate was an order of magnitude faster in alkaline vs. acidic media. In general, the pellets degraded faster than fibers, and while the latter showed little surface deterioration, scanning electron photomicrographs of the pellets revealed considerable surface degradation with circumferential microcracks progressing into longitudinal cracks with increasing immersion times and pH. Concomitantly, DSC measurements showed a steady increase in crystallinity for both fibers and pellets. The fiber tensile strength decline was independent of diameter and more drastic in alkaline media. Additionally, the heat‐treated fiber was always stronger than the non‐heat‐treated one. It is concluded that crystallinity and polymer chain orientation, in addition to immersion media, influence PGA degradation. Also, the loss in strength results from chain scission in the amorphous regions while mass loss occurs when polymer chains become small enough to be soluble. These different variables offer a means of modifying PGA fiber tensile properties.
Curing behavior of unsaturated polyester resin with mixed initiators
Authors: Han Chang Dae , Lee Dai‐Soo
Published: April 2003

The curing behavior of unsaturated polyester resin with mixed initiators was investigated both experimentally and theoretically. For the experimental investigation, we used various combinations of low and high‐temperature initiators to cure a general‐purpose unsaturated polyester resin and determined the rate of cure and the degree of cure, using differential scanning calorimetry and infrared spectroscopy. For the theoretical investigation, we used the mechanistic kinetic model described in our previous paper. It has been demonstrated that the mechanistic model is very useful for predicting the curing behaviour of unsaturated polyester resin with mixed initiators, using information on the rate constants of the individual initiators and the concentration of the initiator. Such an approach will help reduce, if not eliminating completely, the number of tedious and time‐consuming curing experiments that would otherwise have to be performed.
Binding of heavy metal ions by chemically modified woods
Authors: Morita Mitsuhiro , Higuchi Mitsuo , Sakata Isao
Published: April 2003

Three chemically modified woods were prepared and used for the binding of heavy metal ions. Wood–polythylenimine composite (wood–PEI) was found to be effective for the adsorption of heavy metal ions such as Hg2+, Cu2+, and other metal ions which tend to form stable ammine complexes. Adsorption of metal ions on a wood–PEI derivative containing dithiocarbamate group (DTC–wood) was higher than that by wood–PEI. Especially, the reactivity of DTC–wood with Hg2+ was quite high and the binding capacity of about 5 mmol/g was easily attainable. The rate of adsorption on these wood‐based adsorbents was very high, and adsorption of about 70% of total binding capacity was accomplished in the first 1 h. This may be due to a highly porous structure and a hydrophilic nature of the wood which constitutes the skeleton of the adsorbents. Amidoximated wood (AO–wood) prepared by the reaction of cyanoethylated wood with hydroxylamine showed selective adsorptivity for uranium in sea water. More than 53% of uranium in the sea water used was adsorbed by the AO–wood.
Crystalline memory on polycarbonate
Authors: Filippo Giuseppe V. Di , González María E. , Gasiba María T. , Müller Alejandro V.
Published: April 2003

A significant reduction on the time for thermal crystallization of Bisphenol‐A polycarbonate has been achieved by means of a previous crystallization step of the polymer in acetone, followed by a capillary extrusion processing at temperatures above its melting range (230–280°C). The crystallinity of PC was corroborated qualitatively by means of WAXS and quantitatively by means of DSC. The acetone‐crystallized polymer showed higher values of dynamic viscosity than its amorphous counterpart. Such difference decreased with the increase of the test temperature and disappeared at 280°C. The degree of crystallinity of thermally crystallized PC increased with the decrease of the capillary extrusion temperature of the acetone‐crystallized material. It is inferred that the time–temperature‐dependent long range molecular diffusion necessary for the total melting of the crystal fractions could not take place entirely for the short times employed (≈ 4 min), allowing the extruded polymer to behave as a self‐nucleated material.
Aging of EPDM rubber
Authors: Deuri A. Saha , Bhowmick Anil K.
Published: April 2003

The effect of oxidative and thermal aging of EPDM raw rubber and rubber vulcanizate on gelation, network structure, and techical properties has been studied over a wide range of temperatures and times of aging. Three grades of EPDM having different types of diene have been considered. The kinetics of aging of both raw rubber and vulcanizates has also been reported.

Different network structures have been produced due to different reactivity of temonomers. Cross‐link density, cross‐link efficiency, polysulfidic linkage, zinc sulfide sulfur, combined sulfur, free sulfur, and sulfur inefficiency change with aging time and temperature. The number of polysulfidic cross‐links decreases continuously with increase in time or temperature of aging. There is no definite trend in other structural features. It is quite evident that postcuring reactions as well as destruction of cross‐links are taking place in the aging process. The predominance of the former or latter depends on the structure of the diene.

Tensile and tear strength of the compounds decreases or increases with time or temperature of aging. At high temperature, it always decreases with time. Changes in these properties can be approximately correlated with changes in structure only at high temperature. At lower temperature, relations between network structure and technical properties are complicated owing to the competing reactions discussed above. In general, retention of properties of ENB‐EPDM vulcanizate is the best. The properties after aging do not exclusively depend on the network structure, nature of cross‐link, rank of sulfur, or pendant or cyclic sulfide. The backbone structure is important in all these cases. Changes are less drastic on aging in nitrogen, but a similar trend is found. Raw EPDM rubber forms a gel, which increases with temperature of aging. The activation energy for gelation has been found to be 98 kJ/mol, similar to the oxidation of diene‐containing rubbers.

The activation energy for desulfurization of various grades of EPDM vulcanizates is 60–85 kJ/mol. The activation energy for fracture calculated from aging data is, however, 30–36 kJ/mol from tensile measurement and 32–46 kJ/mol from tear strength measurement.
Selective permeation of carbon dioxide through synthetic polymer membranes having pyridine moiety as a fixed carrier
Authors: Yoshikawa Masakazu , Ezaki Tomohiko , Sanui Kohei , Ogata Naoya
Published: April 2003

Sorption and permeation of CO2 were investigated by using synthetic polymer membranes having pyridine moiety or pyridine–Cu(II) complex group as a fixed carrier. The solubility data for CO2 were interpreted by the dual sorption model, Henry's law plus Langmuir‐type adsorption. The permeation results of CO2 through the present membranes containing pyridine moiety were analyzed in terms of the partial immobilization model, while the solubilities and permeablities of O2 and N2 obeyed Henry's law. Permselectivity of the present membrane for CO2 was achieved. These results were explained by the acid‐base interaction between CO2 molecules and fixed carrier in the present membrane.
Thermal stabilization of polyacrylonitrile fibers
Authors: Ko Tse‐Hao , Ting Hsing‐Yie , Lin Chung‐Hua
Published: April 2003

Polyacrylonitrile (PAN) fibers pretreated with potassium permanganate have reduced the activation energy of cyclization and the oxidation time, and also improved the properties of the resultant carbon fibers. The activation energy of cyclization is reduced to 24 ± 1 kcal/mol from 30 ± 3 kcal/mol and the tensile strength of the carbon fibers increases by about 20−40%. The method of measuring the “aromatization index” (AI) value is modified and is recommended in checking the oxidation process. All fully stabilized PAN fibers have almost the same AI value. However, the oxidation time is decreases by 30 min when oxidation temperature is raised by 10°C.
Studies on process variables for natural fiber composites—effect of polyesteramide polyol as interfacial agent
Authors: Pal S. K. , Mukhopadhyay D. , Sanyal S. K. , Mukherjea R. N.
Published: April 2003

A systematic study of the process variables for polyester composites based on different natural fibers like jute, sisal, ramie, and pineapple has been made with a view to determine the most suitable processing conditions for such composites. Effect of polyesteramide polyol (PEAP) as interfacial agent in such composites has also been discussed. Fracture modes of jute/polyester (JP) composite sample having different fiber volume fractions have been examined by scanning electron microscope (SEM). Fracture surfaces of untreated and PEAP‐treated JP composite samples have been examined in SEM, both before and after 72 h immersion in boiling water, to study the nature of interfacial bonding on fiber treatment with PEAP. A qualitative improvement in bonding in case of PEAP‐treated JP composites is evident from SEM photomicrographs. This is also supported by physicomechanical properties of the composite samples.
Solution properties of poly(thiocarbonates)
Authors: Gargallo Ligia , Soto Elia , Tagle Luis H. , Radić Deodato
Published: April 2003

Poly(thiocarbonates) with alkyl side chains have been prepared, and the solution properties of these polymers were studied in different solvents. Comparison with other poly(thiocarbonate) analogues and poly(carbonates) shows that the conformational parameter (Kθ) and rigidity factor increase as the volume of the side chain increases. The effect of the side‐chain structure on the solution properties is analyzed.
Grafting of acrylamide onto guar gum using KMNO4/oxalic acid redox system
Authors: Bajpai U. D. N. , Rai Sandeep
Published: April 2003

The grafting of acrylamide onto guar gum in aqueous medium initiated by KMnO4/oxalic acid redox system has been studied gravimetrically at the temperature 35 ± 0.2°C. The effect of redox components, acrylamide concentration and quantity of guar gum has been studied in terms of percentage and efficiency of grafting. A plausible mechanism of grafting and a suitable rate expression has been suggested. The rate of grafting was found to increase with increase in temperature and concentrations of redox components and acrylamide, but, at high concentration of guar gum, the rate was found to decrease.
Modeling of asymmetric membrane formation. II. The effects of surface boundary conditions
Authors: Yilmaz L. , McHugh A. J.
Published: April 2003

An analysis is carried out to evaluate the effects of alternate surface boundary conditions on the predictions of our previously developed (Part I) pseudobinary diffusion model for membrane formation by the phase inversion process. Attention is addressed to a comparison of concentration profiles in the quenched film for a constant flux interface (CF) condition and a mass transfer rate (MT) interface condition. A numerical algorithm is developed to handle the MT condition based on an explicit, finite difference marching method. Comparison of concentration profiles with those obtained earlier for the CF boundary condition show that since results for both cases are very similar, either condition can be used in concentration profile calculations. Changes in bath conditions will mainly affect membrane formation through the changed solvent/nonsolvent flux ratio during quenching.
Study on rough‐surface biaxially oriented polypropylene film. I. Formation of β‐form crystals in sheet cast with T‐die extruder
Authors: Fujiyama Mitsuyoshi , Kawamura Yoshimasa , Wakino Tetsuo , Okamoto Tomomi
Published: April 2003

Sheets were cast by extruding polypropylenes (PP) which contained γ‐quinacridone, a β‐crystal nucleator, at levels of 0–10 ppm using a 30 mm ϕ extruder with a T‐die at extrusion temperatures of 200–260°C and chill roll temperatures of 30–90°C. The influences of raw resin characteristics such as γ‐quinacridone content and MFI of the base PP and casting conditions such as extrusion temperature and chill roll temperature on the amount of β‐crystals formed in the sheet were studied. The amount of the β‐crystals formed was larger as the γ‐quinacridone content was higher and the extrusion temperature was lower and almost independent of the chill roll temperature. As for the influence of MFI of the base PP, the amount of the β‐crystals formed was maximum at MFI ≑ 8 dg/min.
Effects of film history on gas transport in a fluorinated aromatic polyimide
Authors: Moe M. , Koros W. J. , Hoehn H. H. , Husk G. R.
Published: April 2003

The effects of film formation procedures on transport properties are reported for a rigid‐chained, fluorinated, aromatic polyimide. Residual dimethylacetamide (DMAC) solvent present in films formed under certain casting protocols produces complexities in the permeation behavior of helium and carbon dioxide. Specifically, helium permeabilities are lower, while those of carbon dioxide are higher, in a film containing 8 wt% residual DMAC than in an annealed film containing < 1 wt% DMAC. Significant differences in transport properties are also observed between films prepared using two different casting techniques. These differences appear to be due to differences in organization of chain segments within films. The results of this study emphasize the considerable care needed in formation and postformation processing of these materials to ensure optimum flux/selectivity properties in such applications.
Water sorption kinetics in poly(aryl ether ether ketone)
Authors: Mensitieri G. , Apicella A. , Kenny J. M. , Nicolais L.
Published: April 2003

The kinetics of diffusion of water from different activity vapors and liquid phase have been investigated in glassy amorphous poly(aryl ether ether ketcne) (PEEK) films at the temperature of 60°C and in glassy semicrystalline PEEK sheets at different temperatures, respectively. In the case of the amorphous PEEK films (250 μm thick) the data at low activity levels were interpreted by means of a purely Fickian mechanism. At higher activity levels the material has shown the presence of a relaxation process; in this case the data have been interpreted using a model proposed by Berens and Hopfenberg. Equilibrium sorption isotherm is also reported. Liquid water sorption in semicrystalline (30%) PEEK sheets (2 mm thick) has been determined to follow the classical Fickian mechanism. The water uptake values obtained for both amorphous and semicrystalline PEEK, confirm the good moisture and liquid water resistance of this kind of high performance thermoplastic polymer.
Structural changes and molecular motion of polyacrylonitrile fibers during pyrolysis
Authors: Ko Tse‐Hao , Lin Chung‐Hua , Ting Hsing‐Yie
Published: April 2003

The stabilization process of polyacrylonitrile (PAN) fiber is necessary to develop high‐performance carbon fiber. This work is concerned with studies of the activation energy of PAN fibers during the stabilization process. A wide‐angle X‐ray diffractometer combined with a fiber specimen holder for heating was used to measure the activation energy of crystal transition Ec. Ec is almost the same as the activation energy of the cyclization reaction E which is measured by a differential thermal analysis (DTA). The variation of crystal size in PAN fiber and a model of the ladder polymer in stabilized fiber transformed from acrylontrile (AN) units of PAN fiber are discussed also. The crystal size of PAN fiber increases when the thermal treatment temperature is raised. When exposed to temperatures above the crystal degradation temperature Td, the molecular rods of PAN fiber are destroyed completely, and ladder polymer is formed in the ordered phase of the original PAN fiber. The transformation of ladder polymer is initiated in the disordered phase, and then at the boundaries of the ordered phase.
A methodology for characterizing reactive coatings: Time–temperature–transformation (TTT) analysis of the competition between cure, evaporation, and thermal degradation for an epoxy‐phenolic system
Authors: Gan S. , Gillham J. K. , Prime R. B.
Published: April 2003

A methodology, in terms of a macroscopic isothermal time–temperature–transformation (TTT) diagram, is presented for characterizing the changes that occur isothermally in a reactive thermosetting system in which evaporation, cure, and thermal degradation occur. Iso‐weight loss contours show the progress of the loss of volatile material (mostly solvent). The gelation contour corresponds to the macroscopic viscosity rising to a definite level. The vitrification contour corresponds to the glass transition temperature (Tg) rising to the temperature of cure (Tcure). Iso‐Tg contours show the progress of cure in terms of the easily measured Tg (rather than chemical conversion). The iso‐Tg contours also show the influence of thermal degradation competing with cure. Degradation is responsible for difficulties in assigning the glass transition temperature of the fully cured material (i.e., Tg∞).
High strength and high toughness aromatic polyamide fiber. I. Preparation and properties of block poly(p‐phenylene and 4,4′‐diphenyl ether terephthalamide) fiber
Authors: Goto Tomoko , Maeda Matsuo , Hibi Sadao
Published: April 2003

High strength and high toughness organic fibers can be prepared by molecular design of a suitable block copolymer with mixed segment of rigid and flexible molecular chains. In this paper, the synthesis of fiber forming high molecular weight block copolymer of poly(p‐phenylene terephtalamide) (PPTA) and poly(4,4′‐diphenyl ether terephthalamide) (DPETA) was studied by the low temperature solution polycondensation method. The high molecular weight block copolymer could be obtained in the mixed solution of 1,3‐dimethyl1‐2‐imidazolidone (DMI) and N,N′‐dimethyl acetamide (DMAc) in the presence of triethylamine. The copolymer structures were characterized by elemental analysis and IR spectra. The thermal stability of the block copolymer was better than that of PPTA homopolymer and the ordered copolymer. The wet spinning of the block copolymer was performed using the reaction solution as the spinning dope. The maximum tensile strength and elongation were observed for the filament containing 50% PPTA. The block copolymer had high strength and high Yound's modulus but had a low elongation compared with the ordered copolymer.
Modeling of chemorheology of thermoset cure by modified WLF equation
Authors: Mijovic Jovan , Lee Chee Hung
Published: April 2003

An analysis of chemorheology of cure of a formulation composed of diglycidyl ether of bisphenol‐A (DGEBA) type epoxy resin and a mixture of aromatic amines was performed. A series of kinetic and rheological tests were run, and the experimentally obtained results were checked against the proposed model. A modified form of the classical Williams–Landel–Ferry (WLF) equation was used to model the chemorheology of the formulation. To arrive at the appropriate form of the modified WLF equation, expressions were developed for (i) the cure kinetics, (ii) the glass transition temperature as a function of the degree of cure, and (iii) the changes in parameters C1 and C2 as a function of temperature. By using these correlations in conjunction with the WLF equation, good agreement between predicted and experimental findings was observed.
Effects of silane coupling agents on mica‐filled styrene‐butadiene rubber
Authors: Debnath Shankar , De Sadhan K. , Khastgir Dipak
Published: April 2003

The effects of silane coupling agents on styrene‐butadiene rubber (SBR)‐mica composites have been studied with special reference to the technical properties and polymer‐filler interaction. Silane‐treated mica improves polymer‐filler interaction, which subsequently enhances the tensile and other technically important mechanical properties. Failure surfaces of tensile, tear, and wear specimens have been examined under scanning electron microscope (SEM) and the fractographs have been correlated with the strength and failure mode of the composites.
Melt rheological properties of polypropylene–wood flour composites
Authors: Maiti S. N. , Hassan M. R.
Published: April 2003

This article presents study of melt rheological properties of composites of polypropylene (i‐PP) filled with wood flour (WF), at filler concentrations of 3–20 wt%. Results illustrate the effects of (i) filler concentration and (ii) shear stress or shear rates on melt viscosity and melt elasticity properties of the composites. Incorporation of WF intoi‐PP results in an increase of its melt viscosity and a decrease of melt elasticity such as die swell and first normal stress differences; these properties, however, depend on filler concentration. Processing temperature of the filledi‐PP increases as compared to the nonfilled polymer.
Chiroptical filters from aqueous (hydroxypropyl) cellulose liquid crystals
Authors: Charlet Gérard , Gray Derek
Published: April 2003

An experimental procedure has been designed for the preparation of aqueous mesophases of (hydroxypropyl)cellulose (HPC) exhibiting a stable low turbidity Sandwich chiroptical filters have been made from these right‐handed cholesteric liquid crystals confined between two parallel glass plates. Their optical properties, studied with new circular polarizers prepared from oriented polyethylene films, depend on the mesophase thickness. Thin filters (liquid crystal thickness ≤ 200 μm) reflect selectively up to 36% of normal incident light (i.e., 72% of the right‐handed circularly polarized component) in a very narrow wavelength band (bandwidth ≤ 10 nm). An increase of the reflected intensity is observed at higher sample thickness, although it is accompanied by an increasing loss of selectivity of the filter toward circularly polarized light. However, a range of thickness exists where both selectivity and reflectivity are close to their optimum values. The availability, low cost, and UV resistance of (hydroxypropyl)cellulose make HPC–water liquid crystals attractive for optical applications.
Photolithography of polytetrafluoroethylene for adhesion
Authors: Rye R. R. , Martinez R. J.
Published: April 2003

Irradiation of polytetrafluoroethylene (PTFE) with Mg(Kα) X‐rays is shown to protect the surface against the chemical etching steps used to prepare PTFE for adhesion. Preirradiated etched samples of PTFE have adhesion strengths to epoxies of less than 3% of that for nonirradiated etched samples. The major portion of this decrease in adhesion strength occurs for X‐ray exposures of less than 10 min and failure in every case occurs in PTFE and not in the bonded transition region. XPS measurements (20 Å sampling depth) show little difference in F content between irradiated and nonirradiated samples, but thermal desorption shows increasing short chain fluorocarbon desorption with irradiation time. These results are consistent with previous studies showing that irradiation produces free radicals that lead to branching and/or crosslinking, and a surface rich in low molecular weight fluorocarbons. The crosslinked surface is resistant to deep (10,000 Å) chemical attack and rich in short chain fluorocarbons; both effects are expected to lead to weak adhesive bonding.
Properties of gels obtained by freezing/thawing of poly(vinyl alcohol)/water/dimethyl sulfoxide solutions
Authors: Yamaura Kazuo , Itoh Masayasu , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

Melting points of poly(vinyl alcohol) (PVA) gels obtained by repeated freezing/thawing cycles of the solutions in mixed solvents of water and dimethyl sulfoxide (DMSO) were measured. PVA solutions in 1–30 and 90 vol % DMSO froze at −40°C. The melting point of a gel increased with an increase in freezing/thawing cycles for all the solutions frozen and with an increase in freezing time in 10–30 vol % DMSO. The solutions in 1–5 vol % DMSO gelled even at very low polymer concentration of 1.0 g/dL by repeated freezing/thawing. The melting point of all the gels with a 5% polymer concentration reached ca. 73°C after 14 freezing/thawing cycles except for the gels in 90 vol % DMSO. However, the melting point of the gels with the same polymer concentration prepared at −40°C using an unfrozen mixed solvent in 60 vol % DMSO was ca. 77°C and the largest. The maximum apparent enthalpy of fusion of the gels prepared by repeated freezing/thawing was ca. 40 kcal/mol. The gels in 90 vol % DMSO were transparent independent of cycles where as those in 1–80 vol % DMSO were opaque. The degree of opaqueness increased with decreasing DMSO content.
Comparative study of various methods for thermal degradation of poly[3‐dimethyl(methacryloyloxyethyl) ammonium propanesulfonate]
Authors: Lee Wen‐Fu
Published: April 2003

The comparative study of thermal degradation for poly[3‐dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] [poly(DMAPS)] was studied by various methods under different conditions. The reaction order, the activation energy, and the preexponential factor were evaluated from thermal gravimetric curves. The activation energy and the preexponential factor increase with increasing heating rate in a nitrogen atmosphere and decrease with increasing heating rate in air. The activation energy is higher in an air atmosphere at lower heating rates (5, 10, 20°C/min), for any of the methods used.
Thermogravimetric analysis of cellulose: Effect of the molecular weight on thermal decomposition
Authors: Calahorra M. E. , Cortázar M. , Eguiazábal J. I. , Guzmán G. M.
Published: April 2003

Cellulose fractions of different molecular weights were subjected to dynamic thermogravimetric analysis in a nitrogen atmosphere. From the experimental data, activation energies and reaction orders were obtained following the Freeman–Carroll and Broido methods. The thermal stabilities of the samples were estimated taking into account the values of Ti, Tmax, and Ea. The results show that thermal stability increases as the molecular weight increases. It was also found that the cellulose pyrolisis process cannot be described as having a single value of Ea over the entire pyrolisis range. The dependence of Ea. The dependence of Ea on molecular weight is also discussed.
A study on the mechanism of the curing of LARC–TPI high temperature adhesive
Authors: Chang Shu‐Ying , Huang Samuel J. , Johnson Julian F.
Published: April 2003

A study of the changes in a LARC–TPI adhesive during a three‐stage thermal curing process has been conducted. The multistage curing conditions followed commonly used industrial curing specifications. Using thermogravimetric analysis plus gas chromatography plus mass spectrometry, the gasses involved in the curing were identified. Water analysis was performed by two separate techniques and supplementary information gathered using Fourier transform infrared spectroscopy. These analytical studies permitted determination of the degree of cure at each stage and to determine whether any degradation is taking place under curing condition.
Functionalized polymers derived from the reaction of polymaleic anhydride with amines and alcohols
Authors: Tsiourvas D. , Paleos C. M. , Dais Photis
Published: April 2003

In the present study the application of polymaleic anhydride as a reactive polymer is illustrated in its reactions with didodecylamine, diphenylamine, and dodeecanol. These polymers consisting of lipophilic segments (originating from the long aliphatic chains) or of the mesomorphic diphenyl moiety coupled with the polar carboxylic or carboxylate group can in principle exhibit mesomorphism in the melt and aggregate in dispersion. Of these derivatives didodecyl derivative froms mesomorphic‐like structure in the melt, dodecanol monoester derivative dissolves freely in water whereas the sodium salts of the polymers disperse in water due to the presence of distinct polar and lipophilic moieties in their molecules.
The thermal stability of poly(aryl‐ether–ether‐ketone) as assessed by thermogravimetry
Authors: Day M. , Cooney J. D. , Wiles D. M.
Published: April 2003

The high temperature engineering thermoplastic poly(aryl‐ether–ether‐ketone) (PEEK) has been subjected to dynamic and isothermal thermogravimetry in both nitrogen and air. The dynamic data have been analyzed using both the Kissinger peak maximum technique and an isoconversional procedure developed by Flynn. These techniques gave apparent global activation energies of 223.5 and 235.7 kJ/mol, respectively, for the degradation of PEEK in nitrogen, in good agreement with the value of 219.7 determined from the isothermal experiments. The thermal stability of PEEK in air is substantially less than in nitrogen, and the decomposition mechanism is more complex. The global apparent activation energies for the weight loss in air were found to be 116.9 and 159.5 kJ/mol from dynamic slow heat rate data and isothermal data, respectively. The data obtained from fast heating rate experiments in air were found to be misleading, suggesting caution in the use of “commercial” software packages for lifetime estimates under these conditions, especially where oxidative processes may be occurring.
Selective permeation through hydrophobic–hydrophilic membranes
Authors: Park Jun Seo , Ruckenstein Eli
Published: April 2003

Hydrophobic–hydrophilic composite membranes, containing polystyrene as the dispersed phase and polyacrylamide as the continuous phase, have been prepared by the concentrated emulsion polymerization method. They are highly absorptive for methyl chloride, benzene, and toluene, but poorly absorptive for cyclohexane. The absorption from toluene–cyclohexane mixtures was found to increse with increasing temperature and toluene concentration and to decrease with increasing fraction of polyacrylamide in the composite. The absorption is controlled by diffusion. The permeation rate through the membrane, which was determined by the pervaporation method, exhibits similar trends with respect to temperature, concentration, and fraction of polyacrylamide as absorption does. Higher permeation was obtained by increasing the temperature and by increasing the toluene concentration or by decreasing the fraction of polyacrylamide. The selectivity which was in the range of 4–8 varies inversely with the permeation rate through the membrane which was in the range of 2 × 103−1.0 × 104 g/m2 h.
Molecular weight advancement of poly(ethylene ether carbonate) polyols
Authors: Harris Robert F.
Published: April 2003

Poly(ethylene ether carbonate) polyols have been prepared from ethylene carbonate and monoethylene glycol (MEG) or diethylene glycol (DEG) using sodium stannate trihydrate as catalyst. When these polyols (catalyst removed) are heated to elevated temperatures (< 180°C) at reduced Pressures, volatile impurities are removed, as distillate, molecular weight builds in a controllable manner. This is thought to be a transesterification process in which OC(O)CH2CH2OCH2CH2OH end groups on one molecule react with carbonate moieties on a second molecule with loss of DEG. These advanced polyols form rapidly with high CO2 retention and relatively low polydispersity. This process has been characterized by size exclusion chromatography, quantitative capillary gas chromatography of the distillates, 13C‐NMR of the products, and alkaline hydrolysis of the products followed by quantification of the resultant glycols. The advanced polyols are largely alternating copolymers of DEG and CO2. They are valuable polyols for polyurethane fabrication.
N‐phenylglycine‐(thio)xanthene dye photoinitiating system and application to photopolymer for visible laser exposure
Authors: Yamaoka Tsuguo , Zhang Yu‐Chuan , Koseki Ken'ichi
Published: April 2003

It was found that the bimolecular type photoinitiators consisting of N‐phenylglycine and (thio)xanthene dyes exhibited high initiating efficiency on irradiation of visible light. From the time‐resolved spectroscopic study, the free radical is formed by the sensitized decarboxylation of N‐phenylglycine in the presence of (thio)xanthene dye. By using these initiating systems, the visible laser sensitive photopolymer was prepared and the imaging characteristics were evaluated.
Adsorption of chitosan and a quaternized derivative on kaolin
Authors: Domard A. , Rinaudo M. , Terrassin C.
Published: April 2003

Adsorption of Chitosan on kaolin was tested and a comparison was made with a fully quaternized derivative. The influence of pH, molecular weight, and acetyl content on the results was also studied. The adsorption isotherms and the flocculating properties as functions of the various parameters are discussed.
Sulfonic acid group‐containing thin films prepared by plasma polymerization
Authors: Inagaki N. , Tasaka S. , Miyazaki H.
Published: April 2003

Plasam polymerization of hydrocarbon/sulfure dioxide mixtures, C2H/SO2, C2H4/SO2, and CH4/SO2 mixtures, was investigated to obtain thin films containing sulfonic acid groups. Plasma polymerization of C2H2/SO2 and C2H2/SO2 mixtures gave filmlike products but that of the CH4/SO2 mixtures did not. The plasma polymers possessed much amount of sulfur and oxygen moieties with hydrocarbon chains. The sulfur moieties involved thio, sulfite, and sulfonic acid groups. This groups was a main product and reached 70–80 mol % of the total sulfur moieties. The remains (20–30 mol %) were sulfonic acid and sulfite groups. The oxygen moieties were hydroxyl and carbonyl groups with small amount of carbonxyl groups. The plasma polymers showed and hydrophilicity (the surface energy was 54–56mN/m) and good antithrombogenity.
Compounding of cellulose fibers with polypropylene: Effect of fiber treatment on dispersion in the polymer matirx
Authors: Raj R. G. , Kokta B. V. , Dembele F. , Sanschagrain B.
Published: April 2003

The compounding of Kraft pulp with polypropylene was stuided using a laboratory higheshear roller blender. Dipsersion was characterized by measuring the size and number of agglomerates in a thin compression‐moldled sheet. The effects of parameters such as surface treatment and mixing conditions were investigated. It is shown that with a suitable treatment, better dispersion of fibers can be achieved.
Influence of different imidazole catalysts on epoxy‐anhydride copolymerization and on their network properties
Authors: Bouillon Nelly , Pascault Jean‐Pierre , Tighzert Lan
Published: April 2003

The copolymerization of naidc and methyltetrahydrophthalic anhydrides and diglycidyl ether of bisphenol A (DGEBA) with various stoichiometric ratios [r = 2[anhydride]/DGEBA] and with different concentrations of several imidazoles has been studied. These results are compared with those obtained with a tertiary amine such as benzyldimethylamine, a well‐known efficient catalyst of epoxy‐anhydride copolymerization. Thermal and hydrothermal behaviors of these networks also have been examined.
Swelling of anionic and cationic starch‐based superabsorbents in water and saline solution
Authors: Castel D. , Ricard A. , Audebert R.
Published: April 2003

Starch graft superabsorbents were prepared by graft copolymerization either with polyacrylonitrile (PAN) and saponification of the resulting copolymer or with trimethyl–aminoethylacrylate chloride (CMA) and methylene bisacrylamide as crosslinking agent. The influence of several structural parameters on the swelling properties of these absorbents have been studied: crosslink density, ionic content, and composition of the starch. As expected, the absorbency decreases with an increase of the crosslink density. It increases with the ionic content of the graft copolymer up to a maximum, an excess of charges leading to a swelling decrease. The PAN branch length depends on the origin of the starch. High molar weight PAN was grafted onto waxy corn, a starch with high amylopectin content. The swelling increases with increasing molar weight of PAN up to 5 × 105. In saline solution the absorbency of both ionic gels decreases significantly. However, in the presence of multivalent ions their behavior is different. For cationic absorbents the swelling depends on the ionic strength but not on the ion valency. On the other hand, anionic absorbents are significantly affected by multivalent cations.
The effect of processing parameters on the morphology of an immiscible binary blend
Authors: Favis B. D.
Published: April 2003

In this study an immiscible blend of polypropylene(PP) and polycarbonate (PC) was examined. Experiments were carried out in an internal mixer and the objective was to examine the influence of the time of mixing, the speed of rotation of the rotors as well as the effect of time under quiescent conditions on the size and size distribution of the minor phase. The morphology was studied by light and electron microscopy and the photographs were quantitatively analyzed by semiautomatic image analysis. The effect of the time of mixing was studied for up to 20 min at three viscosity ratios for PC dispersed in PP. The most significant particle size deformation and disintegration processes take place within the first 2 min of mixing. After 2 min very little reduction in the size of the minor phase is observed up to 20 min mixing time, although some phase size/time dependence was observed at an intermediate viscosity ratio. The influence of rotor speed was also studied and the results indicate that this blend is insensitive to changes in the speed of rotation of the rotor over a three‐ to fourfold range. The effect of time at 250°C under quiescent conditions was studied at 7% and 23% composition (volume fraction) for PP dispersed in PC and also for PC in PP. Coalescence coarsening was observed only for 23% PC in PP where the particle size was found to increase by 75% after approximately 90 min at temperature.
Cellulose stability and delignification after alkaline hydrogen peroxide treatment of straw
Authors: Martel P. , Gould J. Michael
Published: April 2003

Neutron diffraction profiles for cellulose from different sources were compared before and after alkaline hydrogen peroxide (AHP) treatment. It was found that AHP treatment did not cause detectable changes in the structure of highly polymerized cellulose. In measurements on wheat straw, peaks were observed at the angles characteristic of pure cellulose. Changes, with AHP treatment, of the intensities, positions, and widths of these peaks were consistent with effects due to delignification, which frees the cellulose lattice from strains caused by the binding of lignin.
Rheological and morphological properties of thermal‐aged poly(phenylene sulfide) resin
Authors: Ma Chen‐Chi M. , Hsiue Lin‐Tee , Wu Wen‐Guey , Liu Wen‐Liang
Published: April 2003

This paper discusses the morphological properties of thermal‐aged poly(phenylene sulfide) (PPS) resin by Fourier‐transform infrared spectroscopy (FT‐IR) and solid‐state 13C‐NMR. Also included is a method of applying the dynamic melt viscoelastic properties to determine the molecular weight distribution of the PPS resin. For virgin PPS resin, two resonance peaks were detected by NMR magic angle spinning (MAS) and cross polarization (CP) studies. However, four additional peaks can be seen for heat‐treated PPS resin, indicating that the aromatic ring in PPS resin was attacked by sulfur‐containing species or by the aryl ether group. The two most important reactions are crosslinking and chain extension. However, the chain extension is predominant when PPS is heated in nitrogen. The results coincide with the phenomenon observed in FT‐IR studies. The molecular weight distribution of thermal‐aged PPS resin was determined from dynamic melt viscoelasticity data. Results show that the longer the preheated time the broader the molecular weight distribution. It indicates that crosslinking and chain‐extension reaction may have occurred when PPS resin was heated in air.