bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of irradiation on crystallinity and mechanical properties of ultrahigh molecular weight polyethylene
Authors: Zhao Yong , Luo Yunxia , Jiang Bingzheng
Published: April 2003

Ultrahigh molecular weight polyethylene (UHMWPE) has been irradiated (0–40 Mrad) with a Co60 source at room temperature under vacuum. The crystallinity has been investigated by differential scanning calorimetry (DSC) and small‐angle X‐ray scattering (SAXS). The mechanical properties have been determined at room temperature. A significant increase of heat of fusion can be seen at low irradiation doses, which is attributed to crystallization, caused by chain scission during the process of irradiation. It is also observed that the thickness of the lamellae changes with irradiation dose. The Young's modulus has been improved significantly after irradiation at low doses. © 1993 John Wiley & Sons, Inc.
On the poly(vinyl alcohol)–iodine complexes
Authors: Takamiya Hiroyuki , Tanahashi Yumi , Matsuyama Tosiki , Tanigami Tetsuya , Yamaura Kazuo , Matsuzawa Shuji
Published: April 2003

The color development due to the complex formation of poly(vinyl alcohol) (PVA) with iodine increased with increasing syndiotacticity of PVA. Isotactic PVA showed no color development. The color development of syndiotacticity‐rich PVA film decreased with increasing annealing temperature for films before complexization, whereas that of atactic (commercial) PVA increased with it. Lower temperatures, the elongation of complex film, and the presence of boric acid enhanced the absorbance at 600 nm due to I−5. The complexes are assumed to be made by incorporation of polyiodines into aggregates of syndiotactic sequences in PVA. The polarizability and electric conductivity of complex films are investigated. © 1993 John Wiley & Sons, Inc.
Rheological behaviors of bisphenol series thermotropic liquid crystalline wholly aromatic copolyesters
Authors: Zhao Zhouming , Wu Xuqin , Lin Yongwei
Published: April 2003

Rheological experiments were performed on a series of thermotropic liquid crystalline aromatic copolyesters based on terephthalic acid (TPA), isophthalic acid (IPA), p‐hydroxybenzoic acid (HBA), and a family of bisphenols. The anisotropic melts behaved as non‐Newtonian fluids in a shear elongation flow. The non‐Newtonian exponents of the melts decreased with increasing the linearity of the bisphenol bridge group, and decreased with increasing the optical anisotropy in the liquid crystalline phase. The cross‐section morphologies along the longitudinal direction of the extrudates were surveyed by scanning electronic microscopy (SEM) and discussed with melt‐flow rate distributions. The extrudates exhibited skin–core microstructures and oriented fibril structures. The die swells of the extrudates decreased sharply to negligible levels when shear stress was above 1000 Pa. © 1993 John Wiley & Sons, Inc.
Injection molding of polypropylene: X‐ray investigation of the skin–core morphology
Authors: Wenig W. , Herzog F.
Published: April 2003

The skin–core morphology of injection‐molded polypropylene bars has been investigated employing X‐ray small‐and wide‐angle scattering. The small‐angle scattering has been evaluated by means of interface distribution functions. It is found that skin and core exhibit different morphologies. In the skin, the crystal lamellae are oriented primarily around the c axis, but a (small) fraction of a*‐axis‐oriented lamellae also exists. The lamellar thickness in the skin layer measured from the meridional small‐angle X‐ray scattering shows higher values than in the core. The composition of the monoclinic α1, α2 crystal modifications show dependencies that are typical for the cooling conditions in the mold during injection. © 1993 John Wiley & Sons, Inc.
Synthesis of polymeric microspheres employing SPG emulsification technique
Authors: Omi Shinzo , Katami Ken'ichi , Yamamoto Arihiro , Iso Mamoru
Published: April 2003

Relatively uniform polymeric microspheres, the coefficients of variation being close to 10%, were obtained by the BPO‐initiated suspension polymerization of styrenic monomers. Unlike the conventional stirred‐tank system, a particular microporous glass membrane (SPG) provided uniform monomer droplets continuously when monomer was allowed to permeate through the micropores. The monomer droplets were suspended in an aqueous solution containing the stabilizing agents, transferred to a stirred vessel, and polymerized. Up to 10μm spheres, of a far narrower size distribution than those obtained by conventional microsuspension polymerization spheres, were obtained. The initial droplet size and distribution were retained with the successful suppression of secondary particle nucleation by the addition of hydroquinone in the aueous phase. Crosslinked polystyrene spheres were also synthesized in the presence of various low‐molecular‐weight diluents. While a good solvent, toluene, was not so effective; poor solvents, n‐heptane and n‐heptane, easily yielded the microporous structure, the specific surface area being as high as 160 m2/g. © 1994 John Wiley & Sons, Inc.
Crystallization characteristics of polypropylene and low ethylene content polypropylene copolymer with and without nucleating agents
Authors: Zhang Ruiyun , Zheng Haifeng , Lou Xiaolie , Ma Dezhu
Published: April 2003

In this paper, the crystallization characteristics of polypropylene and low ethylene content polypropylene copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). In order to determine the nonisothermal crystallization rate of these materials, a new estimation method was introduced. Comparing with the crystallization rate coefficient (CRC), which was proposed by Khanna, we found the new approach is more reasonable. From the analysis of results of DSC and PLM, it can be concluded that nucleating agent is more efficient than it is in PP homopolymer. © 1994 John Wiley & Sons, Inc.
Double melting phenomena of polyphenylene sulfide and its blends
Authors: Mai Kancheng , Zhang Mingqiu , Zeng Hanmin , Qi Shicheng
Published: April 2003

The melting behavior of PPS (polyphenylene sulfide) and its blends with PSF (bisphenol A polysulfone) and PEK‐C (polyetherketone with phthalidylidene groups) are investigated with DSC technique. It is found that, with a rise in melt temperature Tmelt and melt time tmelt, the intensities of the lower melting peaks of PPS increase while those of the upper ones decrease or disappear in some cases, which can be attributed to the obstructive effect of branching or crosslinking of PPS macromolecules on the crystallization of PPS at higher temperature. As the annealing crystallization temperature increases, both the peak temperatures and intensities of the lower melting peaks of PPS increase. PSF and PEK‐C have no influence on the lower melting peaks of PPS but are unfavorable to the crystallization of the higher melting species. The double melting behavior of the PPS component in the blends is much more susceptible to the changes in Tmelt and tmelt than that of neat PPS. © 1994 John Wiley & Sons, Inc.
Kinetic study of acrylic monomer grafting in the presence of a polyfunctional monomer onto radioperoxided poly(ethylene–tetrafluoroethylene) copolymer
Authors: Gineste Jean‐Luc , Largueze Christophe , Pourcelly Gerald
Published: April 2003

Acrylic acid (AA), methacrylic acid (MA) and diethyleneglycol dimethacrylate (DEGDM) are grafted onto 100 μm radioperoxided poly(ethylene–tetrafluroethylene) copolymer (ETFE). The influences of the homopolymerization inhibitor, the solvent, the grafting temperature, and the monomer content on the grafting kinetics are studied. For the grafting of acrylic monomers, the limitation of the grafting yield is more important for AA grafting whatever the nature of the metallic salt; the difference between the two homopolymerization inhibitors is their respective concentration to obtain a given grafting yield. For the AA + DEGDM cografting, the grafting yield increases with the DEGDM content of the grafting solution. In both cases, the overall activation energy has been calculated, and its variation as a function of the composition of the grafting solution is discussed. © 1994 John Wiley & Sons, Inc.
Heat sealing of semicrystalline polymer films. I. Calculation and measurement of interfacial temperatures: Effect of process variables on seal properties
Authors: Meka Prasadarao , Stehling Ferdinand C.
Published: April 2003

A finite element analysis (FEA) modeling technique was used to predict the interfacial temperature as a function of time during the sealing of semicrystalline polymer films. An experimental technique using micro‐thermocouples to measure rapidly changing interfacial temperatures during sealing was also developed. Agreement between predicted interfacial temperature profiles and measured values for polyethylene films was good except at temperatures substantially above the final melting point of the polymer. This deviation is caused by film‐thickness changes occurring during sealing that are not taken into account in the calculations. The effect of heat‐sealing process variables (seal bar temperature, dwell time, and pressure) on seal properties (seal strength, seal elongation, and seal energy) of polyethylene films has also been quantitatively determined. Seal properties are determined primarily by the maximum temperature achieved at the interface during heat sealing. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level, but longer times at a given interfacial temperature do not improve seal properties at the conditions of our experiments. A slight pressure is helpful in bringing two microscopically uneven film surfaces into intimate contact, but higher pressure has no beneficial influence on seal properties. However, increased pressures and dwell times at temperatures above the final melting point of the polymer are detrimental to seal appearance due to material deformation in the sealing area. © 1994 John Wiley & Sons, Inc.
Heat sealing of semicrystalline polymer films. III. Effect of corona discharge treatment of LLDPE
Authors: Farley James M. , Meka Prasadarao
Published: April 2003

The effects of corona‐discharge treatment (CDT) of commercial polyethylene (PE) Linear low‐density PE (LLDPE) were studied with special emphasis on the heat‐seal behavior of treated films. A range of treat levels, representative of those used in industry, was obtained by varying the applied power to a commercial, on‐line treater. Film surfaces were characterized by XPS and wetting‐tension measurements. The primary effect of CDT on the heat‐sealing behavior of LLDPE films is a transition in the failure mode of heat seals from a normal tearing or inseparable bond to a peelable seal. In addition, CDT increases the seal initiation temperature 5–17°C and decreases the plateau seal strength 5–20% as the treat level, or wetting tension, increases from 31 to 56 dynes/cm. These effects are attributed to cross‐linking during corona treatment, which restricts polymer mobility near the surface and limits the extent of interdiffusion and entaglements across the seal interface. Results of heat‐sealing studies with electron‐beam‐irradiated PE, chemically oxidized PE, and CDT polypropylene (PP) provide indirect evidence for the proposed surface cross‐linking mechanism. The effect of commercial levels of slip additives on the heat‐seal behavior was also investigated. © 1994 John Wiley & Sons, Inc.
A kinetic study of the effect of three catalytic systems on the curing of an unsaturated polyester resin
Authors: Salla J. M. , Ramis X.
Published: April 2003

We studied by differential scanning calorimetry (DSC) the influence of three tertiary amines used as promoters on the curing kinetics of unsaturated polyester resins catalyzed with an organic peroxide. The kinetic study was made by means of the analysis of isothermal experiments and we used a kinetic model that does not presuppose knowledge of the experimental rate equation f(α), which relates the reaction rate dα/dt at constant temperature with the degree of conversion α through a rate constant k according to dα/dt = kf(α). It is thus possible to predict the time, temperature, and degree of curing without needing to know f(α). This model makes a linear relation between the logarithm of time needed to reach a given degree of conversion with the inverse of the inverse of the curing temperature according to the expression ln t = A+E/RT for a constant α, where A is a constant, R is the universal gas constant, and E the activation energy. The proposed model has been used to calculate the activation energies for each degree of conversion according to the type and amount of promoter used. From the relation between the time and the curing temperature for a given conversion, it is possible to predict values of curing time for different temperatures. We thus simulated curing kinetics by using the proposed model and compared them with those obtained experimentally by DSC. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of polymers with pending UV‐absorber groups. I. Polymers based on polydimethylsiloxane
Authors: Riedel Jan‐H. , Höcker H.
Published: April 2003

The hydrosilylation reaction using dichloro(dicyclopentadiene) platinium (II) as catalyst is carried out to synthesize polymeric UV absorbers with polysiloxane backbone. An almost quantitative addition of vinyl groups of the UV absorber (benzophenone) to silane groups is observed. The IR spectra indicate the qualitative results of the reaction, whereas the 1H‐NMR spectra allow the following of the reaction quantitatively. Low glass transition temperatures are observed by DSC. UV spectroscopy shows that the extinction coefficient and spectra of the UV absorbers are hardly affected by the polymer analogous reaction. © 1994 John Wiley & Sons, Inc.
Structure and properties of poly(vinyl alcohol)–iodine complex formed in the crystal phase of poly(vinyl alcohol) films
Authors: Choi Yoon‐So , Miyasaka Keizo
Published: April 2003

The structure and optical properties of the complex formed in the crystal phase of PVA that is caused by soaking at very high iodine concentration are investigated. In the resonance Raman spectra of lightly and heavily iodinated specimens, two Raman shifts appeared at 109 and 161 cm−1. The 109 cm−1 peak due to the I mode was much stronger than the 161 cm−1 peak in a heavily iodinated specimen, whereas the peak was comparable with the 161 cm−1 peak in a lightly iodinated specimen. The complex formed in the crystal phase is identified as the I mode complex. It has an averaged iodine–iodine distance of 3.2 Å, which is different from the 3.08 Å of the I mode complex formed in the amorphous phase. The effect of KI concentration in the soaking solution on the formation of the complex is also examined. The increased KI concentration in the soaking solutions at a fixed iodine concentration increases the amount of the complex formed in the crystal phase. The change in the hydrogen‐bonding state in the crystal phase with the complex formation can be evidenced by IR and NMR. © 1994 John Wiley & Sons, Inc.
Effect of chain microstructure on modulus of ethylene–α‐olefin copolymers
Authors: Sehanobish K. , Patel R. M. , Croft B. A. , Chum S. P. , Kao C. I.
Published: April 2003

A family of copolymers of ethylene and α‐olefin resins with homogeneous branching distribution, which behaves as elastomers at high short‐chain branching levels and acts as typical thermoplastics at low short‐chain branching levels, is now available. Control of this broad range of properties stems from the ability to control the molecular architecture more effectively using Dow's INSITE

Trademark of The Dow Chemical Co.

technology than in the past. Due to the unique combination of narrow short‐chain branching distribution (SCBD) and narrow molecular weight distribution (MWD), these resins provide a unique opportunity to model structure/property relationships in branched ethylene‐α‐olefin copolymers. The modulus in branched ethylene‐α‐olefin copolymers with aliphatic branches is shown to be primarily dictated by crystallinity. It is shown that the branch distribution and the branch type have an insignificant effect on the modulus of ethylene copolymers containing aliphatic branches at a given crystallinity. Modulus data have been successfully modeled in such systems using a lamellar fiber‐reinforced amorphous matrix composite model. Switching from aliphatic branches to cyclic branches significantly affected the modulus at similar crystallinities. © 1994 John Wiley & Sons, Inc.
Metallization of polyimide film by wet process
Authors: Ho Syh‐Ming , Wang Tsung‐Hsiung , Chen Han‐Lung , Chen Ker‐Ming , Lian Syh‐Ming , Hung Aina
Published: April 2003

The interfacial adhesion strength of metallized polyimide (BPDA/ODA/PDA) has been studied with respect to polyimide surface molecular structure, reactions during electroless nickel deposition, baking, copper electroplating, and thickness of polyimide film. Each factor is discussed in terms of its influence on the peel strength. For practical application, operation at optimized conditions for each step of the metallization process is essential for sustaining the mechanical integrity of the copper/polyimide laminate. © 1994 John Wiley & Sons, Inc.
Low dielectric, fluorinated polyimide copolymers
Authors: Stoakley Diane M. , St. Clair Anne K. , Croall Catharine I.
Published: April 2003

Copolymers of fluorinated polyimides and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) have been prepared as films and composite laminates. The addition of BPDA was used as a means to achieve insolubility, making the polymers suitable as aircraft matrix resins. Glass transition temperatures, thermooxidative stabilities, and tensile strengths were increased with increasing BPDA content in the copolymers. Although the addition of BPDA did increase the UV cutoff and decrease the percent transmission slightly, the optical transparency of the polymers was still excellent. Dielectric constants of the copolyimide films ranged from 2.6 to 2.9. Astroquartz II laminates made with these resins had dielectric constant of 3.3–3.4. Flexural strength on unidirectional specimens were in the 1.24–1.41 GPa range and flexural moduli were 41 GPa. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Monosize polystyrene latices carrying functional groups on their surfaces
Authors: Tuncel Ali , Kahraman Ridvan , Piskin Erhan
Published: April 2003

In this study, monosized polystyrene (PS) latices were prepared by dispersion polymerization of styrene in isopropanol‐water media using poly(acrylic acid) (PAA) as a steric stabilizer and 2,2′‐azobisizobutyronitrile (AIBN) as an initiator. The effects of initiator and stabilizer concentrations, alcohol/water and monomer/dispersion medium ratio on the polymerization kinetics, and the size and monodispersity of PS latices were experimented with in a stirred reactor system. Monosize PS beads in the size range of 1.0–3.0 μm were obtained. The PS latex obtained in the first step having a diameter of 2.3 μm were used as the seed latex, and styrene/acrylate monomers, acrylic acid (AA), 2‐hydroxyethyl methacrylate (HEMA), and dimethylaminoethyl methacrylate (DMAEMA) were copolymerized onto the PS latex particles. The incorporation of functional groups to the surface and bulk structure of PS was confirmed by IR, FTIR, XPS, and zeta potential measurements. © 1994 John Wiley & Sons, Inc.
Studies on the thermal and curing behavior of polyimide blends
Authors: Choudhary Veena , Pearce E. M.
Published: April 2003

Blends of thermosetting (Thermid MC‐600 and Thermid FA‐700) and thermoplastic (UL‐TEM 1000) polyimide resins with different compositions were prepared. Curing and thermal behavior of the blends were investigated using differential scanning calorimetry and dynamic thermogravimetry in a nitrogen atmosphere. The peak exotherm temperature increased with increasing amount of thermoplastic resin, whereas the heat of polymerization decreased. The electrical characteristics of the blends were also investigated using a dielectric analyzer. Dynamic as well as isothermal scans were recorded. Ionic conductivity, permittivity, and the loss factor were measured as a function of temperature at various frequencies. These results showed the complete curing of the resins having 50% Ultem at 225°C in 1 h, whereas Thermid MC‐600 required a postcuring step to observe fully cured resins. A marginal decrease in thermal stability was observed on blending. © 1994 John Wiley & Sons, Inc.
Determination of filler content in rice husk ash and wood‐based composites by thermogravimetric analysis
Authors: Fuad M. Y. Ahmad , Zaini M. J. , Jamaludin Mustafah , Ishak Z. A. Mohd , Omar A. K. Mohd
Published: April 2003

Three new types of fillers for polypropylene are investigated. The first two were derived from burnt rice husk ash (RHA), whereas the third, a wood‐based filler, was processed from oil palm trunk. One important characterization of the composites involves the checking for the actual filler content and filler distribution within the matrix. An analytical technique is described here for computation of the filler content in the composites based on a simple expression derives from thermogravimetric analyses. For filler with volatiles such as the black RHA, the derived expression was pf = 106(rb/mc), and for easily burnt fillers (wood‐based), the expression was pf = 156(md/mc). The technique has shown good agreement and consistency between analyzed and actual filler contents and a uniform filler distribution within the polypropylene matrix. © 1994 John Wiley & Sons, Inc.
Synthesis, characterization, and properties of reactive liquid rubbers based on butadiene–acrylonitrile copolymers
Authors: Chen D. , Pascault J. P. , Bertsch R. J. , Drake R. S. , Siebert A. R.
Published: April 2003

Reactive liquid polymers (RLP), carboxyl‐terminated butadiene–acrylonitrile copolymers (CTBN), epoxy‐terminated butadiene–acrylonitrile copolymers (ETBN), amine‐terminated butadiene–acrylonitrile copolymers (ATBN) of different molecular weights (from 2200 to 6500 g/mol), and a nonfunctional butadiene–acrylonitrile copolymer were synthesized and characterized. Selection of end groups of RLPs and the synthesis were discussed. Phase behaviors of CTBN, ETBN, and NFBN in the RLP/DGEBA system were investigated regarding to the molecular weight, molecular weight distribution, chain composition, and end groups with a light transmission method. These experimentally determined phase behaviors will be related to those of the RLPs in the systems to be modified. The effect of molecular weight of RLP on the viscosity was also studied. © 1994 John Wiley & Sons, Inc.
Preparation of PVA membranes containing β‐cyclodextrin oligomer (PVA/CD membrane) and their pervaporation characteristics for ethanol/water mixtures
Authors: Yamasaki Akihiro , Mizoguchi Kensaku
Published: April 2003

Poly(vinyl alcohol) (PVA) membranes were modified by introducing β‐cyclodextrin (β‐CD) oligomer, which has an inclusion ability sensitive to size, structure, and hydrophilicity of the guest molecule. The modified membranes (PVA/CD membrane) were prepared by casting of the aqueous solutions of PVA and β‐CD oligomer. The CD oligomer was immobilized in the membranes by cross‐linking with glutaraldehyde. The cross‐linking times were 1 and 8 h. The content of CD in the membranes was 33 wt %. The effects of CD on the pervaporation characteristics for water/ethanol were investigated by comparisons with those of the cross‐linked PVA membranes. For the 1 h cross‐linked membranes, CD increased both the water permeation rate and selectivity at lower ethanol concentrations in the feed. At higher ethanol concentrations, CD increased the water selectivity, but it decreased the water permeation rate. For the 8 h cross‐linked membranes, at lower ethanol concentrations, CD increased the water permeation rate, but the water selectivity through the PVA/CD membrane was almost equal to that of the PVA membrane. At higher ethanol concentrations, CD increased the water selectivity and decreased the water permeation rate. These effects of CD can be interpreted in terms of the inclusion strength in the cavity and the reduction of the cross‐linking density of the PVA phase in the membranes. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical properties of poly(vinyl chloride) and polyurethane carboxylate blends
Authors: Kim Sang June , Kim Byung Kyu , Jeong Han Mo
Published: April 2003

The miscibility of thermoplastic polyurethane elastomers (TPUs) with poly(vinyl chloride) (PVC) was studied. PVC blends with TPUs, prepared from 4,4‐diphenylmethane diisocyanate as diisocyanate, hydroxy‐terminated poly(butylene adipate) (PBA) as the soft segment, and dimethylolpropionic acid as the chain extender carrying a latent anionic site for neutralization by triethylamine, showed a single glass transition temperature (Tg), irrespective of neutralization of latent anionic sites of TPU. But in neutralized TPU/PVC blends, limited intimate segmental mixing was perceived from the mechanical properties observed. When hydroxy‐terminated poly(propylene glycol) was used as the soft segment instead of hydroxy‐terminated PBA, PVC/TPU blends showed two separate Tg's of PVC and TPU, irrespective of neutralization. © 1994 John Wiley & Sons, Inc.
Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers
Authors: Metwally M. S. , Metwally N. E. , Samy T. M.
Published: April 2003

The article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross‐linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g−1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li+ −Na+ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.
Deswelling characteristics of poly(N‐isopropylacrylamide) hydrogel
Authors: Park Tae Gwan , Hoffman Allan S.
Published: April 2003

Poly(N‐isopropylacrylamide) gels exhibit a lower critical solution temperature (LCST) behavior in aqueous solution. At temperatures below the LCST, the gel is more hydrated than at temperatures above the LCST. At the LCST, the volume change is sharp. It is shown here that the water content of the gel above the LCST depends upon previous states of the gel (e.g., dry or wet), the heating rate, and the gel thickness. Deswelling kinetics are also affected by the gel thickness. Caffeine release experiments indicate that microscopic water pockets are formed within the matrix during the rapid gel collapse procedure. © 1994 John Wiley & Sons, Inc.
Interdiffusion in microlayered polymer composites of polycarbonate and a copolyester
Authors: Pollock G. , Nazarenko S. , Hiltner A. , Baer E.
Published: April 2003

The interdiffusion of two miscible polymers, polycarbonate (PC) and a copolyester (KODAR), was studied at temperatures from 200 to 230°C. The two polymers were coextruded as microlayer composites with up to 3713 alternating layers. The microlayer structure provided a large area of intimate contact between the two polymers with minimal mixing. Initially, two glass transition temperatures were observed by DSC that were intermediate between the glass transition temperatures of the pure components. Upon annealing, the glass transition temperatures shifted closer together, reflecting the extent to which inter‐diffusion had occurred. After no more than 2 h of annealing, a single glass transition temperature was observed. A model was formulated based on Fick's law of diffusion that related the mutual diffusion coefficient, D, to the change in the glass transition temperatures. The model also incorporated an “equivalent” residence time to account for diffusion that occurred during the coextrusion process. It was not necessary to consider the concentration dependence of D to satisfactorily describe the data with this model. For the temperature range from 200 to 230°C, the value of D varied from 4.0 × 10−16 to 1.6 × 10−15 m2/s. The activation energy of interdiffusion was determined to be 95 kJ/mol. © 1994 John Wiley & Sons, Inc.
Notch tip damage zone in biaxially oriented polypropylene at low temperature
Authors: Snyder J. , Hiltner A. , Baer E.
Published: April 2003

It is well established that biaxial orientation produces large improvements in the mechanical properties of polypropylene; this study further shows that the large improvements in mechanical behavior are magnified especially below the glass transition temperature. In this study, the irreversible deformation behavior of polypropylene during sharp single‐edge notch tension testing has been studied at two levels of biadial orientation at −40°C. Unoriented polypropylene formed a narrow wedge‐shaped damage zone that grows with increasing stress until catastrophic fracture occurs in a brittle manor. The damage zone consisted of many crazes that mainly grew perpendicular to the loading direction. The 50% oriented material initially developed a wedge‐shaped damage zone that grew wider as loading increased. This resulted in a drop of the length‐to‐width ratio at high sample extensions. The specimen fractured with stable crack growth in a ductile manner, showing a large resistance to crack growth. The 80% oriented material had a circular damage zone that consisted of many delamination crases. These crases grew by splitting the specimen in the thickness direction. Stable crack growth dominated the final failure process with the 80% oriented material showing nearly three times the toughness of the unoriented material. © 1994 John Wiley & Sons, Inc.
Mechanical properties of commingled plastic from recycled polyethylene and polystyrene
Authors: Li T. , Silverstein M. S. , Hiltner A. , Baer E.
Published: April 2003

The mechanical properties of commingled plastic in the form of thick beams prepared by the ET‐1 process have been examined in flexure and compression. The mechanical properties were evaluated in relationship to the hierarchical morphology described in a previous study. It was found that the flexural modulus was dominated by the properties of the skin and was satisfactorily modeled by approaches based on the observed micro‐morphology, such as the Nielsen and Davis models. It was not necessary to consider the skin–core macromorphology because the flexural modulus was dominated by the void‐free skin. The compressive modulus was lower than the flexural modulus and was strongly affected by the skin–core macro‐morphology. From the differences between the flexural and compressive moduli, it was determined that the core was essentially nonload‐bearing in compression. Flexural fracture initiated on the tension side of the beam and propagated rapidly through the thickness, whereas compressive failure occurred by longitudinal splitting of the skin. © 1994 John Wiley & Sons, Inc.
Crop resides as lon‐exchange materials. Treatment of soybean hull and sugar beet fiber (pulp) with epichlorohydrin to improve cation‐exchange capacity and physical stability
Authors: Laszlo Joseph A. , Dintzis Frederick R.
Published: April 2003

Ion exchange systems for the treatment of process water or wastewater may benefit by the use of inexpensive, disposable exchange materials before, or in place of, conventional regenerable exchange resins. Various agricultural by‐products have been proposed as suitable exchangers for this role, but they generally fail to have adequate capacity and physical stability for most applications. Two by‐products, soybean hull and sugar beet fiber, were found to have enhanced cation‐exchange capacity and stability upon treatment with epichlorophydrin and base. Exchange capacity was determined by measuring calcium binding. Physical stability was judged by three different aqueous extraction regimens. The most efficacious and economical reaction conditions found were: soybean hull and sugar beet fiber hydrated with water at a water‐to‐solids ratio of 6.4 : 1 and 8 : 1 (v/w), respectively, and epichlorohydrin applied at a 0.3 : 1 (v/w) ratio, for 6 h at room temperature. The resultant cross‐linked materials had cation‐exchange capacities of approximately 0.9 (soybean hull) and 1.3 (sugar beet fiber) meq/g dry weight. These epichlorohydrin‐treated agricultural by‐products may serve as cost‐effective, multivalent‐cation exchanges. © 1994 John Wiley & Sons, Inc.
Crystallinity in the polypropylene/cellulose system. II. Crystallization kinetics
Authors: Quillin Daniel T. , Yin Mengping , Koutsky James A. , Caulfield Daniel F.
Published: April 2003

Nonisothermal differential scanning calorimetry data for neat polypropylene and polypropylene with variously treated cellulose fillers has been used to solve for the Avrami exponent, n. Results show neat polypropylene to have an Avrami exponent value very close to the theoretically excepted value of 4.0. The addition of untreated cellulose fibers to polypropylene, which has been shown to produce a transcrystalline region, results in an exponent value of 2.7–2.9 for the initiation stage, followed by a value of 3.9 for the bulk stage. Treatment of the cellulose with alkyl ketene dimer, alkenyl succinic anhydride, or stearic acid results in intermediate exponent values from 2.7 to 3.9. These results verify the effectiveness of surface treatments in reducing the natural nucleating ability of cellulose. Sample mixing and filler content were also shown to play a role in the crystallization process. © 1994 John Wiley & Sons, Inc.
Morphology–property relationship in oriented PET films: Microstructural reorganization during heat treatment
Authors: Gohil Ramesh M.
Published: April 2003

Morphology–property relationships for simultaneously biaxially stretched films and heatset with fixed dimensions in the temperature range of 100–240°C have been studied. The observed transition in various properties at 180°C can be explained on the basis of microstructural changes caused by competition among several processes, such as crystallization, solid‐state thickening, melting, and molecular relaxation as well as by melting and recrystallization. The resulting structures and, thereby, the properties are different in temperature Regime‐II (Tg to Tmax) and Regime‐III (Tmax to Tm). In Regime‐II, the high rate of crystallization compared to the rate of molecular relaxation develops a constrained amorphous phase, whereas the predominant melting and recrystallization process in Regime‐III generates the relaxed amorphous phase. The structural reorganization during heat treatment is almost the same for uniaxially oriented film, fibers, and biaxially oriented films prepared under similar processing conditions. © 1994 John Wiley & Sons, Inc.
Continuous carbonization of polyacrylonitrile‐based oxidized fibers: Aspects on mechanical properties and morphological structure
Authors: Liu J. , Wang P. H. , Li R. Y.
Published: April 2003

By following the progression of continuous carbonization (300–1250°C) of polyacrylonitrile (PAN)‐based oxidized fibers, variations in tensile mechanical properties and morphological structure are reported in detail along the carbonization line. The tensile strength and Young's modulus of the fibers generally increase throughout the carbonization stage. Meanwhile, the fiber diameter displays a significant decrease. The preferred orientation of carbon layer planes is observed to increase remarkably for temperatures over 400°C. In a similar manner, the stacking size increases significantly but reaches saturation around 600°C, a changing point corresponding to that observed for the variation of the Young's modulus. However, beyond about 1200°C, the stacking size again displays a marked increase. Results thus obtained are interpreted in relation to each other. Possible implications are also discussed. © 1994 John Wiley & Sons, Inc.
Thermal characteristics of silver powder‐filled polypropylene composites
Authors: Maiti S. N. , Ghosh K.
Published: April 2003

The thermal properties of silver powder‐filled polypropylene composites were studied as a function of filler concentration. Thermal conductivities of the composites increased with filler content. Comparison of the data with theoretical predictive models for two‐phase systems showed that the Nielson equation agreed reasonably well with the measured values. A TGA study showed that presence of silver powder increased the thermal stability of polypropylene through an increase in activation energy. The thermal expansion coefficient of the composites exhibited a decreased in the presence of Ag powder. Surface treatment of Ag powder with a titanate coupling agent marginally increased thermal conductivity and decreased thermal expansion coefficient values, implying a degree of enhance adhesion of the filler with the polymer. © 1994 John Wiley & Sons, Inc.
Mechanical property and fracture morphology of fiber‐reinforced polysulfone plasticized with acetylene‐terminated sulfone
Authors: Mai Kancheng , Li Jiaju , Zeng Hanmin
Published: April 2003

The mechanical property and fracture morphology of glass fiber‐ (GF) and carbon fiber‐ (CF) reinforced polysulfone (PSF) blends with bis (4‐(4‐ethynyl phenoxy) phenyl) sulfone (ATS‐C) have been investigated. Experimental results show that the tensile and flexural properties and impact strength of GF‐reinforced ATS‐C/PSF composites decrease as the processing temperature or/and the processing time increase, but CF‐reinforced ATS‐C/PSF composites exhibit better mechanical properties. Although interlaminar shear strenght (ILSS) for fiber‐reinforced ATS‐C/PSF composites decreases, scanning electron microscopy (SEM) observation of fracture surface indicates that the fractural model of fiber‐reinforced PSF composites changes from the interfacial debonding fracture to the matrix fracture at the interfacial region with addition of ATS‐C and the increase of the processing temperature. The end‐use temperature of polysulfone can be retained and solvent resistance of polysulfone can be improved due to the formation of a semi‐interpenetrating polymer network. © 1994 John Wiley & Sons, Inc.
Copolymers of 1,5‐dioxepan‐2‐one and L‐ or D,L‐dilactide: Hydrolytic degradation behavior
Authors: Löfgren A. , Albertsson A.‐C.
Published: April 2003

The degradation of two series of copolymers made of 1,5‐dioxepan‐2‐one (DXO) and L‐or D,L‐dilactide has been investigated. In vitro degradation of the six copolymers with different ratios of the ingoing components was followed using size exlusion chromatography (SEC), nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The copolymers with a high content of lactic acid units showed a higher rate of hydrolysis than the DXO‐rich copolymers. The copolymer morphology also affects the rate of degradation as seen in the differences between amorphous and semicrystalline samples. The effect of electron beam sterilization was studied as well as the degradation products formed using the gas chromatography‐mass spectrometry (GC–MS) technique. The major degradation products resulted from ester bond cleavage. Kinetics of the in vitro degradation indicate a complex hydrolysis, probably a mixture of an uncatalyzed and catalyzed mechanism. © 1994 John Wiley & Sons, Inc.
Structure and properties of maleated high‐density polyethylene
Authors: Wang Yilong , Ji Deqiang , Yang Changlai , Zhang Hongjin , Qin Chuan , Huang Baotong
Published: April 2003

Possible changes in the structure and properties of maleated polyethylene (HDPE–MA) at different degrees of grafting (D.G.) were examined. At the level of 1.6 maleic anhydride (MA)/100 ethylene units E, 70–80% of crystallinity of the parent PE was retained (DSC and WAXD). Both melting temperature and crystallization temperature decreased only slightly with increase in D. G. The lattice constantsaandbof the orthorhombic PE crystallites remained constant, althoughcwas constantly at a larger value. The presence of MA groups hampered the packing of PE chains, leading to an increase in PE crystallite sizes ofL̄110andL̄200with maleation. Of the viscoelastic relaxations, dynamic mechanical analysis showed easier segmental motions and thus lowering in γ‐, α‐ and β‐relaxation temperatures with maleation. The breaking strength (σb) increased slightly with maleation, whereas the elongation at break (εb) lowered due to interaction between the MA groups. In all, in HDPE‐MA up to a D. G. of 1.6 MA/100 E, PE properties were maintained to be used per se or as a compatibilizer for blends involving PE or in any other usage where retention of PE properties is desired. © 1994 John Wiley & Sons, Inc.
Characterization of flexible slabstock foams containing lithium chloride
Authors: Moreland J. C. , Wilkes G. L. , Turner R. B. , Rightor E. G.
Published: April 2003

Characterization of a series of flexible polyurethane foams that contain LiCl in their formulation is discussed. These foams were developed in order to provide an alternative method to produce foams without physical blowing agents and still attempt to maintain specific important physical properties. Three high water content foams of varying LiCl content have been characterized by utilizing several morphological techniques as well as by their viscoelastic behavior. From a morphological standpoint, it appears that by adding LiCl to the formulation, there is less formation of urea‐rich aggregates that occur when LiCl is absent. Also, the hard segments are more dispersed as single units within the network. The cellular texture of the LiCl‐containing foams also shows a greater amount of cellular window material than the same foam without LiCl. Both of these changes due to LiCl addition are believed to bring about a significant increase in the amount of viscoelastic decay. This decay has been observed in tensile stress relaxation, compression load relaxation, and compressive creep studies. Temperature also has a more significant effect on the compression load relaxation behavior of foams with LiCl in their formulation than when absent. These differences in viscoelastic behavior between foams with and without LiCl in their formulation are attributed to the greater mobility of the hard segments in the presence of the LiCl additive serving as a localized “hard segment” plasticizer that also promotes more phase mixing in the foams. © 1994 John Wiley & Sons, Inc.
Polyacrylonitrile ultrafiltration membranes containing negatively charged groups for permeation and separation of dextran and dextransulfate
Authors: Kobayashi Takaomi , Miyamoto Takuro , Nagai Toshihiko , Fujii Nobuyuki
Published: April 2003

Ultrafiltration membranes of poly(acrylonitrile‐co‐sodium styrenesulfonate) [P(AN‐co‐SSS)] were prepared by casting the copolymer solution into water. The ultrafiltration rate of P(AN‐co‐SSS) membranes was controlled by adding poly(ethylene glycol) (PEG) of various molecular weights to the casting solution. The effect of the PEG addition on the membrane properties was examined. By using the P(AN‐co‐SSS) membranes, which possess various molecular weight cutoff (MWCO) properties, the permeation behaviors of dextran (D) and dextransulfate (DS) were compared. The P(AN‐co‐SSS) membranes markedly restricted the permeation of DS, owing to electrostatic barrier of the negatively charged groups in the membrane. The electrostatic sieve separation of DS and D, each having similar molecular size, with the membranes was also investigated. The membrane having negatively charged groups effectively rejected to DS with a high permselectivity. © 1994 John Wiley & Sons, Inc.
The deformation behavior of poly(dimethyl siloxane) networks. II. Equilibrium swelling
Authors: Venkatraman S. , Nixon A. , Highe A.
Published: April 2003

The equilibrium swelling behavior of end‐linked silicone networks has been studied, using low molecular weight silicone oils as diluents. Using the phantom and affine versions of the Flory–Rehner elasticity theory, the predictability of the equilibrium swelling has been examined. It was found that a modified version of the Flory–Rehner equation can be used to predict the equilibrium swelling behavior, provided the interaction parameter is known or measured. The modification is the use of the measured elastic shear modulus of the network prior to swelling, to calculate the density of network chains needed in the equation for swelling. This implies that both entangled and chemically linked chains contribute to the swelling behavior, since the modulus itself is predicted by the use of an equation that incorporates the contribution of entanglements. © 1994 John Wiley & Sons, Inc.
Liquefaction of wood in the presence of phenol using phosphoric acid as a catalyst and the flow properties of the liquefied wood
Authors: Lin Lianzhen , Yoshioka Mariko , Yao Yaoguang , Shiraishi Nobuo
Published: April 2003

The liquefaction of wood in the presence of phenol using phosphoric acid as a catalyst and the flow properties of the obtained liquefied wood were investigated. It was found that phosphoric acid is a satisfactory catalyst for liquefying wood. The amount of phenol that reacts with the liquefied wood components (i.e., combined phenol) increases with an increase in liquefaction temperature, liquefaction time, catalyst content, or liquid ratio. By removing the free phenol, the resulting liquefied woods become novolaclike resins. The measurements of the flow properties of these liquefied woods reveal that the melts of liquefied woods behave as pseudoplastics and their flows obey the Ostwald de Waele power law equation. The amount of combined phenol within the liquefied wood and the presence of filler in the liquefied wood have great influence on their flow properties. The flowing temperature, activation energy, and zero shear viscosity of the liquefied woods show tendencies to increase with an increase in combined phenol. © 1994 John Wiley & Sons, Inc.
X‐ray study of crystallinity and disorder in ramie fiber
Authors: Sao K. P. , Samantaray B. K. , Bhattacherjee S.
Published: April 2003

The degree of crystallinity and the disorder parameter in ramie fibers treated with various concentrations of aqueous NaOH solutions at room temperature (∼ 30°C) and at 0°C, respectively, have been analyzed by the wide‐angle x‐ray diffraction method of Ruland and Vonk.9–11 The results appear to suggest the presence of highly distorted crystalline regions that are first affected by lower concentrations of alkali. At higher concentrations of mercerizing strength it is observed that the lattice conversion to cellulose II is accompanied by a decrease in the degree of crystallinity and an increase in the disorder parameter values. The tensile properties of the fibers corroborate the results. © 1994 John Wiley & Sons, Inc.
Synthesis of nonionic and anionic hydrogels bearing a monosaccharide residue and their properties
Authors: Fukudome Norihiro , Suzuki Kazuya , Yashima Eiji , Akashi Mitsuru
Published: April 2003

Nonionic hydrogels bearing glucoside residues were synthesized by free‐radical copolymerization of glucosylethyl methacrylate (GEMA) and N,N′‐methylenebisacrylamide (BisA) at 0°C for 2 h using ammonium peroxodisulfate and N,N,N′,N′‐tetramethylethylenediamine as the initiator. The cross‐linked polymer gel was obtained quantitatively. The nonionic gels absorbed 30 times as much water as their own weight. Copolymerization of GEMA, sodium acrylate, and BisA gave anionic hydrogels, which absorbed ca. 100 times as much water as their own weight at pH 6.5. The swelling behavior of the nonionic and the anionic hydrogels bearing glucose residues was studied in detail. © 1994 John Wiley & Sons, Inc.