bluuebunny/crossref_metadata_2025 huggingface dataset:
Influences of copolymerization conditions on the structure and properties of isotactic polypropylene/ethylene–propylene random copolymer in situ blends
Authors: Zhang Yu‐Qing , Fan Zhi‐Qiang , Feng Lin‐Xian
Published: October 2004

A spherical TiCl4/MgCl2‐based catalyst was used in the synthesis of in situ isotactic polypropylene/ethylene–propylene random copolymer blends by propylene bulk polymerization and subsequent gas‐phase copolymerization of ethylene with propylene. Different copolymerization conditions, such as the reaction time, monomer pressure, and composition, were investigated, and their influences on the structure and properties of the products were studied. Raising the monomer pressure was the most effective way of speeding up the copolymerization, but it caused more increases in the random copolymer than the block copolymer fractions. Increasing the ethylene content of the monomer feed also resulted in higher reaction rates and copolymer contents, but the ethylene contents of both the random and block copolymer fractions were also raised. In situ blends that contain more than 50 wt % copolymer were prepared. The mechanical properties of the blends, including the impact strength and flexural modulus, were regulated in a rather broad range with changes in the copolymerization conditions. The properties were highly dependent on the amount, distribution, and chain structure of the copolymer fractions. The impact strength was influenced by both the random copolymer and block copolymer portions in a complicated way, whereas the flexural modulus was mainly determined by the amount of random copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 445–453, 2002; DOI 10.1002/app.10415
Effect of winding speed on the structure and properties of as‐spun poly(trimethylene 2,6‐naphthalenedicarboxylate) fibers as compared to poly(ethylene terephthalate) fibers
Authors: Stier U. , Oppermann W.
Published: October 2004

We present a comparative study of melt spinning of poly(trimethylene 2,6‐naphthalenedicarboxylate) (PTN) and poly(ethylene terephthalate) (PET) fibers with respect to the effect of winding speed (2000–6000 m/min): Structural changes were followed by X‐ray analysis, calorimetry, and measurements of density, boiling water shrinkage, and birefringence. As‐spun PTN fibers exhibited a low degree of crystallinity at relatively low speeds (< 2000 m/min). An increase in winding speed up to 6000 m/min only resulted in a minor enhancement of crystallinity and orientation. The small change of structural parameters accounted for the fact that tenacity and modulus did not rise significantly with increasing winding speed, contrary to the PET fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2489–2497, 2002
Preparation of high molecular weight poly(vinyl alcohol) with high yield by emulsion polymerization of vinyl acetate using 2,2′‐azobis(2‐amidinopropane) dihydrochloride
Authors: Lyoo Won Seok , Kwak Jin Woo , Choi Kyu Ha , Noh Seok Kyun
Published: October 2004

To prepare high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high yield and high linearity as a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was emulsion polymerized using, azo initiator, 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH). This was compared with the polymerization using potassium peroxodisulfate (KPS) as an initiator at various polymerization conditions. PVA, having a maximum number average degree of polymerization (Pn) of 3500 was obtained by the saponification of PVAc with Pn of 13,000–14,000, degree of branching (DB) for the acetyl group of about 3.4–3.5, and a maximum conversion of VAc into PVAc of 95%, which was polymerized by AAPH. These numerical values were superior compared with 14,500–15,000 of Pn of PVAc, obtained by KPS, and 3100 of maximum Pn of resulting PVA, DB of about 3.7–3.8, and maximum conversion of 90%. From the foregoing experimental results, we found that AAPH was a more efficient initiator than KPS in increasing both conversion of PVAc and molecular weight of PVA. In addition, PVAc microspheres, obtained by these emulsion polymerizations, can be converted to PVA / PVAc shell / core microspheres through a series of surface‐saponifications, maintaining their spherical morphology. Various surface morphologies, such as flat or wrinkled and swellable or nonswellable ones formed by the various molecular parameters and saponification conditions, were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2356–2362, 2004
Effect of particle size on the properties of Mg(OH)2‐filled rubber composites
Authors: Zhang Qi , Tian Ming , Wu Youping , Lin Gui , Zhang Liqun
Published: October 2004

A novel nanomagnesium hydroxide powder and three kinds of micro‐Mg(OH)2, with different particle sizes, were chosen as fillers and mixed with ethylene–propylene–diene monomer rubber (EPDM) to form a series of composites by a traditional rubber‐processing technique. The results showed that the mechanical properties of composites improved with decreasing particle size. The nanocomposites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calorimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with untreated powder, the peak value of heat release rate decreased and Tign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of particles sometimes substantially improved the mechanical properties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resistance of nanocomposites and flame retardance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2341–2346, 2004
Chain extension of PA1010 by reactive extrusion by diepoxide 711 and diepoxide TDE85 as chain extenders
Authors: Qian Zhenyu , Chen Xi , Xu Jun , Guo Baohua
Published: October 2004

The chain extension behaviors of two diepoxides, epoxide TDE85 and 711, were studied to evaluate their coupling effects on polyamide 1010 (PA1010). The former gave better coupling effects and a faster reaction rate. The torque of PA1010 melt increased dramatically with reaction time. The effect of the diepoxy chain extender on the flowability, thermal properties, and mechanical properties of chain‐extended PA1010 was investigated. The melt flow index (MFI) dramatically decreased as the diepoxide was added to PA1010, and the notched Izod impact strength of the chain‐extended products also increased. Furthermore, study on the usage of chain extender showed that there exists an approximate platform on the curve of melt torque versus content of chain extender, beyond which crosslinking may occur. Theoretical analysis of the occurrence of crosslinking was carried out by Flory criterion, which demonstrated that the average amount of functional groups in the chain extension system played a significant role in avoiding crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2347–2355, 2004
Comparative study of silicon‐containing polyimides from different oxydianilines
Authors: Lin Bao‐Ping , Pan Ying , Qian Ying , Yuan Chun‐Wei
Published: October 2004

Silicon‐containing polyimides were synthesized by solution polycondensation of bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride with 3,4‐oxydianiline and 4,4′‐oxydianiline, respectively. All the poly(amic acid) films could be obtained by solution‐casting from N,N‐dimethylacetamide solutions and thermally converted into transparent and tough polyimide films. The physical properties of thin films of those polyimides were compared by DSC, TGA, UV–visible spectroscopy, and dynamic mechanical analysis. The polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 3,4‐oxydianiline exhibited superior energy‐damping characteristic, mechanical properties, and optical transparency, whereas that from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 4,4′‐oxydianiline possessed higher glass‐transition temperature and thermal stability. Because of the unsymmetric structure of the polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 3,4‐oxydianiline, its increasing rate of linear coefficient of thermal expansion with temperature was quicker than that of the polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 4,4′‐oxydianiline. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2363–2367, 2004
Atomic oxygen resistant coating from poly(tetramethyldisilylene‐co‐styrene)
Authors: Devapal Deepa , Packirisamy S. , Korulla Raji M. , Ninan K. N.
Published: October 2004

A polydisilahydrocarbon, namely, poly(tetramethyldisilylene‐co‐styrene), synthesized from dimethyldichlorosilane and styrene in 1 : 0.5 mol ratio under dechlorination conditions was evaluated as an atomic oxygen (AO) resistant coating for polyimide film and C‐polyimide composite. Exposure of the polymer coating on a quartz plate to an AO fluence of 2.1 × 1021 atoms/cm2 resulted in practically no mass loss, indicating the AO resistance of the polymer. Ten percent solution of the polymer in toluene was applied on aluminized Kapton® polyimide film (125 μm thick) to obtain a coating thickness of ∼ 5 μm on the unaluminized surface. In a similar way, the coating was applied on a C‐polyimide composite. The coated and uncoated samples of Kapton® film and C‐polyimide composite were exposed to AO in a plasma barrel system. The uncoated aluminized Kapton® film (125 μm) lost 6.35 mg/cm2 when exposed to AO fluence of 1.6 × 1021 atoms/cm2 whereas the corresponding coated film lost only 0.14 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. In the case of the C‐polyimide composite, the uncoated sample lost 63.64 mg/cm2 on exposure to AO fluence of 1.8 × 1021 atoms/cm2 whereas the coated one lost only 0.21 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. SEM studies suggest that the coating offers good protection to the substrates. Formation of cracks on some portions of the coating was noticed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2368–2375, 2004
Scanning electron microscopy study of raw and chemically modified sisal fibers
Authors: Martins Maria Alice , Kiyohara Pedro Kunihiro , Joekes Inés
Published: October 2004

Mercerization and acetylation treatments were applied to sisal fibers to enhance adhesion with polymer matrices in composites. The structures of the untreated and treated fibers were assessed with scanning electron microscopy. The waste from sisal‐fiber decortication consisted of mechanical, ribbon, and xylem fibers, and their ultimate cells varied considerably in size and shape. After mercerization and acetylation, the fibers and conductive‐vessel surfaces were successfully changed. The parenchyma cells were partially removed, and the fibrils started to split, because of the alkali action. This increased the effective surface area available for contact with the matrix. The mercerized and acetylated fibers were coated with cellulose acetate by the grafting of the acetyl group in the fibrils. The treatment used to remove lignin and hemicellulose caused changes in the fiber surface but did not damage the fiber structure because the fibrils remained joined in a bundle. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2333–2340, 2004
Structure and properties of polyurethane acrylate prepolymers based on hydroxy‐terminated polybutadiene
Authors: Henry Isabelle , Pascault Jean‐Pierre , Taha Mohamed , Vigier Gérard , Flat Jean‐Jacques
Published: October 2004

Precursors of polyurethane acrylate based on hydroxy‐terminated polybutadiene (HTPB) soft segments, different diisocyanate and hydroxy ethyl acrylate (HEA) as hard units, were synthesized in bulk or in solution in methyl methacrylate. During precursor synthesis (in bulk), microphase separation was observed by small‐angle X‐ray scattering (SAXS). Diffusing particles are around 50 Å in size and are assumed to be assembling of hard segments. From these morphologies, it can be deduced that some isocyanate groups were trapped/or buried in hard domains. At a larger scale, around millimeters, hard segment crystallites were observed. Properties such as molar masses, melting and glass‐transition temperatures, and viscosities were correlated with precursor structure and morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 225–233, 2002
Synthesis of graft copolymeric membranes of poly(vinyl alcohol) and polyacrylamide for the pervaporation separation of water/acetic acid mixtures
Authors: Aminabhavi Tejraj M. , Naik Huchchuraya G.
Published: October 2004

Graft copolymers of poly(vinyl alcohol) (PVA) with polyacrylamide were prepared and membranes were fabricated at 48 and 93% grafting of acrylamide onto PVA. These membranes were used in the pervaporation separation of water/acetic acid mixtures at 25, 35, and 45°C. The permeation flux, separation selectivity, diffusion coefficient, and permeate concentration were determined. The highest separation selectivity of 23 for neat PVA at 25°C and the lowest value of 2.2 for 93% acrylamide‐grafted PVA membranes were observed. A permeation flux of 1.94 kg m−2 h−1 was found for the 93% grafted membrane at 90 mass % of water in the feed mixture. The diffusion coefficients in a water/acetic acid mixture had an effect on the membrane permselectivity. The Arrhenius equation was used to calculate the activation parameters for permeation as well as for the diffusion of water and of acetic acid. The activation energy values for the permeation flux varied from 97 to 28 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 244–258, 2002
Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene
Authors: Xiao Han‐Wen , Huang Shi‐Qiang , Jiang Tao , Cheng Shi‐Yuan
Published: October 2004

The miscibility of polymers is not only an important basis for selecting a proper blending method, but it is also one of the key factors in determining the morphology and properties of the blends. The miscibility between ethylene‐propylene‐diene terpolymer (EPDM) and polypropylene (PP) was explored by means of dynamic mechanical thermal analysis, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results showed that a decrease in the PP content and an increase of the crosslinking density of EPDM in the EPDM/PP blends caused the glass‐transition temperature peaks of EPDM to shift from a lower temperature to higher one, yet there was almost no variance in the glass‐transition temperature peaks of PP and the degree of crystallinity of PP decreased. It was observed that the blends prepared with different mixing equipment, such as a single‐screw extruder and an open mill, had different mechanical properties and blends prepared with the former had better mechanical properties than those prepared with the latter. The TEM micrographs revealed that the blends were composed of two phases: a bright, light PP phase and a dark EPDM phase. As the crosslinking degree of EPDM increased, the interface between the phases of EPDM and PP was less defined and the EPDM gradually dispersed in the PP phase became a continuous phase. The results indicated that EPDM and PP were both partially miscible. The mechanical properties of the blends had a lot to do with the blend morphology and the miscibility between the blend components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 315–322, 2002
Effect of synthesis parameters on thermal behavior of phenol–formaldehyde resol resin
Authors: Park Byung‐Dae , Riedl Bernard , Yoon Soo Kim  , So Won Tek
Published: October 2004

Differential scanning calorimetry (DSC) was used to investigate the influence of resin synthesis parameters on the thermal behavior of low molecular weight phenol–formaldehyde (PF) resol resins prepared with different formaldehyde/phenol (F/P) molar ratios, different sodium hydroxide/phenol (NaOH/P) molar ratios, and different catalysts. As the F/P molar ratio increased, the molecular weight and activation energy increased while the gel time, peak temperature, resin pH, and nonvolatile solids content decreased. By contrast, the molecular weight, gel time, resin pH, resin solids content, and peak temperature increased with an increasing NaOH/P molar ratio. However, the activation energy decreased with an increasing NaOH/P molar ratio. The polydispersity increased with both F/P and NaOH/P ratios. Calcium hydroxide gave a faster curing resin compared to sodium and potassium hydroxides. All DSC thermograms of this study showed just a single exothermic peak for the resins that were used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1415–1424, 2002
Tribological action of metallic fillers in poly(tetrafluoroethylene) composites
Authors: Yan Feng‐Yuan , Xue Qun‐Ji , Wang Xiaobo
Published: October 2004

The tribological behavior of poly(tetrafluoroethylene) composites filled with various metallic particles was investigated under the extreme friction conditions of a heavy load and reciprocation with a small amplitude. Two obviously distinct friction stages corresponding to the contact conditions were found. The phenomena of the accumulation of fillers on the contact surface and extrusion wear of the poly(tetrafluoroethylene) matrix were also observed. Based on the experimental results, the actions of metallic fillers on the transfer film formation were analyzed. It was noted that the transfer and accumulation of fillers could actually be considered to be an assimilating process of the friction pairs. Accordingly, the physical model of the transfer film formation process was described and some suggestions on the mechanism of load‐supporting actions of hard fillers were also proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1832–1840, 2002
Kinetics of the nonstationary photopolymerization of diacrylates
Authors: Bratus A. , Turovki A. , Medvedevskikh Yu. , Zagladko E. , Zaikov G.
Published: October 2004

The kinetics of non‐stationary photopolymerization (post‐polymeryzation) of some diacrylates at the wide range of initial conversions was investigated. All kinetic curves has two regions: quick and short, slow and long. Experimental results were compared with the kinetic model of the photoinitial three‐dimensional photopolymerization. It was determined that kinetic model allows us to describe the process of the post‐polymerization in the whole range of conversions. The rate constants of the linear break of the primary and secondary chains in the interphase layer were estimated. The increasing rate constants in the interphase are the similar for investigated diacrylates and do not depend on the glicol chain. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1892–1895, 2002
Influence of electron donors on the initial stage of cyclopolymerization of 1,5‐hexadiene with MgCl2‐supported Ziegler catalysts analyzed by temperature rising elution fractionation
Authors: Kono Hiroyuki , Mori Hideharu , Terano Minoru , Nakatani Hisayuki , Nishiyama Isa
Published: October 2004

Additive effects of donors on the initial polymerization of 1,5‐hexadiene with the MgCl2‐supported Ziegler catalysts were investigated by using the stopped‐flow method, temperature rising elution fractionation (TREF) analysis, and kinetic study. The cyclopolymerization of 1,5‐hexadiene proceeded within an extremely short period (≤ 0.2 s) and yielded a unique poly(methylene‐1,3‐cyclopentane). cis ring content and cis–cis unit in meso dyad of the resulting polymer were increased by the addition of electron donors. The influence of internal and external donors was examined by the estimation of kinetic parameters and TREF analysis. Because the addition of the internal donor caused an obvious change in one of the kinetic parameters and the microstructure, an isospecific active site was considered to be formed by the addition of the internal donor. In the case of the external donor, the additive effects on the stereospecificity were weaker than those of the internal donor. It was expected from TREF measurements that the external donor modified an aspecific active site into a lower isospecific active site. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2976–2983, 2002; DOI 10.1002/app.2326
Preparation and evaluation of some novel organo‐phosphorus compounds as antioxidants and antifatigue agents in rubber
Authors: Ismail M. N. , Yehia A. A. , Korium A. A.
Published: October 2004

Six organo‐phosphorus compounds were synthesized and incorporated in NR and SBR mixes. The rheometric characteristics of the green rubber mixes were determined using the oscillating disc rheometer. The prepared compounds were evaluated as antioxidants and antifatigue agents in NR and SBR vulcanizates. It was found that the prepared compounds are good antioxidant and antifatigue agents and their efficiency was better than that obtained by 4‐methyl‐2,6‐di‐tert‐butyl phenol, which is used in the rubber industry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2984–2992, 2002; DOI 10.1002/app.2327
Study on pH‐sensitive and thermosensitive polymer networks containing polyacetal segments
Authors: Du Juan , Peng Yuxing , Zhang Tingting , Ding Xiaobin , Zheng Zhaohui
Published: October 2004

A series of pH‐sensitive and thermosensitive polymer networks were first obtained by copolymerization of telechelic poly(1,3‐dioxolane) (PDXL) with acrylic acid (AA), acrylamide (AM), and N‐isopropylacrylamide (NIPAM), respectively. The copolymerization of PDXL diacrylate (PDXLDA) with AA, AM, or NIPAM is expected to lead to polymer networks in which homopolymeric segments of the monomer are connected by polyacetal segments. As a combination of these two parts, these polymer networks can have some interesting physical properties. For example, the copolymer networks of poly(AA‐b‐DXL) showed pH sensitivity, and both the copolymer networks of poly(AM‐b‐DXL) and poly(NIPAM‐b‐DXL) showed temperature sensitivity. Moreover, because of the low ceiling temperature of polyDXL, the networks containing polyacetal segments (PDXL) can degrade by treatment with a trace of appropriate cationic initiator. The polymer networks prepared were characterized by Fourier transform infrared, differential scanning calorimetry, and swelling data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3002–3006, 2002; DOI 10.1002/app.2329
Reactivity ratios of free monomers and their charge‐transfer complex in the copolymerization of N‐butyl maleimide and styrene
Authors: Zhao Youliang , Li Huaming , Liu Pengsheng , Liu Hongwei , Jiang Jing , Xi Fu
Published: October 2004

As for the charge‐transfer complex (CTC) formed by N‐butyl maleimide (NMBI) and styrene in chloroform, the complex formation constant was determined by 1H‐NMR of Hanna–Ashbaugh. The copolymerization of NBMI (NBMI, M1) and styrene (St, M2) in chloroform using AIBN as an initiator was investigated. On the basis of the kinetic model proposed by Shan, the reactivity ratios of free monomers and CTC in the copolymerization were calculated to be r12 = 0.0440, r21 = 0.0349, r1C = 0.00688, r2C = 0.00476, and the ratios of rate constants were obtained to be k1C/k12 = 6.40, k2C/k21 = 7.33. In addition, the copolymer was characterized by IR, 1H‐NMR, DSC, and TGA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3007–3012, 2002; DOI 10.1002/app.2330
Characterization of virgin and postconsumer blended high‐impact polystyrene resins for injection molding
Authors: Xu Guojun , Qiao Jianhong , Kuswanti Christiana , Koelling Kurt , Stuart Julie Ann , Lilly Blaine
Published: October 2004

This article focuses on the mechanical and rheological properties of virgin and recycled high‐impact polystyrene (HIPS) materials and describes our progress in evaluating the viability of reusing postconsumer and virgin polymer blends of HIPS from electronics equipment housings. Plastics reuse challenges are briefly reviewed, and experimental results, such as the rheological properties, mechanical properties, molecular weight, and morphology of different blends, are summarized and discussed for reuse of HIPS from printer and monitor housings. It is found that all blends have similar molecular weight and polydispersity. Furthermore, the recycled resin and virgin resin consist of almost the same components. However, the morphology of the rubber phases is different. The mechanical properties are similar for the ASTM specimens molded with either set of blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1–8, 2002; DOI 10.1002/app.2339
A kinetic investigation of thermally initiated emulsion copolymerization of styrene and methylmethacrylate without conventional initiators
Authors: Du Yong‐Zhong , Ma Guang‐Hui , Nagai Masatoshi , Omi Shinzo
Published: October 2004

The thermally initiated emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA) was carried out in the absence of conventional initiators. The hydroperoxide (HPO) concentration in the monomers, sodium dodecyl sulfate (SDS), deionized water, and the formulation of those for emulsion copolymerization were measured. The HPO concentration in ST and MMA increased with the storage time, and were considered to be the major sources of HPO. The thermal decomposition of hydroperoxide in monomers, the thermal initiation of ST by Mayo mechanism, and the complex formation between SDS and the monomers were proposed to be three main sources of the radical generation. It was confirmed that new polymer particles were generated throughout the polymerization process, and consequently resulted in a broader distribution of polymer particle size, compared with that for conventional emulsion polymerization. Approximately 80 wt % of monomer conversion was obtained in the presence of SDS at 373 K in 24 h. The initiation rate of the 30 wt % monomer charge was faster than those of 10 wt % and 20 wt % monomer charge. The latex instability at higher solid content was improved by adding electrolyte to promote the electrostatic repulsion force between the polymer particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 455–467, 2002; DOI 10.1002/app.2343
Continuous distribution kinetics for the thermal degradation of LDPE in solution
Authors: Kumar G. Sanjay , Kumar V. Ravi , Madras Giridhar
Published: October 2004

Polymer degradation in solution has several advantages over melt pyrolysis. The degradation of low‐density polyethylene (LDPE) occurs at much lower temperatures in solution (280–360°C) than in conventional melt pyrolysis (400–450°C). The thermal degradation kinetics of LDPE in solution was investigated in this work. LDPE was dissolved in liquid paraffin and degraded for 3 h at various temperatures (280–360°C). Samples were taken at specific times and analyzed with high‐pressure liquid chromatography/gel permeation chromatography for the molecular weight distribution (MWD). The time evolution of the MWD was modeled with continuous distribution kinetics. Data indicated that LDPE followed random‐chain‐scission degradation. The rapid initial drop in molecular weight, observed up to 45 min, was attributed to the presence of weak links in the polymer. The rate coefficients for the breakage of weak and strong links were determined, and the corresponding average activation energies were calculated to be 88 and 24 kJ/mol, respectively. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 681–690, 2002; DOI 10.1002/app.2344
Cure kinetics modeling and process optimization of the vialux 81 epoxy photodielectric dry film (PDDF) material for microvia applications
Authors: Dunne Rajiv C. , Sitaraman Suresh K. , Luo Shijian , Wong C. P. , Estes William E. , Periyasamy Mookkan
Published: October 2004

The cure kinetics of a photodielectric dry film (PDDF) material called ViaLux 81 has been studied, with the aim of understanding and optimizing its curing schedule for the fabrication of sequentially built‐up (SBU) high‐density‐interconnect printed wiring boards (HDI‐PWB). Initial dynamic differential scanning calorimetry (DSC) scans on the material revealed a two‐stage curing mechanism due to the long lifetime of the photoinitiator catalyst, which could not be separated at lower heating rates. On the other hand, the heat flow exotherm from isothermal DSC experiments showed a rapid reaction rate at the beginning with only a single peak. Therefore, to capture the complexity of the process, the faster multiple heating rate DSC experiments are used to predict the degree‐of‐cure (DOC) evolution. Two approaches have been developed based on the dynamic DSC data: (1) a “model‐free” approach, which only requires information about the cure‐dependence of the activation energy; and (2) a practical scheme to deconvolute the two curing peaks. Excellent agreement is observed for the heating rate experiments, but the methods are inadequate for predicting the DOC evolution under isothermal conditions. Therefore, a modified autocatalytic model with temperature‐dependent kinetic parameters has been developed based on the isothermal DSC data. This model predicts the DOC evolution for isothermal curing profiles very well. However, some discrepancy is evident in predicting the DOC evolution for heating rate experiments, due to the underestimation of the activation energy. With appropriate corrections, excellent predictive capability is illustrated for complex cure schedules with combined heating rate and isothermal segments. In addition, a cure process optimization strategy has been suggested, and the fabrication of fine features and microvias is demonstrated. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 691–700, 2002; DOI 10.1002/app.2345
Resin‐vulcanized NBR: Suitability of rheometric parameters for the calculation of cure kinetic constants
Authors: Sousa Ana M. F. , Peres Augusto C. C. , Nunes Regina C. R. , Visconte Leila L. Y. , Furtado Cristina R. G.
Published: October 2004

Several mechanisms can be used to describe the vulcanization process, and study of the reactions that actually take place can be done through different techniques. In this work, two methods that used rheometric parameters to calculate the kinetic constant were compared for the cure of nitrile rubber with a system of phenolic resin, polychloroprene, and zinc oxide. The formulations and data analysis were based on a complete factorial experiment design. The results enabled the identification of the influence of each parameter involved in the vulcanization process and the suitability of the two methods used. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 505–513, 2002; DOI 10.1002/app.2354
Relationship between the composition of polycarbonate copolymers and the refractive index
Authors: Okamoto Masaya
Published: October 2004

With a polycarbonate (PC)–poly(methyl methacrylate) (PMMA) graft copolymer and a PC–poly(dimethyl siloxane) (PDMS) block copolymer, the relationship between the composition of PC copolymers and the refractive index (nD) was investigated. According to the results, with a PMMA content of 38 wt %, the nD value of the PC–PMMA graft copolymer was nearly the same as that of electrical (E) glass (nD = 1.545), and with a PMMA content of 6 wt %, it was nearly the same as that of electrical corrosion resistance (ECR) glass (nD = 1.579). However, with a PDMS content of 19 wt %, the nD value of the PC–PDMS block copolymer was nearly the same as that of E glass, and with a PDMS content of 2 wt %, it was nearly the same as that of ECR glass. The combination of the PC–PDMS block copolymer and the glass fibers (GFs) of ECR glass led to haze values of 8 and 16% with GF contents of 10 and 20%, respectively. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 514–521, 2002; DOI 10.1002/app.2355
Effect of chlorination of ground rubber tire on its compatibility with poly(vinyl chloride): Dielectric studies
Authors: Naskar Amit K. , Khastgir D. , Bhowmick Anil K. , De S. K.
Published: October 2004

Dielectric analysis (DEA) of molded ground waste rubber tire (GRT) and its chlorinated derivatives (Cl‐GRT) was undertaken. Dielectric spectra of Cl‐GRT show formation of a biphasic structure consisting of the rubbery phase and a hard phase whose relaxation occurs in the high‐temperature region. DEA of plasticized poly(vinyl chloride) (PVC) containing GRT and PVC containing Cl‐GRT was also undertaken. It is observed that PVC containing Cl‐GRT exhibits a higher loss factor in the high‐temperature region than does the PVC compound containing GRT, due to enhanced interaction between Cl‐GRT and PVC. While the activation energy for dielectric relaxation of PVC does not change when compounded with GRT, it does decrease when PVC is compounded with Cl‐GRT due to dipolar interaction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 993–1000, 2002; DOI 10.1002/app.10320
Synthesis and characterization of fluorocarbon‐containing, hydrophobically associative poly(acrylic acid‐co‐Rf‐poly(ethylene glycol) macromonomer)
Authors: Zhang Yunxiang , Liu Shouping , Du Libin , Zhuang Dongqing , Chen Junyan , Jiang Ming , Hogen‐Esch Thieo E. , Wu Shuguang , Swift Graham
Published: October 2004

Fluorocarbon‐ or hydrocarbon‐end‐capped poly(ethylene glycol) (PEG) macromonomers were prepared with coupling methods. Several factors affecting the synthesis were studied, and the optimal condition was ascertained. The critical micelle concentrations of these macromonomers were determined with the fluorescence method. Novel fluorocarbon‐containing, hydrophobically modified, alkali‐soluble copolymers were made by the copolymerization of fluorocarbon‐ or hydrocarbon‐alkyl‐end‐capped PEG macromonomers with acrylic acid in an organic solvent. The effects of the macromonomer contents, polymerization conditions, spacer, temperature, shear rate, pH, and addition of salt and various surfactants on the solution viscosity were preliminarily investigated. A very strong hydrophobic association was found for these copolymer solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1035–1047, 2002; DOI 10.1002/app.10393
NK‐active cytokines IL‐2, IL‐12, and IL‐15 selectively modulate specific protein kinase C (PKC) isoforms in primary human NK cells
Authors: Vitale Marco , Bassini Alessandra , Secchiero Paola , Mirandola Prisco , Ponti Cristina , Zamai Loris , Mariani Adriana R. , Falconi Mirella , Azzali Giacomo
Published: October 2004

Natural killer (NK) cell function is largely modulated by growth factors and cytokines. In particular, interleukin (IL)‐2, IL‐12, and IL‐15 have major effects on the proliferative and cytotoxic activities of NK cells against tumor and virus‐infected cells. It is thought that the members of the protein kinase C (PKC) family of serine/threonine kinases play an important role in mediating the pleiotropic effects of cytokines on their target cells. We have investigated the downstream effects generated in purified human NK cells by IL‐2, IL‐12, and IL‐15 on PKCα and PKCϵ—a canonical and a novel isoform of PKC, respectively. By means of Western blotting, PKC activity assays, and immunofluorescence performed on highly purified preparations of primary human NK cells, we demonstrate that: 1) the three cytokines have similar effects on PKCα and PKCϵ activities; 2) whereas PKCϵ activity is induced by cytokine stimulation, PKCα activity is inhibited; and 3) both the induction of PKCϵ and the inhibition of PKCα functional activity are relatively early events in NK cells, while longer cytokine stimulations do not generate significant variations in enzyme activity, suggesting that the activation of both the canonical and novel isoforms of PKC are events required in the early phases of cytokine‐induced NK cell stimulation. Anat Rec 266:87–92, 2002. © 2002 Wiley‐Liss, Inc.
Functional anatomy of the deer spine: An appropriate biomechanical model for the human spine?
Authors: Kumar Naresh , Kukreti Sandeep , Ishaque Mushtaque , Sengupta Dilip K. , Mulholland Robert C.
Published: October 2004

The object of this study was to create a database for the biomechanical and certain functional anatomical parameters of the deer spine, for comparison with the human spine. This was done with a view toward using the deer spine as an alternative model for various biomechanical experiments, as it is difficult to procure nonembalmed, fresh human spine specimens. Bovine spongiform encephalopathy (BSE) and its human variant, Creutzfeld Jakob disease (CJD), prevent us from using bovine and sheep spine. There is a risk of transmission of disease through direct inoculation to the researcher working with infected bovine or sheep spine, and a theoretical possibility of transmission through the food chain if proper precautions for specimen disposal are not taken. We chose deer spine as an alternative for testing nonembalmed fresh human spine because, to date, there have been no reported cases of deer being carriers of prion diseases. Fifteen deer spine specimens were sectioned appropriately to obtain six functional spinal units for each level in the thoracic and lumbar spine. Each unit was tested in a Dartec materials testing machine (Dartec Ltd., Stourbridge, UK) under pure moments in three main anatomical planes. The range of motion (ROM), neutral zone (NZ), and stiffness parameters of the functional unit were determined in flexion‐extension, right/left lateral bending, and axial rotation. The data obtained were compared with the corresponding human spine data in the literature. Deer spine specimens were also studied for bone mineral density (BMD) using a DEXA scan. The results revealed the overall ROM was greater for deer spine compared to the human spine in the upper thoracic region, but less compared to human spine in the lower lumbar spine region. The only comparable region for ROM was in the lower thoracic/upper lumbar region. The stiffness coefficients were also comparable in this region. The BMD was also comparable in the two species. We conclude that the lower thoracic/upper lumbar region in the deer spine can be used as a model for some human biomechanical experiments because of its biomechanical and material similarities to the human spine of the corresponding region. Anat Rec 266:108–117, 2002. © 2002 Wiley‐Liss, Inc.
Transforming growth factor‐beta 3(Tgf‐β3) in a collagen gel delays fusion of the rat posterior interfrontal suture in vivo
Authors: Opperman Lynne A. , Moursi Amr M. , Sayne Jennifer R. , Wintergerst Ana Maria
Published: October 2004

Postnatal expansion of the intramembranous bones of the craniofacial skeleton occurs as bone growth at sutures. Loss of the bone growth site occurs when the suture fails to form, or when the newly formed sutures become ossified, resulting in premature obliteration. Previous experiments demonstrated that removal of dura mater from fetal rat coronal sutures, or neutralizing transforming growth factor‐beta 2 (Tgf‐β2) activity using antibodies resulted in premature obliteration of the suture in vitro. Conversely, addition of Tgf‐β3 to coronal sutures in vitro rescued them from osseous obliteration. To examine whether Tgf‐β3 rescues sutures from obliteration in vivo, a collagen gel was used as a vehicle to deliver Tgf‐β3 to the normally fusing rat posterior interfrontal (IF) suture. Surgery was done on postnatal day 9 (P9) rats, in which collagen gels containing 0, 3, or 30 ng Tgf‐β3 were placed above the IF suture, underneath the periosteum for 2 weeks. By P24, 75–100% of animals in control unoperated, sham‐operated, and collagen gel‐only groups had fused IF sutures. In contrast, 40% of sutures exposed to 3 ng Tgf‐β3 remained open, while sutures exposed to 30 ng Tgf‐β were similar to controls. By immunohistochemistry, sutures rescued from obliteration by Tgf‐β3 had the same Tgf‐β receptor type II (Tβr‐II) distribution as controls. However, Tgf‐β3‐treated sutures had altered Tgf‐β2 and Tβr‐I distribution compared to controls. Anat Rec 267:120–130, 2002. © 2002 Wiley‐Liss, Inc.
Circumferential variation in human second metacarpal cortical thickness: Sex, age, and mechanical factors
Authors: Lazenby Richard A.
Published: October 2004

Variation in cortical thickness (CT) in four quadrants of the human second metacarpal was investigated in a sample (100 males and 72 females, skeletal age 20 to 50+ years) from a 19th‐century cemetery. Both left and right elements were studied (total N = 344). Multivariate analysis of covariance (MANCOVA) (for age, sex, and side, controlling for absolute size) was used to test the hypothesis of equality of thickness in the dorsal, palmar, medial, and lateral quadrants. Differences in regional CT posits localized regulation of resorption and formation adapting bone shape to functional loads, with implications for activity‐modulation of skeletal senescence. The palmar cortex was found to be uniformly thicker in both sexes and both sides, and at all ages (young, middle, and old adult); the medial, lateral, and dorsal cortices did not differ significantly. Patterns of age‐related loss occurring preferentially at the endocortical surface differed between men and women, with women showing significant declines across all age groups for all quadrants, and males only small decrements after middle age. The greater CT in the palmar quadrant corresponds to the region of maximum compressive strain in the second metacarpal for functions involving full flexion (grasping). Although the palmar cortex is thicker at all ages, women lose mass in that quadrant at the same rate as in other quadrants, suggesting that function does not offer protection against endocrinologically‐mediated depletion of bone mass (postmenopausal osteopenia). Anat Rec 267:154–158, 2002. © 2002 Wiley‐Liss, Inc.
Patients' perceptions of the effects of systemic lupus erythematosus on health, function, income, and interpersonal relationships: A comparison with Wegener's granulomatosis
Authors: Boomsma Maarten M. , Bijl Marc , Stegeman Coen A. , Kallenberg Cees G. M. , Hoffman Gary S. , Tervaert Jan Willem Cohen
Published: October 2004

Objective

To describe the patients' perceptions of the effects of systemic lupus erythematosus (SLE) and Wegener's granulomatosis (WG) on health, function, income, and interpersonal relationships.

Methods

114 patients with SLE, and 79 patients with WG completed a self‐administered questionnaire. Patients had been diagnosed with SLE or WG for a median period of 10 and 5 years, respectively.

Results

All patients experienced substantial functional morbidity. Two‐thirds of the patients with SLE or WG reported either a periodic or permanent inability to perform daily activities at home and/or at work. Furthermore, SLE as well as WG had a considerable impact upon the psychological and social life, affecting their happiness and altering relationships.

Conclusion

Our study demonstrates that SLE and WG are associated with substantial medical morbidity resulting in physical and occupational disability. SLE has a profound impact on patients' lives, similar to that experienced in patients with WG.
Molecular biology of Fanconi anaemia—an old problem, a new insight
Authors: Ahmad Shamim I. , Hanaoka Fumio , Kirk Sandra H.
Published: October 2004

Fanconi anaemia (FA) comprises a group of autosomal recessive disorders resulting from mutations in one of eight genes (FANCA, FANCB, FANCC, FANCD1, FANCD2, FANCE, FANCF and FANCG). Although caused by relatively simple mutations, the disease shows a complex phenotype, with a variety of features including developmental abnormalities and ultimately severe anaemia and/or leukemia leading to death in the mid teens. Since 1992 all but two of the genes have been identified, and molecular analysis of their products has revealed a complex mode of action. Many of the proteins form a nuclear multisubunit complex that appears to be involved in the repair of double‐strand DNA breaks. Additionally, at least one of the proteins, FANCC, influences apoptotic pathways in response to oxidative damage. Further analysis of the FANC proteins will provide vital information on normal cell responses to damage and allow therapeutic strategies to be developed that will hopefully supplant bone marrow transplantation. BioEssays 24:439–448, 2002. © 2002 Wiley Periodicals, Inc.
Hydrodynamic properties of rigid macromolecules composed of ellipsoidal and cylindrical subunits
Authors: García de la Torre J. , Carrasco B.
Published: October 2004

A procedure is devised for the calculation of hydrodynamic properties of rigid macromolecules composed subunits that are modeled as ellipsoids of revolution and cylinders. Owing to the axial symmetry of these shapes, smooth shell models can be constructured for the subunit structure. The bead shell model so constructed is employed for the calculation of the properties. A computer program, HYDROSUB, has been written implementing both the model building and the hydrodynamic calculation. A detailed example of the use of this methodology is presented for the case of the solution properties of the human antibody molecule immunoglobulin G3 (IgG3). Finally, hints are given on other uses and applications of the procedure. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 163–167, 2002; DOI 10.1002/bip.10013
Molecular dynamics calculations on amylose fragments. I. Glass transition temperatures of maltodecaose at 1, 5, 10, and 15.8% hydration
Authors: Momany Frank A. , Willett J. L.
Published: October 2004

Molecular dynamics simulations (NPT ensembles, 1 atm) using the all atom force field AMB99C (F. A. Momany and J. L. Willett, Carbohydrate Research, Vol. 326, pp 194–209 and 210–226), are applied to a periodic cell containing ten maltodecaose fragments and TIP3P water molecules. Simulations were carried out at 25 K intervals over a range of temperatures above and below the expected glass transition temperature, Tg, for different water concentrations. The amorphous cell was constructed through successive dynamic equilibration steps at temperatures above Tg and the temperature lowered until several points of reduced slope (1/T vs volume) were obtained. This procedure was carried out at each hydration level. Each dynamics simulation was continued until the volume remained constant without up or down drift for at least the last 100 ps. For a given temperature, most simulations required 400–600 ps to reach an equilibrium state, but longer times were necessary as the amount of water in the cell was reduced. A total of more than 30 ns of simulations were required for the complete study. The Tg for each hydrated cell was taken as that point at which a discontinuity in slope of the volume (V), potential energy (PE), or density (ρ) vs 1/T was observed. The average calculated Tg values were 311, 337, 386, and 477 K for hydration levels of 15.8, 10, 5, and 1%, respectively, in generally good agreement with experimental values. The Tg for anhydrous amylose is above the decomposition temperature for carbohydrates and so cannot be easily measured. However, it has also been difficult to obtain a value of Tg for anhydrous amylose using simulation methods. Other molecular parameters such as end‐to‐end distances, mean square distributions, and pair distributions are discussed. Published 2002 John Wiley & Sons, Inc. Biopolymers 63: 99–110, 2002
A molecular dynamics study of the stoichiometric complex formed by poly (α, L‐glutamate) and octyltrimethylammonium ions in chloroform solution
Authors: Zanuy David , Alemán Carlos , Muñoz‐Guerra Sebastián
Published: October 2004

We present a molecular dynamics simulation at 300 K in explicit solvent environment of chloroform of the stoichiometric complex formed by poly(α,L‐glutamate) and octyltrimethylammonium ions. We observed that the α‐helix conformation of the polypeptide chain remains stable during a 2‐ns run. The surfactant ions predominantly adopted an extended conformation that is stabilized by favorable interactions with the organic solvent. Analysis of the organization of the surfactant with respect to the polypeptide chain indicated that each octyltrimethylammonium cation was preferentially bound to more than one carboxylate group. It was found that the most populated arrangement was that with the surfactant cations interacting with two carboxylate groups simultaneously. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 151–162, 2002; DOI 10.1002/bip.10016