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This article presents a list of research papers related to materials science, published in the "Journal of Materials Science." These research papers include "Adhesively-Bonded Joints and Repairs in Metallic Alloys, Polymers and Composite Materials," by A. Baldan; "Thermo-Mechanical Fatigue of Shape Memory Alloys," by E. Hornbogen; "Role of Entropy of Fusion in Phase Transformation and Self-Diffusion," by G.P. Tiwari, J.M. Juneja and Y. Iijima; "Models in Thermoluminescence," by C. Furetta and G. Kitis; and "Electrical Applications of Carbon Materials," by D.D.L. Chung.

A key requirement for polymer pipes, in having the ability to achieve a long in service life, is the retention by the polymeric material of its anti-oxidants. In dry air and other favourable environmental conditions the life-span of the polymer material can be many decades. However, when polymer pipes are transporting water and the pipes need to be installed in all kinds of ground conditions then the loss of anti-oxidant from the polymer can become more of a problem. To maintain integrity of water distribution networks, companies aim to plan for replacement of water pipes before they are likely to fail. This paper presents ways in which small scale evaluations of aged pipe material can be employed to assess remaining in-service life of water pipes. Small-scale chemical and physical evaluations have been devised to provide indicators of the ageing process with associated loss of mechanical properties. The presented studies were performed using MDPE and PE80 pipe materials. These materials were evaluated before and after ageing to identify which chemical and physical evaluations were the most appropriate to assess the remaining life of in service polymer pipes. [ABSTRACT FROM AUTHOR]

The pursuit for the electrosyntheses of high quality polycarbazole (PCz) films is a great challenge for the application of polycabazoles. The incorporation of thiophene unit into carbazole monomer might result in a novel polymer having both the advantages of polythiophene and polycarbazole. As expected in this paper, a novel conducting polymer, free-standing poly(9-(6-(thiophene-3-yl)hexyl)-9H-carbazole) (PTh-H-Cz) films with electrical conductivity of 7.8 S/cm, were synthesized electrochemically by direct anodic oxidation of a novel carbazole monomer, 9-(6-(thiophene-3-yl)hexyl)-9H-carbazole (Th-H-Cz), in boron trifluoride diethyl etherate (BFEE) solution. Incorporation of thiophene unit into carbazole monomer as a pendant led to the electrodeposition of high quality PCz films with metallic shine. Fluorescence spectral study revealed that as-formed polymer film in solid state was a good blue light emitter with strong emission at about 410 nm. This high quality free-standing PTh-H-Cz film will facilitate their potential applications as blue-light-emitting materials in organic light-emitting dioxide. [ABSTRACT FROM AUTHOR]

The present paper investigates the force-extension behavior of a stiff polymer under stretching inside a small tube. We develop a theory and perform Brownian dynamic simulations based on a recently developed generalized bead-rod model (GBR) to show that the force-extension relation of such a strongly confined polymer chain can be described by that of an unconfined polymer subject to an effective force which is derived based on Odijk’s theory of a confined polymer chain. [ABSTRACT FROM AUTHOR]

In this paper a numerical study is presented that concentrates on the influence of the interface roughness that develops during plastic deformation of a metal, on the work of adhesion and on the change of interface energy upon contact with a glassy polymer. The polymer coating is described with a constitutive law that mimics the behavior of Poly-Ethylene Terephthalate. It includes an elastic part, a yield stress, softening and hardening with increasing strains. For the interface between the metal and the polymer a mixed-mode (mode I and II) stress-separation law is applied that defines the interface energy and an interaction length scale. At the onset of deformation the surface of the substrate has a self-affine roughness characterized by the so-called Hurst exponent, a correlation length and an rms roughness amplitude, that evolves as a function of increasing strain. The findings are the following: the interface energy decreases until the strain at yield of the polymer coating. Interestingly, after yielding as the polymer starts to soften macroscopically, the decreasing average stress levels result in partial recovery of the interface energy at the interface. At higher strains, when macroscopic hardening develops the recovery of the interface stops and the interface energy decreases. The effect of coating thickness is discussed as well as the physical relevance of various model parameters. [ABSTRACT FROM AUTHOR]

Carbon nanotube reinforced polymer composites have been extensively researched [Shadler LS, Giannaris SC, Ajayan PM (1998) Appl Phys Lett 73:3842; Ajayan PM, Shadler LS, Giannaris C, Rubio A (2000) Adv Mater 12:750; Wagner HD, Lourie O, Feldman Y, Tenne R (1998) Appl Phys Lett 72:188; Thostenson ET, Chou T-W (2002) J Phys D: Appl Phys 35:L77] for their strength and stiffness properties. The interfaces between nanotubes and polymer matrix can play a critical role in nanocomposites for their mechanical properties, since the interfacial area is order of magnitude more than traditional composites. Unless the interface is carefully engineered, poor load transfer between individual nanotubes (in bundles) and between nanotubes and surrounding polymer chains may result in interfacial slippage [Shadler et al. (1998); Ajayan et al. (2000)] and consequently disappointing mechanical stiffness and strength. Interfacial slippage, while detrimental to high stiffness and strength, could result in very high mechanical damping, which is a hugely important attribute in many commercial applications. In this paper, we show that the mechanical damping is related to frictional energy dissipation during interfacial sliding at the extremely many nanotube-polymer interfaces, and characterize the impact of activation of the frictional sliding on damping behavior. [ABSTRACT FROM AUTHOR]

Preceramic polymers and expansion agents are being investigated to produce composite ceramic coatings for oxidation protection of metallic substrates. In this paper, we present results of a systematic approach to selecting the preceramic polymer and expansion agents and the optimization of the processing parameters to produce composite ceramics. Six commercially available poly(silsesquioxane) polymers and a polysiloxane were studied. In addition, several metals and an intermetallic were considered as potential expansion agents. Based on this study, the most desirable polymer/expansion agent combination and optimal processing parameters have been identified. [ABSTRACT FROM AUTHOR]

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al2O3. [ABSTRACT FROM AUTHOR]

The whisker-reinforced polymer composites have good friction and wear properties and widely used in many fields. Potassium titanate (K2Ti6O13) whiskers have good properties, lower prices and show good foreground in whisker-reinforced polymer matrix composites. The surface properties of the whisker are vital for the performance of the reinforced composites. In this paper, the friction and wear properties of potassium titanate whiskers reinforced bismaleimide copmposites and the surfaces of whiskers treated by coupling agents were studied. Two coupling agents, a silane compound (KH550) and a titanate (NDZ311) were selected to treat the surface of K2Ti6O13 whiskers, respectively. Three whisker-reinforced BMI composites, K2Ti6O13/BMI, K2Ti6O13 (KH550)/BMI and K2Ti6O13 (NDZ311)/BMI, were prepared and their tribological behaviors were investigated. Results show that the wear-resistance of the matrix improved by the incorporation of whiskers into the matrix, while the improvement efficiency is depended on the nature of the surface of whiskers and whisker content. The composite containing KH550 treated whiskers has the best wear-resistance, and that containing untreated whiskers has the poorest wear-resistance among the three composites. Experiment results were explained from the point of the interfacial adhesion between the matrix and whiskers as well as the surface morphologies of worn surface and wear particles of the matrix and composites. [ABSTRACT FROM AUTHOR]

This paper studied the progressive matrix cracking in high temperature polymer composite laminates that could be used for next generation high speed transport airframe structures and aircraft engine components exposed to elevated temperatures. Damage mechanisms of matrix cracking were identified by X-ray radiography at room temperature and in-test photography technique at high temperature. It was found that the non-deterministic scenario is always involved in the procedure of transverse matrix cracking. Monte Carlo simulations using experimentally obtained materials properties were applied to simulate the multiple transverse cracking and compared with the experiment data. Finally, a novel statistical model combining Weibull theory with shear lag model was proposed to predict the matrix cracking based upon the previously obtained probability density function of crack spacing. It is shown that the predictions of this statistical model agree well with the experimental results and can be used to have an in-depth understanding of the random matrix cracking problem in composite laminates. [ABSTRACT FROM AUTHOR]

Examines the two-step positive temperature coefficient effect in immiscible polymer blends filled with carbon black. Conductive polymer composite materials; Use of high density polyethylene (HDPE) and polypropylene (PP) as the polymer matrix; Dependence of the log resistivity on HDPE content in the HDPE/PP blends.

As flammable polymeric materials become more ubiquitous in consumer goods, home furnishings, and transportation, there is a growing need for safe and effective flame retardant treatments. Recent studies suggest that certain flame retardant chemistries exhibit environmental and health problems, which has prompted the development of new flame retardant technologies. Layer-by-layer assembly has emerged as a promising technique for depositing environmentally-benign flame retardants on a variety of polymeric substrates. This technology has allowed the translation of common flame retardant mechanisms onto the surfaces of flammable polymers in the form of nanometer-scale coatings. Significant reductions in heat release rates and smoke release, as well as the ability to self-extinguish in open flame tests, have been observed on a variety of substrates. This review provides a comprehensive description of flame retardant multilayer nanocoatings on textiles, foams, and bulk polymers, as well as insight into the future direction of this growing field. [ABSTRACT FROM AUTHOR]

A detailed morphological study of the microstructure of poly( p-phenylene benzobisoxazole) (PBO) fibres (HM and HM+) and a polypyridobisimidazole (PIPD) (HT) fibre has been undertaken using transmission electron microscopy. Both PBO and PIPD fibres are composed of rigid-rod polymers having p-phenylene rings in the molecular backbone and show high modulus (280-360 GPa) and high strength (4-6 GPa). It is found that the PBO HM+ fibre has the highest degree of molecular orientation of the three fibres and the longest crystal length along the fibre axis, while the PIPD fibre shows a lower degree of orientation and a shorter crystal length than the PBO fibres. To understand the effect of crystalline size and fine structure of the fibres upon mechanical properties, dark-field and high-resolution lattice images were obtained and analysed in detail. [ABSTRACT FROM AUTHOR]

Pure Al2O3–2SiO2 precursors (powders) for a geopolymer were prepared by a sol–gel method. The alkali-activated products derived from the precursors meet the general criteria for a geopolymer. The structure of the powders was investigated by NMR, XRD, and FTIR analysis, and their alkali-activation properties were studied. The data show that the powders when heat treated at 200 °C begin to contain 5-coordinated Al, those heat treated at 300 °C can begin to undergo alkali-activation, and those heat treated at 300–800 °C possess a number of structure characteristics similar to metakaolin, and the properties of their alkali-activated products are similar to those of the metakaolin geopolymers. [ABSTRACT FROM AUTHOR]

Polyacrylamide/poly(vinyl alcohol)/polyacrylamide/graphite interpenetrating network (PAM/PVA/PAM/G IPN) hydrogel is synthesized using a simple two-step polymerization method. The swelling behaviors of the hydrogel depend on the PVA, graphite, and crosslinker dosages, and swelling process is dominated by a relaxation of macromolecule chains. Owing to IPN structure, the hydrogel shows a good mechanical strength and thermal stability. On the other hand, the incorporation of graphite improves the conductivity of the hydrogel. [ABSTRACT FROM AUTHOR]

Natural rubber-clay composites were prepared by direct polymer melt intercalation. Ca-montmorillonite Jelšový Potok (JP; Slovakia) and Na-montmorillonite Kunipia-F (KU; Japan) were ion exchanged with octadecyltrimethylammonium (ODTMA) bromide and were used as aluminosilicate fillers. Silica Ultrasil VN3 was used in amount of 15 phr as conventional filler. The effect of clay or organoclay loading from 1 up to 10 phr on the mechanical properties was evaluated from the tensile tests (stress at break, strain at break and modulus M100). Organic modification resulted in an increase of toluene uptake degree for both fillers. While an addition of unmodified KU had no effect on tensile strength and deformation at break, a reinforcing effect was observed for the mixture containing 10 phr of unmodified JP. Both ODTMA modified fillers (KU and JP) exhibited substantial increase in tensile strength and deformation at break; JP proved to be more effective compared to KU also if modified with ODTMA. The highest stress at break and strain at break values for natural rubber composites were obtained with 15 phr of SiO2 and 10 phr of montmorillonite; however, the effect of exchangeable cation was minor. [ABSTRACT FROM AUTHOR]

Shape memory polyurethane (SMPU) cross-linked by a polyethyleneglycol (PEG) spacer at its side was compared with a linear SMPU and the one randomly cross-linked by glycerol. The SMPU was composed of 4,4′-methylenebis(phenylisocyanate) (MDI), polytetramethyleneglycol-2000 (PTMG-2000), 1,4-butanediol (BD), glycerol, and PEG-200 as a spacer. PEG-200 connected the glycerol hydroxyl groups of two polyurethane chains via the connecting agent, MDI. Tm of the soft segment increased with the increase of cross-linking content. Cross-link density measured by the swelling experiment increased in proportion to the glycerol content. A surprising increase in maximum stress compared to the linear SMPU was attained without any sacrifice in strain. Remarkably, the stress–strain curve revealed that the PEG cross-linked SMPU exhibited a similar behavior and superior tensile mechanical properties to natural rubber. Storage modulus also increased and loss tangent became broad in distribution over the temperature range after PEG cross-linking. Shape recovery rate went up to 96.8%, and shape recovery speed was three times faster than that of linear SMPU. [ABSTRACT FROM AUTHOR]

A small amount of polymer in water solution form (polyvinylpyrolidone or polyvinylalcohol) was added to a mix high silicate cement + amorphous silica, with reduced water to cement ratio. It was shown that as the molecular mass of the polymer is increased, the fracture stress and the stored energy at fracture of the specimens improved. The polymer induces an increase of the critical stress intensity factor ( K Ic ) (crack initiation). The fracture behaviour of the polymer modified cement paste beyond the elastic domain is also affected by PVA or PVP additions. The dissipated energy measured using the crack opening displacement CMOD was increased by a factor of two with 4wt% of PVP and by a factor of three with 3wt% of PVA, as a consequence of operative toughening mechanisms. The increase of mechanical properties is explained in case of PVP by crack interactions due to CSH microstructure modifications, and with PVA by crack bridging mechanisms as a consequence of dispersed polymer rich nodules in the hydrates phase. [ABSTRACT FROM AUTHOR]

The reaction kinetics and mechanism of geopolymers are studied. The dissolved silicate concentration decreases from the beginning of the reaction. A characteristic time ‘ t 0,vit’ for the setting of the reaction mixture is derived from isothermal Dynamic Mechanical Analysis experiments. ‘ t 0,vit’ increases with SiO2/R2O but goes through a minimum for increasing water content. The reaction is slower for K compared to Na-silicate based systems. 29Si and 27Al solution NMR are used to probe the molecular changes. 27Al NMR and FTIR reveal that an ‘intermediate aluminosilicate species’ (IAS) is formed from the start of the reaction. The concentration decrease of OH− during low-temperature reaction is related to the formation of IAS. The rate law of this process seems to be obeyed by a total reaction order of 5/3, with a partial order of 1 for OH− and 0 for Na+ in the silicate solution. During first heating after polymerization water is lost leading to a distortion of the Al environment. According to XRD, no crystallization occurs below 900 °C. However, between 950 and 1100 °C a crystallization exotherm of nepheline is observed with DSC for a geopolymer with SiO2/Na2O = 1.4. Neither T g of the amorphous geopolymer, nor the shrinkage and expansion around T g during first heating, cause a measurable heat effect. [ABSTRACT FROM AUTHOR]

Coextrusion is a novel fabrication method for ceramic processing. However, the rheological behavior of ceramic/polymer blends during batching and extrusion in a coextrusion process is not well understood. In this study, the rheological properties of BaTiO3/polymer mixtures during batching in a high-shear rate mixer (C.W. Brabender) were investigated and several models were evaluated. The BaTiO3/polymer mixtures exhibited shear thinning behavior with a yield stress. The power-law model still fit for the data obtained from the high-shear rate mixer in the tested shear rate range. The results also showed that Bousmina’s model only fits well for the pure polymer melts. For the ceramic/polymer mixtures, large deviations from Bousmina’s model were observed. [ABSTRACT FROM AUTHOR]

The main goal of this work is to find a reasonable explanation for the frequently reported drastic deviations from the “rule of mixture” applied for calculation of the overall microhardness, H, of complex polymer systems comprising a soft, (with a glass transition, T g, or melting, T m, temperatures below room temperature) component and/or phase. According to the common practice, the contribution to H of the soft component and/or phase, H s, is considered as H s = 0, which results in extremely large differences between the measured and calculated H values for systems comprising more than 20–25 wt% soft component and/or phase. For such systems a different deformation mechanism during indentation process is postulated, namely “floating” of the solid particles in the soft component and/or phase, in addition to their plastic deformation. The contribution of the “floating effect” to the overall H is accounted for by the empirically derived relationship H = 1.97 T g−571. Using the reported data on H and T g for homopolymers, blockcopolymers and blends, the H values are recalculated and a good agreement with the experimentally measured values is found. A modified additivity law is suggested, which contains a term accounting for the contribution of the soft component and/or phase to the overall microhardness via the relationship between H and T g; its application results in much smaller differences between the measured and calculated H values. [ABSTRACT FROM AUTHOR]

Changes in the permeability tensor of fabric preforms caused by various modes of fabric distortion and fabric-layers shifting and compacting is one of the key factors controlling resin flow during the infiltration stage of the common polymer-matrix composite liquid-molding processes. While direct measurements of the fabric permeability tensor generally yield the most reliable results, a large number of fabric architectures used and numerous deformation and layers rearrangement modes necessitates the development and the use of computational models for prediction of the preform permeability tensor. The Lattice Boltzmann method is used in the present work to study the effect of the mold walls, the compaction pressure, the fabric-tows shearing and the fabric-layers shifting on the permeability tensor of preforms based on orthogonal balanced plain-weave fabrics. The model predictions are compared with their respective experimental counterparts available in the literature and a reasonably good agreement is found between the corresponding sets of results. [ABSTRACT FROM AUTHOR]

The elongational rheology of some fiber forming polymers, such as polypropylene (PP), polyethylene (PE), nylon 66, and lyocell (cellulose dissolved in N-Methylmorpholine/water) solutions, has been characterized using hyperbolic convergent dies in a capillary rheometer, at different Hencky strains, processing temperatures, and as a function of elongational strain rates up to 600 s− 1. The influence of melt flow rate (MFR) and molecular parameters is studied and it is shown that the elongational viscosity curves can be shifted with respect to both temperature and Hencky strain. [ABSTRACT FROM AUTHOR]

We report the characteristics of polymer/quantum dot solar cells fabricated using a water-soluble polymer and carbon nanotubes in a bulk heterojunction configuration. The water-soluble polythiophene polymer showed significant photoresponse and the potential for use in photovoltaics. The addition of carbon nanotubes to the polymer resulted in an order of magnitude increase in the photoconductivity. Improved charge separation and collection was evidenced by the large difference between light and dark conductivities as well as the increase in both open circuit voltage and short circuit current. Finally, photovoltaic cells using aligned nanotubes showed further improvement in the photoconductivity and IV characteristics. [ABSTRACT FROM AUTHOR]

Polyurethane-based conducting composites with polyaniline, polythiophene or polypyrrole are in the class of modern macromolecular materials that combine the toughness and elasticity of a polyurethane matrix with conductivity of intrinsically conducting polymers. Since the methods of preparation strongly influence the structure and properties of resulting composite/blend, this work aims at a systematic description of polyurethane-based conducting composites. This review has been structured to present an overview on preparations, characterisation and applications of polyurethane-based conducting materials with polyaniline, polythiophene or polypyrrole. [ABSTRACT FROM AUTHOR]

Polymethylmethacrylate (PMMA), polystyrene (PS) and polycarbonate (PC) were incorporated into the pitch with an objective to increase the tensile strength and tensile modulus of the pitch fibres (green) and to retain or to improve the mechanical properties of the carbonised fibres. It was found PMMA addition to the pitch increases the strength or flexibility of the green fibres but results in the formation of highly porous carbon fibres. The incorporation of PS and PC improves the tensile strength and tensile modulus both at the green and carbonised levels. The enhancement of mechanical properties is better in the case of carbon fibres derived from PC modified pitches. [ABSTRACT FROM AUTHOR]

Evaluates mechanical properties of two glass-fiber-reinforced polymers (GFRP), using transverse impact, double cantilever beam (DCB) and end-notched flexure tests. Results of the transverse impact and DCB tests showed a clear difference in delamination resistance between the two GFRP; Similarity of the delamination resistance in the shear mode; Effect of the toughness variation in different modes of loading.

Water-soluble chitosan with low molecular weight was prepared by the depolymerization of chitosan with aqueous H2O2 solution. The IR and 1H-NMR studies verify that depolymerization leads to the breakage of 1,4-β-D-glucoside bonds of chitosan. X-ray analysis shows the depolymerization takes place at the surface of the chitosan in crystal region by so called peeling-off process while the amorphous portion is depolymerized by penetrating pattern. [ABSTRACT FROM AUTHOR]

Asymmetric styrene/butadiene block copolymers and their blends with polystyrene homopolymer are studied, using transmission electron microscopy and scanning force microscopy, to explore the influence of phase morphology on the microindentation hardness and the nano-mechanical deformation mechanisms. In contrast to polymer blends and random copolymers, in which microhardness generally follows the additivity law, the behaviour of the investigated block copolymer systems is found to significantly deviate from the hardness additivity behaviour. Owing to the modified architecture, the asymmetric star block copolymer having 74 vol% polystyrene possesses a lamellar morphology, which partly explains the observed low hardness values. An additional explanation is found in the large plastic homogeneous deformation of the polystyrene (PS) lamellae by means of a new micromechanical mechanism called thin layer yielding. In the blends of a star block copolymer with polystyrene homopolymer, a rapid change in the micromechanical deformation behaviour is found to cause a shift in the observed microhardness to larger values. A major conclusion of our investigations is that microhardness of the triblock and star block copolymers can only be explained in the light of the morphology and nano-mechanical deformation mechanisms involved. [ABSTRACT FROM AUTHOR]

The effect of the particle size of metakaolinite on the reaction kinetics of low-temperature synthesized inorganic polymer glasses is studied. The heat capacity of the material during isothermal cure is measured by Modulated DSC (MDSC). This signal can be followed quantitatively during the complete course of the reaction, whereas the heat flow signal is sometimes too small for quantitative interpretations. A characteristic time for the reaction, defined as onset of vitrification, is also measured with Dynamic Mechanical Analysis (DMA). The DMA and MDSC results show that the reaction rate increases with decreasing particle size of metakaolinite, at least till a particle size of about 2 μm. It can be concluded that the first step of the reaction, breaking down the metakaolinite grains, occurs at the surface of the particles. The second step is the building of a network starting from the reaction products of the former reaction. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and solvatochromic behavior of a new series of chiral polyesters are reported. These polymers with π-conjugated donor-acceptor segments were synthesized with a view to be suitable for second harmonic generation. The polyesters were prepared by the reaction of diacid chlorides with biphenolic azo chromophores with Λ-conformation and optically active dihydroxy compound (isosorbide). The polymers containing isosorbide units are optically active. They showed Tg between 100°C to 160°C and are stable up to 400°C. A red shift in the longer wavelength absorption band of these polymers in UV-Vis. absorption spectra (positive solvatochromism) shows that the dipole moment of excited state is higher than that of the ground state. Therefore these polyesters are expected to have good second harmonic generation capability. [ABSTRACT FROM AUTHOR]

Mg amalgam reacts with PTFE (foil or oriented film on Si) to give a thin surface layer containing MgF2 in a mixture with complicated, air-sensitive, carbonaceous product containing large amount of residual C-F bonds. The reaction does not propagate into the bulk polymer, which, consequently, retains its white color even after hundreds of hours of reaction at 150 °C. These findings contrast with the reactivity of PTFE with amalgams of alkali metals, Li, Na, K. The differences are interpreted, in terms of the electrochemical model of amalgam carbonization, as blocking of charge (e−/Mg 2+) propagation through the modified layer. AFM patterns show that the Mg-treatment increases the surface roughness. The molecular-level ordering of PTFE films is strongly perturbed by the action of Mg-amalgam; the treated surface shows only small proportion of organized macromolecules. [ABSTRACT FROM AUTHOR]

Three series of isotactic polypropylene characterized by different molecular weights and the same isotactic index have been studied during crystallization under static and shearing conditions. The shear is induced by the displacement of a glass fiber in the molten polymer. The monoclinic α-phase is here formed under shear with a columnar organization at the surface of the glass fiber, and does not appear under static condition. The growth-rate, constant during the shear-induced crystallization experiment, is compared with the result obtained from static crystallization. An important increase of the growth-rate due to the shear flow is observed. This increase depends on the molecular structure. The average molecular weights ―Mw and ―Mz seem to be the most important molecular parameters, for which an excellent correlation is obtained. The increase of these parameters ―Mw and ―Mz leads to a significant enhancement of the growth-rate, which can be multiplied by a factor of 10 in the present conditions. [ABSTRACT FROM AUTHOR]

The article reports on the syntheses and the electronic behaviors of alternating indium-organic moiety binary hybrid copolymers. The authors claim that indium is an important key atom in the field of electronic and photochemical industries and the authors assumed that an indium-organic moiety hybrid material is expected to show unique properties.

The article focuses on effects of organic acids on sol-gel transition of silicic acid-Arheological study. The sol-gel transition in the silica system is dependent upon the degree of hydrolysis and polymerization reaction in the system. The polymerization reaction for the formation of the gel network occurs in different stages, i.e. polymerization of monomer to form particles, growth of particles and finally linking of particles into chains and the formation of the network which extends throughout the liquid medium. The structural evolution through the growth of silicate polymers from the genesis to the gel point has been well established by various in-situ methods such as NMR, vibrational spectroscopy and small-angle scattering.

Reports on an attempt to overcome stress-caused birefringence in polymers through modification of existing polymer systems to control or compensate for molecular orientation. Reduction of orientation-related birefringence; Suitability of polymers for waveguide applications; Achievement of index reproducibility.