Preparation of compatible blends of poly(methyl methacrylate) used in dentistry with a reactive terpolymer containing maleic anhydride and their thermomechanical characterization

This study focuses on the preparation of compatible blends with the poly(methyl methacrylate) (PMMA) using a reactive terpolymer maleic anhydride–styrene–vinyl acetate (MA–St–VA). In the first series of experiments, binary blends of the PMMA and the MA–St–VA terpolymer have been prepared in tetrahydrofurane. The PMMA and the MA–St–VA terpolymer formed the compatible blends. The effects on thermomechanical properties of MA–St–VA terpolymer ratio in the blends were studied. The glass transition temperatures (T_g), thermal expansion coefficient (α), and other thermomechanical parameters for the blends have been established by TMA method and the compatibility of two polymers has been evaluated by these TMA parameters. The addition of MA–St–VA terpolymer to PMMA made a plasticizing effect on PMMA. This effect regularly changed with the increasing of the terpolymer in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 363–367, 2006     

Stress relaxation of woodfiber–thermoplastic composites

Woodfiber–polypropylene and woodfiber–waste polyethylene composites have been produced by injection molding and by hot pressing the thermoplastic between woodfiber mats. The stress relaxation under constant strain in these composites has been studied at 25, 50, and 80°C. The results have been compared with similar experiments performed on neat thermoplastics. It is interesting to note that the presence of woodfibers as reinforcement in the composites restricts the stress relaxation, but their effectiveness decrease with the increase in ambient temperature. Composites made by hot pressing the woodfiber mat and the thermoplastic are found to exhibit a lesser amount of relaxation than those made by injection molding the same combination. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 401–407, 2006     

Dielectric properties of γ‐irradiated POE highly filled with aluminum hydroxide

The influence of γ irradiation on the dielectric and physicochemical properties of polyethylene‐octene elastomer (POE) containing 120 phr aluminum hydroxide (Al(OH)₃) as fillers has been investigated. The dielectric properties of the γ‐irradiated POE highly filled with Al(OH)₃ have been measured over a wide range of frequencies (70 kHz–3 MHz). It was found that γ irradiation strongly influences the dielectric properties of the POE composite in the dose range 0–250 kGy. POLYM. ENG. SCI. 46:1721–1727, 2006. © 2006 Society of Plastics Engineers     

Resin II: Thermal degradation studies of terpolymer resins derived from 2,2′‐dihydroxybiphenyl,urea, and formaldehyde

The terpolymer resins have been synthesized by the condensation of 2,2′‐dihydroxybiphenyl with urea and formaldehyde in the presence of 2M HCl as a catalyst and with varying molar proportions of reactants. Elemental analysis, IR, NMR and UV–Visible spectral study, and TGA–DTA analysis characterized the resins. The number average molecular weight was determined by nonaqueous conductometric titrations. Thermal studies of the resins have been carried out to determine their mode of decomposition, activation energy, order of reaction, frequency factor, entropy change, free energy, and apparent entropy change. Freeman–Carroll and Sharp–Wentworth methods have been applied for the calculation of kinetic parameters, while the data from Freeman–Carroll method have been used to determine various thermodynamic parameters. The order of thermal stabilities of terpolymers has been determined using TGA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 227–232, 2006     

Analysis of the structural parameters of polyacrylonitrile fibers containing nanohydroxyapatite

The structural parameters and strength properties of a new generation of polyacrylonitrile fibers have been analyzed. These fibers, after being carbonized, can be used in biomaterial engineering. They are characterized by a high tensile strength of 31–43 cN/tex. An advantageous influence of nanoparticles added to the fiber matter on the degree of crystallinity has been found. When nanoparticles of hydroxyapatite are incorporated into these fibers, their degree of crystallinity increases by about 5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 760–765, 2006     

Surface characteristics of untreated and modified hemp fibers

Natural cellulosic fibers, including hemp, are increasingly being used for composite reinforcement. However, their poor adhesion with synthetic resins limits their use as reinforcing agent. It is generally accepted that interfacial adhesion can be best described in terms of dispersion forces and acid–base interactions. Therefore, there is a need for quantitative determination of acid–base character of natural cellulosic fibers. In this study, acid–base characteristics and dispersion component of surface energy of hemp fibers have been determined using inverse gas chromatography. Effect of alkalization and acetylation on acid–base characteristics has also been examined. The results indicate that alkalization and acetylation make the hemp fiber amphoteric, thereby improving their potential to interact with both acidic and basic resins. Finally, a parallel is drawn between the changes in fiber‐matrix acid–base interactions and the actual improvement in the mechanical properties of the composites manufactured using resin transfer molding process. POLYM. ENG. SCI. 46:269–273, 2006. © 2006 Society of Plastics Engineers     

Preparation and characterization of alginate and hydroxyapatite‐based biocomposite

In this article, we report a novel route for the preparation of alginate‐hydroxyapatite biocomposite. Hydroxyapatite has been nucleated on alginate chains by precipitation method to obtain a biomimetic artificial bone‐like composite. The composite was characterized by powder XRD, FTIR, TGA, DTA, and SEM to ascertain its phase homogeneity and particle size distribution. Hydroxyapatite particles on alginate matrix are around 500–1000 nm in diameter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5162–5165, 2006     

Effect of solution concentration on the properties of nanocomposites

Though a large number of nanocomposites prepared by solution process has been reported in the literature, effect of solution concentration on properties of the nanocomposites has not been studied. In the present work, new fluorocarbon–clay nanocomposites were prepared by a solution mixing process. Characterization of the nanocomposites was done with X‐ray diffraction technique and atomic force microscopy. Effects of different rubber‐solution concentrations (5, 10, 15, 20, and 25 wt %) on the mechanical and dynamic mechanical properties of the resultant nanocomposites were investigated. Optimum properties were achieved at 20 wt % solution. The data could be explained with the help of structure of the nanocomposites and dispersion of the clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2407–2411, 2006     

Investigation on gradient dielectric characteristics of bamboo (Dentroclamus strictus)

Dependence of dielectric constant (ε′) and dielectric dissipation factor (tan δ) on distance from outermost skin to the center of bamboo has been determined. Dielectric measurements have been done in the temperature range of 24–120°C and in the frequency range, 4–100 kHz. Gradient behavior in ε′ and tan δ has been found in bamboo. It has also been observed that ε′ and tan δ increase with increasing temperature and decrease with increasing frequency. Relaxation times have been calculated for the four samples at 80, 90, and 100°C temperatures, which show that relaxation time decreases with the increase of temperature because of the increased molecular mobility. A continuous increase in the hardness from center (48) to outer surface (70) and density from 0.45 to 0.80 g/cc has been observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 380–386, 2006     

Humidity sensitivity of polypyrrole and polypyrrole/SBA‐15 host–guest composite materials

Polypyrrole (PPY) and PPY/SBA‐15 host–guest composite materials have been prepared using chemical synthesis route and characterized by XRD, IR, N₂ adsorption–desorption isotherms, and SEM. The humidity sensitive properties (HSP) of this kind of materials have been studied by analyzing the variation curve of impedance as a function of relative humidity. It was found that the PPY/SBA‐15 host–guest composites materials exhibit better HSP than that of the corresponding pure PPY. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3301–3305, 2006     

New aspects of polymeric sheet punch deformation

Two methods of punch deformation of flat polymeric materials have been studied and compared between themselves. The areas of the method application for the determination of fabric mechanical and exploitation stability and also the suitability of methods for the evaluation of effectiveness of technological treatment with liquid chemical softeners have been analyzed. The geometrical and mechanical behavior of flat polymeric materials (woven and knitted fabrics) during pulling of a disc‐shaped specimen through a central hole of KTU‐Griff‐Tester has been analyzed on the basis of pulling parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 358–361, 2006     

Noise generation and propagation control in disc brake systems using composite friction materials composed of thermoplastic elastomers as viscoelastic materials

Attempts have been made for the first time to produce a thermal sensitive friction material by the inclusion of thermoplastic elastomers (TPE) with combined plastic and rubbery properties as viscoelastic polymeric materials into the composition of the friction material for the purpose of increasing damping behavior. To evaluate the viscoelastic parameters such as loss factor (tan δ) and elastic modulus (E′) of the friction material on the molecular scale, dynamic mechanical thermal analysis was performed on the samples. Natural frequencies and mode shapes of the friction material and brake disc were determined by modal analysis. Styrene–butadiene–styrene (SBS), styrene–ethylene–butylene–styrene (SEBS) and nitrile rubber/polyvinyl chloride (NBR/PVC) blend systems have been used as TPE materials. However, NBR/PVC and SEBS were found to be more effective in preventing the noise generation and reducing the amplitude of the brake vibrations. All the friction materials containing TPEs exhibited more damping characteristics within a wide range of temperature compared with the damping characteristics of the reference sample. POLYM. COMPOS. 27:461–469, 2006. © 2006 Society of Plastics Engineers.     

Coaxial electrospinning of PC(shell)/PU(core) composite nanofibers for textile application

Functional core–shell structured composite nanofibers can be fabricated through electrospinning of two polymer solutions in a coaxial, two‐capillary spinneret system. Composite nanofibers, polycarbonate (PC, shell)/polyurethane (PU, core), have been developed by this technique. Morphological, structural, infrared spectroscopy, and mechanical performance are conducted for the developed nanofibers. Their applications as textile materials have been explored. POLYM. COMPOS. 27:381–387, 2006. © 2006 Society of Plastics Engineers     

Effect of organoclay content on the rheology,morphology, and physical properties of polyolefin elastomers and their blends with polypropylene

The effect of onium‐ion exchanged montmorillonite clay (organoclay) on the rheology and physical properties of maleated ethylene–octene copolymer and ethylene–propylene rubber elastomers has been examined. The formation of a nanocomposite hybrid, containing substantial amounts of exfoliated clay, was accompanied by significant increases in the complex viscosity, elastic and loss moduli, and a narrowing of the region of linear viscoelasticity, attributed to both filler/polymer and filler/filler interactions. The properties of blends of these elastomers with polypropylene were dominated by the reinforced elastomeric matrix, into which the organoclay resided preferentially. The nanocomposite blends exhibited very fine morphologies, as well as a good balance of stiffness and ductility and enhanced thermal stability. POLYM. ENG. SCI., 46:1491–1501, 2006. © 2006 Society of Plastics Engineers     

Studies on production of polypropylene filaments with increased temperature stability

High Modulus high tenacity polypropylene filaments have been prepared by drawing them on a heater with a gradient of temperature. The thermal properties have been analyzed, and the effects of nature of the gradient and end temperatures on thermal properties of the filament have been investigated for such filaments. Low shrinkage values even at 150°C, high retention of storage modulus in dynamic mechanical analyses and very low change in length in thermomechanical analyses have been the characteristic of the gradient drawn filaments. The filaments have high crystallinity, crystal perfection, and crystal orientation. In addition, the reported process has the advantage of being continuous in nature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 838–842, 2006     

Reactive processing and evaluation of butadiene–styrene copolymer/polyaniline conductive blends

Blending is an important way to obtain materials based on intrinsically conductive polymers and conventional plastics and rubber materials. Much research has been carried out to determine the best performance of materials be used for electrostatic dissipation and electromagnetic interference shielding. Mechanical mixing, codissolution, and in situ polymerization have been used to prepare these materials. The method used depends on the host polymer and its thermal stability and acid attack resistance. Homogeneity and miscibility are properties that should be controlled during blend preparation. In this study, we prepared a conductive thermoplastic elastomer material based on butadiene–styrene copolymer (SBR) and polyaniline (PANI) doped with dodecylbenzene sulfonic acid (DBSA) and poly(styrene sulfonic acid) (PSS). PSS also acted as compatibilizer between PANI and SBR. PANI was doped by reactive processing with DBSA and PSS to produce the conductive complex PANI–DBSA–PSS. This complex was mixed with 90, 70, and 50% (w/w) SBR in a counterrotatory internal mixer. Conductivity tests, swelling studies, thermal analysis, and mechanical property and reflectivity testing were done, and the results show a strong dependence on PANI concentration and the ratio between PANI–DBSA and PSS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 681–685, 2006     

Silicon‐containing heterocyclic polymers and thin films made therefrom

Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the chloroform or N‐methylpyrrolidone solutions of polyimides or poly(imide‐amide)s containing silicon and phenylquinoxaline units in the main chain. The polymers have been synthesized by solution polycondensation reaction of aromatic diamines having preformed phenylquinoxaline rings with bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride or with a diacid chloride resulting from the reaction of this dianhydride with p‐aminobenzoic acid. The polymers were easily soluble in polar aprotic solvents and showed high thermal stability. The free‐standing films exhibited good mechanical properties with tensile strengths in the range of 48–86 MPa, tensile modulus in the range of 1.25–2.22 GPa and elongation at break in the range of 3–37%. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz were in the range of 2.94–3.08 for polyimides and 3.89–4.49 for poly(imide‐amide)s. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3062–3068, 2006     

Catalytic activity of polymer–montmorillonite composites in chemical reactions

Polymer–clay composite material has been prepared by intercalation of polymeric ammonium salt onto the montmorillonite (Na–MMT) followed by grafted polymerization of hydroxyethyl methacrylate onto amine‐terminated poly(butadiene‐co‐acrylonitrile)–montmorillonite (ATBN–MMT) intercalate. The hydroxyl groups were modified to chloromethyl groups followed by conversion to onium salts, which are suitable as phase transfer catalysis. The catalytic activities of the supported catalysts were investigated in nucleophilic reactions of thiocyanate and cyanate ions with alkyl and aryl halides. The rates of the reactions have been investigated under different factors such as the nature and structure of the support, the amount of catalyst, the solvent, and the temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1121–1129, 2006     

Effect of spinning conditions on the structure and properties of PAN fibers containing nano‐hydroxyapatite

Spinning conditions for nano‐hydroxyapatite‐containing precursor polyacrylonitrile (PAN) fibers have been developed and their effects on the structure and properties of nanocomposite PAN fibers have been assessed. The precursor PAN fibers prepared under the developed conditions are characterized by high strength, with their total pore content being at a level of 0.25 cm³/g. After carbonization, these fibers are designed for use as implants that support and stimulate the process of bone reconstruction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2881–2888, 2006     

Structure–property relationships for sulfonated poly(butylene terephthalate)

Structure–property relationships have been developed for sulfonated poly(butylene terephthalate) copolymers. The compositional variables investigated were sulfonate content, molecular weight, and polymer endgroup composition, and the fundamental polymer properties evaluated were melt viscosity, crystallization kinetics, and impact strength. It was found that all compositional variables significantly affect all of the polymer properties of interest. The most interesting effect is the influence of polymer endgroup composition on polymer properties. The trends indicate that the carboxylic acid endgroups form intermolecular interactions with sodium sulfonate groups, resulting in a decrease in the strength of intermolecular ionic interactions between sodium sulfonate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4662–4771, 2006