Preparation and characterization of nanocomposites based on thermoplastic elastomers from rubber–plastic blends

In the present work, thermoplastic elastomer (TPE)–clay nanocomposites (TPN) based on different rubber–plastic blends from ethylene–octene copolymer [Engage]–Polypropylene and brominated poly(isobutylene‐co‐paramethyl styrene)–nylon 6 were prepared by melt blending. Hexadecyltrimethylammonium bromide and octadecyl amine‐modified sodium montmorillonite were used as organoclays. The nanocomposites were prepared by adding the nanoclay separately into the rubber and plastic phases. The TPNs were characterized with the help of transmission electron microscopy (TEM) and X‐ray diffraction. The X‐ray diffraction peaks observed in the range of 3–10° for the modified clays disappeared in the thermoplastic elastomeric nanocomposites. TEM photographs showed exfoliation and intercalation of the clays in the range of 20–30 nm in the particular phase where the clay was added. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus was observed on incorporation of the nanoclays in the rubber phase of TPN. When the nanoclay was added to the plastic phase, the mechanical reinforcement is comparatively poorer due to partial destruction of the crystallinity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1645–1656, 2006     

Structural development in cycloolefin copolymers under uniaxial elongational flow

Development of structures in new cycloolefin copolymers (COCs) of ethylene–norbornene (E–NB) and ethylene–tetracyclododecene (E–TD) of different NB/TD compositions were investigated under uniaxial elongational flow. For E–NB copolymer, which has multiblock sequences, a shoulder in WAXD at 0.76 nm was evident besides its amorphous halo, and the relative intensity of the peak increased with increasing comonomer content (NB). The appearance of a new peak for E–TD copolymer, and a relatively higher intense peak for E–NB copolymer at the same position of 0.76 nm, indicated that local ordering of the segments occurred when the COC was subjected to uniaxial flow. A lower comonomer composition of elongated COC, at a constant Hencky strain rate, exhibited two T_g values, whereas a higher composition showed a single T_g. Both local ordering and segmentization occurred in low comonomer content COCs but only local ordering occurred in higher comonomer content COCs. Both the shear viscosity and roll processing experiments exhibited similar phenomena of segregation. A model is proposed to illustrate the structure of COC after uniaxial elongation/deformation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3421–3427, 2004     

Influence of various crosslinking systems on the mechanical properties of gas phase EPDM/PP thermoplastic vulcanizates

Dynamically cured thermoplastic elastomers or thermoplastic vulcanizates (TPVs) are widely used nowadays for their unique characteristics. In this paper, gas phase ethylene–propylene–diene terpolymer (GEPDM)/Polypropylene (PP) TPVs with various crosslinking systems have been extensively studied to optimize the curative level in each crosslinking system with special reference to their mechanical properties. Optimized systems were compared for heat aging, recyclability, crosslink density, morphology studies, and dynamic mechanical analysis. Crosslinking by peroxide in the presence of triallyl cyanurate as a coagent gives best overall performance with reference to excellent heat aging behavior, tension set, and compatibility between GEPDM and PP. Conventional EPDM/PP system was also compared with GEPDM/PP system. GEPDM/PP system was found to exhibit better behavior in all respects. Significant correlations were obtained between delta torque values obtained from Moving Die Rheometer and modulus or cross link density of TPVs irrespective of the nature of crosslinking agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5463–5471, 2006     

Magnetic particles for sugar separation from sulphuric acid solution generated during nano‐crystalline cellulose production

Nano‐crystalline cellulose (NCC) is a renewable material having different applications ranging from drug delivery to a reinforcing filling agent in polymer synthesis. Concentrated sulphuric acid is used to hydrolyze cellulosic biomass to obtain NCC. Manufacturers are keen to reuse the diluted acid solution left after the process. However, the presence of mono and oligosaccharides makes it unsuitable for repeated use. About 99 % of these compounds have been successfully separated from the acid solution by employing NaOH‐treated magnetic particles developed during this investigation. It has been observed that by NaOH treatment, zeta potential of the magnetic particles could be increased from +11 mV to +37.5 mV; correspondingly, sugar removal efficiency was increased from 23.04 % to more than 99 %. Thus a direct correlation between the change in zeta potential of the particles and sugar separation efficiency has been observed.     

信号调制系统实现角位移测量（英文）

采用基于定时器LM555的非稳态多谐振荡器和通用频数转换设计了一种变面积式电容传感器信号调制系统用于角位移测量。变面积式电容器连接在基于定时器的非稳态电路内,其角位移的变化引起电容的变化,进而引起定时器电路输出时间周期的变化。定时器电路输出波形的时间周期与电容呈线性关系,因而与角位移也是线性关系。定时器输出经通用频数转换器进一步处理后可用于测量。实验结果显示,时间周期与角位移在0-180°范围内呈线性关系,将不确定度与平均时间周期相关联,即为平均标准差,亦称为标准误差,其值为±0.023μs。该测量系统使用简单,可用于电子和工业仪器中。     

Mechanical properties and morphology of PBT/FE blends

The mechanical properties such as tensile properties and Izod impact strength of melt compounded poly (butylene terephthlate)(PBT)/Fluorocarbon terpolymer elastomer (FE) blends at FE concentration from 0 to 0.26 volume fraction were studied. With increase in the FE concentrations the tensile properties decreased while the impact strength increased. Good dispersion and adhesion of FE with major phase PBT was shown by the morphological studies. Crystallinity of PBT and interphase adhesion influenced the tensile properties. Use of simple models relating normalized relative tensile parameters where the data were divided by the crystallinity of PBT in the blends and in the matrix, respectively, supported the interphase adhesion. The concentration and the interparticle distance of the dispersed phase FE influenced the impact toughening.     

Green fire retardant finishing and combined dyeing of proteinous wool fabric

Flame retardancy was imparted to a scoured and bleached, proteinous woollen textile by using banana pseudostem sap, an ecofriendly waste agricultural product, at different pH levels. The flame retardancy characteristics of both the control and the treated fabrics were analysed in terms of the limiting oxygen index and the vertical flammability measurement. Thermal degradation and fire retardancy mechanisms were studied using thermogravimetry, scanning electron microscopy, and energy dispersive X‐ray analysis. Moreover, the charring mechanism of both the control and the banana‐pseudostem‐sap‐treated fabrics with varying pH was analysed and reported in detail. The wool fabric was also dyed with CI Acid Blue 25 using banana pseudostem sap as well as water as the medium. The fabric dyed with the banana pseudostem sap medium at pH 5.5 showed more colour exhaustion, colour strength, and thermal stability compared with the control wool fabric. The mechanism by which superior fire retardancy and colour strength are imparted to the woollen textile by the application of banana pseudostem sap is proposed.     

Novel organic–inorganic composite material as a cation exchanger from a triterpenoidal system of dammar gum: synthesis,characterization and application

A pioneer study has been conducted to synthesize novel hydrogel starting from a non-cellulosic raw material, gum dammar-a triterpenoidal system, and then converting this hydrogel into an organic–inorganic composite zirconium-based ion exchanger. Gum dammar was cross-linked with polyacrylamide zirconium (IV) iodo-oxalate [Gd-cl-poly(AAm)-Zr (IV) iodo-oxalate] by incorporating inorganic precipitates into the polymeric mixture. The polymeric mixture was synthesized using gum dammar (Gd), acrylamide (AAm), N, N′-methylene-bis-acrylamide (MBA) and potassium persulphate (KPS). The reaction conditions for synthesis of hydrogel and ion exchanger such as time (120 min), temperature (70 °C), solvent (4 mL), concentration of monomer (12.97 × 10^?3 mol/L), initiator (1.48 × 10^?4 mol/L), cross-linker (4.22 × 10^?4 mol/L) and ratio of zirconium oxychloride (0.1 M), potassium iodate (0.1 M) and oxalic acid (0.1 M) in ratio 2:3:2 were optimized to obtain maximum ion exchange capacity (2.02 meq/g). The morphology and structure of hydrogel and ion exchanger were studied using FTIR, SEM, XRD and TGA/DTA/DTG. The SEM study was followed by energy dispersive spectroscopy for elemental analysis. The ion exchanger was quite stable in various acids and bases at low concentration but it completely dissolved in acids and bases at high concentrations. Distribution studies showed that the synthesized ion exchanger had high selectivity for Pb²⁺ ions. Thus, the polymeric-inorganic hybrid material showed integration of both inorganic and organic characteristics within the composite material.