Studies on LDPE-cyanoethylated lignocellulosics blends using epoxy functionalized LDPE as compatibilizer

Rubberwood flour and cellulose have been plasticized by cyanoethylation and then blended with low-density polyethylene (LDPE). A small quantity of epoxy functionalized polyethylene i.e., polyethylene-co-glycidyl methacrylate (PEGMA) has been added to further enhance the mechanical properties. The mechanical properties were measured according to the standard ASTM methods. SEM analysis was performed for both fractured and unfractured blend specimens. The mechanical properties were improved by the addition of PEGMA compatibilizer. LDPE blends with cyanoethylated wood flour (CYWF) showed higher tensile strength and modulus than cyanoethylated cellulose CYC-LDPE blends. However CYC-LDPE blends exhibited higher relative elongation at break values as compared with the former. The TGA analysis showed lowering of thermal stability as the filler content is increased and degradation temperature of LDPE is shifted slightly to lower temperature. DSC analysis showed loss of crystallinity for the LDPE phase as the filler content is increased for both types of blends. Dielectric properties of the blends were similar to LDPE, but were lowered on adding PEGMA. (c) 2006 Wiley Periodicals, Inc.

Miscibility of poly(phenyl acrylate) with acrylonitrile/styrene copolymers

The Blase transition and phase behavior of blends of poly(pheny1 acrylate) with poly(acrylonitri1eco-styrene) was studied by differential scanning calorimetry. It was found that poly(pheny1 acrylate) is miscible with poly(acrylonitri1e-co-styrenes) within a specific range of copolymer composition. The segmental interaction parameters were estimated and found to be positive for all three pairs. The miscibility in thissystem appears to be the consequence of the intramolecular repulsion between styrene and acrylonitrile units.

Dilute solution properties of methyl methacrylate—acrylonitrile copolymer (MA2)

This article deals with studies of the dilute solution properties of methyl methacrylate-acrylonitrile (MMA-AN) copolymer of 0.415 mole fraction (mf) of acrylonitrile composition. Mark—Houwink parameters for this copolymer have been evaluated in acetonitrile (MeCN), 2-butanone (MEK), dimethyl formamide (DMF), and γ-butyrolactone (γ-BL). The Mark-Houwink exponent a in all four solvents at all temperatures is larger than the corresponding values of the parent homopolymers. The solvent power is in the order of DMF < γ–BL < MEK < MeCN; [η] decreases with an increase in temperature, which is behavior characteristic of polymers in good solvent. The unperturbed dimensions (K0) values, obtained by the Stockmayer–Fixman method, are lower than those for the parent homopolymers and depend on solvent as well as temperature. The solute—solvent interaction parameter X1 values are close to 0.5; X1 is independent of temperature. The excess interaction parameter XABvalues are negative. The results for this copolymer system in regard to low second virial coefficient A2, large X1, and high a values suggest that the large extension of these copolymer chains is due to the unusual short-range interactions.

Hollow hemisphere and microcapsules of nonionic copolymer

Hemispherical colloidal nanowells or microwells with hollow interiors are becoming increasingly important for the encapsulation of functional materials. There has been rapid progress to develop new methods to obtain such structures. In this work, we present emulsification approach to generate hemisphere and microcapsules of biocompatible organic polymer. The precise control over the size is exhibited by applying variable vortex effect. The hemispheres and microcapsules of a copolymer (BPVA-PVA) were characterized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). These structures were used for loading of hydrophilic molecules and submicron colloidal particles to demonstrate their potential application. The introduction of hydrophobic groups on poly(vinyl alcohol) was crucial to obtain these structures.

Effect of dynamical asymmetry on the viscosity of a random copolymer melt

The variation of the viscosity as a function of the sequence distribution in an A-B random copolymer melt is determined. The parameters that characterize the random copolymer are the fraction of A monomers f, the parameter lambda which determines the correlation in the monomer identities along a chain and the Flory chi parameter chi(F) which determines the strength of the enthalpic repulsion between monomers of type A and B. For lambda>0, there is a greater probability of finding like monomers at adjacent positions along the chain, and for lambda<0 unlike monomers are more likely to be adjacent to each other. The traditional Markov model for the random copolymer melt is altered to remove ultraviolet divergences in the equations for the renormalized viscosity, and the phase diagram for the modified model has a binary fluid type transition for lambda>0 and does not exhibit a phase transition for lambda<0. A mode coupling analysis is used to determine the renormalization of the viscosity due to the dependence of the bare viscosity on the local concentration field. Due to the dissipative nature of the coupling. there are nonlinearities both in the transport equation and in the noise correlation. The concentration dependence of the transport coefficient presents additional difficulties in the formulation due to the Ito-Stratonovich dilemma, and there is some ambiguity about the choice of the concentration to be used while calculating the noise correlation. In the Appendix, it is shown using a diagrammatic perturbation analysis that the Ito prescription for the calculation of the transport coefficient, when coupled with a causal discretization scheme, provides a consistent formulation that satisfies stationarity and the fluctuation dissipation theorem. This functional integral formalism is used in the present analysis, and consistency is verified for the present problem as well. The upper critical dimension for this type of renormaliaation is 2, and so there is no divergence in the viscosity in the vicinity of a critical point. The results indicate that there is a systematic dependence of the viscosity on lambda and chi(F). The fluctuations tend to increase the viscosity for lambda<0, and decrease the viscosity for lambda>0, and an increase in chi(F) tends to decrease the viscosity. (C) 1996 American Institute of Physics.

Photoinitiating capabilities of vinyl polyperoxides and metamorphosis of block-into-block copolymer

This article describes the first comprehensive study on the use of a vinyl polyperoxide, namely poly(styrene peroxide) (PSP), an equimolar alternating copolymer of oxygen and styrene, as a photoinitiator for free radical polymerization of vinyl monomers like styrene. The molecular weight, yield, structure and thermal stability of polystyrene (PS) thus obtained are compared with PS made using a simple peroxide like di-t-butyl peroxide. Interestingly, the PS prepared using PSP contained PSP segments attached to its backbone preferably at the chain ends. This PSP-PS-PSP was further used as a thermal macroinitiator for the preparation of another block copolymer PS-b-PMMA by reacting PSP-PS-PSP with methyl methacrylate (MMA). The mechanism of block copolymerization has been discussed. (C) 1996 John Wiley & Sons, Inc.

Electrical and Optical Properties of Diketopyrrolopyrrole-Based Copolymer Interfaces in Thin Film Devices

Two donor acceptor diketopyrrolopyrrole (DPP)-based copolymers (PDPP-BBT and TDPP-BBT) have been synthesized for their application in organic devices such as metal-insulator semiconductor (MIS) diodes and field-effect transistors (FETs). The semiconductor-dielectric interface was characterized by capacitance-voltage and conductance-voltage methods. These measurements yield an interface trap density of 4.2 x 10(12) eV(-1) cm(-2) in TDPP-BBT and 3.5 x 10(12) eV(-1) cm(-2) in PDPP-BBT at the flat-band voltage. The FETs based on these spincoated DPP copolymers display p-channel behavior with hole mobilities of the order 10(-3) cm(2)/(V s). Light scattering studies from PDPP-BBT FETs show almost no change in the Raman spectrum after the devices are allowed to operate at a gate voltage, indicating that the FETs suffer minimal damage due to the metal-polymer contact or the application of an electric field. As a comparison Raman intensity profile from the channel-Au contact layer in pentacene FETs are presented, which show a distinct change before and after biasing.

Studies of moisture induced crosslinking in a novel vinyl ether maleic anhydride copolymer

A novel vinyl ether, 2,2-dimethyl-4-vinyioxymethyl-1,3-dioxol (DMVMD), that has a dimethyl ketal protected vicinal diol functionality was synthesizied from readily available starting materials, such as glycerol, acetone and acetylene. Copolymerisation of DMVMD with maleic anhydride (MAH) in various molar ratios was carried out using a free radical initiator. The composition of the copolymer was established by conductometric titration, and was found to be 1:1 irrespective of the monomer feed composition thus establishing its alternating nature. The copolymer formed clear free standing films upon solvent casting which became insoluble upon prolonged exposure to ambeint atmosphere. The insolubility is ascribed to moisture induced crosslinking. A plausible mechanism for the crosslinking involves the hydrolysis of some of the anhydride groups, followed by acid catalysed deketalization, and then by the reaction of the alcoholic groups, thus generated, with the residual anhydride to give ester crosslinks. This hypothesis was confirmed both by model reactions and insitu FT-IR studies.

Mesoporous MnO2 synthesized by using a tri-block copolymer for electrochemical supercapacitor studies

Mesoporous MnO2 is prepared from KMnO4 by using a tri-block copolymer, namely, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) as a reducing as well as a structure-directing agent. The as synthesized MnO2 samples are poorly crystalline with mesoporosity having pore diameter between 8 and 40 nm. BET surface area as high as 273 m(2) g(-1) is obtained. By heating, the poorly crystalline MnO2 turns into a well crystalline form at 400 degrees C with nanorod morphology. However, the surface area decreases for the heated samples. Samples of MnO2 prepared by varying the ratio of KMnO4 and the copolymer, and also the heated samples are subjected to electrochemical characterization for supercapacitor studies. High specific capacitance values on mass basis are obtained for the as prepared mesoporous MnO2 samples. (C) 2011 Elsevier Inc. All rights reserved.

On the formation of poly(ethyleneoxide)-poly(vinylalcohol) blends

Poly(ethyleneoxide)-poly(vinylalcohol) blends were prepared and characterized using thermal, spectroscopic and structural methods, By all indications the blends appear to be microscopically inhomogeneous with no strong interpolymer bonding. The high degree of crystallinity in PEO regions induces a significant degree of ordering in neighbouring PVA regions, as evident from thermal properties. PVA obtained from solvent evaporation exhibits an irreversible endothermic transition which could be order-disorder type. Both IR and NMR spectroscopies also suggest the presence of subtle structural ordering influence of PEO on PVA. It is found to be possible to prepare self supporting films of the blends which consists of fine dispersion of PEO and PVA in each other. (C) 1999 Elsevier Science Ltd. All rights reserved.

Solution grafting of maleic anhydride onto polyethylene and compatibilization of polyetylene-nylon blends

Maleic anhydride (MAH) has been grafted onto high density polyethylene (HDPE) with benzoyl peroxide (BOP) initiator in toluene solution. Maximum degree of grafting (12%) without crosslinking has been obtained using MAH/HDPE and BOP/HDPE weight ratios of 1.0 and 0.15 respectively, at 110 degrees C. The HDPE-g-MAH compatibilizer is found to drastically reduce the dispersed phase size and also to produce homogeneous blends for relatively low concentrations of dispersed phase in HDPE/nylon blends. Addition of this compatibilizer results in increase of tensile strength and modulus with increasing nylon content of HDPE/nylon blends, while the opposite is found for the blends without any added compatibilizer.

Spectral, thermal and electrical properties of poly(o- and m-toluidine) PVC blends prepared by solution blending

Poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends with polyvinylchloride (PVC) of five different compositions have been prepared by solution blending. The POT-PVC and PMT-PVC blends were prepared using THF as a solvent in which POT-HNO3, PMT-HNO3 bases and PVC are soluble. The blends have been characterized by spectral, thermal and electrical measurements. The results indicate the formation of blends at all the compositions presently studied. The thermal stability of the POT-PVC and PMT-PVC blends is higher than that of POT-HNO3 and PMT-HNO3 salts, respectively. Using the present method, POT/PMT can conveniently be blended with 30% wt/wt of PVC without significant loss in its conductivity. (C) 1998 Elsevier Science Ltd. All rights reserved.

Polymerization of pyrrole and processing of the resulting polypyrrole as blends with plasticised PVC

Polypyrrole was synthesized by chemical oxidation of pyrrole in water containing various sulphonic acids like toluene sulphonic acid (TSA), sulphosalicylic acid (SSA), and camphor sulphonic acid (CSA), as well as a combination of each sulphonic acid with sodium dodecyl benzene sulphonate (NaDBS) to investigate the effect of doping on conductivity, yield, and processability of the conducting polymer. Free-standing blend films of polypyrrole and plasticized polyvinyl chloride (PVC) were obtained by casting an homogeneous suspension of the two polymers in tetrahydrofuran. The maximum conductivity of the blend film is similar to 0.3 S/cm, corresponding to a weight fraction of 0.16 w/w polypyrrole. The blend film is semiconducting in the range 300-10 K. A TG-DTA scan indicates the blend film to be amorphous with a stepwise decomposition process similar to pristine PVC. The choice of a dual dopant system during synthesis and the plasticised polymer during subsequent processing were keys to obtaining homogeneous high-quality films. (C) 2001 John Wiley & Sons, Inc.

Synthesis of nanocomposites of Ni-Zn ferrite in aniline formaldehyde copolymer and studies on their pyrolysis products

Synthesis of nanoparticles of Ni-Zn ferrite dispersed in aniline formaldehyde copolymer using a room temperature route and the effect of heat treatment on these samples were studied using XRD, FTIR spectroscopy, Fe-57 Mossbauer spectroscopy and TEM microscopy. The results show the formation of nanosized particles of Ni-Zn ferrite in the polymer matrix at room temperature. On pyrolysis, the Ni-Zn ferrite phase persists up to 500 degreesC. However, heating of composites to 700 degreesC results in the partial reduction of the spinet ferrite leading to the formation of Ni-Fe alloy under ambient conditions and complete reduction of the alloy on heating in inert atmosphere. (C) 2003 Elsevier B.V. All rights reserved.

Use of maleic anhydride-grafted polyethylene as compatibilizer for HDPE-tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol-plasticized and in unplasticized states was blended with high-density polyethylene (HDPE) using HDPE-g-maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact-fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch. (C) 2001 John Wiley & Sons, Inc.