Preparation of modified sodium lignosulfonate hydrogel–silver nanocomposites

In this article, modified sodium lignosulfonate (MSLS) hydrogel particles were prepared using sodium lignosulfonate as starting material. The hydrogel particles exhibit a reversible property transformed between the two states of macrohydrogel and microhydrogel by ultrasonic dispersion and vacuum drying. Using this property, highly stable and uniformly dispersed silver nanoparticles (AgNPs) have been prepared via in situ reduction of silver ions (silver nitrate) in the microhydrogel aqueous dispersion with sodium borhydride. The hybrid microhydrogel with AgNPs was transformed into MSLS hydrogel–silver nanocomposites by drying under vacuum at 40°C. X‐ray diffraction, ultraviolet–visible (UV–vis) spectrophotometry, Fourier transform infrared spectra, atomic absorption spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to characterize the composite system. The results show that the size of spherical silver nanoparticles incorporated in the hydrogel framework is about 10 nm. POLYM. COMPOS., 34:860–866, 2013. © 2013 Society of Plastics Engineers     

Magnetic and electric responsive hydrogel–magnetic nanocomposites for drug‐delivery application

Magnetic and electrically responsive hydrogel networks were developed for drug‐delivery applications. The hydrogel matrices were synthesized by the polymerization of acrylamide monomer in the presence of carboxymethylcellulose (CMC) or methylcellulose (MC) with N,N‐methylenebisacrylamide, a crosslinker with the redox initiating system ammonium persulfate/tetramethylethylenediamine. The magnetic nanoparticles were generated throughout these hydrogel matrices by an in situ method by the incorporation of iron ions and their subsequent reduction with ammonia. A series of hydrogel–magnetic nanocomposites (HGMNCs) were developed with various CMC and MC compositions. The synthesized HGMNCs were characterized with spectral (Fourier transform infrared and ultraviolet–visible spectroscopy), X‐ray diffraction, thermal, and microscopy methods. These HGMNCs contained iron oxide (Fe₃O₄) nanoparticles with an average particle size of about 22 nm, as observed by transmission electron microscopy. The dielectrical properties of the pure hydrogel (HG); the hydrogel loaded with iron ions, or the hydrogel iron‐ion composite (HGIC); and the HGMNCs were measured. These results suggest that HGMNCs exhibited higher dielectric constants compared to HG and HGICs. The curcumin loading and release characteristics were also measured for HG, HGIC, and HGMNC systems. These data revealed that there was a sustained release of curcumin from HGMNCs because of the presence of magnetic nanoparticles in the hydrogel networks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polyurethane–polypropylene blends

Five series of blends were obtained by mixing five polyurethanes (PUR), based on poly-propyleneoxide, MDI, and butanediol, with polypropylene (PP). The structure of PUR was varied by varying soft segment length (MW = 1000 and 2000) and soft segment concentration (50, 60, and 70%). It has been shown that interaction between PUR and PP was better in the case of PUR with the polyol of MW = 1000. The addition of lower molecular weight PUR produced an easy flowing material in the molten state, comparable with the “control rheology PP.” The morphology of the blends changed with PUR concentration. At 30% PUR the dispersed phase tended to agglomerate in the form of long cylinders. Mechanical properties generally were affected by the change of morphology.     

Cellulose–copolyamide 6,69 blends

In a previous work [J. Polym. Sci. Polym. Phys., 32 , 1437 (1994)], a technique for the preparation of cellulose-polyamide 66 (PA66) blends was proposed. It was shown that the crystallization of PA66 is responsible for the phase separation and, furthermore, for the morphology of the domains in the blends. For this reason, the use of a quasi-amorphous polyamide, i.e., a random copolymer of units 6 and 69, instead of PA66, is now investigated. Cellulose-polyamide 669 (PA669) blends were prepared by a solution-precipitation process. A mixture of N-methylmorpholine-N-oxide and phenol (80/20 wt/wt) was used as a common solvent. Materials were precipitated whether in methanol or in water. The fibers obtained were characterized by scanning electron microscopy, mechanical spectroscopy, and tensile tests. It is shown that the morphology of these blends depends on the precipitation system and is a function of the different steps of processing of the blends. © 1996 John Wiley & Sons, Inc.     

Epoxy resin–polyethersulphone blends

A series of amine-cured epoxy resin systems and the blends of these containing up to 50% polyethersulphone (PES) were evaluated in terms of curing behavior, microstructure, and mechanical and dynamic mechanical thermal properties. The epoxy networks were based on a 2 : 1 mixture of triglycidyl-p-aminophenol and the polyglycidylether of a phenolformaldehyde novolac, and a curing agent of 3,3'-diaminodiphenylsulphone (DDS). The curing mechanism and the rate of curing were affected by the DDS and PES contents. Reaction between the epoxy resin and hydroxyl groups attached to PES was indicated in epoxy-rich formulations. Phase separation, evident in all the blends, was affected by the curing rate. Various blend morphologies were observed depending on the epoxy network/thermoplastic composition. Blending improved ductility and toughness-related properties, particularly at 20–40% PES contents, which corresponded to spinodal/co-continuous morphologies. Changes in glass transition behavior were attributed to possible variations in intermolecular free volume. © 1994 John Wiley & Sons, Inc.     

In vitro toxicity evaluation of hydrogel–carbon nanotubes composites on intestinal cells

Composite materials based on carbon nanotubes (CNT) and polymeric hydrogels have become the subject matter of major interest for use as carriers in drug delivery research. The aim of this study was to evaluate the in vitro cytotoxicity of the hydrogel–carbon nanotube–chitosan (hydrogel–CNT–CH) composites on intestinal cells. Oxidized CNT were wrapped with chitosan (CH), Fourier transform infrared (FT‐IR) analysis suggest that oxidized CNT interact with CH. Transmission electron microscopy (TEM) images show a CH layer lying around CNT. Chitosan wrapped CNT were incorporated to poly (acrylamide‐co‐acrylic acid) hydrogels. Swelling behavior in buffers at different pH were evaluated and revealed a significantly lower swelling when it is exposed to a acid buffer solution (pH 2.2). Mechanical properties were evaluated by measurements of elasticity and the material with CNT showed better mechanical properties. The incorporation and liberation of Egg Yolk Immunoglobulin from hydrogel–CNT–CH were also assessed and it revealed an improved performance. To evaluate the effect of these nanocomposites on cellular redox balance, intestinal cells were exposed to hydrogel–CNT–CH composites and antioxidant enzymes were assessed. Cytotoxicity and apoptosis were also evaluated. Hydrogel–CNT–CH composites induce no oxidative stress and there were no evidence of cytotoxicity or cell death. These preliminary findings suggest that hydrogel–CNT–CH composites show improved properties and good biocompatibility in vitro making these biomaterials promising systems for drug delivery purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41370.     

Mechanical properties of HDPE–PS–SEBS blends

Blends of high-density polyethylene (HDPE), polystyrene (PS), and an SEBS triblock copolymer were extruded, pelletized, and injection molded. The binary HDPE–PS blends exhibit very poor ductibility; however, addition of the SEBS block copolymer greatly improves this characteristic but with an accompanying loss in strength and modulus. The modified blends are very tough and have mechanical properties suitable for many end use applications. However, weld lines pose a problem and should be avoided with these blends.     

Studies on polymer blends. II. Butadiene–styrene copolymers and polybutadiene–polystyrene blends

The properties of butadiene–styrene copolymers and of polybutadiene–polystyrene blends were compared. Polybutadiene, polystyrene, and four copolymers having styrene contents of 20, 40, 60, and 80% were prepared. The copolymers were compared with blends having various styrene contents and prepared by means of latex blending and roll blending. Vulcanizates were prepared by three different curing methods, i.e., sulfur cure, peroxide cure, and radiation cure. The results of the benzene extraction of three vulcanizates showed that the polystyrene blended was not cured by any of the curing methods used. The properties of the vulcanizates of the copolymers were markedly different from those of the blends, i.e., in the case of the blends the properties showed a linear relationship with their blending ratio, while in the copolymers the properties showed a curvilinear relationship which had an inflection point at a styrene content of about 60%. From this phenomenon of the copolymers, it was proposed that the second-order transition point of styrene is the cause of the properties showing this peculiar point. From the results, it was found that the behavior of styrene in copolymers is essentially different from that in blends.     

Viscosities of ethylene–propylene–diene terpolymer blends in oil

Viscosities were obtained on oil solutions of two ethylene–propylene–diene terpolymers (EPDMs) and their blends. For the amorphous terpolymer with 59 mol% ethylene, intrinsic viscosities were constant between–10 and 40°C. The viscosities decreased rapidly at low temperature for blends of this material with as little as 20 wt % of a slightly crystalline EPDM with 79 mol% ethylene. Dynamic viscosity measurements on 1.0% solutions of blends likewise gave considerably smaller values at low temperature than measurements on an amorphous EPDM of similar molecular weight. The data are in agreement with the view that longer ethylene sequences that crystallize in the bulk polymer can organize in oil into ordered domains that interfere less with flow than the disordered amorphous polymer regions. © 1993 John Wiley & Sons, Inc.     

Partial miscibility of cellulose–polyacrylonitrile blends

Cellulose-polyacrylonitrile (PAN) blends have been prepared by the regeneration of 2% concentration solutions in dimethylformamide–NO₂ solvent. The blends are transparent when containing between 0 and 50% by weight of PAN. Dynamic mechanical measurements indicate a shift in glass transition temperature T_g of PAN for the blends, suggesting partial miscibility between cellulose and PAN. Experimental density values larger than those predicted theoretically are also in agreement with this conclusion.     

Stress–strain behavior of polyolefin blends

As part of a study on reuse of plastics as blends, the yield tensile strength, elongation at break, and the modulus of melt blends of low-density polyethylene, high-density polyethylene, and polypropylene have been studied over the entire ternary composition range. The modulus and strength are nearly monotonic functions of blend composition. The contribution of the pure components to these properties is roughly additive. The elongation at break is a more complex function of composition in that minima are observed near the center of the triangular composition diagram and on each of the three binary legs. The response is nearly symmetrical along two of the binary legs but is skewed toward high-density polyethylene for blends of high- and low-density polyethylene. The deterioration of elongation produced by blending is much less severe for polyolefins than observed for other blend systems. This, combined with the observed additivity of strength, make polyolefin blends mechanically superior to blends of other plastics found in wastes. This fact is interpreted in terms of compatibility and amorphous phase interactions which are likely for polyolefins. Modification of polyolefin blends by addition of a rubbery copolymer of ethylene and propylene produced large improvements in elongation at break for some compositions.     

Alkyd–epoxy blends as multipurpose coatings

The alkyd resins of three different compositions based on nahar seed oil (Mesua ferrea), phthalic anhydride, and maleic anhydride were synthesized by an alcoholysis method. These alkyd resins were blended with a commercially available epoxy resin (Araldite 250, Ciba Geigy, Mumbai, India) separately to study the performance of the blends as coatings. The morphology of the blends was studied with scanning electron microscopy. The drying time, gloss, flexibility, pencil hardness, adhesion, pressure test, and chemical resistance under different conditions were measured for this purpose. The thermal characteristics of the blends were also investigated by thermogravimetric analysis. The studies showed better performance of the blends with respect to the drying time, hardness, flexibility, gloss, pressure test, thermal stability, and chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 516–521, 2006     

Thermogravimetric analysis of polyurethane–polysulfone blends

Thermal decomposition of blends of a poly(ester urethane) and poly(ether sulfone) with or without poly(urethane sulfone), taken as a compatibilizing agent, was studied by thermogravimetric analysis under dynamic conditions. Theoretical mass loss curves were compared with experimental ones and it was found that the blends studied possessed lower thermal stability than the pure polymers, indicating the presence of interactions in the degradation process. The shifts between the theoretical and experimental curves became smaller as the amounts of polysulfone increased, confirming the thermal stabilisation effect of this polymer. The analysis of activation energy revealed, for both binary and ternary systems, that E_CR (T_max corresponding to the main decomposition stage of polysulfone) increased as the amount of this polymer increased and also the reaction order became zero. For the polyurethane decomposition stages and blending revealed no significant changes as far as activation energy and order of reaction were concerned. © 2002 Society of Chemical Industry     

Chemistry of miscible polycarbonate–copolyester blends

Blends of polycarbonate and the copolyester based on 1,4-cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids are known to be completely miscible. This study was concerned with various chemical events which may occur in this system, particularly during melt processing. Degradation reactions were studied by both TGA and dilute viscometry techniques, and some indications of component interaction were noted. The residual titanium catalyst from the copolyester formation was found to produce color formation by interaction with phenolic end groups in the polycarbonate and to promote interchange reactions. Both events could be suppressed by deactivation of the residual catalyst with appropriate additives. An indication of the extent of interchange reactions was obtained by following the crystallizability of the copolyester component using differential scanning calorimetry.     

Natural rubber–isotactic polypropylene thermoplastic blends

Thermoplastic elastomers, prepared by melt blending of natural rubber (NR) and isotactic polypropylene (PP) through a dynamic vulcanization technique, were developed during the later 1970s. However, they have certain drawbacks due to thermal degradation and higher molecular weight of NR. In the study reported here, NR was masticated to different levels prior its addition to isotactic polypropylene to improve the flow properties and to reduce the incompatibility resulting from molecular weight mismatch of NR/PP thermoplastic blends. Mixing energy curves of uncrosslinked blends and those of dynamically vulcanized blends crosslinked using different cure systems were compared. The mixing energy curves of blends containing NR of different molecular weight (M _n) and two grades of PP (injection and film grades) were also compared. Technological and processing properties of the dynamically vulcanized (sulphur and peroxide cure systems) and unvulcanized blends were compared with those of the samples containing unmasticated NR. The results indicated that a number average molecular weight in the range 4 × 10⁵ for NR increased the procoessability without significantly affecting the technological properties of NR/PP thermoplastic blends. Among the three cure systems studied Luperox 101 and dicumyl peroxide gave better technological properties than the sulphur‐cured samples. Two antioxidants, viz. quinoline (TDQ) and imidazole (MBI) type, were tried in NR/PP blends. It was found that TDQ imparts better aging resistance compared to MBI. The improvement in processability due to the reduction in molecular weight of natural rubber by mastication is more noticeable in the case of peroxide vulcanized blends compared to sulphur vulcanized samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2063–2068, 2004     

EVA–EPDM blends as cable insulant

Base materials for heat-resistant cable insulant have been developed from blends of ethylene vinyl acetate (EVA) copolymer containing 28% VA and ethylene propylene diene (EPDM) rubber. Different electrical, mechanical, and thermal properties of these blends have been studied extensively. Aging under different conditions has also been studied. The chemical and mechanical stability of these compositions has been assessed at the actual temperature range of application. Dielectric properties have been determined against varying temperature. These blends may be used as insulating materials having a temperature rating around 90–130°C, which is above the temperature rating (85–90°C) of heat-resistant insulation based on EPDM. © 1994 John Wiley & Sons, Inc.     

Mechanical relaxation in polycarbonate–polysulfone blends

Lexan polycarbonate and polysulfone P-1700 were blended to various weight percentages by dissolution in methylene chloride. The blended material was reclaimed in the form of evaporated thin films which were dried, ground, and molded. Low-frequency mechanical relaxation tests were run on specimens machined from this material as a function of composition and thermal treatment. In addition to the β-peak, a second peak, β′, was resolved in unannealed 75 wt/o P-1700 specimens. These results are presented and a possible interpretation is discussed and compared with previously proposed mechanisms.     

Investigation of rubber–rubber blends miscibility

Polybutadiene rubber, poly(styrene‐co‐butadiene) rubber, natural rubber, and their blends were investigated to estimate the degree of miscibility of components in the blends. The morphology of a rubber–rubber blend controls its rheological properties and glass transition behavior. Therefore, two different measuring techniques were used: rheological characterization of blends by the rubber process analyzer (RPA) and temperature modulated differential scanning calorimetry (TMDSC). To study the dependence of complex viscosity on blend composition, two commonly used empirical mixing rules were applied: the log‐additivity mixing rule and the quadratic mixing rule. Viscoelastic properties of the examined samples were described by mechanical and relaxation spectra. Since the RPA measurements cannot be performed in a wide frequency range, the experimental results cannot offer a complete overview. Also, the quantitative analysis using the differential of the heat capacity, dC_p/dT, versus the temperature signal from TMDSC did not allow to calculate the weight fraction of the interface for all types of the blends under investigation. However, the combination of the two techniques applied provided complementary information on blend morphology and rubber–rubber miscibility. POLYM. ENG. SCI. 46:1649–1659, 2006. © 2006 Society of Plastics Engineers.