All issues / Volume 3 (2009) / Issue 5 (May)
This is an editorial article. It has no abstract.
Physicochemical and electrochemical characterization of battery separator prepared by radiation induced grafting of acrylic acid onto microporous polypropylene membranes
N. K. Goel, Y. K. Bhardwaj, R. Manoharan, V. Kumar, K. A. Dubey, C. V. Chaudhari, S. Sabharwal
Vol. 3., No.5., Pages 268-278, 2009
Vol. 3., No.5., Pages 268-278, 2009
Mutual radiation grafting technique was used to graft acrylic acid on micrometer thick micro-porous polypropylene membrane using high-energy gamma radiation. Grafting could not be achieved in aqueous acrylic acid solution. The presence of Mohr’s salt effectively retarded the homopolymerization of acrylic acid but did not lead to grafting enhancement. Mohr’s salt in presence of acids was found to be effective in enhancing the grafting yield. Contact angle measurement studies of the grafted and radiation treated polypropylene showed that initial grafting as well as radiation treatment of poly(propylene) in aqueous medium and in presence of Mohr’s salt enhances its affinity towards the grafting solution. The enhancement in the polar component of surface energy of treated polypropylene membrane is the primary cause of grafting enhancement. The membranes grafted to an extent of ~20% were found to perform comparably with the battery separator presently being used by battery industry.
Porous poly(acrylamide) was synthesized using calcium carbonate microparticles and subsequent acid treatment to remove the calcium carbonate. Methylenebisacrylamide and ammonium persulfate/sodium metabisulfite were used as crosslinking agent and redox initiator, respectively. The porous structure of resulted hydrogels was confirmed using SEM micrographs. The effect of methylenebisacrylamide concentration and calcium carbonate amount on the swelling of the hydrogels was investigated. The results showed that the effect of methylenebisacrylamide and calcium carbonate variables on the swelling is reverse. The hydrogels were subsequently utilized for the loading of potassium nitrate. Potassium nitrate as active agent was loaded into hydrogels and subsequently the release of this active agent was investigated. In these series of investigation, the effect of content of loading, methylenebisacrylamide and calcium carbonate amount on the release of potassium nitrate from hydrogels was investigated.
Poly(carboxylic acid)-polysaccharide compositions have been found suitable for obtaining drug formulations with controlled release, most formulations being therapeutically efficacious, stable, and non-irritant. The influence of the characteristics of the aqueous solutions from which the polymer matrix is prepared (i.e. the total concentration of polymer in solutions and the mixing ratio between the partners, hydroxypropyl cellulose, HPC and maleic acid-alternating-styrene copolymer, MAc-alt-S) on the kinetics of some drugs release in acidic environment (pH = 2) has been followed by ‘in vitro’ dissolution tests. It has been established that the kinetics of procaine hydrochloride release from HPC/MAc-alt-S matrix depends on its composition; the diffusion exponent, n is close to 0.5 for matrices where one of the components is in large excess and n~0.02 for middle composition range. The lower value of diffusion exponent for middle composition range could be caused by the so called ‘burst effect’, therefore the kinetic evaluation is difficult.
Pyrolytic carbon black (PCB) made from used tires was used in ethylene-propylene-diene copolymers (EPDM). The microstructure of PCB was characterized by scanning electron microscopy (SEM). PCB was compounded with EPDM to prepare EPDM vulcanizates. The effects of PCB on the processing properties of EPDM compounds and the mechanical properties of vulcanizates were investigated and compared with other traditional fillers such as semi-reinforcing furnace black (N774), light calcium carbonate (CaCO3) and thermal black (N990). At the same time, the rheological behavior of EPDM compounds filled with different fillers was characterized by capillary rheometrics. The SEM photos showed that the particle shape was quiet different from that of CaCO3 and N990, it was similar to that of N774. The primary particle size was smaller than that of N774, but the aggregate size of PCB was larger than that of N774. The effect of PCB on the processing properties of EPDM compounds was similar to that of other fillers. Among the four fillers, PCB imparted EPDM compounds with higher Mooney viscosity. With the increase of filler content, the scorch time and optimum curing time of EPDM compounds changed little. The reinforcing effect of PCB was similar to that of N990, but inferior to that of N774. With the increase of PCB content, tensile strength, tear strength, and modulus at 100% elongation of EPDM vulcanizates increased significantly. When EPDM was filled with 50 phr PCB, the tear strength of EPDM vulcanizates increased by 3 times, compared with that of EPDM gum vulcanizates. The appearance of EPDM extrudate filled with PCB was coarser than that of other fillers.
Chitosan/Na+-montmorillonite/multi-walled carbon nanotubes (CTS/MMT/MWCNTs) nanocomposite films were prepared by a simple solution-evaporation method. The effects of MMT and MWCNTs on mechanical properties of the nanocomposite films were investigated. The results indicate that the simultaneously introduced MMT and MWCNTs into CTS film could greatly improve the mechanical properties. The Young’s modulus of the CTS film is increased about 50% as 1.0 wt% MMT and 1.0 wt% MWCNTs are introduced. The MMT could compensate the negative effect of MWCNTs on elongation at break of the CTS film. The highest elongation at break is obtained when the contents of MMT and MWCNTs are 0.5 and 0.5 wt%, respectively. Formation of the MMT…CTS…MWCNTs subassembly may be responsible for the observed synergistic effect of MMT and MWCNTs on mechanical properties of the CTS film.
Ethylene-octene elastomer (POE) and ethylene-octene elastomer grafted maleic anhydride (POEgMAH) toughened nanocomposites of polyamide 6/polypropylene (PA6/PP) containing 4 wt% organophilic modified montmorillonite (MMT) were produced by melt compounding followed by injection moulding. The PA6/PP composition was kept constant (PA6/PP = 70/30 parts) while the elastomer (either POE or POEgMAH) content varied between 5 and 20 wt%. PP grafted maleic anhydride (PPgMAH) was used to compatibilize the blend system. The impact strength of the nanocomposite system was examined by the conventional Izod impact test at room temperature (RT). In addition, linear elastic fracture mechanics (LEFM) approach was used to study the fracture response of the notched three point bending type specimens at room temperature (RT) and –40°C. Fracture surfaces of the broken specimens were examined using scanning electron microscopy. The results show that while POEgMAH can remarkably improve the compatibility between PA6 and the elastomer thus increasing the toughness, the unmodified POE has less significant contribution to PA6/PP/organoclay toughness. Elastomer domains of POEgMAH show a finer and more uniform dispersion than that of POE in the PA6/PP/organoclay matrix. It is also observed that the toughness increased with the increasing elastomer concentration for both unmaleated and maleated POE.
The present paper aims to study the possibility to modify the properties of poly(vinyl alcohol) (PVA) hydrogels prepared in the presence of different salt types (Na2SO4, NaCl and NaNO3) in order to extend the nature of the salts already used in obtaining films or gels, to expand their concentration domains and to explain the increase of film strain, concomitantly with the increase of their crystallinity. The morphology of the PVA based hydrogels has been studied by Scanning Electronic Microscopy (SEM), the interaction between the PVA macromolecular chains and salts has been determined by Fourier Transform Infrared Spectroscopy (FTIR), while the mechanical properties of the cryogels have been investigated by oscillatory dynamic mechanical measurements. The gels swelling in water have been monitored by gravimetric method in order to evidence the alteration of the PVA cryogel properties such as crystallinity and porosity determined by the salt addition to the initial PVA aqueous solution. The data reported show that the ions present in the PVA solution influence the interaction between PVA-water and PVA-PVA chains; their influence on the salt-based PVA hydrogels follow the Hofmeister lyotropic series.