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Polyurethane (PU) based pressure sensitive adhesive (PSA) commonly used in surgical dressing has been made by electron beam (e-beam) irradiation. In contact with biological substrate like skin, PSAs generally lose their adhesive strength due to very low moisture vapor transmission rate (MVTR). In the present study, effects of varying e-beam dose and different crosslinkers on the MVTR of the PU-PSA have been investigated. A comparative study of effects of different crosslinkers showed that PU-PSA with IPDI has the least while that with TAC has the highest gel content and crystallinity and a reverse trend was observed for the MVTR.

When Nylon 66 was irradiated by an optimum dose of e-beam in presence of polyurethane as impact modifierin combination with triallyl isocyanurate as cross-linker, a superior performance was observed for the irradiatednylon 66. Significant improvement of properties, such as hardness, tensile strength, flexural modulus and impactstrength was obtained on radiation processing of nylon 66 by e-beam. More interestingly, percent water absorptionof such irradiated nylon 66 was reduced substantially. Improvement of mechanical properties and reduction of waterabsorption of irradiated nylon 66 were due to the cross-linking of the polymer system. Increase of cross-linkingwith dose of e-beam was verified by the increased gel content at higher doses. Irradiated nylon 66 showed betterdimensional stability than those achieved with pristine nylon 66. The increase in dimensional stability may beattributed to reduction in crystallinity with increasing dose of e-beam as revealed by DSC studies.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 281-289, DOI:http://dx.doi.org/10.14429/dsj.64.7328

A hydrophobic composition for foldable intraocular lenses was developed by copolymerizing phenyl ethyl acrylate, phenyl ethyl methacrylate and butanediol diacrylate by gamma irradiation. Aqueous solution of heparin, a biocompatibilizer absorbed in hydroxyethyl methacrylate was added to the monomer mixture before irradiation to impart desired level of hydrophilicity and improved biocompatibility to the hydrophobic composition. Ketorolac tromethamine, an anti-inflammatory agent and L-glutathione, an antioxidant were added to the composition as functional additive for exhibiting improved performance while in use. Concentrations of monomers, biocompatibilizer and functional additives were optimized to develop an advanced material for foldable intraocular lenses. Transmittance, refractive index, Abbe number, hardness, tensile strength, flexibility and foldability were studied on the final composition. Scanning electron microscopic study, differential scanning calorimetric analysis, leachability and viscometry confirmed the permanent incorporation of additives into the polymer. Results of haemocompatibility, tissue implantation and cytotoxicity confirm that the biocompatibility of the base polymer was improved by incorporation of heparin.

Devices for medical application require materials to perform at the highest standard over an extended period of time, as many products may be stored more than a year before their use. The performance of such devices can be adversely affected, if the materials of construction they are made of loose their efficiency during storage. Therefore, material aging information is very important in order to ensure the product quality. The quality of the product can be evaluated either by doing the actual storage studies time to time or accelerated aging studies can be simulated in the laboratory to reduce the study time and to know performance of the product well in advance. The accelerated aging studies thus have immense importance before commercialization of any product. In the present study an attempt has been made to assess life time expectancy in terms of its performance of a microporous pressure sensitive adhesive (PSA) tape made of polyurethane (PU) acrylate by e-beam irradiation process. The accelerated agin...

The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66.

Isocyanate terminated polyurethane prepolymer, a ba se material for water curable polyurethane bandage was prepared from diphenylmethane diisocyanate and poly (propylene ox ide) glycol. In polyurethanes, the diisocyanate ac t as hard segment and provides dimensional stability, whereas the polyol which forms the soft segment gives elastomeric char acter. Due to its segmented structure, polyurethane’s with a wide range of phys ico-mechanical properties can be obtained by varyin g its monomers types and content. In this paper, the effect of different soft segment length on influencing the structure prop erty relationship of polyurethane prepolymer was studied. The soft segment length was varied by using poly (propylene oxide) glycol havi ng different molecular weight and also by blending two polyols having similar che mical composition but of different molecular weight . The formation of the prepolymer was investigated by Fourier transform in frared spectroscopy (FTIR). The results reveal that with increasing soft segment length, the weight average molecular weight and sto rage time of the prepolymer increases, whereas the Brookfield viscosity decreases due to higher content of soft segment. The curing time was found higher in prepolymer having longer s oft segments due to lower isocyanate content. With increasing molecular weigh t of the soft segment, the phase separation between the hard and soft segment increases due to which the prepolymer produce low T g. The tensile strength of the polyurethane film dec reases whereas percent elongation increases with increase in soft segment length. The findings of the study will be beneficia l for understanding the role played by soft segment length on tailoring the stru cture and ultimately the properties of isocyanate t erminated polyurethane prepolymer.

Polyurethane (PU)-based pressure-sensitive adhesive (PSA) has been manufactured by electron beam (e-beam) irradiation using urethane-acrylate. The effect of variation of e-beam dose and crosslinkers viz. triallyl cyanurate (TAC), triallyl isocyanurate, polymeric methylene diphenyl diisocyanate, carbodiimide-modified methylene diphenyl di-isocyanate, methylene diphenyl di-isocyanate, and isophorone di-isocyanate (IPDI) has been studied concerning the shrinkage, adhesion properties, and gel content of the PU-PSA. It was found that with increasing e-beam dose the shrinkage is increased up to 25 kGy, but remained constant thereafter with further increasing the dose up to 60 kGy. Similarly, with increasing concentration of crosslinkers from 2 to 6%, shrinkage is increased but beyond that there is no appreciable change. A comparative study of the effect of different crosslinkers on shrinkage, adhesion properties, and gel content of PU-PSA was carried out, and it was found that TAC leads to the maximum, while IP...

Polyurethane (PU) based pressure-sensitive adhesive (PSA) using monofunctional urethane acrylate (MFUA) and difunctional urethane acrylate (DFUA) has been cured using electron beam (e-beam) irradiation. The effect of varying e-beam doses on the adhesion properties viz. peel adhesion, shear adhesion and initial tack of PSA has been studied. Effect of various crosslinkers viz. methylene diphenyl di-isocynate (MDI), isophorone di-isocynate (IPDI) and triallyl isocynurate (TAIC) on adhesion properties as well as on moisture vapor transmission rate (MVTR) and gel content of the PSA has also been studied. It was observed that with increasing dose and concentration of crosslinkers all the adhesion properties viz. peel adhesion, shear adhesion strength and initial tack were increased and reached a plateau, and then a decline was observed with further increasing of the dose and crosslinkers concentration. Similarly, MVTR decreased and the gel content increased with increasing dose of electron beam.

This investigation highlights the processing of Nylon 66 and the incorporation of nano-silicate into the Nylon 66 polymeric matrix. Further, radiation modification of Nylon 66 and nano-silicate dispersed Nylon 66 was carried out in order to essentially alter the physicochemical properties of the material. A combination of both the above methods of processing and modifying the neat Nylon 66 polymeric matrix provides an interesting aspect for studying the resultant effect on the variation in properties of the composite material over the virgin polymer. There was a significant improvement of physicothermal and physicomechanical properties when Nylon 66-silicate nanocomposites were further modified under gamma radiation, which was confirmed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile and water absorption studies.

Polyurethane based pressure sensitive adhesive using monofunctional urethane acrylate and difunctional urethane acrylate has been made using electron beam irradiation. The effect of varying electron beam doses on the adhesion properties viz., peel adhesion, shear adhesion and initial tack has been studied. Effect of tackifier and crosslinkers viz., polymeric methylene diphenyl diisocynate, carbodiimide modified methylene diphenyl diisocynate and triallyl cynurate on adhesion properties as well as on moisture vapor transmission rate and gel content of the polyurethane based pressure sensitive adhesive has also been studied. It was found that with increasing dose, tackifier and crosslinkers concentration, all the adhesion properties viz., peel adhesion, shear adhesion strength and initial tack were increased upto a certain dose, concentration of tackifier and crosslinkers, reached a plateau and then levelled off with further increasing the dose, tackifier and crosslinkers concentration. Similarly, moisture vapor transmission rate was decreased and the gel content increased with increasing dose of electron beam.

Nylon 66 has been transformed into a material with significantly improved properties like hardness, tensile strength, and flexural modulus by processing it under the optimized dose rate of electron beam in the presence of suitable crosslinkers. Furthermore, percent water absorption of nylon 66 was reduced substantially on irradiation. Thermogravimetric analysis revealed that thermal stability of nylon 66 improved with increasing dose of radiation. Improvement of mechanical and thermal properties and reduction of water absorption of nylon 66 were due to the crosslinking of polyamide molecules made possible by the high energy radiation. Increase of crosslinking with increasing radiation dose was verified by the increase of gel content at higher doses. Differential scanning calorimetry showed that both melting and crystallization temperatures along with percent crystallinity of nylon 66 were decreased with the increasing dose of radiation leading to the development of more amorphous character in this semicrystalline polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Various composites of polypropylene (PP) produced using natural fibers such as pineapple leaf fiber, banana fiber, and bamboo fiber were studied for their degree and rate of aerobic biodegradation. Composites used contained 10, 15, and 50% volume fractions of pineapple leaf fiber, banana fiber, and bamboo fiber, respectively, which are the optimum fiber percentages of the respective composites as reported by these authors in their previous works. Cellulose has been used as positive reference material. All the composites exhibited partial biodegradation in the range of 5–15% depending on the fiber content. Degradation had not taken place in the covalent ester linkages between the natural fiber and the MA-g-PP compatibilizer but in those areas of the fibers which have remained only physically embedded in the resin matrix. Thus, although natural fibers reinforced PP composites are not excellent biodegradable material, they can address to the management of waste plastics by reducing the amount of polymer content used that in turn will reduce the generation of nonbiodegradable polymeric wastes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A device made for biomedical applications must be biocompatible and biologically safe for use. The used ingredients may leach off a device into adjacent tissue and can harm the body after or during application. In the present study qualitative and quantitative methods were used to assess the cytotoxicity of electron beam (e-beam) cured polyurethane pressure sensitive adhesive (PU-PSA) tape materials made for different biomedical applications. In the qualitative morphological results, it was found that there was no cell lysis or morphological changes in triplicate culture wells of the extract of e-beam cured PU-PSAtape. In the quantitative method of cytotoxicity studies, MTT cell viability (%) for PSA tape samples were90, i.e., relative value of toxicity was nil. In case of agar overlay test for test samples, the relative value of toxicity was nil, while in filter diffusion score for the test samples was between 0-0.2, hence the relative degree of toxicity was nil.

It is true that the developments in material sciences along with the improvements in various aspects of technology involved in transforming materials into products, over the years, have been responsible for making many of the impossible-looking devices possible. It is also a fact that the demand for a new, improved and better material has never ended; in fact it has been increasing to a greater degree and with bigger dimensions than ever before, especially in recent times. As a matter of fact, for certain advanced applications, the need for efforts to have new materials can never be over emphasized; for example, in the area of biomedical devices such as intraocular lens (IOL). The advances in the field of bio-medical applications require the materials of high quality meeting stringent norms of performance. For implants such as the ones like IOL used for correction of vision of the eyes, besides the quality and performance of materials, biocompatibility is an issue of major concern. The material scientists have been working on the development of materials for IOLs targeting the needs arising out of the developing countries. The challenges include not only to bring down the cost of the materials used for IOLs but also to increase the biocompatibility of IOLs. For making the development process easy and bringing the state-of-the- art of knowledge to those looking for new materials, it is thought necessary to review various facets of IOLs in the present paper. Not only the aspects related to the recent developments in biomedical devices of eye care but also related to the properties of available materials vis a vis the deficiencies in properties of existing materials have been covered in this review. The aim has been to bring out the gap areas at various levels of process of product chain starting from the monomer to polymer, blank to IOL, insertion of IOL into eyes to life cycle of IOLs, mainly to provide certain possible and feasible leads to meet the challenges of making new and more biocompatible materials.

Ethanol produced from renewable resources is being considered globally as the most prominent and possible substitute for fossil fuel. It is being produced by fermentation of raw materials obtained from various renewable resources like Sugarcane, Corn and Sweet Sorghum all over the world. Ethanol is mainly blended with gasoline in different ratios and commonly known as ‘Gasohol’. This special use has escalated the global production of ethanol by 85% in 2006 from 2002. Oil embargo of 1973 forced Brazil to initiate and implement the Bio-ethanol for mandatory use in automotive fuel upto the extent of 100%. For this to happen, the flexi-fuel vehicles were also introduced that can run both on petrol and E100 (Bio-ethanol). Other countries like US, Europe and India followed this successful model to achieve the objectives of self reliance in fuel. At present in India ethanol is blended @ 5% in petrol. Ethanol in fuel increases its oxygen content and has replaced the use of MTBE and ETBE. Various studies conducted all over the world have revealed that ethanol blending in petrol at different ratios has remarkably reduced the emission of GHG from vehicles. Ethanol has also been used along with diesel, but comparatively ethanol blended petrol is more acceptable than with diesel because later requires the admixture of surfactants to keep the blend stable, which increases the cost of the fuel. Even, having so much benefits of ethanol blending, its use is limited by various technical factors like, degradation of non-metallic components of engine, decrease in fuel lubricity, viscosity and calorific value of the fuel, etc. The other Non-technical factors also plays major role, which are elaborately discussed in this paper. Government of India in the year 2002 issued the first national Biofuel policy, in order to use bio-ethanol and bio-diesel as a fuel for transport. However, certain factors hindered the successful execution of ethanol use as a transport fuel. This paper present the studies conducted to find out the reasons for limited success of especially ethanol blended fuel in India. The outcome of this study would serve as the base reference for the policy makers to devise strategies to achieve the indicative target of recent Biofuel Policy released on September 11, 2008 mandating 20 % blending of biofuels by 2017.