International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 2(4), 1-4, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 1 Investigation of Morphological and Mechanical Behavior of Poly (vinyl alcohol) /Chitosan/Papain Ternary Blend FilmsChougale Ravindra, Masti Saraswati2 and Mudigoudra BhagyavanaDepartment of Materials Science, Mangalore University, Mangalgangotri, 574199, INDIA Department of Chemistry, Karnatak Science College, Dharwad, 580001, INDIAAvailable online at: www.isca.in Received 22nd November 2012, revised 15th February 2013, accepted 13rd March 2013 AbstractTernary polymer blended films were prepared by mixing different weight percent of papain in equal weight percent solutions of poly (vinyl alcohol) (PVA) and chitosan (CS) by solvent evaporating technique. The phase morphology and mechanical properties of various polymeric blended films were carried out using scanning electron microscopy (SEM) and universal testing machine (UTM) at room temperature. SEM micrographs for the blend system showed good miscibility among the blend components. The tensile strength increases with increase in wt% of papain (dried papaya latex in power form) and then decreases. Keywords: Poly (vinyl alcohol), chitosan, papain, mechanical behavior. IntroductionPolymer blending has received much attention in the recent years. This is mainly due to the fact that new materials with better physicochemical properties can be observed when the original polymers are compatible1,2. Blending of synthetic with natural biopolymers is considered as a new class of materials that is of particular significance. Poly (vinyl alcohol) (PVA) is a non-toxic, water soluble synthetic polymer that has been commercially produced on a large scale. It has a large number of hydroxyl groups which allows it to react with many types of functional groups. This advantage makes it suitable as biocompatible materials. PVA has been widely utilized in diverse fields, ranging from thickening agent to controlled release systems. Chitosan, a natural polysaccharide, has attracted much attention of researcher in various parts of the globe. It is produced by excessive alkaline deacetylation of the second most abundant naturally occurring chitin of crab and shrimp shells. Due to the presence of amino groups in its chain, chitosan can be dissolved in dilute aqueous acid solutions, such as acetic acid and propionic acid, formic acid and lactic acid. Since it is inexpensive, non-toxic and possesses potentially reactive amino functional groups, chitosan has been widely used in the fields of medicine, food, cosmetics, agriculture, wastewater treatment and so on6-10. Synthetic polymers offers a broad range of properties that can be reasonably modified using plant products which are attractive and alternative to synthetic products because of biocompatibility, low toxicity, environmental friendliness and low price compared synthetic products11. Papain (papaya latex, PL) is a natural proteolytic enzyme that is extracted from the latex in the leaf, the stem and unripe fruits of papaya tree12. Papain is present in all parts of the papaya plant but maximum amount can be found in their plants leaves and in the skin of the full grown but unripe fruits. Papain (papaya latex, PL) is a milky white sticky substances or latex that flows from fully grown and unripe papaya when it is cut. This milky white substance or latex is collected in a container and dried as papain. Papain (papaya latex, PL) is characterized by its ability to hydrolyze large proteins into smaller peptides and amino acids13. Papain (papaya latex, PL) has wide range of applications in different industries, especially in personal care products such as soap, shower gel and good industry14. It is also being used to tenderize meat and meat products, in the manufacture of protein hydrolysis, in confectionary industry to prepare chewing gums, in brewing industry to remove cloudiness in beer and in dairy industry for cheese15. Similarly, papain is also used in pharmaceutical industry, textile industry and tanning industry14. In addition to tenderizing effect on meats, papain may also be used to make beer chill proof. The main objective of this study was to prepare poly (vinyl alcohol)/chitosan/papain (papaya latex, PL) blend films and to investigate their morphology and mechanical properties. The chemical structures of the polymer used in the study are given below. Chitosan International Research Journal of Environment Vol. 2(4), 1-4, April (2013) International Science Congress Association Poly (vinyl pyrrolidone) Figure-1 Chemical structure of the polymers Material and Methods Poly (vinyl alcohol) having molecular weight 1,40,000 and Chitosan were obtained from HIMEDIA Mumbai. Papain was received from Sisco Research Laboratory, Mumbai and acetic acid was procured from, Spectrochem, Mumbai, and was used as received. Doubly distilled water was used throughout the experiment. Preparation of Blend Films: Ternary polymer blends films of poly (vinyl alcohol)/ch itosan/papain of different compositions were prepared by solution casting method. For the preparation of blend films, exactly weighed amount of polymers and papain were dissolved separately. Chitosan solution was prepared in 2% acetic acid and poly (vinyl alcohol) and papain solution was made in universal solvent water. After allowing them to dissolve completely, papaya latex was not dissolved completely, then polymer solutions were mixed with continuous stirring four hours and subsequently definite volum e of all blend solutions poured onto previously cleaned and dried glass petri dishes and solvent is evaporated at room temperature to form blend films. Finally the petri dishes containing films was dried in hot air oven at 45C for a week to ensure comple te removal of trace amount of solvent present in the blend films. After evaporation of complete solvent all films peeled off from petri and kept under evacuated desiccator over fresh silica gel until use. All obtained films were semitransparent, uniform bubble free. Mechanical Properties: A LLOYD LRX plus machine, UTM, (LLOYDS – 5 KN, London, UK) was used to measure tensile strength, young’s modulus and percent elongation (%). The tests were carried out according to ASTM D-882 standard test (ASTM, 1992). Rectangular shaped sample of films (25 × 100 mm) were taken for the determination of tensile properties. Two metallic grips were attached for griping both ends of the test specimen of the film. The lower grip was sta tionary and the upper grip moved upward with constant rate of extension 50 mm/min keeping constant initial grip separation 50 mm for all samples. An automatic speed controller was attached to keep the speed of the upper grip. The machine was electrically driven. All measurements were carried out at room temperature in air. Tensile Strength calculated by dividing the maximum load for breaking the film by cross-sectional area. Elongation at Break Environment Sciences_______________ _________________________ International Science Congress Association Chemical structure of the polymers Poly (vinyl alcohol) having molecular weight 1,40,000 and Chitosan were obtained from HIMEDIA Mumbai. Papain was Research Laboratory, Mumbai and acetic acid was procured from, Spectrochem, Mumbai, and was used as received. Doubly distilled water was used throughout the Ternary polymer blends films of itosan/papain of different compositions were prepared by solution casting method. For the preparation of blend films, exactly weighed amount of polymers and papain were dissolved separately. Chitosan solution was prepared in alcohol) and papain solution was made in universal solvent water. After allowing them to dissolve completely, papaya latex was not dissolved completely, then polymer solutions were mixed with continuous stirring four e of all blend solutions poured onto previously cleaned and dried glass petri dishes and solvent is evaporated at room temperature to form blend films. Finally the petri dishes containing films was dried in hot air te removal of trace amount of solvent present in the blend films. After evaporation of complete solvent all films peeled off from petri and kept under evacuated desiccator over fresh silica gel until use. All obtained films were semitransparent, uniform thickness and LRX plus universal testing 5 KN, London, UK) was used to measure tensile strength, young’s modulus and percent elongation (%). The tests were carried out according to ASTM Rectangular shaped sample of films (25 × 100 mm) were taken for the determination Two metallic grips were attached for griping both ends of the test specimen of the film. The lower tionary and the upper grip moved upward with constant rate of extension 50 mm/min keeping constant initial grip separation 50 mm for all samples. An automatic speed controller was attached to keep the speed of the upper grip. The driven. All measurements were Tensile Strength was calculated by dividing the maximum load for breaking the film Elongation at Break by dividing the film elongation at rupture to initial g is the ratio of the extension to the length of the sample). modulus of elasticity (young’s modulus) is strain at the linear portion of the curve or slope of the linear portion of the curve of stress str ain. Scanning Electron Microscopy: viscosity difference among the polymers or component of blend films has a significant impact on the phase morphology of the blends. If the minor component has lower viscosity compared to the major one, it will be finely and uniformly dispersed in the major continuous phase owing to the diffusion restrictions imposed by the matrix16 and otherwise coarsely dispersed. Films surface morphology was examined using scanning electron microscopy (SEM). Prior to the examination, blend films were dried overnight in a hot air oven at 45 mounted on a metal stub with double side sticky tape. Then the blend films were coated with a thin layer of platinum in order to improve conductivity and prevent electron charging on the surface. The morphological structures of the films were studied by a JSM- 6360 scanning electron microscope (SEM) of JEOL, Germany, and the images were taken at accelerating voltage 5 kV and a magnification 500 times of origin specimen size. Results and DiscussionMechanical properties: The phase morphology and the interfacial adhesion among the components of polymer blend, influence the mechanical properties of polymer blend films. The stress- strain behavior of blend films is demonstrated in figure 2. From the stress- strain curves, we estimated maximum tensile strength, elongation at break and young’s modulus, data was analyzed using NEXOGEN Plus software, and these tensile properties are summarized in table 1. The tensile strength, young’s modulus (modulus of elasticity) and percent elongation could be used to describe how the mechanical properties are related to their chemical structure. The tensile strength indicates the maximum tensile stress that the film can sustain. Figure - Stress- Strain curves of PVA/CS/PL blend films 051015201020304050 1. 50% PVA/50% CS 2. 47.5% PVA/47.5% CS/5% PL 3. 45% PVA/45% CS/10% PL 4. 42.5 PVA/42.5% CS/15% PL 5. 40% PVA/40% CS/20% PL 541 Strain (%) Stress (MPa) _________________________ ______ ISSN 2319–1414 Int. Res. J. Environment Sci. 2 film elongation at rupture to initial g auge length (% elongation is the ratio of the extension to the length of the sample). The modulus of elasticity (young’s modulus) is the ratio of stress to strain at the linear portion of the curve or slope of the linear ain. Scanning Electron Microscopy: It should be noted that the viscosity difference among the polymers or component of blend films has a significant impact on the phase morphology of the blends. If the minor component has lower viscosity compared the major one, it will be finely and uniformly dispersed in the major continuous phase owing to the diffusion restrictions and otherwise coarsely dispersed. Films surface morphology was examined using scanning Prior to the examination, blend films were dried overnight in a hot air oven at 45 C and mounted on a metal stub with double side sticky tape. Then the blend films were coated with a thin layer of platinum in order to improve conductivity and prevent electron charging on the The morphological structures of the films were studied 6360 scanning electron microscope (SEM) of JEOL, Germany, and the images were taken at accelerating voltage 5 kV and a magnification 500 times of origin specimen size. The phase morphology and the interfacial adhesion among the components of polymer blend, influence the mechanical properties of polymer blend films. strain behavior of blend films is demonstrated in strain curves, we estimated maximum tensile strength, elongation at break and young’s modulus, data was analyzed using NEXOGEN Plus software, and these tensile properties are summarized in table 1. The tensile strength, (modulus of elasticity) and percent elongation could be used to describe how the mechanical properties are related to their chemical structure. The tensile strength indicates the maximum tensile stress that the film can sustain. - 2 Strain curves of PVA/CS/PL blend films 2530354045 1. 50% PVA/50% CS 2. 47.5% PVA/47.5% CS/5% PL 3. 45% PVA/45% CS/10% PL 4. 42.5 PVA/42.5% CS/15% PL 5. 40% PVA/40% CS/20% PL 32 Strain (%) International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(4), 1-4, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 3 Table-1 Tensile properties of PVA/CS/PL blend films Blend ratios (wt%) Tensile Strength (MPa) Young’s modulus (MPa) Elongation at Break (%) 50% PVA/50% CS 12.881 136.639 27.489 47.5% PVA/47.5% CS/5% PL 45.128 1452.918 37.413 45% PVA/45% CS/10% PL 45.338 1291.455 42.300 42.5% PVA/42.5% CS/15% PL 41.719 607.270 37.090 40% PVA/40% CS/20% PL 36.119 1183.68 11.784 Young’s modulus is a measure of the stiffness of the blend film material. Elongation at break is the maximum change in length of a test film before breaking. The results indicate that the addition of the papaya latex increases the tensile strength and then decreases. Blend film exhibits maximum tensile strength with 10% papaya latex and above this wt% tensile strength decreases which may be due to decrease in interfacial adhesion among the blend components. Scanning electron microscopy (SEM): Figure 2 shows SEM photographs of the top surface of the pure poly (vinyl alcohol)/chitosan blend film and poly (vinyl alcohol)/chitosan/papaya latex blended films. The result of SEM indicates that on surface of poly (vinyl alcohol)/chitosan film there are many non spherical granules with varying sizes and these kinds of granules are not seen in the films prepared from papaya latex. Blend films prepared from 10 wt%, 15 wt% and 20 wt% papain displayed clear and homogenous surfaces with no interface layers. The formation of homogeneous blends of poly (vinyl alcohol)/chitosan/papain was mostly due to the interactions of hydrogen bonds among the functional groups of the blend component. However, the ratio 47.5%PVA/47.5%CS/5%PL blend film showed a little rougher surface indicating more hydrophilic top surface than the other blend films. According to Chen et al17 such a rough surface could be due to the reorientation of polar functional groups toward to the top surface of the blend film. Based on these observations it can be concluded that all papaya latex blended films were compatible at all ratios. (a) 50%PVA/50%CS (b) 47.5%PVA/47.5%CS/5%PL (c) 45%PVA/45%CS/10%PL (d) 45%PVA/42.5%CS/15%PL (e) 40%PVA/40%CS/20%PL Figure-2 SEM micrographs of pure PVA/CS and PVA/CS/PL blended films International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(4), 1-4, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 4 ConclusionTernary blended films of poly (vinyl alcohol)/chitosan/papain were prepared at various proportions of papaya latex. SEM Investigation of the obtained blend films displayed good miscibility among poly (vinyl alcohol), chitosan and papain due to the interaction existing among the components of blend films. AcknowledgmentWe, Ravindra Chougale (PI) and Saraswati Masti (CO-PI), express our sincere thanks to the University Grants Commission (UGC), New Delhi, India, for financially supporting this research project under the research grant, F.No.34-397/2008 (SR)/30 Feb., 2008. References1.Ratajska M. and Boryniec S, Physical and Chemical Aspects of Biodegradation of Natural Polymers, Reactive and Functional Polymers,38(1), 35-49 1998) 2.Bae Y.H. and Kim S.W., Hydrogel Delivery Systems Based on Nolymer Blend Block Copolymer or Interpenetrating Networks, Advanced Drug Delivery Review, 11(1-2), 109-1351993) 3.Yang X., Zhu Z. 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