Develppment And Properties Of Thermoplastics From Biopolymers Gratfed With Various Methacrylates

Natural biopolymers, including carbohydrates such as starch and cellulose, proteins suchas soyproteins, chicken feathers, corn DDGs and sorghum DDGs, have been made intothermoplastic films. The developed films from natural biopolymers have good dry and wettensile properties.The commercial thermoplastics are made from synthetic polymer, which is come fromthe non-renewable resources oil. At present, people tried to make thermoplastics frombiopolymers due to the shortage of petrochemical resources. Biothermoplastics that canreplace the traditional plastics derived from synthetic polymers such as polypropylene,polyethylene, and polystyrene, this have gained considerable attention in the past decademainly due to the non-biodegradability of the synthetic polymer based materials and relatedenvironmental concerns. Carbohydrates, such as starch and cellulose, proteins such as soyproteins, have been modified and made into thermoplastic films. Although considerableprogress has been made to develop renewable and sustainable sources to replace traditionalplastics, high cost and relatively inferior performance properties have limited the use ofbiothermoplastics for commodity applications. Thermoplastics made from chemicallymodified biopolymers have good tensile properties and water stability, are suitable for variousapplications. Among the various types of chemical modifications, grafting is more appropriateto develop thermoplastics form biopolymers. Grafting avoids damage to the main chain of thebiopolymers, therefore, the developed products present better tensile properties and retainbiodegradability.Among the various types of monomers grafted onto biopolymers, acrylic monomers suchas methyl, ethyl, and butyl acrylates, and the corresponding methacrylates, are preferred dueto their lower cost and ability to provide good performance properties. Starch is one of themost widely used biopolymers for food and nonfood applications. Starch is an inexpensiveand biodegradable polymer but is nonthermoplastic, needs to be chemically modified to makestarch suitable for various applications. Soyprotein isolates are obtained as coproducts duringsoybean processing, have unique properties and have been widely studied for variousindustrial applications. Although films with properties suitable for various applications havebeen developed from soyproteins by solution casting, the thermoplastics films fromsoyproteins with high strength and stability under aqueous environments have not beensuccessful. Feathers are available in large quantities and at a low price but have limitedapplications. Although thermoplastics have been developed from feathers by graftingacrylates and methacrylates, limited information is available on the properties of thethermoplastics and the effects of different methacrylate structures on the properties ofthermoplastics. Although many reseachers have tried to develop thermoplastics from DDGS,the presence of carbohydrates, proteins, and oil makes it difficult to be used or modified forvarious applications and obtain useful thermoplastics. In addition to the low cost and largeavailability, DDGS is derived from corn, a renewable and sustainable source, and isbiodegradable. Sorghum, a crop that is less energy intensive and requires considerably lower amounts of water to grow is gaining attention as an alternative to corn for biofuel production.Since sorghum DDG contains up to45%proteins that are indigestible by animals, it isnecessary to find alternative applications to make sorghum ethanol economically competitive.Among the various types of chemical modifications, grafting is more appropriate todevelop thermoplastics form biopolymers. Grafting avoids damage to the main chain of thebiopolymers, and therefore the developed products have better tensile properties and retainbiodegradability. Among the five biopolymers, the properties of MA grafted starch is theworst, and the soy protein, feather grafted with MA is the best, the corn and sorghum DDGSis between them. The type of monomer and amount of homopolymers in the filmsconsiderably influenced tensile strength and water stability. The grafted biopolymers showedlower strength but higher elongation with increasing alkyl chain lengths. Increasing thepercent of homopolymers generally increased the tensile strength and elongation. Filmsgrafted with EMA were considerably brittle with elongation of13%, whereas films graftedwith BMA and HMA had elongations between5%and35%, depending on the amount ofhomopolymers. Overall, BMA was found to be more suitable for developing thermoplasticstarch products with good tensile properties and water stability. However, soyproteins graftedwith higher alkyl chain lengths showed better thermoplasticity. Presence of homopolymerswas necessary to obtain films with good tensile strength, elongation and waterstability.Grafted soyprotein films could be used to develop compression and injection moldedthermoplastic products for various applications. The grafted feathers showed lower strengthbut higher elongation with increasing alkyl chain lengths. The developed films from graftedfeathers have good dry and wet tensile properties. Therefore, feathers grafted withmethacrylates could be useful to develop thermoplastics for commercial applications. GraftingDDGS with two monomers showed that the two monomers were partially compatible andgenerally increased the thermoplasticity and would be helpful to develop thermoplastics withhigher strength and elongation. Among the studied three monomers, BMA grafted DDG hadbetter thermoplasticity and prepared films present good dry and wet tensile properties.Grafting appears to be a more viable approach to develop thermoplastics from DDGcompared to other common types of chemical modifications.The films developed from natural biopolymers have good dry and wet tensile properties.This method is sustainable for using renewable resources, and will get considerable economicbenefits.