Research On Preparation And Performance Of Biodegradable Thermoplastic Films And Textile Sizes From Natural Proteins

The coproducts of processing cereal crops and waste are available in abundance, inexpensive, biodegradable and are derived from renewable resources. They don’t need to special grown and have the utilization of the low value. Therefore, these renewable materials and eco-friendly processing with clean technologies are paid more and more attention in scientific theory research and practical application research. If these resources are reasonable to be used in textile materials, it will effectively reduce the carbon discharge from the textile industry complex from the beginning and weaken the dependence on petroleum resources for textile industry.Attempts have been made to use proteins, such as wheat gluten, zein and chicken feather to develop thermoplastic films. Since proteins have poor thermoplasticity, plasticizers such as glycerol or chemical modifications are inevitably used to develop thermoplastics from proteins. However, there are limited industrial applications and further research. The research is that plasticizers such as glycerol commonly used to plasticizing proteins are hydrophilic, absorb considerbale amounts of water and therefore substantially decrease the mechanical properties and also reduce the water resistance of the thermoplastics, and the chemical modification increase the cost of protein-based products. This research will lay the foundation for the development of natural protein based biomaterials, develop a new thought to get green textile materials from natural resources, which make textile industry less impact on the environment and achieve sustainable development.To sum up, the following five problems are mainly studied in this paper.First, we demonstrate alkali hydrolysis approach of controlling the melting performance and dissolving performance of proteins. Proteins were hydrolyzed using various concentrations of alkali and the hydrolyzed proteins were compression molded into films and prepared for textile sizing. Different molecular weight of hydrolyzed proteins influenced the application performances of thermoplastic films and protein sizes.Second, the preparation condition and performances of thermoplastic protein films were studied. The thermoplasticity, water stability and tensile properties of films were improved by controlling concentration of glycerol and temperature of hot-press. The thermoplastic performance was characterized by the means of SEM, DSC, TGA and pictures. The effect on tensile properties and water stability of films of time, temperature, concentration of glycerol and crosslinking agent was evaluated by breaking stress, breaking elongation and modulus of films.We show that the protein samples can be compression molded into thermoplastic films with good tensile strength and water stability using low glycerol concentration but high molding temperatures. Furthermore, the citric acid crosslinking occurs at the temperature range used to compression mold the films, enabling a one-step crosslinking-compression-molding process, which is helpful to improve the water stability of the films.Third, the interaction mechanism and effect factors between protein sizes and sized material were researched. We developed the soy protein, wheat gluten and chicken feather protein films using casting solution method and evaluated the mechanical properties of protein films with peak load and peak elongation. Furthermore, the protein (soy protein, wheat gluten and chicken feather protein) sizes were prepared by alkali hydrolysis method and the effects of alkali concentration, temperature and time on performance of sized material were studied. Firstly, different treatment conditions of alkaline hydrolysis decreased the molecular weight and made the proteins suitable to develop textile sizes, which influenced the viscosity of protein sizes. Secondly, we have used the hydrolyzed proteins to size polyester and polyester/cotton rovings, yarns and fabrics. The effect of sizing conditions on the adhension properties and abrasion resistance properties of the sized materials was studied based on peak load, peak elongation, abrasion times of sized material, which provide the guidance to practical application of protein sizes. Thirdly, the simplicity to desize of the protein sizes with water have been studied according to percent desizing ratio, including the effect of ratio of fabric and water, temperature and rinse times on desizing performance. The research demonstrates the ability to form films and the feasibility to be textile sizes from soy protein, wheat gluten and chicken feather proteins. Protein sizes can penetrate into yarns and have good adhension on fibers with controlling viscosity. Low cost, excellent film forming properties, adhesiveness, insensitive to humidity and easy desizing make proteins a very attractive choice as a textile sizing agent for polyester and their blends.Fourth, the environmental performance of protein sizes was evaluated. Protein sizes were treated in activated sludge and assessed the biodegradability of proteins with the changes of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), and total nitrogen and ammonia nitrogen value before and after treated. The results show that soy protein, wheat gluten and chicken feather protein sizes were digested by microorganism. The total nitrogen and ammonia nitrogen released during degradation was little, which demonstrate that the degradation of protein sizes has not negative effects on operation of water treatment plant.Fifth, it is very important to evaluate the feasibility for protein sizes to substitute PVA sizes for sizing polyester and polyester/cotton materials. Commercially used PVA sizes have been used to size polyester/cotton (65/35) and polyester rovings, yarns and fabrics. The properties of PVA sizing agent, sized materials, desizing and biodegradable have been compared with the same materials sized with protein sizes. The results show that protein sizes provide the desired sizing properties, biodegradability, simplicity to preparation and cost-effective substitute to PVA for sizing synthetic fibers and their blends, which can decrease the pollution to environment for textile plants.This research results have innovations based on theory and application of biodegradable material subject, which is reflected in the scientific utilization of natural bioresources and coproducts from agricultural products. These findings will solve the ecological problems meeted in textile industry. This innovation is mainly reflected in the following aspects:First, we extracted peanut proteins with controlling molecular weight from peanut meal by alkaline hydrolysis based on the theory of protein degradation. Alkaline hydrolysis method can be used for extracting proteins from coproducts from processing crops and waste, which can solve the environmental pollution and resource shorage problems to make textile industry sustainable development.Second, the proteins were hydrolyzed using alkali and then compression molded into thermoplastic films.The alkaline hydrolysis method can solve the melting problems for many plant and animal proteins and make them into biodegradable thermoplastics.Third, thermoplastic films with good tensile strength and water stability were compression molded using low glycerol concentration but high molding temperatures from the wheat proteins (gluten, gliadin, glutenin and pure glutenin), peanut proteins and chicken feather proteins.Fourth, a one-step crosslinking-compression-molding process was developed, which can improve the water stability for protein films. The non-toxic crosslinking with citric acid can save cost and the films could be used for food and medical applications.Five, protein sizes for textile were prepared by alkaline hydrolysis method which have been studied in comparison to commercially available PVA based sizes, which was expected to provide the desired sizing properties, biodegradability and cost-effective substitute to PVA for sizing synthetic fibers and their blends. This result can solve the problems of removing PVA sizes and environmental pollution, also develope a novel resource for green textile sizes. Fifth, environmental performance for protein sizes were evaluated based on the changes of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), and total and ammonia nitrogen value before and after treated in activated sludge. The result is helpful to reduce the pollution to environment from size effluents from textile plants.