Preparation Of Natural Polymers Based Composite Films And Study On Their Performance

General plastics are widely used in our daily life, but most of them are difficult to degrade in natural environment and always made from the limited fossil resources, what’s worse, they pollute the environment seriously after discarded in environment, hence, the development and application of plastic products are increasingly restricted. It is a generally acknowledged fact that starch is a renewable and unlimited resource, has short production cycle and green biodegradation process, which turns out to be main material of biodegradable composite film.However, mechanical properties of starch-based films or starch/polyvinyl alcohol(PVA) composite films are unsatisfactory and their water resistances are also poor, which are the main reasons of limiting their actual application. So far there have been many researchs about starch- and modified starch-based biodegradable films, on the mean while, more and more attentions have been paid to promote the development and application of natural biopolymers materials. To further improve the mechanical properties and water resistance of starch-based biodegradable films and get more applications of natural biopolymers in biodegradable fields, in this research we successfully created a serials of new biodegradable composite films, which was manufactured via casting the solution on glass mold by blending natural biopolymers, the performances and structure of composite films were measured and characterized.Adding the natural biopolymers such as carboxyl methyl cellulose(CMC), sodium alginate(SA), agar(AG) as strengthening agents and two kinds of plasticizers including sorbitol(SOR) and glycerol(GLY) into mixed system of potato modified starch(PMS) and PVA was an efficient method to enhance the mechanical properties and water resistance of composite films. The composite films with CMC: SA=1:1 showed 124.00% water absorption(A) and tensile strength(TS) of 20.84 MPa. Water absorption of AG-films was further improved, which decreased to 83.35% when the contents of AG were 0.2 g.Different plasticizers have different effects on composite films, so do contents of plasticizers. The results show that with CMC: SA=1:1, TS, E and A valued higher 51.5% and 61.8% and 42.9% respectively in the sorbitol system; while the values of TS in glycerol system were lower than those of sorbitol system, and E vice verse; within certain amounts of plasticizer, increasing amounts of plasticizer resulted in a decrease of TS and a increase of E.Finally, we got that under any plasticizer systems, those biopolymers we added acted an excellent role in enhancing the properties of composite films, especially mechanical properties and water resistance. Although many factors could influence properties of composite films, if few contents of natural biopolymers were added into the system as strengthening agents, performances of conventional composite films could be further improved, especially mechanical properties and water resistance.Fourier Transform Infrared Spectroscopy(FTIR) manifested strong intermolecular hydrogen bonds between starch and other molecules were formed in our process; Scanning Electron Microscopy(SEM) displayed a solid structure of composite film with CMC and SA, few contents of AG added could improve compatibility of system and form a stronger three-dimensional network structure, however, composite films with excessive AG showed uneven structure, biocompatibility became poor. X-ray Diffraction(XRD) found that crystallinity of the composite film reduced, particles diminished, compatibility and flexibility turned better; Differential Scanning Calorimetry(DSC) testified composite films had a certain degree of resistance to environment.We ultimately researched and identified optimum performance of composite films and their corresponding synthetic conditions by some kinds of orthogonal experiments, which has certain theoretical significance in the aspects of process improvement and cost control.