Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 3/26/1998
Publication Date: N/A
Interpretive Summary: Disposal of conventional plastic has become an environmental concern. Furthermore, much plastic is produced from imported petroleum which increases the nation's trade deficit. Developing plastic material by blending starch with biodegradable waste-material such as chitin is a useful approach. It utilizes a renewable resource produced in abundance in the United States together with the largest waste-stream generated by the fish industry. This approach not only reduces the amount of petroleum based materials conventionally used in plastic manufacturing but also adds value to agricultural waste materials. Furthermore, use of natural polymers into plastic is perceived as environmentally beneficial since these materials are naturally biodegradable. We found that chitin and starch are compatible; films had good physical properties and both polymers were readily degradable. Addition of chitin in the formulations slowed biodegradability. These results provide important information on the starch plastic blends and their performance in natural environments. Presented results are of interest to researchers in the field, as well as manufacturers of degradable plastics.
Technical Abstract: A blend containing 40% cornstarch, 25% low density polyethylene (LDPE), 25% ethylene-co-acrylic acid (EAA), and 10% urea as a plasticizer was prepared and extruded into blown plastic films. In another blend, half of the starch was replaced by chitin while the composition of LDPE, EAA, and urea remained the same. Control films containing neat LDPE and EAA were also extruded. Mechanical properties and biodegradability of the films were investigated. These films were incubated with a consortium of highly amylolytic bacteria (LD 76) in liquid culture to determine their biodegradability. Biodegradation was assessed by measuring film weight-loss, infrared absorption changes in FTIR spectra, and measuring changes in physical properties of the films, namely tensile strength and percent elongation, over a 30 day period. While starch/LDPE/EAA/urea films lost over 21% weight within 30 days, weight loss in starch-chitin/LDPE/EAA/urea was only 13.6% during the same time period. The controls, LDPE and EAA, showed negligible weight loss. The FTIR spectra exhibited diminished bands corresponding to OH, C-O, and Amide I region absorbances from the starch and chitin components. No spectral changes were observed in control samples. While percent elongation diminished significantly in both formulations, loss of tensile strength was less pronounced and somewhat variable.