Chapter 12
Extruded Plastics Containing Starch and Chitin: Physical Properties and Evaluation of Biodegradability 1
2
2
1
K. A. Niño , S. H. Imam , S. H. Gordon , and L. J. G. Wong 1
Department of Microbiology and Immunology, University of Nuevo León, San Nicolás de los Garza, Nuevo León 64000, Mexico
Downloaded by UNIV OF ROCHESTER on August 27, 2013 | http://pubs.acs.org Publication Date: March 25, 1999 | doi: 10.1021/bk-1999-0723.ch012
2
Biopolymer Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 N. University Street, Peoria, IL 61604
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 plasticfilms.In another blend, half of the starch was replaced by chitin while the composition of LDPE, EAA and urea remained the same. Controlfilmscontaining neat LDPE and EAA were also extruded. Mechanical properties and biodegradability of thefilmswere investigated. These films were incubated with a consortium of 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 by measuring changes in physical properties of thefilms,namely tensile strength and percent elongation, over a 30 day period. While starch/LDPE/EAA/ureafilmslost over 21% weight within 30 days, weight loss in starch-chitin/LDPE/EAA/urea was only 14.0% during the same time period. The controls, LDPE and EAA, showed negligible weight loss. FTIR spectra exhibited diminished bands corresponding to OH,C-Oand Amide I region absorbancesfromthe starch and chitin components. No spectral changes were observed in control samples. While percent elongation diminished significantly in bothformulations,loss of tensile strength was less pronounced and somewhat variable. The use of plastics in single-use, disposable applications has increased significarrtly, particularly in the second half of this century. The useful life of most plastics end after packaging is removed (7). Plastics persist in the environment due to their resistance to biodegradatioa Improper disposal of plastics has been shown to cause harm to marine animals, including sea birds, turtles and other life forms (2). Recalcitrant plastics accumulate in the environment at a rate of 25 million tons per year (J). Plastic formulations containing starchfromcorn as a biodegradable component have been studied as part of an effort to increase the susceptibility of plastic products to biological degradative processes (4-6). Once disposed of in the environment, these materials are
© 1999 American Chemical Society
In Biopolymers; Imam, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
195
196 expected to biodegrade under the influence of environmental processes and eventually disintegrate into smaller and benign byproducts (7). Examples include agricultural mulch films, used for weed control and water retention in crops, as well as packaging materials and other rigid containers that have limited durability and can be discarded after use. Starch is a polysaccharide which has been used extensively in the development of biodegradable plastics. The objective of this study was to develop formulations containing other potentially useful natural polysaccharides, such as chitin, in starch-synthetic polymer blends and test their biodegradability under laboratory conditions.
Downloaded by UNIV OF ROCHESTER on August 27, 2013 | http://pubs.acs.org Publication Date: March 25, 1999 | doi: 10.1021/bk-1999-0723.ch012
Experimental Plastics. The plasticfilmsused in this study were obtained by the semi-dry method of Otey (8). Formulations are shown in Table I. Two test formulations were prepared, one containing 40% starch (dry-weight basis), while the other contained 20% starch and 20% chitin. Both formulations contained the same amount of LDPE, EAA and urea. Control films were neat LDPE or EAA, without any polysaccharide.
Table L Plastic Formulations and Physical Properties Formulation
LDPE (%)
EAA (%)
Starch (%)
Chitin
Starch/LDPE/ EAA/Urea
25
25
Starch/Chitin/ LDPE/EAA/ Urea
25
25
Neat LDPE
100
Neat EAA 8 b
100
TS" (Mpa)
%E
