Starch based polymers are of interest because starch is generated by plants from carbon dioxide and water via photosynthesis. Starch is completely degradable in a wide variety of environments.[1] It can be hydrolyzed to glucose by microorganisms and then metabolized into CO2 and H2O.Starch itself has poor thermal and physical stability. That is why starch needs to be modified to increase its usability. However, modifications can reduce the biodegradability of starch based polymers.[1]

Recently starch has been used used in conjunction with petrochemical based hydrocarbons like polyethylene and poly(ethylene-co-acrylic acid). This is being done because starch in composites will be bio degraded and leave only the non-degradable petrochemical hydrocarbon polymers behind. This would reduce the total non degradable material and increase the biodegradable material out there, as the biodegradable and non biodegradable materials will be mixed.

Starch_depleted_polymer.jpg
Figure 1[2] : Biological degradation of a starch-petrochemical composite polymer
Gould et al. (1990) report a plastic composites containing corn starch (20%-40% weight basis) in combination with polyethylene (PE) and poly(ethylene-co-acrylic acid) (EAA). It was found that all of the starch components were removed via metabolization by microorganism in 20-30 days. PE and EEA are not biodegradable and were found to be unaffected after 60 days of incubation. The tensile strength of the film was decreased because of starch removal.[2]

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  1. ^ Lu DR, Xiao CM, Xu SJ. 2009. Starch-based biodegradable polymer material. Express Polymer Letters. 3(6):3266-375.
  2. ^ Gould JM, Gordon SH, Dexter LB, Swanson CL. 1990. Biodegradation of starch-containing plastics. In: Glass JE, Swift G, editors. Agriculture and Synthetic Polymers: Biodegradability and Utilization. 433: 65-75.