TY  - EJOU
AU  - Grewell, David 
AU  - Carolan, Sean T. 
AU  - Srinivasan, Gowrishankar 

TI  - Development of Soy Protein Plastics Using Functional  Chemistry for Short-Life Biodegradable Applications
T2  - Journal of Renewable Materials

PY  - 2013
VL  - 1
IS  - 4
SN  - 2164-6341

AB  - : Soy protein plastic formulations were developed through iterative experimental stages to produce waterstable, soy protein isolate (SPI)-based plastic resins. The protein polymer-based materials are glycerol and 
water plasticized resins that have been described as thermoplastics [1] by some researchers and have been 
described as materials that behave similar to thermoplastics upon application of heat and pressure [2]. 
Previous researchers have developed SPI plastic for various applications, all of which were adversely effected 
by water absorption. The formulations in this research included anhydride chemistries, such as maleic 
anhydride (MA), phthalic anhydride (PA), and bifunctional chemistries, such as adipic acid in combination 
with glycerol as plasticizer. The mass content of the respective functional chemistries were varied between 3 
and 10 w/w% (total mass). Formulations based on phthalic anhydride exhibited the lowest water absorption; 
in particular, PA10% formulation exhibited water absorption of 21% compared to 250% for the control 
formulation after 24 h of exposure to water. Anhydride-based formulations were characterized using Fourier 
transform infrared spectroscopy (FTIR) to verify the fundamental mechanisms of improved water stability. 
In addition, cotton-based composites were studied to enhance the mechanical strength. The inclusion of fi ber 
reinforcements reduced the overall dry and wet state mechanical properties. 
The addition of adipic acid (AA) to PA5% reduced the tensile strength by 10–40%, depending on adipic acid 
concentration which was varied from 1.23–10%. Other cost effective formulations were developed and studied 
with varying levels of soy protein isolate (SPI) and soy fl our (SF), which is a relatively inexpensive component 
compared to isolates (<$1/lb compared to $2–3/lb). It was observed that the addition of 
2.5% AA to a PA5% formulation with a 50:50 ratio of SPI: SF reduced water absorption from 36% to 17%.
KW  - Water stability
KW  -  protein plastics
KW  -  anhydrides
KW  -  molding and bioplastics

DO  - 10.7569/JRM.2013.634120