Basics 160 120 80 40 0
Basics 160 120 80 40 0 20 A Tensile Strength [MPa] Elongation [%] 5 Figure 3: Tensile Properties of Soy Meal Blends: A): Soy Meal- Biopolyester (30/70 wt %) B): Thermoplastic Soy Meal- Biopolyester (30/70 wt %) 30 B 156 thermoplastics are obtained in two steps; plasticization/ destructurization followed by blending with biopolyesters. The process of plasticization/destructurization is shown in the Fig.2. Soy meal and canola meal has been successfully utilized in dry processing via twin screw extrusion to obtain a thermoplastic like material [6]. This thermoplastic meal was blended with tough biopolyesters like polybutylene succinate (PBS), polycaprolactone (PCL) and polybutylene adipate terephthalate (PBAT) to obtain flexible blends [7]. The study showed that destructurization and plasticization has improved interactions between the meal and the biopolyesters and thereby improving the mechanical properties of the meal based bioplastics. Also, soy meal was successfully converted into thermoplastic using conventional twin screw extrusion in one step process. The blends of soy meal based thermoplastic with PBS, PCL and PBAT were successfully utilized in both injection molding and cast film processing. A comparison of tensile properties of soy meal based blends with biopolyester is shown in the Fig.3, where it can be clearly seen that with thermoplastic conversion of the meal, the properties have improved significantly. However, one of the drawbacks in utilizing the meal for film applications is its fibre content which doesn’t elongate during film processing and restricts its thickness. To overcome this, different techniques were adopted which effectively removes fiber from these meals before initiating plasticization and destructurization step. Ternary blending approach was used to improve the mechanical properties of the thermoplastic blends [6]. Soy Meal + Denaturants & Plasticizers Plasticization / Destructurization Melt Extrusion Thermoplastic Soy Meal Figure 2: Thermoplastic Conversion of Soy Meal via plasticization/destructurization 38 bioplastics MAGAZINE [04/12] Vol. 7
Bioplastics from Protein There are multitudes of advantages in utilizing these proteineous meals for bioplastics applications which include renewability and biodegradability. Biodegradability helps in removing the biodegradable plastic from the environment by the action of microorganisms. This should occur in timely manner for restoring carbon and sustainability. Today all around the world, there is clear demarcation on biodegradability and compostability, where the compostability is time bound biodegradability. Many of the bioplastics including PLA, PCL, PHBV and PBS degrade under controlled composting environments [8]. However their degradation rate is slow compared to the standard compostable materials like cellulose [8]. Furthermore, these bioplastics show very slow degradation profiles in soil and studies have shown that the incorporation of natural materials can accelerate their degradation [9]. Hence, incorporation of proteineous meals can improve the degradation profiles of these bioplastics. Finally, based on the studies conducted by Nova Institute, Germany, biomass utilization for materials application results in 5-9 times more employment and also improves 4-9 times economic value of the meal than any other conventional applications [10]. More importantly this approach helps in utilizing the bio-carbon for plastics applications. Films and sheets obtained from soy meal based formulations on a conventional cast film processing unit are shown in the Fig.4. The cost estimation studies shows that these plastics can be very competitive compared to most of the starch based formulations available. Furthermore, jatropha meal which is not edible can be utilized for this purpose and the technology can be extended to any new oil crop based proteineous meals. Proteineous meals based bioplastics can be used in both flexible and rigid applications. These bioplastics can be especially useful in one trip applications such as cutlery, shopping bags and trash bags. Also, composites can find applications in sports goods, automotive applications. Acknowledgements: – Hannam Soybean Utilization Fund (HSUF) and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) New Directions & Alternative Renewable Fuels ‘Plus’ Research Program 2009 # SR9223. References: 1. Reddy M. M, Mohanty A.K and Misra M, Chem. Eng Prog, 2012, 108(5),37-42 2. Taheripour F, Hertel T W, Tyner W.E, Beckman J.F, and Birur D.K, 2010, Biomass and Bioenergy, 34(3), 278. 3. Verbeek C.J. R., van den Berg E.L, Macromol. Mater. Eng. 2010, 295, 10–21 4. Song F., Tang D.L., Wang X.L., and Wang Y.Z., Biomacromolecules, 2011, 12 (10), pp 3369–3380 5. Wu Q, and Zhang L., Ind. Eng. Chem. Res., 2001, 40 (8), pp 1879–1883 6. Reddy M. M, Mohanty A.K and Misra M, Macromol. Mater. Eng. 2011, 9999, 000–000, DOI: 10.1002/mame.201100203 7. Reddy M. M, Mohanty A.K and Misra M, J. Mater. Sci,2012, 47 (6),p 2591 8. Rudnik E. Compostable polymer materials: Elsevier Science; 2008. 9. Teramoto N, Urata K, Ozawa K, Shibata M. Polymer degradation and stability. 2004;86: 401-9. 10. Nova Institute for Ecology and Innovation, GmbH, “The Development of Instruments to Support the Material Use of Renewable Raw Materials in Germany,” Hürth, Germany (2010). www.bioproductscentre.com Thermoplastic Soymeal- Biopolyester Blend Sheets Cast Film Process Films Figure 4: Sheets and Films obtained from Soy Meal based Bioplastics Colored Films bioplastics MAGAZINE [04/12] Vol. 7 39
