Preparation of fully biodegradable starch-based materials

Biodegradable starch-based materials were prepared by blending starch with polyvinyl alcohol (PVA), soy dregs and glycerol as plasticizer. The effects of the amount of PVA and soy dregs on the mechanical properties of materials prepared were investigated. The results showed that the tensile strength of starch-based materials increased first and then decreased with increasing of soy dregs and PVA. And the elongation at break decreased when increasing soy dregs, but first increased then decreased with increasing of PVA. The effects of paper powder and CaCO₃ on the mechanical properties of materials prepared were also investigated. The results showed that both paper powder and CaCO₃ enhanced the tensile strength in some degree, but decreased the elongation obviously. The tensile strength and elongation attained 3.5 MPa and 60% respectively while keeping starch∶soy dregs∶PVA∶glycerol∶CaCO₃ as 60∶10∶6∶10∶2. Moisture absorption measured under 100% relative humidity showed that rape oil and glyceryl stearate could reduce the moisture absorption of the starch-based materials and the moisture absorption of starch-based materials coated with latex decreased obviously. The samples of obtained material underwent microbic growth on humus soil for 7～8 d, and the coverage of microorganism on sample surface was above 60%.