Research On Properties Of Straw/Rubber Composites

Straw obtained from agricultural waste is mainly composed of celluloses which has the characteristics of abundant availability, low cost and recyclability. Straw is incorporated into rubber on laboratory size two-roll mill to prepare two new kinds of straw/natural rubber (NR) and straw/nitrile rubber (NBR) composites. The effects of straw nature and treatment methods on processing, vulcanization, mechanical and aging properties are investigated in details. The main results list below:⑴The incorporation of straw into NR can increase Mooney viscosity which gives rise to poor processing properties of straw/NR composites. Mooney viscosities increase with straw loading; for 15phr the same loading, the bigger the straw particle size is, the higher the Mooney values are.⑵For sulfur vulcanization system, the addition of straw into both NR and NBR compounds increases the crosslinking rate and has a shorter scorch time.⑶Overall results indicate straw only can be used as a cheap filler in NR materials. The good comprehensive properties of straw/NR composites, i.e. tensile strength 14 MPa, modulus at 300% 6.0 MPa, tear strength 29.0 kN·m-1, Shore A hardenss 51 and elongation at break 450% are achieved at straw loading 10-15 phr, particle size 80-100 mesh. Meanwhile, when using different sulfur vulcanization system, the order is conventional vulcanization system(CV)>semi-effective vulcanization system(SEV)>effective vulcanization system(EV) in terms of mechanical properties.⑷Straw can be used as reinforcement for NBR materials. The best results are achieved at the condition of straw loading 15 phr, particle size 60 mesh and the mechanical properties obtained is tensile strength 7.7 MPa, tear strength 23.0 kN·m-1 and Shore A hardenss 64.⑸Mechanical properties of composites can be improved by treating straw with alkali and silane coupling agent. The optimum additions ar 1 phr for KH-550 and 2wt% NaOH solution for alkali treatment respectively.⑹Oxidation resistance of straw/NR composites is very poor and shows higher hardness, lower tensile strength and elongation after aging, which can be improved by properly choice of antioxidants. The best antioxidant is 4010NA or 4010NA in combination with MB among various antioxidants used.