| Acetone extracts was extracted from nature rubber (NR) by dissolution of acetone. The composition of acetone extracts and its influence on mechanical properties, crosslink density and the thermo-oxidative stability were investigated by FTIR, GC/MS, tensile test machine, NMR and TG/DTG. Vulcanization characteristics, crosslinking density and thermal oxidation stability of NR,IR vulcanizes were studied and tested by the vulcanizing apparatus, NMR cross-linked densitometer and TGA respectively. Lipid extracts extracted from nature rubber latex (NRL) by chloroform/methanol mixes was saponificated and theβ-Sitosterol was generated, and the influence ofβ-Sitosterol on aging properties and thermal stability of rubber were measured and studied.The results show that the influence on mechanical properties, cosslink density and the thermo-oxidative stability of NR and IR of acetone extracts andβ-sitosterol is obviously. The performance of modulus, tensile strength and tear strength of NR & IR with acetone extracts is better than NR & IR. Tensile strength of NR vulcanizates is promoted previously and decreased finally with the increasing of more acetone extracts. The maximum tensile strength of NR vulcanizates was achieved if 1 phr acetone extracts were available. Otherwise, the tensile strength of IR vulcanizates decreased with the increasing of acetone extracts. The modulus, tensile strength and tear strength of NR & IR increased obscurely with increasing ofβ-sitosterol.The composition of acetone extract was analyzed, which includes higher aliphatic acids (72.1%), higher aliphatic acid esters (7.99%), olefins (8.74%), alcohols (9.01%) and little aldehydes (1.17%) and ketones (0.99%). The existences of these substances play a physical softening of the role to improve the processing properties of rubber.The results of vulcanization characteristics show that t10, t60, t90 of NR and IR samples with acetone extracts are all lower than the blank samples, while the maximum torque (MH) is higher than the blank one. The modulus, tensile strength and tearing strength of rubber with acetone extracts are higher than before. The vulcanizing properties of rubber with acetone extracts is improved, because many active alcohols of vulcanization and higher aliphatic acids were available in acetone extracts, which can improve the diffusion and activities of zinc oxide. The crosslinking of rubber molecules is enhanced for above reasons and the modulus, tensile strength of vulcanized rubber is improved.The results of Nuclear Magnetic Resonance (NMR) show that, the cross-link density of NR and IR with acetone extracts is higher and the magnetic decay rate is quicker comparing with the blank samples. Which indicates the network integrity of NR with acetone extract is better than before. The cross-link density of vulcanized NR is 1.56 x 10"4 mol/cm3,54.5% promotion compare with the blank samples if 1 phr acetone extract was added. While the cross-link density of vulcanized IR is 1.92 x 10-4 mol/cm3,10.3% higher than before, if 2.5 phr acetone extract was added. As a result, network of vulcanized rubber can be improved and enhanced by acetone extracts, which will increase the complication of network structures.The results of thermo gravimetric analysis show that, thermal and thermo-oxidative stability of NR and IR were influenced by acetone extracts andβ-Sitosterol. The thermal degradation of NR and IR in nitrogen is an one-step reaction, and the thermal stability of NR and IR can be improved by adding acetone extracts orβ-Sitosterol. However, the thermo-oxidative degradation of NR and IR in air is a two-step reaction. The first step will be taken in the temperature of 300℃-450℃and the next step reaction is taken in the temperature of 450℃-550℃. The cross-link density of molecular of rubber will be improved by acetone extracts, which will promote the anti-aging performance of rubber. While, theβ-Sitosterol is an antioxidant, and both the acetone extracts and P-Sitosterol can improve the thermo-oxidative stability of rubber. |
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