Study On The Strain-induced Crystallization Of Natural Rubber Blend And Synthesis Of Biobased Rubber Accelerator

For the requirement of natural rubber (NR) development and greening of rubber industry, strain-induced crystallization (SIC) property of NR blend and synthesis of biobaed rubber accelerator were studied in this research. Now China is faced with the shortage of NR. Isoprene rubber (IR) can't replace NR because the SIC property of IR is inferior to NR. To solve these problems, we studied the effect of NR on the SIC property and structural evolution of IR by using wide angle X-ray diffraction (WAXD) and PeakForce QNM atomic force microscopy methods. We also used serinol and camphor to synthesis biobased rubber accelerator in order to solve the problem that traditional rubber accelerators rely on fossil fuel resources and can produce toxic substances.The main research content and achievements are shown as follows:1. To prepare the unvulcanized and vulcanized NR/IR blend, SKI-3 S was selected as IR and mixed with NR by mechanical blending. We used dilatometers to investigate the temperature-induced crystallization process of NR/IR blends at -25?. It has been shown that the unvulcanized IR sample crystallizes somewhat more slowly than the control sample of NR, seven times lower at -25? without deformation. By blending with NR, the crystallinity and crystallization rate of unvulcanized IR can be improved significantly.What's more, the crystallinity and crystallization rate of unvulcanized IR increase with NR content increasing.2. We studied the SIC process of vulcanized NR/IR by using the stress relaxation method at -25?.The rate of stress relaxation increased with initial strain increasing which means the rate of crystallization increased as strain increased. The vulcanized IR took eight to twelve times as long as for the NR crosslinked to the same degree over a range of strains from 50% to 200%. IR achieved higher crystallinity and crystallization rate by blending with NR.3. WAXD was mainly applied to investigate the SIC of NR/IR including the change of crystallinity, unit cell parameters, grain size and degree of orientation. The results showed that the onset strain of SIC of NR was smaller than IR while the onset strain of SIC of IR could be increased by blending with NR. The unit cell parameters, grain size of NR, IR and NR/IR were almost same and kept constant during stretching. The degree of orientation increased slightly with strain increasing. We proposed a model to illustrate the SIC process: When vulcanized NR was stretched, chemical bond network and entanglements induced SIC at small strain and pseudo end-linked network assisted the induction of SIC at high strain, which leaded to the higher crystallinity of NR than IR and could increase the crystallinity of IR significantly by blending IR with NR during SIC process.4. We characterized TKS rubber by FTIR, NMR, GPC and TGA and found that the structure of TKS rubber is cis-1,4-polyisoprene which is similar to NR from rubber tree. WAXD results showed that TKS has smaller onset strain of SIC than NR and IR. TKS rubber has higher crystallinity comparing with NR and IR at the same strain. TKS may provide a new source of natural rubber as the cold resistant and adaptability of this plant obviously exceed that of rubber tree.5. PeakForce QNM AFM method was firstly applied on researching the SIC of sulfur and DCP vulcanized NR, IR and NR/IR. We used the nanomechanical mapping to probe the structural evolution and mechanical properties of deformed rubber. We directly visualized the microstructure evolution and demonstrated that the highly deformed rubber consists of a hierarchical network of nanofibrils ranging from several to one hundred nanometers in size, which is responsible for the significantly enhancement in the stress, leading to the superior mechanical properties. Our findings have identified key structural features of the highly deformed rubber and provide new insights into the structure-mechanical property relationship that should aid in the rational design of more enhanced mechanical properties of self-reinforcement elastomers by SIC.6. Synthesis of serinol-camphor imine (SC) was performed by reacting serinol and camphor in the absence of any solvent or catalyst, at 180? and the average yield was about 60%. The imine presents high thermal stability and its steric hindrance is compatible with reactions of hydroxyls with other functional groups. SC appears thus suitable candidate for stepwise polymerizations. Polyurethanes and polyethers were prepared, in the absence of solvents, with 1,6-hexamethylene diisocyanate and 1,6-dibromohexane as the comonomers. They were characterized through thermogravimetric and 13C-NMR analysis and differential calorimetry. SC could be used as a new rubber accelerator and the synthesized polymers could mediate the solubility of apolar molecules such as camphor in polar media, thus modulating their release in environments such as aqueous solutions. Controlled release of camphor and other carbonyl molecules make these polymers as reservoirs of active molecules for a variety of functions: from antimicrobial to local anesthetic.