Study On Preparation,Characterization And Properties Of Hydrogenated NR And Hydrosilated TPI

As a natural green raw material, natural rubber has wide applications in various industries for its high elasticity, elongation at break and mechanical stability properties. But because of the natural rubber molecular chain containing the carbon-carbon double bond, it is easy for the natural rubber molecular chain to get influence from heat, oxygen, ozone and UV. The utilization range was narrowed as the result of the weak molecular chain. In recent years, study on the direct hydrogenation into NR molecular carbon-carbon double bond structure became a hot field. Hydrogenated NR(HNR) has a structure similar with ethylene-propylene-diene monomer(EPDM). The molecular structure of EPDM does not contain the polar substituent groups and the intermolecular cohesive energy is relatively low, so it can maintain flexibility of the rubber within a larger temperature range. The structural saturation and non-polarity give EPDM lots of superior performance,including resistance against ozone, heat aging, alkaline and acid, water resistance and electrical insulation properties. The hydrogenated NR not only has characteristics of EPDM, but also contains the superior performance of NRs. It is a new-type green rubber.Trans-1,4-polyisoprene (TPI), also named synthetic Eucommia Ulmoides Gum (EUG), is the isomer of NR. This polymer shows plastics characters in normal temperature, because it's high degree of molecular regularity, and also high Crystallization of molecular chain. In this paper, hydrosilylation reaction was designed on TPI to achieveelastomer of excellent property by destroying the crystallization. This maybe expand its application in various functions areas.This article studies from the following aspects:1. The hydrazine hydrate/hydrogen peroxide/boric acid catalytic system was used for hydrogenation modification. Hydrogenated natural rubber of different degrees of hydrogenation was prepared. 1H-NMR and FT-IR were applied to represent the HNR structure. The Soxhlet extraction method was used to measure the gel content. DSC and TGA testing were done to measure its thermal performance and stability; dilatometer method study showed the low temperature and crystallinity of HNR; and the equilibrium swelling measured the crosslinking density of vulcanized rubber. Results showed that the gel content and the decomposition temperature increased along with the increasing degree of hydrogenation of NR; the glass transition temperature increased slightly; the crosslinking density of vulcanized rubber rose along with increasing degree of hydrogenation. This further proved decreasing flexibility of the HNR after hydrogenation and weakening crystallization of HNR along with increasing degree of hydrogenation.2. Best reaction parameters, including reaction temperature, timing, H2 pressure, NR concentration in solution and content of catalyst for preparing HNR, were determined by using solution hydrogenation with Wilkinson's catalyst. HNR was verified by H-NMR, FT-IR and GPC, the results showed that Mn and Mw were lower than that of NR. Glass transition temperature of HNR has a slightly change; and decomposition temperature of HNR increased along with the degree of hydrogenation increasing.3. Vulcanized HNRs with different degrees of hydrogenation were developed. The mechanical properties of vulcanized HNR and NR results showed that HNR's properties was worse than that of NR's. Ageing-resistant performance of HNR was better than that of NR at 100?, 72h in oxidation test. DMA test results showed that: 1, storage modulus E' of HNR was smaller than NR; 2, for HNR, degree of hydrogenation had some influence on E',when it's at 9.5%, 14.7% and 29.6% percentage, E' showed no big changes,when degree hydrogenation increased to 74.6%, E' decreased a lot along with C-C double bond decreasing; 3, for HNR, tan? was going to smaller as degree hydrogenation increasing.4. Strain induced crystallization researched by AFM, result showed that:under same strain situation, in NR, the fine fibrous region occupied most of the area, and amorphous region was pretty less. For HNR, along with degree hydrogenation increasing, the C-C double bond content decreased. As a result,the molecular chain flexibility getting to lower brought about the difficulty of molecular chain going into lattice. So, HNR was not sensitive on strain-induced crystallization, because amorphous region took the most distribution of stress during the straining process.5. Best reaction process parameters for hydrosilation reaction were gotten after researching the influence on degree of hydrosilation from the reaction time, temperature, dosage of catalyst and triethyl silicane. Confirmed triethyl silicane group was grafted into TPI C-C main molecular chain after characteristic analysis on HsTPI by using H NMR and Si NMR. TG and DTG Spectrogram showed that TPI has one stage of thermal decomposition, and HsTPI has two stage of thermal decomposition. HsTPI's decomposition temperature increasing along with degree of hydrosilation increasing. Glass transition temperature increased along with degree of hydrosilation increasing from the spectrogram of DSC. From test result, we can see that the crystal form changed and also capability of crystallization HsTPI minimized a little bit. Along with hydrosilation degree increasing, cured HsTPI tensile strength and stress at definite elongation decreasing. Compared with the distribution of silicon dioxide in hydrogenated TPI and HsTPI vulcanizates by scanning electron microscope, it was found that silica was better dispersed in HsTPI.