Preparation And Modification Of Liquid Natural Rubber

This paper studied that liquid natural rubber (LNR) was prepared respectively by four types of oxidative degradation agents (phenyl hydrazine, nitrobenzene-hydrogen peroxide, potassium persulfate-propionaldehyde and periodic acid). The optimum conditions of each degradation agent were conducted by orthogonal experiment, and the structures of LNR were analysised with FTIR. Carbonyl-telechelic liquid natural rubber (CTLNR) was successfully prepared by the selective controlled degradation of natural rubber via epoxidation and cleavage reactions, and then hydroxyl-telechelic liquid natural rubber (HTLNR) was obtained through reduction of end groups of CTLNR, then CTLNR-g-PMMA was obtained by the copolymerization of methyl methacrylate into CTLNR. Structures of the three products were characterized by FTIR and1H-NMR, and glass transition temperature (Tg) of CTLNR and HTLNR were analysised by differential scanning calorimetry(DSC).The results show that the values of average molecular weight (Mn) and molecular weight distribution were13961g-mol-1and1.83respective for liquid natural rubber which was obtained by the degradation of NR with phenyl hydrazine as degradation agents. The amounts of functional group at the terminal chain were too much. The values of Mn and molecular weight distribution were36216g-mol-1and1.95respective for liquid natural rubber which was obtained by the degradation of NR with nitrobenzene-hydrogen peroxide as degradation agents. The functional groups at the terminal chain were hydroxyl group and carbonyl group. The values of Mn and molecular weight distribution obtained are43861g-mol-1and1.79respective for liquid natural rubber which was obtained by the degradation of NR with potassium persulfate-propionaldehyde as degradation agents. The functional group at the terminal chain was mostly carbonyl group. The values of Mn and molecular weight distribution obtained were16652g-mol-1and1.67respective for liquid natural rubber which was obtained by the degradation of NR with periodic acid as degradation agents. The functional group at the terminal chain was carbonyl group. There are contrasts between the tetrahydrofuran and latex. The degradation ability of periodic acid in latex was poor. The viscosity-average relative molecular mass of LNR obtained from ENR latex was28100, and the epoxide ring was partly degraded by periodic acid. The LNR contained a lot of the epoxide ring and a little aldehyde and ketone. The viscosity-average relative molecular mass (Mn) of CTLNR were decreased with the increase of reaction temperature, time and oxidant amount. The degree of epoxidation content of ENR played a decisive role in the Mn of CTLNR, and through the control of the degree of epoxidation of ENR realized the Mη controllable. The disappearance of characteristic signals of epoxide ring and the presence of characteristic signals of carbonyl indicated that aldehyde and ketone were the end functional groups of CTLNR. Then the appearance of characteristic signals of hydroxyl function showed that the end functional group of HTLNR was hydroxyl function. The analysis of DSC of CTLNR and HTLNR showed that the value of Tg of CTLNR was much greater than ENR, directly caused by sharp decline of the molecular weight, and the value of Tg of HTLNR was greater than CTLNR, caused by the transformation of chemical polarity.CTLNR chain grafted PMMA by free radical polymerization, and graft was80.5%.