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对天然橡胶复合材料进行了不同时间下的热氧加速老化实验并分析其老化机理.采用红外测试研究天然橡胶在热氧老化过程中可能的基团变化规律,同时对不同老化时间下的红外结果进行二维相关分析,发现老化产物的生成速率依次为酯>过氧化物>醚;核磁交联密度测试表明总交联密度(XLD)与网链分子量(Mc)及横向弛豫时间(T2)有很好的对应关系,XLD随着老化时间的增加而增加,即天然橡胶热氧老化过程中交联反应占主导地位;示差扫描量热(DSC)测试发现,随着老化时间的增加,玻璃化转变温度(Tg)升高,玻璃化转变区变宽,表明交联反应占主导地位,与核磁交联密度测试结果一致.通过对天然橡胶进行压缩应力松弛实验,采用修正的标准线性固态模型(SLS模型)进行拟合分析,发现在短时热氧老化过程中,老化以氧化和交联反应为主,与核磁交联密度及DSC实验结果一致.
The accelerated aging tests of natural rubber composites at different times were carried out and the aging mechanism was analyzed.The possible changes of the groups of natural rubber in the process of thermo-oxidative aging were investigated by infrared spectroscopy. Infrared results of different aging time Two-dimensional correlation analysis showed that the formation rate of aging products was ester> peroxide> ether. The NMR cross-linking density test showed that the total crosslinking density (XLD), the molecular weight of network chain (Mc) and the transverse relaxation time (T2) There is a good correspondence between the XLD and the aging time, that is, the crosslinking reaction dominates in the thermo-oxidative aging of natural rubber. The differential scanning calorimetry (DSC) test shows that with the increase of the aging time, the glass The transition temperature (Tg) increased and the glass transition region widened, indicating that the cross-linking reaction dominates, consistent with the results of NMR cross-linking density test.By compressing the stress relaxation experiment of natural rubber, the modified standard linear solid model (SLS model). It is found that the aging is dominated by oxidation and cross-linking reaction in the short-term thermal aging process, which is consistent with the cross-linking density and the DSC results.