杜仲胶和天然橡胶的土壤老化探讨

Investigation on soil aging of eucommia ulmoides gum and natural rubber

采用自然老化方法对杜仲胶(EUG)和天然橡胶(NR)进行了土壤老化研究.将杜仲胶和天然橡胶生胶样片置于室外土壤中进行土壤老化,通过红外光谱、凝胶渗透色谱、X射线光电子能谱、拉伸实验等对比研究了老化时间对二者结构和性能的影响.结果表明,杜仲胶随着老化时间的延长出现—OH和COO—官能团,分子主链及结构网络未出现明显的变化,且老化过程中始终保持结晶聚合物的性质,在老化150d时数均相对分子质量降低了5.0×10^(4),抗拉强度和断裂伸长率分别降低了14.9MPa和64%;天然橡胶随着老化时间的延长出现—OH,CO,COO—,C—O—C官能团,老化150d时数均相对分子质量降低了8.1×10^(4),抗拉强度降低了1.29MPa,断裂伸长率提高了64%,且老化过程中氧化降解和交联反应同时存在,老化前期以降解为主,后期产生交联;相比之下,天然橡胶抗土壤老化能力更差.

The natural aging method was used to study the soil aging of Eucommia ulmoides gum(EUG)and natural rubber(NR).Samples of EUG and NR were placed in outdoor soil for soil aging,and the effects of aging time on their structure and properties were compared through infrared spectroscopy,gel permeation chromatography,X-ray photoelectron spectroscopy,and tensile testing.The results showed that with the extension of aging time,EUG exhibited the emergence of—OH and COO—functional groups,while the main chain and structural network did not showed significant changes.The crystalline polymer properties were maintained throughout the aging process.Aged for 150 days,the number-average molecular weight of EUG decreased by 5.0×10^(4),the tensile strength and fracture elongation decreased by 14.9 MPa and 64%,respectively.Natural rubber exhibited the emergence of—OH,C O,COO-,and C—O—C functional groups with increasing aging time.At 150 days of aging,the number-average molecular weight of NR decreased by 8.1×10^(4),and the tensile strength decreased by 1.29 MPa,and the fracture elongation rate increased by 64%.During the aging process,oxidation degradation and crosslinking reactions coexisted.In the early stage of aging,degradation is the main reaction,and crosslinking occurs in the later stage;in contrast,natural rubber has a poorer ability to resist soil aging.