木质素基聚电解质薄膜的制备及其力学性能

苏玲; 庞久寅; 任世学; 李淑君; 姜贵全

doi:10.13332/j.1000-1522.20180281

摘要:

目的对工业废弃碱木质素改性制备阳离子木质素聚电解质，将其与聚乙烯醇改性产物羧甲基化聚乙烯醇复合制备聚电解质复合薄膜。分析不同因素对聚电解质薄膜力学性能的影响，并对薄膜结构、热稳定性等进行表征，为木质素基聚电解质在缓释、地膜、包装方面的应用提供理论依据。

方法首先对木质素和聚乙烯醇分别进行季铵化和羧甲基化改性，制备阴、阳离子聚电解质。以甲醛为交联剂，聚乙烯醇为成膜剂，采用流延法制备三甲基木质素季铵盐/羧甲基化聚乙烯醇(TLQA/CMPVA)反应薄膜，通过红外光谱、扫描电镜、热重分析等对聚电解质薄膜结构、形貌、热性能进行表征。

结果木质素季铵盐中季铵根离子质量摩尔浓度为1.81 mmol/g，羧甲基化聚乙烯醇中羧酸根离子为0.62 mmol/g。制备具有较佳力学性能的聚电解质薄膜的条件为：TLQA/CMPVA反应薄膜的固含量为10%，固含中聚乙烯醇(PVA)质量分数为30%，三甲基木质素季铵盐(TLQA)和羧甲基化聚乙烯醇(CMPVA)(质量比为3:7)的质量分数为70%，甲醛加入质量分数为3.88%，溶液pH值为9。所制备聚电解质反应薄膜的最佳断裂伸长率为222.13%，拉伸强度为6.80 MPa。聚电解质反应薄膜的平面较光滑，断面不平整，聚电解质共混薄膜平面粗糙。聚电解质反应薄膜分子结构中有醚键形成；聚电解质反应薄膜的热稳定性大于聚电解质共混薄膜的热稳定性。

结论木质素和聚乙烯醇改性后，通过加入成膜剂聚乙烯醇、交联剂甲醛，聚电解质薄膜热稳定性得到提高，可获得具有较好力学性能和缓释性能的TLQA/CMPVA聚电解质反应薄膜。

Abstract:

ObjectiveThe industrial waste lignin was modified to prepare trimethyl-lignin quaternary amine salt (TLQA). The polyelectrolyte film was prepared by compounding TLQA with carboxymethylated polyvinyl alcohol (CMPVA) which was the modified product from polyvinyl alcohol. The influence of different factors on the mechanical properties of polyelectrolyte films was analyzed, and the structure and thermal stability of the films were characterized. The results will provide theoretical basis for the application of lignin-based polyelectrolytes in sustained release, plastic film and packaging.

MethodFirst, quaternization of lignin and carboxymethylation of polyvinyl alcohol were carried out respectively to prepare cationic and anionic polyelectrolytes. With formaldehyde cross-linking agent and polyvinyl alcohol film-forming agent, TLQA/CMPVA reaction film was prepared by a casting method. The structure, morphology and thermal properties of polyelectrolyte films were characterized by FTIR, SEM and TG.

ResultThe molality of R₄N⁺ of TLQA was 1.81mmol/g, and that of —COO^- of CMPVA was 0.62 mmol/g. The optimum conditions to prepare film of best mechanical properties were as follows: the total solid content of polyelectrolyte crosslinked film was 10%, polyvinyl alcohol accounted for 30% of the solid content, TLQA and CMPVA accounted for 70% of the solid content (mass ratio of TLQA to CMPVA was 3:7), and formaldehyde mass fraction was 3.88%, pH 9. Elongation-at-break (EB) and tensile strength (TS) of TLQA/CMPVA reaction film were 222.13% and 6.80 MPa, respectively. The surface of reaction film was smooth and the section was uneven, while the surface of blend film was rough. The ether bond was formed in TLQA/CMPVA reaction film. The thermal stability of TLQA/CMPVA reaction film increased after formaldehyde crosslinking.

ConclusionWith polyvinyl alcohol film-forming agent and formaldehyde cross-linking agent, TLQA/CMPVA reaction film with good slow-release performance and improved thermal stability can be obtained by the modification of lignin and polyvinyl alcohol.

木质素基聚电解质薄膜的制备及其力学性能

Preparation of lignin-based polyelectrolyte film and its mechanical properties