纤维素填充改性聚乳酸的研究

发布时间：2018-02-13 03:07

本文关键词： 乙酰化改性纤维素聚乳酸复合材料超临界发泡　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文主要研究了三种纤维素(纳米纤丝纤维素NFC、纳米晶体纤维素NCC、α-纤维素)的乙酰化改性,并采用改性后的mNFC、mNCC、mα-纤维素,用溶剂共混法制备了改性纤维素增强的纤维素/聚乳酸复合材料,尝试用安全、无毒无害无污染的超临界二氧化碳工艺制备微孔发泡材料。乙酰化改性成本较低,且材料表面取代度较高。FTIR、接触角测试说明了纤维素中的部分羟基被乙酰基成功取代,亲水性明显降低,有助于改善纤维素与聚乳酸的界面相容性。其中由~1HNMR可计算得到三种纤维素乙酰化改性的取代度(DS):mNCC为1.32,mNFC为1.62,mα-纤维素为1.98。XRD和TEM显示了改性略微降低了纤维素的结晶度,但改性后的纤维素仍保留了原本的晶体结构,改性多发生在纤维素的表面。二氯甲烷作为溶剂易挥发,用溶剂共混法分别制备mNFC/PLA、mNCC/PLA、mα-纤维素/PLA复合材料,操作过程简单,溶剂残留少。力学性能测试显示了添加mNFC有利于提高聚乳酸的拉伸强度,且随着含量的增加,拉伸强度逐渐增大,断裂伸长率与之相反。TG说明了改性后的聚乳酸复合材料,热稳定性有所下降,而DSC说明了 Tg和Tm都有明显的提高。紫外光谱表征说明mNFC含量增加,透光率下降,透明性降低。对纤维素/聚乳酸复合材料的超临界发泡进行了尝试研究。在泄压法发泡工艺中,将发泡温度提高到接近复合材料的熔点附近,延长保压时间(20h左右),可促进二氧化碳在聚乳酸中的充分溶解,达到饱和状态。SEM观察表明在树脂基体中可观察到超临界二氧化碳形成的泡孔。同时对升温法发泡工艺进行了初步探索,但为获得泡孔形态均一、膨胀率较大的发泡材料,其最佳工艺条件仍需要进一步探索。
[Abstract]:In this paper, the acetylation modification of three kinds of cellulose (nano-fiber cellulose NFC, nanocrystalline cellulose NCC-a-cellulose) was studied, and the modified mNFCnCCM 伪 -cellulose was used. Cellulose / polylactic acid composites reinforced by modified cellulose were prepared by solvent blending method. Microcellular foaming materials were prepared by a safe, innocuous and innocuous supercritical carbon dioxide process. The cost of acetylation modification was low. The results of surface substitution. FTIR and contact angle test showed that some hydroxyl groups in cellulose were successfully replaced by acetyl groups, and the hydrophilicity of cellulose decreased obviously. The interfacial compatibility between cellulose and poly (lactic acid) can be improved by 1H NMR. Three kinds of cellulose modified by acetylation can be calculated as DS / MNCC = 1.32mNFC = 1.62mNFC = 1.98.XRD and TEM show that the crystallinity of cellulose is decreased slightly. However, the modified cellulose still retains its original crystal structure, and the modification mostly occurs on the surface of the cellulose. Dichloromethane is volatile as a solvent, and the mNFC / PLAC / MNCC / PLAm 伪 -cellulose / PLA composite is prepared by solvent blending method. The operation process is simple. The mechanical properties test showed that the addition of mNFC was beneficial to increase the tensile strength of polylactic acid, and the tensile strength gradually increased with the increase of content, and the elongation at break was opposite to that of the modified PLA composite. The thermal stability decreased, while DSC showed that TG and TM were improved obviously. UV spectra showed that the content of mNFC increased and the transmittance decreased. The supercritical foaming of cellulose / poly (lactic acid) composites was studied. In the pressure-release foaming process, the foaming temperature was raised to close to the melting point of the composite. Prolonging the pressure holding time of about 20 h can promote the full dissolution of carbon dioxide in polylactic acid. SEM observation showed that the foam formed by supercritical carbon dioxide could be observed in resin matrix. The optimum technological conditions still need to be further explored.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332

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