Sirviö Juho Antti, Honkaniemi Samuli, Visanko Miikka, Liimatainen Henrikki
Fibre and Particle Engineering, University of Oulu , P.O. Box 4300, FI-90014 Oulu, Finland.
Fibre and Particle Engineering and Thule Institute, University of Oulu , P.O. Box 4300, FI-90014 Oulu, Finland.
ACS Appl Mater Interfaces. 2015 Sep 9;7(35):19691-9. doi: 10.1021/acsami.5b04879. Epub 2015 Aug 28.
Long and flexible cellulose nanofibrils or stiff and short cellulose nanocrystals (CNCs) are both promising lightweight materials with high strength and the potential to serve as reinforcing agents in many polymeric materials. In this study, bifunctional reactive cellulose nanocrystals (RCNCs) with carboxyl and aldehyde functionalities were used as reinforcements to prepare acetal-bonding cross-linked poly(vinyl alcohol) (PVA) films. Two RCNCs were obtained through the mechanical homogenization of partially carboxylated dialdehyde cellulose (DAC) with a residual aldehyde content of 0.55 and 1.93 mmol/g and a carboxyl content of 1.65 and 1.93 mmol/g, respectively. The mechanical, thermal, and barrier properties of PVA-RCNC films with a variable mass ratio of RCNCs (0.5-10%) were determined. Reference CNCs without reactive aldehydes were obtained through the reduction of aldehyde functionalities to primary hydroxide groups, and their reinforcing effect was compared to RCNCs. With the addition of 10% acetal-bonding RCNCs with respect to PVA weight, the tensile strength and Young's modulus were up to 2-fold greater than those of pure PVA film. An addition of only 0.5% RCNCs improved the tensile strength of the PVA film by 66% and the modulus by 61%. In comparison, a significantly lower reinforcing effect (19% with CNC loading of 0.5%) was found using reference CNCs. PVA's effective oxygen barrier and thermal properties were preserved when RCNCs were introduced into the films.
长而柔韧的纤维素纳米纤维或硬而短的纤维素纳米晶体（CNC）都是很有前景的轻质材料，具有高强度，并且有潜力在许多聚合材料中用作增强剂。在本研究中，具有羧基和醛基官能团的双功能反应性纤维素纳米晶体（RCNC）被用作增强剂来制备缩醛键交联的聚乙烯醇（PVA）薄膜。通过对部分羧化二醛纤维素（DAC）进行机械均质化获得了两种RCNC，其残余醛含量分别为0.55和1.93 mmol/g，羧基含量分别为1.65和1.93 mmol/g。测定了RCNC质量比可变（0.5 - 10%）的PVA - RCNC薄膜的力学、热学和阻隔性能。通过将醛基官能团还原为伯羟基获得了不含反应性醛的参比CNC，并将它们的增强效果与RCNC进行了比较。相对于PVA重量添加10%的缩醛键合RCNC时，拉伸强度和杨氏模量比纯PVA薄膜高出2倍。仅添加0.5%的RCNC就能使PVA薄膜的拉伸强度提高66%，模量提高61%。相比之下，使用参比CNC时发现增强效果显著较低（CNC负载量为0.5%时为19%）。当将RCNC引入薄膜中时，PVA的有效氧气阻隔性能和热性能得以保留。
