Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25 wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNC_m) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNC_w). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517 g m⁻² day⁻¹ was the PU/PVDC film reinforced with 0.1 wt% of CNC_m. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14 days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

中文翻译：

---

基于不同类型纤维素纳米晶体增强的PU / PVDC共混物的太阳能电池密封剂的透明度，防潮性能和性能

使用酸水解处理制备了两种不同类型的纤维素纳米晶体，分别来自水葫芦纤维和微纤化纤维素（MFC）。这些纤维素纳米晶体（CNC）进一步用作与25 wt％的聚偏二氯乙烯（PVDC）混合的聚氨酯（PU）的阻挡增强填料。这项研究的目的是研究CNC的类型和浓度对聚合物复合膜的机械，光学和阻隔性能的影响。将获得的复合膜用作封装材料以延长染料敏化太阳能电池（DSSC）的寿命的可行性也是令人关注的。MFC生成的棒状纤维素纳米晶体（CNC _m），而酸水解的风信子导致形成球形纤维素纳米晶体（CNC _w）。无论采用哪种CNC，复合膜的光学透明度均保持在60％以上。根据这项研究的结果，水蒸气透过率最低的最有效的薄膜是0.0517 g m ^-2 天^-1，是用0.1 wt％的CNC _m增强的PU / PVDC薄膜。用这种复合材料制成的密封剂可以将DSSC器件的寿命延长14天，标准化PCE值为0.78。总的来说，这项工作表明仅考虑聚合物密封剂的阻隔性能不足以确保该系统有效。还应考虑到密封剂和电极之间的界面粘附以及所制造电池内部的聚合物和化学物质之间的某些副反应。