Effects of plasticizers on the properties of breathable cellulose diacetate films

Cellulose diacetate (CDA) is a bio-based polymer of high hydrophilicity and low crystallinity for intrinsic moisture conductor. However, strong hydrogen bond induces interactions and close arrangement of CDA chains, which not only induces the difficulties for their thermal processing, but also restricts their water vapor permeability (WVP) properties. In this paper, diacetin (DA) and triacetin (TA) were chosen as green and effective plasticizers for CDA. The plasticizing CDA blends were evaluated by rheology, melt flow rate, mechanical test, Fourier transform infrared spectrometer (FTIR). The WVP of plasticized CDA film was monitored by a moisture-permeable cup. The biodegradability of CDA materials is indicated with molecular weight analyzed by gel permeation chromatography (GPC) after hydrolysis process in cellulase solution. The red shift of stretching vibrational band of carbonyl bond in FTIR demonstrates the interaction between plasticizer and CDA. The melt fluidity of CDA material increases with the increasing amount of plasticizers. The modulus and tensile strength decrease, and the elongation at break increases as a whole by blending plasticizers. DA has one more hydroxyl than TA with better compatibility with CDA. Therefore, DA brings better chain mobility of CDA chain and accordingly better improvement in moisture permeability than TA on the same load. For the CDA-DA, with the DA content increasing, the WVP is raised from 18.2 × 10^–13 g·cm⁻¹·s⁻¹·Pa⁻¹ to 23.6 × 10^–13 g·cm⁻¹·s⁻¹·Pa⁻¹. This study suggests an effective way to increase WVP of films by enhancing the chain mobility and hydrophilicity.