Preparation and Mechanical Properties of PBAT/Silanized Cellulose Composites

Abstract

Polybutylene adipate-terephthalate (PBAT) is a fully biodegradable polyester, which has been proven to be the most suitable alternative to traditional plastics. However, due to the low strength of PBAT (17.2 MPa) and high price, the use of PBAT has a degree of limitations. To obtain a cost-effective and high-performance composite material of PBAT, for this study we selected microcrystalline cellulose, which is inexpensive and easily available, as the reinforcing medium. However, due to the hydrophobicity of PBAT, the mechanical properties of PBAT when mixed with hydrophilic cellulose were low. In order to improve the compatibility of cellulose and PBAT, this study selected hexadecyltrimethoxysilane (HDTMS) containing long carbon chains to silanize microcrystalline cellulose (MCC) to obtain silanized cellulose (SG). Three types of SGs with different degrees of silanization were obtained by controlling HDTMS with different mass ratios (1:10; 3:10; 5:10) to react with MCC. Characterization of these three types of SGs was conducted using FTIR, TEM, and water absorption analysis. The results demonstrated the successful synthesis of SG. With the increase in the reaction ratio of HDTMS and MCC, the size of the nanoparticles increases, and the water absorption decreases significantly. Subsequently, PBAT/SG composites were prepared by blending three kinds of silanized cellulose with PBAT in different proportions by the sol-gel method. To study the thermal stability and compatibility, the mechanical properties of the composites were evaluated, including thermogravimetric testing, scanning analysis, and dynamic thermomechanical testing. The optimal blending ratio and the optimal type of silane cellulose were found. Analysis of the mechanical properties revealed that the tensile strength initially increased and then decreased with increasing blending ratio for all three composites tested. Among them, the PBAT/SG2 composites exhibit superior performance, with a maximum tensile strength reaching 22 MPa at an 85/15 blending ratio, nearly 30% higher than that of pure PBAT alone. The addition of SG significantly improved the strength of the PBAT, and SG2 is more suitable for preparing high-strength composite materials. In addition, after the addition of SG, the yield stress of the composite is improved while maintaining good thermal stability. Both the SEM and DMA results indicated good compatibility of the PBAT/SG composites. This study provides a new idea for the industrial-scale development of degradable polyesters with low cost and good mechanical properties.