Why and how should PBAT be modified?
As the leader in biodegradable polymers, PBAT will be widely used in packaging materials (garbage bags, food containers, film packaging), sanitary products (diaper backing, cotton swabs), biomedicine and other fields in the future.
However, PBAT has deficiencies in mechanical properties, thermal properties, barrier properties and production costs. In order to expand its application scope, a series of modifications should be carried out. In the future, the development of PBAT matrix composites with low cost and excellent comprehensive performance and good degradability, bacteriostasis and durability should be paid attention to and further studied.
1、 Improvement of mechanical properties of PBAT
1. Cellulose nanocrystals (CNC) can improve the mechanical properties and thermal stability of PBAT.
2. Thermoplastic starch (TPS) filling can significantly improve the tensile strength of PBAT.
3. Calcium carbonate filling can promote the crystallization of PBAT.
4. The blending of lignin and PBAT showed ideal tensile properties, and the cost could be significantly reduced by 36%.
2、 Improved barrier performance of PBAT
1. PBAT and PPC were blended, extruded and blown into a composite film. It was found that PBAT/PPC film had high tensile strength and tear strength.
2. When using 0.48% oriented graphene nanoflakes (volume fraction), the water vapor permeability of the prepared PBAT nano-composite film decreased by 80%, and the oxygen permeability decreased by more than 99%.
3. The PBAT matrix was mixed with unmodified and modified clay nanoparticles (sepiolite, montmorillonite and lithium fluoride montmorillonite), which significantly improved the overall thermal stability and barrier effect compared with pure PBAT nano-clay.
4. Polyurethane prepolymer (PUP) was modified with starch to improve its compatibility. With the increase of amylose content in the modified PUP, the crystallinity, hydrophobicity, oxygen barrier and mechanical properties of PBAT film (MSPF) were improved.
3、 PBAT-based antibacterial material
In recent years, non-toxic antibacterial agents embedded in polymer nanocomposites have gained potential commercial significance, mainly because they can be used to maintain food quality and ensure safety. Some scholars have already carried out research on bacteriostatic degradable plastics on other degradable plastics. These achievements can be transferred and applied to the development of biodegradable bacteriostatic plastics based on PBAT, providing technical and theoretical support for the subsequent realization of industrial production.
Wei et al. used potato starch and polyhexamethylene guanidine hydrochloride (PHGH) as raw materials to prepare antibacterial thermoplastic starch (ATPS) containing guanidine polymer by twin-screw extrusion. A non-leaching PBAT-based antibacterial biodegradable polymer was prepared by co-extrusion of ATPS and PBAT under the action of coupling agent 2,2 '- (1,3-phenylene) - diazoline (PBO). The non-leachability of the composite membrane was confirmed by washing and ring diffusion test. Even at a very low dose of PHGH (1.0mg/g PBAT film), excellent antibacterial activity against Escherichia coli could be obtained: the PBAT composite membrane with 6.4% ATPS mass fraction inactivated 99.99% of Escherichia coli within 15 seconds of contact. Considering the biodegradation rate of the antibacterial material, the biodegradation behavior and antibacterial performance of the material in three months before and after the soil burial test were studied in another work. Even in the presence of antibacterial agent PHGH, PBAT and starch can still be degraded, but the biodegradation rate is low. Thanks to the high retention rate of PHGH, despite three months of biodegradation test, the composite material still has a growth inhibition rate of more than 99% against Escherichia coli.
Using sodium benzoate (SB) as antibacterial agent, Mondal et al. prepared polybutylene adipate-co-terephthalate (PBAT)/organic clay (CMMT) nanocomposite film by solution mixing method. The water vapor transmission rate of the PBAT film added with 4% CMT nanocomposite decreased by 25.21%. The film is endowed with antibacterial ability while taking into account the water vapor barrier. Such composite materials with antibacterial properties can be applied to special scenarios such as food packaging and medical materials.
It is urgent to develop products with excellent basic performance and antibacterial properties based on PBAT in the disposable neighborhood of food packaging, medical and health care, so as to extend the shelf life of food and apply it in preventive medicine to replace the existing non-degradable plastic products. Adhering to the principle of green and sustainable development, expanding the application of PBAT-based degradable plastics still requires the joint efforts of more scientific researchers. Future development should focus on low cost and excellent comprehensive performance, focusing on bacteriostatic performance and durability.
