Biodegradable Poly (Butylene Adipate-co-terephthalate) (PBAT)/ Polylactic Acid (PLA)/ Tetrapod-ZnO Whisker Composite Film with Improved Properties
Creators: name: Zhao, Zhibo
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400302
subject: Biomaterials
classificationCode: 401602
subject: Composite and hybrid materials
classificationCode: 401708
subject: Tribology

description: The environmental issue posed by the non-biodegradable polymer blend film underscores the necessity for identifying alternatives to mitigate their impact. Substituting non-biodegradable films with biodegradable polymer films emerges as a promising solution to address environmental concerns. Considering these environmental issues, degradable poly-mers particularly biodegradable polymers have gained prominence as substitutes for these non-degradable polymer materials. Polylactic acid (PLA), among these biodegradable poly-mers, stands out due to its widespread applications resulting from available ingredients and optimised properties. However, the brittleness and other limitations have impeded its further development. 
In this master project, the properties of PLA are modified by blending with another biode-gradable polymer poly (butylene adipate-co-terephthalate) (PBAT), known for its superior ductile properties. Additionally, these blends are further reinforced with Tetrapod-Zinc Ox-ide whiskers (t-ZnOw) fillers. In this project, the ratio of PLA and PBAT was fixed at 30/70 due to the content of approximately 65%~70% having the best properties in impact and ten-sile suitable for film blowing. The content of t-ZnOw varies at 0%, 1%, 3%, and 7%. The primary objective of this research project is to elucidate how the content of t-ZnOw impacts the properties of the PBAT/PLA blends and investigate the content of t-ZnOw that could im-pact the PBAT/PLA blends to have the optimised properties in crystalline, rheological, me-chanical and some functional properties and be used as a potential packaging film. The study also delves into the impact of a chain extender on polymer compatibility and the use of a silane coupling agent to modify t-ZnOw.
 The thesis also focuses on the blend melt flow properties of the PBAT/PLA/t-ZnOw blends encompassing the crystallisation properties and the rheological properties of the PBAT/PLA/t-ZnOw blends. The primary objective is to identify the optimal processing con-ditions for PBAT/PLA blends. In the crystallinity analysis, a quantitative methodology has been employed to scrutinize the crystallisation kinetic of the cooling. The objective is to discern the dimension of the crystal growth in the isothermal and non-isothermal way and the optimum temperature or heating rate for the PLA/PBAT/t-ZnOw with the highest crys-talline rate and achieve the best mechanical and optical properties. The melt flow rheologi-cal investigations using the isothermal frequency scan and the temperature range frequency scan of the samples to identify the impact of t-ZnOw on the properties of the PBAT/PLA, determine the polymer blends are incompatible and the blends do not follow the time-temperature superposition principle due to thermogeological complexity.
The next section addresses the composite film properties of the PBAT/PLA/t-ZnOw. This section focuses on the method of producing the PBAT/PLA/t-ZnOw film and the perfor-mance related to the practical application of PBAT/PLA/t-ZnOw film such as the optical, mechanical, barrier and anti-bacterial properties. The processing method for the PBAT/PLA film preparation emphasizes the formulations, processing equipment, processibility condi-tions and most importantly the usage of a silane coupling agent for the filler. Due to the strong polarity of the t-ZnOw, which poses challenges for direct filling into the PBAT/PLA matrix, the surface modification was performed through the coupling agent to alter the po-larity of the t-ZnOw and better integrate into the PBAT/PLA matrix. The practical properties of the polymer film are evaluated through various tests including mechanical, optical, mor-phology, barrier, and anti-bacterial assessments. The chapter identified how the properties are impacted by the t-ZnOw and determined the optimised ratio of t-ZnOw in enhancing the properties in comparison to some commonly used non-biodegradable film as a potential an-ti-bacterial packaging film material.
The last section addresses the degradation of the sample film. As a fully degradable film ma-terial, the enzymatic degradation of the PBAT/PLA/t-ZnOw sample film is an area of lim-ited exploration. In this part, the protease is introduced to facilitate the degradation of the sample film over varying time periods. Subsequent to the degradation process, the related evaluation has been carried out on the degraded film including the weight loss, morphology change, alterations in functional groups and modifications in crystalline properties. The analysis compared the properties of the sample before and after enzyme degradation, allow-ing for a further study on the impact of t-ZnOw on the degradation process. 
In summary, this research contributes to the understanding of the enhanced performance of the fully degraded PBAT/PLA film properties through t-ZnOw addition and their potential applications. The findings are anticipated to play a pivotal role in developing the degrada-ble polymer material film and identifying alternatives to the non-biodegradable polymer film to mitigate environmental concerns.