Biodegradable Polymer Blends/Composites, With High Performance Characteristics, for Packaging Application

Govindan, Srinivasan
Ramos, Maximiano
Al-Jumaily, Ahmed
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Doctor of Philosophy
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Auckland University of Technology

This research project focuses on developing biodegradable polymer films for flexible packaging applications with high-performance characteristics.

During this research, three biodegradable polymers, namely, Polybutylene succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic acid (PLA), were selected and investigated to improve their performance.

Three strategies were adopted for improvement; namely, i) by blending with Polycaprolactone (PCL), a highly biodegradable polymer, ii) by plasticization with three plasticizers, and iii) by the fabrication of nanocomposites/ by incorporating nanomaterials such as nano-cellulose and nano-clay.

Polymer films of various compositions were fabricated by injection molding, followed by hot-pressing and carried out an investigation of the tensile properties, water vapor transmission rate (WVTR)/ barrier properties, and biodegradability characteristics (in-home compost & seawater medium) of polymer films, and analyzed the effect of blending, plasticization, and nanomaterials.

The investigation carried out on blending of PBS, PHB, and PLA with PCL (with 10, 20, 30, and 40 wt% PCL) demonstrated enhancement of tensile elongation (ε), improvement in water vapor barrier property (decrease in WVTR), and increase in the biodegradation rate (in-home compost and seawater), with the addition of PCL, though with a slight decrease in tensile strength (σ). It was concluded from the studies on blending that polymer blending with approximately 10-20wt % PCL offer overall enhancement of polymer properties.

Studies carried out on plasticization of PBS-PCL20, PHB-PCL20, and PLA-PCL20 blends, with three plasticizers, [GTA, a monomeric plasticizer P1; Ultramoll, a polymeric plasticizer P2; and mixed plasticizer P3 ( 1: 1 mix of P1 and P2)], with 5 wt% plasticizer loading, indicated, a substantial increase in elongation at break and biodegradability, with the addition of all the three plasticizers, though with a decrease in tensile strength (σ) and water vapor barrier property. It was concluded from the plasticization study that mixed plasticizer P3 offers the best overall performance enhancement.

An investigation carried out on nanocomposites of PBS, PHB and PLA, prepared by incorporating nano cellulose and nano clay ( 1, 3, and 6 wt%) in plasticized blends, ( PBS-PCL20-P3, PHB-PCL20-P3, and PLA-PCL20-P3) demonstrated improved water vapor barrier properties (decrease in WVTR), improved tensile strength (except for PLA), and higher biodegradation rate with the addition of both nano cellulose and nano clay. Though a decrease in elongation at break was observed with nanomaterials' addition to the plasticized blends, the cumulative improvement was observed for neat polymers.

Studies on nanomaterial content's effect indicated that the best performance was obtained with 1wt % nano cellulose and 6% nano clay, which differ only slightly in properties.

The nanocomposites with nano cellulose (1wt%), namely PBS-PCL20-P3-nCell1, PHB-PCL20-P3- nCell1, and PLA-PCL20-P3- nCell1 was found to have improved properties, such as higher tensile elongation by 50%, 168%, and 494%; higher water vapor barrier properties (lesser WVTR) by 59%, 46% and 48%; higher biodegradation rate in home compost media by 56%, 13%, and 93%; and higher biodegradation rate in seawater media (after 180 days) by 79%, 10%, and 92% respectively, compared to neat PBS, PHB and PLA. The nanocomposites with 6 wt% nano clay were found to have slightly higher tensile strength and water vapor barrier properties, though slightly lower ductility and biodegradability. Hence nanocomposites with 1% nano cellulose or 6% nano clay may be used depending on the application requirement.

The present investigation thus demonstrated the overall performance improvement of PBS, PHB, and PLA polymers through blending, plasticization, and nanomaterials.

The present investigation has also generated valuable data on biodegradation of PBS, PHB and PLA polymers, PCL blends, plasticized blends, and nanocomposites under ambient temperature/ home composting conditions and marine environment, which will be of great help for future researchers.

Biodegradable polymer , Polymer blends/composite , Biodegradation , Tensile Test , Barrier Properties
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