Design and development of environmentally friendly biodegradable nanocomposite
Chee, Siaw Soon.
Date of Issue2013
School of Materials Science and Engineering
Prospective applications of nanocomposite in producing environmentally friendly biodegradable packaging were investigated by incorporating nano-fillers into a biodegradable polymer matrix. Polylactic acid (PLA) was selected due to its biodegradability and wide acceptance as an alternative material to replace petroleum-based polymers. However, the unsatisfied toughness, poor barrier property and higher cost of PLA compared to petroleum-based polymers had restricted its potential widespread applications. In this work, nanoclay and carbon nanotube was incorporated into PLA to study their effect on the mechanical and functional properties of PLA. In this study, solvent casting technique is employed to prepare PLA\30B nanocomposite and followed by investigating its biodegradability, mechanical and thermal properties using series of materials characterization techniques. Two processing methods were prepared and compared the effect of different sequence of adding nanoclay into solvent or a pre-dissolved polymer solution plays an important role in proving dispersion of nanoclay in polymer. Processing method 1 is a type of conventional process obtained from literature involved adding nanoclay into a prepared polymer solution (pre-dissolving polymer pellets into a solvent). However for processing method 2 discussed in this study has a different sequence which polymer pellets are added only after a nanoclay-solvent suspension is prepared. Processing method 2 has shown that the nanoclay achieved greater extent of intercalated and even exfoliated nanoclay. Both the TEM and XRD analysis have revealed processing method 2 which promote swelling of nanoclay offers formation of greater extent of intercalated and exfoliated nanoclay compared to processing method 1. With formation of more intercalated and exfoliated nanoclay, elongation at break and toughness of PLA with addition of 1wt% of Cloisite 30B increased significantly up to 55.79% and 154.24%, respectively. However, the Young’s Modulus and ultimate tensile strength increased up to 18.34% and 4.83%. In order to achieve the aim to develop a biodegradable nanocomposite, biodegradability of nanocomposite was also evaluated using enzymatic degradation. PLA\30B (1%) sample which shows enhanced mechanical properties degraded completely after subjected to 6 days (144 hours) of enzymatic degradation. Many studies have shown that addition of carbon nanotube has shown remarkably improvement in mechanical and functional properties of virgin polymer. In this work, various weight percentages of MWNT were also added into PLA to study the effect of MWNT on the mechanical and thermal properties of nanocomposite. It has shown that mechanical and thermal properties of PLA improved tremendously with incorporation of well distributed carbon nanotube even at very low CNT content. Both the mechanical and thermal properties of PLA were greatly enhanced with addition a very low amount of nanoclay (Cloisite 30B) and MWNTs. It was found that the by optimizing the processing technique and nanoclay concentration which could influence the distribution of nanofiller in PLA exert critical influences over the properties of the nanocomposites. It was observed that there is an optimal concentration of nanofiller beyond which mechanical properties will deteriorate. With the enhanced mechanical properties and biodegradable nature, the nanocomposite developed with high strength, good toughness and biodegradability could serve as an environmentally friendly biodegradable packaging material.