Title: Thermal, mechanical and morphological characterization of plasticized PLA-PHB blends Authors
Submitted to: Polymer Degradation and Stability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 28, 2012
Publication Date: September 10, 2012
Citation: Abdelwahab, M.A., Flynn, A., Chiou, B., Imam, S.H., Orts, W.J., Chiellini, E. 2012. Thermal, mechanical and morphological characterization of plasticized PLA-PHB blends. Polymer Degradation and Stability. 97(9):1822-1828. Interpretive Summary: Biomass such as agricultural residues have shown promise for use in eco-efficient packaging to replace petroleum feedstock without competing with food crops. Poly(lactic acid) (PLA) is a biodegradable polymer that can be produced from renewable resources and is of interest to the packaging industry due to its availability and low cost. Poly(3- hydroxybutyrate) (PHB) is a biodegradable thermoplastic polymer produced by microorganisms. Both PLA and PHB have excellent thermal and mechanical properties and are used in consumer products due to their biocompatibility, biodegradability and sustainability. Both PLA and PHB have poor processing properties and are brittle at room temperature. Thus, modifications have been proposed to improve their processing and mechanical properties. Blending is much easier and faster than copolymerization methods. A new polyester plasticizer has been developed from mostly renewable resources. This plasticizer is in commercial development and goes by the commercial name of Lapol 108. This plasticizer has high molecular weight, is highly branched and is derived from more than 50% renewable resources. In this paper, we studied the effects of Lapol 108 on PHB, PLA and PLA/PHB blends to create a new type of eco-friendly blend material suitable for single-use applications, such as fast-food packaging.
Technical Abstract: A blend of poly(lactic acid) (PLA) (75% by weight) and poly(3-hydroxybutyrate) (PHB) (25% by weight) with a polyester plasticizer (Lapol 108) at two different concentrations (5 and 7% by weight per 100 parts of the blends) were investigated by TGA, DSC, XRD, SEM, mechanical testing and biodegradation studies. PLA/PHB blends showed a good distribution of the major components and absence of phase separation. XRD showed that the original crystal structure of PHB in the PLA75/PHB25 blend had been disturbed. DSC curves of PLA or PHB with plasticizer exhibited one Tg value, indicating that both major blend components are miscible. The Tg values also decreased with increased amount of plasticizer and showed good correlation to the Fox Equation, The melting temperature of PLA and PHB blends mostly did not change with an increase in plasticizer content, and the thermal stability of PLA and PHB was not affected. Also, the elongation at break of the PLA/PHB blend was greatly improved with the addition of plasticizer. In addition, in preliminary biodegradation studies carried in natural compost neat PHB showed some biodegradation, whereas the samples containing PLA did not experience a substantial biodegradation. This last aspect is worthy of further investigation in a more comprehensive and detailed approach.