On the Synthesis and Characterization of Polylactic Acid, Polyhydroxyalkanoate, Cellulose Acetate, and Their Engineered
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JMEPEG https://doi.org/10.1007/s11665-020-04594-3
On the Synthesis and Characterization of Polylactic Acid, Polyhydroxyalkanoate, Cellulose Acetate, and Their Engineered Blends by Solvent Casting Saud Abu Aldam, Maharshi Dey, Sabah Javaid, Yun Ji, and Surojit Gupta (Submitted December 23, 2019) In this paper, we report the synthesis of polylactic acid (PLA), polyhydroxyalkanoate (PHA), cellulose acetate (CA), and their binary and ternary blends by solvent casting. PLA, PHA, and CA had tensile strengths of 59.4, 17.4 and 23.9 MPa, respectively. Differential scanning calorimetry (DSC) analysis showed that binary blends of PLA and PHA are immiscible in each other. During mechanical testing, 50 PHA–50 PLA showed mild enhancement and had a tensile strength of 37.8 MPa as compared to 75 PLA– 25 PHA and 25 PLA–75 PHA, which had tensile strengths of 31.2 and 22.9 MPa, respectively. This may be due to the formation of crystallized PHA in PLA matrix, which was further supported by the DSC results and analysis of fractured surface of 50 PHA–50 PLA. The addition of 24, 49, 74, and 89.5 vol.% CA in the PHA matrix improved the tensile strength to 25.8, 25.9, 44.9, and 42.4 MPa, respectively. Based on DSC results, it is hypothesized that the strength enhancement is due to synergistic effect of crystallization of PHA and plasticizing effect of CA additions. The addition of CA in PLA caused severe demixing, and the strength of PLA matrix reduced to 25.8 and 21.4 MPa after the additions of 24 and 49 vol.% CA in PLA matrix, respectively. In ternary blends, the addition of 5 and 19 vol.% CA degraded the strength of PHA–PLA to 22.6 and 21.8 MPa, respectively. However, after the addition of higher concentrations of CA, for example 32, 59, and 79 vol.% CA additions in PHA–PLA matrix, the strength improved to 32.9, 39.3, and 32.1 MPa, respectively. The enhancement in strength can be explained by the increase in amorphous nature of these blends, which was further supported by the DSC results. Keywords
bioplastic, blend design, sustainability
1. Introduction 1.1 Biopolymers and Sustainable Economy Circular economy has emerged as an important component of sustainable economic development (Ref 1). Fundamental research on plastics from the perspective of circular economy and sustainability has become important for our current generation (Ref 2). Based around the principles of circular economy, there is an urgent need for producing plastics from renewable sources which can potentially eliminate the deleterious effect of plastic usage on environment (Ref 3). Plastics derived from renewable sources are referred to as bioplastics (Ref 4). A sub-category of bioplastics is renewable and biodegradable. Some examples of the biodegradable This article is an invited paper selected from presentations at the ‘‘11th International Symposium on Green and Sustainable Technologies for Materials Manufacturing and Processing,’’ held during Materials Science & Technology (MS&TÕ19), September 29–October 3, 2019, in Portland, OR
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