Influence of Carboxylic Acids on Poly(lactic acid)/Thermoplastic Starch Biodegradable Sheets Produced by Calendering-Extrusion

Thermoplastic starch and poly(lactic acid) (PLA) blends have been studied as potential materials for the production of biodegradable packaging. However due to the hydrophilic characteristic of starch and hydrophobic nature of PLA, these polymers are incompatible at microscopic level and this fact interfere significantly in the mechanical properties of the obtained materials. Several compatibilizer have been investigated to improve the compatibility between these polymers, including carboxylic acids. Thus, this study evaluated the mechanical properties of thermoplastic starch and PLA sheets added of citric and adipic acids produced by flat extrusion (calendaring-extrusion) and stored at different relative humidity. The sheets containing citric acid were thinner, more resistant and showed higher values of elongation at break. The relative humidity of storage interfered significantly in the mechanical properties, possibly due to the plasticizing effect of water. Citric acid was an additive which improved the mechanical properties of the starch and PLA sheets produced by flat extrusion. Furthermore, it is important to control the relative humidity of storage to not alter the mechanical properties of the starch based blends.DOI: 10.14685/rebrapa.v5i2.164

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Mechanical, Thermal, and Morphological Properties of Thermoplastic Starch/Poly(lactic acid/Poly(butylene adipate-co-terephthalate) Blends

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.970.312 ◽

2014 ◽

Vol 970 ◽

pp. 312-316

Author(s):

Sujaree Tachaphiboonsap ◽

Kasama Jarukumjorn

Keyword(s):

Lactic Acid ◽

Impact Strength ◽

Interfacial Adhesion ◽

Tensile Modulus ◽

Thermoplastic Starch ◽

Morphological Properties ◽

Poly Lactic Acid ◽

Melt Blending ◽

Elongation At Break ◽

Blending Method

Thermoplastic starch (TPS)/poly (lactic acid) (PLA) blend and thermoplastic starch (TPS)/poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blend were prepared by melt blending method. PLA grafted with maleic anhydride (PLA-g-MA) was used as a compatibilizer to improve the compatibility of the blends. As TPS was incorporated into PLA, elongation at break was increased while tensile strength, tensile modulus, and impact strength were decreased. Tensile properties and impact properties of TPS/PLA blend were improved with adding PLA-g-MA indicating the enhancement of interfacial adhesion between PLA and TPS. With increasing PBAT content, elongation at break and impact strength of TPS/PLA blends were improved. The addition of TPS decreased glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm) of PLA. Tgand Tcof TPS/PLA blend were decreased by incorporating PLA-g-MA. However, the presence of PBAT reduced Tcof TPS/PLA blend. Thermal properties of TPS/PLA/PBAT blends did not change with increasing PBAT content. SEM micrographs revealed that the compatibilized TPS/PLA blends exhibited finer morphology when compared to the uncompatibilized TPS/PLA blend.

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