Effect of the Addition of Natural Rice Bran Oil on the Thermal, Mechanical, Morphological and Viscoelastic Properties of Poly(Lactic Acid)

Maria Cristina Righetti,Maria Irakli,Patrizia Cinelli,Andrea Lazzeri,Carlo Andrea Massa,Norma Mallegni

doi:10.3390/su11102783

Abstract

For the first time in this study, the utilization of rice bran oil (RBO) as possible totally eco-friendly plasticizer for poly(lactic acid) (PLA) has been investigated. For comparison, the behavior of soybean oil (SO) has also been analyzed. Both oils are not completely miscible with PLA. However, certain compatibility exists between PLA and (i) RBO and (ii) SO, because demixing is not complete. Although not totally miscible, RBO and SO are able to reduce the viscosity of the PLA+RBO and PLA+SO mixtures, which attests that a small amount of RBO or SO can be successfully added to PLA to improve its processability. Additionally, the mechanical properties of the PLA+RBO and PLA+SO mixtures exhibit trends typical of plasticizer-polymer systems. More interestingly, RBO was found to accelerate the growth of PLA α’-crystals at a low crystallization temperature. This feature is appealing, because the α’-phase presents lower elastic modulus and higher permeability to water vapor in comparison to the α-phase, which grows at high temperatures. Thus, this study demonstrates that the addition of RBO to PLA in small percentages is a useful solution for a faster preparation of PLA materials containing mainly the α’-phase.

Highlights

Bio-based and/or biodegradable polymers [1] represent an important alternative to petroleum-derived polymers, which are commonly non-degradable, in some cases they can be de-polymerized, and made sustainable [2]
rice bran oil (RBO) and soybean oil (SO) are able to reduce the viscosity of the poly(lactic acid) (PLA)+RBO and PLA+SO mixtures, which attests that a small amount of RBO or SO can be successfully added to PLA to improve its processability
The main aim of the present paper is to investigate how the addition of the totally eco-friendly RBO can modify the final thermal, mechanical, morphological and viscoelastic properties of PLA-based materials

Summary

Introduction

Bio-based and/or biodegradable polymers (bioplastics) [1] represent an important alternative to petroleum-derived polymers, which are commonly non-degradable, in some cases they can be de-polymerized, and made sustainable [2]. The main effects of a plasticizer on the properties of a polymeric material are: (i) Decrease in the glass transition temperature (Tg), (ii) decrease in the melting temperature (Tm), (iii) decrease in the tensile strength, (iv) increase in the elongation at break, and (v) reduction in viscosity [6]. These changes affect the workability of the materials, because the decrease in Tm can allow reducing the temperature of processing, and possible polymer degradation

Objectives

Methods

Results