Abstract
In this study, for the first time, Brazil nut seed oil was chemically modified with maleic anhydride to obtain maleinized Brazil nut seed oil (MBNO). The same process was developed to obtain maleinized hemp seed oil (MHO). The use of MBNO and MHO was studied as bio-based plasticizers by incorporating them with different contents ranging from 0 to 10 phr in a polylactic acid (PLA) matrix. By means of mechanical, thermal and thermomechanical characterization techniques, the properties of the different formulations were studied to evaluate the plasticizing effect of the MBNO and MHO. With the addition of both plasticizers, a significant increase in ductile properties was observed, reaching an increase in elongation at break of 643% with 7.5 phr MBNO and 771% with 10 phr MHO compared to neat PLA. In addition, it has been observed that the mechanical resistant properties do not decrease, since the oils enhance the crystallization of PLA by increasing the free volume between its chains and counteracting the effect. Finally, a disintegration test was carried out under thermophilic conditions at 58 °C for 27 days, demonstrating that the incorporation of MHO and MBNO does not significantly affect the biodegradability of neat PLA.
Highlights
Since the end of the 20th century, environmental concerns and the development of sustainable strategies have been on the rise [1]
The problem arises mainly because of the negative impact on the ecosystems generated by the amount of plastic waste, since only 173 million tonnes are collected for recycling or landfill [3], and by the exploitation of non-renewable natural resources, such as petroleum
Several polylactic acid (PLA) compositions were made with different phr of maleinized Brazil nut seed oil (MBNO) and maleinized hemp seed oil (MHO), which are summarized in Table 1, where the codes assigned to each of them are indicated
Summary
Since the end of the 20th century, environmental concerns and the development of sustainable strategies have been on the rise [1]. The lack of miscibility between the components makes it difficult to achieve this improvement in toughness [5,11,17,18] For this reason, some authors proposed modified vegetable oils (MVOs) as compatibilizing agents or even as plasticizing additives [12,19]. Maleinization is a chemical process, usually carried out in a single step, which consists of incorporating maleic anhydride molecules into the triglycerides that make up vegetable oils when conjugated carbon–carbon double bonds are present For this purpose, there are several methods that can be used, such as the so-called “ene” reaction, Diels-Alder addition and free radical copolymerization, the first being the most favorable and the one used in this work [5,29]. Where c is the exact concentration of the KOH standard solution used (mol·L−1), V the volume of the KOH standard solution used (mL) and m the mass analyzed (g)
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