Thermal and Mechanical Properties of Esterified Lignin in Various Polymer Blends.

Alexander Orebom,Davide Di Francesco,Clara Pierrou,Joseph S M Samec,Patrick Shakari

doi:10.3390/molecules26113219

Alexander Orebom, Davide Di Francesco + Show 3 more

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https://doi.org/10.3390/molecules26113219

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Abstract

Lignin is an abundant polymeric renewable material and thus a promising candidate for incorporation in various commercial thermoplastic polymers. One challenge is to increase the dispersibility of amphiphilic lignin in lipophilic thermoplastic polymers We altered Kraft lignin using widely available and renewable fatty acids, such as oleic acid, yielding more than 8 kg of lignin ester as a light brown powder. SEC showed a molecular weight of 5.8 kDa with a PDI = 3.80, while the Tg of the lignin ester was concluded to 70 °C. Furthermore, the lignin ester was incorporated (20%) into PLA, HDPE, and PP to establish the thermal and mechanical behavior of the blends. DSC and rheological measurements suggest that the lignin ester blends consist of a phase-separated system. The results demonstrate how esterification of lignin allows dispersion in all the evaluated thermoplastic polymers maintaining, to a large extent, the tensile properties of the original material. The impact strength of HDPE and PLA blends show substantial loss upon the addition of the lignin ester. Reconverting the acetic acid side stream into acetic anhydride and reusing the catalyst, the presented methodology can be scaled up to produce a lignin-based substitute to fossil materials.

Highlights

Plastics are fundamental building blocks of numerous commercial material segments today, with a total production volume of about 359 million tons annually in 2018 [1].Fossil plastics are strongly linked to environmental issues such as CO2 emissions and littering resulting in a widespread leakage of microplastics in the environment
The annual production capacity of bioplastics is less than 1% of the total plastic production volume, [3] which further emphasize the need for innovations to address the demand of renewable materials for fossil plastic substitution [4,5]
Previously reported procedures to yield Fatty Acid Ester of Lignin (FAEL) involve the formation of acyl chlorides in situ [27,28], with the subsequent requirement of reagents and generation of a large amount of waste and the requirement of additional chemicals to quench the acids generated during the process lowering the atom economy dramatically

Summary

Introduction

Plastics are fundamental building blocks of numerous commercial material segments today, with a total production volume of about 359 million tons annually in 2018 [1].Fossil plastics are strongly linked to environmental issues such as CO2 emissions and littering resulting in a widespread leakage of microplastics in the environment. Plastics are fundamental building blocks of numerous commercial material segments today, with a total production volume of about 359 million tons annually in 2018 [1]. With an increasing global population, the need for plastic components is expected to increase while the environmental concerns create a demand for technological development of renewable solutions [2]. The annual production capacity of bioplastics is less than 1% of the total plastic production volume, [3] which further emphasize the need for innovations to address the demand of renewable materials for fossil plastic substitution [4,5]. Kraft lignin is the main component in black liquor which is a waste product from the production of cellulose pulp. Removal of lignin from this system has been shown to be economically favorable due to the possibility to increase the productivity of the pulp mill without investment in new CAPEX intensive recovery boilers [7,8,9]

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