Functional MgO-Lignin Hybrids and Their Application as Fillers for Polypropylene Composites.

Aleksandra Grząbka-Zasadzińska,Sławomir Borysiak,Łukasz Klapiszewski,Teofil Jesionowski

doi:10.3390/molecules25040864

Aleksandra Grząbka-Zasadzińska, Sławomir Borysiak + Show 2 more

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https://doi.org/10.3390/molecules25040864

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Abstract

Inorganic–organic hybrids are a group of materials that have recently become the subject of intense scientific research. They exhibit some of the specific properties of both highly durable inorganic materials (e.g., titanium dioxide, zinc) and organic products with divergent physicochemical traits (e.g., lignin, chitin). This combination results in improved physicochemical, thermal or mechanical properties. Hybrids with defined characteristics can be used as fillers for polymer composites. In this study, three types of filler with different MgO/lignin ratio were used as fillers for polypropylene (PP). The effectiveness of MgO-lignin binding was confirmed using Fourier transform infrared spectroscopy. The fillers were also tested in terms of thermal stability, dispersive-morphological properties as well as porous structure. Polymer composites containing 3 wt.% of each filler were subjected to wide angle X-ray diffraction tests, differential scanning calorimetry and microscopic studies to define their structure, morphology and thermal properties. Additionally, tensile tests of the composites were performed. It was established that the composition of the filler has a significant influence on the crystallization of polypropylene—either spherulites or transcrystalline layers were formed. The value of Young’s modulus and tensile strength remained unaffected by filler type. However, composites with hybrid fillers exhibited lower elongation at break than unfilled polypropylene.

Highlights

Biodegradable materials/biomaterials, hybrid materials or composites/biocomposites obtained from renewable sources are extremely promising products that may replace synthetic polymers in the future [1]
The selection of this biopolymer is mainly dictated by its structural diversity as well as ease of preparation, which results from the production associated with cellulose fibers [9]
In the case of all hybrid systems, characteristic signals originating from functional groups present in lignin were observed: stretching vibrations of O–H bonds in the wavenumbers range of 3600–3200 cm−1, stretching vibrations of C–H bonds, including those derived from -CH3, -CH2 and O–CH3 groups, with wavenumber values of 2950–2840 cm−1, vibrations associated with the presence of aromatic rings in the biopolymer structure, in the wavenumber range of 1600–1500 cm−1 and 1490–1440 cm−1

Summary

Introduction

Biodegradable materials/biomaterials, hybrid materials or composites/biocomposites obtained from renewable sources (biomass) are extremely promising products that may replace synthetic polymers in the future [1]. Lignin is the second most available substance on Earth after cellulose [8] This biopolymer is distinguished from other products by properties such as biodegradability, antioxidant and antibacterial activity [10,11], good chemical reactivity [12], affinity to inorganic oxides [13,14] or possible sorption of harmful compounds from the environment due to the diversity of functional groups in the lignin structure [15,16]. It is worth emphasizing that lignin is a renewable raw material, i.e., it corresponds well

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