Minimization of moisture content in cellulose fibres through a physico-chemical treatment: application in polymer composites

S. Cichosz, A. Masek
Lodz University of Technology,
Poland

Keywords: cellulose fibres, solvent exchange, ethylene-norbornene copolymer, moisture content

Summary:

Plant and animal fibres used as plastic reinforcements have been known for many years. Due to the low-cost and low-density, as well as good mechanical properties and recyclability of different natural fibres an opportunity to use them as alternatives to synthetic fillers (e.g. glass, carbon) in polymer composite applications is given. Biodegradable plastics and bio-inspired polymer products based on annually renewable agricultural and biomass feedstock can form the basis for a portfolio of sustainable, eco-efficient products that can compete and capture markets currently dominated by products based exclusively on petroleum feedstock. Therefore, it is extremely important to improve the processing of such materials. One of the main problems is the cohesion of the polar filler to the hydrophobic polymer matrix. In the following research new cellulose hybrid modification approach, being undoubtedly a scientific novelty, is introduced. It is combined of physical and chemical methods. Study reveals the properties of cellulose (Arbocel UFC100 – Ultra Fine Cellulose) and characterizes cellulose-filled polymer composites based on an ethylene-norbornene copolymer (TOPAS Elastomer E-140). This research underlines the importance of UFC100 moisture content reduction considering polymer composites application with the employment of a technique different than thermal treating. Therefore, a new hybrid chemical modification approach is introduced. It consists of two steps: solvent exchange (with ethanol either hexane) and maleic anhydride (MA) grafting. With the use of Fourier-transform infrared spectroscopy (FT-IR), it has been proved that the employment of different solvents may contribute to the higher yield of the modification process. Furthermore, according to the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the improvement in fibres thermal resistance has been noticed. Modification process, apart from leading to the water removal from the bio-filler, may bring about a specific variation in the cellulose chemical structure. It is being referred in literature as a hornification process and concerns the stiffening of cellulose-based materials. The phenomenon occurs when the biopolymer is being dried, especially while wetting-drying cycles are repeated many times. In its origin, it has been commonly associated with the creation of irreversible hydrogen bonds either lacton bridges creation. This research provides a reader with a wide range of data considering the properties of both cellulose and polymer composite regarding different biofiller moisture content (controlled via a drying time). Regarding mechanical properties of a polymer composite sample, it may be claimed that the most favourable changes were evidenced in case of filling TOPAS with UFC100 specimen which has been modified with MA after a solvent exchange with ethanol (not dried before the treatment). Mentioned sample exhibited an excellent performance (almost the same as neat polymer matrix – tensile strength at the level of approximately 40 MPa, elongation at break in the region of 500%) which was not affected by the high aspect ratio filler alignment direction. What should be emphasized, plant fibre modification described in this research was highly successful and might contribute to the production of environmentally friendly polymer materials, leading to plastic-waste minimization and environmental pollution limitation, subsequently, following the rules of sustainable development.