Melt-processing and properties of thermoplastic composites based on ethylene-acrylic acid copolymer reinforced with wood nanocellulose
Doctoral thesis, 2020
However, when the processing was scaled up, the improvement in properties was much less for the CNF-based and CNC-based composites after being melt-processed via extrusion and injection moulding, despite the fact that they showed a percolated cellulose network. Although the scale-up was successful, aggregates were observed. These aggregates could be reduced to some extent by changing the process design and parameters. Water-assisted extrusion was also used to reduce the aggregation but there was little improvement in properties. It is suggested that the extent of melt flow in the processing method influences the final properties of the composites, despite the nanoscale reinforcement.
Pulp fibers
Melt rheology
Composite
Injection moulding
Cellulose
Cellulose nanofibers
Cellulose nanocrystals
Extrusion
Mechanical properties
Author
Abhijit Venkatesh
Chalmers, Industrial and Materials Science, Engineering Materials
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A composite material contains two (matrix and reinforcement) or more (additives) components that are combined to obtain a material with properties different than the individual components. Wood is nature’s composite where lignin is the matrix and cellulose are the reinforcement. The reinforcement provides structural integrity and improves the properties, which is exactly what cellulose does in trees and plants. In wood-polymer composites, the cellulose has been used as reinforcement, for decades, to strengthen the polymer matrix. However, an interest has been rekindled due to advancements in cellulose production technology which helps in commercially obtaining nano-sized cellulose reinforcements. Here, the nanocellulose is expected to improve the reinforcing capabilities more than the larger fibers, due to their excellent mechanical properties, resulting in composites with high strength and stiffness.
Despite the favourable properties of nanocellulose, it has a major drawback when used as reinforcement in thermoplastics, due to its relatively hydrophilic nature when compared to the usually hydrophobic polymer matrix, which drastically affect the properties. In addition, the main method of producing nanocellulose composites has been through laboratory scale methods and to make the production of nanocellulose composites commercially interesting on an industrial scale, the feasibility with conventional melt processing technique should be considered. The results from this work helps us improve the understanding of melt processing of cellulose nanocomposites and highlight the importance of process details. It also highlights the possibility of upscaling the production while analysing its impact on nanocellulose modification and the different types of melt processing techniques. In this work, depending on the type of processing method and the hierarchical structure of the cellulose reinforcements used, the composites exhibited an increase in stiffness of up to 21 times than that of the polymer matrix.
Production of new high-performance CNF biocomposites (Cellulose nano-composites)
Swedish Foundation for Strategic Research (SSF) (GMT14-0036), 2020-01-01 -- 2020-12-31.
Swedish Foundation for Strategic Research (SSF) (GMT14-0036), 2016-01-01 -- 2020-12-31.
Subject Categories
Polymer Chemistry
Materials Engineering
Polymer Technologies
Composite Science and Engineering
Driving Forces
Sustainable development
Areas of Advance
Materials Science
ISBN
978-91-7905-421-2
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4888
Publisher
Chalmers
Virtual Development Laboratory, Chalmers Tvärgata 4C, Chalmers University of Technology, Gothenburg
Opponent: Professor Mikael Hedenqvist, Kungl. Tekniska Högskolan (KTH), Stockholm, Sweden