Melt-processing and properties of thermoplastic composites based on ethylene-acrylic acid copolymer reinforced with wood nanocellulose
Doktorsavhandling, 2020

Composites reinforced with cellulose nanofibers (CNF), both modified and unmodified cellulose nanocrystals (CNC) and pulp fibers have been prepared through small-scale and large-scale methods. The composites were produced by water-assisted dispersion mixing, drying and compression moulding on the laboratory scale and by extrusion and injection moulding for the large-scale production. The compression-moulded composites were stiffer and stronger by a factor of more than 10 for the CNF or pulp-based samples (>50 wt%) and by a factor of 3 for the CNC-based composites (at 10 wt%). The addition of a lubricant to pulp-based fibers resulted in a behaviour similar to that of a compatibilizer at low concentrations and to that of both compatibilizer and lubricant at higher concentrations.

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.

Injection moulding

Cellulose nanofibers

Melt rheology

Cellulose nanocrystals

Mechanical properties


Pulp fibers



Virtual Development Laboratory, Chalmers Tvärgata 4C, Chalmers University of Technology, Gothenburg
Opponent: Professor Mikael Hedenqvist, Kungl. Tekniska Högskolan (KTH), Stockholm, Sweden


Abhijit Venkatesh

Chalmers, Industri- och materialvetenskap, Konstruktionsmaterial

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Ehsan Hosseini, A. Venkatesh, A. Boldizar & G. Westman. Molybdenum disulphide – A traditional external lubricant that shows interesting interphase improvements in pulp based biocomposites

The societal efforts to move towards a more sustainable future has resulted in the search for bio-based, biodegradable and renewable replacements among which cellulose is also being explored as a possible option. The main source of cellulose are plants and trees, with a global annual synthesis of 100 billion tons, and hence abundantly available in nature. Cellulosic materials are also biodegradable, renewable, inexpensive and have been used as structural material for centuries while still covering a large part of the industries like paper, forest products, textiles, etc. Sweden has always used cellulose as raw materials in various applications and with the stricter regulations from EU, the industries are opting for more sustainable materials/solutions. This has worked in the favour of wood-based materials which can be used as an inexpensive reinforcing material in thermoplastic composites.

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.

Tillverkning av nya högpresterande CNF biocompositer

Stiftelsen för Strategisk forskning (SSF) (GMT14-0036), 2020-01-01 -- 2020-12-31.

Stiftelsen för Strategisk forskning (SSF) (GMT14-0036), 2016-01-01 -- 2020-12-31.


Hållbar utveckling







Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4888



Virtual Development Laboratory, Chalmers Tvärgata 4C, Chalmers University of Technology, Gothenburg


Opponent: Professor Mikael Hedenqvist, Kungl. Tekniska Högskolan (KTH), Stockholm, Sweden

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