Preparation and Characterisation of Binder-Free All-Cellulose Composites
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A recent emerging concept of all-cellulose composites within the field of
environmentally friendly materials has received increasing attention. The main
advantage of these materials is the lack of using additional bonding agents such as
polymer resins as in the case of e.g. phenolic resin based panel products or natural
fibre reinforced plastics that increase their environmental impact. Two different
routes for the production of all-cellulose composites have been followed. The
obtained materials were characterised by scanning electron microscopy, X-ray
diffraction, flexure and tensile mechanical tests, thermogravimetric analysis,
pycnometry and water absorption tests.
The first strategy makes use of the selective dissolution method where the
cellulose fibre skins are partially dissolved to form a matrix phase that bonds the
fibres together, while the strong core fibres are maintained and impart a reinforcing
effect to the composites. The influence of the dissolution time, activation time and
the fibre source were assessed. It was found that a dissolution time of 18 h led to
materials with the best overall mechanical performance (5.5 GPa and 145 MPa for
Young’s modulus and tensile strength, respectively), as this time allowed for the
dissolution of a sufficient amount of fibre surface to obtain good interfacial bonding
between fibres, while keeping a considerable amount of remaining fibre cores that
provide a strong reinforcement to the composite, leading to materials that outperform
natural fibres reinforced polypropylene composites.
Still, the previous methodology has the drawback of using chemical
substances of high environmental impact (solvents). In order to overcome this, a new
concept in the production of all-cellulose composites is proposed in this work, which
makes use of the intrinsic bonding capability between cellulose fibres to enhance the
hydrogen bond network in order to produce materials of good mechanical
performance. A new experimental procedure was developed, based on the refinement
Abstract
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of cellulose fibres in order to increase their specific surface area, thus increasing the
interfibre bonding capability, and achieving materials with excellent mechanical
properties, up to 17 GPa and 119 MPa for flexural modulus and strength,
respectively, and low water absorption. These new high-performing environmentally
friendly materials are based on renewable resources and are 100% recyclable and
biodegradable.
Authors
Peces, Raquel ArévaloCollections
- Theoretical Physics [234]