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Water absorption and hydrothermal performance of PHBV/sisal biocomposites
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-2139-7460
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2014 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, 166-174 p.Article in journal (Refereed) Published
Abstract [en]

The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.

Place, publisher, year, edition, pages
2014. Vol. 108, 166-174 p.
Keyword [en]
Hydrothermal degradation, Biocomposites, Poly(hydroxybutyrate-co-valerate) (PHBV), Lignocellulosic fibres, Sisal, Statistical factorial analysis (SFA)
National Category
Polymer Technologies
URN: urn:nbn:se:kth:diva-119928DOI: 10.1016/j.polymdegradstab.2014.04.012ISI: 000343380800020ScopusID: 2-s2.0-84956613223OAI: diva2:612898

QC 20141121. Updated from manuscript to article in journal.

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2014-11-21Bibliographically approved
In thesis
1. Tuning the long-term properties to control biodegradation by surface modifications of agricultural fibres in biocomposites
Open this publication in new window or tab >>Tuning the long-term properties to control biodegradation by surface modifications of agricultural fibres in biocomposites
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sustainable polymeric materials put emphasis on mastering the whole life-cycle of polymeric materials. This includes the choice of raw materials, selection of synthesis and processing, environmental impact during long-term use followed by detailed knowledge about recycling and waste management.  Within this large efforts are put in the design and development of new biocomposites using renewable fibres instead of inert ones. The thesis deals with surface modifications of agricultural fibres and the design of biocomposites with optimal long-term properties balancing the potential risk for biodegradation. 

The first part of this thesis involved surface modifications of oil palm fibres and production of biocomposites with PP as matrix. The chemical surface modifications of oil palm fibres explored propionylation, PPgMA grafting via solution modification and reactive blending and vinyltrimethoxy silanization as methods. All modified fibre/PP biocomposites showed improvements in the mechanical properties followed also by an improvement of water resistance. In comparison with unmodificed fibres/PP matrix the highest water resistance after the surface modifications of oil palm fibres were observed for silanization followed by PPgMA modified,  PPgMA blending and  propionylation.

The second part aimed at producing fully biodegradable biocomposites and analysing the resulting properties with respect to potential risk for biodegradation. Sisal fibres were incorporated in PLA and PHBV and the resulting risk for biodegradation using a fungus, Aspergillus niger, monitored. Neat PLA and PHBV were compared with the corresponding biocomposites and already without fibres both polymers were notably biodegraded by Aspergillus niger. The degree of biodegradation of PLA and PHBV matrices was related to the extent of the growth on the material surfaces. Adding sisal fibres gave a substantial increase in the growth on the surfaces of the biocomposites.

Correlating the type of surface modification of sisal fibres with degree of biodegradation, it was demonstrated that all chemically modified sisal/PLA biocomposites were less biodegraded than unmodified sisal biocomposites.  Propionylated sisal/PLA demonstrated the best resistance to biodegradation of all biocomposites while sisal/CA/PLA demonstrated high level of biodegradation after severe invasion by Aspergillus niger.

In general, the biodegradation correlated strongly with the degree of water absorption and surface modifications that increase the hydrophobicity is a route to improve the resistance to biodegradation.

Designing new biocomposites using renewable fibres and non-renewable and renewable matrices involve the balancing of the increase in mechanical properties, after improved adhesion between fibres and the polymer matrix, with the potential risk for biodegradation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xi, 76 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2013:11
agricultural fibres, biocomposites, renewable polymers, PP, PLA, PHBV, surface modifications, water uptake, microbial growth, biodegradation
National Category
Engineering and Technology
urn:nbn:se:kth:diva-119915 (URN)978-91-7501-677-1 (ISBN)
Public defence
2013-04-22, Q2, Osquldasväg 10 NB, KTH, Stockholm, 10:00 (English)

QC 20130325

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2013-03-26Bibliographically approved

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