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Tuning the long-term properties to control biodegradation by surface modifications of agricultural fibres in biocomposites
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
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.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:11
Keyword [en]
agricultural fibres, biocomposites, renewable polymers, PP, PLA, PHBV, surface modifications, water uptake, microbial growth, biodegradation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-119915ISBN: 978-91-7501-677-1 (print)OAI: oai:DiVA.org:kth-119915DiVA: diva2:612793
Public defence
2013-04-22, Q2, Osquldasväg 10 NB, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130325

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2013-03-26Bibliographically approved
List of papers
1. The effect of surface modifications on the mechanical and thermal properties of empty fruit bunch oil palm fibre PP biocomposites
Open this publication in new window or tab >>The effect of surface modifications on the mechanical and thermal properties of empty fruit bunch oil palm fibre PP biocomposites
2012 (English)In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 3, no 3, 79-100 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to study the effect of chemical surface modifications on empty fruit bunch oil palm fibre/polypropylene composite properties. By FTIR spectra, propionylated fibre and PPgMA-modified fibre showed the presence of a carbonyl group of esters while vinyltrimethoxysilane-treated fibre showed a peak of silicate, confirming that the modifications were successful. PPgMAmodified fibre PP composite at fibre content 20% demonstrated the highest modulus of 0.71 GPa while the modulus of unmodified fibre PP composite was 0.56 GPa. By DSC analysis, PPgMA-modified fibre and vinyltrimethoxysilane-treated fibre PP composite at the same fibre content of 5% showed the highest crystallinity of 46% and 44% respectively whereas unmodified fibre PP composite showed a lower crystallinity of 38%. The DMTA analysis showed that after 60°C, the modified fibre PP composites exhibited a higher stiffness than pure polypropylene.

Keyword
Biocomposite, Empty fruit bunch oil palm fibre, Mechanical properties, Polypropylene, Surface modification, Thermal properties
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-110207 (URN)2-s2.0-84869800540 (Scopus ID)
Note

QC 20130111

Available from: 2013-01-11 Created: 2013-01-10 Last updated: 2013-03-25Bibliographically approved
2. Comparison of Water Uptake as Function of Surface Modification of Empty Fruit Bunch Oil Palm Fibres in PP Biocomposites
Open this publication in new window or tab >>Comparison of Water Uptake as Function of Surface Modification of Empty Fruit Bunch Oil Palm Fibres in PP Biocomposites
2013 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, 2998-3016 p.Article in journal (Refereed) Published
Abstract [en]

Empty fruit bunch oil palm (EFBOP) fibres were surface modified by four different methods, propionylation, vinyltrimethoxy silanization, PPgMA dissolution modification, and PPgMA blending, and integrated into a polypropylene (PP) matrix. The designed biocomposites were subjected to an absorption process at different temperatures. Their water uptake behaviour was compared with the unmodified fibre biocomposites. An increased fibre content and temperature resulted in increased water uptake for all of the biocomposites. The biocomposites containing modified fibres showed a reduction in water uptake, rate of diffusion, sorption, and permeation in comparison with unmodified fibre composites. Comparing the 20 wt% fibre composites at ambient temperature, the performance in water absorption followed the sequence silanization < propionylation < PPgMA dissolution modification < PPgMA blending < no modification. Furthermore, the lowest water absorption was obtained from the silanized fibre/PP composite with 40% fibre content at ambient temperature. Dissolution or blending of PPgMA gave similar water uptake results. The reduction of diffusion, sorption, and permeation confirmed that the modification of fibres was potentially effective at resisting water penetration into the composites.

Keyword
Biocomposite, Fibre modification, Oil palm fibre, Polypropylene, Water
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-119924 (URN)000320185500073 ()2-s2.0-84877933255 (Scopus ID)
Note

QC 20130625

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2017-12-06Bibliographically approved
3. Water absorption and hydrothermal performance of PHBV/sisal biocomposites
Open this publication in new window or tab >>Water absorption and hydrothermal performance of PHBV/sisal biocomposites
Show others...
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.

Keyword
Hydrothermal degradation, Biocomposites, Poly(hydroxybutyrate-co-valerate) (PHBV), Lignocellulosic fibres, Sisal, Statistical factorial analysis (SFA)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-119928 (URN)10.1016/j.polymdegradstab.2014.04.012 (DOI)000343380800020 ()2-s2.0-84956613223 (Scopus ID)
Note

QC 20141121. Updated from manuscript to article in journal.

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2017-12-06Bibliographically approved
4. Susceptibility to biodegradation by fungi for sisal/PLA and sisal/PHBV biocomposites
Open this publication in new window or tab >>Susceptibility to biodegradation by fungi for sisal/PLA and sisal/PHBV biocomposites
2013 (English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-119926 (URN)
Note

QS 2013

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2013-03-25Bibliographically approved
5. Effect of surface modifications on microbial growth and biodegradation in sisal/PLA biocomposites
Open this publication in new window or tab >>Effect of surface modifications on microbial growth and biodegradation in sisal/PLA biocomposites
2013 (English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-119927 (URN)
Note

QS 2013

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

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