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Surface-Densified Wood: From Laboratory-Scale Research Towards a Competitive Product
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

For many decades, humans have been consuming more resources than the world has to offer in the long run. Increasing the use of renewable materials, such as wood, is essential if we are to achieve a sustainable use of the resources available to us. Densification of wood in general, and surface densification in particular, has the potential to improve the properties of widely available low-density wood species, opening up new fields of application, and fostering the use of wood products in general.

The objective of this thesis is to put past research within the field of surface densification of solid wood and advancements within the present project into a context, and to suggest a path towards a performance-driven and cost-effective type of product. A prevalent research gap has been identified and this thesis summarizes how this gap can be filled by already conducted and future studies. Important aspects that need be handled in order to fulfill the overall vision of the large-scale commercialization of surface-densified wood products are considered.

Past studies were successful in gaining a good understanding of different approaches to the densification of solid wood, such as using a hot press or a friction welding machine. Problems, such as the moisture-induced recovery of the densified wood cells could be solved from a technological perspective. However, those studies did not take into account industrial implementation. Existing methods are time- and/or energy-consuming. The use of roller-pressing equipment showed promising results, but also highlighted certain limitations. Solid wooden boards have been successfully surface-densified at speeds of up to 80 m/min. However, problems arose regarding the plasticization and stabilization of the densified wood cells, indicating that a continuous belt-press approach might be more viable with regard to the objective of industrial implementation.

In parallel, a structured method to identify the most suitable wood species for surface densification has been presented, with the aim of propagating the use of surface-densified wood products and widening their fields of application. This method has confirmed the suitability of previously used wood species, and has also suggested alternatives not considered thus far.

Previous studies into the surface densification of wood have provided a rather sound understanding of the densification process and have provided a useful foundation for the current project. The work done, thus far, has shown the viability of a continuous densification process and has indicated a sensible path towards the widespread establishment of surface-densified wood products on the market. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2016. , 60 p.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Other Natural Sciences
Research subject
Wood Science and Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-60282ISBN: 978-91-7583-757-4ISBN: 978-91-7583-758-1 (pdf)OAI: oai:DiVA.org:ltu-60282DiVA: diva2:1045759
Presentation
2016-12-15, Hörsal A, Hus A, Luleå tekniska universitet, Skellefteå, 10:00 (English)
Supervisors
Available from: 2016-11-14 Created: 2016-11-10 Last updated: 2016-11-25Bibliographically approved
List of papers
1. Development of a continuous wood surface densification process: the roller pressing technique
Open this publication in new window or tab >>Development of a continuous wood surface densification process: the roller pressing technique
2016 (English)In: Proceedings of the 59th International Convention of Society of Wood Science and Technology.: Forest Resource and Products: Moving Toward a Sustainable Future. / [ed] Susan LeVan-Green, Monona, WI: Society of Wood Science and Technology , 2016, 17-24 p.Conference paper (Refereed)
Place, publisher, year, edition, pages
Monona, WI: Society of Wood Science and Technology, 2016
Keyword
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
Research subject
Wood Technology
Identifiers
urn:nbn:se:ltu:diva-30743 (URN)4a861bab-bce6-4ee8-8387-7f46dd34cced (Local ID)978-0-9817876-6-4 (PDF) (ISBN)4a861bab-bce6-4ee8-8387-7f46dd34cced (Archive number)4a861bab-bce6-4ee8-8387-7f46dd34cced (OAI)
Conference
International Convention of Society of Wood Science and Technology : Forest Resource and Products: Moving Toward a Sustainable Future 06/03/2016 - 10/03/2016
Note
Godkänd; 2016; 20160309 (dicsan)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2016-11-10Bibliographically approved
2. Continuous Wood Surface Densification: Chemical Treatments to Reduce the Set-Recovery
Open this publication in new window or tab >>Continuous Wood Surface Densification: Chemical Treatments to Reduce the Set-Recovery
Show others...
2016 (English)In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium - Bio-based composites for a sustainable future, Concepción: University of Concepción , 2016, 66-77 p.Conference paper (Refereed)
Abstract [en]

The hardness of the outer surface of solid wood can be improved by densification, and this opens up new fields of application for low-density species. So far, surface densification is carried out in time- and energy-consuming batch processes, and this means that potential advantages over more expensive hardwood species or non- renewable materials are lost. One of the crucial problems in all densification processes is to reduce the moisture-induced set-recovery of the densified wood cells. In a previous study, a new high-speed continuous surface densification process was introduced, where the surface of solid Scots pine boards could be densified at speeds of up to 80 m/min by a roller pressing technique. The aim of the present study was to integrate the roller pressing technique with different pre- and post-treatment methods to reduce the set- recovery. An aqueous solution of sodium hydroxide was used as a pre-treatment agent to activate the wood surface prior to densification, and a methacrylate ester monomer solution was used as an impregnation agent, both before and after densification. After densification and impregnation, the methacrylate monomers are polymerized by curing in an oven at 100°C in order to stabilize the compressed wood cells. The results show that the different treatments had no significant effect on the set-recovery, probably due to insufficient penetration into the wood material. Future work will focus on improving the treatment process and integrating all process steps into a fully continuous and automatic process. 

Place, publisher, year, edition, pages
Concepción: University of Concepción, 2016
Keyword
compression, sodium hydroxide, methacrylate, impregnation, roller pressing
National Category
Other Natural Sciences Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60281 (URN)
Conference
13th Pacific Rim Bio-Based Composites Symposium, Concepción, Chile, 13-15 November 2016
Available from: 2016-11-10 Created: 2016-11-10 Last updated: 2016-11-30Bibliographically approved
3. A new methodology to select hardwood species for wooden products
Open this publication in new window or tab >>A new methodology to select hardwood species for wooden products
2015 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 4, 344-352 p.Article in journal (Refereed) Published
Abstract [en]

In general, only a few wooden species are used or even considered for any given wooden product, even though hundreds of alternative wood species are available. In many cases, the reason for this is tradition rather than availability, technical or aesthetic considerations and it can result in endangered species being used to an unnecessarily high degree. The purpose of this study was to develop a structured, quantifiable, and easy-to-use methodology to identify suitable hardwood species for a specific product. The methodology combines processes based on quality function deployment and multivariate data analysis in a three-step workflow, and takes different criteria into consideration. To verify the methodology, it was applied to an example product: an electric guitar. It was shown that the methodology was easy to use and provided useful and quantifiable results. Expansion of the underlying wood species data-set will be necessary to improve the performance in the future.

Keyword
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
Research subject
Wood Technology
Identifiers
urn:nbn:se:ltu:diva-15634 (URN)10.1080/17480272.2015.1046919 (DOI)f2b8de43-9f83-42c7-acfd-472616b0e91e (Local ID)f2b8de43-9f83-42c7-acfd-472616b0e91e (Archive number)f2b8de43-9f83-42c7-acfd-472616b0e91e (OAI)
Note
Validerad; 2015; Nivå 1; 20150614 (dicsan)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2016-11-10Bibliographically approved
4. Application of a new method to select the most suitable wood species for surface densification.
Open this publication in new window or tab >>Application of a new method to select the most suitable wood species for surface densification.
2016 (English)In: New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA, Madison: Forest Products Society, 2016Conference paper (Refereed)
Abstract [en]

Surface densification improves many properties of solid wood, and opens up new applications for low-density species e.g. flooring or wooden structures, and adds value to these species. Research into the surface densification of wood has been focused mainly on Scots pine, Norway spruce, aspen and poplar. In order to propagate the use of surface densification techniques, it is necessary to find more wood species that have a particularly high potential for an increase in value through such a treatment.The purpose of this study was to select wood species which are suitable for surface densification and for use in a specific product, by applying a systematic and quantifiable selection method. The method that was presented in detail in an earlier work, is designed around a workflow consisting of multiple stages, takes into account weighted selection criteria and provides a quantified ranking of the most suitable species.The results suggest that several species such as alder, basswood, cedar, and obeche that have not previously been considered for surface densification may be suitable candidates. Aspen, poplar and pine were confirmed as suitable, being among the top species in the ranking.

Place, publisher, year, edition, pages
Madison: Forest Products Society, 2016
Keyword
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
Research subject
Wood Technology
Identifiers
urn:nbn:se:ltu:diva-40694 (URN)feba3b52-2111-4497-a812-5b7ae64e89a1 (Local ID)feba3b52-2111-4497-a812-5b7ae64e89a1 (Archive number)feba3b52-2111-4497-a812-5b7ae64e89a1 (OAI)
Conference
Forest Products Society International Convention : 26/06/2016 - 29/06/2016
Note
Godkänd; 2016; 20160712 (dicsan)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2016-11-10Bibliographically approved

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