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Neyses, B. (2019). Surface Densification of Solid Wood: Paving the Way Towards Industrial Implementation. (Doctoral dissertation). Luleå University of Technology
Open this publication in new window or tab >>Surface Densification of Solid Wood: Paving the Way Towards Industrial Implementation
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surface densification of a piece of solid wood results in an increase in density and in hardness in the whole or a part of the densified material, and is one of the ways of improving the properties and value of low-density wood species. Despite efforts for many years, mass commercialisation of either bulk- or surface-densified wood products has not yet been achieved. Most of the previously tested densification methods have limitations in terms of processing speed and integration into the largely continuous wood processing chain, which leads to high production costs. Established methods to eliminate the set-recovery rely either on technologically complex close-system methods or on open-system methods that require relatively long periods of high energy input. For this reason, impregnation with adhesives is used in almost all commercially available densified wood products, and none of them have risen above their status of being niche products.

Based on this background, three objectives for this project were formulated: (1) the development of a method for selecting the most suitable wood species for surface densification, (2) showing that surface densification can be carried out in a continuous manner at high process speeds, (3) and researching a fast open-system method to reduce the set- recovery.

The method developed for selecting the most suitable wood species for surface densification was based on Lean principles, and it confirmed the suitability of previously studied wood species, such as Scots pine, spruce and poplar. In addition, several suitable alternatives from different parts of the world and from different types of forest were identified. This suggests a high potential for establishing such wood products on a global market level.

Two studies using a continuous roller press showed that solid wood can be successfully surface-densified at process speeds of up to 80 m min-1, and that some defects, such as knots, are acceptable in the raw material, but the problem of set-recovery could not however be solved.

A screening experiment testing different open-system approaches to reduce the set-recovery highlighted the potential of a novel method using ionic liquids as a plasticiser prior to the surface densification of solid Scots pine. The set-recovery could be reduced to 10%, with the time of high energy input being less than 10 minutes. The Brinell hardness was increased by a factor of 2.7 over that of undensified wood. A study with thermo-gravimetric analysis and digital image correlation showed that the set-recovery almost exclusively happens in the transition zone between the densified and undensified wood cells, where there is less penetration of the ionic liquids.

The work accomplished in this project has successfully addressed several gaps in the field of wood densification, firstly, by employing a continuous surface densification process using a roller press, and secondly, by developing and studying a fast open-system pre-treatment with ionic liquids, which greatly reduces the set-recovery. Research will continue on a new band press, facilitating a swift transfer of knowledge between small- scale studies and the continuous surface densification of production-size wooden boards.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019. p. 123
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-75794 (URN)978-91-7790-435-9 (ISBN)978-91-7790-436-6 (ISBN)
Public defence
2019-10-08, Auditorium A, Skellefteå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-09-02 Created: 2019-09-02 Last updated: 2019-09-12Bibliographically approved
Báder, M., Bak, M., Németh, R., Rademacher, P., Rousek, R., Horníček, S., . . . Pfriem, A. (2018). Wood densification processing for newly engineered materials. In: M. C. Barbu; A. Petutschnigg; E. M. Tudor (Ed.), Proceedings of the 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), Freising/Münich, September 20-21: . Paper presented at 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), 20 - 21 September 2018, Freising/Munich, Germany. (pp. 255-263). Kuchl
Open this publication in new window or tab >>Wood densification processing for newly engineered materials
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2018 (English)In: Proceedings of the 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), Freising/Münich, September 20-21 / [ed] M. C. Barbu; A. Petutschnigg; E. M. Tudor, Kuchl, 2018, p. 255-263Conference paper, Published paper (Refereed)
Abstract [en]

Wood is a renewable, bio-based material with a mixture of different properties and qualities, used in numerous applications. Beside many species with high wood qualities several species suffer due to a number of disadvantages, where low hardness and abrasive resistance are characteristic for low-density species. This paper presents examples of on-going European research projects and industrial processes mostly related to wood densification methods. Wood densification is a classical thermohydro-mechanical (THM) wood treatment process, through which density is increased by mechanical compression of wood perpendicular to the grain, by impregnation of cell lumens or cell walls with solutions or melted substances (resins, waxes), or by a combination of both. The purpose is to produce newly designed and engineered materials and products with new property profiles, which would potentially find new markets. In general, the THM processes consist of three stages: plasticization of the wood cells, followed by the actualcompression, and finally solidification of the compressed wood in order to prevent elastic spring-back and the moisture-induced set-recovery. The wood densification process refers but is not limited to solid wood and might apply to whole wood pieces, or to local areas within given pieces only. Another THM method is the mechanical compression of wood parallel to the grain, which leads to a product with high flexibility. A European wood research network, represented by the authors of this contribution, has extended experience in many wood modification processes, as demonstrated through ongoing researches and case studies in this paper

Place, publisher, year, edition, pages
Kuchl: , 2018
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71358 (URN)
Conference
5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), 20 - 21 September 2018, Freising/Munich, Germany.
Available from: 2018-10-27 Created: 2018-10-27 Last updated: 2019-01-21Bibliographically approved
Neyses, B. & Sandberg, D. (2017). Ionic liquid pre-treatment to reduce the elastic spring-back and set-recovery of surface densified Scots pine.. In: Tondi, G, Posavčevič, M, Kutnar, A, Wimmer, R, (Ed.), COST Action FP1407 3rd Conference: Wood modification research & applications. Paper presented at COST Action FP1407 3rd Conference, Kuchl, Austria, September 14-15 (pp. 32-33). Kuchl, Austria
Open this publication in new window or tab >>Ionic liquid pre-treatment to reduce the elastic spring-back and set-recovery of surface densified Scots pine.
2017 (English)In: COST Action FP1407 3rd Conference: Wood modification research & applications / [ed] Tondi, G, Posavčevič, M, Kutnar, A, Wimmer, R,, Kuchl, Austria, 2017, p. 32-33Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Kuchl, Austria: , 2017
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-65756 (URN)978-3-200-05255-0 (ISBN)978-3-200-05265-9 (ISBN)
Conference
COST Action FP1407 3rd Conference, Kuchl, Austria, September 14-15
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2017-11-24Bibliographically approved
Neyses, B., Rautkari, L., Yamamoto, A. & Sandberg, D. (2017). Pre-treatment with sodium silicate, sodium hydroxide, ionic liquids or methacrylate resin to reduce the set-recovery and increase the hardness of surface-densified Scots pine. iForest : Biogeosciences and Forestry, 10(5), 857-864
Open this publication in new window or tab >>Pre-treatment with sodium silicate, sodium hydroxide, ionic liquids or methacrylate resin to reduce the set-recovery and increase the hardness of surface-densified Scots pine
2017 (English)In: iForest : Biogeosciences and Forestry, ISSN 1971-7458, E-ISSN 1971-7458, Vol. 10, no 5, p. 857-864Article in journal (Refereed) Published
Abstract [en]

The hardness of the outer regions of solid wood can be improved by surface densification, and this opens up new fields of application for low-density species. So far, surface densification relies on time- and energy-consuming batch processes, and this means that the potential advantages over more expensive hardwood species or non-renewable materials are reduced. Using fossil-based plastics or applying wood densification processes with a high energy consumption has adverse effects on the environment. In a previous study, it was shown that the surface of wood can be densified by a continuous high-speed process, adopting a roller pressing approach. The desired density profiles could be obtained at process speeds of up to 80 m min-1, but an equally simple and fast method to eliminate the moisture-induced set-recovery of the densified wood cells is still required. For this reason, the goal of the present study was to evaluate the effect on the set-recovery and hardness of surface-densified Scots pine after a fast pre-treatment with solutions of sodium silicate, sodium hydroxide, methacrylate resin, and ionic liquids. The Scots pine specimens were pre-treated by applying the chemical treatment and impregnation agents to the wood surface with a paper towel, before the specimens were densified. For each type of treatment, 15 specimens were densified in a hot press. The set-recovery was measured after two wet-dry cycles, and 30 Brinell hardness measurements were carried out on each group of specimens. In general, the effect of the treatments on the set-recovery was rather low. Ionic liquid solutions appear to work as a strong plasticiser and the treatment led to a reduction in set-recovery by 25%. The treatments with sodium silicate, ionic liquids and methacrylate resin led to a greater hardness than in untreated and densified specimens. Further experiments are needed to improve the depth of penetration of the treatment solutions into the wood surface, as this was identified as one of the main causes of the rather weak effects.

Place, publisher, year, edition, pages
Italian Society of Silviculture and Forest Ecology, 2017
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-66300 (URN)10.3832/ifor2385-010 (DOI)000413842100004 ()2-s2.0-85039747852 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-10-31 (rokbeg)

Available from: 2017-10-29 Created: 2017-10-29 Last updated: 2019-09-12Bibliographically approved
Neyses, B. & Sandberg, D. (2016). A new method to select wood species suitable for surface densification. In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium : Bio-based composites for a sustainable future.. Paper presented at 13th Pacific Rim Bio-Based Composites Symposium, Conceptión, Chile, 13-15 November 2016 (pp. 96). Concepción: University of Concepción, Article ID PT04.
Open this publication in new window or tab >>A new method to select wood species suitable for surface densification
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, p. 96-, article id PT04Conference paper, Poster (with or without abstract) (Refereed)
Place, publisher, year, edition, pages
Concepción: University of Concepción, 2016
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60704 (URN)
Conference
13th Pacific Rim Bio-Based Composites Symposium, Conceptión, Chile, 13-15 November 2016
Available from: 2016-11-27 Created: 2016-11-27 Last updated: 2017-11-24Bibliographically approved
Neyses, B. & Sandberg, D. (2016). Application of a new method to select the most suitable wood species for surface densification (ed.). In: (Ed.), New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA. Paper presented at Forest Products Society International Convention : 26/06/2016 - 29/06/2016. Madison: Forest Products Society
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, Published 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
Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
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: 2019-09-12Bibliographically approved
Neyses, B., Hagman, O., Nilsson, A., Sandberg, D. & Sundqvist, B. (2016). Continuous Wood Surface Densification: Chemical Treatments to Reduce the Set-Recovery. In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium - Bio-based composites for a sustainable future. Paper presented at 13th Pacific Rim Bio-Based Composites Symposium, Concepción, Chile, 13-15 November 2016 (pp. 66-77). Concepción: University of Concepción
Open this publication in new window or tab >>Continuous Wood Surface Densification: Chemical Treatments to Reduce the Set-Recovery
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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, p. 66-77Conference paper, Published 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
Keywords
compression, sodium hydroxide, methacrylate, impregnation, roller pressing
National Category
Other Mechanical Engineering
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: 2019-09-12Bibliographically approved
Neyses, B., Hagman, O., Sandberg, D. & Nilsson, A. (2016). Development of a continuous wood surface densification process: the roller pressing technique (ed.). In: (Ed.), Susan LeVan-Green (Ed.), Proceedings of the 59th International Convention of Society of Wood Science and Technology.: Forest Resource and Products: Moving Toward a Sustainable Future.. Paper presented at International Convention of Society of Wood Science and Technology : Forest Resource and Products: Moving Toward a Sustainable Future 06/03/2016 - 10/03/2016 (pp. 17-24). Monona, WI: Society of Wood Science and Technology
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, p. 17-24Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Monona, WI: Society of Wood Science and Technology, 2016
Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-30743 (URN)4a861bab-bce6-4ee8-8387-7f46dd34cced (Local ID)978-0-9817876-6-4 (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: 2019-09-12Bibliographically approved
Couceiro, J., Neyses, B. & Sandberg, D. (2016). In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning. In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium, Bio-based composites for a sustainable future.. Paper presented at 13th Pacific Rim Bio-Based Composites Symposium, Conceptión, Chile, 13-15 November 2016 (pp. 92). Concepción: University of Concepción, 2, Article ID NA01.
Open this publication in new window or tab >>In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning
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, Vol. 2, p. 92-, article id NA01Conference paper, Poster (with or without abstract) (Refereed)
Place, publisher, year, edition, pages
Concepción: University of Concepción, 2016
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60703 (URN)
Conference
13th Pacific Rim Bio-Based Composites Symposium, Conceptión, Chile, 13-15 November 2016
Available from: 2016-11-27 Created: 2016-11-27 Last updated: 2017-11-24Bibliographically approved
Neyses, B., Rautkari, L., Yamamoto, A. & Sandberg, D. (2016). Reduction of the set-recovery of surface-densified Scots pine by pre-treatment with sodium silicate or sodium hydroxide. In: Kutnar A., Schwarzkopf M., Burnard M., Sebera V. & Troppová E. (Ed.), Innovative production technologies and increased wood products recycling and reuse: . Paper presented at COST Action FP1407 2nd Conference, Innovative production technologies and increased wood products recycling and reuse,Brno, Czech Republic, 29-30th of September, 2016 (pp. 57-58). Brno: Mendel University in Brno
Open this publication in new window or tab >>Reduction of the set-recovery of surface-densified Scots pine by pre-treatment with sodium silicate or sodium hydroxide
2016 (English)In: Innovative production technologies and increased wood products recycling and reuse / [ed] Kutnar A., Schwarzkopf M., Burnard M., Sebera V. & Troppová E., Brno: Mendel University in Brno , 2016, p. 57-58Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
Brno: Mendel University in Brno, 2016
Keywords
water glass, compression, wood modification, surface treatment
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60293 (URN)978-80-7509-429-2 (ISBN)
Conference
COST Action FP1407 2nd Conference, Innovative production technologies and increased wood products recycling and reuse,Brno, Czech Republic, 29-30th of September, 2016
Available from: 2016-11-10 Created: 2016-11-10 Last updated: 2017-11-24Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1489-0839

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