Surface densification of acetylated wood

Laine, Kristiina; Segerholm, Kristoffer; Wålinder, Magnus; Rautkari, Lauri; Hughes, Mark; Lankveld, Chiel

doi:10.1007/s00107-016-1077-3

Cited by 21 publications

(11 citation statements)

References 23 publications

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“…On the other hand, the reduced penetration may have a negative impact on mechanical adhesion. The compressibility of acetylated wood is affected by the decreasing material moisture [ 81 ]. After acetylation, 20 mm-thick (radial) pine ( Pinus radiata D. Don) samples were densified by only 6.9%, compared to 10% for untreated samples.…”

Section: Bonding Acetylated Woodmentioning

confidence: 99%

Bonding Acetylated Veneer for Engineered Wood Products—A Review

2022

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The purpose of this review is to put previous research findings on acetylated wood and the fabrication of veneer-based products in a common context. The first research on wood acetylation was already conducted in the 1920s using wood meal, whereas relevant research on veneer acetylation was published nearly two decades later, during the 1940s. In the years that followed, a great deal of research has been done on both solid wood and composite acetylation. Developments in the 1990s and early 2000s resulted in the creation of commercial products. Nowadays, wood is becoming increasingly popular in construction. Therefore, high-performance materials with high dimensional stability and durability are required. Veneers are thereby of particular relevance because of their propensity to absorb chemicals into even tough-to-treat wood species. However, acetylation alters the bonding properties of wood, which is important for the manufacture of engineered veneer products, especially in load-bearing construction. A large amount of research is now being conducted on the acetylation of veneer, and acetylated veneer products are anticipated in the near future. This study covers the fundamentals of bonding but focuses specifically on veneer acetylation and its fabrication to engineered veneer-based products. The influencing factors of acetylation on bonding are also discussed.

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Section: Bonding Acetylated Woodmentioning

confidence: 99%

Bonding Acetylated Veneer for Engineered Wood Products—A Review

2022

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“…Laine et al (2013b) achieved similar results for surface densified Scots pine at the same treatment temperature. Acetylating wood before densification resulted in a reduction of the set-recovery from 70 to 20% (Laine et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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

Neyses¹,

Rautkari²,

Yamamoto³

et al. 2017

iForest

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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.

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“…Their tests showed that the post-treatment at higher temperatures and longer durations improved the dimensional stability of the HTM samples, suggesting a permanent fixation of the transversal compression, but also reduced the thermal stability in the same context. Laine et al (2016b) carried out the surface densification test of acetylated radiata pine and mainly focused on the set recovery and hardness improvement of the densified acetylated wood. According to their work, the pre-acetylation significantly reduced the set recovery, and the hardness and the hardness recovery of the acetylated samples increased significantly due to densification.…”

Section: Introductionmentioning

confidence: 99%

Transversal mechanical properties of surface-densified and hydrothermally modified needle fir wood

Zhan

Avramidis

2017

Wood Sci Technol

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Hydrothermal-mechanical (HTM) treatment is a combined action of temperature, moisture, and mechanical loads. Various kinds of HTM processes have been developed to produce eco-friendly modified wood products. Among these modification technologies, a combination of surface densification and hydrothermal post-treatment is a promising option that can be used to enhance plantation wood properties and generate value-added softwood products. This paper aimed to investigate the transversal dynamic transversal modulus of elasticity (dtMOE) profile and transversal density profile of surface-densified and hydrothermally posttreated needle fir (Abies nephrolepis) wood, and provide a practical guide for the processing optimization of surface-densified and thermally treated low-grade plantation softwood. Needle fir lumbers were surface-densified in an open hotpressing system, at a compression ratio of 16.1% and two hot-pressing temperatures (160 and 180°C) for a pressure holding duration of 10 min with a subsequent hydrothermal post-treatment at two temperatures (180 and 200°C) for 60 min. The transversal dtMOE profiles for six types of specimens (moisture-saturated, conditioned control, and four types of surface-densified specimens) were measured and analyzed by a dynamic thermo-mechanical analysis (DMA) apparatus. A dtMOE gradient variable (G M ) was defined herein to quantitatively formulate the dtMOE distribution of the surface-densified and hydrothermally post-treated wood specimens. Upon hot pressing, compressed cell tissues were observed within a 1.0-to 2.0-mm layer beneath the surface of the densified wood. The density peaks of compressed sections were increased to 650-800 kg/m 3 , compared with the average & Jian-feng Zhan density of the control specimens being at 350 kg/m 3 . The dtMOEs of the compressed sections were increased from 650 MPa of the control specimens, to 750-900 MPa, achieving the objective of surface densification. As the temperature of hydrothermal post-treatment increased from 180 to 200°C, the differences of the dtMOEs between the compressed surface sections and their inner adjacent ones decreased significantly, indicating the effective fixation of the compression deformations. Based on the test results obtained herein, it was concluded that the impact of the hot-pressing temperature and thermal post-treatment temperature over the dtMOE was insignificant. Nevertheless, it was also found that the hydrothermal treatment temperature showed significant influences over the dtMOE difference between the densified surface and its adjacent layer; the possible explanations for these complicated behaviors were also proposed herein.

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Surface densification of acetylated wood

Cited by 21 publications

References 23 publications

Bonding Acetylated Veneer for Engineered Wood Products—A Review

Bonding Acetylated Veneer for Engineered Wood Products—A Review

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

Transversal mechanical properties of surface-densified and hydrothermally modified needle fir wood

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