State of Degradation in Archeological Oak from the 17th Century <i>Vasa</i> Ship: Substantial Strength Loss Correlates with Reduction in (Holo)Cellulose Molecular Weight

Bjurhager, Ingela; Halonen, Helena; Lindfors, Eva-Lisa; Iversen, Tommy; Almkvist, Gunnar; Gamstedt, E. Kristofer; Berglund, Lars A.

doi:10.1021/bm3007456

Cited by 65 publications

(51 citation statements)

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“…Compared with the reference specimens, the tensile strength of Vasa oak was reduced by an average of 40%, but reductions of up to 80% were also observed [25]. From this summary, it can be concluded that the variation in mechanical properties is large in the oak in the Vasa warship.…”

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 72%

“…At that time, no differences in mechanical performance were found between samples taken from the interior and the exterior part of the warship [24]. Chemical degradation with a subsequent reduction in strength has been confirmed later on [25]. However, as the majority of the chemical degradation is also believed to have taken place after the salvage [31], Thunell's results [24] are reasonable.…”

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 98%

“…Bjurhager et al [25] also carried out extensive tensile testing in the longitudinal direction on Vasa oak from four different locations in the warship. Compared with the reference specimens, the tensile strength of Vasa oak was reduced by an average of 40%, but reductions of up to 80% were also observed [25].…”

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 99%

“…The density of both Vasa oak and reference oak will be measured from volume-weight measurements and compared with X-ray measurements. The PEG content can be determined using methods such as Soxhlet extraction, nuclear magnetic resonance spectroscopy (NMR) or matrix-assisted laser desorption/ ionisation time-of-flight (MALDI-TOF) mass spectrometry [3,25,37].…”

Section: Relationship Between Density Moe and Peg Distributionmentioning

confidence: 99%

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Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

2013

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To maintain the integrity of the Vasa warship after salvage in 1961, conservation treatment with polyethylene glycol was carried out to prevent the collapse of cell walls. This treatment had negative effects on the strength and stiffness of the oak and the hull structure has been found to slowly deform over time. It is of interest to construct a three-dimensional numerical computer model to model and predict the deformation of the warship. This creates difficulties related to the complexity of measuring the detailed material properties that are required as input. In this context, a non-destructive methodology to predict the stiffness of the Vasa oak in terms of moduli of elasticity in the three principal directions of timber at critical positions in the ship would be useful. The twofold aim of the paper is to propose a strategy for a support system and to conduct an on-site assessment of the warship to predict the mechanical properties of the Vasa oak material. This paper also contains an up-to-date review of all essential mechanical data measured on the Vasa oak. The preliminary investigation using an X-ray technique to investigate the density properties produced promising results for future use in the evaluation of the mechanical performance. Based on these results, a procedure to establish the stiffness properties of the Vasa oak in terms of MOE was suggested, using a combination of data from previous measurements, in combination with extended tests on Vasa oak specimens and an X-ray-based density calibration procedure. The general complexity of the Vasa warship can be mainly attributed to large variations in the properties of Vasa oak due to surface degradation, chemical treatment and the disintegration of the cell-wall structure originating from centuries of waterlogged conditions. That causes difficulties when assessing mechanical and physical properties on a structural level. A combination of visual inspection together with X-ray investigation is of great importance to evaluate those properties and to obtain more accurate estimates. The results from evaluating mechanical properties can serve as input in a numerical model and serve as a foundation for decision-making relating to the modification of the support system.

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Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 72%

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 98%

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 99%

Section: Relationship Between Density Moe and Peg Distributionmentioning

confidence: 99%

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Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

2013

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“…This procedure aimed at replacing the water in the wood cell walls by PEG and thus preventing shrinkage and formation of cracks during drying (Håfors 2001). Since salt precipitation on numerous surfaces on the ship had been reported (Sandström et al 2002), a series of investigations of the chemistry (Glastrup et al 2006;Almkvist and Persson 2008a, b;Lindfors et al 2008;Almkvist et al 2016) and also of the mechanical properties of Vasa oak wood (Ljungdahl 2006;Bjurhager et al 2012;Vorobyev et al 2016) have been performed over the last years. These research activities showed that the oak wood is affected by degradation, i.e., by depolymerization of polysaccharides.…”

Section: Introductionmentioning

confidence: 99%

The influence of chemical degradation and polyethylene glycol on moisture-dependent cell wall properties of archeological wooden objects: a case study of the Vasa shipwreck

et al. 2016

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Cell wall measures allow for direct assessment of wood modification without the adverse effect of varying density and microstructure. In this study, cell wall properties of recent and archeological oak wood from the Vasa shipwreck were investigated for cell wall stiffness, hardness and creep with respect to effects of chemical degradation, impregnation with a preservation agent, namely polyethylene glycol, and moisture. For this purpose, nanoindentation tests were performed at varying relative humidity, leading to different moisture contents in the wood samples. Concurrently, microstructural and chemical characterization of the material was conducted. Impregnated and untreated recent oak wood showed a softening effect of both moisture and preservation agent at the wood cell wall level. On the contrary, increased stiffness was found for non-impregnated Vasa oak, which can be explained by aging-related modifications in cell wall components. These effects were counteracted by the softening effect of polyethylene glycol in the impregnated Vasa material, where a lower overall stiffness was measured. The reverse effect of the preservation agent and moisture, namely increased indentation creep of the cell wall material, was revealed. The loss of acetyl groups in the hemicelluloses explained the decreased hygroscopicity of the Vasa oak. In the impregnated Vasa oak, this effect seemed to be partly counteracted by the presence of low-molecular polyethylene glycol contributing to higher hygroscopicity of the cell wall. Thus, the higher overall sorptive capacity of the impregnated Vasa material, with respect to the non-impregnated material, was detected, which has resulted in a sorptive behavior similar to that of recent oak wood. The proposed approach requires only small amounts of material, making it especially suitable for application to precious historical wooden artifacts.

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Lectin‐Functionalized Polyethylene Glycol for Relief of Mucosal Dryness

Blakeley

Sharma

Kaper

et al. 2021

Adv Healthcare Materials

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The importance of lubrication between oral surfaces provided by the salivary film is most acutely apparent when it is disrupted, a prevalent consequence of salivary gland hypofunction experienced with aging, a symptom of certain diseases, or a side effect of some medical interventions. Sufferers report difficulty with speech and oral food processing and collectively is detrimental to quality of life. Polyethylene glycol (PEG) is widely employed as a successful biocompatible boundary lubricant in engineering and biomedical applications. It is hypothesized that the immobilization of PEG to biological materials such as oral epithelial cells and tissue can mimic the salivary film and provide durable relief from the symptoms of mucosal dryness. To do so, PEG is functionalized with a sugar binding lectin (wheat germ agglutinin) to enhance epithelial adhesion through lectin-sugar interactions. Retention and lubricity are characterized on an ex vivo oral tissue tribology rig. WGA-PEG coats and retains on mucin films, oral epithelial cells, and porcine tongue tissue, and offers sustained reduction in coefficient of friction (COF). WGA-PEG could be developed into a useful topical treatment for reducing oral friction and the perception of dry mouth.

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State of Degradation in Archeological Oak from the 17th Century Vasa Ship: Substantial Strength Loss Correlates with Reduction in (Holo)Cellulose Molecular Weight

Cited by 65 publications

References 20 publications

Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

The influence of chemical degradation and polyethylene glycol on moisture-dependent cell wall properties of archeological wooden objects: a case study of the Vasa shipwreck

Lectin‐Functionalized Polyethylene Glycol for Relief of Mucosal Dryness

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