Improving Thermal Conductivity Coefficient in Oriented Strand Lumber (OSL) Using Sepiolite.

Hamid R Taghiyari,Abolfazl Soltani,Hamed Gholipour,Ayoub Esmailpour,Antonios N Papadopoulos,Vahid Hassani

doi:10.3390/nano10040599

Hamid R Taghiyari, Abolfazl Soltani + Show 4 more

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https://doi.org/10.3390/nano10040599

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Abstract

An issue in engineered wood products, like oriented strand lumber (OSL), is the low thermal conductivity coefficient of raw material, preventing the fast transfer of heat into the core of composite mats. The aim of this paper is to investigate the effect of sepiolite at nanoscale with aspect ratio of 1:15, in mixture with urea-formaldehyde resin (UF), and its effect on thermal conductivity coefficient of the final panel. Sepiolite was mixed with UF resin for 20 min prior to being sprayed onto wood strips in a rotary drum. Ten percent of sepiolite was mixed with the resin, based on the dry weight of UF resin. OSL panels with two resin contents, namely 8% and 10%, were manufactured. Temperature was measured at the core section of the mat at 5-second intervals, using a digital thermometer. The thermal conductivity coefficient of OSL specimens was calculated based on Fourier’s Law for heat conduction. With regard to the fact that an improved thermal conductivity would ultimately be translated into a more effective polymerization of the resin, hardness of the panel was measured, at different depths of penetration of the Janka ball, to find out how the improved conductivity affected the hardness of the produced composite panels. The measurement of core temperature in OSL panels revealed that sepiolite-treated panels with 10% resin content had a higher core temperature in comparison to the ones containing 8% resin. Furthermore, it was revealed that the addition of sepiolite increased thermal conductivity in OSL panels made with 8% and 10% resin contents, by 36% and 40%, respectively. The addition of sepiolite significantly increased hardness values in all penetration depths. Hardness increased as sepiolite content increased. Considering the fact that the amount of sepiolite content was very low, and therefore it could not physically impact hardness increase, the significant increase in hardness values was attributed to the improvement in the thermal conductivity of panels and subsequent, more complete, curing of resin.

Highlights

Oriented strand lumber (OSL) is a widely studied engineered wood to satisfy the demand for structural wood products [1,2,3]
The present project was primarily carried out to examine the potential impact of sepiolite at nanoscale on the thermal conductivity coefficient of oriented strand lumber (OSL) panels
Sepiolite was mixed with urea-formaldehyde resin (UF) resin for 20 min prior to being sprayed onto wood strips in a rotary drum

Summary

Introduction

Oriented strand lumber (OSL) is a widely studied engineered wood to satisfy the demand for structural wood products [1,2,3]. One constant problem in engineered wood and wood-composite manufacturing factories is the low thermal conductivity coefficient of wood, preventing the fast transfer of heat into the core of composite mats [6,7,8]. Nanowollastonite was applied with urea formaldehyde resin, which improved the thermal conductivity coefficient and, the mechanical and physical properties of OSL [12]. The mechanism involved in the fortification of UF resin with nanowollastonite was attributed mainly to the following: (i) nanowollastonite compounds made active bonds with the cellulose hydroxyl groups, putting them out of reach for the water molecules to make bonds with and (ii) the high thermal conductivity coefficient of wollastonite improved the transfer of heat to different layers of the OSL mat, facilitating better and more complete resin curing

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