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Research Papers

Epoxy Adhesives Modified With Nano- and Microparticles for In Situ Timber Bonding: Effect of Environment on Mechanical Properties and Moisture Uptake

[+] Author and Article Information
Z. Ahmad

Faculty of Civil Engineering, University Technology Mara Malaysia, Shah Alam, Selangor 40450, Malaysiazakiahah@hotmail.com

M. P. Ansell

Department of Mechanical Engineering, Materials Research Centre, University of Bath, Avon BA2 7AY, UKm.p.ansell@bath.ac.uk

D. Smedley

 Rotafix (Northern) Limited, Rotafix House, Abercraf, Swansea SA9 1UR, UKdaverotafix@aol.com

J. Eng. Mater. Technol 132(3), 031016 (Jun 24, 2010) (8 pages) doi:10.1115/1.4001836 History: Received December 12, 2009; Revised May 05, 2010; Published June 24, 2010; Online June 24, 2010

The environmental stability of three room temperature cure epoxy adhesives was evaluated following exposure to temperatures of 20°C, 30°C, and 50°C at 95%RH, to 50°C in air and soaked in water for up to 90 days. The adhesives contained nano- and microparticles and were especially formulated for bonded-in timber connections, and the properties of bulk adhesives and adhesively bonded block shear specimens were evaluated. After 90 days of aging the results demonstrate critical temperature effects controlled by the glass transition temperature. The apparent free volume for all the adhesives remains constant as moisture is absorbed but plasticization takes place at high temperature and relative humidity, evidenced by the increased elongation and yield observed by strain values and scanning electron microscope. Exposure at 50°C in air causes the adhesives to postcure enhancing strength but high humidity causes degradation. Nanofiller additions enhance environmental stability but the addition of microparticles provides better moisture resistance.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 4

Moisture absorption curves for adhesives, (a) aged at 50°C/95%RH and (b) soaked in water at 20°C

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Figure 5

Tensile strength of adhesives exposed to 95%RH at 20°C, 30°C, and 50°C for 90 days in comparison with control samples

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Figure 6

Modulus of elasticity of adhesives exposed to 95%RH at 20°C, 30°C, and 50°C for 90 days in comparison with control samples

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Figure 11

Shear strength of adhesive-timber joints exposed to 95%RH at temperatures of 20°C, 30°C, and 50°C for 90 days referenced to solid LVL and standard block shear specimens held at 20°C and 65%RH.

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Figure 1

(a) Tensile strength, (b) modulus of elasticity, and (c) elongation as a function of aging time for adhesives aged at 50°C and 95% RH

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Figure 2

(a) Tensile strength, (b) modulus of elasticity, and (c) elongation as a function of aging time for adhesives aged at 50°C in air

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Figure 3

(a) Tensile strength, (b) modulus of elasticity, and (c) elongation as a function of aging time for adhesives soaked in water

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Figure 7

SEM micrograph of fracture surfaces of Timberset: (a) exposed to 20°C/95%RH, showing the plasticization of the adhesive, ×1200; (b) exposed to 30°C/95%RH, showing the debonding of fillers, ×400; and (c) exposed to 50°C/95%RH, showing the adhesive is packed and dense, ×1400

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Figure 8

The moisture induced swelling versus maximum moisture uptake for the three adhesives (correlation coefficient in parentheses): (a) CB10TSS, (R2=0.60), (b) Albipox, (R2=0.95) (c) Timberset, (R2=0.86), and (d) all three adhesives

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Figure 9

SEM micrographs of fracture surface of Albipox: (a) aged at 20°C/95%RH, ×1500; (b) aged at 30°C/95%RH, ×6500; and (c) aged at 50°C/95%RH, ×7500, all for 90 days

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Figure 10

Shear strength from block shear test for the three adhesives at different aging times at 50°C/95%RH

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