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Open AccessArticle

A New Flexible Soy-Based Adhesive Enhanced with Neopentyl Glycol Diglycidyl Ether: Properties and Application

1
Ministry of Education Key Laboratory of Wooden Material Science and Application, Beijing Key Laboratory of Wood Science and Engineering, College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China
2
School of Materials Science and Engineering, Shandong University, Jinan 250061, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Antonio Pizzi
Polymers 2016, 8(9), 346; https://doi.org/10.3390/polym8090346
Received: 19 June 2016 / Revised: 10 August 2016 / Accepted: 14 September 2016 / Published: 21 September 2016
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
Soy-based adhesives inherently possess low water resistance and brittleness, which limit their application on plywood fabrication. This investigation involves using a long chain cross-linker, neopentyl glycol diglycidyl ether (NGDE), to produce an intrinsic toughening effect to reduce the brittleness and improve the water resistance of a soybean meal–based adhesive. The solids content, viscosity, functional groups, fracture surface micrographs, and thermal stability of the adhesives were measured. Three-layer plywood was fabricated using the resultant adhesive, and the tensile shear strength of the plywood was measured. All adhesive properties were compared with a soybean meal/polyamidoamine-epichlorohydrin (PAE) adhesive and commercial melamine urea formaldehyde resin. The results showed that adding 6 g NGDE improved the water resistance of the soybean meal-based adhesive by 12.5%. This improvement is attributed to the following reasons: (1) a dense cross-linked network is formed by the chemical reaction between NGDE and protein molecules; (2) the toughness of the adhesive increases and a smooth and homogeneous fracture surface is created, which effectively prevents moisture intrusion; (3) the addition of NGDE increases the thermostability of the cured adhesive. The tensile shear strength of the plywood bonded with the soybean meal-based adhesive with 6 g NGDE was 286.2% higher than that without NGDE and attained 1.12 MPa, which was attributed to the reduction in the adhesive’s viscosity, and the improvement in the water resistance and toughness of the adhesive. The tensile shear strength of the plywood bonded with 6 g NGDE was 19.1% higher than that with 6 g PAE and was similar to the MUF resin, which validated the novel adhesive being suitable for use as an industrial plywood adhesive. View Full-Text
Keywords: soy-based adhesive; neopentyl glycol diglycidyl ether; water resistance; toughness; plywood soy-based adhesive; neopentyl glycol diglycidyl ether; water resistance; toughness; plywood
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MDPI and ACS Style

Luo, J.; Luo, J.; Zhang, J.; Bai, Y.; Gao, Q.; Li, J.; Li, L. A New Flexible Soy-Based Adhesive Enhanced with Neopentyl Glycol Diglycidyl Ether: Properties and Application. Polymers 2016, 8, 346.

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