Abstract
As a byproduct from the soybean oil industry, soy meal can be reproduced into value-added products to replace formaldehyde as a plywood adhesive. However, the use of soy meal has been limited by its poor antifungal and antiseptic properties. In this work, three kinds of material, namely nano-Ag/TiO2, zinc pyrithione, and 4-cumylphenol were applied to enhance the mildew resistance of soy meal via breakdown of the cellular structure of mildew. The fungi and mold resistance, morphology, thermal properties, and mechanism of the modified soy meal were evaluated. The success of the antifungal and antiseptic properties was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The results indicated that all three kinds of material improved the fungi and mold resistance of soy meal, and sample B, which was modified with a compound of nano-Ag/TiO2 and zinc pyrithione, was the effective antifungal raw material for the soy-based adhesives. FTIR indicated that the great improvement of antifungal properties of soy meal modified with 4-cumylphenol might be caused by the reaction between COO– groups of soy protein. This research can help understand the effects of the chemical modification of nano-Ag/TiO2, zinc pyrithione, and 4-cumylphenol on soy meal, and the modified soy meal exhibits potential for utilization in the plywood adhesive industry.
Highlights
Formaldehyde-based adhesives have predominated in the plywood industry market due to their advantage with regard to cost and availability, and most of them use petrochemicals as raw material [1,2]
The growing awareness of the need for formaldehyde-free environmental protection has motivated an intense effort to develop eco-friendly materials. Renewable biomaterials such as proteins [4,5,6], carbohydrates [7,8,9], tannins [10,11], and citric acid [12,13] have been extensively studied for the replacement of petroleum-based wood adhesives
Off-white colonies were first detected on the untreated soy meal (SM) rather than on the preservative-treated ones, which suggested that the untreated SM is more vulnerable to microbial attack than the preserved ones
Summary
Formaldehyde-based adhesives have predominated in the plywood industry market due to their advantage with regard to cost and availability, and most of them use petrochemicals as raw material [1,2]. Such extensive usage of petroleum, a nonrenewable resource, triggers the environmental problem of volatile organic compound release and causes human health problems [3]. The deficiency in fungi and mold resistance, the low Polymers 2020, 12, 169; doi:10.3390/polym12010169 www.mdpi.com/journal/polymers
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