Study of an Appropriate Suberinic Acids Binder for Manufacturing of Plywood

Abstract

In the study, birch outer bark`s suberinic acids (SA), appropriate for binding the plywood, obtained in a water medium and precipitated in two acidification stages under various medium pH levels, were characterized, which could become a sustainable, environmentally friendly alternative to toxic, formaldehyde-containing plywood binders. In the process of obtaining SA, it was found that all SA of the first acidification stage filtrated successfully. With increasing the pH level of precipitation from 2 to 6, the yield of SA decreased from 35.6 to 18.8 wt% from oven dry (o.d.) extracted birch outer bark or 69.5-36.6 wt% from total o.d. raw material SA. Meanwhile, only one sample of SA from the second acidification stage with the initial pH level 6 filtrated successfully, reaching the yield of 4.4 wt% from total o.d. raw material SA. The SA obtained in the first acidification stage at the pH level 2 contained a lower amount of epoxy groups – 1.7 wt% from o.d. SA, but at the same time, the highest acid value – 84.4 mg KOH/g. In turn, increasing the pH level to 6, the amount of epoxy groups increased gradually up to 19.9 wt% from o.d. SA, and the acid value of SA decreased to 67.4 mg KOH/g. The acid value of SA from the second acidification stage was 133.0 mg KOH/g, but epoxy groups in the composition were not observed.