Tailoring of oxidized starch's adhesion using crosslinker and adhesion promotor for the recycling of fiberboards

Abstract

The growing interest in recycling waste medium density fiberboards (MDFs) is driving the development of new adhesives that provide sufficient adhesion, and allow disintegration of the waste MDFs. Described in here is the preparation of adhesives based on oxidized starch (OS) in combination with blocked‐polymeric 4‐4 diphenylmethane diisocyanate (B‐pMDI) as a crosslinker and poly(vinyl alcohol) (PVA) as an adhesion promotor for the recycling of waste MDFs. The COOH groups of OS were reacted with NCO groups of B‐pMDI to form amide linkages, and the CHO groups were reacted with OH groups of PVA through hydrogen bonding. Further, when applied as an adhesive, the OS formed ester linkages with OH of MDF fibers. As the results, MDF bonded with 1% B‐pMDI/15% PVA/OS adhesive had an internal bonding strength of 0.13 MPa, 0.01 mg L−1 of formaldehyde emission (FE), and 12% of degree of fiber disintegration. These results demonstrate that the B‐pMDI/PVA/OS adhesive is a possible alternative to the current urea–formaldehyde resins for the recycling of waste MDFs into recycled MDFs without FE. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47966.

Tuning of adhesion and disintegration of oxidized starch adhesives for the recycling of medium density fiberboard

“…Regardless of the type of cross-linker, weight gain values decreased as the content of crosslinker increased. Furthermore, the OS-bonded MDFs showed greater weight gain than did the UF-bonded MDFs, showing that the C=O or O-H of the OS-bonded MDFs absorbed more water than those of the UF-bonded MDFs (Guo and Wu 2017;Lubis et al 2019). The test results for mass loss and degree of fiber disintegration followed the same trend as that of weight gain (Fig.…”

“…4), and thus the -CHO groups were easily extracted by hydrolysis. However, there was a possibility that the peaks of the C=O of ester linkages and -CHO groups of the CA/OS overlapped at 1720 cm -1 because the -COOH of the OS could react with the -OH of the MDF fibers to form ester linkages (Umemura and Kawai 2015;Lubis et al 2019). The -COOH groups showed a peak at 1600 cm -1 only after hydrolysis at 80 °C for 1 h. Additional peaks at 1660 cm -1 for B-pMDI/OS and 1645 cm -1 for CA/OS were attributed to intra-molecular hydrogen bonds of ester or amide bonds in the hydrolysates (Parovuori et al 1995).…”

Ferric Ions Modified Polyvinyl Alcohol for Enhanced Molecular Structure and Mechanical Performance

“…To increase the bonding strength, PVA is usually used with other resins. For instance, PVA is widely used as a filler in formaldehyde-based and starch-based adhesives for the increase of their solid content and viscosity [11][12][13]. It is sometimes used as an emulsifier in isocyanate adhesives for even distribution or shelf time elongation purposes [14].…”