Properties of crosslinked waterborne polyurethane adhesives with modified melamine: Effect of curing time, temperature, and HMMM content

Abstract

A series of crosslinked waterborne polyurethane (WBPU) adhesives were prepared by prepolymer synthesis. Modified melamine, hexamethoxymethyl melamine (HMMM) was used as the crosslinking agent. It was elucidated by FTIR and 1 H-NMR spectroscopy that the crosslinking reaction occurred between the polyurethane carboxyl acid salt groups and the HMMM methoxy groups. The hydrophobicity of the WBPU films increased after HMMM crosslinking. As the HMMM content was increased (increasing mole ratio of HMMM/dimethylol propionic acid (DMPA)), the water uptake (%) of the film decreased, and the water contact angle increased. The thermal stability, tensile strength, and initial modulus increased with increasing HMMM content up to an optimum value (mole ratio of HMMM/DMPA=0.5) at which point the maximum thermal stability, tensile strength, and initial modulus were recorded. The adhesive strength was found to be dependent on HMMM content, curing time, and temperature. The adhesive strength of crosslinked WBPU in the case of optimum HMMM content (8.46 wt%) was only slightly affected after immersing adhesive bonded nylon fabrics in water (for up to 2 days).

Synthesis and Properties of Cross-Linkable Waterborne Polyurethane/HMMM-CNT Nanocomposite

“…The crosslinked WBPU/HMMM-CNT nanocomposites, the crosslinked WBPU/HMMM and the conventional WBPU/CNT nanocomposites all showed higher water resistivity by absorbing less water comparing to this for conventional WBPU. The crosslinked WBPU/HMMM showed higher water resistivity due to the compact structure of the films made by crosslinking [23]. The conventional WBPU/CNT nanocomposites also showed higher water resistance due to having a structure with less free volume.…”

Developments in aqueous polyurethane and polyurethane-acrylic dispersion technology. Part II. Polyurethane-acrylic dispersions and modification of polyurethane and polyurethane-acrylic dispersions

“…Polyaziridines, and melamine-formaldehyde resins were evaluated as crosslinkers for APUD e.g. in [67,68], respectively, and two-component systems designed for automotive clear-coats based on APUD and on acrylic polyols, cured with water-dispersible polyisocyanates and containing different catalysts specific for NCO-OH reaction, were compared in [69]. Presently, three types of crosslinkers are used in most of two-component APUD systems offered on the market: polyaziridines (for room temperature curing) and melamine-formaldehyde resins or water-dispersible blocked polyisocyanates (for elevated temperature curing).…”

“…-adhesives, especially for footwear, textile and packaging industry [43,44,47,48,57,68,[101][102][103][104][105][106][107][108][109][110][111];…”

A fluoride degradable crosslinker for debond-on-demand polyurethane based crosslinked adhesives

“…The desire for high strength adhesives that exhibit healable and debondable properties range of environmental conditions has driven interest in this field over several decades. [1] Many different types of adhesives have been developed including hotmelt adhesives, [2][3][4][5][6] pressure sensitive adhesives [7][8][9] as well as reactive [10,11] and crosslinked adhesives [9,12,13]. Formulations commonly used to produce in crosslinked adhesives include those containing acrylates, [8,[13][14][15][16] epoxy resins [17][18][19][20][21] and polyurethanes.…”

“…Formulations commonly used to produce in crosslinked adhesives include those containing acrylates, [8,[13][14][15][16] epoxy resins [17][18][19][20][21] and polyurethanes. [2,12,22] Whilst crosslinked materials generally offer higher mechanical strengths over a greater temperature range than structure analogous linear adhesives [23] they are by their nature, insoluble and cannot be melt processed.…”