Improvement of polyurethane film strength by H‐bonding crosslinking with hydroxylated melamine

Abstract

Due to the condensation reaction of hydroxylated melamine molecules is possible to take place in the whole pH range, especially in acidic water medium or at high temperature, losing its water solubility. In this work, freeze drying perfectly removes water at pretty low temperature, avoiding condensation reaction of hydroxylated melamine. Therefore, a hydroxylated melamine in solid form (MOH‐S) was prepared. It can be not only dissolved in water after storing for 180 days but also well dispersed in waterborne polyurethane emulsion. The addition of hydroxylated melamine significantly improves the tensile strength of polyurethane films by 170%. After soaking the films in water for 24 h, the tensile strength of WPU/30%MOH‐S film lost only 6%, but 34% loss for the neat. Fourier transform infrared spectroscopy peak fitting demonstrates that the H‐bonding degree of N─H in WPU/30%MOH‐S film is 20.72 that is much higher than 3.33 in neat WPU. This indicates that H‐bonding cross‐linked structure is formed between polyurethane chains and hydroxylated melamine molecules. This work provides an effective strategy for preparing stable hydroxylated melamine and enhancing the strength of polyurethane film.

The High‐Strength, Flexible Organic Solvent Driven Reversible “Deformation‐Recovery‐Reverse Deformation” Responsive g‐PLA/PPC/PVA Film for Contactless Actuation

“…Figure S2, Supporting Information, shows that the infrared spectrum of g‐PLA/PPC/PVA film contained structural characteristic peaks of PLA, PPC, and PVA (Supporting Information). The change of peak shape implied the CO … HO, OH … HO, or COOH … HO hydrogen bond interaction between g‐PLA and PVA after via PPC, [ 21,22 ] indicating that the sandwich film with good connectivity was successfully prepared (Figure S2b, Supporting Information).…”

Hierarchically Structured NH2‐MIL‐125/TiO2/Cellulose Composite Membranes With Enhanced Photocatalytic Performance

“…The world has been facing with environmental pollution and health harm due to the emission of organic pollutants, [1] hence there raises a challenge to treat the pollutants mildly and sustainably. [2] As compared with the various methods developed such as physical adsorption, [3] bio-degradation, [4] and membrane separation, [5] photocatalytic degradation is regarded as one of the most promising ways to address this problem due to its advantages like low energy consumption, eco-friendliness, as well as mild reaction conditions.…”

Study on the preparation and performance of SiC nanoparticle reinforced polyurethane coatings

“…The first is a chemical method which utilizes polyisocyanates and polyols to either introduce high energy covalent bonds, or increase the density of non-covalent bonds within PU structures. 7,8 The second is a physical method, which uses different reinforcing fillers to improve the mechanical properties of PU. [9][10][11] Nanoparticles are considered an ideal reinforcing filler due to their high strength, stiffness and "nano effect," 12 while a small addition has been shown to effectively improve the mechanical properties of PU.…”