Effects of the reaction degree of melamine-formaldehyde resin on the structures and properties of melamine-formaldehyde/polyvinyl alcohol composite fiber

Abstract

Composite fibers made of polyvinyl alcohol (PVA) and melamine-formaldehyde (MF) resins with different reaction degrees were prepared by wet spinning. The phase structures of MF/PVA spinning dopes and composite fibers were observed by using optical microscope (OM) and scanning electron microscope with energy-dispersive X-ray spetroscopy (SEM-EDS). Crystal structures of composite fibers were studied by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The loss of MF resins in the spinning process was calculated by using Kjeldahl. The mechanical properties, the flame retardant property, the water resistant property, and the thermal stability of composite fibers were also tested. Results show that with an increase in the reaction degree of MF resin, the phase separation degrees of spinning dopes and composite fibers rise up, the size of MF microphase grows larger, and the loss of MF resin diminishes; consequently, the hot water resistance and the flame retardancy of the fiber ameliorate while the tensile strength and the thermal stability perform a tendency of dropping after rising.

Water‐resistant modification of poly(vinyl alcohol)/polyamidoxime chelating fibers prepared by emulsion spinning and their adsorption properties

“…Figure shows the FTIR spectra of composite fibers on different modification stages. The peak of the precursor PVA/PAN fiber at 3407 cm −1 was attributed to the vibrations of OH of PVA and the peaks at 2244 and 1730 cm −1 were due to the CN and COOCH 3 of PAN copolymer . After the crosslinking modification, the intensity of hydroxyl peak decreased and shifted to 3414 cm −1 (curve b), 3425 cm −1 (curve c), and 3418 cm −1 (curve d).…”

“…XRD patterns of composite chelating fibers are showed in Figure . The diffraction peaks at 11.13°, 19.17°, and 22.19° [Figure (a–d)] were attributed to (100), (101), and (200) crystallographic planes of PVA, and the peak at 16.8° of PAN was not observable due to the successful preparation of amidoximated composite fibers . The uncrosslinked PVA/PAO fiber showed stronger peak intensity than those of crosslinked composite chelating fibers, indicating that the crosslinking treatment would do harm to the structure of PVA/PAN precursor fibers.…”

“…Water contact angles (WCA) were measured with a drop shape analysis system (Kruss K100, Germany) using a 3 μL water droplet in ambient conditions. Hot water resistances of composite fibers were characterized by hot water softening point (SP) . The mechanical properties of modified fibers in dry and wet conditions were tested with the electronic fiber strength tester (Model LLY‐06, Laizhou Electron Instrument Co, Ltd., China) (a crosshead velocity of 20 mm min −1 and a gauge length of 20 mm).…”

Preparation of melamine–formaldehyde resin grafted by (3‐aminopropyl) triethoxysilane for high‐performance hydrophobic materials

“…The shell life of MF resin is rather short, normally less than 2 weeks . In the presence of triazine rings, MF materials are usually rigid and of weak toughness . Hydrophobicity and water resistance of MF materials are also poor because of containing abundant hydrophilic groups, such as methylol (CH 2 OH) .…”

Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning

“…To further improve the stability and spinnability of the resin, four kinds of modifiers, namely PVA, polyethylene glycol (PEG), thiourea, and benzonquanmine, are added to the MF system. As mentioned earlier, PVA is an indispensable modifier as the fiber‐forming and toughening agent in an MF resin solution and can improve the stability of the spinning solution . However, a large quantity of PVA cannot be added to the MF resin because it will deteriorate the fire retardancy and water resistance of MF fiber .…”