Modification Of Urea-formaldehyde Resin Research Articles

Study on Performance and Structural Design of Bamboo Helmet

The helmet is a mandatory tool for safe production, and bamboo helmets can be used as an alternative to the traditional plastic safety helmet. In this study, bamboo helmets were modified with urea-formaldehyde resin and have shown excellent impact resistance, good color sensitivity, and high gloss. The excellent performance of the bamboo helmet comes from the structure designed by imitating the gradient characteristics of bamboo and the modification of urea-formaldehyde resin. The pores and defects of bamboo in the helmet modified by urea-formaldehyde resin are filled and repaired. The chemical combination of urea-formaldehyde resin and bamboo reduces bamboo’s crystallinity and improves the bamboo helmet’s impact resistance. The development of bamboo helmets provides a supplement and option for the traditional helmet market while opening up new ways of bamboo utilization.

Modification of Urea Formaldehyde Resin with Pyrolytic Oil on Particleboard

Modification of Urea Formaldehyde Resin with Pyrolytic Oil on Particleboard

ADHESIVE COMPOUND FOR PRODUCTION OF WOOD CHIPBOARD COMPOSITE MATERIALS

Currently, the chipboard production is a priority direction in the development of woodworking industry. In addition to purely technological aspects, the environmental safety of chipboard production is the most relevant, which is reflected in the modern patent, scientific and technical literature. One of the main ways to improve the environmental safety and efficiency of the chipboard production is a directed modification of urea-formaldehyde resin, the main binder, in order to significantly change the emission of free formaldehyde from finished structures. This problem is solved by modifying both the binder and the hardener. Ammonium chloride, oxalic acid, hydrochloric acid, ammonium silicofluoride, combined hardener in the composition of ammonium chloride and ammonia water and others are used as a hardener, and a polyacrylamide solution is used as resin modifier. The gas phase of wood chipboards aged at 1100 °C for 30 min was studied using a method of the vapor-phase gas chromatographic analysis with the mass spectrometer detection. Results show that polyacrylamide sample with modifying additives has the smallest quantity of components releasing in the gas phase. Concerning gas emission, all studied wood chipboard samples meet the sanitary rules for the use of polymeric materials in construction and furniture production and the sanitary and hygienic assessment of polymer and polymer-containing building materials and structures intended for use in the construction of residential, public and industrial buildings.

Modification of urea-formaldehyde resin adhesives with blocked isocyanates using sodium bisulfite

Polymeric 4-4 diphenyl methane diisocyanate (pMDI) was blocked with an aqueous sodium bisulfite solution to obtain water-dispersible blocked pMDI (B-pMDI) resin with different HSO3/–NCO mole ratios for the modification of urea-formaldehyde (UF) resin. Fourier transform infrared (FTIR) spectra of the B-pMDI resin clearly showed that all isocyanate groups of the pMDI resin were successfully blocked by sodium bisulfite. As the HSO3/–NCO mole ratio increased, the de-blocking temperature of the B-pMDI resin also increased. Two addition levels (1% and 3%) of the B-pMDI resin with different HSO3/–NCO mole ratios were mixed with UF resins and used as an adhesive for plywood. The gel time of the UF/B-pMDI resins decreased to a minimum at a mole ratio of 0.9 and then increased with the HSO3/–NCO mole ratio, and was consistent with the peak temperature (Tp). However, as the HSO3/–NCO mole ratio increased, the viscosity of the modified UF resins by 1% B-pMDI resin addition slightly increased, whereas those of modified resins with 3% B-pMDI resin addition rapidly increased. The adhesion strengths of plywood bonded with the hybrid resins were greater for 1% B-pMDI resin addition than for 3% B-pMDI resin addition. Formaldehyde emission of plywood bonded with the UF/B-pMDI resins significantly decreased up to 34% by the addition of B-pMDI resin at a mole ratio of 1.8. These results suggest that the modification of UF resins by mixing with water-dispersible B-pMDI resin can be a method for improving the water resistance and formaldehyde emission of UF resins for wood-based composites.

Study on Modification of Urea Formaldehyde Resin with Keratin

As the main adhesive types in wood-based panel industry，urea-formaldehyde has such shortcomings as high levels of free formaldehyde content and formaldehyde emission of its bonding product. In this experiment, we try to modify urea-formaldehyde resin with keratin through copolymerization reaction. Through the determination of such reaction technology as molar ratio, adding sequence of keratin and adding amount of keratin, we finally synthesized the low toxic urea resin. The results show that the optimum molar ratio is 1.3:1, the adding amount of keratin is 5% and adding keratin after the third feeding of urea is the best choice. By optimizing the synthesis process, we ultimately get the low toxicity modified urea-formaldehyde resin. At the same time, modified urea-formaldehyde resin cost has been reduced because extensive sources of keratin and low cost.

Effects of urea–formaldehyde resin mole ratio on the properties of particleboard

The use of urea–formaldehyde (UF) resins with lower contents of free formaldehyde in the board industry has led to products with very low emissions of formaldehyde. This study gives a detailed account of the influence on the mechanical and physical properties of the particleboard using UF resins with different mole ratios of formaldehyde:urea within the range 0.97–1.27. The mole ratio influenced not only the thickness swelling (TS) and water absorption (WA) but also the internal bond strength (IB) and the modulus of rupture (MOR) if the manufacturing process was optimized. The investigation revealed clearly that at mole ratios of formaldehyde giving the emission class El the MOR, IB, TS, and WA of particleboard deteriorated. Compensation for the deterioration could be provided through a higher dosage of resin or through the modification of UF resin. However, both alternatives meant that the product would be more expensive.

13C NMR study of modification of urea formaldehyde resins by furfuryl alcohol

A method has been devised for determining from the 13C NMR spectra the structure of the products of interaction of furfuryl alcohol with urea and formaldehyde. Hemiformals form in a neutral medium. Boiling at pH 5·5 leads to the formation of dimethylene ether bridges between the furane cycles and the nitrogen atoms of the urea residues so that the additive is chemically incorporated into the structure of the resin. At pH 3·5 methylene bridges form between the cycles and secondary nitrogen atoms; a considerable part of furfuryl alcohol reacts over the second α-carbon atom of the furane cycle. The crosslinked resin also has methylene bridges between the furane cycles and the tertiary nitrogen atoms of the urea residues.