Variation of MUF and PMUF resins mass fractions during preparation

Abstract

ABSTRACT:The variation of molecular mass distribution with the progress of the reaction was studied for the following: (i) sequential-type melamine-urea-formaldehyde (MUF) resin formulations in which the sequence of addition of chemicals follows well-defined species reactivity principles; (ii) a nonsequential MUF formulation in which simultaneous melamine and urea competition for formaldehyde yields a MF resin cocondensed with small amounts of urea. This resin became soaked with reacted and unreacted monomeric urea species. (iii) A PMUF resin, namely a MUF resin with a small proportion of phenol (7.8% by weight on melamine and urea) cocondensed with the main MUF fraction. All the formulations used were industrial resins formulations in current use. Development and variation of molecular mass fractions, from which performance and other useful resin parameters depend, have been found to depend on the type of resin formulation used for these type of aminoplastic resins. The two very different MUF resin formulations yielded different variations in molecular mass fractions during the progress of the reaction and during the so-called ambient temperature "maturing" of the resin. The PMUF resin also showed both similar and different fractions present during manufacturing and during short term ageing at ambient temperature. While similarities in recurrent fractions and in trends are common to all the three different formulations, differences between them are also clearly observed. A major proportion of the reaction of some of the aminoplastic resins examined also occurs on ageing (i.e."maturing" of the resin at ambient temperature), this appearing to be an essential phase of the resin preparation process.

Effect of Melamine Allocation Proportion on Chemical Structures and Properties of Melamine-Urea-Formaldehyde Resins

“…The performance of MUF resins closely relies on the resin formulation and synthesis parameters. Lei et al (2006) found that formulations resulted in different variations of molecular mass distribution during the progress of reaction and ageing of MUF resins. Xu et al (2009) investigated the curing behavior and adhesion performance of a MUF resin synthesized by the staged addition of melamine.…”

Testing by fourier transform infrared species variation during melamine–urea–formaldehyde resin preparation

“…Only recently did a study appear that followed the development of the different mass fractions and, by inference, the development of the average molecular species as functions of the type of formulation used. 6 A later study 7 investigated in depth what chemical species are formed during the preparation of MUF resins and how they evolve throughout the complete preparation procedure of the resins by using 13 C-NMR and matrix-assisted laser desorption/ionization time-offlight (MALDI-TOF) mass spectrometry to examine a sequential MUF formulation. Although a great variety of MUF formulations exist and are used industrially, the greater majority of them are produced according to so-called sequential formulations, in which the sequence of addition of the chemicals follows welldefined species reactivity principles.…”

Urea–formaldehyde resin prepared with concentrated formaldehyde

“…The results of 13 C-NMR indicated that the increase in the concentration of formaldehyde would cause more ether bridges and less methylene bridges in the final resin system, which was consistent with that reported before. [13] Since ether bridges are thought to be not so stable as methylene bridges and be more likely to be rearranged to methylene bridges by splitting off formaldehyde, [6] it is recommended to avoid such ether bridges in UF resins. The higher content of methylol groups in UF2 was also proved by 13 C-NMR seen from Table 3.…”

“…The measure and calculation of 13 C-NMR made reference of [13]: The 400 μl liquid sample was directly mixed with 50 μl DMSO-d6 for 13 C-NMR determination. The spectra were obtained on a Bruker AVANCE 600 NMR spectrometer using 12 μs pulse width (90°).…”

“…The objectives of this work was to analyze the structure of the UF resin prepared with formaldehyde with higher concentration and to explore the effects of the concentration of formaldehyde on the properties of the final resin system. Although UF concentrate with more than 40 wt% formaldehyde is sometimes used for the preparation of UF resin, [13,14] the study on the preparation of UF resin directly with formaldehyde with high concentration is rather few. The significance of this research was as follows: (1) to avoid the vacuum dewatering, which has to be done to increase the resins' solid content for preparation of some kinds of wood panels, especially for the preparation of particleboards.…”