Untersuchungen zur Thermoanalyse von Harnstoff‐Formaldehyd‐Schäumen

Abstract

ZUSAMMENFASSUNG:Differentialthermogravimetrische Untersuchungen an Harnstoff sowie an Monound Dimethylolharnstoff mit anschlieoender Auswertung durch IR-spektroskopische Analysen ergaben charakteristische differentielle Zersetzungsmaxima von Methylolgruppen und primlren Amidogruppen.Vergleichende thermische Abbauversuche an Harnstoff-Formaldehyd (UF)-Vorkondensaten und den daraus hergestellten Schlumen zeigten, dao ausgehartete UF-Schaume keine nachweisbaren Mengen an reaktiven Methylolendgruppen mehr enthalten. SUMMARY:Differential thermogravimetric investigations on urea, monomethylolurea and dimethylolurea followed by IR-spectroscopic analyses yield some characteristic maxima of differential degradation for methylol groups and primary amido groups.Corresponding thermal degradation experiments of urea-formaldehyde-precondensates and the therefrom produced urea-formaldehyde (Urn-foams showed that these cured foams don't contain any detectable amounts of reactive methylol endgroups. I . Einleitung und ProblemstellungHarnstoff-Forrnaldehyd-Schaurnstoffe (UF-Schaurnstoffe) gehoren zu den altesten industriell genutzten Schaurnstoffen. Ihre Vorteile gegeniiber vergleichbaren anderen Kunststoffschiiurnen liegen vor allern in ihrer schweren Entflarnrnbarkeit, der Herstellung aus preiswerten Ausgangsstoffen und der Moglichkeit der einfachen Verschaumung direkt am Verwendungsort.Dernentsprechend wurden iiber die Grundreaktionen von Harnstoff rnit Forrnaldehyd bereits seit langerer Zeit eingehende Untersuchungen durchgefiihrt ' '. Trotz dieser urnfangreichen Arbeiten ilber die sogenannten UF-Vorkondensate ist uber die chernische und rnorphologische Struktur der dar-0 1984 Hiithig& Wepf Verlag, Basel

Preparation and structural characterization of melamine–methylurea–formaldehyde resin and its blends separately with ethyl cellulose, starch, teakwood, and almond shell powders by 13C NMR, IR, TGA, and SEM techniques

“…(2) From 250 to 300°C, an oxidative degradation of methylurea units seems to occur. (3) From 350 to 400°C, i.e., an oxidative degradation of melamine units,48, 49 as the degradation process of resin and cellulosic blends by breaking the bonds release oxygen, which is used for oxidative degradation (4) demarcates the degradation of the residual fraction that starts from 450°C. It is evident that methylurea methylol undergoes an oxidative degradation at lower temperature than those of the melamine ones.…”

“…But due to the superior quality of resin and simplicity in preparation, the melamine–urea–formaldehyde (MUF) polycondensates are in use as adhesives for pulpwoods,29–35 IR36 and NMR37–42 spectroscopy have investigated their structures. An enormous studies on MUF,43–47 melamine–formaldehyde,48 melamine–urea, and urea–formaldehyde49 have been conducted in detail, while studies on MMUF resin preparation and its blends with cellulosic items have not been reported. This manuscript reports the structural, morphological, and thermal stability investigations on the resin and its blends.…”

New Materials for Biosensor Construction

“…How do the molecules maintain identity under different polarity and electrostatics for sequential structural reorientations? It becomes more important in case of biomolecules such as EPC which being weakly polar involved in biosensor signal as emulsifying agent (9)(10)(11). For example, a detection of bound water at moon is an input and incentive to intensify search and research of undiscovered molecular world (12).…”

Molecular Interactions of First and Second Tier Dendrimers, Anticancer Molecules, Analyzed with Densities and Viscosities of Their Aqueous Mixtures

“…It forms many channels and cavities 12,13 to trap foreign material like boron neutron capture therapy 14 and many others 9, 14-17 in medical sciences, drug delivery systems, biomedical, biophysical, and biochemical 9,18 fields using friccohesity, a dual force theory (DFT) with respect to chiral friccohesity. The molecules are biodegradable in nature with respect to polar solvent 1 and also ecofriendly.…”