Cargando…
Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance
Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosit...
Autores principales: | , , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2018
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6025633/ https://www.ncbi.nlm.nih.gov/pubmed/29921774 http://dx.doi.org/10.3390/ma11061032 |
_version_ | 1783336325227741184 |
---|---|
author | Pereira, Pedro Pereira, João Paiva, Nádia. T. Ferra, João. M. Martins, Jorge M. Carvalho, Luísa. H. Magalhães, Fernão. D. |
author_facet | Pereira, Pedro Pereira, João Paiva, Nádia. T. Ferra, João. M. Martins, Jorge M. Carvalho, Luísa. H. Magalhães, Fernão. D. |
author_sort | Pereira, Pedro |
collection | PubMed |
description | Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosity increase that renders the resin unusable, occurs due to the progress of condensation reactions between the polymeric species present in the liquid medium. In order to achieve a stable resin formulation, dimethylurea (DMeU) was selected for being less reactive than urea. Dimethylurea is shown to co-polymerize with the UF polymer during the acidic synthesis condensation step. However, during storage it behaves like an end group blocker, due to its lower reactivity at basic pH. By adding 1.25% DMeU, it was possible to obtain a formulation that remained with stable viscosity during two-month storage at 40 °C. The reference UF resin remained stable only for eight days in these conditions. Wood particleboards produced with modified resins showed internal bond strengths of about 0.5 N·mm(−2), similar to the fresh reference UF resin, even when the resins were used after the two-month storage period. Formaldehyde content values were below the limit for E1 class, ≤8 mg/100 g oven dry board (EN 13986). |
format | Online Article Text |
id | pubmed-6025633 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-60256332018-07-09 Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance Pereira, Pedro Pereira, João Paiva, Nádia. T. Ferra, João. M. Martins, Jorge M. Carvalho, Luísa. H. Magalhães, Fernão. D. Materials (Basel) Article Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosity increase that renders the resin unusable, occurs due to the progress of condensation reactions between the polymeric species present in the liquid medium. In order to achieve a stable resin formulation, dimethylurea (DMeU) was selected for being less reactive than urea. Dimethylurea is shown to co-polymerize with the UF polymer during the acidic synthesis condensation step. However, during storage it behaves like an end group blocker, due to its lower reactivity at basic pH. By adding 1.25% DMeU, it was possible to obtain a formulation that remained with stable viscosity during two-month storage at 40 °C. The reference UF resin remained stable only for eight days in these conditions. Wood particleboards produced with modified resins showed internal bond strengths of about 0.5 N·mm(−2), similar to the fresh reference UF resin, even when the resins were used after the two-month storage period. Formaldehyde content values were below the limit for E1 class, ≤8 mg/100 g oven dry board (EN 13986). MDPI 2018-06-19 /pmc/articles/PMC6025633/ /pubmed/29921774 http://dx.doi.org/10.3390/ma11061032 Text en © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Pereira, Pedro Pereira, João Paiva, Nádia. T. Ferra, João. M. Martins, Jorge M. Carvalho, Luísa. H. Magalhães, Fernão. D. Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title | Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title_full | Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title_fullStr | Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title_full_unstemmed | Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title_short | Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance |
title_sort | copolymerization of uf resins with dimethylurea for improving storage stability without impairing adhesive performance |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6025633/ https://www.ncbi.nlm.nih.gov/pubmed/29921774 http://dx.doi.org/10.3390/ma11061032 |
work_keys_str_mv | AT pereirapedro copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT pereirajoao copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT paivanadiat copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT ferrajoaom copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT martinsjorgem copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT carvalholuisah copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance AT magalhaesfernaod copolymerizationofufresinswithdimethylureaforimprovingstoragestabilitywithoutimpairingadhesiveperformance |