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Ammonium Lignosulfonate Adhesives for Particleboards with pMDI and Furfuryl Alcohol as Crosslinkers
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Linnaeus University.ORCID-id: 0000-0002-5188-4817
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).ORCID-id: 0000-0002-6909-2025
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).ORCID-id: 0000-0003-0883-2306
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).ORCID-id: 0000-0002-6390-7377
2019 (Engelska)Ingår i: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, nr 10, s. 1-17, artikel-id 1633Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Tightening formaldehyde emission limits and the need for more sustainable materials have boosted research towards alternatives to urea-formaldehyde adhesives for wood-based panels. Lignin residues from biorefineries consist of a growing raw material source but lack reactivity. Two crosslinkers were tested for ammonium lignosulfonate (ALS)—bio-based furfuryl alcohol (FOH) and synthetic polymeric 4,4′-diphenylmethane diisocyanate (pMDI). The addition of mimosa tannin to ALS before crosslinking was also evaluated. The derived ALS adhesives were used for gluing 2-layered veneer samples and particleboards. Differential Scanning Calorimetry showed a reduction of curing temperature and heat for the samples with crosslinkers. Light microscopy showed that the FOH crosslinked samples had thicker bondlines and higher penetration, which occurred mainly through vessels. Tensile shear strength values of 2-layered veneer samples glued with crosslinked ALS adhesives were at the same level as the melamine reinforced urea-formaldehyde (UmF) reference. For particleboards, the FOH crosslinked samples showed a significant decrease in mechanical properties (internal bond (IB), modulus of elasticity (MOE), modulus of rupture (MOR)) and thickness swelling. For pMDI crosslinked samples, these properties increased compared to the UmF. Although the FOH crosslinked ALS samples can be classified as non-added-formaldehyde adhesives, their emissions were higher than what can be expected to be sourced from the particles. 

Ort, förlag, år, upplaga, sidor
MDPI, 2019. Vol. 11, nr 10, s. 1-17, artikel-id 1633
Nyckelord [en]
biorefinery lignin; wood panels; sustainable adhesives; adhesive penetration; particleboard properties; formaldehyde emissions
Nationell ämneskategori
Polymerteknologi
Forskningsämne
Teknik, Skog och träteknik
Identifikatorer
URN: urn:nbn:se:lnu:diva-89556DOI: 10.3390/polym11101633ISI: 000495382700102PubMedID: 31658588OAI: oai:DiVA.org:lnu-89556DiVA, id: diva2:1360575
Tillgänglig från: 2019-10-14 Skapad: 2019-10-14 Senast uppdaterad: 2019-11-21Bibliografiskt granskad
Ingår i avhandling
1. Towards low-emitting and sustainable particle and fibreboards: Formaldehyde emission test methods and adhesives from biorefinery lignins
Öppna denna publikation i ny flik eller fönster >>Towards low-emitting and sustainable particle and fibreboards: Formaldehyde emission test methods and adhesives from biorefinery lignins
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

High volumes, fast production speed, and low material costs have been historically the driving factors of the particle- and fibreboard industries. However, in recent years the fossil-fuel dependency and health issues of the formaldehyde-containing adhesives used in the production have gained attention from both legislators and consumers. The latest example of legislation development is the change that the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety of Germany  (Bundesministerium für Umwelt, Naturschutz und Nukleare Sicherheit) made to their testing method, effectively lowering the formaldehyde emission levels of wood-based panels in Germany from the European emission level of 0.1 ppm (E1, EN 717-1) to 0.05 ppm. As the emission levels of requirements decrease, market opportunities arise for formaldehyde-free bio-based adhesive systems. The aim of this thesis was thus to evaluate the different formaldehyde test methods at low emission levels (<0.05 ppm), and to explore new adhesive alternatives to the formaldehyde and petroleum-based systems used today.

As formaldehyde emissions decrease, choosing the right measurement method becomes increasingly important. Repeatability and correlation between the main European and American formaldehyde measurement chambers, described in EN 717-1 and ASTM D 6007 standards respectively, were determined. In addition, an alternative fast factory method based on emissions was evaluated, and the effect of reducing the conditioning time before emission measurements was investigated. A literature research was conducted on different bio-based raw materials in order to review their potential, from both scientific and industrial viewpoints, as alternatives to the current petroleum-derived and formaldehyde-based adhesives. Lignin residues from biorefinery processes were chosen for further testing due to their increasing volumes and potential to suit various pathways for adhesive making. Three different biorefinery lignins were compared, and ammonium lignosulfonate was chosen for making adhesives for particleboards by using one petroleum-based and one bio-based crosslinker.

The main conclusion of the formaldehyde emission part of the thesis was that formaldehyde emissions can be measured both accurately and quickly at low levels using chamber methods, even at factory environment. There was a good correlation between the American D 6007 and European EN 717-1 chamber methods at emission levels <0.05 ppm for both particleboards (r2 = 0.9167) and fibreboards (r2 = 0.9443). Further understanding on the effect of edge-sealing of boards and analytical methods described in the standards was obtained. It was confirmed that a fast chamber method with 1 day conditioning and 15 minutes measuring time could be used for factory formaldehyde control for most board types.

The bio-based adhesives’ literature review revealed a large amount of studies on different sustainable adhesive systems, some of which seem promising. Both soy protein and tannin were found to be partially commercialized, with certain pre-requisites. Kraft-lignin was especially well researched, but was found to be difficult to use for other applications than partial replacement of phenol in phenol-formaldehyde (PF) adhesives due to poor water solubility and purity. Lignin residues from biorefinery processes were found to be a less studied, growing raw-material source with a lot of potential. Thus, supercritical water hydrolysis lignin (SCWH) and two biorefinery lignosulfonates were chemically and thermally characterized, and evaluated as raw materials for value-added applications, including adhesives. SCWH lignin was found to have more β-R linkages and lower amount of impurities than the lignosulfonates. High amount of phenolic hydroxyl groups indicated that SCWH would be well suited for phenol replacement in PF adhesives. The two lignosulfonates had more aliphatic hydroxyl groups, which can be interesting for other crosslinking reactions than PF. Ammonium lignosulfonate (ALS) was chosen for further evaluation as having slightly better properties than sodium lignosulfonate (SLS). ALS was combined with one bio-based crosslinker, furfuryl alcohol (FOH), and one synthetic crosslinker, 4,4’-diphenylmethane diisocyanate (pMDI), and tested as particleboard adhesive. Although in veneer tensile shear strength testing the crosslinkers worked equally well, pMDI provided significantly better results in particleboards. In addition, higher emissions than what can be expected from wood particles alone were detected from the particleboard samples crosslinked with FOH, even though FOH can be classified as non-formaldehyde added adhesive system. Further research is needed to elucidate how much the lignin contributes to the final adhesion strength when it is used together with pMDI.

This thesis has provided new insights on formaldehyde emissions and bio-based adhesives towards healthier and more sustainable particle- and fibreboards. It has been proven that formaldehyde emissions can be measured accurately at emission levels of wood, enabling comparisons of formaldehyde-free systems. Formaldehyde-free adhesives based on a biorefinery lignin type and pMDI showed promising results for particleboards. However, these results need to be improved by different modifications of the lignin in order to bring the adhesive system to the economical and performance level required by the particleboard industry.

Ort, förlag, år, upplaga, sidor
Växjö: Linnaeus University Press, 2019. s. 78
Serie
Linnaeus University Dissertations ; 363
Nyckelord
Wood board industry, chamber methods, dynamic microchamber (DMC), bio-based adhesives, lignosulfonates, supercritical water hydrolyzed lignin, crosslinkers, fibreboards, particleboards
Nationell ämneskategori
Polymerteknologi Polymerkemi
Forskningsämne
Teknik, Skog och träteknik
Identifikatorer
urn:nbn:se:lnu:diva-89560 (URN)978-91-88898-98-2 (ISBN)978-91-88898-97-5 (ISBN)
Disputation
2019-11-06, Homeros (F332), Hus F, Växjö, 13:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
KK-stiftelsen, project titled “New environment-friendly board materials”
Tillgänglig från: 2019-10-14 Skapad: 2019-10-14 Senast uppdaterad: 2019-11-12Bibliografiskt granskad

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