Polyurethane‐based sealants modified by blending with Kraft lignin

Abstract

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=c9b4fe05-3368-4351-9b80-70406ba86f94 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=c9b4fe05-3368-4351-9b80-70406ba86f94 SynopsisAn investigation was conducted to establish the viability of blending Kraft lignin (L), a naturally occurring, readily available polymer resource, with polyurethane-(PU) based sealants.The sealants were tested in a detailed program where lignin-sealant blends, having blend ratios varying between 0 and 20 pbw L, were prepared on substrates of aluminum, mortar, and wood, and subjected to laboratory control (C), artificial weathering (AW), and natural weathering (NW) conditions. Results of tension testing showed that generally, lignin acts as a reinforcing agent which adds rigidity to the polymeric matrix, as indicated by the increase in toughness and modulus of blended sealants with the addition of lignin. In addition, the curing mode of PU, as determined by sequence hardness testing, was modified with the addition of lignin.

Preparation of Lignopolyols from Wheat Straw Soda Lignin

“…Lignin samples contain different types and quantities of these functional groups that could beu t i l i z e di nm a k i n ga n d / o r replacing a majority of petroleum-based products in the manufacture of industrial biomaterials and biocomposites 6,7 such as polyurethanes. 8,9 Lignin incorporation in polyurethane production has been one of the most intensively investigated applications. 7À12 In some cases, its presence modifies the polyurethane cure rate by contributing aromatic groups and increasing the degree of crosslinking.…”

“…Lignin acts as a reinforcing agent, which adds rigidity to the polymeric matrix. 9 Several studies have suggested that the solubility and the uniformity of the lignin are the foremost key parameters affecting its reactivity for polyol substitution in polyurethane production. 12,13 This in turn is directly dependent upon different classes of hydroxyl groups that may be present in lignin causing both electronic and steric factors affecting the lignin reactivity 14 in the polyurethane network.…”

Mechanical characteristics of sealants based on polyurethane-lignin polyblends

“…It is surmised that incorporation of lignin may contribute to an increase in the degree of crosslinking of PU. Further work in this initial series showed that the durability of the blended sealants, as measured by the change in mechanical properties of specimens subjected to natural and artillcial weathering programs, is generally neither hindered nor improved with the addition of lignin [1].…”

“…In previous papers the curing, and durability [1], morphology [2], miscibility [3], and swelling [4] characteristics of polyurethane (PU)-lignin polyblends were reported. Preliminary studies [1] indicated that the curing mode of PU sealants is modified with the addition of lignin, in that the initial setting time was reduced with the addition of lignin, but the rate of curing remained constant, indicating that the matrix hardens in direct proportion to the amount of lignin present in the blend.…”

“…Preliminary studies [1] indicated that the curing mode of PU sealants is modified with the addition of lignin, in that the initial setting time was reduced with the addition of lignin, but the rate of curing remained constant, indicating that the matrix hardens in direct proportion to the amount of lignin present in the blend. It is surmised that incorporation of lignin may contribute to an increase in the degree of crosslinking of PU.…”