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Polyvinyl alcohol (PVA) adhesives reinforced by microfibrillated cellulose (MFC) – adhesive properties and reinforcement mechanisms
Luleå University of Technology, Department of Engineering Sciences and Mathematics.
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The aim of the project was to investigate a green and sustainable replacement for boric acid in polyvinyl alcohol (PVA) adhesives for solid paperboard production. Boric acid acts as a cross-linker and tackifier in the adhesive but is classified as a harmful substance. Microfibrillated cellulose (MFC) was therefore investigated as a possible replacement for boric acid since it is produced from renewable and sustainable resources. In addition, it has hydroxyl groups available for interaction with the PVA, can be used to modulate the viscosity and can function under a variety of pH-values. 

For the industrial process, there are three basic characteristics which must be met by the newly developed adhesive, which have to be the same as for the boric acid-containing reference. These three are the viscosity, the pH-value, and the dry content. Furthermore, it is important that the initial wet tack and the final adhesive strength are at least as high as the reference’s. 

In this context, eight types of samples were investigated in total. Two were references, one prepared on industrial and the second on a laboratory scale according to a current industrial recipe. In the other six samples, the boric acid from the recipe was replaced by three different weight percentages of MFC of two different industrial grades. Both the dry content and the pH-value were not noticeably influenced by the addition of MFC. The viscosity however increased drastically with the increasing amount of MFC. The addition of MFC was enough to reach the three basic characteristics. In addition it was observed positive effects on a couple of other parameters that is beneficial for the glue.  

A test method for evaluating the initial wet tack of the adhesive was developed. It was shown, that the tack of the adhesive containing MFC is 40 % lower than the one of the reference material. Therefore, five additives were tested in the formulation, in combination with MFC. The most promising result led to a comparable initial tack and final strength as the reference. 

Place, publisher, year, edition, pages
2019. , p. 45
Keywords [en]
PVA adhesive, boric acid, MFC, cross-linkers, aluminum sulfate, initial wet tack
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-74609OAI: oai:DiVA.org:ltu-74609DiVA, id: diva2:1325841
External cooperation
Borregaard
Educational program
Materials Engineering, master's level
Supervisors
Examiners
Available from: 2019-06-18 Created: 2019-06-17 Last updated: 2019-07-03Bibliographically approved

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The full text will be freely available from 2022-07-01 10:11
Available from 2022-07-01 10:11

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