Hanna de la Motte

Karlstad 091118CHEMICALCROSSLINKINGOF SOFTWOOD KRAFT FIBRE NETWORKS TOWARDSAN ABSORPTION PRODUCTHanna de la Motte, Kristoffer Lund, Harald Brelid, Gunnar WestmanChalmers University of TechnologyOrganic Chemistry, Forest Products and Chemical Engineering

Hanna de la Mottehanna.delamotte@chalmers.seWooDiThe aim of the research is to invent a moresustainableabsorption structure byimproving the propertiesof the wood-based materials and concurrentlyreduce the dependencyon non-renewable additives

Hanna de la Mottehanna.delamotte@chalmers.seIntroductionPorous network from pulp fibresSuper absorbent polymers (SAP)Decrease the use of nonrenewablematerialsBetter understanding of network

Hanna de la Mottehanna.delamotte@chalmers.seIntroductionWet stiffness of the fibre network has to be increasedIntra-fibre crosslinking in the fibre walls

Hanna de la Mottehanna.delamotte@chalmers.seExperimentalNever-dried bleached Scandinavian softwood kraft pulp supplied by Södra Cell VäroFractionationCrosslinkingPreparation of porous test padsWRV (Water Retention Value)Compression test

Hanna de la Mottehanna.delamotte@chalmers.seCrosslinkersThe reactions were performed in acetone, isopropanol or water at for 10-60 min usingdifferent crosslinker concentrations.

Preparation of padsHanna de la Mottehanna.delamotte@chalmers.se

WRV (g/g)Hanna de la Mottehanna.delamotte@chalmers.seWRVResults1.0510.950.90.850.80.750.70.650.6Reference(withactivation)Reference(noactivation)(S) withactivation(S) noactivation(L) withactivation(L) noactivation•Sodium hydroxide activates the hydroxy groups, while uncatalysed reaction occursat carboxylate groups belonging to hemicelluloses.• The crosslinked fibres have a substantially lower WRV than the reference fibres.

WRV (g/g)Hanna de la Mottehanna.delamotte@chalmers.seWRVResults0.90.80.70.60.50.40.30.20.10Cationic(L) Neutral• The cationic crosslinker showed a higher WRV compared to the non-cationiccrosslinkers.

Wet bulk (cm³/g)Hanna de la Mottehanna.delamotte@chalmers.seWet bulk, 15 kPaResults8.007.50y = -6,6211x + 10,729R² = 0,87177.006.50Crosslinker (L)6.005.505.000.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9WRV (g/g)• Only minor differences between the pads in the dry bulk test, strong hydrogen bonds.• The wet bulk follows the trend of the WRV, a high wet bulk gives a low WRV.• Crosslinking increases the stiffness of the network.

Structure recovery (cm³/g)Hanna de la Mottehanna.delamotte@chalmers.seStructure recoveryResults181614121086420Reference(withactivation)Reference(noactivation)(S) withactivation(S) noactivation(L) withactivation(L) noactivation•Crosslinked pads regain most of their initial structure.• Indicates that an increase in crosslinking in the fibre wall give more stable fibrils.• The data correlates well with the WRV and wet bulk.

Time (min)Time (min)Hanna de la Mottehanna.delamotte@chalmers.seMultivarate analysisResultsWet bulkStructure recoveryTemperatureTemperature• Longer reaction times are favourable as well as acetone as solvent.• A longer reaction time does not require the highest temperature for an improvedstructure recovery.

Hanna de la Mottehanna.delamotte@chalmers.seConclusionThe new crosslinking method increases the wet bulkand the structure recoveryAn evident correlation between the wet bulk and thewater retention value (WRV) can be seenLonger reaction times are favourable to improve thestructure recovery of the fibre network

Hanna de la Mottehanna.delamotte@chalmers.seFuture workThe results presented are the outcome of initial effortsin a larger research projectThe future requires more fundamental knowledgeabout the influence of chemical modifications towardsspecific fibre network propertiesImprovement of analytical methods on a molecularscale

AcknowledgementsHanna de la Mottehanna.delamotte@chalmers.se

Thank you!Hanna de la MotteChalmers University of Technologyhanna.delamotte@chalmers.se