Spontaneous imbibition and colloidal aspects of inkjet printing

Water-based inkjet is one of the most abundant and versatile digital printing technologies. The subject of this thesis work is processes that take place once an inkjet drop lands on the surface of a porous printing media, with focus on liquid penetration due to capillary action (spontaneous imbibiti...

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Main Author: Oko, Asaf
Format: Doctoral Thesis
Language:English
Published: KTH, Yt- och korrosionsvetenskap 2014
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-152904
http://nbn-resolving.de/urn:isbn:978-91-7595-272-7
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spelling ndltd-UPSALLA1-oai-DiVA.org-kth-1529042014-10-03T06:46:31ZSpontaneous imbibition and colloidal aspects of inkjet printingengOko, AsafKTH, Yt- och korrosionsvetenskapStockholm,Sweden2014Water-based inkjet is one of the most abundant and versatile digital printing technologies. The subject of this thesis work is processes that take place once an inkjet drop lands on the surface of a porous printing media, with focus on liquid penetration due to capillary action (spontaneous imbibition) and aggregation of ink components. Knowing the details of these two sub-processes would allow optimization of printing processes as well as prediction of the final print result, based on material properties. The dynamics of drops as they land on different surfaces is captured at adequate time and length-scales by an optical imaging system coupled to an inkjet dispensing unit. The evaporation rate of drops is quantified and distinguished from imbibition, and their spreading behavior on porous substrates is characterized. A set of paper grades is used as examples to conclude that the events are captured accurately. Scaling laws for imbibition are derived from Darcy’s law for liquid flow through dimensional analysis and it is shown that the imbibition rate of drops is related to dimensionless volume and time groups, defined by the volume of the drop, porosity and permeability of the substrate, viscosity of the liquid and the Laplace capillary pressure that drives the imbibition. The approach is applied for two types of systems, one that includes simple liquids imbibing homogeneous and isotropic porous glass and the other that includes complex liquids imbibing heterogeneous and anisotropic paper. The addition of simple divalent salts to the paper surface is widely used to increase the print quality of water-based pigmented inkjet inks. Salt ions quickly diffuse into the inkjet droplets as they land on the paper and cause the ink to aggregate. This effect leads to the accumulation of colorant-pigments close to, or even on, the surface of the paper. Two salts, CaCl2 and MgCl2, are used to aggregate inkjet inks and their components. The interactions between the aggregated compounds are investigated by a set of experimental measurements that include sedimentation, confocal Raman microscopy, turbidity, rheology and electrophoretic mobility. It is concluded that the salt induced aggregation is led by a non-color polymeric ink component used as a pigment dispersant, and that CaCl2 induces stronger interactions between polymeric carboxylate groups compared to MgCl2. This ion specific effect cannot be explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory for electrostatic interaction in colloidal systems. <p>QC 20141002</p>Doctoral thesis, comprehensive summaryinfo:eu-repo/semantics/doctoralThesistexthttp://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-152904urn:isbn:978-91-7595-272-7TRITA-CHE-Report, 1654-1081 ; 2014:39application/pdfinfo:eu-repo/semantics/openAccess
collection NDLTD
language English
format Doctoral Thesis
sources NDLTD
description Water-based inkjet is one of the most abundant and versatile digital printing technologies. The subject of this thesis work is processes that take place once an inkjet drop lands on the surface of a porous printing media, with focus on liquid penetration due to capillary action (spontaneous imbibition) and aggregation of ink components. Knowing the details of these two sub-processes would allow optimization of printing processes as well as prediction of the final print result, based on material properties. The dynamics of drops as they land on different surfaces is captured at adequate time and length-scales by an optical imaging system coupled to an inkjet dispensing unit. The evaporation rate of drops is quantified and distinguished from imbibition, and their spreading behavior on porous substrates is characterized. A set of paper grades is used as examples to conclude that the events are captured accurately. Scaling laws for imbibition are derived from Darcy’s law for liquid flow through dimensional analysis and it is shown that the imbibition rate of drops is related to dimensionless volume and time groups, defined by the volume of the drop, porosity and permeability of the substrate, viscosity of the liquid and the Laplace capillary pressure that drives the imbibition. The approach is applied for two types of systems, one that includes simple liquids imbibing homogeneous and isotropic porous glass and the other that includes complex liquids imbibing heterogeneous and anisotropic paper. The addition of simple divalent salts to the paper surface is widely used to increase the print quality of water-based pigmented inkjet inks. Salt ions quickly diffuse into the inkjet droplets as they land on the paper and cause the ink to aggregate. This effect leads to the accumulation of colorant-pigments close to, or even on, the surface of the paper. Two salts, CaCl2 and MgCl2, are used to aggregate inkjet inks and their components. The interactions between the aggregated compounds are investigated by a set of experimental measurements that include sedimentation, confocal Raman microscopy, turbidity, rheology and electrophoretic mobility. It is concluded that the salt induced aggregation is led by a non-color polymeric ink component used as a pigment dispersant, and that CaCl2 induces stronger interactions between polymeric carboxylate groups compared to MgCl2. This ion specific effect cannot be explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory for electrostatic interaction in colloidal systems. === <p>QC 20141002</p>
author Oko, Asaf
spellingShingle Oko, Asaf
Spontaneous imbibition and colloidal aspects of inkjet printing
author_facet Oko, Asaf
author_sort Oko, Asaf
title Spontaneous imbibition and colloidal aspects of inkjet printing
title_short Spontaneous imbibition and colloidal aspects of inkjet printing
title_full Spontaneous imbibition and colloidal aspects of inkjet printing
title_fullStr Spontaneous imbibition and colloidal aspects of inkjet printing
title_full_unstemmed Spontaneous imbibition and colloidal aspects of inkjet printing
title_sort spontaneous imbibition and colloidal aspects of inkjet printing
publisher KTH, Yt- och korrosionsvetenskap
publishDate 2014
url http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-152904
http://nbn-resolving.de/urn:isbn:978-91-7595-272-7
work_keys_str_mv AT okoasaf spontaneousimbibitionandcolloidalaspectsofinkjetprinting
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