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Heterogeneous Film-Forming Latexes : Preparation - Morphology - Mechanical Properties

Karlsson, Ola LU (1997)
Abstract (Swedish)
Popular Abstract in Swedish

Marknaden för bestrukna tryckpapper har vuxit snabbare än för andra papperskvaliteter och förväntas göra så även i framtiden. Drivkraften bakom denna utveckling är kraven på bra färgåtergivning, framför allt inom reklamsektorn. Bestrukna papper blir en allt viktigare produkt för den svenska pappersindustrin men det är också ett område där konkurrensen och produktkraven ökar.



Bestrykningsskiktet består till största delen av ett oorganiskt pigment samt en syntetisk latex som bindemedel. Traditionellt har dessa latexar bestått av sampolymerer som tillverkats genom emulsionspolymerisation i ett steg. Strukturerade latexar med olika partikelmorfologier går att åstadkomma genom att... (More)
Popular Abstract in Swedish

Marknaden för bestrukna tryckpapper har vuxit snabbare än för andra papperskvaliteter och förväntas göra så även i framtiden. Drivkraften bakom denna utveckling är kraven på bra färgåtergivning, framför allt inom reklamsektorn. Bestrukna papper blir en allt viktigare produkt för den svenska pappersindustrin men det är också ett område där konkurrensen och produktkraven ökar.



Bestrykningsskiktet består till största delen av ett oorganiskt pigment samt en syntetisk latex som bindemedel. Traditionellt har dessa latexar bestått av sampolymerer som tillverkats genom emulsionspolymerisation i ett steg. Strukturerade latexar med olika partikelmorfologier går att åstadkomma genom att utföra polymerisationen i flera steg. Dessa latexar förväntas ge ett bättre papper att trycka på genom att nya egenskaper kan tillföras bestrykningsskiktet. Partiklar med en hård kärna och ett mjukt skal, så kallad ”core-shell” morfologi, kan till exempel kombinera en låg filmbildningstemperatur med en hög elasticitetsmodul, vilket inte är möjligt med traditionella latexar.



I denna avhandling har det visats att tillsats av små mängder karboxylsyramonomer vid tillverkningen av heterogena latexar har en mycket kraftig effekt på partikelmorfologin i latexen. Vidare har också graden av tvärbindning i den polymer som gjorts i första steget stor betydelse för den slutliga partikelmorfologin. Den inre partikelstrukturen påverkar i sin tur filmegenskaper hos filmer gjorda med dessa latexar. Störst mekanisk styrka och också bäst egenskaper vid försök med modellbestrykningar gav filmer gjorda av latexpartiklar med oregelbundna, hårda partikelrester från första polymersiationssteget. (Less)
Abstract
This thesis describes the preparation of heterogeneous latexes, which may serve as binders in coating applications, and the characterization of these. The latexes were prepared in two-stage seeded emulsion polymerization. The seed latexes used were polystyrene, whose properties had been changed by copolymerization with methacrylic acid (MAA) or divinyl benzene. The second-stage polymers were copolymers of styrene-co-isoprene-co-MAA or styrene-co-butadiene-co-MAA with varying compositions. The monomers in the second stage of polymerization were added either as a batch, or as a semi-continuous operation during the whole of the second stage or during various periods. The hydrophilicity of the polymeric phases was found to affect the particle... (More)
This thesis describes the preparation of heterogeneous latexes, which may serve as binders in coating applications, and the characterization of these. The latexes were prepared in two-stage seeded emulsion polymerization. The seed latexes used were polystyrene, whose properties had been changed by copolymerization with methacrylic acid (MAA) or divinyl benzene. The second-stage polymers were copolymers of styrene-co-isoprene-co-MAA or styrene-co-butadiene-co-MAA with varying compositions. The monomers in the second stage of polymerization were added either as a batch, or as a semi-continuous operation during the whole of the second stage or during various periods. The hydrophilicity of the polymeric phases was found to affect the particle morphology to a great extent. It was possible to change the particle morphology from an inverted core-shell to a core-shell morphology simply by adding small amounts of MAA to the monomer mixture used in the second stage of polymerization. Crosslinking of the seed particles had an even stronger effect on the morphology development.



Increased amounts of isoprene and MAA, as well as an increased phase ratio between the second-stage polymer and the seed was found to increase deviations between particle sizes obtained by TEM and QELS. Monomer swelling experiments showed that it was possible to estimate the monomer volume fraction at which the seed polymer glass transition temperature (Tg) and the so-called gel point occurred, through pressure measurements. When the pressure was monitored in the copolymerization of butadiene and styrene, the conversion at which crosslinking began was detected as an irregularity on the pressure curve plotted as a function of the second-stage monomer conversion.



Films made from the heterogeneous latexes were found to consist of two phases with the hard seed particles remaining as particles within the films. Mechanical measurements on the films showed that films made from latexes with crosslinked seed particles having irregular shapes, had the highest mechanical strength due to inter-particle contacts. Films made from latexes with core-shell morphologies exhibited lower mechanical strength due to the smooth seed particle structures left in the film. When latexes with crosslinked seed particles of irregular shapes were used as binders in model paper coating applications, they increased the porosity, gave greater light scattering ability and higher coating gloss of the coating layer, compared with latexes having core shell morphologies, due to retarded shrinkage of the coating during drying. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Tauer, Klaus, Max Plank Institute of Colloids and Interfaces, Teltow-Seehof, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
core-shell, particle morphology, heterogeneous latexes, particle size, crosslinking, hydrophilicity, poly(isoprene-co-styrene-co-methacrylic acid), monomer partitioning, internal particle viscosity, transmission electron microscopy (TEM), calorimetric reactor, two-stage, seeded emulsion polymerization, film morphology, mechanical properties, paper coating., Polymer technology, biopolymers, Polymerteknik
pages
163 pages
publisher
Department of Chemical Engineering, Lund University
defense location
lecture hall C, Center for Chemistry and Chemical Engineering
defense date
1997-05-31 10:15
external identifiers
  • Other:ISRN: LUTKDH/TKKT--97/1046--SE
ISBN
91-628-2532-1
language
English
LU publication?
yes
id
94d6f941-92af-4952-addf-898931c0c052 (old id 29430)
date added to LUP
2007-06-14 11:35:52
date last changed
2016-09-19 08:45:03
@misc{94d6f941-92af-4952-addf-898931c0c052,
  abstract     = {This thesis describes the preparation of heterogeneous latexes, which may serve as binders in coating applications, and the characterization of these. The latexes were prepared in two-stage seeded emulsion polymerization. The seed latexes used were polystyrene, whose properties had been changed by copolymerization with methacrylic acid (MAA) or divinyl benzene. The second-stage polymers were copolymers of styrene-co-isoprene-co-MAA or styrene-co-butadiene-co-MAA with varying compositions. The monomers in the second stage of polymerization were added either as a batch, or as a semi-continuous operation during the whole of the second stage or during various periods. The hydrophilicity of the polymeric phases was found to affect the particle morphology to a great extent. It was possible to change the particle morphology from an inverted core-shell to a core-shell morphology simply by adding small amounts of MAA to the monomer mixture used in the second stage of polymerization. Crosslinking of the seed particles had an even stronger effect on the morphology development.<br/><br>
<br/><br>
Increased amounts of isoprene and MAA, as well as an increased phase ratio between the second-stage polymer and the seed was found to increase deviations between particle sizes obtained by TEM and QELS. Monomer swelling experiments showed that it was possible to estimate the monomer volume fraction at which the seed polymer glass transition temperature (Tg) and the so-called gel point occurred, through pressure measurements. When the pressure was monitored in the copolymerization of butadiene and styrene, the conversion at which crosslinking began was detected as an irregularity on the pressure curve plotted as a function of the second-stage monomer conversion.<br/><br>
<br/><br>
Films made from the heterogeneous latexes were found to consist of two phases with the hard seed particles remaining as particles within the films. Mechanical measurements on the films showed that films made from latexes with crosslinked seed particles having irregular shapes, had the highest mechanical strength due to inter-particle contacts. Films made from latexes with core-shell morphologies exhibited lower mechanical strength due to the smooth seed particle structures left in the film. When latexes with crosslinked seed particles of irregular shapes were used as binders in model paper coating applications, they increased the porosity, gave greater light scattering ability and higher coating gloss of the coating layer, compared with latexes having core shell morphologies, due to retarded shrinkage of the coating during drying.},
  author       = {Karlsson, Ola},
  isbn         = {91-628-2532-1},
  keyword      = {core-shell,particle morphology,heterogeneous latexes,particle size,crosslinking,hydrophilicity,poly(isoprene-co-styrene-co-methacrylic acid),monomer partitioning,internal particle viscosity,transmission electron microscopy (TEM),calorimetric reactor,two-stage,seeded emulsion polymerization,film morphology,mechanical properties,paper coating.,Polymer technology,biopolymers,Polymerteknik},
  language     = {eng},
  pages        = {163},
  publisher    = {ARRAY(0xa7bc100)},
  title        = {Heterogeneous Film-Forming Latexes : Preparation - Morphology - Mechanical Properties},
  year         = {1997},
}