Film Formation of High Tg Latex Using Hydroplasticization: Explanations from NMR Relaxometry
The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField 1 H NMR at various relative humidities (RH). Polymer particles with glass-transition temperatures in the range...
Saved in:
Published in | Langmuir Vol. 35; no. 38; pp. 12418 - 12427 |
---|---|
Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
24.09.2019
|
Online Access | Get full text |
Cover
Loading…
Summary: | The film formation
of acrylic latex dispersions, containing different
amounts of carboxylic acid functional groups by the incorporation
of methacrylic acid (MAA), was studied with GARField
1
H
NMR at various relative humidities (RH). Polymer particles with glass-transition
temperatures in the range from 26 to 50 °C formed films at room
temperature because of hydroplasticization. It was found that with
an increased drying rate due to lower RH, the evaporation flux of
water was limited by the latex polymer. Only in the second stage of
drying this phenomenon was more obvious with increasing MAA content.
1
H NMR relaxometry was used to study the change of hydrogen
mobilities during film formation and hardening of the films. This
showed that the drying rate itself had no impact on the hydrogen mobility
in the latex films as measured via the
T
2
relaxation time. Hydrogen mobilities of water and the mobile polymer
phase only significantly decrease after most water has evaporated.
This implies that the rigidity of the polymers increases with the
evaporation of water that otherwise plasticizes the polymer through
hydrogen bonding with the carboxylic acid groups. This hardening of
the polymer phase is essential for applications in a coating. The
hydrogen mobilities were affected by the MAA concentration. Densities
of mobile hydrogens increase with increasing MAA content. This is
expected if the mobile protons are contained in the MAA groups. The
result thus confirms the role of carboxylic acid groups in hydrogen
bonding and plasticization of the copolymers. Hydrogen mobilities,
however, decrease with increasing MAA content, which is hypothesized
to be caused by the formation of dimers of carboxylic acid groups
that still hold water. They still enable short-range polymer hydrogen
mobility due to hydroplasticization but limit long-range polymer mobility
due to interaction between the carboxylic acid groups. |
---|---|
Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0743-7463 1520-5827 |
DOI: | 10.1021/acs.langmuir.9b01353 |