Surface morphology of latex film formed from poly(butyl methacrylate) latex in the presence of alkali-soluble resin

Abstract

The film morphology of emulsifier‐free poly(n‐butyl methacrylate) (PBMA) latex in the presence of post‐added alkali‐soluble resin (ASR) was studied using atomic force microscopy (AFM). The film morphology was monitored, from the nascent stage after water was evaporated from the dispersion, as a function of annealing temperature and its duration. The AFM results suggest strongly the formation of a hard shell of ASR, namely poly(styrene/alpha‐methylstyrene/acrylic acid) (SAA) over the soft PBMA particle. During annealing, the incompatibility of the two polymers leads to the migration and accumulation of SAA at the interstices and interfacial regions among the arrays of PBMA particles, and also at the film surface. The hard shell of SAA retards the diffusion of the PBMA molecules across the particle/particle interface and slows down the gradual coalescence of film formation. Annealing at high temperature ruptures the SAA shells and the PBMA particles interdiffuse at a faster rate than the SAA due to its lower Tg compared to that of SAA. The difference in the rates of fusion of the SAA and PBMA phases leads to the formation of indentations on individual particles at high annealing temperature and long annealing duration. The occurrence of this feature increases with the annealing temperature and its duration. These indentations are eventually transformed into ‘depressions’ on the latex films when the indentations at the top of the individual particles sag inwords at sufficiently high annealing temperature and long annealing time. The surface enrichment of SAA is confirmed by the results of fainer transform infrared spectroscopy with attenuated internal reflectance of the film surface. Copyright © 1999 John Wiley & Sons, Ltd.

Water Barrier Properties of Resin‐Stabilized Waterborne Coatings for Paperboard

“…Through this drying process, the polymer particles dispersed in water are concentrated and will in principle coalesce into a solid water‐insoluble polymer film, as reported for similar ASR‐stabilized colloidal dispersions. [ 31–38 ] Water evaporation and protonation of the ASR were monitored at room temperature (RT ≈ 20 °C) using FTIR, by the decrease of the characteristic OH stretching peaks of water between 3440 and 3200 cm −1 (Figure 2B) and the COO − vibration peak (asymmetric COO − stretching) at 1546 cm −1 , as well as, the increase of the COOH vibration peak (C─O stretching) at 1158 cm −1 (Figure 2C). When the dispersion was dried at RT a polymer film was formed.…”

“…These observations are in line with previous reports which indicated that the annealing of ASR-stabilized polymer films at elevated temperatures influences the film formation and the coating surface characteristics. [31,33,34,36,38] DSC measurements of the vacuum-dried free-standing films of the coating show two glass transition temperatures (T g ) at 24 and 90 °C (Figure S7, Supporting Information). The lowest T g corresponds to the acrylic polymer particles and the highest originates from the ASR.…”

“…[18,[27][28][29][30] The film formation of ASR-stabilized dispersions has also been extensively researched. [31][32][33][34][35][36][37][38] One of the key findings is that the high glass transition temperature (T g ) of the ASR shell around the polymer core hinders the diffusion of polymer chains across the particle boundaries. Thus, increasing the annealing temperature close to the T g of the ASR improves film formation, which is expected to enhance the coatings' properties.…”

“…Thus, increasing the annealing temperature close to the T g of the ASR improves film formation, which is expected to enhance the coatings' properties. Although several reports have been published on the optimization of ASR-based emulsion polymerizations [27,28,39,40] and film formation properties of ASR-supported dispersions, [31][32][33][34][35][36][37][38] the water barrier performance of ASR-stabilized waterborne coatings has not yet been addressed. Herein, we investigate the relation between the characteristics of an ASR-based waterborne coating and its water barrier performance.…”

The colloidal properties of alkaline‐soluble waterborne polymers

“…In this way, surfactant‐free polymer dispersions can be obtained. The film formation process of such polymer latexes way has been studied . By now, this technology is an established, commercially relevant polymer technology for a broad array of coatings and graphic arts applications .…”