Viscoelastic properties and film morphology of heterogeneous styrene-butadiene latexes

Abstract

SYNOPSISHeterogeneous carboxylated styrene-butadiene (S/Bu) latexes were prepared by a twostage emulsion polymerization process, using three PS seeds with different molecular weights. The second-stage polymer was a copolymer with a fixed S/Bu ratio of 1 : 1 and a methacrylic acid (MAA) content of either 1 or 10 wt %. Morphological studies by transmission electron microscopy (TEM) as well as studies of the viscoelastic properties by mechanical spectroscopy have been performed on films prepared from the latexes. The studies showed that the glass transition temperature, Tg, of the second-stage polymer was considerably affected by copolymerization with MAA. An increase in the MAA content in the second-stage polymer increased the T, of this phase significantly. Addition of DVB as a crosslinking agent in the preparation of the PS seed phase substantially increased the rubbery moduli of the films, whereas the glass transition temperature of the second-stage polymer was unaffected. On the other hand, the presence of a chain transfer agent reduced the glass transition of the second-stage copolymer containing 1 w t % MAA dramatically, whereas the rubbery modulus was unaffected. When the MAA content was increased to 10 wt % the influence of the MAA monomer had a dominating effect on Te Latexes containing 10 wt % MAA had Tc values close to each other, regardless of chain transfer agent present in the second-stage polymerization. It was found that the morphology of the latex particles influenced the rubbery modulus of the films. The presence of irregularly shaped seed particles in samples prepared from a crosslinked PS seed had a considerable reinforcing effect on the films, whereas spherical seed particles originating from core-shell particles had a less reinforcing effect.

Reliability and validity of the self-report version of the Panic Disorder Severity Scale in Korea

“…One way to avoid this problem is the use of structured core/shell latex particles9–13 that have a high‐ T g polymer core and a low‐ T g film‐forming polymer shell. The corresponding dry films can then be described9–12, 14–16 as equivalent to an elastomeric matrix containing rigid inclusions. Another way to enhance significantly the mechanical properties of soft latex films is the physical blending of two separate latex dispersions with homogeneous particle morphologies.…”

Effects of thermal annealing on the viscoelastic properties and morphology of bimodal hard/soft latex blends

“…One way to avoid this problem is the use of structured core/shell latex particles [9][10][11][12][13] that have a high-T g polymer core and a low-T g film-forming polymer shell. The corresponding dry films can then be described [9][10][11][12][14][15][16] as equivalent to an elastomeric matrix containing rigid inclusions. Another way to enhance significantly the mechanical properties of soft latex films is the physical blending of two separate latex dispersions with homogeneous particle morphologies.…”

Resolving the Film-Formation Dilemma with Infrared Radiation-Assisted Sintering

“…Published in Langmuir (2011) 27(6):2176-2180 3 soft polymers -created with particle blends, 2,12,13 core-shell particles, 14,15 or heterogeneous particles 16,17 -also offer a means to enable film formation while also achieving film hardness. The past approaches to the film formation of hard latex coatings, along with their limitations, are listed in Table 1.…”