Film formation of heterogeneous latex systems—a comparative study by mechanical testing, electron microscopy, interferometry and solid state NMR

Abstract

The inÑuence of latex morphology, composition and drying conditions on Ðlm formation and Ðlm properties is investigated for heterogeneous poly(acrylate) latex model systems. For blends of small latex particles water evaporation is the rate limiting process of Ðlm formation and the critical hard phase content reaches theoretical predictions. Upon increasing the size of the particles, their deformation becomes rate limiting which results in lower critical hard phase content, which signiÐcantly depends on Ðlm thickness. Film forming properties of blends are compared with that of heterogeneous lattices possessing di †erent morphology. According to conventional measurements of the minimum Ðlm forming temperature, core-shell lattices with a glassy (high shell are non-Ðlm forming. A more thorough investigation reveals signiÐcant di †erences T g ) depending on latex composition and even Ðlm formation. It is demonstrated that this Ðlm formation is rate limited by particle deformation. Electron microscopy, turbidity measurements, electromechanical testing and interferometrical thickness determination are used to investigate Ðlm densiÐcation and particle deformation. Solid state NMR spin di †usion measurements are applied to characterize morphological changes during Ðlm formation and interdi †usion.

Effect of Bimodality on the Adhesive Properties of Pressure Sensitive Adhesives: Role of Bimodal Particle Size and Molecular Weight Distributions

“…In terms of film formation, it has been reported that smaller particles deform faster and take less time to fill interstitial voids while larger particles show only superficial deformation in the same time frame because, in larger particles, the polymer chains have to flow over longer distances. 45,46 This means that the three bimodal PSD latexes prepared in this study led to various film formation paths and, thus, different particle surfaces which in turn affected loop tack. It must also be considered that small and large particles could contain different surfactant amounts.…”

Internal Stresses during Film Formation of Polymer Latices

“…In this picture, the air-water interface exerts tensile stress in the topmost This material cracks extensively when dried at a temperature below 44 °C. 28 The fluctuations occurring on the time scale of some minutes mark the growth of cracks. prevents lateral stress.…”

“…The film formation properties of this compound are rather complex and will be reported in detail in a separate publication. 28 Important in the context of this work is the fact that cracks evolve unless the dispersion is dried very slowly or at temperatures much higher than 44 °C. Strictly speaking, 44 °C is not an MFT because stable films do form at even lower temperatures provided that the system is given enough time.…”

“…Figure 7. Stress histories as a function of temperature for the drying of a core-shell latex with an initial thickness of 15 µm.This material cracks extensively when dried at a temperature below 44 °C 28. The fluctuations occurring on the time scale of some minutes mark the growth of cracks.…”

PMMA-doped CdSe quantum dots as saturable absorber in a Q-switched all-fiber laser

“…For the second phase, the CdSe QD powder was mixed with PMMA by an emulsion polymerization process [35] . The PMMA functions as a host material due to its characteristics of high optic transparency and low photoluminescent background [36] .…”