The replacement of plastic packaging by paperboard can significantly contribute to meeting sustainability goals in important application fields, such as in food packaging. The (water) barrier properties of paperboard‐based products need, however, to be improved. Waterborne coatings offer an environmentally friendly possibility to enhance these barrier properties, which in turn highly depend on the coating chemistry and film formation. Here, the relation between the characteristics of a waterborne coating and its water barrier performance is investigated. A waterborne polymer dispersion is prepared by emulsion polymerization, using an alkali‐soluble resin (ASR) as stabilizing agent. The ASR‐stabilized dispersion is applied as a coating on paperboard. During this application, the carboxylate groups of the ASR are converted to uncharged carboxylic acids. The coatings are characterized by Fourier‐transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM), and the water barrier properties are evaluated by dynamic vapor sorption (DVS) and the Cobb method. It is found that the water barrier performance is dominated by the carboxylate concentration remaining in the film, which is dependent on the moisture content. High drying temperatures improve particle deformation and polymer flow during coating formation, but do not influence the water barrier performance.
The effect of adding diethyl zinc as a chain transfer agent during the polymerization of propylene in heptane performed at 80 °C was studied. Although it was expected that the chain transfer would stop after precipitation of the polymer, the polymer molecular weight continued to increase throughout the whole of the polymerization. The presence of diethyl zinc had an additional effect that the polymerizations were devoid of reactor fouling. To unravel this phenomenon, the polymer particle morphology was studied. Under the conditions applied, surprisingly, uniform platelet-shaped polymer particles were formed. At high polymer content, these particles aggregate into microfibrillar structures consisting of nematic columnar strands of the same uniform platelets. The polymer particle morphology, as a result of controlled crystallization, is believed to play a crucial role in preventing reactor fouling.
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