The synthesis of waterborne polyurethane dispersions (PUDs) using an automated parallel reactor system was explored. Waterborne PUDs are an important class of polymer dispersion that can be used in many applications such as coatings for wood finishing, glass fiber sizing, adhesives, automotive topcoats, and other applications. Herein, we present the synthesis of aqueous PUDs using a Chemspeed Autoplant A100 TM automated parallel reactor system. This is the first time a PUD has been synthesized using an automated parallel reactor system. The synthesis involves the formation of an isocyanate-terminated prepolymer followed by neutralization, dispersion in water, and chain extension. Details of the methodology are discussed with respect to the process of writing the program for the synthesis to synthesizing the PUD itself with the Chemspeed. It is demonstrated that an aqueous PUD can be synthesized with an automated parallel process and the unit-to-unit results are similar. Process variables such as agitator design, rate of neutralization, and rate of water dispersion are varied as these are the three major factors which lead to the desired end product property. The controlled addition of neutralizer, water, and chain extender is an added advantage with this automated technique and gave consistent results in all the units. The PUDs were characterized for their particle size, viscosity, and percent solids.
Moisture-curable polysiloxanes were modified with ionic groups to enable specific interactions between the polysiloxane matrix and silica nanoparticle reinforcement. A trimethoxysilane-functional quaternary ammonium salt (QAS) was used to modify the polysiloxane matrix. A comparison of the mechanical properties of coatings containing QAS modification to analogous coatings without QAS modification showed that QAS modification resulted in a dramatic improvement in mechanical properties of silica nanoparticlereinforced coatings. QAS modification provided major enhancements in both tensile modulus and toughness. The coatings were characterized using positron annihilation spectroscopy, photo-acoustic FT-IR, differential scanning calorimetry, transmission electron microscope, and atomic force microscopy. The characterization results suggested that the QAS moieties present in the polysiloxane matrix undergo specific interactions with the surface of silica nanoparticles enabling an enhancement in interfacial adhesion between the polymer matrix and the nanoparticles. Most likely, the specific interaction that provided the enhanced mechanical properties was an ion-dipole interaction involving silanol groups present on the surface of the silica nanoparticles. The enhanced modulus and toughness of these polysiloxane materials may enable their application as a fouling-release coating for ship hulls, since current polysiloxane-based fouling release coatings suffer from poor mechanical properties and durability.
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