Abstract
New waterborne polyurethane-urea dispersions with adequate adhesion and cohesion properties have been synthesized by reacting isophorone diisocyanate, copolymer of ether and carbonate diol polyol and three amino-alcohols with different number of OH groups chain extenders using the prepolymer method. The waterborne polyurethane-urea dispersions were characterized by pH, particle-size distribution, and viscosity, and the polyurethane-urea films were characterized by attenuated total reflectance infrared (ATR-IR) spectroscopy, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and plate-plate rheology (temperature and frequency sweeps). Polyurethane-urea pressure-sensitive adhesives (PUU PSAs) were prepared by placing the waterborne polyurethane dispersions on polyethylene terephthalate (PET) films and they were characterized at 25 °C by creep test, tack and 180° peel test. The waterborne polyurethane-urea dispersions showed mean particle sizes between 51 and 78 nm and viscosities in the range of 58–133 mPa·s. The polyurethane-urea films showed glass transition temperatures (Tgs) lower than −64 °C, and they showed a cross of the storage and loss moduli between −8 and 68 °C depending on the number of OH groups in the amino-alcohol chain extender. Different types of PUU PSAs (removable, high shear) were obtained by changing the number of OH groups in the amino-alcohol chain extender. The tack at 25 °C of the PUU PSAs varied between 488 and 1807 kPa and the 180° peel strength values ranged between 0.4 and 6.4 N/cm, and their holding times were between 2 min and 5 days. The new PUU PSAs made with amino-alcohol chain extender seemed very promising for designing environmentally friendly waterborne PSAs with high tack and improved cohesion and adhesion property.
Highlights
Polyurethane-urea (PUU) materials are versatile polymers commonly used as adhesives and coatings [1]
All Waterborne Polyurethane-Urea Dispersions (WPUUs) synthetized with the different amino-alcohols chain extenders are translucent and stable for more than six months
All WPUUs display relatively ample tails indicating the existence of somewhat broad particle-size distributions in the range of 30–180 nm
Summary
Polyurethane-urea (PUU) materials are versatile polymers commonly used as adhesives and coatings [1]. Waterborne polyurethane-urea materials are obtained by reacting polyol, diisocyanate, internal emulsifier and chain extender, and they show segmented structures consisting of soft (SS) and hard. The soft segments are made of polyol and provide flexibility to the PUU, whereas the hard segments are made by reaction of the diisocyanate and the chain extender, and they impart mechanical properties. The ionic interactions of the pendant groups of the internal emulsifier in different polymeric chains contribute to the mechanical properties of the PUU. Both hard and soft segments can be organized in either amorphous or crystalline ordered domains by formation of hydrogen bonds between them, and this determines the PUU properties [6]
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