Synthesis and characterization of branched, functional polyurethane dispersions as a technology platform for self-crosslinking textile coatings
Durmuş Sayar, Ayşe (2017) Synthesis and characterization of branched, functional polyurethane dispersions as a technology platform for self-crosslinking textile coatings. [Thesis]
Waterborne polyurethane dispersion technology has been increasingly becoming significant in the market of environmentally friendly materials for advanced coating and adhesive applications due to their high performance and zero or near zero volatile organic content (VOC) in recent decades. Although the versatile chemistry of polyurethanes enables one to design high performance coating, adhesive or elastomeric materials for a wide range of applications, current synthetic routes for linear polyurethanes have limitations in the introduction of chemical functional groups on the polymer backbone. The present study focuses on the synthesis and characterization of waterborne, branched polyurethanes with a multitude of functional end-groups via the oligomeric A₂ + B₃ methodology. While the waterborne nature of final products makes them user and environmentally friendly, the presence of functional end-groups makes them suitable coating and adhesive materials for a variety of surfaces, specifically textiles. In this thesis, one-component and self-crosslinking, or two-component, amino- or silane functional polyurethane dispersions were synthesized and examined in detail. The influence of the degree of branching, nature of the soft segment and chemical structure of end-groups on the dispersion properties and thermo-mechanical properties of elastomeric films obtained from these dispersions was investigated systematically. Decreasing the A2:B3 ratio followed by silane functionalization and self-crosslinking resulted in stiffer films and coatings, due to higher crosslinking density. On the other hand, crosslinking of amino-functional PUs with water dispersible polyisocyanate compounds in a two-component waterborne system resulted in enhanced mechanical and thermal properties as a function of the degree of cross-linking controlled by the water dispersible polyisocyanate content. Upon the synthesis and characterization of branched, functional PU dispersions and films, pure wool and wool/polyester blend fabrics were coated with selected PU dispersions in an attempt to improve wrinkle recovery of fabrics. While half grade improvement was achieved with branched PU dispersions containing urea, silane and amino functionalities on pure wool surfaces, wrinkle resistance of wool/polyester blend fabrics was improved at least one grade with both self-crosslinking and two-component PU coatings due to better compatibility of polyester containing wool fabric with polyester-based PU backbone.
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