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The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites. [ABSTRACT FROM AUTHOR]

ABSTRACT: Environmentally friendly waterborne polyurethanes (WPUs) modified by moisture‐curable alkoxysilane have been much studied nowadays. In this work, a new diol‐bearing pendant urea‐propyl trimethoxysilane (APD‐Si) was synthesized and used as the chain extender in the preparation of a silicone‐modified WPU dispersion. Both the formation of hybrid networks based on the condensation of trimethoxysilane groups and the enhanced microphase separation of the hard and soft segments have been found to rely on the strong hydrogen‐bonding capability of the urea‐containing spacers, which link the alkoxysilane groups with the backbone of WPU. Because of the synergism of chemically bonded silsesquioxane and physically hydrogen bonded hard domains serving as crosslinking points, the mechanical properties of the hybrid films of WPU are improved, especially the modulus and yield strength. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46628. [ABSTRACT FROM AUTHOR]

Inspired by the growing demand for smart and environmentally friendly polymer materials, we employed 2,2′-disulfanediyldianiline (22DTDA) as a chain extender to synthesize a waterborne polyurethane (WPUR). Due to the ortho-substituted structure of the aromatic disulfide, the urea moieties formed a unique microphase structure in the WPUR, its mechanical strength was enhanced more 180 times relative to that of the material prepared without 22DTDA, and excellent self-healing abilities at body temperature in air or under ultrasound in water were obtained. If the self-healing process was carried out at 37 °C, 50 °C or under ultrasound, the ultimate tensile strength and elongation at break of the healed film could reach 13.8 MPa and 1150%, 15.4 MPa and 1215%, or 16 MPa and 1056%, respectively. Moreover, the WPUR films could be re-healed at the same fracture location over three cutting–healing cycles, and the recovery rates of the tensile strength and elongation at break remained almost constant throughout these cycles. [ABSTRACT FROM AUTHOR]

Proper building of polymer/polysilsequioxane composite is determined by deep-rooted structural variables. This work focuses on the fabrication of silane-grafted waterborne polyurethane (DWPU)/polyphenylsilsequioxanes (PPSQ) composites by blending and in-situ methods, respectively. By using blending method, PPSQ nanoparticle latexes were dispersed in DWPU. By using in-situ method, as the precursor of PPSQ, phenyltrimethoxysilane was mixed in DWPU, and PPSQ was expected to be generated via in-situ sol-gel reaction during film formation. We systematically investigated the influences of PPSQ and its incorporation method on the phase separation of films. The competition between a heterophase-triggered phase separation and a silane-based crosslinking was found during film formation. The intrinsically local ordering permutation of PU segments was interrupted more or less with PPSQ. Both surface composition and morphology were altered in correspondence to the different addition amount of PPSQ. Furthermore, optical, mechanical, and thermal resistances of composite films were also investigated for potential applications as coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • The film-formation driven construction of dual dynamic networks by waterborne polyurethane. • The good balance on the comprehensive performances, their recovery and the environment. • The distinguish on the dynamic responses of the H-bonding and chemical bonded networks. • The all commercial monomers and industrializable preparation. The implementation of the dynamic crosslinking network toward the commodity polymers such as polyurethane has been much highlighted for resource conservation and environmental protection. This work demonstrates a feasible dual dynamic network (DDN) construction of waterborne polyurethane (WPU) by using a biobased trifunctional ketose, 1,3-dihydroxyacetone (DHA) serving as the chain extender. The WPU dispersion was compatible well with the post-added adipic acid hydrazide (ADH) as the water soluble crosslinking agent. When the one-pot system of WPU-ADH was cast into films, covalent adaptive network (CAN) was formed through the condensation of ketohydrazine and carbonyl groups driven by the evaporation of water. The produced acylhydrazone groups would also contribute to the strengthen on the H-bonding crosslinking network. The synergism of the two sets of the networks provided not only the improved mechanical performances, but their > 95% recovery efficiencies on the 28 MPa of strength and 750% fracture elongation in the self-healing, reprocessing and welding tests under moderate heating. In addition, the WPU exhibited as an effective adhesive to metal with the adhesive strength sustained after four times of deconstruction-rebonding circles. The all commercially available components, feasible preparation together with the excellent and recoverable performances suggest an industrializable resolution for the sustainability of environmental friendly WPU materials. [ABSTRACT FROM AUTHOR]