Abstract
Waterborne polyurethane (WPU) is a versatile and environment-friendly material with growing applications in both industry and academia. Silk fibroin (SF) is an attractive material known for its structural, biological and hemocompatible properties. The SF reinforced waterborne polyurethane (WPU) is a promising scaffold material for tissue engineering applications. In this work, we report synthesis and characterization of a novel nanocomposite using SF reinforced WPU. The rheological behaviors of WPU and WPU-SF dispersions with different solid contents were investigated with steady shear and dynamic oscillatory tests to evaluate the formation of the cross-linked gel structure. The average particle size and the zeta potential of WPU-SF dispersions with different SF content were examined at 25 °C to investigate the interaction between SF and WPU. FTIR, SEM, TEM and tensile testing were performed to study the effects of SF content on the structural morphology and mechanical properties of the resultant composite films. Experimental results revealed formation of gel network in the WPU dispersions at solid contents more than 17 wt %. The conjugate reaction between the WPU and SF as well as the hydrogen bond between them helped in dispersing the SF powder into the WPU matrix as small aggregates. Addition of SF to the WPU also improved the Young’s modulus from 0.30 to 3.91 MPa, tensile strength from 0.56 to 8.94 MPa, and elongation at break from 1067% to 2480%, as SF was increased up to 5 wt %. Thus, significant strengthening and toughening can be achieved by introducing SF powder into the WPU formulations.
Highlights
Waterborne polyurethane (WPU) is a widely used versatile class of material for applications in coatings, adhesives, sealants, elastomers, porous-foams, biomaterials and many more [1,2,3,4].Polyurethane has been used as scaffold material in tissue engineering, and as a career material in drug delivery as well [5]
By in situ adding Silk fibroin (SF) powder during the synthesis processing of WPU prepolymer, the SF powder can covalently bond to the WPU molecular chains and the hydrogen bonding formed between SF and WPU17
The Young’s modulus, the tensile strength, and the elongation at break of the WPU17-SF5 film were much higher compared to those of the WPU17-SF5a film. This indicates that a strong interaction such as conjugated reaction or hydrogen bond between SF and prepolyurethane if SF is added during the WPU synthesis process
Summary
Waterborne polyurethane (WPU) is a widely used versatile class of material for applications in coatings, adhesives, sealants, elastomers, porous-foams, biomaterials and many more [1,2,3,4]. Polymers 2016, 8, 94 dispersions and the mechanical properties [9,10,11] of WPU films are of paramount importance for controlling their flow during applications in coating of textile fibers, sealants, and glass fiber sizing, as well as controlling the mechanical properties of solids prepared from these dispersions [12]. The dispersions of WPU and WPU-SF with various solid contents were synthesized for preparing the novel composite WPU-SF materials with enhanced physical and biological properties. The resultant WPU-SF dispersions were used to prepare composite films, and the effect of SF content on the structure, morphology, and mechanical properties were discussed
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