Synthesis and properties of biodegradable waterborne polyurethane modified as castor oil

A series of biodegradable waterborne polyurethane (WPU) based on polycaprolactone diol and castor oil is synthesized through the process of the polyaddition reaction. Biodegradable WPUs are designed by using polycaprolactone diol and 4,4′- methylene dicyclohexyl diisocyanate as the main domain of urethane, dimethylol butanoic acid as the anionic internal emulsifier and trimethylamine as the neutralizing agent. Castor oil is introduced as a key component to induce or maximize the biodegradability and biocompatibility of a WPU series. The biodegradable ability of WPUs are changed by the control of Castor oil content and molecular weight (MW). The biodegradation of a WPU series prepared in this study is analyzed in field emission scanning electron microscopy through visual modifications in bio-enzyme evaluation. The effects of Castor oil and MW on the physical properties are evaluated using gel permeation chromatography (GPC), universal test machine (UTM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FE-SEM). The WPU with high level of MW and Castor oil shows enough enhancement in tensile strength and Young's modulus, ranging from 12.28 to 23.47 MPa and from 0.04 to 0.137 MPa, respectively. SEM results point to a significant microphase biodegradation of a WPU series by bio-enzymes. It can be an environmental-friendly candidate to apply various biofields.