Preparation And Properities Study Of Vegetable Oil-based Polyurethane Modified By Hydroxylated Polyhedral Oligomeric Silsesquioxane

Polyurethane?PU?,as one of the six major synthetic materials,its production and usage is huge,large amounts of raw materials outputed from petroleum chemical industry,thus caused increased pollution and energy depletion.Based on these problems,this article chose resource-rich and renewable vegetable oils as raw materials,and the green polyurethanes were prepared through the polymerization with isophorone diisocyanate?IPDI?.To promote better application of vegetable oil-based polyurethanes in the industry,some insufficient aspects of the important molecular structures and properities of these polyurethanes should be solved first,such as weak of heat resistance,low hydrophobicity and poor tensile strength.In order to improve the comprehensive performance of pure vegetable oil-based polyurethane,silsesquioxane have been chose to prepare hybrid PU films through chemical modification due to its high temperature resistant and low surface energy.After the product structure of the preparation process been verified by characterizations,the properities of PU films have been tested.Here are the main research contents of this paper:Polyurethanes were prepared with multi-hydroxyl castor oil,heptaphenyl trihydroxyl silsesquioxane[T₇?OH?₃]was prepared and added into the polyurethanes,thus chemical modified polyurethanes were obtained.When T₇?OH?₃ addition was 0.73 wt%,T_d5?temperature of initial decomposition?for modified PU was 12 ? enhanced,compared to pure PU,when T₇?OH?₃ addition was 0.97 wt%,the tensile strength of modified PU was13.41 MPa.After modification,PU materials turned hydrophobic from hydrophilic.Nevertheless,the bad dispersion of T₇?OH?₃ made it easy to aggregate,and the tensile properties of PUs needed to be improved.Expoxy soybean oil was chosen as raw material,polyol was prepared by the ring-opening reaction together with methanol,and then was used to synthesize polyurethanes.Dihydroxyl double?decker phenylsilsesquioxane?DDSQ?Me?OH?with complete cage structure was prepared and linked to the main chain of polyurethanes by partly replacing the chain extender.When the DDSQ?Me?OH addition was 4.46 wt%,T_d5?temperature of initial decomposition?for modified material can be 291 ?,16 ? higher than the material without modification,T_g?glass transition temperature?was 12.4 ? higher,the tensile strength can be almost twice of the material without modification.As the DDSQ?Me?OH addition was 12.26 wt%,contact angle of modified material to water was up to 110.2 °,its hydrophobicity was significantly improved.Compared with the modification of T₇?OH?₃,the aggregation phenomenon was alleviated,but the tensile properties still need to be improved.Two kinds of polyols were obtained through the ring-opening reaction of expoxy soybean oil with castor oil acid and glucose,due to their high crosslinking densities,the corresponding polyurethanes were prepared respectively through one-step process,different contents of DDSQ?Me?OH were added to the reaction to modify the polyurethanes.After the research and comparison,it was found that both polyurethanes were hydrophobic as their contact angle to water were both above 90 °,and the thermal stability of soybean oil-glucose based polyurethane?SGP-PU?of all steps were better than that of soybean oil-castor oil based polyurethane?SCP-PU?.Specially,compared with SCP-PU,T_d50?the temperature of 50%weight loss?for SGP-PU was 32 ? higher,the tensile strength was more than four times higher,while the elongation at break was only 1/4 of SCP-PU.After modification,the changing rules in the properities of the two kinds of polyurethanes were basically the same.When the DDSQ?Me?OH addition in SCP-PU was 4.46 wt%,its comprehensive performance was the best,compared with the material without modification,its T_d5?temperature of initial decomposition?was 26 ? higher,T_g?the glass transition temperature?was increased by 10.8?,the tensile strength reached 17.22 MPa which was more than 3 times of that before modification,with the same time,the elongation at break was always around 700%.For SGP-PU,when DDSQ?Me?OH content was 7.87 wt%,T_d5?temperature of initial decomposition?was 29 ? improved,T_g?the glass transition temperature?increased by 11 ?,and the tensile strength reached 41.52 MPa.These two soybean oil-based polyols increased the intermolecular volume of corresponding polyurethanes from the raw material level,the aggregation of the modifier was improved,and the tensile properties of the materials were improved in two different aspects respectively.