Preparation And Properties Of Vegetable Oil-based Waterborne Polyurethane

Waterborne polyurethane(WPU)not only inherits the excellent physical and chemical properties of traditional polyurethane(PU),but also has been widely used as the non-toxic,safe and reliable multifunctional material in many fields,such as coatings,leather,ink and adhesives.However,in order to achieve the performance requirements of industrial standards,most of the raw materials synthesized in the water-based polyurethane products are petroleum-based polyols,which will aggravate the consumption of petroleum resources when it is used excessively,and the non-degradability of the materials will also bring some pollution to the environment.In this thesis,the natural renewable energy-vegetable oils are used as raw material,different groups(epoxy groups and hydroxyl)of vegetable oil-base structure were functioned to prepare vegetable oil-based polyols,which was used to synthesize the vegetable oil-base waterborne polyurethane instead of petroleum-based polyols,so as to get the purpose of energy conservation and environmental protection.The main contents of this paper are as follows:Castor oil(CO)as raw material,was reacted with maleic anhydride by the esterification reaction to prepare castor oil-based emulsifier(MCO),then pentaerythritol(PE)was used as small molecular crosslinking agent to synthesize a series of free DMPA(2,2-dihydroxymethylpropionic acid),solvent-free bio-based emulsifier waterborne polyurethane(MWPU).The molecular structure of MCO was characterized by FT-IR and ¹H-NMR,and the effect of PE content on the properties of waterborne polyurethane was investigated.When the addition of PE increased from 1%to 4%,the tensile strength of MWPU film increased from2.83 MPa to 22.45 MPa,and the glass transition temperature(T_g)was improved from 22.53?to 77.48?.However,when the PE content was 4%,the average particle size of MWPU emulsion increased sharply to 207.5 nm.The storage stability of the emulsion decreased,which was easy to generate sedimentation.In order to avoid the use of small molecule crosslinking agent to improve the polyurethane film properties,the epoxidized soybean oil(ESO)was reacted with 1,3-propylene glycol,trimethylolpropane and xylitol,respectively by the ring opening reaction to prepare three kinds of different hydroxyl value of polyols,which reacted with IPDI and DMPA to synthesize three kinds of soybean oil-based waterborne polyurethane.The effect of hydroxyl value of polyols on the properties of polyurethane films was studied.With the increase of hydroxyl values of the polyol,the tensile strength of the polyurethane film increased from 2.61 MPa to 24.35 MPa,the T_g was enhanced from 30.01?to 88.28?,and the initial decomposition temperature(T₅)decreased from 207?to 159?.In addition,compared with MWPU emulsion,the maximum average particle size of soybean oil-based waterborne polyurethane emulsion was 171.1 nm.The storage stability of the emulsion was improved.In order to improve the thermal performance of polyurethane film,the ESO and ricinoleic acid were used to prepare polyols under the condition of without solvent and catalyst.The R value(the mole ratio of-NCO/-OH)in the process of the synthesis of WPU was adjusted to prepare the four different R value of soybean oil-based waterborne polyurethane(SWPU),and the relation between R value and the performance of the SWPU membrane was studied.The results showed that with the increase of R value,the mechanical properties,thermal properties and hydrophobicity of SWPU films were strengthened.When R value increased from 1.1 to 1.4,the tensile strength of SWPU film increased from 10.02 MPa to 27.32 MPa,T_g of hard segment increased from 68?to 130?,and T₅ was enhanced from 201?to 246?.Compared with soybean oil-based waterborne polyurethane,the thermal stability and T_g of SWPU film was improved.In order to endow the waterborne polyurethane with more functionality and solve the single performance problem of the vegetable oil-based waterborne polyurethane prepared in the previous work,a variety of self-repaired vegetable oil-based waterborne polyurethanes were synthesized.Firstly,soybean oil-based emulsifier(GA-ESO)was synthesized by epoxy soybean oil and glutaric acid without solvent and catalyst.Then,two DA diols(BMI-FA and ATOM-FA)were prepared by the DA reaction between N,N-(4,4-methyldiphenyl)bismaleimide(BMI),4-maleimide phenol(ATOM)and furfuryl alcohol(FA),respectively.Finally,GA-ESO and DA diols used as the raw material were reacted with IPDI to synthesize a series of soybean oil-based waterborne polyurethane with self-healing behavior.The effects of DA diol on the properties of polyurethane films and the self-healing process and mechanism of polyurethane membrane were investigated.The results showed that after the addition of DA diol,the particle size of polyurethane emulsion increased from 28.8 nm to 85.3 nm,the tensile strength was improved from 0.3 MPa to 12.6 MPa,and the water contact angle was enhanced from 68.5°to 84.2°.In addition,the self-healing test showed that the polyurethane film with the addition of DA diol had self-repaired behavior at high temperature,and the highest self-healing efficiency could reach 100%.