| Polyurethane (PU) is the general term of the molecular chain polymers containing carbamate structure. Its structure is composed of soft and hard segments, adjust the categories and the proportion of soft and hard segments can synthesize polyurethane materials to meet specific application needs,so it has a wide range of applications and research value.People gradually increase the awareness of environmental protection,as well as the establishment of community environmental regulations become more standardized, environmentally friendly materials came into be appeared.Waterborne polyurethane (WPU) as water as dispersion medium, a non-toxic and difficult to combustion, the advantages of environmentally friendly and so on, is the future of the development of green material,widely used in textile, leather, wood, construction, automotive, paper, electronics, and other fields.However, because of single water-based polyurethane’s inherent defects, such as water resistance, solvent resistance, poor weather resistance, low molecular weight, mechanical properties, low solid content, initial adhesion is poor,etc,its promotion and application has been limittied. Therefore, waterborne polyurethane modified has to be become a research focus of the university researchers and corporate R&D department.Natural vegetable oils are types of natural organic compounds, defined as a mixture of mixed fatty acid triglycerides by the chemical concept. Generally, natural oil, its fractions other than95%for triglycerides, there is little content and composition of complex non-composition of the triglycerides. Play a leading role fatty acid proportion of the triglycerides molecules, so the impact of its chemical and physical properties. As a modifier for waterborne polyurethane modified on the basis of the green, effectively improve the overall performance of waterborne polyurethane, expanding its application areas. In this thesis,in base of reading a lot of literature,linseed oil as a modifier,we mainly do the work and research of the following three areas:1.Modification of the linseed oilFor the structure of the linseed oil itself dose not contain hydroxyl,can not to be a modifier of waterborne polyurethane directly,so we should do some hydroxyl modification on pure linseed oil.For which,this section modified linseed oil by two processeson,which are alcoholysis and aminolysis methods,to discuss the ammonolysis and alcoholysis agent and amount of the catalyst,and also explore the aminolysis and alcoholysis process parameters and formulation design,order to get the best response and modify effect,and the products were characterized and tested,the results show that:(1)For linseed oil, a more reasonable alcoholysis conditions is LiOH as catalyst for3h at230℃;Aminolysis condition is using diethanolamine as aminolysis agent, NaOCH2CH3as catalyst,add the amount of0.5%(mass fraction),react about2h under90℃.(2)The color of linseed oil modified in alcoholysis methods is deeper than the color of linseed oil modified in ammonolysis methods,and also has well storage stability. IR and NMR characterization proved alcoholysis and aminolysis methods have both access hydroxy in the triglyceride structure successful.(3)Theoretically,in the condition of determining the amount of linseed oil triglycerides,the hydroxyl rate is the same by both alcoholysis and aminolysis methods.2.Synthesis and properties of linseed oil modified waterborne polyurethaneOn the basis of the previous chapter,using the hydroxylation of linseed oil modified waterborne polyurethane,discussed either modification process to waterborne polyurethane by linseed oil in alcoholysis and aminolysis methods. Synthesized a series of stable linseed oil modified waterborne polyurethane emulsion (water-based urethane oil).By characterized and tested for it and its film, the affect of amount of linseed addition to the water-based urethane oil performance,the crosslinker and other factors were discussed,the results show that: (1)For alcoholysis of linseed oil modified polyurethane,the temperature controlled is required to be higher,and for aminolysis of linseed,because of its much more activities,to the low temperature controlled,it is also recommended to use the "two-step" method in adding.Either additional crosslinker and after chain extender may reduse the stability of water-based urethane oil obtained.(2)Water absorption and surface water contact angle measurements indicated that waterborne polyurethane’s water resistance has been enhanced significantly modified by linseed oil.TG tests proved its TGA onset temperature increased by about100℃than the original.(3)Mechanical properties of water-based urethane oil film gradually increased with the increase in the amount of linseed oil,but when addition is more than25%,it appeared a hard and brittle characteristics.For the oxygenation of the unsaturated double bonds in the film later,product coating hardness is significantly enhanced.3.Synthesis and properties of linseed oil based waterborne polyurethane-polyacrylate composite emulsionIn recent years,acrylic modified waterborne polyurethane waterborne polyurethane has become research hotspot.In this section,we use the unsaturated double bonds contained in the pre-synthesis of linseed oil based waterborne polyurethane, its as seed emulsion,to start acrylic emulsion polymerization, Synthesized core-shell structure of the linseed oilbased waterborne polyurethane-polyacrylate composite emulsion.From multiple modified,product performance has been further enhanced, characterization and test results show that:(1)FT-IR and TEM proved that the core-shell structure of the linseed oilbased waterborne polyurethane-polyacrylate composite emulsion was synthesized.(2)When linseed oil ratio of20%and acrylate ratio below50%,the emulsion was stable.(3)Water absorption,mechanical properties,thermal properties and other tests confirmed that the linseed oil based waterborne polyurethane-polyacrylate film has better water resistance and heat resisitance,the mechanical properties has not change obviously. |
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