| Polyurethane is one of the materials which are commonly used in fabric coating, however, waterproof and moisture vapor permeable polyurethane coating agent usually have defect in water vapor permeability. The study found: People’s sweat volume is 11500g/24h in the activity, which will take about 4000g/m~2 *24h of the moisture vapor permeability; in order to achieve the desired waterproof effect, it requires that the fabric hydrostatic pressure is not less than 5.58kpa.when the hydrostatic pressure of fabrics have been increased, the moisture vapor permeability of fabrics will result in a decline .Therefore, to ensure a certain hydrostatic pressure of fabrics under the premise, how to improve the moisture vapor permeability has become a focus of attention. Researchers at home and abroad according to bring the hydrophilic chain segments or groups to the molecular chain through the synthesis of waterproof and moisture vapor permeabile polyurethane coating agent, but the hydrophilic chain segments or groups will bring the introduction of waterproof performance decline.Polyester-polyurethane generally has excellent mechanical properties, film-forming properties, but poor moisture vapor permeability; and by polyethylene glycol as the hydrophilic chain segment of the polyether-based polyurethane,by which the fabrics have been coating finished have good hydrophility,high moisture permeability, but the only poor mechanical properties and waterproof propertis. At present the industrial use of polyurethane coating agent there are many grades of goods, as trade secrets and know little of its structure that limits the right polyurethane research.This insufficient as a starting point, in view of the general polyester-based polyurethane has excellent mechanical properties, good film-forming performance, but its poor moisture vapor permeability characteristics; and the fabric have good hydrophilicity and high moisture permeability, only poor mechanical properties and water resistance characteristics, which is coating finished by polyethylene glycol as the hydrophilic chain segment of the polyether-polyurethane.Thus we try to use polyester and polyether polyol mixture as a soft segment of water-based polyurethane, in order to develop a having good waterproof and moisture vapor permeability of environment-friendly water-based polyurethane coating agent.First, the reaction of isophorone diisocyanate (IPDI) and polybutylene glyool adipate(PBA,M=2000), polyethylene glycol (PEG,M= 2000), and dimethylolpropionic acid ( DMPA) create the polyurethane prepolymer with ended isocyanate groups, discussing temperature, catalyst concentration on the impact of the pre-polymerization ,and it was proposed prescriptions of synthetic polyurethane prepolymer ; then the aqueous Polyurethane coating agent was prepared by adding a certain amount of acetone into the prepolymer, cooling to 55℃, joining the chain extender 1,4-butanediol (BDO), reacting of 2h, and adding neutralizer triethylamine (TEA) for 0.5h, cooling to 30℃, last adding deionized water emulsion and stirring for 0.5h. The influence of the values of R, DMPA mass fraction, PBA / PEG molar ratio to the polyurethane emulsion stability and performance, viscosity, film mechanical properties, water absorption, as well as the waterproof property and moisture vapor permeability of the water-based polyurethane coating fabric ,filtering out the appropriate R values, DMPA mass fraction, PBA / PEG molar ratio, to be prepared by the recommendations of waterborne polyurethane coatings prescription.At last, we use the prescription of the final adoption of the recommendations of waterborne polyurethane coating agent, and change PEG molecular weight in order to explore different PEG molecular weight on properties of waterborne polyurethane emulsion stability, particle size, viscosity, film mechanical properties, water absorption, as well as the waterproof property and moisture vapor permeability of the water-based polyurethane coating fabric. Then we get two kinds of good waterproof and moisture permeability of two different PEG molecular weight of water-based polyurethane coating agent. And Fourier transform infrared spectroscopy (IR), thermal gravimetric analysis (TGA, DTG), wide-angle X diffraction analysis (WAXD) and scanning electron microscopy (SEM) are explored to characterize physical and chemical properties of two kinds of thin film coatings prepared by the 2 kinds of polyurethane which have been said above.On this basis, we choose the best results of water-based waterproof and moisture vapor permeable polyurethane coating agent which have been used in polyester fabric coating finishing, research the impact of waterproof properties and moisture vapor permeabilities, and mechanical properties amount of different coatings and curing temperature on the coated fabrics. Research shows that: In the curing temperature of 160℃, the coating when the amount of 23g/m~2 coated polyester fabric ,its water vapor permeability can be up to 4810.3 g/m~2 * 24h, hydrostatic pressure can reach to 6.74kpa,thus we can get a good waterproof property and moisture vapor permeability . At the same time, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA, DTG) analysis of test results show that: the surface of the polyester fabric which has been coating finished by the polyuranthane in the experiment has formed a continuous film, and has little change in thermal performance. |
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