The effect of solid content on the properties of polycarbonate-based waterborne polyurethane dispersions

Keywords: polyurethane; water-based; thermal analysis; shear stretching
Background: Water-based polyurethane dispersions (PUDs) are becoming increasingly of concern to researchers in the adhesive and coatings industry due to environmental, health and safety concerns. In fact, puDs systems were developed primarily to control the emission of volatile organic compounds into the atmosphere, and of course because of their superior performance compared to their solvent-based polymers. Polycarbonate glycol (PCD) has been widely used in the manufacture of materials with good

. Polyurethanes made from polycarbonate glycol have better hydrolytic resistance, excellent aging and oil resistance, better mechanical properties, better low temperature performance, and improved weather resistance to the resulting polyurethanes compared to the use of polyester polyols.
the effect of solid content on the properties of water-based polyurethane dispersions is less studied. Jung is used to synthesize water-based polyurethane dispersions with different solid contents (30%-50%). It was found that with the increase of solid content in polyurethane dispersion, the particle size increased, and its viscosity was also affected by solid content, but the solid content had no effect on the dynamic performance and dynamic dynamic performance of polyurethane coating film. Madbouly and other water-based polyurethane dispersions made from polyester polyols and isofone diocyanates studied the effect of solid content (24%-46%) on performance. It was found that the viscosity of the dispersion increased with the increase of the solid content, and the solid content had a great influence on the fluid performance of the polyurethane coating film, and the solid content of the polyurethane dispersion also affected the shape of its resin network structure.
taking into account the shortcomings of existing literature studies and the contradictions of previous studies, several water-based polyurethane dispersions with different solid contents have been synthesized using polycarbonate as raw materials, such as García-Pacios of the University of Licante in Spain. The effects of solid content on the relationship between polyurethane structural properties were studied, and the results were published in International Journal of Adhesion and Adhesives.
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1. The synthesis of water-based polyurethane
four water-based polyurethane dispersions were prepared according to the NCO/OH ratio of 1.5. The solid content of the dispersion was between 37% and 44%. The DEG content is set at 0.5% and the DMPA content is set at 5% (both are based on the weight of the prejudging).
the large molecule ddiol, IPDI, DEG and DMPA into the glass jacket reactor equipped with a mechanical agitator, and the reaction is carried out under nitrogen at 80 degrees C. When the residual NCO value reaches the theoretical value (tested by toluene-dythropamine), control the speed of 450 rpm and dissolve the pre-concentration in acetone at 45-55 degrees C until it is completely dissolved. Then use triethylamine (TEA) to medium the acid in DMPA.
because of the priority reactive nature of NCO group and amine, amine-based chaining agents are added first to avoid the reaction of unresponsive NCO groups with water. Finally, the polymer is dispersed in water at 900 rpm and the residual acetone is removed by steaming.
2. Synthesis of water-based polyurethane film
some properties are measured using polyurethane film, the solid film is by placing about 100 cm3 polyurethane dispersion in a Teflon mold, at room temperature for 72 hours, allowing the solvent to evaporate slowly. Then, dry the film at 40 degrees C for 8 hours to allow the water to be completely removed. The resulting film thickness is about 0.7 to 0.9mm.
the name of the polyurethane, as shown in Table 1, it consists of a capital letter PU, followed by a solid content value.
and performance testing, the authors
series of symptoms and performance tests on the synthetic materials.
conclusion:
increase in solid content (or soft segment content) in water-based polyurethane results in reduced particle size distribution and particle multi-dispersion of polyurethane dispersion. On the other hand, as the solid content increases, the viscosity of PUDs increases, thus reducing the flow of particles, thus reducing the probability of particle-particle interaction.
solid content affects the relative strength of the infrared band of polyurethane, showing differences in the content of the hard segment. On the other hand, thermal weight analysis can distinguish the segmented structure of polyurethane. The increase in solid content increases the weight loss corresponding to the degradation of the soft segment. Therefore, thermal stability increases with the increase of polyurethane solid content.
the solid content of the polyurethane reduces the glass transition temperature, indicating a higher degree of phase separation of polyurethane. On the other hand, due to the increase in the content of the soft segment, the intersection between the energy storage module and the loss mould moves in the direction of the lower module. Finally, the increase in solid content does not affect the bonding strength under peeling stress. However, due to the reduction of the hard segment content and the increase of solid content, the shear resistance strength of polyurethane is reduced and cohesion damage occurs.
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Yin X, Dong C, Chai C, et al. Thermostability and flame retardance of green functional two-component waterborne polyurethane coatings with nanoparticles. Progress in Organic Coatings, 2018, 122:119-128.