When designing and manufacturing polyurea, we must consider potential issues that may arise during construction operations, such as how to minimize the product's potential harm to us. During construction, it's challenging to avoid determining whether the construction products have any impact on us. Therefore, our focus is to first reduce its toxicity. Below is an introduction to the importance of polyurea prepolymer by the editor.
The A component should be a polyisocyanate prepolymer rather than a monomer, which is absolutely necessary under polyurea spray conditions. The purpose of the polyisocyanate component prepolymerization has at least three significant aspects: Firstly, it reduces the toxicity of the isocyanate to make the polyurea spray truly safe and environmentally friendly, becoming an actual eco-friendly product; secondly, it enhances product stability while ensuring the prepolymer has sufficient functionality and reactivity—unprepolymerized diphenyl methane diisocyanate—MDI can gradually dimerize at room temperature without any catalyst, leading to gelation; and thirdly, it achieves a structure similar to that of polyether, which is conducive to improving the miscibility of the A and R components.
In order to reduce toxicity, even in the painting process of polyurethane, not only is the polyisocyanate required to be pre-polymerized, but the pre-polymer must also be thoroughly purified to ensure that the diisocyanate monomer content is below 0.7% (less than 0.5% after adding solvent). Moreover, the application of polyurea spraying requires high-pressure counter-mixing under high temperatures to achieve complete atomization, which is a necessary condition. It can be imagined that the A component of polyurea not only needs to be pre-polymerized, but the diisocyanate monomer content in the pre-polymer should be subject to even stricter limitations.
Additionally, the isocyanate prepolymer is beneficial for improving the branching tendency during the film-forming process, increasing the molecular weight between cross-linking points, adjusting the cross-linking density, and ensuring the film's high elasticity and high crack resistance, among other mechanical and physical properties.
It appears that the pre-polymerization reaction of polyurea has a significant impact on us. Firstly, the reduced toxicity of polyurea products is a positive development. Additionally, it's beneficial for our construction workers during the construction process. The impact on their health has also been greatly minimized. The editor believes that in the future, polyurea will better adapt to our needs.
