Selection of raw materials for polyurethane sheet
Selection of raw materials for polyurethane sheet:
The isocyanate (PAPI) component is sourced from Yantai Wanhua PM-200, and this component remains constant throughout the process. As the amount of PAPI increases, the degree of cross-linking in the foam rises, which enhances both strength and rigidity. However, an excessive amount of PAPI can make the foam brittle, leading to cracks in the core material.
Choosing the right polyether polyol is crucial. It is a fundamental raw material in rigid polyurethane foam and significantly affects the physical properties, dimensional stability, and foaming process. Once the polyether model is determined based on factors like the initiator type, hydroxyl value, and viscosity, it's important to select a low potassium ion content to ensure better performance.
It's recommended that the foam stabilizer has strong emulsification properties. This helps control cell size, maintain cell stability, and prevent collapse. Silicone-based foam stabilizers are particularly effective, and their dosage can be adjusted between 1.5% and 2.5% by weight, directly influencing the density and strength of the rigid polyurethane foam.
The blowing agent not only helps adjust the density and performance of the final product but also reduces the viscosity of the polyether blend, improving the foaming process. It enhances foam fluidity and makes molding easier. Considering environmental sustainability, the use of CFCs as blowing agents is now heavily restricted due to their harmful impact on the ozone layer.
Catalysts play a key role in controlling the reaction speed. A delayed catalytic system allows for a longer interval between whitening and gel times, improving the flowability of the foaming system and making it more suitable for production. The uniformity of the foam inside the cavity, the level of expansion, and the closed-cell structure all greatly affect the panel’s insulation performance. These factors are closely related to how well the foam adheres to the cavity walls and its dimensional stability.
Flame retardants enhance the fire resistance of the foam. However, they can negatively affect the foam during the foaming process. It’s essential to balance the flame-retardant effect with the foam’s overall performance and dimensional stability to ensure long-term usability.
Set Adjusting Additive and Admixture
For cement based or gypsum based product like mortar or concrete, set adjustment is so necessary, which is important for ensure the application time and early strength development. There are many types of product to change the initial and final setting time. In some case, Set Retarder is adopted to extend the setting for cement or gypsum including tartaric acid, citric acid, sodium gluconate etc. In other case, Set Accelerator is also critical to shorten the setting time and improve the early strength, such as lithium carbonate, lithium sulphate and calcium formate etc. CSA Cement, as fast setting cement, works as fast-setting admixture, which give excellent instant setting effect when used alone or combined with ordinary portland cement. Furthermore, in some fast-setting binder system, retarder and accelerator have to be added together to fine tune the hydration process.
Set retarder,cement retarder,gypsum retarder,set accelerator,early strength agent,tartaric acid,set adjusting admixture
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