The formulation for slow rebound foam is broadly similar to that for conventional foam, with key differences primarily in the main ingredient, polyether. Some minor ingredients can be substituted, but to ensure high-quality product outcomes, careful selection of these additives is essential.
- Selection of Amines
The standard amine for slow rebound foam is Dabco33-LV, produced by Air Products. The typical dosage ranges from 0.3 to 0.8 parts per hundred parts of polyether. This product comprises 33% triethylenediamine and 67% di(propylene glycol) (DPG). The preference for this amine is due to its solvent, DPG, which has the largest molecular weight and lowest hydroxyl value among small alcohols like propylene glycol, diethylene glycol, ethylene glycol, and 1,4-butanediol. This characteristic reduces TDI consumption and minimizes the risk of closed-cell formation. - Choice of Tin Catalysts
In traditional foam production, stannous octoate (T-9) is commonly used; however, dibutyltin dilaurate (D22, T-12, also known as K-19 domestically) is recommended for slow rebound foams. T-9 is advantageous for low to medium density foams but may not provide sufficient post-cure properties for higher densities. Additionally, T-9 can hydrolyze, particularly in slower-reacting foams like slow rebound types, which can affect the curing process. Dibutyltin dilaurate, in contrast, offers stable initiation, gelation, and curing, with improved post-cure performance.
For issues with tensile strength, dibutyltin dilaurate has shown positive effects. T-9 is used at 0.1-0.4 parts, while dibutyltin dilaurate can be used at lower levels of 0.03-0.05 parts. For continuous production lines, the amount can be further reduced to 0.001-0.01 parts. For export orders with restrictions on tin catalysts, bismuth neodecanoate can be an effective alternative.
- Silicone Oil Selection
B8002 is a typical silicone oil used for slow rebound foam, with usage ranging from 0.5 to 2 parts. It’s more commonly used in low-density foams and hand-mixed applications. In recent years, domestic suppliers have developed various silicone oils specifically for slow rebound applications, with good performance. When using L-580, which is more active, the amount of silicone oil should be reduced. - Use of Pigments
The usage of pigments generally follows the same principles as for conventional foam. However, special care is required when using black pigments, as carbon black can interfere with component compatibility and catalyst efficiency due to its hydrophobic nature. This can lead to issues like cracking in black foams, necessitating adjustments in catalyst dosage.
These insights are based on practical experience and are shared for reference, inviting feedback and corrections from industry peers.
