Nucleation foam formulation

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. 

The endothermic nucleating foaming agent uses hydrocerol agents reacting with baking soda and citric acid to release carbon dioxide with limited moisture. It is formulated in a PE-based master batch, and added at 1.5 to 2% levels. One grade... 

Surfactants are necessary in the RIM urethane elastomer process where some degree of foaming is desired in the final moulding. They are added to the foam formulation to decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic medium, aid in nucleation, stabilize the foam and regulate cell structure. The choice of surfactant depends upon the type of foam preparation (polyester, prepolymer or one-shot polyether). Both ionic and non-ionic surface-active agents have been employed. 

In a simple foam formulation for a water-blown foam of polyol, diisocyanate, water, silicone surfactant, and tertiary-amine and stannous octoate catalyst, the first reaction to occur is water with isocyanate to liberate carbon dioxide, which nucleates to form gas cells and begins foam expansion. This reaction of water with isocyanate is the most energetic reaction that will occur, and it has about twice the heat of rection of either amine with isocyanate or hydroxyl with isocyanate. 

The Kleber-Colombes rigid PVC foam (253,254) is produced by compression mol ding vinyl plastisol to react and gel the compound, followed by steam expansion. The process involves mixing, mol ding, and expansion. The formulation consists of PVC, isocyanate, vinyl monomers such as styrene, anhydrides such as maleic anhydride, polymerization initiators, FC-11, and nucleators. The ingredients are mixed in a Wemer-Pfleiderer or a Baker Perkins... 

The surface active agent is an essential ingredient in formulations. It facilitates the dispersion of water (see below) in the hydrophobic resin by decreasing the surface tension of the system. In addition, it also aids nucleation, stabilizes the foam, and regulates the cell size and uniformity. A wide range of surfactants, both ionic and nonionic, have heen used at various times. Commonly used among them are the water-soluhle polyether siloxanes. 

Microcell 545 and Microcell 546 are chemical foaming agents with endothermic reaction kinetics. At low doses the formulations produce very fine cell structures. They can also be used as nucleating agents for directly gassed systems or in masterbatch formulations. ... 

PLA and PBAT are premixed as pre-foaming master batches. Maleic anhydride and LI01 are then added to PLA/PBAT blend pre-foaming master batches as a multi-compatibilizer. PLA/PBAT foams are prepared by reactive extrusion. AC is added as blowing agent and nano-Si02 as nucleation agents. The formulations for all experiments are shown in Table 5.11. 

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