Reaction molding

Due to the exothermic nature of the reaction and the phase separation which occurs, temperature and conversion (and MWD and sequence distribution) can only be assigned local, not global, values in polyurethane reaction molding. 

In reaction molding, the reactive mixture is initially poured or injected into the mold bottom as a pool. As the mold rotates, the mixture moves along the mold surface and becomes uniformly distributed on the wall in the ideal case. For example, let us suppose that the process begins from point M in Fig. 4.23 at a fixed value of to and mean film thickness b. As the viscosity increases as... 

Fig. 13.46 Temperature distribution in a reacting polyurethane slab isothermal-wall simulations. Dotted line denotes the adiabatic temperature rise and x s indicate gel points, k = 1, n — 1, AT — 0.423, and B = 18.7, 4>gel = 0.707. [Reprinted by permission from E. Broyer and C. W. Macosko, Heat Transfer and Curing in Polymer Reaction Molding, AICHE J. 22, 268 (1976).]...

E. Broyer and C. W. Macosko, Heat Transfer and Curing in Polymer Reaction Molding, AIChE J., 22, 268 (1976). 

Nine compositions with the diamond concentration of 3, 5, 7, 9, 10, 12, 15, 20, 25 mass % were mixed with the charge Ti-C-Mo to produce multi-layered semi-products. The ready mixtures were placed layer-by-layer into a pressform in the following order diamondless layer weighing 25,5 g 3 mass % diamond layer, weighing 10 g 5 % layer -10 g 7 % layer - 10 g 9 % layer - 9,9 g 12 % layer - 9,9 g. After densification pellets were obtained 48 mm in diameter with the thickness of the layers 5.0, 2.0, 2.0, 2.0, 2.0, 2.0 mm correspondently. Multilayered pellets with the diamond concentration from layer to layer as much as 0, 5, 10, 15, 20, 25 % mass were prepared similarly. The final pellet was placed into a reactional mold. An SHS reaction was initiated from the lateral face of the cylindrical pellet by a tungsten spiral. After accomplishment of the combustion reaction and propagation of the combustion synthesis wave, the hot SHS-products were compacted in a hydraulic press at P > 400 MPa for no more than 10 s. The time of exposure to pressure was chosen dependent on the combustion temperature and reology of the products, e.g., on their plasticity and the amount of the liquid phase formed. Usually this time is 0.5 -4 2 sec. SHS-products were cooled at the room temperature. 

To produce FGM with cobalt varied concentration a mixture was prepared of the following composition 64 % Ti -l- 16 % C -H 20 % Co. The mixture weighing 56 g was placed into a mold. Then cobalt powder was added. Three pellets were obtained with the diameter of 48 mm with various mass ratio of the mixture and cobalt layers 13/56 (0.23) 20/56 (0.36) 28/56 (0.5) correspondently. The relative density of the mixture layer was 0.58 of cobalt layer - 0.65. The SHS-densification was carried out in the reactional mold with the values of the delay time ti = 2 4- 5 sec pressure Pk = 30 MPa and time of exposure t2= 5 4-10 sec. 

Reaction molding method has given composite impact and wear resistant reinforced gradient polymeric materials, based on polyisocyanurates (PIC) and polyurethanes (PU). 

This work is targeted at the study of impact resistance and wearability in gradient polymeric materials based on PU and PIC composites, produced by reaction molding method, with respect to the composition. Two types of composite gradient polymeric materials the... 

Much less work has been done on relating rheological changes to structural changes during radical chain growth polymerization. Yet radical chain systems are widely used In reinforced plastics reaction molding. These systems are well suited for this use. 

Low density reinforced reaction molded polyurethane (LD-RRIM) is claimed to simplify production of interior automobile components. 

Rotational Molding Pultrusion Thermolorming Calendering Compression Molding Reaction Molding Transfer Molding... 

Molding. In molding liquid materials are poured into a mold and there hardened, i.e., polycondensed or polymerized (Figure 36-1). Phenol and epoxy resins are processed in this manner, as are monomers such as methyl methacrylate, styrene, vinyl carbazole, and caprolactam (reaction molding). 

Eskevez, S. R. and Macosko, J. M. (1980) Heat transfer in polymer reaction molding. Inti J. Heat Mass Transfer, 23, 1479-92. 

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