Molded foams

Foam-injection molding Foam plastic sheathing Foam products Foam regulators Foam rheology... 

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

For passenger car seating about 90% is made by the molded foam process. The transportation market has expedenced a decline since 1979 due to decreased automotive production and also because U.S. cars have been downsized, resulting in the use of less polyurethane foam per car. 

The products from the continuous process (buns) are cut to shape for the particular appflcation, while the molded foams ate formed to shape during the mol ding process. The density of the continuous buns is traditionally between 16-32 kg/m (1-2 Ibs/ft ). Molded foams have densities greater than 32 kg/m. Flexible foams find appHcafions as automotive cushions, carpet underlay, furniture, seating, and bedding. 

Monofunctional, cyclohexylamine is used as a polyamide polymerization chain terminator to control polymer molecular weight. 3,3,5-Trimethylcyclohexylamines ate usehil fuel additives, corrosion inhibitors, and biocides (50). Dicyclohexylamine has direct uses as a solvent for cephalosporin antibiotic production, as a corrosion inhibitor, and as a fuel oil additive, in addition to serving as an organic intermediate. Cycloahphatic tertiary amines are used as urethane catalysts (72). Dimethylcyclohexylarnine (DMCHA) is marketed by Air Products as POLYCAT 8 for pour-in-place rigid insulating foam. Methyldicyclohexylamine is POLYCAT 12 used for flexible slabstock and molded foam. DM CHA is also sold as a fuel oil additive, which acts as an antioxidant. StericaHy hindered secondary cycloahphatic amines, specifically dicyclohexylamine, effectively catalyze polycarbonate polymerization (73). 

Property Styrofoam/ extmded Bead, board-molded Foam sheet ASTM... 

Hydroxy group containing tertiary amines are also used because they become incorporated into the polymer stmcture, which eliminates odor formation ia the foam (3). Delayed-action or heat-activated catalysts are of particular interest ia molded foam appHcations. These catalysts show low activity at room temperature but become active when the exotherm builds up. In addition to the phenol salt of DBU (4), benzoic acid salts of Dabco are also used (5). 

Semiflexible molded polyurethane foams are used in other automotive appHcations, such as instmment panels, dashboards, arm rests, head rests, door liners, and vibrational control devices. An important property of semiflexible foam is low resiHency and low elasticity, which results in a slow rate of recovery after deflection. The isocyanate used in the manufacture of semiflexible foams is PMDI, sometimes used in combination with TDI or TDI prepolymers. Both polyester as well as polyether polyols are used in the production of these water-blown foams. Sometimes integral skin molded foams are produced. 

In 1993, a total of over 6 x 10 t of polyurethanes were consumed worldwide (Table 8). The flexible foam market in the United States totaled 932,000 tons in 1994. Flexible slab foam is used predominantly in furniture, carpet underlay, and bedding molded foam is used extensively in transportation. Carpet underlay is manufactured from either virgin or scrap polyurethane foam, which is combined with a binder adhesive. The consumption of flexible polyurethane foam in the various U.S. markets in 1994 is shown in Table 9. 

Foams have limited use for these purposes. Rigid cellular PVC is good as a thermal barrier but aot for stmctural parts. Doors and frames of stmctural molded foam, eg, foamed high impact polystyrene, can be made by iajection mol ding, with recesses for hinges, striker plates, and miter corners. Sohd polystyrene and stmctural foam-molded polyurethane have been molded for door frames. 

G F-G Extruded and molded Foams for cushions, toys, gears, bushings, pulleys, shock mounts... 

PVC Plastisols 1940 M-H VG G G G Slush and rotationally molded, foamed, extruded Used in coating machines to cover paper, cloth and metal... 

Foam vs. Sheet Molding Foam vs. Hand Lay-up Foam vs. Injection... 

Theres a lot of competition between PS and the other five big thermoplastics LDPE, LLDPE, HDPE, PP, and PVC. Polystyrene continues to lose marker share, but it seems to have a permanent place in some applications, particularly molded foams (for carryout food containers), some extrusions, and sheet and film applications. About half the polystyrene ends up in packaging, 17% in electrical/electronics applications, 13% in construction, building products and furniture, and 7% in medical applications. 

Dallas, Texas, 6th-10th May, 2001, paper 115 EFFECT OF PROCESSING VARIABLES ON THE QUALITY OF INJECTION MOLDED FOAMED PARTS... 

The resulting slate of polyols has been demonstrated in conventional flexible slabstock foam [143], viscoelastic foam [144], and high resiliency slabstock and molded foams [145],... 

The mechanical characteristics of the epoxy and polyester cold-cured syntactic molded foams do not differ much from the hot-cured materials (Table 12)1),... 

Stuart, J.B. Skarke, S.C. Ogita, T. et al. Flame retardant polyolefin resin pre-expanded particles and in-mold foamed articles prepared therefrom, PCT US Patent 6,822,023 assigned to Kaneka Corporation, 2001. 

DBUa heat-activated catalyst molded foam... 

Mixed Polymers. A mixture of 5 parts of polyethylene and 95 parts of expandable polystyrene is extruded and converted to quenched pellets. The pellets are expanded and converted into molded foams with improved resistance to solvents and water vapor transmission (29). There is a polyethylene skin on the surface. 

Molded foam copolymers with 10-30% glycidyl acrylate may be crosslinked by heating in the presence of polyamines. Heat resistance may be increased to as high as 150°C. by this treatment (25). Use of certain allyl or diallyl esters to control the crosslinking of polystyrene to the desired very light extent has been disclosed as a means of obtaining foams of improved and regular cell structure (135). Block copolymers of polystyrene, polydiene (particularly polyisoprene), and polystyrene... 

Molded foam for package cushioning, flotation devices, and sports equipment is made from foamed pellets. Polyethylene pellets are foamed with volatile organic liquid and cross-linked by peroxide or electron beam. The foamed pellets are poured into a... 

Two principal PS foams that are fabricated are extruded foam and expanded for molded foams. PS foams are light, closed-cell foams with low thermal conductivities and excellent water resistance. They provide for low-temperature insulation and buoyancy media. The extruded PS foam is fabricated as billets and boards. They are made by extruding molten PS containing a blowing agent, under elevated temperature and pressure, into the atmosphere, where the mass expands. Billets and boards can be used directly or can be cut into many different forms.254... 

---