Polyphenylene foam

Triphenyl phosphate [115-86-6] C gH O P, is a colorless soHd, mp 48—49°C, usually produced in the form of flakes or shipped in heated vessels as a hquid. An early appHcation was as a flame retardant for cellulose acetate safety film. It is also used in cellulose nitrate, various coatings, triacetate film and sheet, and rigid urethane foam. It has been used as a flame-retardant additive for engineering thermoplastics such as polyphenylene oxide—high impact polystyrene and ABS—polycarbonate blends. 

The substrates tested alone have substantially different values. Polycarbonate (1/4 inch) structural foam has an of 27.5, modified-polyphenylene oxide (1/4 inch), 84.4, and RIM polyurethane (1/2 inch), 173.3. These values compare with 164.4 for 1/4 inch hardboard and 139.1 for 1/4 inch plywood. A comparison of graphite, nickel, and copper/aciylic coatings on polycarbonate and modified-polyphenylene oxide substrates illustrate a dramatic result. Despite a factor of 3 difference in substrate performance, the Q and Fs values for the coated samples are very similar. The Q for the modified-polyphenylene oxide samples are 0.7 to 0.5 that of the uncoated sample. One would expect a similarity in Fs for the coated sample, but such a reduction in Q is dramatic. Both Q and Fs are determined by the 2 mil surface. 

Table VI. Comparison of Needle-Flame Test Results and Oxygen Indices for Modified Polyphenylene Oxide Structural Foam Samples...

Figure 3. Continued. NBS Smoke Chamber results (non-flaming) for modifled-polyphenylene oxide and RIM polyurethane structural foam.

Coatings can interact with the substrate as shown with zinc on modified-polyphenylene oxide structural foam. Examination of zinc on modified-polyphenylene oxide has been undertaken to ascertain the origin of the synergism and is reported separately. The presence of zinc shows an increase in char, and a decrease in low molecular weight volatiles at pyrolysis temperatures versus the uncoated substrate. 

The effect of blending LDPE with EVA or a styrene-isoprene block copolymer was investigated (178). The properties (thermal expansion coefficient. Young s modulus, thermal conductivity) of the foamed blends usually lie between the limits of the foamed constituents, although the relationship between property and blend content is not always linear. The reasons must he in the microstructure most polymer pairs are immiscible, but some such as PS/polyphenylene oxide (PPO) are miscible. Eor the immiscible blends, the majority phase tends to be continuous, but the form of the minor phase can vary. Blends of EVA and metallocene catalysed ethylene-octene copolymer have different morphologies depending on the EVA content (5). With 25% EVA, the EVA phase appears as fine spherical inclusions in the LDPE matrix. The results of these experiments on polymer films will apply to foams made from the same polymers. 

A comparative stndy is made of the properties of energy absorbing foams nsed in passenger protection in cars, with particular reference to dynamic impact and compression strength. Materials examined inclnde polyurethanes, PP, PS and polyphenylene oxide/PS. 7 refs. 

In 1982 the leader in structural plastics used for structural foams parts was modified polyphenylene oxide (NORYL ), accounting for almost three-quarters of all material usage. Polycarbonate held a strong second materials position, followed by ABS, with polystyrene next (5). 

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

Noryl . [GE Plastics GE Plastics Ltd.] Modified polyphenylene oxide resins engineering resin for inj. mcdding, ex> trasitm, structural foam used for computers, business equip., automotive, elec., electronics, construction, telecommunications, tqppliances, and other industries. 

Prevex . [GE Plastics] Polyphenylene eiha resins fa inj. moldiiig, extrusion, structural foam molding fa puriqis, housings, small qqdiances, lawn care toob, powa toob, industrial devices, shea pidile, business machine parts, elec, enclosures and connectors. 

A rigid foam is defined as one in which the polymer matrix exists in the crystalline state or, if amorphous, is below its Tg. Following from this, a flexible cellular polymer is a system in which the matrix polymer is above its Tg. According to this classification, most polyolefins, polystyrene, phenolic, polyycarbonate, polyphenylene oxide, and some polyurethane foams are rigid, whereas rubber foams, elastomeric polyurethanes, certain polyolefins, and plasticized PVC are flexible. Intermediate between these two extremes is a class of polymer foams known as semirigid. Their stress-strain behavior is, however, closer to that of flexible systems than to that exhibited by rigid cellular polymers. 

Modified Poiyphenyiene Ether Thermoplastic polyphenylene ether alloys with impact polystyrene. Has good impact strength, resistance to heat and fire, but poor resistance to solvents. Processed by injection and structural foam molding and extrusion. Used in auto parts, appliances, and telecommunication devices. Also called MPE, MPO, and Modified Polyphenylene Oxide. 

While the number of styrenic blends might seem limitless, compatibility and morphology limit blend types. Styrenic blends are many but most are limited to only a couple types. The most important blend is ABS and polycarbonate (PC). Next in importance is ABS and polyamide (or nylon, PA). PS and polyethylene are often used in expandable foams. PS and polyphenylene ether (PPE or PPO) are commercially important blends, which are covered in later chapters. The other classes of the styrenic blends are not major product lines but can be very important in some applications. 

Structural foam molding ABS, acetal, nylon, polycarbonate, polyethylene, polyphenylene oxide, polypropylene, polystyrene, polysulfone, SAN... 

Conventional insulation materials are of the closed-cell foam type and are unlikely to be used in this application, because the pressure will crush the cells, increasing the thermal conductivity. Yates investigated open-cell foams for use with liquid hydrogen and reported best results with polyphenylene oxide (PPO). This is an anisotropic open-cell material with elongated cells in the depth direction, as developed by General Electric. From Yates data on the thermal conductivity of this material and the known properties of methane. Walker, Stuchly, and Read have estimated that the effective thermal conductivity for PPO foam filled with methane at 7.0 MPa ( 1000 psi) would be of the order of 70 mW/m K. It is, however, very important to note this value is speculative and experimental verification is urgently required. 

Insulation (noise and seismic vibrations), sonor foams Laminates of rubber (mostly natural/chloroprene), polyphenylene oxide (PPO, UF foams, open cell foams of PU, PIR, PS... 

Many open cell foams such as PU, PIR, PS and integral foams based on polyphenylene oxide are used in construction for acoustic insulation [61-63]. UF and PF foam are used for interior soimd absorbing floors [31]. 

Endex ABS 50 is a new endothermic foaming agent for a wide range of thermoplastics, including polycarbonate, polyphenylene ether, nylon. 

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