Polyphenylene Oxides PPO

PPO is a thermoplastic with excellent heat and dimensional stability, and satisfactory chemical resistance. The material may be found primarily in pump parts and certain other applications where impact strength, good modulus, and reasonable abrasion resistance are required. The chemical resistance of the material is good and the allowable temperature limit of 120°C, under appropriate conditions, extends the attractiveness for use of the product. The cost requires specific need for an identifiable application before choosing the product over many less costly thermoplastics. 

This is a iinear poiymer made by the cataiytic oxidative coupiing of 2,6 dimethyi-phenoi. PPO has a use temperature range of -55 to 175 °C. It is transparent but yeiiow in coiour and is rather expensive being used mainiy in engineering appiications. Its resistance to repeated steam sterilisation makes it a useful plastic in food engineering applications. It is also used in the fabrication of domestic food mixers. 

A modified form of PPO is available with the trade name Noryl (General Electric Company). This is cheaper than PPO and has excellent mechanical properties over the range -40 to 120 °C. This polymer is used extensively in food contact applications where an impact strength slightly inferior to that of PPO is acceptable. 

Noryls, patented by G.E. Plastics, are amorphous modified polyphenylene oxide resins. The basic phenylene oxide structure is as follows  

Several grades of the resin are produced to provide a choice of performance characteristics to meet a wide range of engineering application requirements. PPO maintains excellent mechanical properties over a temperature range of from below — 40°F ( —40°C) to above 300°F (149°C). 

Polyphenylene oxide has excellent resistance to aqueous envirorunents, dilute mineral acids, and dilute alkalies. It is not resistant to aliphatic hydrocarbons, aromatic hydrocarbons, ketones, esters, or chlorinated hydrocarbons. Refer to Table 2.30 for the compatibility of PPO with selected corrodents. Reference [1] provides a more extensive listing. 

PPO finds application in business equipment, appliances, electronics, and electrical devices. 

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Polyphenylene oxide (PPO) is produced by the condensation of 2,6-dimethylphenol. The reaction occurs by passing oxygen in the phenol solution in presence of CU2CI2 and pyridine ... 

Engineering polymers are often used as a replacement for wood and metals. Examples include polyamides (PA), often called nylons, polyesters (saturated and unsaturated), aromatic polycarbonates (PCs), polyoxymethylenes (POMs), polyacrylates, polyphenylene oxide (PPO), styrene copolymers, e.g., styrene/ acrylonitrile (SAN) and acrylonitrile/butadiene/styrene (ABS). Many of these polymers are produced as copolymers or used as blends and are each manufactured worldwide on the 1 million tonne scale. 

Modified-polyphenylene oxide (or ether) is a blend of high impact polystyrene (PS) and polyphenylene oxide (PPO), plus thermal stabilizers and a triarylphosphate flame retardant. Studies of the mechanism of the flame retardant in modified-polyphenylene oxide have shown some evidence for both solid phase and vapor phase inhibition (4). Indeed, one is always interested to know whether flame retardant action is on the solid or vapor phase. 

Sauk, J., Byun, J. and Kim, H. J. 2005. Composite Nafion/polyphenylene oxide (PPO) membranes with phosphomolybdic acid (PMA) for direct methanol fuel cells. Journal of Power Sources 143 136-141. 

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. 

Aromatic cyclic chains are more stable than aliphatic catenated carbon chains at elevated temperatures. Thus linear phenolic and melamine polymers are more stable at elevated temperatures than polyethylene, and the corresponding cross-linked polymers are even more stable. In spite of the presence of an oxygen or a sulfur atom in the backbones of polyphenylene oxide (PPO), polyphenylene sulfide (PPS), and polyphenylene sulfone, these polymers are... 

Other compatible commercial systems are as follows polystyrene (PS) and polyphenylene oxide (PPO) polyvinyl chloride (PVC) and nylon 66 PVC and acrylonitrile-butadiene rubber (NBR) and PS and polycarbonate (PC) (up to 60% PC). 

Amide urethane, and ester groups in the polymer chain, such as those present in nylons and polyesters may be hydrolyzed by acids to produce lower-molecular-weight products. Polyacetals are also degraded by acid hydrolysis, but ethers, such as polyphenylene oxide (PPO), are resistant to attack by acids. 

Several flexible polymers, such as natural rubber (NR) synthetic rubber (SR) polyalkyl acrylates copolymers of acrylonitrile, butadiene, and styrene, (ABS) and polyvinyl alkyl ethers, have been used to improve the impact resistance of PS and PVC. PS and copolymers of ethylene and propylene have been used to increase the ductility of polyphenylene oxide (PPO) and nylon 66, respectively. The mechanical properties of several other engineering plastics have been improved by blending them with thermoplastics. 

Eq. (5) in conjunction with Eqs. (8) and (9) have, so far, provided adequate representation of experimental isotherms6 32, which are characterized by an initial con vex-upward portion but tend to become linear at high pressures. Values of K, K2 and s0 have been deduced by appropriate curve-fitting procedures for a wide variety of polymer-gas systems. Among the polymers involved in recent studies of this kind, one may cite polyethylene terephthalate (PET) l2 I4), polycarbonate (PC) 19 22,27), a polyimide l6,17), polymethyl and polyethyl methacrylates (PMMA and PEMA)l8), polyacrylonitrile (PAN)15), a copolyester 26), a polysulphone 23), polyphenylene oxide (PPO)25), polystyrene (PS) 27 28), polyvinyl acetate 29) and chloride 32) (PVAc and PVC), ethyl cellulose 24) (EC) and cellulose acetate (CA) 30,3I>. A considerable number of gases have been used as penetrants, notably He, Ar, N2, C02, S02 and light hydrocarbons. 

Polyphenylene oxide (PPO) or Polyphenylene ether (PPE) is an amorphous polymer with a softening temperature of about 210 °C. To improve its processability it is mostly blended with PS (modified PPE, e.g. Noryl ), which is at the cost of its heat distortion temperature. The properties are excellent the applications are mainly in fine-mechanical construction, in automotive parts, in household equipment etc. 

Polyphenylene oxide. Oxidative polymerization of 2,6-xylenol to the engineering resin polyphenylene oxide (PPO) is catalyzed by copper and manganese amines. Pyridine is a typical amine used in the polymerization. 

Comparison of Permeability and Separation Properties of the CsHe/CsHs System for Individual Penetrants, as well as for Their Equimolar Mixture, in Various Polyimides and in Polyphenylene Oxide PPO... 

Figure 1. Nitrogen adsorption and desorption Isotherms for polyphenylene oxide (PPO) membranes. (PPO-9 and PPO-10 Indicate the polymer concentration (wt. %) in the casting solution).

Injection moldable polyphenylene oxide (PPO, Noryl) was produced by A. S. Hay in the earlv 1960 s by the copper-amine catalyzed oxidation of xylends. (21)The commercial product is a blend of PPO and polystyrene. PPO is being produced at an annual rate of 70 thousand tons in the U.S. and it is anticipated that the annual production in the late 1980 s will exceed 175 thousand tons. 

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