Cerium plastics

Praseodymium is soft, silvery, malleable, and ductile. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air. As with other rare-earth metals, it should be kept under a light mineral oil or sealed in plastic. 

The free world market for cerium-oxide based polishing compounds is not large—approximately 4400 metric tons per year—, and we do not see a substantial growth potential despite the 11% annual growth in sales of spectacle lenses. The reason is twofold first, faster more efficient polishing compounds are available which can be used in slurry concentrations one-half that of a few years ago second, fully half the market for ophthalmic glass lenses has been captured by plastic lenses of CR-39 polymer. Cerium oxide is ineffective in polishing this material specially treated alumina or stannic oxide are used. 

Cerium sulfide pigments are produced from hydrated cerium oxide or oxalate and calcined in an oxygen-free, sulfide environment. They are silica-encapsulated to minimize water-reactivity and to improve heat stability and chemical resistance properties. Because of their low relative value-in-use, they are used primarily in engineering plastics and in particular the polyamides where high-performance organic colorant alternatives and other inorganic pigment alternatives are few. 

Two sorts of catalyst have been widely applied in plastics pyrolysis [85], namely molecular sieve catalyst or reformed molecnlar sieve catalyst, such as Y-zeoUte and REY zeolite metal oxide catalyst, snch as silica-alumina, AI2O3, CuO, ZnO, Fe203, cerium oxide and Co-Mo oxide. 

The ortho alkylation of phenol (6.24) has been carried out with a catalyst that was a solid solution of cerium(IV) and magnesium oxides.86 At 32% conversion, the selectivity was 90% for o-cresol and 8.6% for 2,6-xylenol. [The latter is a monomer for a poly(phenylene oxide), an engineering plastic.] There was no decay of activity. 

Until a few years ago, the red pigment for coloring containers, toys, household wares, plastic crates, etc. was Cadmium Red. This is Cadmium sulfoselenide red, C9Hi3CdN204SSe (CAS 58339-34-7), also known as Pigment Red 108 (see Chemnet 2015). The cadmium compound is now considered environmentally undesirable, so it is being replaced by the non-toxic Cerium(III) sulphide (Cc2S3 CAS 12014-93-6). This compound gives a rich red color and is stable up to 350 °C (Emsley 2001). 

Uses High-temp, thermoelectric material pigment for plastics, food-contact materials Trade Name Synonyms Cerium Orange PO 75 [Rhodia HPCII France... 

Commercially available, highly efficient liquid and solid scintillators were tested as standards for comparison with our samples. Ultima Gold (PerkinElmer) is a standard liquid scintillation counting cocktail, containing PPO (ca. 1 wt %) in a mixture of aromatic compounds, and phosphate and succinate surfactants. BC-400 (Bicron) is a plastic scintillator composed of organic fluors, PPO and POPOP, at <3 wt % in PVT. KG2 (Bicron) is a cerium-activated lithium silicate glass scintillator, containing 7.5 wt % of Li (95% i) as a neutron absorber, and Ce as a scintillation material. 

Mechanical polishing It is more or less similar to grinding, but the polishing compound (cerium oxide, ferric oxide) is finer. The polishing tool may be plastic, cellulose and pitch. A mixture of hydrofluoric and sulphuric acids is used for acid-polishing. 

Table 4-3 Ti nting strength of cerium sulfide pigments in plastics.

Cerium sulfide pigments can be readily dispersed in a variety of polymeric resin systems using conventional plastics processing equipment. They are both non-dusting as well as dispersible (Figure 4—10). 

Besides the fact that they are compatible with most thermoplastics, cerium sulfide pigments can also be used in a wide range of other polymers including engineering plastics, thanks to their very good heat stability. 

Breslin VT, Swanson RL (1993) Deterioration of starch-plastic composite in the environment. J Air Waste Manag Assoc 43 325-335 Breslin CB, Chen C, Mansfeld F (1997) The electrochemical behaviour of stainless steels following surface modification in cerium-containing solutions. Corrosion Sci 39 1061-1073... 

---