Stabilization of polyolefins

The 2-imino-4-thiazolines may be used as ultraviolet-light stabilizers of polyolefin compositions (1026). 2-Aminothiazole improves adhesive properties of wood to wood glue (271). Cbmpound 428 exhibits antioxidant properties (Scheme 242) (1027). Ammonium N-(2-thiazolyl)dithio-carbamate (429) is a bactericide and fungicide used in industrial products such as lumber, paint, plastics, and textiles (1037). Compound 430 is reported (1038) to form an excellent volume of foam coating in aluminum pans when ignited with propane. 

S. Al-Malaika and G. Scott "Thermal Stabilization of Polyolefins," iu N. S. AUen, ed.. Degradation and Stabilisation of Polyolefins, AppUed Science Pubhshers Ltd., London, 1983, pp. 247—281. 

At present, high-temperature stabilization of polyolefins is still misunderstood besides, this problem presents serious difficulties. Stabilization of thermal oxidation and photoinduced destruction with the use of stabilizers in this case is inefficient, since at high temperatures these stabilizers are easily evaporated out of the polyolefin melt and decomposed with the formation of radicals capable of initiating additional kinetic chains of destruction. 

Thermal stabilization of polyolefins has been first demonstrated for low-molecular models-normal structure alkanes [29]. It has been shown that metallic sodium and potassium hydroxide with absorbent birch carbon (ABC) as a carrier are efficient retardants of thermal destruction of n-heptane during a contact time of 12-15 s up to the temperature of 800°C [130]. Olefins and nitrous protoxide, previously reported as inhibitors of the hydrocarbon thermal destruction, are ineffective in this conditions. 

London, 16th-18th Sept.1992, p.3/1-3/10. 6E IMPROVED METHOD FOR MEASURING THE STABILITY OF POLYOLEFINS... 

The laboratory-to-laboratory reproducibility of the isothermal oxidative stability procedure for measuring the oxidative stability of polyolefin insulation used in telecommunications applications has been improved from approximately 45% to approximately 85%. The improved protocol is described in some detail. 12 refs. 

Tphe major objective of this work was to understand better the effect - of heavy metals in autoxidation reactions in view of the importance of trace metals in oils, fats, rubber, plastics, and other materials. Because of our interest in the stability of polyolefins such as polyethylene and polypropylene the major model substance used was 2,6,10,14-tetramethyl-pentadecane. With its four tertiary C—H bonds it is a suitable model for either polypropylene or branched polyethylene. Hexadec-l-ene was also used since its mono-olefinic character could be typical of some residual unsaturation in polyethylene. N-alkylamides served as model substances for polyamides, and a few experiments were also carried out with methyl linoleate. While studying the causes of initiation of the autoxidation of these substances we observed that certain compounds were catalysts at low concentrations but became inhibitors at higher concentrations. The phenomenon was called catalyst-inhibitor conversion. ... 

Besides their two main uses as reinforcing fillers and pigments, small amounts of carbon blacks are used by the electrical industry to manufacture dry cells, electrodes, and carbon brushes. Special blacks are used to give plastics antistatic or electrical conduction properties. Another application is the UV stabilization of polyolefins [4.31]. 

OX. 240-250 110-120 2-3 100-120 20-30 2,5-3,5 carbon paper, carbon ribbons, fibers, UV stabilization of polyolefins... 

---