Materials degradable

Starch and cellulosic materials are frequently used as fillers in degradable materials. The addition of starch to LDPE in combination with a pro-oxidant increases the photooxidation rate and the formation of hydroperoxides and carbonyl groups. Starch alone does not increase the photooxidation rate. The addition of starch to LDPE increases its stability in 80°C water. Slower degradation in water is due to leaching out of the pro-oxidant. The addition of starch causes biodegradation process under soil burial conditions. Further increase in the degradation rate can be achieved by preheating polyethylene filled with starch.  

Hydroxyapatite and magnesium oxide improve biodegradation of polylactides. The degradation occurs in the bulk material whereas, in unfilled material, degradation occurs by surface erosion. 

2 Bataille P, Schreiber H P, Mahlous M, Antec 93. Conference Proceedings, New Orleans, La., 

5 Svorcik V, Micek I, Jankovskij O, Rybka V, Hnatowicz V, Wang L, Angert N, Polvm. Degradat. 

8 Abdel-Aziz M M, Youssef H A, El Miligy A A, Yoshii F, Makuuchi K, Polym. Polvm. Composites, 

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J. E. Guillet, Degradable Materials Perspective, Issues and Opportunities, CRC Press, Boca Raton, Fla., 1990, pp. 55—97. 

The word asphalt has been carelessly used in that it is not adequately differentiated from thermally degraded materials, especially coal tar and derivatives. It is essential to differentiate asphalt from these materials which contain known carcinogens and health ha2ards. For this reason, the use of cracked asphalts must be treated with caution. 

Erosion and cavitation both can degrade materials simply by mechanical means or by combining the effects of mechanical deterioration and corrosion to produce a synergistic result. However, the mechanisms by which erosion and cavitation operate, and the resulting damage, are quite distinct. 

The source of ignition of the polyethylene glycol was probably autoignition of the degraded material. The report recommends the use of nonabsorbent insulation for equipment containing heat-sensitive materials such as EO [19, 20]. 

F.A. Niehaus J.A. Wiegand, Investigation of Environmentally Degradable Materials , NAVAMMODEPOT RQTR-276... 

A different approach consists of reacting dimethyl terephthalate and dimediyl adipate with 1,4-butanediol in die experimental conditions of poly(butylene terephthalate) (PBT) syndiesis. The resulting copolyester (Eastman s Eastar Bio) presents properties close to diose of odier degradable materials (Table 2.10). 

In order to improve the mechanical properties of PHB or poly(3HB-co-3HV), many have reported on blending these biopolymers with other, both degradable as well as non-degradable, materials. However, due to the lack in compatibility between most polymers no substantial improvements in mechanical properties were reported upon, up to now [90]. 

Degradable materials can be destroyed by natural environmental elements such as light, oxygen and water. 

As discussed in Section 11.12.2, several root causes exist for black streak contamination in molded parts. These root causes include degradation of the resin in the screw channels and nonreturn valve or runner system, degraded material entering with the resin feedstock, and poorly dispersed pigments in the color masterbatch. To determine if the color concentrate masterbatch was the source of the black streaks, the color concentrate was removed from the feedstock and only natural... 

A common feature to both intrusive and non-intrusive mechanisms of attack is that decay can be initiated only from the surface, a conclusion from which three correlaries can be derived (1) The decay rate ultimately depends on the percentage of surface area consisting of degradable material ... 

Composts can be made from most biodegradable materials, and could derive from many unusual sources. If it originates from municipal solid waste, however, care should be taken that no toxic and non-degradable materials remain after the supplier s separation processes. Small pieces of brick and concrete, glass and plastic (inerts), lead residues from old car batteries and cadmium from electroplated items are possible. A useful work on specifications and recommended chemical analyses of composts is the book by Bertoldi et al., 1987. 

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