Materials deterioration when working

As with c -polyisoprene, the gutta molecule may be hydrogenated, hydro-chlorinated and vulcanised with sulphur. Ozone will cause rapid degradation. It is also seriously affected by both air (oxygen) and light and is therefore stored under water. Antioxidants such as those used in natural rubber retard oxidative deterioration. If the material is subjected to heat and mechanical working when dry, there is additional deterioration so that it is important to maintain a minimum moisture content of 1%. (It is not usual to vulcanise the polymer.)... 

Cellulose nitrate poses two major health risks. First, old film made of cellulose nitrate has a tendency to deteriorate and decompose. That process results in the release of oxides of nitrogen, which may be toxic to a greater or lesser degree. This problem is of special concern to people who have occasion to work with old films, but not usually to the general public. Second, cellulose nitrate is a very flammable material that ignites when exposed to even minimal flames or sparks. Most products that contain cellulose nitrate today have been treated to minimize that risk. However, products that were made many years ago do not have the same protection and may pose safety risks to people who come into contact with them. 

A less sanguine view of the architectural use of GRP is taken by Fidler who reviewed various projects, mainly in connection with building restoration work [18]. Several incidences of unacceptable deterioration of newer replacement items when compared with the longevity of more conventional constructional materials are cited, although much of this appears to have been due to poor workmanship. 

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