Flammable polymers

MITI is currently undergoing research to develop technology for the recycling of non-flammable plastics such as those used in business machines and computers. Their National Institute for Resources and Environment plans to decompose, without the production of harmful substances, non-flammable polymers by means of liquid phase hydrocracking, and to recover from them light oils such as benzene, toluene and xylene. The key to the technology, it is claimed, lies in the development of a catalyst which will be able to combine hazardous substances such as bromine and chlorine contained in the waste plastics. 

Unfortunately, most fatalities in fires occur by inhalation of toxic vapours. These can be carbon monoxide (which arises from incomplete combustion), cyanides (from nitrogen-containing polymers) and chlorides (from chloropoly-mers). These are the adverse consequences of flammable polymer combustion. They can be overcome by using breathing apparatus, face masks, etc. 

The principles needed to design a polymer of low flammability are reasonably well understood and have been systematized by Van Krevelen (5). A number of methods have been found for modifying the structure of an inherently flammable polymer to make it respond better to conventional flame retardant systems. For example, extensive work by Pearce et al. at Polytechnic (38, 39) has demonstrated that incorporation of certain ring systems such as phthalide or fluorenone structures into a polymer can greatly increase char and thus flame resistance. Pearce, et al. also showed that increased char formation from polystyrene could be achieved by the introduction of chloromethyl groups on the aromatic rings, along with the addition of antimony oxide or zinc oxide to provide a latent Friedel-Crafts catalyst. 

The reactor system in a pilot plant contains stock tanks that are 24 in in diameter and 36 in high. A relief system must be designed to protect the vessel in the event of fire exposure. The vessel contains a flammable polymer material. What rupture disc diameter is required to relieve the vessel properly Assume a discharge pressure of 10 psig. The molecular weight of the liquid is 162.2, its boiling point is 673°R, the heat of vaporization is 92.4 Btu/lb, and the heat capacity ratio of the vapor is 1.30. 

The grade. An inherently flammable polymer can be VO classified for a special fire-retardant grade or, vice versa, an inherently fire-resistant polymer can be HB classified for a special grade containing too high a level of flammable plasticizer. 

Safety glasses must be worn in the laboratory at all times. Appropriate safety gloves must be worn when preparing solutions. Caution must be used in making polymer solutions. Material safety data sheets must be read regarding the solvent, polymer, and suspected additives as many solvents and monomers are toxic, carcinogenic, or flammable. Polymer solutions should be made up at concentra-... 

New Flame Retardant Materials Nonhalogenated Additives from Brominated Starting Materials and Inherently Low-Flammability Polymers... 

To summarize, the field of flame retardancy for polymers is in a state of flux, and multiple new technologies and approaches are expected to arise in the coming decade. In this entry, we focus on some new technology from our laboratory, including nonhalogenated flame retardants synthesized from bromi-nated starting materials, and inherently fire-safe and low-flammability polymers. 

In 1870, John Wesley Hyatt patented use of an excellent plasticizer for cellulose nitrate camphor ( ). This led to the successful launching of Celluloid. The combination of cellulose nitrate and camphor produced such an outstanding polymer composition that it stood as the standard of comparison for later plasticized compositions. Researchers began to study cellulose acetate as a less-flammable polymer base and to examine hundreds of substances to find a plasticizer that was analogous to camphor s performance in Celluloid. This search successively embraced other polymers as they became known. 

Intrinsically non-flammable polymers are few, but phenolic resins have a good reputation both in Are and smoke performance, which has resulted in their becoming increasingly favoured for reinforced plastics structures, for example, underground transport, where such concerns are greatest. Polyether ether ketone (PEEK) is also a low fire and smoke polymer. Unsaturated polyesters, vinyl esters and epoxy resins bum readily, but modified versions are available with improved behaviour. For example, both bromine and chlorine are used extensively in the form of chlorendic (HET) acid, tetrachlorophthalic anhydride (TCPA) and tetrabromo-phthalic anhydride (TBPA) which can be reacted into the polyester in small quantities and can act as permanent (non-migrating) flame retardants. 

The effect of polymer blending on flammabihty was studied in combination of ABS (one of the most flammable polymers) and PVC (intrinsically flame retardant). The 30 wt% PVC in blend was not sufficient to make substantial changes in ABS behavior.Only the addition of iron peroxide helped to increase LOI and reduce smoke by 45%. 

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