Flammability of Polymers (Inhibition of Flame Reactions)

  • D.G. Thwaite

Student thesis: Doctoral ThesisDoctor of Philosophy


All commercial plastics will burn under the right
conditions. To overcome this problem incorporation of
flame retardant additives and chemical modification to
the polymer have been used with varying success. These
measures may affect solid phase pyrolysis of the resin or
the burning of volatile fragments in the gas phase. The
present research was devoted to development of methods
for studying the gas phase reactions in a manner applicable
to burning conditions.

The performance of a range of commercial flame retardant
additives was assessed in an unsaturated polyester
resin system using test methods which reflect burning and
ignition properties. A marked synergistic effect was
noted between halogenated compounds in the presence of
antimony trioxide. On heating antimony trioxide with
chlorinated paraffin antimony trichloride was shown to be
the chief reaction product. Weight loss experiments indicated
that some mixtures should have been more effective
than was observed in the early experiments. It was concluded
that these test methods provided conditions of too
low thermal stress and a number of resin formulations were
subjected to the more severe BS.476 fire propagation test.

A diffusion flame apparatus suitable for burning
model fuels was set up and a number of inhibitors were
studied but practical difficulties occurred in attempting
to disperse metal halides quantitatively in the flame.

An apparatus was designed for burning premixed model
fuel/air flames to study materials such as metal halides.
Antimony trihalides and a number of other metal halides
were shown to be effective inhibitors. The particular
efficiency of antimony trihalides was attributed to their
ability to undergo oxidation providing solid particles
which were effective in abstracting reactive flame species.

A number of techniques have been established using
known technological effects, these have been used in obtaining
some new information which is applicable on a
broader basis.
Date of Award1970
Original languageEnglish


  • flammability
  • polymers
  • flame reactions

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