Cooling endothermic degradation

A1(OH)3 ° In both cases, the reaction is endothermic which contributes a cooling effect to the degrading polymer. Borates degrade at different temperatures depending on their composition (ammonium -120 C, barium metaborate - 200°C, zinc borate - 290°C). ... 

As a FR, ATH has several modes of action. When it degrades thermally, the polymer is cooled by endothermic decomposition, which implies less release of volatile products. The aluminum oxide resulting from the dehydration of ATH forms a barrier layer on the surface... 

Differential scatming calorimetry (DSC) study was carried out on the TA instruments model 2920-DSC, The heat flow and temperature were calibrated using Indium as a standard. Nitrogen was used as a protection gas (30 ml/min) and no thermal degradation was detected. Thin films were encapsulated in Al pans and the sample mass was about 9 mg. The m-iPP was melted at 200°C for 1 minute, then cooled to 117°C at 10C°/min for isothermal crystallization. The crystallization time at 117°C varied from 1 to 40 minutes, and the sample was immediately re-heated at 5°C/min (without cooling) to observe the development of melting endotherms after partially crystallizing the material. 

Ablative polymers are used for the purpose of cooling which is due to the fact that work has to be done at the surface. Endothermic processes take place (e.g. melting, vaporization, thermal decomposition, etc.). Some heat is dissipated by radiation from the very hot surfaces. Pyrolysis of an ablative polymer starts when its decomposition temperature is reached at the surface. Ablation may be different from bulk degradation as the surface is preferentially heated. One refers to surface pyrolysis or "linear pyrolysis". The loss of material from the surface is termed "surface regression". 

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