thermaloxidative

Thermaloxidative, also written as thermoxidative or thermo-oxidative, refers to chemical processes in which a substrate undergoes oxidation accelerated by heat and the presence of oxygen. The term is commonly used in polymer science, lubricants and oils, food chemistry, and materials aging to describe degradation pathways that are promoted at elevated temperatures.

The mechanism typically involves initiation of radical species at high temperature, followed by propagation through reactions with molecular oxygen to form peroxides and hydroperoxides, and eventual chain termination. The overall rate increases with temperature according to the Arrhenius equation and is influenced by the presence of catalysts such as trace metals, impurities, light, and the availability of oxygen. Diffusion of oxygen into a material can become the rate-limiting step in bulk systems.

In polymers, thermal oxidation can cause chain scission, cross-linking, embrittlement, discoloration, and loss of mechanical performance. In lubricants, oils, and fuels, it leads to varnish formation, sludge, and viscosity changes. In foods and beverages, thermal oxidation affects flavor, aroma, and nutritional quality. Preventive strategies include the use of antioxidants or stabilizers, processing under reduced or inert oxygen, and storage at lower temperatures or with protective packaging.

Methods to assess thermooxidative stability include oxidative induction time measurements (OIT) by differential scanning calorimetry, the Rancimat method for oils, and spectroscopic monitoring of carbonyl formation. Understanding thermaloxidative behavior is important for material design, product shelf life, and quality control across industries.