Thermal Degradation

Structural Breakdown

Chemical breakdown of wood fibers, synthetic binders, or surface coatings caused by exposure to high temperatures reduces the physical strength and brightness of paperboard. High temperatures trigger thermal degradation, which begins with the loss of bound water and proceeds to the depolymerization of cellulose chains. This reaction weakens the fiber-to-fiber bonds within the sheet, making the board brittle and prone to cracking when folded.

The process also leads to yellowing as hemicelluloses and lignin oxidize. This loss of elasticity complicates subsequent creasing and converting steps.

Industrial Impact

Converting and printing operations must be run below specific temperature thresholds to prevent material failure. During the high-speed application of hot-melt adhesives, overheating can char the glue, clogging nozzles and weakening the seal. Similarly, on the printing press, excessive drying temperatures can damage the clay coating or blister the board surface.

These failures lead to rejected batches and increased waste.

Prevention Method

Precise control of temperature and dwell time on the production line remains the most effective way to avoid these heat-related issues. Modern dryers use infrared sensors to monitor sheet temperature in real time. Applying chemical protective additives during the paper-making process also helps stabilize the fibers against oxidation.

A heavy mechanical press rests on a dark shelf adjacent to a stack of unprinted white paper substrates used for physical property analysis.

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