Flame Retardant Paraffin-Based Shape-Stabilized Phase Change Material via Expandable Graphite-Based Flame-Retardant...

Thermal energy storage materials are widely used in energy-saving buildings. However, the flammability of shape-stabilized phase change materials (SSPCM) poses a safety risk. Conventional methods to reduce flammability have shown limited success. Prior research has shown that adding flame retardants in bulk can only moderately improve fire resistance. That uncertainty drove the search for alternative strategies. No prior work had resolved how surface coatings might influence flame propagation. This gap motivated the investigation of surface coatings as a solution. The need for safer, more effective thermal storage materials is clear. This study aimed to explore a novel approach to flame retardance.

The aim of this work was to evaluate surface coatings as a means to improve the fire resistance of SSPCM. The specific problem addressed is the inherent flammability of paraffin-based thermal storage materials. The motivation stems from the need for safer building materials. The researchers propose that surface coatings could offer better flame retardance than bulk methods. This approach could reduce the amount of flame retardant needed. The study tested various coatings to find the most effective one. The goal was to identify a coating that could significantly delay combustion. The ultimate purpose was to develop a safer and more efficient thermal storage material.

A series of surface coatings with different flame retardants were applied to SSPCM. The coatings were tested under controlled burning conditions. Horizontal burning time was measured to assess flame propagation. Limiting oxygen index was calculated to determine flammability thresholds. Peak heat release rate was recorded during combustion tests. Total smoke production was also measured as a safety indicator. The performance of each coating was compared to identify the best one. The most effective coating was further analyzed for its flame-retardant mechanism.

The EG coating showed the best flame-retardant performance among all tested coatings. Horizontal burning time was significantly prolonged with this coating. The limiting oxygen index exceeded 30%, indicating improved fire resistance. The peak heat release rate dropped from 1137.0 to 392.5 kW/m². The coating achieved a V0 classification in fire safety standards. Total smoke production was minimized compared to other coatings. The EG coating formed thick porous carbon layers at high temperatures. These layers blocked the transfer of heat, oxygen, and combustibles.

The study demonstrated that surface coatings can effectively enhance flame retardance in SSPCM. The EG coating outperformed other flame-retardant options tested. The coating mechanism involves two stages: first, it hinders paraffin evaporation at moderate temperatures. Second, it forms a protective carbon layer at high temperatures. This dual-action strategy reduces fire risk without excessive flame retardant use. The findings suggest that surface coatings are a viable alternative to bulk methods. The approach may be applicable to other flammable thermal storage materials. The authors propose that this strategy could be adopted in building materials design.