Experimental studies on the effects of spacing on dripping behavior of thin polymethyl-methacrylate slab

•The first time investigate the effect of spacing on dripping behavior of thermally thin PMMA slab.•As the spacing increased, the dripping time and mass first increased and then decreased.•The dripping behavior is assumed to correspond to the net heat flux to the surface, extensional viscosity, and gravitational force of melting PMMA.

Experiments were carried out to study the dripping behavior of vertical burning thermally thin polymethyl-methacrylate (PMMA) with different spacings parallel to the wall. With spacings of 7, 10, 13, 16, 19, 22, and 25 mm, the dripping behavior was studied by infrared video image analysis, and the mass retention was recorded by the load cells. As the spacing increased, the dripping time, dripping mass, and burnout growth distance first increased and then decreased. The minimum value was observed at the 13 mm case. The dripping behavior is assumed to correspond to the net heat flux to the surface, extensional viscosity, and gravitational force of melting PMMA. In this study, the dripping behavior was investigated using uniform PMMA samples with 200 mm height, 50 mm width, and 2 mm thickness.