EFFECTS OF FOAMING PARAMETERS ON PHYSICAL PROPERTIES OF MICROWAVE-VULCANIZED NATURAL RUBBER LATEX FOAMS (IVCST2021)

This work reported the use of microwave vulcanization coupled with Dunlop process to prepared natural rubber latex foam (NRLF). Optimization of microwave heating for curing step was firstly carried out using a commercially available domestic microwave oven. The processing window and optimum condition for making NRLF were obtained. The optimum power and time of the irradiation were found at 600 W and 6 min, respectively. Using the optimum microwave vulcanization, effects of stirring time (2, 4, 6, 8, and 10 min) and speed (650, 950, 1250, 1550, and 1850 rpm) of foaming step on cell structure, bulk density, compressive properties, and hardness of NRLFs were investigated. Generally, the increases in the stirring time and speed in foaming step both gave rise to the volume of the air incorporated into the latex compound. This resulted in the increases in the bulk density and the number of cell but, the decrease in foam cell size. The stirring speed in a range of 950 to 1550 rpm was successfully used for preparing the NRLF. Too low and too high foaming speeds caused unstable latex compounds and failed to produce NRLF. The foam cell structure changed dramatically as the foaming speed increased. The foam mechanical properties, both compressive strength and hardness, were found to be linearly related to the foam bulk density.