Real-time monitoring of tablet surface temperature during high-speed tableting by infrared thermal imaging

Abstract The effect of tableting speed on the surface temperature of tablets during the high-speed tablet manufacturing process was monitored using an infrared (IR) thermal imaging camera. The direct compression prescription powder was tableted using a practical rotary-tableting machine at 10, 25, and 40 rpm with a compression force of 9 kN to produce 200 mg tablets over 30 min. Subsequently, the weight and hardness of the tablets were measured to determine their pharmaceutical properties. The surface temperatures of the tablets were continuously measured using an IR camera, and the relative frequency distribution (RFD) and cumulative relative frequency distribution (CRFD) of the surface temperature of the entire tablet, compression surface, and side surface were obtained from the IR image. The IR thermal imaging parameters, such as the maximum surface temperature (Tmax), mode temperature (Tmo), increasing temperature of the tablet after tableting compression (ΔT), 50% temperature of the ΔT RFD (ΔT50%), and thermal energy parameter for tableting compression (ΔQ’) were evaluated based on the RFD and CRFD. These parameters indicated that the thermal behaviors of the top and side surfaces of the tablets were considerably different depending on the tableting speed. At a tableting speed of 10 rpm, the temperature of the top surface of the tablet was higher than that of the side surface; however, at 25 and 40 rpm, the temperature of the side surface of the tablet was higher than that of the top surface. The weight and hardness of the tablets tended to decrease with an increase in tableting time.