Measuring Thermal Conductivity of Avicel® PH 105 Powder under Compression
Microcrystalline Cellulose (MCC) is a very popular binder and diluent in tablet and capsule formulations due to its excellent compressibility, stability and safety. Moreover, it is used as an adsorbent and bulking agent in cosmetic and food products.
C-Therm was recently contacted by a client interested in testing the material in both powder format and compressed tablet.
In testing any powder it is very important to understand the impact densification of the material has on the effective thermal conductivity of the material. Thus the careful and repeatable control of the compression force applied to the material during testing is a critical factor to characterize the thermal conductivity of powders accurately. The thermal conductivity value of most powders tend to increase with compression. This makes sense if you consider the thermal conductivity of air is very low. As the material is compacted the interstitial air is reduced.
C-Therm’s Compression Test Accessory (CTA) makes for an ideal tool in such work - engineered and designed to enable users to precisely control the level of compression or compaction of a sample. By accurately controlling the compression level, the characterization of thermal conductivity can be offered at representable application conditions.
Figure 1: Measuring Thermal Conductivity of Powders with Compression Testing Accessory (CTA).
In this specific testing highlight, the thermal conductivity of Avicel® PH105 was measured under 500gf, 1000gf and 1400gf of compression, with use of the C-Therm TCi thermal conductivity analyzer. The TCi employs the Modified Transient Plane Source (MTPS) technique and offers accuracy of better than 5% and precision better than 1%.
Figure 2: Avicel PH105 Thermal Conductivity Test Data under Different Compression Level (R2=0.9991).