Carbon black (CB) distribution and electrical properties of CB-filled conductive polymer composites were studied theoretically and experimentally in detail. Several important fundamental issues have been addressed. ₄...[ Read more ]

Carbon black (CB) distribution and electrical properties of CB-filled conductive polymer composites were studied theoretically and experimentally in detail. Several important fundamental issues have been addressed.

The CB distribution in a pure semicrystalline polymer was elucidated using RuO₄ vapor staining technique and transmission electron microscopy (TEM). It has been found that the CB particles were present between the lamellae of the semicrystalline polymer. Based on the TEM results, schematic models for the CB distribution in pure semicrystalline polymers were developed.

The CB distribution in binary immiscible polymer blends was investigated theoretically and experimentally. A thermodynamic model was derived to predict the CB distribution in immiscible polymer blends. The predictions obtained by simulation agreed very well with the experimental observations by scanning electron microscopy (SEM), optical microscopy (OM), and TEM. An in-complete wetting model was also developed for the case when one of the two polymer components has a very high viscosity. In addition, a novel approach was developed to localize the CB particles at the interface between two immiscible polymers, subsequently the CB-filled conductive polymer composites with a low percolation threshold less than 0.01 volume fraction of CB were successfully prepared.

The positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects of CB-filled a semicrystalline polyurethane-based shape memory polymer (SMP) composite were studied. It has been observed that apart from the CB content and the CB type, thermal aging could impose a pronounced influence on their PTC and NTC effects.

The PTC and NTC effects of CB-filled immiscible polymer blends were investigated. Some novel physical effects, such as double-PTC effects, delayed NTC effect, and reduced PTC effect, have been observed and explained in terms of their morphological features. Schematic models were also given to predict the PTC and NTC effects of the composites with different morphologies.

The effects of mechanical strain on the electrical resistance of CB-filled pure polymers and immiscible polymer blends were elucidated. Positive strain coefficient (PSC) and negative strain coefficient (NSC) effects were observed and explained using tunneling junction and two-process models. A CB-filled pure polymer composite that is very sensitive to mechanical strain was also successfully prepared, which has potential applications in making strain sensors.