OCC has published a review on the Prolimatech PK-2 & PK-3 TIM

Often times people wonder what thermal paste is and which is best to use when they assemble their cooling devices. Thermal Interface Material, often abbreviated as TIM, is an agent applied between a heat sink and CPU/GPU cores or other integrated circuits and hot electronics. While the base of a heat sink may appear flat, they are not truly flat or smooth although lapping (the process of removing small layers at a time) can increase these traits. TIM fills the gaps between the hot object and the heat sink, thus it helps with heat conduction. In a perfect world if both surfaces were perfectly smooth and flat then paste wouldn't be needed.

Integrated Heat Spreaders (IHS) are installed on most processors and larger GPU cores. These are metal lids that protect the fragile core from damage, such as by a bad heat sink installation. The IHS conducts heat away from the cores underneath by solder or TIM. The top is usually uneven and can be easily seen through lapping. Thermal paste fills the unevenness between the two bodies. Prolimatech has provided samples of two of its newest TIMs — PK-2 and PK-3. Both come in three capacities: 1.5g, 5g, and 30g. PK-2 is thinner and meant for easy application while PK-3 is thicker and intended for higher thermal conductivity.

  Prolimatech PK-2 & PK-3 TIM Review