dc blocking capacitor materials
Just a comment first: That is not a DC-blocking capacitor. That is the primary resonant capacitor (this is a dual-resonant design, by the looks of it) and is crucial to the operation of the Tesla coil.

The thing about Tesla coils is that their primary resonant capacitor must have a very, very low dissipation factor (&lt;0.001 is best). If your capacitor has a poor dissipation factor, then there will be serious losses, and internal heating can cause the capacitor to explode. Polypropylene film is really the best option out there due to its low dissipation factor and performance at high frequencies.

Another thing, loneoceans (who created the design you linked to) has made several newer versions of the tesla coil, so I recommend you use one of them. There are some important updates to look for. 

You'll have to remember that simply putting together this Tesla coil based on the schematic may not work. DRSSTCs are VERY finicky, and if the slightest thing is out of place, or if a resistor is miscalculated, it may not work at all. It is not at all uncommon for the transistors or capacitors to even explode under the stress. 

Keep in mind that the resonant capacitor must be rated for about 30-50x your bus voltage. In this case, you'd be using 120VAC, which means the capacitor should be rated for at least 3600V, though I would put that on the VERY low end of things. I would actually recommend rating it for closer to 6kV, to make sure you're safe. Most people use what they call a "Multi-mini Capacitor" bank, or "MMC". It's basically a bunch of capacitors connected in series-parallel configurations to give the desired voltage rating and capacitance. I built mine out of 32 Aerovox RBPS polypropylene snubber capacitors, rated for 2uF 530VAC each. I put 16 of them in series to get a voltage rating of approximately 8.5kV, and put two of these strings in parallel, giving me a total of 250nF. I calculated that value based on the physical dimensions of my coil, as well as the wire gauge, proximity of the primary to the secondary, and a wide range of other specifications. These values will be different for every coil, even if you follow a schematic. 

There is also a lot of protection circuitry which I am not seeing in this schematic. I would HIGHLY recommend joining 4hv.org. Loneoceans is a member there, as is Steve Ward and many other well-known, highly-experienced Tesla coil builders. They will be able to give you quick, accurate feedback on your setup to make sure you won't blow yourself up ;)

There is a significant amount of math, physics, and electronic theory that goes into building one of these things, so don't expect to simply build it and have it work, just like that. It's never that easy.

Good luck!