Parylene exhibits very little absorption in the visible region and is, therefore, transparent and colorless. Below about 280 mu, both N and C absorb strongly.
Both parylenes are relatively featureless to at least 50-micron wavelengths (except for a few characteristic peaks), especially in thin film form (<1 u).
Parylene C and N films show a high degree of resistance to degradation by gamma rays in a vacuum. Tensile and electrical properties were unchanged after 100 megarad dosage at a rate of 1.6 megarads per hour. Exposure to air leads to rapid embrittlement.
Although stable indoors, the parylenes are not recommended for use outdoors when exposed to direct sunlight.