Multilayer Diffusion Barrier Coatings on Poly(propylene) with Improved Temperature Durability

The improvement of temperature durability for autoclaving of silicon oxide (SiO x ) diffusion barrier coatings on poly(propylene) (PP) by deposition of thin amorphous hydrogenated carbon‐nitrogen (a‐C:N:H) intermediate layers was investigated. Attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy revealed terminating amino and nitrile groups responsible for low compressive stress in a‐C:N:H. Uniaxial tensile tests showed a higher crack onset strain (COS) for a‐C:N:H of 2.7% compared to 0.7% for SiO x . Best temperature durability was achieved by a three‐layer coating from a‐C:N:H, an intermediate layer deposited by a mixture of N 2 , C 2 H 2 , hexamethyldisiloxane (HMDSO), and a SiO x layer. The oxygen transmission rate (OTR) was only increased from 6 to 22 cm 3 ·m −2 ·d −1 ·bar −1 after exposure to 140 °C for 30 min, whereas for single SiO x barrier coatings, severe loss of barrier properties of 1 040 cm 3 ·m −2 ·d −1 ·bar −1 was evidenced due to the formation of cracks.