Background noise analysis and improvement for the water vapor and oxygen transmission rate test of free-standing films

Abstract

The background noise (BGN) of test equipment affects the lower detection limit of the measurement range, and achieving an ultralow BGN is identified as a formidable challenge for highly accurate testing of a free-standing film. In this paper, a new gas transmission rate test apparatus is designed by detecting the electrical resistance increase with calcium corrosion. Thanks to the new design strategy, the only permeable place of this apparatus is the clamping and holding site. Mathematical methods for calculating the molecular permeation behaviors and magnitude of BGN are devised. The results show that the properties and structures of the materials significantly affect the BGN value. By using a sealant with low permeability (2.25 × 10−15 g cm cm−2 s−1 Pa−1) and a clamping ring with small width (2.5 mm) and testing an ultrahigh barrier (WVTR: 10−6 g m−2 day−1), the BGN could reach a level of 10−11 g m−2 day−1. With theoretical guidance, after optimization, one sealing structure obtained an ultralow BGN value (∼10−6 g m−2 day−1) in the actual test. The electrical resistance test has many advantages over existing methods. Additionally, the computational method devised in this study to examine the effects of materials provides a useful tool to achieve high-accuracy testing.