Quantitative in-situ evaluation of environmental stress cracking resistance in poly(methyl methacrylate) using automated crack detection

In this study, an in-situ evaluation method was developed to provide an objective and quantitative analysis of the environmental stress cracking (ESC) resistance of poly (methyl methacrylate) (PMMA) materials. The ESC resistance of PMMA materials with different molecular weights was evaluated under varying solvent temperatures (22, 40, and 60 °C) and bending strains (0%, 0.5%, and 1%). Differences in ESC behavior between the two PMMA materials under different conditions were identified by observing surface damage and determining the timing of crack initiation and fracture occurrence, revealing distinct crack patterns associated with molecular weight. Quantitative analysis of surface observations provided objective material characteristics, and a predictive model for crack evolution was developed through dual fitting analysis combining lognormal distribution and power series approaches. The reliability of the evaluation method was confirmed by establishing optimal image threshold values and reference crack areas used for crack detection. This approach, applicable to transparent polymer specimens under controlled laboratory conditions, enables standardized evaluation of ESC behavior through visual-based crack detection. These findings clarify the ESC mechanism of PMMA as a function of molecular weight and support the potential standardization of ESC evaluation using the developed method and predictive modeling framework for similar transparent polymeric materials. ● Investigated differences in ESC resistance of PMMA materials with varying molecular weights under various solvent temperature and bending strain conditions, revealing distinct material behaviors. ● Proposed a new in-situ evaluation method for objectively assessing ESC performance. ● Applied the technique to quantify material-specific characteristics and accurately identify crack initiation times. ● Determined optimal evaluation parameters and validated the method’s high accuracy compared to visual inspection results.