A new method to quantify crazing in various environments

Abstract

A new technique to quanti@ the rate of change of craze density in stressed transparent polymeric plates of polycarbonate was developed. The samples are placed under a creep load in a controlled temperature and humidity environment, during which the craze density is measured with a reflective imaging system at a defined rate. It has been shown that this unique method for craze detection and quantilbtion has sufficient repeatability to generate statistically acceptable data, obeying well-established trends in craze behavior. Unlike the bulk of the craze detectors currently used, the method described in the present work is an in-situ, quantitative, non-subjective, direct measurement of craze density.

Measurement of the residual mechanical properties of crazed polycarbonate. I: Qualitative analysis

“…5% rh. Craze testing was performed in a sealed chamber in the presence of a distilled water reservoir under constant load at 24°C and 85 -C 5% rh, as described in detail in previous work (13,14). The range of stress tested for ithis study was 40 to 50 MPa.…”

“…The range of stress tested for ithis study was 40 to 50 MPa. While under stress, the relative craze density, craze area divided by standard gauge area, was measured with a reflective imaging s.ystem (13,14) consisting of a CCD camera, backlight., and frame grabber. The craze growth charts were created using relative craze densities measured on the stored images with SigmaScan ProTM image analysis software (16).…”

A full-field optical crazimeter

“…Visual inspection is subjective in nature and thus cannot be reliable, while microscopic and point-by-point measurement techniques are suitable only for small objects. Techniques based on optical reflection [23] have also been reported, but their performance varies with change in the angle of incidence and angle of imaging of the scattered light. Due to the transparent nature of these materials contrast between crazes and the substrate remains poor and variations in thickness of the substrate and the presence of scattering due to surface roughness create additional noise in the captured images which further degrade image quality.…”

Influence of Nanoparticle Loading on Craze Formation and Crack Propagation of Polycarbonate in Different Environments

“…Common surface-active agents that cause ESC include organic surfactants, solvents, and humidity. The ESC issue has been under extensive investigation in recent years [1][2][3][4][5][6][7][8][9]. There have been several hypotheses presented over the years to explain the mechanism of ESC.…”

“…It is widely used in many application fields such as automotive, medical appliance, packaging, electrical applications, and a variety of sport and leisure applications [13,14]. However, it has been found that PC exhibits stress crazing (cracking) under the influence of a stress in some environments [2,3,5,12,15]. This would lead to disastrous consequences in many applications, for example, when PC is used in the medical market such as filter housings, tubing connectors, and surgical staplers.…”