Thermal aging glass transition temperature

The physical and chemical properties of both the solidified adhesive and the plastic substrate affect the quality of the bonded joint. Major elements of concern are the thermal expansion coefficient, modulus, and glass transition temperature of the substrate relative to the adhesive. Special consideration is also required of polymeric surfaces that can change during normal aging or on exposure to operating environments. 

The acrylic core-shell polymers are considered to offer superior ultraviolet-light and thermal-oxidative aging properties than does the more conventional reactive liquid polymeric toughener, CTBN. Hence, there is current interest in the use of acrylic core-shell polymers as tougheners for adhesives and composite matrices that possess a relatively high glass-transition temperature. 

Polybutadiene-PMMA (80 20) core-shell particles of 0.18 pm diameter have been shown to reduce the rate of embrittlement of polycarbonate degraded by physical ageing just below the glass transition temperature [132]. The unmodified polycarbonate became brittle (as assessed by 80% of specimens showing brittle fracture) after 5 h at 135 °C in air, whereas a blend containing 10 wt% of the core-shell particles withstood these conditions for 800 h before embrittlement. By using more thermally stable particles with a poly(n-butyl acrylate) core, embrittlement was further delayed to times greater than 4500 h,... 

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