Investigation of thermolabile sizings for debonding on demand in glass fiber-reinforced plastics

A major drawback in the usage of glass fiber-reinforced plastics (GFRP) is their limited recyclability at the end of their service life. This is mainly due to the challenging separation of the components, namely the glass fibers and the epoxy matrix. A possible solution is the implementation of a separation trigger, following the principle of “debonding on demand.” To this end, a novel glass fiber sizing is investigated which is designed to induce interfacial delamination between glass and polymer at specific temperatures due to gas evolution. As active components for the thermolabile sizing, two variants are discussed: poly(vinyl alcohol), functionalized with various carboxylic acids, and cellulose nitrate nanoparticles. Debonding experiments performed on flat glass demonstrated successful component separation for both systems. Afterward, glass fibers were spun using the novel sizings and tested regarding interfacial shear strength and bending behavior of the resulting GFRP. These tests were performed both before and after heating to simulate the debonding process. Although, debonding was demonstrated on flat glass substrate, the effects are significantly less pronounced in actual GFRP systems. It is therefore assumed that additional temperature-induced effects within the composite mask or superimpose the interfacial delamination process.