Jl. Longhenry et al., COOLING RATE-INDUCED GLASS-ADHESION VARIATIONS USING CRYSTALLIZING HOT-MELT ADHESIVES, Journal of Materials Science, 32(9), 1997, pp. 2283-2289
Polychlorotrifluoroethylene (PCTFE) and PCTFE copolymeric films are be
i ng used in the electronic packaging industry as insulating dielectri
c layers between microwave circuits. Because these films are semicryst
alline and, in this application, are being used as hot-melt adhesives,
the cooling rate is an important processing variable, affecting the c
rystallinity of the PCTFE films which, in turn, affect many properties
including dielectric characteristics and mechanical properties. In th
is study, the crystallinity of PCTFE and PCTFE copolymeric films as a
function of cooling rate was characterized by wide-angle X-ray scatter
ing. As expected, the degree of crystallinity decreased as the cooling
rate increased. Analysis of mechanical properties as a function of co
oling rate by tensile testing showed that the mechanical behaviour of
the films became more ductile with faster cooling rates. Because the c
ooling rate has also been shown to significantly affect adhesion in pr
evious studies, the effect of cooling rate on the bond strength betwee
n PCTFE and a glass substrate was analysed. Peel testing was performed
on PCTFE/glass laminates revealing that the adhesive bond strength in
creased as the cooling rate was increased. Thus, optimum adhesion is a
chieved with faster cooling rates. This was attributed to the higher f
racture energy and greater ductility of the adhesive.