Thermal
expansion refers to the size or length of an object increases with
temperature and increasing the physical properties, while the thermal
expansion coefficient of an object in the unit temperature changes, the
material rate of change in length or volume, which indicated that the
method is (coefficient × ppm ( 10-6 ℃). expansion coefficient is
important to understand the physical nature of the operation of the
design is also forming an important parameter. the different
coefficient of thermal expansion will cause the internal stress of
polymer resin, making materials, premature rupture. plastic expansion
and contraction of metal is about 6 ~ 9 times. Coefficient of thermal
expansion as the glass transition temperature before and after will
have different values, lower than the glass transition temperature Tg,
because the more brittle material present state, it will be lower
coefficient of thermal expansion; one but above the glass transition
temperature, due to material Softening become rubber state, will become
a higher coefficient of thermal expansion. It is proposed that after
the forming operation and curing temperature near the glass transition
temperature, operating temperature is too high will easily lead to a
high coefficient of thermal expansion, thermal stress cracking gum
large produce; operating temperature is low then hardened slowly, and
inconsistent production efficiency and easy to harden enough. That the
use of thermal mechanical analyzer (TMA) test sample specimen of the
thermal expansion coefficient, Tg results of their analysis prior to
the thermal expansion coefficient of 60ppm, after the thermal expansion
coefficient of 180ppm. |
