production information-pg电子app

4.1 linear thermal expansion coefficient  (α)

linear thermal expansion coefficient refers to the elongation of the unit length of glass when heated per 1℃ in a certain temperature range. it is measured with thermal dilatometer by quartz comparison method. after obtaining the relationship curve between temperature and sample elongation from room temperature to softening temperature, we can get transition and sag temperatures through graphing method. in a certain temperature range, after every 1℃ increase in temperature, the elongation of the unit length of sample indicates the mean linear expansion coefficient in this temperature range, and expressed by 10^-7/k.

test equipment: netzsch expansion coefficient tester (dil402 select)

temperature range: -150℃~1000℃

measurement accuracy:better than ±1%.

sample requirement: no visible stripes, bubbles, stones or other impurity with naked eye, stress birefringence up to class 1.

the mean thermal expansion coefficients from -50℃ to 80℃ and from 100℃ to 300℃ are given in the handbook (see figure 2). also, the mean thermal expansion coefficients of every 10℃ from -50℃ to 160℃ are provided.

 figure 2

4.2 transformation temperature  tg

    heat an annealed sample at a certain rate, we can obtain the thermal expansion curve between temperature and sample elongation, as shown in figure 2. the transformation temperature tg is defined as the intersection of two lines that are extrapolated from the low and high temperature sides respectively.

4.3 sag temperature  ts

    the sag temperature ts is defined as the temperature at which annealed sample stops expanding when being heated, as shown in figure 2. the peak temperature on the expansion curve is sag temperature.

4.4 strain point  t₁₀^14.5

     the strain point refers to the temperature at which the glass viscosity is 1014.5 dpa·s. it is also called the lower limit temperature at which inner stress in the glass can be eliminated within several hours.

4.5 annealing point t₁₀¹³

     the annealing point refers to the temperature at which the glass viscosity is t1013 dpa·s. it is also called the upper limit temperature at which inner stress in the glass can be eliminated within several minutes.

4.6 thermal conductivity (λ)

    the thermal conductivity of optical glass refers to the heat transferred through the unit area per unit time divided by the temperature difference of the unit distance under stable heat transfer conditions, and expressed by λ, in unit of w/(m•℃).

    the thermal conductivity listed in this catalog is measured at the temperature of 23±2℃. the measurement accuracy is ±5%.