Materials for Turbine Power Blades, Reinforcements, and Resins - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 83

10000

1000

100

10

20 30 40 50

Styrene Content (wt%)

60

FIGURE 3.13
Viscosity.of.uncured.vinyl.ester.resins.at.25 o C.(Mn.=.690.g/mol).

3.9.4 Effect of Temperature

The.viscosity.of.epoxy.or.vinyl.ester.resins.decreases.as.temperature.increases..
The.Andrade.equation.relates.the.viscosity.to.temperature.as.follows:

. η.=.A10 B/T. (3.5)

. logη.=.logA.+.B/T. (3.6)

where. A. and. B. are. constants. characteristic. of. the. polymer. and. T. is. the.
absolute.temperature..The.viscosity.of.a.polymer.at.a.given.temperature.
can. be. estimated. by. knowing. the. viscosity. at. two. other. temperatures..
This. knowledge. also. calculated. the. constant. A. and. B. and. determina-
tion.of.viscosities.at.other.temperatures..The.Andrade.equation.holds.for.
many.polymer.solutions.and.polymer.melts.well.above.their.glass-transi-
tion.temperatures. 6
The.concentrated.vinyl.ester.resins.(low.styrene.content).with.two.different.
molecular.weights.(Mn.=.690.g/mol.and.Mn.=.1,000.g/mol).were.measured.
at.temperatures.of.25°C,.35°C,.50°C,.75°C..Plots.of.logη.versus.1/T.are.shown.
in.Figure 3.14.. It.was.found.that.logh.versus.1/T.was.a.straight.line.for.all.
tested.resins.for.temperature.ranging.from.25.to.75°C,.which.are.well.above.
Tg.(glass.solidify.temperature).
The. constants. A. and. B. are. also. determined. and. listed. in. Table 3.15.. As.
styrene.content.increases,.the.viscosity.of.the.vinyl.ester.resins.become.less.
dependent.on.temperature,.as.concluded.by.the.decrease.in.both.log.A.and.B.