Materials for Turbine Power Blades, Reinforcements, and Resins - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 78

80

1

7

1. Polyester urethane
2. Polyester urethane
3. Polycaprolactone
4. Polyetherurethane
5. Polyetherurethane
6. Poly bd polyol urethane
7. Poly bd polyol urethane

60

40

4

5

2 3

6

20

0

0 20 40 60

FIGURE 3.9
Comparative.hydrolytic.stability.of.the.polybutadiene.urethane.versus.other.materials..(From.
Li,.H..1998.. Rheological behavior of vinyl ester resin ..Online.at.www.scolar.lib.vt.edu/theses..With.
permission.)

3.8.3.2 Hydrolytic Stability

Polybutadiene. resins. have. a. hydrophobic,. nonpolar. hydrocarbon. back-
bone. that. imparts. hydrolytic. stability. to. products. prepared. from. it.. The.
stability. properties. surpass. those. of. polyurethanes. prepared. from. other.
polyols.that.have.ester.or.ether.linkages,.which.are.more.hydrophilic.and.
easier. to. hydrolyze.. Polybutadiene. resin-based. systems. can. far. exceed.
the. 28-day. requirement. of. the. U.S.. Naval. Avionics. Center. (Indianapolis,.
Indiana).test..For.example,.measuring.hardness.versus.time.at.100°C.and.
95.percent.relative.humidity,.it.has.been.shown.(see.Figure 3.9).that.typi-
cal. polybutadiene-based. urethanes. are. essentially. unaffected,. whereas.
urethanes.prepared.from.other.polyols.actually.liquefy.(revert).under.the.
test.conditions.
The. addition. of. even. moderate. amounts. of. polybutadiene. resin. to. poly-
esterpolyol-based. polyurethane. markedly. improves. the. hydrolytic. stabil-
ity.of.the.cured.polyurethane..Figure 3.10.and.Figure 3.11.show.test.results.
from. two. comparable. polyurethane. systems. containing. a. 24.4. wt.. percent.
polybutadiene. resin/75.6. wt.. percent. polyester. polyol. mixture. and. based.
only. on. the. polyester. polyols.. Changed. tensile. strength. polybutadiene.
/polyester/polyurethane.composites.are.shown.in.Figure 3.10.and.changed.
hardness.of.polybutadiene/.polyester/polyurethane.composites.are.shown.
in.Figure 3.11.

3.8.3.3 High Hydrophobicity

The. core. polybutadiene. aliphatic. chain. imparts. signiicant. hydrophobic.
properties.to.polybutadiene-based.urethane.as.compared.to.the.traditional.
urethanes.. Sand. bounces. off. the. fractures. upon. impact,. while. raindrops.
change.shape.and.continue.to.penetrate.the.substrate..Therefore,.improved.
hydrophobic. properties. are. essential. for. the. protection. from. rain. erosion.