CREATING TOMORROW’S SOLUTIONS

FOR EFFICIENT BONDING PASTESONE GRADE BETTER: HDK® H18

ADHESIVES I PyROGENIC SILICA

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HDK® H18 – THE BEST GRADE FOR EFFICIENCy

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To meet the demand for higher energy yields from wind turbines, ever longer rotor blades must be constructed – meaning heavier blade weight. This impacts not only on blade design and materials, but on how the blades are bonded together. The standard adhesives employed are 2-component bonding pastes, which consist of a resin and a curing agent. HDK® pyro-genic silica plays a decisive role in the processing of these two components.

HDK®, GENIOPLAST®, POWERSIL® and ELASTOSIL®

are registered trademarks of Wacker Chemie AG.

The blades of a wind turbine are made by bonding together half-shells composed of different materials.

Lower shell

Shear web Upper shell

Bonding joint

Design Principle of a Rotor Blade

An Innovation that Pays OffIn HDK® H18, WACKER offers a new grade of pyrogenic silica that exhibits a superior level of performance, especially in these bonding pastes. It is readily incorporated into epoxy resins to impart an exceptionally high viscosity and remarkable storage stability. What is more, since comparatively little HDK® H18 is required, the cured adhesive has less tendency to embrittle.

A Partner You Can Count OnWACKER is one of the world’s leading producers of pyrogenic silica and has a product portfolio that is remarkable for its breadth and depth. Driven by innovation, WACKER has a specialty grade for every application, each grade offering a key performance advantage. Why not give us a call? With our research capability and applications engineering, we can find or create an HDK® grade that meets your needs and gives you the all-important edge, whether in processing itself or the final product.

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BETTER PERFORMANCESHORTER PRODUCTION CyCLES

HDK® H18 has been developed specifi-cally for use in polar systems, such as epoxy resins and polyurethanes. It is characterized by a high specific surface area, and has a specific coating which renders it highly hydrophobic. This makes it particularly adept at controlling the rheology of polar systems.

The resultant bonding pastes have an extremely high viscosity and produce non-sag adhesive beads directly upon application. Furthermore, as formulations containing HDK® H18 undergo shear-thinning, users can be assured of perfect processing results.

HDK® H18 has a typical performance advantage of 10 – 15%, e. g. for wind turbine bonding pastes.

The viscosity of HDK® H18 in epoxy resins recovers fast after shear thinning.

Figure 1: Viscosity of Different Hydrophobic Pyrogenic Silicas in an Epoxy Resin

70

60

50

40

30

20

10

0

Vis

cosi

ty [P

as]

■ 10 s-1 ■ 100 s-1 System: epoxy resin with 7% pyrogenic silica dispersed with dissolver at 15 m/s

200

175

150

125

100

75

50

25

0

Vis

cosi

ty [P

as]

10 220 345 425 530 630

■ HDK® H18 ■ HDK® H13L System: epoxy resin with 2.5% pyrogenic silica dispersed with dissolver at 15 m/s

Time [s]

0.1s-1 (conditioning)

10 s-1 (shear thinning)

0.1s-1 (relaxation)

Epoxy + HDK® H17 + HDK® H18 + Competitor 1 + Competitor 2

Figure 2: Viscosity Dependance on Shear Rate

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EFFECTIVE IN LOWER AMOUNTSWHAT COULD BE MORE EFFICIENT?

HDK® H18 also imparts remarkable long-term storage stability and excellent effi-ciency. This means not only that the pro-portion of pyrogenic silica in bonding pastes can be reduced, but also that the cured resin has less tendency to embrittle.

The blend of the two adhesive compo-nents, too, exhibits superior rheological properties at very low HDK® H18 content.

We also offer you optimized grades for other resins and adhesive formulations, too. Just contact us! Together we’ll find a solution – one grade better.

Joint Solutions

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

Vis

cosi

ty [P

as]

Figure 3: Storage Stability of Pyrogenic Silicas with Different Hydrophobic Treatments

HDK® H20 HDK® H13L HDK® H18

■ 1d ■ 7d ■ 30d System: epoxy resin with 8 w% HDK®

Dispersing equipment: dissolver Viscosity measured at shear rate 0.1 s-1 after relaxation

2-component epoxy systems containing HDK® H18 are more viscous than their benchmarks.

2,500

2,000

1,500

1,000

500

0

Vis

cosi

ty [P

as]

Figure 4: Viscosity of 2-Component Epoxy Systems Using Different Pyrogenic Silicas

160 320 480 640 800Time [s]

0.1s-1

1s-1

10s-1 100s-1

0.1s-1

■ HDK® H18 ■ Competitor 1 ■ Competitor 2

System: component A = 92% Epikote 828 epoxy resin / 8% hydrophobic pyrogenic silica (HDK® vs. competitor 1 vs. competitor 2); component B = Epikure 137 amine hardener

0

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WIND POWER – HARNESSED By WACKER

HDK® Hydrophobic Grades – Physicochemical PropertiesHDK® H18BET surface area of hydrophobic silicaDIN EN ISO 9277/DIN 66132

[m²/g] Approx. 120

pH in 4% dispersion (1 : 1 mixture of water/methanol) DIN EN ISO 787-9 4.0 – 6.8Tamped density, DIN EN ISO 787/11 [g/l] Approx. 50Loss on drying, ex works (2 h at 105 °C) DIN EN ISO 787-2 [wt. %] < 0.6Sieve residue DIN EN ISO 787-18 [wt. %] < 0.3Carbon content, DIN ISO 10694 [wt. %] Approx. 4.0 – 5.2Surface modification Polydimethylsiloxy

Our Expertise Goes Far BeyondRotor BladesWACKER is one of the most research-intensive chemical companies in the world and has been developing solutions for sustainable energy supplies for many years. In the wind power sector, we pro-vide highly specialized product solutions for a successful future with renewable energy technologies. Simply call one of our experts or visit our internet site.

HDK®

HDK® is not just used in bonding the rotor blades. It also serves to secure the turbine in its foundations.

ELASTOSIL® CELASTOSIL® C vacuum bags streamline the manufacture in infusion process of the requisite fiber composites. Multiple use of silicone vacuum bags reduces tooling time and waste.

POWERSIL®

POWERSIL® silicone transformer fluid is used in transformers for cooling and to provide electrical insulation, as it ensures largely maintenance-free operation. This fluid also offers excellent long-term heat resistance, high thermal shock resis-tance, and cold-start properties.

GENIOPLAST®

GENIOPLAST® performance additives from WACKER aid the extrusion of wind-turbine control cable jackets and enhance abrasion/scratch resistance during final assembly.

Note: These figures are intended as a guide and should not be used in preparing specifications.

7

6696

e/02

.15

repl

aces

669

6e/0

7.12

The data presented in this brochure are in accordance with the present state of our knowledge but do not absolve the user from carefully checking all supplies immediately on receipt. We reserve the right to alter product constants within the scope of technical progress or new developments. The recommendations made in this brochure should be checked by preliminary trials because of conditions during processing over which we have no control, especially where other companies’ raw materials are also being used. The information provided by us does not absolve the user from the obligation of investigating the possibility of infringement of third parties’ rights and, if necessary, clarifying the position. Recommendations for use do not constitute a warranty, either express or implied, of the fitness or suitability of the product for a particular purpose.

Wacker Chemie AGHanns-Seidel-Platz 481737 München, GermanyInfoline: +49 89 6279-1741info@wacker.com

www.wacker.com

www.wacker.com/hdk

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