Advancements in Structural Epoxy Adhesives for Wind Blade Assembly

Transcription

1 Advancements in Structural Epoxy Adhesives for Wind Blade Assembly European Coatings Conference "Adhesives for wind and solar technology" Tony Kremer & Christian Claus 3M Renewable Energy Division

2 3M stands for Minnesota Mining & Manufacturing Founded: 1902 in Two Harbors, USA Today s Headquarters: St. Paul, Minnesota From its beginnings as a mining company (= Mining), and later including further processing (= Manufacturing), 3M has now developed into a diversified technology company with worldwide operations. 3M Worldwide Headquarters: St. Paul Sales: $ 26.7 billion Employees: 80,000 Subsidiaries in over 65 countries 3M Europe and Middle East Headquarters: Brussels Sales: $ 6.3 billion Employees: 18,120 Subsidiaries in more than 30 countries 3M Germany Headquarters: Neuss Sales: $ 2.9 billion Employees: 4,790 Subsidiaries at 14 locations

3 3M Renewable Energy Division 3M enables more efficient and more reliable wind turbines, build faster and safer Leveraging 3M s core competencies in the field of films, adhesives, tapes, coatings and the inventive power of 40+ additional corporate technology platforms

4 3M Renewable Energy Division 3M s Renewable Energy Blade Surface Improve resistance to erosion, icing, and fouling Reduce cycle time Improve aerodynamics Reduce interference with radar Easier to maintain Erosion Coatings Functional Coatings Blade Structure Increase strength, decrease weight Lower blade costs Improve turbine efficiency Enhance mechanical properties Improve laminate quality Wind Protection Tapes Sealants Wind Repair Fillers Blade Bonding Blade Processing Aids Reduce cycle time Lower blade costs Faster, more efficient blade throughput Structural Adhesives & Threadlockers Hot Melts Butyl Tape Mold Release Other Consumable Tapes Dry Layup Adhesive

5 Important Notes W1100 = original wind blade adhesive offered by 3M (superseded by W1101) W1101 = current high performance wind blade adhesive from 3M Unless otherwise stated, the results presented for W1100 and W1101 are based on a 4 hour 70 C cure. The information presented here should be considered typical or representative only, and should not be used for specification purposes. The data are also based on a limited number of manufacturing runs. On occasion, 3M does provide internal 3M test data as a service to our customers. 3M does not certify the accuracy or validity of this information and 3M is not responsible for customer s interpretation of or use or misuse of the provided information. For example, customers should not use this information for business purposes, including but not limited to setting test criteria, developing a specification or evidence of meeting a specification, or as a basis for determining if a product is fit for a particular application or will have particular attributes. Product attribute claims should not be based on this information. The information provided is made available on an as is basis. 3M makes no warranty, express or implied, related to this information. 3M shall not be liable for any incidental, special, or consequential damages relating to the use or inability to use this information, regardless of the legal theory asserted.

6 Epoxy Adhesives Structural epoxy adhesives have been successfully used for wind blade assembly for decades Common properties: High shear strength Outstanding adhesion to common wind blade materials Excellent mechanical properties High tensile modulus (rigidity) High ultimate tensile strength Superior elevated temperature properties (onset Tg > 65 C with thermal cure) Moderate exotherm and bond line temperatures Robust mix ratio tolerance Low shrinkage during cure Outstanding environmental resistance

7 Shear Strength Failure during lap shear tests on epoxy composite materials mostly occurs within substrate (interlaminate split) Cohesive failure Cohesive failure Laminate failure Laminate failure

8 Shear Strength Shear strength > 22 MPa and relatively constant over temperature range from -40 C to 50 C GL Requirement

9 Tensile Properties Relatively constant tensile modulus and rigidity over a wide temperature range = cured adhesive glass transition well above maximum 50 C operating temperature Toughened epoxy formulations (such as 3M W1101) exhibit slightly lower tensile strength but higher elongations at break

10 Exotherm Differential Scanning Calorimetry 10 C/min ramp rate Standard epoxy adhesive: Energy release 290 J/g 3M W1101: Energy release 240 J/g Reduced total energy release (exotherm) during cure helps control maximum adhesive bond line temperatures

11 Bond Line Temperature Thick adhesive bond line (20 mm) sandwiched between two plastic slabs to simulate wind blade assembly Peak centerline adhesive temperatures 100 C Thinner bond lines or lower temperature cures will further reduce the peak temperature

12 Shrinkage During Cure 3M W1101 Cure Mix Density increase during cure corresponds to: 1.00% volume shrinkage 0.33% linear shrinkage

13 Environmental Resistance 3M W1101 Essentially no reduction in bond strength after 1,000 hours immersion in a wide variety of solvents, high temperature, high humidity, and other environments

14 Epoxy Adhesives Some recent advancements in structural epoxy adhesives for wind blade assembly can provide process improvements and greater final performance Differentiating properties: Cure speed Strength development Tg development Pot life 3M W1101 Toughness T-peel Floating roller peel Fracture energy + =

15 Strength Development High temperature lap shear test ensures adhesive has cured to sufficient Tg 3M W1101 provides 70 C shear strength of 12 MPa after just 2.5 hours of 70 C cure (4 hours faster than standard epoxy adhesive)

16 Strength Development Two-part epoxy adhesives cure slowly at room temperature, but with an improved curative package, can cure extremely quickly at temperatures of 50 C and higher

17 Tg Development 3M W1101 provides a midpoint Tg of 70 C after just 2.5 hours of 70 C cure (at least 4 hours faster than the standard epoxy adhesive)

18 Tg Development Regardless of exact cure schedule, epoxy adhesives with an optimized curative package can save hours of mold time GL Requirement Minimum onset Tg > 65 C ensures consistent mechanical properties up to 50 C (and probably to even higher temperatures)

19 Pot Life Despite faster cure speeds, both epoxy adhesives (3M W1100 and W1101) retain higher % of original bond strength for longer pot life

20 Toughness (via T-Peel) Peel tests force cohesive split of adhesive itself, providing some indication of internal toughness 3M W1101 provides 3.5x higher T-peel strength compared to the standard epoxy adhesive GL Requirement

21 Toughness (via Floating Roller Peel) Peel tests force cohesive split of adhesive itself, providing some indication of internal toughness 3M W1101 provides 3x higher floating roller peel strength compared to the standard epoxy adhesive at 22 C, and much greater increase at cold temperatures

22 Toughness (via Fracture Energy) Compact tension test measures energy required to propagate a crack through the adhesive, an excellent indication of toughness Toughened epoxy adhesives can provide over 2x higher fracture energy compared to the standard epoxy adhesive

23 Conclusion Advancements in structural epoxy adhesives for wind blade assembly can provide: Faster cure speed (approximately 4 hours faster at 70 C) = mold time savings, manufacture more blades per mold Longer pot life (at least 2 hours at 30 C) Improved mechanical properties Equivalent shear strength 3x peel strength 2x fracture energy = improved crack resistance, fewer repairs, greater performance and durability = improved performance in more demanding applications (longer blades, segmented or modular construction)

24 Thank You for your attention Christian Claus Business Development Manager Wind Energy - Renewable Energy Division 3M Europe, Middle East & Africa christian.claus@mmm.com Tel: More Information