DevelopmentofUV-curedsealingcoatingsforbalsa-minimisingpost-appliedresinabsorptioninwindturbineblademanufacture

Phil Barker, Matthew Kennedy and Peter Gillies

Program for today

•  Project background •  UV Curing background •  Raw materials characterisation

–  Quantitative 13C NMR •  Balsa as a substrate •  Understanding the real problem •  Lab/line UV curing correlation •  Possible solutions •  New formulations and results •  Impact on turbine blade manufacture •  General information about co-operative funding for research

projects or product development.

SCAA 2019 2

So what did A&I want us to do??

SCAA 2019 3

Then….

SCAA 2019 4

UV cured coating to seal the balsa

www.diabgroup.com

Minimise finish resin uptake

Blades as light as possible

Plan

•  Characterise coatings raw materials in current product offer •  Characterise substrate •  Understand UV curing production line in Moss Vale •  Optimise photoinitiator package •  Optimise new formulation •  Proof of concept

•  Line trial on UV curing production line in Moss Vale •  Characterise product of line trial

SCAA 2019 5

Background Watching paint dry is fun……..seriously

SCAA 2019

Thermal curing Watching paint dry is fun……..there are so many ways of doing it

Exit Entry

150m/min line speed

SCAA 2019

Background Watching paint dry is fun……..seriously

SCAA 2019

UV curing Watching paint dry is fun……..there are so many ways of doing it

•  Ambient temperature

•  100% solids –  All components react –  No solvents –  Fewer OH&S issues

•  Significant cost benefit vs thermal curing

–  Operating costs –  Maintenance

•  Many and varied applications

Tom Slavinsky – www.metalfinishing.com

SCAA 2019

SCAA 2019 10

UV curing Many unique applications already

UV curing Many unique applications already

SCAA 2019 11

UV curing Many unique applications already

SCAA 2019 12

UV curing Many unique applications already

SCAA 2019 13

UV curing Overall process

•  Photoinitiator –  Type I, type II

•  Reactive base resin –  Diacrylate

•  Other stuff –  Reactive diluent

•  Viscosity control •  Reactivity

–  Synergist (with type II PI) •  Radical generation

SCAA 2019

Substrate Characterisation - balsa Density Variation

100 mm

610 mm

1220 mm

200 mm

SCAA 2019

Method UV Sealing coat applied

Coated with UV sealer

SCAA 2019

18

Method Resin application

SCAA 2019

Heart of the problem Resin bleed-through

SCAA 2019 19

Tracheids, rays and sap channels

Resin bleed through

—  Each resin spot corresponds to an open sap channel

—  The sealing coating does not seal !

—  As the channels are 200µm (±50), the sealer cannot bridge this gap.

—  This picture was a ‘good’one !!

The Problem Underneath after sealing and resin application

Balsa

Sealing coat

Post-applied resin

Sap Channel – Circular

150-250 µm Tracheids – Hexagonal – 30-70 µm

Ray Cells – Rectangular – 13 µm

SCAA 2019

Visually Differing coating masses (in duplicate)

Qualitatively, resin bleed-through shows that higher coating mass decreases resin absorption

Sealer coating mass

Resin bleed

From this background work, we developed two methods for estimating resin bleed

through…..

SCAA 2019

Method 1 Epoxy film build

Higher sealing coat mass shows increased epoxy DFT

100 mm

200 mm

Scrim

Film buildmeasurement

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

21 26.5 43.5 53.5

VC6 Standard Fi

lm B

uild

(mm

) Coating (g/m2)

SCAA 2019

Method 2 Resin absorption

Resin absorption calculated by mass gained shows higher coating mass decreases resin absorption

0

100

200

300

400

500

600

700

800

21 26.5 43.5 53.5

Standard Formulation R

esin

Abs

orpt

ion

(g/m

2 )

Coating (g/m2)

Blade manufacturer in-house method

—  Weigh sealed balsa piece (a)

—  Apply Epoxy and cure

—  Carefully sand epoxy back to balsa surface

—  Reweigh (b)

—  b – a = absorbed resin mass

SCAA 2019

Novel formulation concepts Lab evaluation

•  Base formulation : epoxy acrylate, diluent, synergist, PI package (BP + Irgacure 184) •  Optimise PI concentration •  Replace 184 with BAPO – type initiator

•  New concept : employ UV-formulation compatible materials (some reactive, some not) –  Matting agents –  Texturing agents –  At unusual concentrations –  Block sap channels

SCAA 2019

Eureka moment ! Incomplete drawdown of #2+B

SCAA 2019

Microscopy Method development

Unsealed balsa Sap Channels clearly visible

Contrast is poor Which channels are filled? Which channels are empty?

Look closer

SCAA 2019

Microscopy Close up of the interface

SCAA 2019 30

Microscopy Method development

Platinum sputtering of whole surface

Contrast is improved Can see full and partially filled channels

Look closer

Now put on your 3D specs !!!

SCAA 2019

Microscopy Method development

SCAA 2019

#2 + B

SCAA 2019 33

Sealing coating applied

Post applied resin on top

Target no resin bleed-through

Sap channel should be EMPTY

Now put on your 3D specs !!!

#2 + B

SCAA 2019 34

No sealant

SCAA 2019 35

No sealing coating

Post applied resin on top

Resin bleed through

Sap channel should be FULL

No sealant

SCAA 2019 36

Top of column

Resin fills sap channel

Air bubble

Resin bleed through

No sealant

SCAA 2019 37

Bottom of column

Resin plugs sap channel

Resin bleed through

Sap channel is FULL

Sap Channels sealed (yippee!!) But these were laboratory prepared samples now we must scale up

20cm x 10cm 120cm x 60cm

50ml 10L

SCAA 2019

Limited by constraints and variables…

•  Balsa Sheets 120mm x 60mm

•  Only 20 sheets available !!!!

•  Decided upon 4 formulations, to produce 5 sheets of each at different coating masses

•  A&I base formulation, but with reduced photoinitiator (4%)

•  Matt1 – A&I base (4% photoinitator) with 1% (mass basis) B (+ reduced reactive diluent)

•  Matt2 – A&I base, 4% optimised photoinitiator package, 0.5% Additive B + 0.5% additive C

•  Matt3 – A&I base, 4% optimised photoinitiator package, 1.0% Additive C

•  Scale up all formulations from 50g to 10Kg

•  Coated Sheets to go to composite company in Sweden for testing

Plan for line trial

SCAA 2019

Production line trial June 16th

SCAA 2019

Production line trial Line overview

SCAA 2019

Production line trial Applicator with nip feed

SCAA 2019 42

SCAA 2019 43

Production line trial Balsa sheet going from applicator to 1st UV station

Production line trial June 16th

Clear sample labelling on all 4 edges

18 sheets out of 20 for Sweden

We retained 2 for our testing

‘Matt 3’ 24g/m-2

SCAA 2019

Promising after resin application Comparison with VC6 at 40g.m-2

Original system shows considerable resin bleed

Clearly reduced resin bleed from ‘Matt 3’ at similar coating mass

Must do the microscopy to confirm

Original A&I system ‘Matt 3’ system

SCAA 2019

Promising after resin application Section and Pt sputter

Post-applied resin

‘Matt 3’ coating on both sides

Close up….

Now put on your 3D specs !!!

SCAA 2019

SCAA 2019

SCAA 2019

Blade manufacturing

Turbine blade construction

Balsa core

Resin infusion

Picture from Composites World June 2010

When our whole product sheets were tested under vacuum infusion conditions in Europe……

200g/m2

Order of magnitude improvement over uncoated balsa

SCAA 2019

•  At least 2 reformulated systems which show no resin absorption/bleed and excellent production line application properties

•  Improved photoinitiator package

•  Detailed Report

•  Recommendations for future work

•  All in 7 months [official project timeline 6months (+2)]

What have we delivered ?

SCAA 2019

Significant result for blade development Research in USA

SCAA 2019 53

All-glass Baseline Blade: 114 ton weight

Carbon Design Studies: 74 ton weight

Advanced Core Material: 59 ton weight

Funding Innovation Connections Program

•  Bruce Thomson Business Development Manager

•  Professor Di Jolley

•  Phil and Matt

SCAA 2019

Funding State government programs

Supporting business in New South Wales

Eligible businesses can use a TechVoucher to: • seed a research project in partnership with a BBIP delivery partner • support a research project that will lead to an application for an Entrepreneurs' Infrastructure Programme Research Connections or Accelerating Commercialisation, or other similar scheme • fund access to research facilities and equipment such as electron microscopes, medical imaging, e-research supercomputers, nanofabrication, marine and climate infrastructure, and other BBIP delivery partner facilities • fund product or process design activities, such as engineering or technical design expertise to determine prototype structure, function and/or materials • access technical assistance • trial production runs or processes to demonstrate technical concepts • validate or demonstrate technical capabilities of a product, process or technology • fund toxicology studies on materials you have invented, or wish to incorporate into a new product.

TechVouchers

www.industry.nsw.gov.au

SCAA 2019

Funding Australian Research Council Linkage Scheme

3-year funding for major research project arc.gov.au

•  Must be in an area of national interest/priority •  Rigorous selection process

SCAA 2019

•  Enthusiasm and support of Peter and the team at A&I Coatings

•  Professor Dianne Jolley (now UTS) for her astute mentorship, management and communication skills

•  Head of School of Chemistry and Molecular Bioscience

•  To all the Conference organisers for inviting me to speak

•  To all you attendees – Thank you.

Acknowledgements

SCAA 2019