In-mould gel-coatingwith a separator layer

Zoltán Gombos and John Summerscales

Plymouth University, UK

Gel-coat

Many applications require a separate surface finishfor cosmetic and/or durability reasons.

This coating, known as the gel-coat, is normally applied to the mould tool before the structural laminate is moulded.

Gel coats should be 0.5-0.6 mm thick[Scott Bader Crystic Polyester Handbook]

Gel-coat application

by hand-painting or spray onto the open mould.

The process releases volatile organic compounds (VOC) into the workplace and the environment.

by mould-opening and flow into the spacehorizontal surfaces increase by the required distance

vertical surfaces see no increase in space

Drivers

Styrene Producers Association hasrecently recommended implementinga 20ppm limit that ensures employee safety.

“ultra-low styrene content spray gelcoat”reported to have achievedan average styrene concentration of 22.3 ppm relative to 54.3 ppm for a “standard gelcoat”

New in-mould process

applicable to RTM, RIFT and similar processes

mould cavity divided by a separator layer

separator has texture toprovide stand-off from mould surface

enhance physical bond to laminate and gel-coat

IPR published as British Patent GB 2 432 336A

IMGC concept

as for RTM, but with two injection ports:

Trilaminate separator layer

textile provides:

• keying to laminate

• defined space for gel-coat

membrane:

• separates two resin systems

two textiles facesbonded either side ofan impermeable membrane

Reference cases for IMGC

Hand-Painted Gel-Coat (HPGC)

In-Mould Surfacing (IMS)Removable silicone shim

AR Harper, Production of composite mouldingsPatent WO2013/132211A1, 12 September 2013.

Processes

flat platessimulated resin transfer moulding (RTM)between two glass plates with central injection points

double opposed tetrahedron mould

Materials used

AHCL Alan Harper Composites Limited, Saltash, United Kingdom. Ccot Centro Tessile Cotoniero E Abbigliamento SpA, Busto Arsizio, Italy. DeIJ De IJssel Coatings BV, Moordrecht, The Netherlands. DSM DSM (formerly Dutch State Mines), Heerlen, The Netherlands. SB Scott Bader, Wellingborough, United Kingdom. SGV Saint Gobain Vetrotex, Litomyšl, Czech Republic

Characterisation

flow to complete fill

aesthetic finish

WaveScan Distinctness of Image (DOI)

instantaneous styrene vapour levels

PhoCheck Tiger Photo-Ionisation Detector (PID)with a 10.6 eV lamp set at 0.349 for styrenereferenced to the isobutylene (C4H8, CAS 115-11-7) calibrationbelow 3000 ppm at 20°C and 90% RH

gel-coat pull-off adhesion strength

EN ISO 4624:2002 standard procedures

Aesthetic finish

Mean DOIDorigon

RTMIMGC

RIFTIMS

HPGC

flat plate 93.2 93.4 92.2

tetrahedron ~ 70.2 75.9

high DOI is goodmaximum DOI is 96

Styrene levelsstyrene level

(ppm)flat tetra

IMGC TWA 0.24(-99.7%)

N/A

IMGC ceiling 36(-96.5%)

N/A

IMS TWA 0.23(-99.2%)

0.37(-98.7%)

IMS ceiling 49(-92.6%)

107(-84.0%)

HPGC TWA 71 29

HPGC ceiling 1017 668

Pull-offadhesiontests

EN ISO 4624:2002

Pull-off adhesion strengths

Strength (MPa)

RTMIMGC

RIFTIMS

HPGC

flat plate 7.8 23.7 27.9

tetrahedron ~ 13.4 16.1

target levels minimum 8 MPaideally > 20 MPa

typical industrial parts 16-20 MPa

failure for IMGC occurs at separator layer interfaces:

Double tetrahedron mould tool

Separator fabric will not conform to complex shape

Conclusions

all processes capable for flat plates

IMGC cannot (yet) handle complex shapesneed more conformable separator layer

need greater cohesion within separator layer

closed mould gel-coatingsignificantly reduces styrene levels

Acknowledgements

This research was funded by the European Union's Seventh Framework Programme

managed by REA-Research Executive Agency ([FP7/2007-2013] [FP7/2007-2011]) under

grant agreement number FP7-SME-2011-1-286520.

Thank you for your attention

any questions ?