Transcript Education, Professional Development and Recognition

In-mould gel-coating
with a separator layer
Zoltán Gombos and John Summerscales
Plymouth University, UK
Gel-coat
Many applications require a separate surface finish
for 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 space
horizontal surfaces increase by the required distance
vertical surfaces see no increase in space
Drivers
Styrene Producers Association has
recently recommended implementing
a 20ppm limit that ensures employee safety.
“ultra-low styrene content spray gelcoat”
reported to have achieved
an 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 to
provide 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
two textiles faces
bonded either side of
an impermeable membrane
textile provides:
•
keying to laminate
•
defined space for gel-coat
membrane:
•
separates two resin systems
Reference cases for IMGC
Hand-Painted Gel-Coat (HPGC)
In-Mould Surfacing (IMS)
Removable silicone shim
AR Harper, Production of composite mouldings
Patent WO2013/132211A1, 12 September 2013.
Processes
flat plates
simulated 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 styrene
referenced to the isobutylene (C4H8, CAS 115-11-7) calibration
below 3000 ppm at 20°C and 90% RH
gel-coat pull-off adhesion strength
EN ISO 4624:2002 standard procedures
Aesthetic finish
Mean DOI
Dorigon
RTM
IMGC
RIFT
IMS
HPGC
flat plate
93.2
93.4
92.2
tetrahedron
~
70.2
75.9
high DOI is good
maximum DOI is 96
Styrene levels
styrene level
(ppm)
flat
tetra
TWA
0.24
(-99.7%)
N/A
ceiling
36
(-96.5%)
N/A
TWA
0.23
(-99.2%)
0.37
(-98.7%)
ceiling
49
(-92.6%)
107
(-84.0%)
HPGC
TWA
71
29
HPGC
ceiling
1017
668
IMGC
IMGC
IMS
IMS
Pull-off
adhesion
tests
EN ISO 4624:2002
Pull-off adhesion strengths
Strength
(MPa)
RTM
IMGC
RIFT
IMS
HPGC
flat plate
7.8
23.7
27.9
tetrahedron
~
13.4
16.1
target levels
typical industrial parts
minimum 8 MPa
ideally > 20 MPa
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 shapes
need more conformable separator layer
need greater cohesion within separator layer
closed mould gel-coating
significantly 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 ?