Sheet Moulding Compound
Bulk Moulding Compoud
SMC, The process
Equipment
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Mixer (type cowles dissolver) with vessel 400-1000 liter with
drain
Equipment
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Meetering pump to dose thickening agent (MgO paste)
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Pump and piping to connect mixing vessel to SMC machine
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SMC machine
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Glass roving rack and guiding tubes
Raw materials
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Glass roving
Pe/Nylon/PE foil
Unsaturated polyester resin (thickenable with MgO)
Low shrink addive (e.g.solution of polystyrene in styrene)
Low profile additive (PVAc solution or saturated polyester)
Catalyst (TBPB)
Internal release agent (Zinc stearate)
Filler (Calcium carbonate, Dolomite, ATH, Talcum,
Colour paste
Thickening agent (Magnesium oxide)
Starting formulation general purpose SMC
Ingredient
pbw
Ortho phthalic resin
Styrene
Trigonox. C
Poly ethylene powder
Zn stearate
Pigmentpaste
Ca carbonate
MgO paste
100
5
1,5
5
5
5
160
3
Glass 25 mm
25% on paste
Starting formulation for Electrical boxes
Ingredient
Pbw
Polyester resin
Polystyrene solutio
BYK W 996
PBQ 10%
Trigonox C
Pigment paste
Polyethylene powd
Zn stearate
ATH course
ATH fine
MgO paste Luvatol MK 35
65
35
2,3
0,3
1,2
10
4
5
Glass roving 25 mm
27% on paste
100
2,1
50
Starting formulation car body panels
Ingredient
pbw
Pure Maleic resin
65,5
Saturated polyester solution
28
PVAC solution
2
Styrene
4,5
BYK W 996
2,9
PBQ 10%
0,7
Co octoate 1%
1,1
Trigonox C
1
Ca stearate
5,5
Ca carbonate
145
Ca carbonate BLR3
80
MgO paste
2,6
Glass roving 25 mm
28% on paste
Thickening with MgO
Thickening of SMC paste with MgO
200 x 10E6
Viscosity 23° C [mPa.s]
160 x 10E6
120 x 10E6
80 x 10E6
40 x 10E6
0 x 10E6
0
5
10
15
Time [days]
20
25
30
Influence of Moisture
Moisture:
The moisture content of the UP resin,
or filler can play an important role in
the final thickening level
(hydrogen bonds)
Moisture accelerates the thickening
in the initial stage, but stops the
thickening (too) early
Not enough moisture causes higher
plateau viscosity .
Special requirements for UP resin
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High reactivity
Low OH value
Small limits for Acid value
Reproducible thickening with MgO
Low water content
Resin has to be adapted for use in SMC.
Selection in close co operation with resin supplier
The thickening of each batch has to be checked by the
supplier.
The thickening figures have to be mentioned on the batch
report.
Resin specifications example
Special requirement for fillers
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Controlled particle size distribution
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Average particle size <20 micron
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Low humidity (< 0.2%)
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Equal whiteness from batch to batch
Requirements MgO paste
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Supplier have to check every new batch with an approved
standard resin.
Fgures have to be on the certificate of analysis
Standard resin have to be refreshed every 6 month after
checking the thickening efficiency compared with the
previous resin.
Capacity Hydraulic press
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For simple flat parts
For complicated parts
For Class A parts
30-50 kg/square cm
50- 80 kg/square cm
60-100 kg/square cm
Pressure on projected surface of
the mould!!
Moulds
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Material
: Steel
Treatments : Female mould: hardened edges
Both moulds have to be chrome plated
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Placed on hot plate or provided with heating elements
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Clearance at working temperature : 0,05 – 0,2 mm
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Isolation plates between press table surface and heating
plates or heated moulds.
Appearence of ready made SMC
Mould for kitchen sinks
BMC
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Bulk Moulding Compound
BMC Kneader
BMC Kneader
Comparison SMC BMC formulations
Ingredient
SMC
BMC
Polyester resin
LS additive
Catalyst
release agent
pigment paste
Filler
Thickening agent
65
35
1.2
5
10
150
2.5
70 *)
30
1.2
5
10
300
--
Glass fiber 25 mm
Glass fiber 12 mm
*) Thickenability not required
27% on paste
--
-12% on paste
Processing BMC
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Hydraulic Press
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Injection Machine
Head lamp reflectors
Optical engine chasis
Iron foot
Advantages of BMC
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Short cycle times
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Integration of functions
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Electric isolation
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Pigmented
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Excellent processable