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Equipment
Meetering pump to dose thickening agent (MgO paste)
Pump and piping to connect mixing vessel to SMC machine
SMC machine
Glass roving rack and guiding tubes
Raw materials
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 100Styrene 5Trigonox. C 1,5Poly ethylene powder 5Zn stearate 5Pigmentpaste 5Ca carbonate 160MgO paste 3
Glass 25 mm 25% on paste
Starting formulation for Electrical boxes
Ingredient Pbw
Polyester resin 65Polystyrene solutio 35BYK W 996 2,3PBQ 10% 0,3Trigonox C 1,2Pigment paste 10Polyethylene powd 4Zn stearate 5ATH course 50ATH fine 100MgO paste Luvatol MK 35 2,1
Glass roving 25 mm 27% on paste
Starting formulation car body panels
Ingredient pbw
Pure Maleic resin 65,5Saturated polyester solution 28PVAC solution 2Styrene 4,5BYK W 996 2,9PBQ 10% 0,7Co octoate 1% 1,1Trigonox C 1Ca stearate 5,5Ca carbonate 145Ca carbonate BLR3 80MgO paste 2,6
Glass roving 25 mm 28% on paste
Thickening of SMC paste with MgO
0 x 10E6
40 x 10E6
80 x 10E6
120 x 10E6
160 x 10E6
200 x 10E6
0 5 10 15 20 25 30Time [days]
Vis
cosi
ty 2
3°C
[mPa
.s]
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)
Not enough moisture causes higher plateau viscosity .
Moisture accelerates the thickening in the initial stage, but stops the thickening (too) early
Special requirements for UP resin
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.
Special requirement for fillers
Controlled particle size distribution
Average particle size <20 micron
Low humidity (< 0.2%)
Equal whiteness from batch to batch
Requirements MgO paste
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
For simple flat parts 30-50 kg/square cm For complicated parts 50- 80 kg/square cm For Class A parts 60-100 kg/square cm
Pressure on projected surface of the mould!!
Moulds
Material : Steel
Treatments : Female mould: hardened edgesBoth moulds have to be chrome plated
Placed on hot plate or provided with heating elements
Clearance at working temperature : 0,05 – 0,2 mm
Isolation plates between press table surface and heating plates or heated moulds.
Comparison SMC BMC formulations
Ingredient SMC BMC
Polyester resin 65 70 *)LS additive 35 30Catalyst 1.2 1.2release agent 5 5pigment paste 10 10Filler 150 300 Thickening agent 2.5 --
Glass fiber 25 mm 27% on paste --Glass fiber 12 mm -- 12% on paste
*) Thickenability not required