Sheet Moulding CompoundBulk Moulding Compoud

SMC, The process

Equipment

Mixer (type cowles dissolver) with vessel 400-1000 liter with drain

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 with MgO

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.

Resin specifications example

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.

Appearence of ready made SMC

Mould for kitchen sinks

BMC Bulk Moulding Compound

BMC Kneader

BMC Kneader

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

Processing BMC

Hydraulic Press

Injection Machine

Head lamp reflectors

Optical engine chasis

Iron foot

Advantages of BMC

Short cycle times

Integration of functions

Electric isolation

Pigmented

Excellent processable