Processing of moulding compounds

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Processing of free-flowing thermosetting compounds
1. Injection moulding

Thermosetting moulding compounds may be processed on all standard injection moulding machines equipped with a thermoset unit. Standard screws for thermosets normally have a compression of 1:1.2 and the length:diameter ratio usually between 15 - 19. The cylinder should be equipped with a minimum of two separately regulated heating zones.

2. Press processing

Although; in principle, all free-flowing thermosetting moulding compounds are suitable for press processing, better results are obtained using those compounds that have been developed, with respect to their flow-curing behaviour, for this procedure. Dosage can be carried out by weight or by volume, i.e. the material can be processed directly, as tablets (with or without pre-heating) or can be preplastified prior to use. The temperature and pressure within the closed mould forces the softened material into the cavities. After the required curing time, which is dependent on the wall thickness of the processed part, mould temperature and the reactivity and pre-treatment of the moulding material, the finished part is removed from the mould. Depending on the part size, This process can be carried out manually, semi-automatically or automatically. Press processing is used to produce parts with low filler orientation and low shrinkage. Press moulds nowadays normally are constructed with a bleed out. These guarantee the precise production of finished parts due to ideal compaction. The factors concerning mould design and mould steel are the same as for injection processing.

3. Processing of Raschig moulding compounds

Please see table below for the parameters for injection moulding and press processing of Raschig moulding compounds:

 

Press Processing:

Moulding compound	Ampal	Melopas	Ralupol	Resinol
Mould temperature	160-180 °C	160-180 °C	165-180 °C	165-180 °C
Internal pressure	>= 200 bar	>= 200 bar	>= 200 bar	>= 200 bar
Curing time per mm wall thickness	20 - 50 s	20 - 50 s	10 - 35 s	20 - 50 s

 

Injection moulding:

Moulding compound	Ampal	Melopas	Ralupol	Resinol
Cylinder temperatures	Room temp.	Room temp.	Room temp.	Room temp.
Loader	20 - 25 °C	20 - 25 °C	20 - 25 °C	20 - 25 °C
Zone 1 (screw zone)	50 - 75 °C	70 - 90 °C	50 - 75 °C	50 - 75 °C
Zone 2 (Nozzle zone)	80 - 100 °C	90 - 100 °C	80 - 100 °C	80 - 100 °C
Compound temperature leaving nozzle	100 - 115 °C	100 - 115 °C	100 - 115 °C	100 - 115 °C
Screw speed	80 - 120 RPM	80 - 120 RPM	70 - 120 RPM	70 - 120 RPM
Backing up pressure	8 - 12 bar	8 - 12 bar	10 - 15 bar	5 - 15 bar
Dwell/injection pressure	80 - 100 %	60 - 80 %	60 - 80 %	50 - 70 %
Dwell pressure time	10 - 20 s	10 - 15 s	10 - 20 s	2 - 8 s
Mould temperature	165 - 180 °C	165 - 180 °C	165 - 180 °C	165 - 180 °C
Curing time	10 - 100 s	10 - 100 s	10 - 100 s	10 - 100 s

 

Remarks: After injection time and dwell pressure time, the injection unit should be drawn back.

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