The choice of vulcanising agent (peroxide) to add to the SILBIONE MM SERIES 71791 U depends on the processing method and the conformity with various "Food contact grade" regulations.
The various processing methods are summarised in the table below:
Dichloro- 2, 4 benzoyle Peroxide
at 50 %
at 95 %
2, 5 dimethyl-
2, 5- di
72 % (L)
|MOULDING||compression||-||-||0.6 parts per 100 master batch||0.6 parts per 100 master batch|
|MOULDING||injection||-||-||0.6 parts per 100 master batch||0.6 parts per 100 master batch|
|Extrusion||Hot air vulcanisation||-||0.9 to 1.25 parts per 100 master batch|| || |
|Extrusion||Pressurised steam vulcanisation||6 to 12 bar|| ||0.6 parts per 100 master batch|| |
|Extrusion||Pressurised steam vulcanisation||12 to 20 bar|| || ||0.6 parts per 100 master batch|
|CALANDERING||Hot air vulcanisation|| ||0.9 to 1.25 parts per 100 master batch|| || |
1. Adding peroxide to SILBIONE MM SERIES 71791 U
This operation is performed on a two-roll mixing mill.
à Check that the equipment is scrupulously clean in order to avoid including impurities that would detract from the quality and properties of the SILBIONE MASTER BATCH.
à Plasticise the SILBIONE MASTER BATCH.
Use of a back / front roller speed ratio of between 1.25 and 1.4 ensures sufficient friction to give good plasticising.
à Add the peroxide, then mix by cutting and crossing.
à Cool the cylinders throughout the operation in order to maintain the SILBIONE MASTER BATCH at a temperature below 30 °C;
In the case of catalysis using crystalised dicumyl peroxide, after dispersion it is recommended to heat the elastomer to 50 °C to ensure the fusion of the peroxide, then to cool to 30 ° once fully incorporated.
SILBIONE MM SERIES 71791 U obtained in this way can be processed using all conventional methods in the rubber processing industry used for traditional materials.
In this way, using SILBIONE MASTER BATCH plasticised on a two-roll mixing mill, we could:
à Either roll a sheet to the required thickness from which we will cut preforms for moulding.
à Or cut bands that will be used for example to feed an injection press or to prepare sheets for calendering.
3. Vulcanisation and post curing
Vulcanisation of SILBIONE MM SERIES 71791 U is carried out at temperatures according to the type of peroxide used.
Once cured we remind you that SILBIONE MM SERIES 71791 U must be post cured at 200 °C in forced air ovens with protected heating elements.
The post cure duration depends on the thickness of the parts obtained (moulded, extruded or calendered).Post curing gives the elastomer its optimum characteristics and ensures its conformity with the requirements of the regulations currently in force.
Important comments :
Post curing at a temperature above 200 °C or any accidental increase in temperature (e.g. to around 250-300 °C) can damage parts causing stiffening, cracking or formation of a surface glaze. It is therefore important to use good temperature control together with forced air ventilation.
Non-ventilated ovens or those with insufficient ventilation can cause "reversion" to occur: a reduction in hardness due to the onset of depolymerisation.
|SILBIONE MM 71791/70 U may be stored at temperatures between -5°C / 23°F and 40°C / 104°F for up to 18 months from its date of manufacturing.||Please consult the Safety Data Sheet of this product.|
SILBIONE MM 71791/70 U
SILBIONE MM SERIES 71791 U are silicone rubbers which cure after addition of a vulcanising agent (chosen as a function of the production process).
This series includes three products which differ by their hardness once cured : 40, 60 and 70 Shore A.
Once processed SILBIONE MM SERIES 71791 U , "Food contact and biomedical grade" are intended for:
- applications requiring a material that is non-toxic under normal conditions of use and inert to food products.
For regulated applications, please contact Elkem Silicones to ensure compliance and obtain the relevant statement.
SILBIONE MM SERIES 71791 U , are elastomers comprising polymethylvinylsiloxane gums and silica. They heat cure after addition of an organic peroxide compound. This vulcanisation must be followed by post curing at 200°C.
- Easy processing
- Highly transparent
- Excellent mechanical properties, including high tear strength and a good compromise between tear strength and compression set
- Very good resistance to oxidising agents (oxygen, ozone, UV)
- Very good behaviour for all sterilisation modes
- Very good release properties
- Chemically inert
SILBIONE MM SERIES 71791 U , once catalysed and processed is recommended for the manufacture of the following articles:
Those which enter in contact with food such as :
- Tubes for drink distribution, including potable water
- Baby's bottle tops
- Various technical parts.
- Sections, sleeves, calendered sheets, belts and conveyor belts
Those used in pharmacy such as:
- Tubes and piping for the circulation of liquid or soluble medicines
- Medicine conveyor belts, etc.
Those used for medical applications such as:
- Tubes and piping for extra-corporal circulation
- Oxygenotherapy tubes
- Self-injectable syringe seals
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