Cross-Linkable Compounds - FAQ

Polidan® EC, Polideimme® G, Cogegum® GFR and catalyst products

Frequently Asked Questions

Are products packaged under vacuum?

No vacuum is applied to each bag during packaging. Bags have an extraction valve on their bottom that allows air to exit under the weight of the material itself, so that a partial vacuum is achieved after some hours from the packaging; for this reason, often bags of the top rows of the pallet are softer than bags of the bottom rows. It is just required that air from outside doesn’t enter the bag. Liners in boxes are not under vacuum

Can very soft bags be used?

If the bag is much softer than usual, then it is probably torn, and, in this case, air entered the bag and the material cannot be used.

Why are Catalyst MB packaged in multilayer moisture-proof bags but not sealed?

Catalyst MB are not hygroscopic as silane grafted compounds, and don’t require to be kept out of contact with the ambient air during storage.
Catalyst CT/5 and CT/7 series are an exception, and its high concentration of antioxidants makes it hygroscopic

May I transfer and store the material in a different packaging or in a silo?

No, in order to prevent moisture absorption the material must be stored in its original package until its use. It cannot be stored in a silo, unless for small volumes (200 kg max) to be used within the end of the day

If a bag is torn or broken, can I recover the material from this bag mixing it with other material?

No, if a bag is broken the material has probably already adsorbed enough moisture to give pre-crosslinking problems during extrusion. If you dilute the broken bag material with other material from untorn bags, you will probably propagate the crosslinking problems to the whole batch

Can I store bags or boxes already partially used?

No, once the bags or boxes are opened, their content must be completely used before the end of the day. It can be recovered just closing the bag by welding the multilayer bag or liner, and the material must be used anyway within 2-3 days

Does the Catalyst MB storage follow the same precautions as the grafted base?

Catalyst MB must be stored in the same environmental conditions as the grafted base, but if a bag is partially used it can be closed with adhesive tape and used also after in the next production campaigns

If the material is stored from a long time, should I pre-dry it to improve processing?

No, silane grafted materials must be not pre-dried at any time. Pre-drying would mean to start the crosslinking process in the material before its extrusion, in a small amount since the absence of the Catalyst MB, but enough to make the extrusion problematic

Must the Catalyst MB be pre-dried?

Normally Catalyst MB doesn’t need any pre-drying; anyway, a pre-drying treatment made at a temperature of 60-70°C (140-158°F) for 4-6 hours does not determine any degradation of the material. Pre-drying of the Catalyst MB is suggested for long storage (over 6 months) in humid environment

How critical can be the storage temperature on material processing?

Material stored at very low temperature, below 10°C, may show some difficulty to melt and homogenize properly during processing, particularly on short extruders (less than 24 L/D); this may occur mainly for Cogegum® GFR grades, and, in case, it is suggested to transfer the bags in a warmer ambient the day before the extrusion. Don’t warm-up the material in a oven! Storage temperature above 30°C (86°F) may have an influence just on Polidiemme® G softer grades, making granules a little sticking; no effect on Polidan® EC and Cogegum® GFR grades

Is the use of a gravimetric feeder mandatory to dose the Catalyst MB?

No, volumetric feeder can also be used; the maximum tolerance on nominal dosage should be within ± 10%.

Can the same Catalyst MB be used for different silane grafted compounds?

Each Catalyst MB is compatible with each compound, but dedicated Catalyst MB, as indicated in the TDS of each compound, can guarantee the optimal performances in terms of material processing and properties

How can the characteristics of the extrusion equipment impact the Catalyst MB dosage?

The nominal dosage of Catalyst MB has been optimized to fit with a standard screw with double-flight PVC design up to 25 L/D for Polidan® EC and Polidiemme® G grades, and a low compression screw up to25 L/D for Cogegum® GFR grades; longer screws (28-30 L/D) may require the Catalyst MB dosage to be reduced to 2/3. Screws shorter than 20 L/D must be avoided

How can the dosage of Catalyst MB impact material crosslinking and processing?

The higher the Catalyst MB dosage, the higher is the reactivity of the system. Hence crosslinking rate will be higher, as sensitivity to pre-crosslinking during extrusion. A trimming of the dosage respect nominal value may be required to balance a safe processing with an acceptable cross-linking rate

Which properties depend on the Catalyst MB dosage, other than crosslinking rate?

Catalyst MB also contains the antioxidant package to prevent the long term material degradation; its reduction means to reduce also protection against ageing; as first estimation, protection to ageing reduction is proportional to the Catalyst MB reduction

Is it preferable to pre-dry during blending?

No, the silane grafted compound must not be pre-dried at any time; this would be cause of pre-crosslinking and make possible lumps on cable. Catalyst MB normally doesn’t require pre-drying, but it’s not damaged by it

Can we use PE colour MB for Cogegum® GFR grades?

Colour MB based on PE carrier are compatible with Cogegum® GFR grades, but it may require a higher dosage than MB based on EVA carrier to match the same colour; since PE burns easily, it may impact also on the cable flammability

How much can the typical color of the material affect color match?

Polidan® EC and Polidiemme® G grades normally don’t affect the colour matching; Cogegum® GFR grades, due to the high content of white filler, must be evaluated when the cable is fully cooled down, since, when the cable is still warm, color appears significantly lighter

In case, can we use color MB for PVC or PU or polyesters, etc.?

No, it is mandatory to use colour MB based on polyolefin carrier; MB for other kinds of material may give serious problem of bad dispersion and incompatibility of unwanted additives