We are trying to sheath PVC based FRHF Compound in our 100mm rosendahl extruder and have experienced very low output and excessive load on the extruder. The material also seems to degrade. How to solve this problem.

Extruder details: 100mm screw, L/d ratio: 24, Crosshead: 30/40, The clearances of the screw-barrel have incereased.
Cable dia: 13mm, Sheath Thickness: 1.5 mm

Hello Shekhar,

We need to know the type of screw you have in this extruder. Are you indeed using a PVC screw?

Likewise, what does the compound manufacturer recommend as the proper screw design for pumping with this compound?

Sincerely,

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

hi all,
First of all,you can't manufacture halogen free flame retardant compound by using pvc.Because pvc has chlorine just decrease of smoke.I think you are using ATH in your formula that effects to output badly.You should use Sb2O3 instead of ATH, approximately 3-4%

Hello serdar1970,

I suspected Shekhar didn't mean zero halogen content because he directly referenced PVC.

For the rest of us non-chemistry types:


Antimony trioxide (SbO3) is a highly effective flame retardant. However, Answers.com provides the following toxicology information for antimony trioxide:

"Antimony trioxide is weakly absorbed by the digestive system, and the main route of exposure is by inhalation of the dust. The elimination of antimony from the body is slow, leading to a risk of chronic toxicity. Acute poisoning is rare, and the signs are fairly non-characteristic (vomiting, abdominal pain, irritation of the mucous membranes, diarrhea, cardiac irregularities).

Chronic poisoning by antimony trioxide is sometimes found in exposed workers. The main signs are irritation of the respiratory tract and of the skin and a characteristic pneumoconosis which is visible on chest X-rays.

Antimony trioxide is known to pass into breast milk and to transverse the placenta. Exposed female worker have a higher incidence than usual of menstrual problems and of late-term miscarriages. Their children develop slower than usual during the first twelve months of life."


Alumina trihydrate (ATH) is the world’s most widely used flame retardant. ATH contains no halogens or heavy metals and it is far more environmentally friendly than flame retardants based on antimony metal or chlorinated and brominated (halogenated) compounds.

Alumina, aluminium hydroxide and aluminium compounds in general have very low levels of toxicity except when there are high exposure levels or unusual routes of exposure.

Sincerely,

Peter J. Stewart-Hay (Forums Moderator)
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Dear All,

Thanks for the inputs, having discussed the same with my team members, actually the compound being used by us is EVA based Halogen Free Low Smoke Flame Retardant compound. The screw being used by us is suitable for polyethylene based compounds.
The problem in extrusion of the same may now be re-considered by your goodself for suitable corrective action.

Regards

Shekhar

Sheks

hi again,
hffr cable production is slower than pvc cable production approx %25-40.You should use low compression screw 1:1,2 to increase the output or should use different hffr compound which has a mgoh2(flame retardant).
www.scapapolymerics.com megolon is a trade mark but it is expensive.