Top Issues and Fixes in Halogen-Free Cable Production

Flame retardant materials like magnesium hydroxide and aluminum hydroxide are essential in producing halogen-free flame retardant cable materials, widely used in the cable industry. Over the past decade, we’ve assisted numerous customers—primarily from the cable sector—in overcoming production challenges related to cable compounds and cable extrusion. Many of these issues are recurring, so we’ve compiled the most common problems and their solutions below to help you optimize your processes.

Before diving into the problems, let’s explore the key differences between LSZH (Low Smoke Zero Halogen) cable compounds, PE (Polyethylene) compounds, and PVC (Polyvinyl Chloride) compounds.

Differences Between LSZH, PE, and PVC Cable Compounds

Understanding these distinctions is crucial for addressing production challenges effectively:

1. Mechanical Properties

• LSZH Compounds: Lower tensile strength and elongation at break compared to PVC and PE compounds.

• Oxygen Index: Higher than PVC, but flame retardant performance is weaker due to poor self-extinguishing ability in halogen-free compounds.

• Density: Higher due to significant flame retardant additives.

2. Extrusion Process Variations

Compared to PVC and PE compounds:

• Shearing: LSZH materials experience greater shear; use a special screw with a low compression ratio (1:1.1–1.5), especially for large-diameter extruders.

• Load: Higher motor current due to increased load; opt for extruders with powerful motors.

• Output: Lower glue output and slower extrusion speed.

• Temperature Control: Difficult to manage—excessive heat causes surface air holes or rough cut edges.

These differences set the stage for troubleshooting halogen-free LSZH/HFFR cable material processing issues.

Common Issues and Solutions in LSZH Cable Production

Below are the top challenges encountered during halogen-free cable manufacturing, along with actionable solutions based on our experience.

Issue 1: Rough Cable Surface and Small Holes at Cut Section

Possible Causes:

• A) Damp material.

• B) Excessive process temperature causing flame retardant decomposition.

Solutions:

• A) Pre-dry the material using a blowing device at 70–80°C for 2–3 hours.

• B) Lower screw speed or reduce body and mold temperature.

Issue 2: High Motor Current, Slow Production Speed, or Screw Stalling

Possible Causes:

• A) Incomplete plasticization or melting, leading to high shear and frictional heat.

• B) Excessive back pressure.

Solutions:

• A) Raise the process temperature, particularly in the feeding zone.

• B) Use a smaller mesh filter screen or remove the filter and manifold if needed.

• C) Adjust screw speed to maintain an optimal current level.

• D) Switch to a screw with a low compression ratio.

Issue 3: Fluctuating Cable Outer Diameter During Extrusion

Possible Causes:

• A) Unstable extruder discharge.

• B) Inconsistent traction.

• C) Variations in cable core outer diameter.

Solutions:

• A) If motor current and extrusion speed permit, lower extruder temperature or add a filter screen/shunt plate for stable material thrust.

• B) Verify mold compatibility and select an appropriate mold core and sleeve.

• C) Repair the traction system to ensure consistency.

• D) Control semi-product outer diameter in prior processes.

Conclusion and Next Steps

These are some of the most frequent challenges in halogen-free LSZH cable production, along with proven solutions drawn from our expertise. By addressing these issues—whether it’s improving extrusion processes, selecting the right screw compression ratio, or stabilizing cable diameter—you can enhance efficiency and product quality.

Have additional insights or questions? Feel free to contact the author to discuss further or share your experiences. Let’s optimize your flame retardant cable manufacturing together!

Halogen-Free Lszh Cable Manufacturing Raw Material Supply from KMT

Hexagonal Magnesium Hydroxide

Synthetic magnesium hydroxide, halogen free flame retardant for PE, PP, POE, EPDM, EVA, XLPE, PVC, TPU, PA and ABS based compound. HP series products comply with RoHS requirements and have REACH certification.

BET controlled Easy dispersing Lower compounding torque

Precipitated Magnesium Hydroxide

Precipitated superfine magnesium hydroxide coated by KMT patent formula, can easy dispersing in PP, PE, EVA, POE, EPDM, XLPE, PA, ABS compound.

High purity High whiteness Low moisture contentHigh bulk densityEasy flow

Hydromagnesite

Nature own fire retardant. Hydromagnesite Chemical formula: [3MgCO3 · Mg(OH)2 · 3H2O] This unique natural minerals is also known as HMH. It is a proven fire retardant filler in a wide range of polymers and rubbers such as EVA, POE, polyethylene (PE), polyvinyl chloride (PVC), ethylene-propylene diene monomer (EPDM) and Nitrile Rubber (NBR).

High LOI Good charring effect Easy flowAnti-bridg

Natural Brucite Powder

The production of natural Brucite is started in the year 2008. We offer high purity and high whiteness Brucite powder. B series Brucite is widely used in PVC cable, HFFR cable compound, flame retardant panel, aluminum composite panel, flue gas desulfurization, wastewater treatment, magnesium fertilizer, etc.

BET controlled Easy dispersing Lower compounding torque

Aluminum Hydroxide

High purity Aluminum Hydroxide can be used as halogen free flame retardant for plastic and rubber industry due to its well distributed granularity, good stability, non toxic and non-polluting.

High-purity Regular crystal structure Low oil absorption