Our SPL-ZHFR-7000 XL is a Zero Halogen, Low smoke, Flame Retardant, Silane grafted, moisture curable by addition of a catalyst master-batch cross-Linkable Compound used for Power, Signal, Communications and Building Cables applications.

Our compound can run at high line speed for insulation /sheathing applications. The material contains metal deactivator hence suitable for direct insulation on copper conductor.

 

The key benefits for using our SPL-ZHFR-7000 XL are

• Good mechanical and Electrical Properties
• Zero Halogen acid gas generation
• Long-term reliability
• Good flame retardancy and low smoke

Our compound works on reactive extrusion technology, we introduce Catalyst (CTMB-09) with a dosage is 3 - 5% by weight and blending must be done just before using (2-3 hours max.), preferably in the extruder hopper and it does not require any pre-drying. This compound consists specialty thermoplastic polymers, inorganic fillers and additives helps in achieving good processing and physical properties.

Shakun’s SPL-ZHFR-EXP-422 XL is a Zero Halogen, Low Smoke, Flame Retardant, Silane Cross-linkable Compound and Polyolefin based for PV insulation and sheathing applications.  It has good electrical properties and high thermal stress resistance.

 

Solar cables are installed in an open environment, they inherently have to be resistant adverse climate conditions as well as need to perform in difficult climate conditions with a service life of 25 years and more depending on the cable specification. This adds to making the compound highly durable and efficient to perform in these conditions.

OUR COMPOUNDS key properties are as follows:-

•   Good abrasion resistance
•   Zero Halogen acid gas generation
•   Long-term reliability
•   Good flame retardancy and low smoke

We have also received TUV approval for this compound as per BS EN 50618:2014 under the brand name of PvTek cable. Our compound is versatile, this single compound can be used for Insulation as well as for sheathing. The most critical test to pass for solar cable application is Thermal Endurance test for 20,000 hours from temperature starting from 120 and going up to 200.

 

As regards to the processing guidelines we recommend using Catalyst (CTMB-11 AOX) with a dosage of 4 to 5% by weight and blending must be done just before using (2- 3 hours max.), preferably in the extruder hopper. Catalyst doesn’t need any preying.

Extrusion temperatures of 110 - 150°C on Extruder Barrel Zones, 155°C on neck, 160°C on head and 165°C on Die are recommended.  

Abstract

The Cable industry is one of the most challenging markets because of diversified applications that lead too many cable constructions, followed with a market segment with stringent technical demands which are technologically driven.

The presented research paper will include the single and most popular segment commonly known as Building wire. Building wire is always been popular with PVC- Halogenated material containing chlorine and bromine which produces high density smoke during fire and causes death.  This paper is mainly focused on the high demands of non- halogenated flame retardant compounds replacing PVC for building wire application.

European regulations for RoHS, REACH and WEEE are impacting material choices for wire/cable in other global regions. Technologies for replacing PVC with halogen free, flame retardant (HFFR) compounds are moving beyond the first generation candidates. In addition, low smoke, halogen free (LSHF) compounds are driven by fire safety for both Health & Environment.

Key words: - Building wire, Halogenated, non-halogenated, Polyvinylchloride (PVC), Halogen free flame retardant (HFFR) compounds

1. Introduction

Major accidents which have resulted in the deaths of many innocent people, have taught us that the safety of the occupants and users in public, commercial and industrial environments is of paramount importance. Every possible safety feature designed to prevent and protect against loss of life and damage to property should be specified and installed.

Polyvinyl chloride (PVC, or vinyl) was a smart choice for wiring because it possesses excellent fire performance properties.  All organic polymers (whether they are plastics or natural materials like wood, cotton or rubber) are combustible: when sufficient heat is supplied to any organic polymer, it will thermally decompose, and its thermal decomposition products will burn. However, PVC will typically not burn once the source of heat or flame is removed. This results from PVC having 56.8% chlorine in its base polymer weight and it is well known that chlorine is one of the few elements that confers good fire properties to a polymer.  When polymers burn they give off gaseous products, which usually generate flames (most likely with light emission and soot)

Polymer + Heat →  Thermal Decomposition Products

Decomposition Products + Oxygenated Radicals →  Combustion Products + Heat

PVC’s are inherently resistant to ignition, so PVC cable components will limit and slow down the spread of a fire throughout the building and limit the cables to act as a fuse. BUT at the same time the dense black smoke produced by burning PVC materials is very toxic.

1. 1 Kg of burning PVC fills a room of size 500 m3 with smoke
2. 1 Kg of PVC generates 2 litres of HCl acid that corrodes metals and produces toxic fumes

Therefore the demand has been for material to replace PVC at school, colleges, high rise buildings, and commercial complexes etc which do not give off smoke and toxic fumes and do not contain halogens having following characteristics

1. Fire retardant and zero halogen
2. No or Low emission of smoke, toxic fumes and acid gases during combustion
3. Similar mechanical and electrical properties to PVC
4. Acceptable procesability with acceptable cost 

Following is the Trend of Insulating Materials in Building Wires

1. NORMAL PVC
2.  FR PVC (Flame Retardant)
3. FRLS-PVC (Flame Retardant Low Smoke)
4. HR-FR & FRLS PVC (Heat Resistant Flame Retardant Low Smoke)       
5. FR-LF-PVC (Flame Retardant, Lead free Complying with RoHS requirements)
6. FRLS-LF-PVC (Flame Retardant, Low Smoke, Lead Free Complying with RoHS requirements)
7. HR-FRLS-LF PVC(Heat Resistant, Flame retardant,  Low Smoke, Lead free Complying with RoHS requirements)
8.  Thermoplastic HFFR (Halogen Free, Flame Retardant, Low Smoke, Non Toxic Compound)
9.  Crosslinked HFFR ( Crosslinked Halogen Free, Flame Retardant, Low Smoke, NON -Toxic Compound)

1. Experimental details

For Initial compound screening a range of formulation were compounded for five material listed as below

1. PVC (normal PVC)
2. FR-PVC  (Fire Retardant PVC)
3. FRLS-PVC (Fire Retardant Low smoke PVC)
4. Thermoplastic ZHFR (Zero Halogen Flame Retardant)
5. Crosslinked ZHFR.

 The samples produced were used to prepare 1mm extruded tape and for crosslinked ZHFR with varying percentage of catalyst master-batch. These compounded materials were further tested for all physical parameters including, density, standard mechanical properties, % crosslinking etc. Table 1 represents sample exhibiting the balance of physical, electrical and mechanical properties was further studied on final application testing. Table 2 represents cable trial results.  The wire extrusion provides an initial opportunity to regulate the formulation in turn as well its processing behavior during our studies.

1. Results and discussion     

Table 1:- Compound stage results (on 1mm extruder tape)

 

Properties	pvc	FR pvc	FRLS PVC	HFFR	XL-HFFR
Density (g/cc)	1.43	1.45	1.50	1.48	1.51
Physical properties - 1mm extruded Tape
Hot set value @ 200 ⁰C (%)	XX	XX	XX	XX	58
Permanent set @ 200 ⁰C (%)	XX	XX	XX	XX	0
Tensile Strength @ break  (N/mm2)	24.6	23.1	16.9	12.26	12.22
Elongation at break (%)	342	328	316	234	268
Other Properties
Hardness- Shore D	XX	XX	XX	48	47
Hardness- Shore A	90	90	91	XX	XX
Volume Resistivity (Ωcm)	2 X 1014	1 X 1014	7 X 1013	7.5411 X 1014	8.34 X 1014
Fire properties
Smoke density rating, %	75	67	55	3.0	2.9
Limiting Oxygen Index	26.2	30.3	31.5	36	36
Temperature Index (⁰C)	150	265	280	285	300
Thermal stability, Minutes	146	136	133	>180	>180
Halogen acid gas generation (%)	33.7	25.5	17.3	Nil	Nil
Heat ageing (Temperature and Time)	@ 100 ⁰C / 7 days				@ 135 ⁰C / 7 days
% Variation in Tensile Strength	-11	-15	-8	8	12
% Variation in Elongation	-12	-9	-7	-11	-14

  Table 2:- Cable Trial Results

Grade	PVC	FR PVC	FRLS PVC	HFFR	XL-HFFR
Size, Sq. mm	1.5  sq.mm	1.5  sq.mm	1.5  sq.mm	1.5  sq.mm	1.5  sq.mm
Catalyst Master Batch	XX	XX	XX	XX	4 % CTMB-09
Type of Screw (Compression ratio)	PVC (3:1)	PVC (3:1)	PVC (3:1)	ZHFR (1.4 : 1)	ZHFR (1.4 : 1)
Extrusion Type	Pressure	Pressure	Pressure	Semi pressure	Semi pressure
Extruder	90 mm	90 mm	90 mm	90 mm	90 mm
T-1 (oC)	130	130	130	80	80
T-2 (oC)	140	140	140	90	90
T-3 (oC)	150	150	150	135	135
T-4 (oC)	155	155	155	140	145
T-5 (oC)	160	160	160	150	155
Clamp (oC)	165	165	165	165	165
Head (oC)	170	170	170	170	170
Die (oC)	175	175	175	180	180
Surface	Smooth	Smooth	Smooth	Smooth	Smooth
Wire Mesh	80	100	100+40	40	40
Curing temperature, °C	XX	XX	XX	XX	80
Curing time, Hrs.	XX	XX	XX	XX	3 hrs
Thickness of insulation, mm	0.73	0.74	0.74	0.72	0.74
Hot set, %	XX	XX	XX	XX	42
Permanent set, %	XX	XX	XX	XX	5
Tensile strength, N/mm2	18.3	17.5	15.4	11.70	13.5
Elongation, %	240	225	195	180	190
Single flame test Period of burning after removal of flame, sec. Unaffected length, mm	Pass   01 390	Pass   01 385	Pass    02 390	Pass   03 380	Pass    02 390
Volume Resistivity @ 27oC	4.1 x 1013	2.5x 1013	1.6  x 1013	5.7 x 1013	6.6 x 1013
Hot deformation @ 80°C for 4 Hrs. (K=0.6), %	27	28	31	38	HDT @ 100 C, (K=1.0)= 22 %
Heat ageing	@ 100 ⁰C/ 7days			@ 135 ⁰C/ 7days
% Variation in Tensile strength
	-8	-7	-9	18	19
% Variation in Elongation	2	2	-3	-14	-22
Smoke density rating, %	80	70	56	4.2	Cross-linkable
Limiting Oxygen Index	26	30.2	31.1	35	Cross-linkable
Thermal stability, Minutes	135	130	122	>180	> 180
Halogen acid gas generation (%)	33.6	25	17.5	Nil	Nil

 

 

Table 1 represents the comparative properties of PVC, FR PVC, FRLS PVC, HFFR and crosslinked-HFFR (XL-HFFR). These studies were carried out on compounded granules or 1 mm extruded tape or 1mm compressed sheet or 3mm compressed sheet as per the test specimen required on desired temperature profile to obtain smooth surface replicating cable surface.

Density of all compounds were measured and are mentioned in Table 1 are in the range of  1.4- 1.5 g/cc. Physical properties including tensile strength and elongation at break were tested on 1 mm extruded tape. As observed FRLS PVC (nowadays majorly used) have more value for tensile strength and elongation at break than compared to halogen free flame retardant compounds, whereas due to crosslinking behavior the properties are better in  XL- HFFR.  Being thermoset material the crosslinking is measured through hot set value which is < 60 %.

PVC being a rigid material therefore hardness is always measured in Shore A scale, whereas due to high loading of flame retardant fillers the material hardness increases and measured in shore D scale.

XL-HFFR exhibits the higher volume resistivity as compared to the other compounds because during crosslinking the molecular weight increases, its temperature withstanding

properties increases as results it exhibits higher current capacity.

Similarly all five were compared for fire properties. FRLS PVC (the most upgraded form of PVC) also exhibits higher smoke value as observed in Table 1 compared to HFFR compounds. PVC itself extinguishes the fire but shows low limiting oxygen values LOI,  and high halogen acid gas generation compared to HFFR where fire extinguish because of mineral filler mechanism.

The accelerated mode such as heat ageing at 100 ⁰C/7days was performed to understand the long term behavior after cable extrusion. The crosslinked compounds better performance, the accelerated studies heat ageing is carried out at 135 ⁰C/ 7days, thus due to crosslinking its molecular weight increases, temperature withstanding properties also increases.

Table 2 represents the comparative studies were carried out on cable. Compounds were used for cable extrusion keeping desire cable extrusion temperature profile and other parameters constant to understand and compare the physical, electrical and fire properties.  Crosslinked HFFR exhibits the balance of properties compare to the HFFR over FRLS PVC and all. The detail values are mentioned in the Table 2. Thus, the results obtained after cable extrusion are more or less in similar line meeting the requirement of standard.  

Our SPL-ZHFR-3300B is a Zero Halogen, Low Smoke, Flame Retardant, Thermoplastic RoHS compliance polyolefin based Compound for inner sheath/bedding application in various cables.

This compound being versatile in composition can be used for CPR cable constructions for Optical Fiber Cables, Telecommunication cables and control cables.

Cables manufactured with SPL-ZHFR-3300B according to standard technology meet industrial cable specifications as per BS 6724 for bedding materials. This compound consists of special thermoplastic polymers, inorganic filler and other additives. It shows good processing and physical properties.

The Table below shows the properties of this compound and can be used for

Property	Test Method	Unit	Typical Value
Density at 27oC	ASTM D 792	g/cm3	1.48
Melt Index at 21.6 kg & 160oC	ASTM D 1238	g/10min	6
Hardness	ASTM D 2240	Shore D	55
Tensile Strength at break	IEC 60811-1-1	MPa	13
Elongation at break	IEC 60811-1-1	%	180
Limiting Oxygen Index	ASTM D 2863	% O2	33
Temperature Index	ASTM D 2863	o C	280
Smoke Density Rating	ASTM D 2843	%	8
Halogen Acid Gas Generation	IEC 60754-1	%	Nil
Test on Gases Evolved During Combustion	IEC 60754-2
pH		pH	5.5
Conductivity		ms / mm	1.8

 

This compound used for inner sheath/ bedding is placed under the armor and creates a protective layer for the same. They have high loading of flame retardant mineral fillers having superior fire performance. In some cable constructions over the insulation bedding is necessary. For example :- For Insulation crosslinked polyethylene is used then high flame retardant bedding compound is needed as polyethylene is pure polymer and being highly flammable it acts as a deterrent to flame and smoke suppression.