Mechanical properties comparison of different magnesium hydroxide grades in low-smoke halogen-free flame retardant systems

Mechanical properties comparison of different magnesium hydroxide grades in low-smoke halogen-free flame retardant systems

——H5IV and XK-10000SN/99 compare

By:

Ara king and Frank Chen

KMT INDUSTRIAL HK LIMITED 

www.kmtindustrial.com

Abstract :

Formulation was: EVA (7470K) 35%, compatibilizer 5%, antioxidant 0.175%, magnesium hydroxide 60%; Test conditions: 23℃, 40%; and we want to compare two grades XK-10000SN/99 and H5IV mechanical properties, finally the test result shows the tensile strength of XK-10000SN/99 is 16.3Mpa, the elongation at break is 190, the melt index is 0.3, and the oxygen index is 33; the tensile strength of H5IV is 14.8Mpa, The elongation at break is 210, the melt index is 0.52, and the oxygen index is 31.5.

Key words: halogen free flame retardant formula, magnesium hydroxide

1. Materials and Testing

1.1Materials prepare

Ethylene-vinyl acetate copolymer (EVA), grade 7470K, vinyl acetate (vA) content is 26%, from Formosa Plastics Group; Magnesium hydroxide (MH) XK-10000SN/99, particle size of 10000 mesh, from KMT INDUSTRIAL HK LIMITED; Magnesium hydroxide (MH) H5IV, particle size is 10000 mesh, from JM Huber Corporation.

Banbury, Plate Curing Press; Mould; SY-6210-A Electronic Pulling Force Machine; Oxygen Index Meter;

1.2  Preheat the Banbury to 100 °C-120 °C, the mixing time is 30 minutes, the mixing temperature is 200 ± 10 °C

Put the dough into the mould which is preheated well in advance (the thickness of the mould frame is 1 ± 0.1 mm), then use plate Curing Press tabletting (prepress: 10MPA, pressure: 10-15mpa, temperature: 220 °C, preheat for 2 Min) , After tabletting cooled to 40-50 °C  and got the samples.

1.3  Composite Standard Test Strips made from dies, the tensile properties were tested on SY-6210-A electronic tensile machine with a tensile speed of 250 mm/min and sample size of 120 * 10 * 1mm (GB/T 32129-2015 standard for halogen-free flame retardant cable materials for wire and cable).

1.4 Testing of combustion performance (GB/T 2406.2—2009)

2. Results and Discussion

2.1 Two grade magnesium hydroxide powders

Table 1. Fire retardant ingredients used in this study

 XK-10000SN/99H5IV
Test conditions23℃,40%23℃,40%
Particle size (D50)1.5um1.89um
Surface coated or notcoatedcoated

2.2 Test result of tensile strength

Table 2 shows under the formula: EVA (7470K) is 35%, compatibilizer 5%, antioxidant 0.175%, Magnesium hydroxide 60% in the same composition system; The results show that the tensile strength of XK-10000SN/99 is 15.5 MPA, and that of H5IV is 14.8 MPA.

Table 2.

 Formula15
EVA(7470K)35%35%
Compatibilizer5%5%
Antioxidant0.175%0.175%
MDH    XK-10000SN/9960% 
MDH    H5IV 60%
   
Tensile Strength (MPa)16.314.8

2.3Comparison of Elongation at break of two grades in EVA System

According to Table 3, the content of EVA (7470K) was 35%, compatibilizer 5%, antioxidant 0.175% and Magnesium hydroxide 60%; The results show that the elongation at break of XK-10000SN/99 is 190, and that of H5IV is 210. XK-10000SN/99 is a fibre structure with high tensile strength and low elongation at break, which can be improved by surface modification.  H5IV is a hexagonal crystal structure with the advantage of higher elongation at break.

Table 3

 Formula15
EVA(7470K)35%35%
Compatibilizer5%5%
Antioxidant0.175%0.175%
MDH   XK-10000SN/9960% 
MDH   H5IV 60%
   
Elongation at break (%)190210

2.4 Comparison of melting index of two grades in EVA System

According to Table 4, the content of EVA (7470K) was 35%, compatibilizer 5%, antioxidant 0.175% and Magnesium hydroxide 60%

The results show that the melting index of XK-10000SN/99 is 0.3 and that of H5IV is 0.52.

The melting index of XK-10000SN/99 is lower than that of H5IV. that can be improved by selecting the melting index of the substrate.

Table 4

 Formula15
EVA(7470K)35%35%
Compatibilizer5%5%
Antioxidant0.175%0.175%
MDH   XK-10000SN/9960% 
MDH   H5IV 60%
   
MFI(190℃.5KG)0.30.52

2.5 Comparison of Oxygen Index between two grades in EVA System

According to Table 5, the content of EVA (7470K) was 35% , compatibilizer 5% , antioxidant 0.175% and Magnesium hydroxide 60%

The results show that XK-10000SN/99 has a limiting oxygen index of 33, and H5IV has a limiting oxygen index of 31.5.

XK-10000SN/99 has two points higher oxygen index than H5iv and better flame retardancy.

Table 5

 Formula15
EVA(7470K)35%35%
Compatibilizer5%5%
Antioxidant0.175%0.175%
MDH   XK-10000SN/9960% 
MDH   H5IV 60%
   
LOI (100*10*1mm)3331.5

3. Conclusion

 Formula15
EVA(7470K)35%35%
Compatibilizer5%5%
Antioxidant0.175%0.175%
MDH   XK-10000SN/9960% 
MDH   H5IV 60%
   
MFI(190℃.5Kg)0.30.52
Elongation at break (%)190210
Tensile Strength (MPa)16.314.8
Test Conditions23℃,40%23℃,40%
Particle size ( D50/um)1.3-1.61.89
LOI (100*10*1mm)3331.5

According to the above experimental data we can see that:

3.1 under this formulation: H5IV has advantages over XK-10000SN/99:

3.11: High Melt Index

3.12: High Elongation at break

3.2 under this formulation: H5IV compared to XK-10000SN/99 disadvantages:

3.21: Low tensile strength

3.22: Low LOI

Company Profiles…

KMT INDUSTRIAL HK LIMITED, headquartered in Gansu, China, research and manufacturer magnesium hydroxide, natural brucite powder. www.kmtindustrial.com

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