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

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.

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

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

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

3. Conclusion

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