Magnesium Hydroxide in Low-Smoke Flame Retardants

Table of Contents

1. Introduction

2. Materials and Testing Methods

1. 2.1 Materials Preparation

2. 2.2 Testing Conditions and Equipment

3. 2.3 Sample Preparation Process

4. 2.4 Mechanical Properties Testing Method

3. Test Results and Discussion

1. 3.1 Comparison of Two Magnesium Hydroxide Powders

2. 3.2 Tensile Strength Test Results

3. 3.3 Comparison of Elongation at Break

4. 3.4 Comparison of Melt Flow Index

5. 3.5 Comparison of Oxygen Index

4. Conclusion

1. 4.1 Advantages of H5IV

2. 4.2 Advantages of XK-10000SN/99

5. Practical Applications and Outlook

6. Frequently Asked Questions

1. Introduction

As environmental regulations and safety standards continue to tighten, the demand for halogen-free flame-retardant materials has surged in various industries. Magnesium hydroxide (MH) has gained significant popularity as a halogen-free flame retardant due to its excellent fire-resistant properties and environmentally friendly characteristics. This study aims to compare the mechanical properties of two magnesium hydroxide grades, XK-10000SN/99 and H5IV, when combined with an EVA (ethylene-vinyl acetate) matrix, to evaluate their potential applications in flame-retardant cable materials.

The results of this study will provide valuable insights into the strengths and weaknesses of these materials, allowing industries to select the most suitable magnesium hydroxide grade for their specific needs. This article will provide a detailed overview of the experimental methods, results, and a discussion of the properties that contribute to their performance in flame-retardant applications.

2. Materials and Testing Methods

2.1 Materials Preparation

The materials used in this study include Ethylene-Vinyl Acetate copolymer (EVA) grade 7470K, which has a vinyl acetate content of 26%, supplied by Formosa Plastics Group. Two magnesium hydroxide (MH) powders were used for comparison: XK-10000SN/99 and H5IV, both with a particle size of 10,000 mesh. XK-10000SN/99 was supplied by KMT Industry, while H5IV was sourced from JM Huber Corporation. In addition to these key ingredients, the formulation also includes a compatibilizer at 5% and an antioxidant at 0.175%.

2.2 Testing Conditions and Equipment

All tests were conducted under standard conditions of 23°C and 40% relative humidity. The testing equipment included a Banbury mixer for compounding, a plate curing press for molding, a SY-6210-A electronic tensile tester for mechanical property testing, and an oxygen index meter for measuring flame-retardant properties.

2.3 Sample Preparation Process

The sample preparation began by preheating the Banbury mixer to 100°C-120°C. The mixing time was set at 30 minutes, with the temperature controlled at 200 ± 10°C. After mixing, the dough was placed into preheated molds with a thickness of 1 ± 0.1 mm. The molding process involved prepressing the material at 10 MPa, followed by a pressure of 10-15 MPa at 220°C for 2 minutes to ensure proper tabletting. The samples were then allowed to cool to 40-50°C before being removed for testing.

2.4 Mechanical Properties Testing Method

The mechanical properties of the samples, including tensile strength and elongation at break, were tested according to the GB/T 32129-2015 standard for halogen-free flame-retardant materials used in cables. The samples were cut into standard strips measuring 120 × 10 × 1 mm and tested on the SY-6210-A electronic tensile tester at a speed of 250 mm/min.

3. Test Results and Discussion

3.1 Comparison of Two Magnesium Hydroxide Powders

The two magnesium hydroxide powders tested in this study were XK-10000SN/99 and H5IV. Both powders have a particle size of approximately 10,000 mesh, but the D50 particle size of XK-10000SN/99 was slightly smaller at 1.5 μm, compared to H5IV at 1.89 μm. Both materials were coated, which aids in improving their dispersibility and interaction with the EVA matrix.

3.2 Tensile Strength Test Results

Under the formulation of 35% EVA (7470K), 5% compatibilizer, 0.175% antioxidant, and 60% magnesium hydroxide, the tensile strength of XK-10000SN/99 was found to be 16.3 MPa, whereas H5IV exhibited a tensile strength of 14.8 MPa. This indicates that XK-10000SN/99 offers higher mechanical strength, making it more suitable for applications where tensile strength is critical.

3.3 Comparison of Elongation at Break

The elongation at break of the two materials differed slightly. XK-10000SN/99 exhibited an elongation at break of 190%, while H5IV had a higher elongation at break of 210%. This suggests that H5IV has better flexibility, making it a more suitable choice for applications requiring higher elongation and better flexibility.

3.4 Comparison of Melt Flow Index

The melt flow index (MFI) of XK-10000SN/99 was 0.3, while H5IV exhibited a higher MFI of 0.52. A lower MFI is often desirable in industrial applications as it indicates better stability and a higher resistance to flow under heat, making XK-10000SN/99 more suitable for applications requiring a material with controlled viscosity.

3.5 Comparison of Oxygen Index

The oxygen index is a critical factor for evaluating the flame-retardant properties of materials. The results show that XK-10000SN/99 had a limiting oxygen index (LOI) of 33, while H5IV had a LOI of 31.5. A higher oxygen index indicates better flame resistance, making XK-10000SN/99 a more effective flame-retardant material.

4. Conclusion

Based on the experimental data, we can draw the following conclusions:

4.1 Advantages of H5IV

· Higher melt flow index, which may be beneficial for processing in certain applications.

· Better elongation at break, providing increased flexibility.

4.2 Advantages of XK-10000SN/99

· Higher tensile strength, offering superior mechanical performance.

· Higher limiting oxygen index (LOI), indicating better flame retardancy.

Both magnesium hydroxide grades have unique properties, and

their suitability depends on the specific requirements of the application. XK-10000SN/99 is more suitable for applications requiring higher flame resistance and tensile strength, while H5IV is ideal for applications where flexibility and processability are critical.

5. Practical Applications and Outlook

The results from this study highlight the potential for both XK-10000SN/99 and H5IV to be used in a variety of industrial applications, particularly in the production of flame-retardant cables and other plastic-based materials. Further research into optimizing the formulations and improving the processing techniques could lead to even better performance, ensuring that these materials meet the growing demands for environmentally friendly and high-performance products.

6. Frequently Asked Questions

Q1: How do the two types of magnesium hydroxide compare in flame retardancy?
A1: XK-10000SN/99 has a higher oxygen index, making it a more effective flame retardant compared to H5IV.

Q2: Which material is better for applications requiring flexibility?
A2: H5IV has a higher elongation at break, making it more flexible compared to XK-10000SN/99.