Polypropylene flake graphite thermal conductive composite

In recent years, the use of flake graphite modified polypropylene to prepare low-cost and high thermal conductivity composites has attracted more and more attention. polypropylene has low price, corrosion resistance, excellent mechanical properties, and good processability; flake graphite has a wide range of sources and high thermal conductivity, but the compatibility between flake graphite and polypropylene is poor and it is difficult to mix evenly.

In order to solve the above problems, Wang Zhengzheng of Hebei University of science and technology improved the compatibility between flake graphite and polypropylene by adding coupling agent, improved the dispersion of flake graphite in polypropylene by using the sheer force of an open mill, and studied the effects of coupling agent variety and dosage, flake graphite content and particle size on the thermal conductivity and mechanical properties of composites, polypropylene/flake graphite thermal conductive composites with high thermal conductivity and good mechanical properties were prepared. The materials have broad apolypropylenelication prospects in heat exchange equipment in the fields of the chemical industry, architecture, electronics, seawater desalination, and so on.

1. Effect of coupling agent on properties of polypropylene/ flake graphite Composites

Comparative experiments were carried out without adding and using silane coupling agents KH – 550, KH – 560, and KH – 570. After KH-550 treatment, the tensile strength, tensile elastic modulus, flexural strength, and flexural elastic modulus of the composites reached the highest 34.4 ＾ MPa, 8.02 ＾ GPA, 51.5 ＾ MPa and 9.10 ＾ GPA respectively, which was better than the mechanical properties of the composites treated with the other two coupling agents and untreated flake graphite.

2. Effect of the amount of coupling agent on the properties of polypropylene/ flake graphite composite

Add 50% with a particle size of 17 μ M flake graphite, changing the content of KH – 550 in flake graphite to prepare thermal conductive composites. Five groups of experimental data show that the tensile strength of the composites increases first and then decreases. When the content of KH – 550 is 1%, the tensile strength, tensile modulus, and flexural modulus increase significantly.

3. Effect of flake graphite particle size on properties of polypropylene/flake graphite Composites

Under the condition that the fixed flake graphite content is 50% and the dosage of KH – 550 is 1%, the particle sizes are 17, 27, 37, 74148 respectively μ M flake graphite to prepare composites.

The thermal conductivity of the composites increases with the increase of flake graphite particle size. flake graphite particle size is 17 μ The thermal conductivity of m composite is 1.76w / (m · K), while the particle size of flake graphite is 148 μ The thermal conductivity of m composite is 2.68 w / (m · K), which is 52.3% higher than the former.

With the increase of flake graphite particle size, the tensile strength and flexural strength of the composites are gradually decreasing. When the particle size of flake graphite is 17 μ M, the tensile strength, tensile elastic modulus, flexural strength, and flexural elastic modulus of the composites are 34.4 ＾ MPa, 8.02 ＾ GPA, 51.5 ＾ MPa and 9.10 ＾ GPA respectively.

4. Effect of flake graphite content on properties of polypropylene/flake graphite Composites

The particle size of fixed flake graphite is 17 μ m. The amount of KH – 550 is 1% of the graphite content. Composites with different flake graphite content are prepared. The test results of thermal conductivity and mechanical properties are as follows:

With the increase of flake graphite content, the thermal conductivity of the composites increases, the tensile strength, and flexural strength first decrease and then increase, and reach the lowest at 20% flake graphite content; The tensile elastic modulus and flexural elastic modulus increase with the increase of flake graphite content, and the fracture tensile strain and fracture bending strain decrease accordingly.

Conclusion

Use particle size 17 μ When adding 70% flake graphite and KH – 550 is 1% of flake graphite content, the thermal conductivity of polypropylene/flake graphite thermal conductive composite prepared by mixer and molding is 4.16w / (m · K), tensile strength is 36.1 MPa, the tensile elastic modulus is 10.7 GPA, flexural strength is 59.0 MPa and flexural elastic modulus is 13.72 GPA.