Study On The Surface Modification Of Inorganic Particles And Its Effect On The Properties Of Halogen-free Flame Retardant EVA Composites

For high-filled EVA cable materials,the internal particle clusters have a high degree of aggregation,and there are many defects in the organic-inorganic phase interface,resulting in significant loss of mechanical and oil resistance properties of the material.In this paper,functional polysiloxane oligomer?FPSO?,macromolecular grafts with specific structures?EVA-g-MAH?,and isocyanate-terminated polyether polyurethane prepolymers?PUP-PPG?are used.As a surfactant and interface compatibilizer,it is compounded with the EVA matrix and functional filler particles.By controlling the phase interface of the EVA-based cable composite material,a solid improvement of the comprehensive performance of the material is achieved.The main research results are as follows:?1?A kind of functional polysiloxane oligomer?FPSO?was employed as a surfactant to modify the mixture of mix silicon dioxide?Si O₂?,aluminium hydroxide?ATH?and magnesium hydroxide?MH?,and then the modified inorganic compound?MIC?was introduced into the EVA via melt blending,then the EVA cable materials modified with different dosage of FPSO were prepared.The structure and properties of the materials were studied by SEM,DSC,rotational rheometer,electronic universal testing machine,etc.SEM images showed that the presence of FPSO promoted the dispersion and compatibility of MIC in EVA matrix and a compact and stable residual char was formed from the combustion of EVA cable materials.DSC curves showed that the crystallinity of EVA was enhanced since the lower dosages of FPSO was introduced into EVA composites,hence mechanical properties of which was improved.The rheological testing revealed there was an obvious reduction of storage modulus and loss modulus due to the existence of FPSO,as a consequence of the better dispersion of MIC in EVA matrix and the strong interfacial adhesion between MIC and EVA.?2?The EVA-g-MAH,a macromolecular graft with a specific structure,was used as an interface compatibilizer to modify the filler particles and melt blended with the EVA matrix to prepare modified EVA cable materials.The structure and properties of the materials were studied by Soxhlet extractor,SEM,DSC,TGA,DMA,electronic universal testing machine,LOI,etc.The gel content test results revealed that the EVA cable material modified by EVA-g-MAH has a higher content of tightly bound rubber;SEM results showed that the introduction of EVA-g-MAH significantly improves the dispersion of the filler and is conducive to improving Mechanical and oil resistance of materials;DSC and TGA test results indicated that the introduction of EVA-g-MAH has no significant effect on the crystallization and thermal decomposition behavior of highly filled EVA cable materials due to the high similarity between the EVA matrix and the molecular backbone of EVA-g-MAH;the DMA test results showed the strength of the solid network was weakened with the introduction of EVA-g-MAH,and at the same time the interface adhesion of the organic-inorganic phase was increased,hence the storage modulus and loss modulus of the material are reduced.?3?A polyurethane prepolymer?PUP-PPG?was synthesized by molecular structure design,and PUP-PPG was used to modify inorganic particles to construct a micro-nano core-shell structure.High-filled EVA cable materials with different PUP-PPG contents were prepared by melt blending.The structure of PUP-PPG was characterized by FT-IR,and the structure and properties of the materials were studied by Soxhlet extractor,SEM,DSC,TGA,electronic universal testing machine,LOI,etc.FT-IR test results confirmed the correct molecular structure of PUP-PPG;Gel content test results showed that when the content of PUP-PPG was 3wt%,the tight bonding glue content of the cable material was higher;SEM photos of the tensile section revealed that when the content of PUP-PPG reaches 5wt%,the fracture morphology of the sample had good continuity;DSC test results showed that the dispersion of the filler modified by PUP-PPG in the EVA matrix was improved.