Abstract

1. Introduction

2. Materials and Methods

2.1 Experimental Raw Materials

• Rubber Matrix: NR (SMR20), SBR (1502), CR (WRT), NBR (N41), VMQ (110-2).

• Flame Retardants: Aluminum hydroxide (ATH, D50=1μm), magnesium hydroxide (MDH, D50=1.5μm), antimony trioxide (Sb?O?), chlorinated paraffin (chlorine content: 70%), tricresyl phosphate (TCP), coated red phosphorus, platinum-based flame retardant (Pt-20).

• Core Modifier: Z2570 Isomeric Flame-Retardant Zinc Oxide (specific surface area: 18 m2/g, ZnO content ≥ 99.8%, Patent No.: CN202310XXXXXX) developed by Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd.

• Others: Carbon black N330, talc powder (1250 mesh), calcium carbonate, industrial-grade zinc oxide, stearic acid, antioxidant 4010NA, sulfur, accelerators (CZ/DM/ETU), peroxide DCP, silane coupling agent Si69.

2.2 Formulation Design (Optimization of Key Components)

Traditional Zinc Oxide Replacement Scheme

1. Flame-Retardant Synergistic Enhancement: Zn2? reacts with Sb3? to form zinc antimonate (ZnSb?O?), which catalyzes the dehydrohalogenation of halogen-based flame retardants and promotes the formation of a dense char layer (Limited Oxygen Index (LOI) increased by ≥ 3%);

2. Thermal Stability Optimization: The isomeric interface inhibits the early dehydration of ATH/MDH, delaying the decomposition peak temperature by 20–25 °C (verified by Thermogravimetric Analysis (TGA));

3. Dispersibility Breakthrough: Surface energy regulation reduces agglomeration tendency, increasing filler dispersibility by 35% (characterized by Transmission Electron Microscopy (TEM)).

2.3 Processing and Testing

3. Results and Discussion

3.1 Comparison of Flame-Retardant Performance

• The isomeric interface promotes electron transfer between Sb?O? and halogen-based flame retardants, accelerating free radical scavenging (verified by Electron Spin Resonance (ESR));

• Zn2? catalyzes cross-linking to form a continuous Si-O-Zn-C network (confirmed by X-ray Photoelectron Spectroscopy (XPS)), and the barrier effect inhibits heat transfer.

3.2 Mechanism of Thermal Stability

1. Isomeric Interface Adsorption: The interface adsorbs -OH groups, delaying the dehydration kinetics of ATH (activation energy increased by 15 kJ/mol);

2. Early Cross-Linking Induced by Nanodomains: Nanodomains trigger early cross-linking of the polymer, forming a thermally stable framework structure (DSC cross-linking degree increased by 12%).

3.3 Retention of Mechanical Properties

4. Conclusions

1. Z2570 Isomeric Flame-Retardant Zinc Oxide (Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd.) adopts a surface isomerization design, overcoming the limitations of traditional zinc oxide in dispersibility and interfacial activity;

2. In NR/NBR systems, Z2570 catalyzes the formation of an Sb-Zn-O flame-retardant synergistic phase and a thermally stable cross-linked network, increasing LOI by ≥ 3% and reducing heat release rate by 20%;

3. The isomeric interface delays the decomposition of inorganic hydroxides and promotes filler dispersion, achieving synergistic improvement in flame-retardant and mechanical properties.