Exploring The Outstanding Performance And Environmental Advantages of Halogen-Free Flame-Retardant PPO

Exploring The Outstanding Performance And Environmental Advantages of Halogen-Free Flame-Retardant PPO

Polyphenylene ether (PPO) is a highly polymeric material known for its difficult flammability, easy char formation, high mechanical strength, excellent heat resistance, and chemical corrosion resistance, with an oxygen index of 29%. In recent years, with the increasing demand for environmental protection, the demand for halogen-free flame-retardant products has also spurred the widespread application of PPO in the field of halogen-free flame retardancy. By modifying PPO, a high level of flame retardancy can be achieved, and since the flame retardant does not contain halogens, it is gradually being valued for replacing traditional halogen-containing flame retardant products, such as in the field of wire and cable.

Incorporating PPO into TPE wire and cable materials, PPO is highly compatible with polystyrene (PS), allowing for blending in any proportion with minimal impact on mechanical properties. Its char-forming characteristic plays a flame-retardant role during combustion. When PPO decomposes upon heating, it forms char that covers the surface of the blended material, acting as a barrier to oxygen and thus preventing the spread of flames. Due to PPO's high molecular weight, good thermal stability, good compatibility with the polymer matrix, and low tendency to migrate or leach out from the polymer matrix, it holds promising prospects for application.

Polyphenylene ether (PPO) is known for its high melt viscosity, and it can be blended with polystyrene (PS) in any proportion, thus improving the flame retardancy of composite materials when PPO is added. Currently, in TPE wire and cable materials, halogen-free flame retardants containing phosphorus are widely used. The phosphorus in the flame retardant promotes the char formation of PPO, creating a dense char layer that isolates heat and oxygen, thereby preventing the spread of flames. Additionally, this also limits the volatilization of short chains and monomers produced by the thermal decomposition of PS, significantly reducing the release of smoke. Therefore, the flame retardant and PPO can produce a synergistic effect.

Researchers have introduced halogen-free flame retardant MRP (microencapsulated red phosphorus) and char-forming polymer PPO into HIPS resin matrix to study their synergistic flame-retardant effects on HIPS in detail. They analyzed the flame-retardant mechanism and obtained a composite system with the least amount of flame retardant and the best comprehensive flame-retardant performance.

Figure 1 illustrates the variation curve of the oxygen index for MRP-PPO/HIPS composite materials when the total mass fraction of MRP and PPO is fixed at 30%. It can be observed that when the total amount of flame retardant is the same, the relative proportions of MRP and PPO have a significant impact on the oxygen index of the composite material. As the amount of MRP increases, the oxygen index of the composite material first increases, reaches a peak, and then gradually decreases. The oxygen index of the composite materials obtained by using MRP and PPO in combination is higher than that obtained by using either alone. In this experiment, when MRP or PPO was added individually to the HIPS matrix, the resulting composite materials had oxygen indices of 22.4% and 19.4%, respectively. When the mass ratio of MRP-PPO/HIPS was 10:20:70, the oxygen index of the composite material reached its maximum value of 23.9%. It is evident that MRP and PPO do indeed have a certain synergistic flame-retardant effect on HIPS, with the optimal amount of MRP being around 10%; an excessive amount can actually reduce the flame-retardant performance of the composite material.

Figure 2 presents digital photographs of the horizontal and vertical burn residues of several different materials. The results of the horizontal and vertical burning performance experiments indicate that the appropriate combination of MRP and PPO has a very significant synergistic flame-retardant effect on HIPS, capable of producing composite materials with excellent flame-retardant properties, which is consistent with the experimental results of the oxygen index.

From the above research, it is evident that the synergistic effect of PPO with flame retardants can significantly enhance the flame-retardant performance of polymers, which is of great significance in the high-temperature flame retardancy of TPE wire and cable materials.

PPO's Characteristics

In fact, PPO is not only resistant to high temperatures and flame retardancy, but it also possesses many other properties. The performance of PPO determines its wide range of application fields and usage, such as:

1. PPO has a low density, high heat deflection temperature, good dimensional stability, and is easy to process, making it suitable for manufacturing casings, chassis, and precision parts for office equipment, household appliances, and computers.

2. The dielectric constant and tangent of dielectric loss angle of PPO are the lowest among the five major general-purpose engineering plastics, meaning it has the best insulating properties and is not affected by temperature or frequency. It is suitable for the electronics and electrical industry, particularly for making electrical insulating components under humid and loaded conditions, such as IC trays, coil cores, tube seats, control shafts, transformer shielding sleeves, relay boxes, and insulating pillars.

3. PPO has good resistance to water and hot water, making it suitable for manufacturing water meters, water pumps, water valves, and impellers. Bobbins used in textile factories need to withstand steaming, and those made from PPO significantly extend their service life.

4. Due to the development of the electronics and telecommunications industries, mobile phones, portable computers, high-performance cameras, and camcorders all require lithium-ion batteries, thus the market for lithium-ion batteries has great development prospects. The packaging materials and grid materials for organic electrolytes in lithium-ion batteries used to be made of Acrylonitrile-Butadiene-Styrene copolymer (ABS) or Polycarbonate (PC). Recently, foreign countries have developed PPO materials for battery use, which perform better than ABS and PC.

5. PPO has a wide range of applications in the automotive industry, such as dashboards and bumpers. Alloys of PPO with polyamide (PA), especially those with high impact resistance, are used in the development of exterior components and are growing rapidly.

6. In the chemical industry, modified polyphenylene ether can be used to manufacture corrosion-resistant equipment. It is particularly resistant to hydrolysis and also resistant to acids, alkalis, and does not dissolve in aromatic and chlorinated hydrocarbons.

7. It is used in medical devices, where it can replace stainless steel and other metals in hot water storage tanks and exhaust fan mixer valves, such as surgical instruments, tableware, and equipment that requires repeated sterilization by steaming.

In conclusion, Yinsu Flame Retardant Company has specially developed a red phosphorus flame retardant, when combined with PPO for HIPS, also achieves highly effective halogen-free flame-retardant properties. This red phosphorus flame retardant, known as FRP-950 series, is a red phosphorus mother granule flame retardant made from microencapsulated red phosphorus as the main ingredient. It is provided in a dust-free granular form, overcoming the hazards associated with red phosphorus powder, making storage, transportation, and use safer . The use of this flame retardant in conjunction with PPO for HIPS not only enhances the flame retardancy of the composite materials but also aligns with the growing demand for environmentally friendly and halogen-free solutions in the plastics industry.