is polypropylene fire resistant

Polypropylene (PP), as one of the five major general plastics, is widely used in various industries. However, the flammable characteristics of PP also limit its application space and hinder the further development of PP materials. Therefore, the flame retardant modification of PP It has always been the focus of people's attention.

Next, let’s take a look at the combustion process and flame retardant mechanism of polymer materials represented by PP, an inventory of flame retardant PP, the application prospects of flame retardant PP in the packaging field, and current problems.

• Combustion process and mechanism of polymer materials

1.Combustion process

Polymer materials refer to polymer compounds containing elements such as carbon, hydrogen, and oxygen in their molecular chains. Most polymers are flammable. The combustion of polymer materials is a combination of a series of physical changes and chemical reactions. Therefore, special phenomena such as melting, softening, and volume changes will appear during the combustion process of polymer materials. The combustion process of polymer materials is shown in Figure 1, which can basically be divided into the following three steps:(1) As the temperature gradually increases, the weaker bonds in the molecular chain will break, and small molecular gases will gradually be produced on the surface of the material. Most of these gases are flammable. These flammable small molecular gases interact with the air. The oxygen in the mixture mixes to form a flammable gas mixture;

(2)As the decomposition reaction proceeds, the combustible concentration of the mixed gas on the surface of the polymer material gradually increases. When the combustible gas concentration of the mixed gas and the external ambient temperature reach the critical conditions required for combustion, a violent explosion will occur. Chemical reaction, the surface of the material is quickly ignited;

(3)The flammable mixed gas burns quickly and releases a large amount of heat. The heat generated will not only spread to the bottom of the material, but also further increase the temperature of the environment around the material, thereby accelerating the decomposition of the material and producing more flammable gases. , ultimately allowing the combustion reaction to continue. Therefore, the combustion of polymer materials can be regarded as a process of gradual promotion and cyclic reaction.

As a hydrocarbon, PP has an oxygen index of only 17.1, is easy to burn, has poor flame retardancy, and generates a large amount of heat when burned. At the same time, dripping can easily cause fires, posing a threat to life and property. In the field of electronics and electrical appliances, the flammable characteristics of PP limit its wider application, so it is necessary to conduct flame-retardant research and development on PP materials.

2.Flame retardant mechanism

Flame retardant mechanisms can be roughly divided into two categories: chain reaction termination mechanism, surface isolation mechanism and interruption of heat exchange mechanism.

(1)Chain reaction termination mechanism When PP burns, it is first decomposed into hydrocarbons, and then further thermally oxidized and cracked into free HO· at high temperature. The chain reaction of HO· is the reason why the combustion can continue, and the termination of the chain reaction is consumption. HO· produced during combustion.

(2)Surface isolation mechanism When PP burns, the flame retardant not only absorbs heat, but also generates solid compounds on the surface of PP. This compound blocks the contact between the matrix and the air, thereby preventing combustion.

(3)Interruption heat exchange mechanism This mechanism means that the flame retardant can absorb a large amount of combustion heat during the combustion process, causing the combustion reaction to lack sufficient heat, and then self-extinguishing occurs, achieving the flame retardant effect.

• Application of flame retardant PP materials in packaging field
  

PP plastic has the characteristics of low density, good transparency, non-toxic and tasteless, easy to process and form, and low price, which make it have great application value in the packaging field. However, PP plastic is flammable and has poor high-temperature resistance and other shortcomings that limit its use in packaging. development of the field. Therefore, in recent years, many scholars have devoted themselves to researching PP packaging materials with high flame retardant properties.

1.Car battery casing

The battery is one of the most important components of new energy vehicles. At the same time, the battery casing, which is responsible for protecting the safety of the battery, is also particularly important. Battery packaging is required to have insulation, impact resistance, anti-corrosion, and good flame retardant properties. Traditional battery packaging is mainly made of metal. materials and sheet molding compound (SMC) materials. However, some of these two materials have complex molding processes and high density, which affects the lightweight of new energy vehicles. Therefore, PP materials with low density and good impact resistance have attracted people's attention. Using PP resin as the matrix, ammonium polyphosphate/triazine compound system as the flame retardant, ethylene-octene copolymer, propylene-based elastomer and EPDM rubber as the toughening agent, it is prepared by melt blending method A PP material with flame retardant properties, used as a battery casing for new energy vehicles. This PP material maintains low density while also having good flame retardant properties and impact strength, good sealing, and strong waterproof performance.

2.Parts packaging

Modify basic magnesium sulfate whiskers (MHSH) and alumina (Al2O3), introduce cross-linking agent KH-550 to their surfaces, then add nitrogen-phosphorus compound flame retardant and PP matrix, and melt and blend The PP/MHSH/Al2O3/N-P composite material was prepared by the method and further processed into a film. Among them, the nitrogen-phosphorus compound flame retardant not only promotes the formation of an expanded carbon layer on the PP matrix at high temperatures, but also reacts with MHSH to form magnesium phosphate with good thermal stability. The presence of magnesium phosphate can enhance the strength of the expanded carbon layer. Strength, it plays a supporting role in the skeleton. The addition of Al2O3 can improve the thermal conductivity of the material, allowing the internal heat of the material to be quickly transferred to the surface to dissipate heat, thereby improving the heat resistance of the material. At the same time, MHSH and Al2O3 are rigid fillers with good mechanical strength and can improve the mechanical properties of the PP/MHSH/Al2O3/N-P composite membrane. Therefore, the PP/MHSH/Al2O3/N-P composite film has both excellent flame retardant properties and high mechanical strength, expanding the scope of application of PP composite materials.

3.Food lunch boxes

Ammonium polyphosphate is used as the gas source and acid source, and the triazine carbon-forming agent is used as the carbon source. Together with the synergist, the IFR is composed, and then it is melted and blended with the clean-processed recycled polypropylene lunch box. The preparation of PP composite materials with high flame retardant properties proves that PP lunch boxes have great potential in recycling.

• Current problems with PP flame retardant

In recent years, more and more people have begun to study flame-retardant PP composite materials. However, the flame-retardant research on PP mainly has the following problems:

(1)The added amount of flame retardant is large and has poor compatibility with the matrix, which causes too much damage to the mechanical properties of the material and affects the use of PP composite materials;

(2)Most of the current flame retardants with high flame retardant efficiency contain halogen, which does not meet the requirements of green environmental protection;

(3)Flame retardants are relatively expensive, which increases the production cost of flame retardant PP materials.

Qingdao primetech Plastic can customize the production of flame retardant PP, flame retardant + filled PP, flame retardant + GF reinforced PP. Currently, more than 150 flame retardant products have been developed and produced, with good mechanical properties and good dimensional stability. In particular, our halogen-free flame retardant PP has a flame retardant grade of up to 1.5mm V0, good precipitation resistance, high glow wire ignition temperature, excellent electrical performance, low toxicity, and meets many environmental standards and regulatory requirements.

Qingdao  primetech  Plastic was established in 2007 and has 16 years of experience in the production of modified plastics, dyeing and color masterbatch. It focuses on one-to-one customized development and mature formulas to ensure that products can accurately match customer requirements. Including PC/ABS alloy, halogen-free flame-retardant engineering plastics, glass fiber reinforced modified materials, antistatic materials, medical grade color masterbatch, PET fiber grade color masterbatch, fully biodegradable plastics, ASA/PE wood-plastic co-extrusion materials, etc. If you have any demand for halogen-free flame retardant PP, please call us for consultation. You can also consult/leave a message online to communicate directly with customer service.