Introduction to several commonly used flame retardants for Polypropylene
1. Why does PP need flame retardancy?
About PP
Polypropylene (PP), along with polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS), is recognized as one of the four major general-purpose plastics. With the continuous advancement in polymer modification technologies, PP has demonstrated superior overall performance compared to other general-purpose plastics, leading to its increasingly broad application in various fields such as electronic and electrical devices, automotive components, plastic pipes, films, and nonwoven fabrics.
In the market, PP is commonly categorized into two types: homopolymer polypropylene (HOMO-PP) and copolymer polypropylene (COPO-PP). HOMO-PP features a regular molecular structure, high strength, and appears as transparent or translucent granules. On the other hand, COPO-PP, due to the incorporation of ethylene in its structure, exhibits excellent toughness and is characterized by its milky white granular form.
About the modification of PP
PP can be modified and blended in various ways, including reinforcement, filling, toughening, flame retardancy, conductivity, and coloring. Depending on the specific requirements of the product, one or more of these functionalities can be combined to impart excellent overall performance to PP.
Flame Retardants for PP
The oxygen index of PP, which represents the minimum oxygen concentration required to sustain its combustion under specified conditions, is quite low at only 18. Therefore, flame retardant modification of PP is both a trend and a necessity.
Currently, the flame retardants available for PP on the market include:
1. Brominated Flame Retardants(such as decabromodiphenyl ether, decabromodiphenyl ethane, octabromoether, tetrabromobisphenol A, octabromo-S ether, brominated triazine, hexabromocyclododecane, etc.) — These contain halogens and are not environmentally friendly.
2. Phosphorus-Based Flame Retardants(such as coated red phosphorus, triphenyl phosphate, BDP, RDP, APP, MPP, etc.) and **Nitrogen-Based Flame Retardants (such as MCA, melamine, etc.) — These often struggle to meet stringent flame retardant standards.
3. Inorganic Flame Retardants(such as magnesium hydroxide, aluminum hydroxide, zinc borate, etc.) — These can significantly impact the mechanical properties of the material.
4. Composite NP Intumescent Flame Retardants— These are environmentally friendly, offer high flame retardant efficiency, and provide good cost-effectiveness, meeting UL94 V-0 standards.
While these flame retardants all have some effect on enhancing the flame retardancy of PP, the choice of flame retardant or a combination of flame retardants depends on the comprehensive cost, the specific flame retardant requirements of the PP products, and the inherent limitations of each flame retardant. This tailored approach ensures that different applications can meet the diverse needs of customers.
Flame retardant test methods and standards
Different countries use different flame retardant standards, so there are ISO, GB, ASTM, EN, and AS. Different products have different applications, so there are electrical components, auto parts, pipes, fabrics, films, and foams. Different products have different test standards. The most commonly used test standard is the UL94 vertical burning test method, as shown in the following table:
Grading | V-0 | V-1 | V-2 |
Number of samples | 5 | 5 | 5 |
Ignition times for each sample | 2 | 2 | 2 |
The longest flaming burning time of each sample after each ignition/s | ≦10 | ≦30 | ≦30 |
The longest flameless burning time of a single sample after the second ignition/s | ≦30 | ≦60 | ≦60 |
Total flaming time after 5 samples were ignited 10 times/s | ≦50 | ≦250 | ≦250 |
Whether there is ignition of molten droplets and whether the molten droplets ignite the absorbent cotton | no | no | yes |
Burn to fixture | no | no | no |
Introduction to PP flame retardant from Baozhuan New Materials
Halogen-free intumescent flame retardant BZ-FR1923 (compound flame retardant of piperazine pyrophosphate system)
- General properties
Item | Unit | Index |
Appearance | — | White powder or high concentration masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥18 |
Nitrogen content content of nitrogen | %（ w/w） | ≥19 |
density Density | g/ cm 3 | ≈ 1. 5 |
Average particle size D50 particle size | μm | 5-10 |
Whiteness | % | > 94 |
Thermogravimetric analysis (TGA) | ℃ | 1% TGA ≥250 |
- Key Features:
. Halogen-free intumescent flame retardant (the system does not contain APP) with phosphorus and nitrogen as the main flame retardant elements, mainly plays a flame retardant role by carbon-forming intumescent flame retardant mechanism, and complies with EU RoHS and REACH directives.
. It has high flame retardant efficiency, good thermal stability, no precipitation, low smoke and non-toxicity, good water resistance, and has passed the 70℃ × 168 hours immersion test (UL746C).
. In the black formula system, the flame retardancy is more stable.
- Typical Applications
Used for flame retardant modification of polyolefin plastics such as PP and PE, reaching UL 94 V-0 level.
2.Halogen-free intumescent flame retardant BZ-FR1926 (compound flame retardant of piperazine pyrophosphate system)
- General properties
Item | Unit | Index |
Appearance | — | White powder or high concentration masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥18 |
Nitrogen content content of nitrogen | %（ w/w） | ≥20 |
density Density | g/ cm 3 | ≈ 1. 5 |
Average particle size D50 particle size | μm | 5-10 |
Whiteness | % | > 94 |
Thermogravimetric analysis (TGA) | ℃ | 1% TGA ≥250 |
- Key Features:
. Halogen-free intumescent flame retardant with phosphorus and nitrogen as the main flame retardant elements (the system does not contain APP), mainly carbon-forming intumescent
The flame retardant mechanism plays a flame retardant role and complies with EU RoHS and REACH directives.
. High flame retardant efficiency, good thermal stability, no precipitation, low smoke and non-toxic, good water resistance, passed the 70℃×168h immersion test
(UL746C).
. It is particularly suitable for glass fiber reinforced PP. Adding 20% can reach UL 94 V-0 (0.8mm).
- Typical Applications
Used for flame retardant modification of polyolefin plastics such as PP and PE, reaching UL 94 V-0 level.
3.Halogen-free intumescent flame retardant BZ-FR1923-ZN (compound flame retardant of piperazine pyrophosphate system)
- General properties
Item | Unit | Index |
Appearance | — | White powder or high concentration masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥18 |
Nitrogen content content of nitrogen | %（ w/w） | ≥19 |
density Density | g/ cm 3 | ≈ 1. 5 |
Average particle size D50 particle size | μm | 5-10 |
Whiteness | % | > 94 |
Thermogravimetric analysis (TGA) | ℃ | 1% TGA ≥250 |
- Key Features:
. Halogen-free intumescent flame retardant (the system does not contain APP) with phosphorus and nitrogen as the main flame retardant elements, mainly plays a flame retardant role through the carbon-forming intumescent flame retardant mechanism, and complies with EU RoHS and REACH directives.
. It has high flame retardant efficiency, good thermal stability, no precipitation, light aging resistance , low smoke and non-toxicity, good water resistance, and has passed the 70℃ × 168 hours immersion test (UL746C).
. In the black formula system, the flame retardancy is more stable.
- Typical Applications
Used for flame retardant modification of polyolefin plastics such as PP and PE, reaching UL 94 V-0 level.
4.Halogen-free intumescent flame retardant BZ-FR1926-ZN (compound flame retardant of piperazine pyrophosphate system)
- General properties
Item | Unit | Index |
Appearance | — | White powder or high concentration masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥ 20 |
Nitrogen content content of nitrogen | %（ w/w） | 19 |
density Density | g/ cm 3 | ≈ 1. 5 |
Average particle size D50 particle size | μm | 5-10 |
Whiteness | % | > 94 |
Thermogravimetric analysis (TGA) | ℃ | 1% TGA ≥250 |
- Key Features:
. Halogen-free intumescent flame retardant with phosphorus and nitrogen as the main flame retardant elements (the system does not contain APP), mainly carbon-forming intumescent
The flame retardant mechanism plays a flame retardant role and complies with EU RoHS and REACH directives.
. It has high flame retardant efficiency, good thermal stability, no precipitation, light aging resistance , low smoke and non-toxicity, good water resistance, and passed the 70℃×168h immersion test (UL746C).
- Typical Applications
Used for flame retardant modification of polyolefin plastics such as PP and PE, reaching UL 94 V-0 level.
5.Halogen-free intumescent flame retardant BZ-TC506 (phosphorus-nitrogen intumescent compound flame retardant)
- General properties
Item | Unit | Index |
Appearance | — | White powder or high concentration masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥ 22 |
Nitrogen content content of nitrogen | %（ w/w） | ≥1 8 |
density Density | g/ cm 3 | ≈ 1. 6 |
Average particle size D50 particle size | μm | 4 -10 |
Whiteness | % | > 94 |
Thermogravimetric analysis (TGA) | ℃ | 1% TGA ≥2 3 0 |
- Key Features:
. Halogen-free intumescent flame retardant with phosphorus and nitrogen as main flame retardant elements, mainly plays a flame retardant role by carbon-forming intumescent flame retardant mechanism, and complies with EU RoHS and REACH directives.
. High flame retardant efficiency, good thermal stability, light aging resistance, low smoke and non-toxicity, and good color stability.
. High cost-effectiveness, and can provide product cost reduction solutions.
- Typical Applications
Used for flame retardant modification of polyolefin plastics such as PP and PE, reaching UL 94 V-0 level.
6.Halogen-free intumescent flame retardant BZ-AMH829 (environmentally friendly and efficient flame retardant for PP)
- General properties
Item | Unit | Index |
Appearance | — | White powder or PP carrier masterbatch |
Phosphorus content content of phosphorus | %（ w/w） | ≥ 22 |
Nitrogen content content of nitrogen | %（ w/w） | ≥1 1 |
content of Bromine | %（ w/w） | ≤ 1 2 |
Average particle size D50 particle size | μm | 5 -1 2 |
Whiteness | % | > 96 |
Max Processing Temperature | ℃ | 210 |
- Key Features:
. The flame retardant with phosphorus, nitrogen and bromine as the main flame retardant elements, and its flame retardant modified PP complies with the EU RoHS and REACH directives.
. It has high flame retardant efficiency and can reach UL94 V-2 level by adding 0.8% to homopolymer PP (2% to copolymer PP).
. It has good thermal stability, no precipitation, no water absorption, light aging resistance, low smoke and non-toxicity, does not contain heavy metals, and does not affect the transparency of PP.
- Typical Applications
Used for PP flame retardant modification, reaching UL 94 V-2 level.