Original Article:
Synergistic barrier effect of aluminum phosphate on flame retardant polypropylene based on ammonium polyphosphate/dipentaerythritol system
Zhaolu Qin, et al.
Materials & Design, 2019, 181: 107913.
10.1016/j.matdes.2019.107913
Aluminum phosphate is a common inorganic phosphate with the molecular formula AlPO4. Aluminum phosphate is widely used in the fields of building materials, fireproof coatings and refractories because of its excellent high temperature resistance. In addition, aluminum phosphate can be used as a binder and matrix in ceramics and may also be a promising alternative material for oxidation resistance. In this work, the authors explored the synergistic barrier effect of aluminum phosphate on the char formation of flame-retardant polypropylene (FR-PP) in ammonium polyphosphate (APP)/dipentaerythritol (DPER) system.
The synergistic barrier mechanism of aluminum phosphate on FR-PP composites is shown in the figure, and aluminum phosphate plays an important role in the following aspects:
1. APP first degrades with the loss of water and ammonia to generate polyphosphoric acid.
2. Polyphosphoric acid is then cross-linked with DPER to produce expanded carbon. During this process, the decomposition speed of some APPs has been delayed.
3. At the same time, aluminum metaphosphate is formed by the crystalline transformation of aluminum phosphate. Because the melting point of aluminum phosphate is as high as 1500°C, which is much higher than the ignition temperature of the material, aluminum metaphosphate exists in the form of solid powder when it burns. Due to the thermal oxidation of the sample surface, the content of aluminum metaphosphate gradually increased.
4. In addition, high surface tension and air bubble effect may also cause aluminum metaphosphate to migrate to the sample surface. The surface of the residue is blocked by aluminum metaphosphate.
In conclusion, crystalline aluminum metaphosphate improves the compactness and uniformity of carbon residue. Therefore, the insulation effect of carbon residue is increased, and the transfer of oxygen, combustible gas and heat during combustion is prevented.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM7784307 | Aluminum phosphate |  |
7784-30-7 | Price |
| ACM56574686 | Aluminum phosphate |  |
56574-68-6 | Price |
| ACM98499640 | Aluminum phosphate |  |
98499-64-0 | Price |
