Ammonium Polyphosphate Intercalated Layered Double Hydroxide and Zinc Borate as Highly Efficient Flame Retardant Nanofillers for Polypropylene.

Yanshan Gao,Qiang Wang,Weiran Lin

doi:10.3390/polym10101114

Abstract

We found in our previous study that layered double hydroxides (LDHs) which undergo aqueous miscible organic solvent treatment (AMOST) can tune the hydrophobicity surface of LDHs to be hydrophobic, and then the solvent mixing method can be used to prepare polymer/LDH nanocomposites. However, flame retardant property is not very high if LDHs are only used. In this present work, ammonium polyphosphate (APP) intercalated LDHs and zinc borate (ZB) was incorporated into a polypropylene (PP) matrix using the solvent mixing method. The structures, morphologies, and performance of the composites were characterized carefully. The peak heat release rate (PHRR) reduction of PP containing 10 and 20 wt % APP-LDH reached 27% and 55%, respectively, which increased up to 63% compared with PP/CO3-LDH. After incorporating 2 wt % ZB in the PP/APP-LDH system, the flame retardant property was further improved. Polypropylene composites with 20 wt % APP-LDH and 2 wt % ZB showed a 58% PHRR reduction. In addition, thermogravimetric analyzer (TGA) results indicated that the addition of APP-LDH and ZB improved the temperature at 50% weight loss (T50%) and the char formation of the materials significantly.

Highlights

Polypropylenes (PPs) are involved in a wide range of applications, such as the automotive, home appliance, and construction industries, etc., due to their ease of processing, excellent mechanical, electrical, chemical resistance, and non-toxicity [1]
Diffraction peak moved to a lower angle (2θ = 9.34◦ ), with an interlayer distance of 0.93 nm, which can be attributed to the intercalation of the relatively larger molecule of ammonium polyphosphate (APP) in the layered double hydroxides (LDHs) interlayers
The PP/APP-LDH and PP/APP-LDH/zinc borate (ZB) nanocomposites were synthesized by solvent mixing method successfully

Summary

Introduction

Polypropylenes (PPs) are involved in a wide range of applications, such as the automotive, home appliance, and construction industries, etc., due to their ease of processing, excellent mechanical, electrical, chemical resistance, and non-toxicity [1]. Most polymer materials, including PPs, are mainly composed of C, H, and O elements, which are easy to burn and generate smoke and toxic, and harmful gases during their combustion, which is a serious threat to both human bodies and the environment. The increased use of these polymer materials has resulted in a growing awareness of flammability problems. LDHs can improve the thermal stability of polymers as well; a small amount of LDHs can increased the thermostability significantly. Similar to general inorganic flame retardants, one of the severe problems of LDHs is that their high loading, generally 40~60 wt % can achieve a good degree of flame retardancy when only LDHs are used [10,11], which usually results in poor mechanical and thermal properties of the materials.

Methods

Results

Discussion

Conclusion