Thermal Stability, Combustion Behavior, and Mechanical Property in a Flame-Retardant Polypropylene System

Lili Wang,Milin Zhang,Baibin Zhou

doi:10.3390/app7010055

Lili Wang, Milin Zhang + Show 1 more

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https://doi.org/10.3390/app7010055

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Abstract

In order to comprehensively improve the strength, toughness, flame retardancy, smoke suppression, and thermal stability of polypropylene (PP), layered double hydroxide (LDH) Ni0.2Mg2.8Al–LDH was synthesized by a coprecipitation method coupled with the microwave-hydrothermal treatment. The X-ray diffraction (XRD), morphology, mechanical, thermal, and fire properties for PP composites containing 1 wt %–20 wt % Ni0.2Mg2.8Al–LDH were investigated. The cone calorimeter tests confirm that the peak heat release rate (pk–HRR) of PP–20%LDH was decreased to 500 kW/m2 from the 1057 kW/m2 of PP. The pk–HRR, average mass loss rate (AMLR) and effective heat of combustion (EHC) analysis indicates that the condensed phase fire retardant mechanism of Ni0.2Mg2.8Al–LDH in the composites. The production rate and mean release yield of CO for composites gradually decrease as Ni0.2Mg2.8Al–LDH increases in the PP matrix. Thermal analysis indicates that the decomposition temperature for PP–5%LDH and PP–10%LDH is 34 °C higher than that of the pure PP. The mechanical tests reveal that the tensile strength of PP–1%LDH is 7.9 MPa higher than that of the pure PP. Furthermore, the elongation at break of PP–10%LDH is 361% higher than PP. In this work, the synthetic LDH Ni0.2Mg2.8Al–LDH can be used as a flame retardant, smoke suppressant, thermal stabilizer, reinforcing, and toughening agent of PP products.

Highlights

Polypropylene (PP) is extensively used in many fields, including floor coverings, automobiles, building materials, electronics and electric materials, various home textiles, wall-coverings, and so on [1,2,3,4,5,6]
The Ni0.2 Mg2.8 Al–layered double hydroxide (LDH) exhibit (0 0 3), (0 0 6), (0 1 2), (0 1 5), (0 1 8), (1 1 0), and (1 1 3) characteristic diffraction peaks of the LDH structure, which can be indexed in a hexagonal lattice with an R3m rhombohedral space group symmetry [43,44]
These reflection positions are in good agreement with those of the reported LDHs [43,45]

Summary

Introduction

Polypropylene (PP) is extensively used in many fields, including floor coverings, automobiles, building materials, electronics and electric materials, various home textiles, wall-coverings, and so on [1,2,3,4,5,6]. To reduce flammability and release of CO, the addition of flame retardants is an effective way [13,14,15,16,17]. It is well known, to improve the strength and poor toughness of PP, the reinforcing and toughening agents are necessary additives [18]. The addition of a small amount of flame retardant can increase the flame retardancy, smoke suppression, and thermal stability, and can enhance the mechanical property of PP polymer, which is a desired goal in this work

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Conclusion