Flammability and Thermal Kinetic Analysis of UiO-66-Based PMMA Polymer Composites.

Ruiqing Shen,Rong Ma,Elizabeth Joseph,Yufeng Quan,Qingsheng Wang,Hong-Cai Zhou,Tian-Hao Yan

doi:10.3390/polym13234113

Abstract

Metal–organic frameworks (MOFs) are emerging as novel flame retardants for polymers, which, typically, can improve their thermal stability and flame retardancy. However, there is a lack of specific studies on the thermal decomposition kinetics of MOF-based polymer composites, although it is known that they are important for the modeling of flaming ignition, burning, and flame spread over them. The thermal decomposition mechanisms of poly (methyl methacrylate) (PMMA) have been well investigated, which makes PMMA an ideal polymer to evaluate how fillers affect its decomposition process and kinetics. Thus, in this study, UiO-66, a common type of MOF, was embedded into PMMA to form a composite. Based on the results from the microscale combustion calorimeter, the values of the apparent activation energy of PMMA/UiO-66 composites were calculated and compared against those of neat PMMA. Furthermore, under cone calorimeter tests, UiO-66, at only 1.5 wt%, can reduce the maximum burning intensity and average mass loss rate of PMMA by 14.3% and 12.4%, respectively. By combining UiO-66 and SiO2 to form a composite, it can contribute to forming a more compact protective layer, which shows a synergistic effect on reducing the maximum burning intensity and average mass loss rate of PMMA by 22.0% and 14.7%, respectively.

Highlights

UiO-66 and its composite with SiO2 were synthesized and well characterized first. They were added into PMMA to form polymer composites via in situ polymerization
SiO2 @UiO-66 show flame-retardant effects on PMMA, which is even better than nanosilica, a well-accepted, environmentally friendly flame-retardant filler for PMMA
Based on the analysis of combustion gas emission and heat of combustion, the dominant flame-retardant mechanism of UiO-66 and SiO2 @UiO-66 for PMMA is related to physical actions in the condensed phase

Summary

Introduction

Metal–organic frameworks (MOFs), known as porous coordination polymers (PCPs), have emerged as a promising class of crystalline porous materials with unique properties [1] They are essentially formed by connecting metal ions with polytopic organic linkers together through coordination bonds. Due to their exceptionally high specific surface area, tunable pore size distribution, and rich surface chemistry, MOFs have received significant interest in the areas of gas storage, gas/vapor separation, catalysis, luminescence, and drug delivery [2]. Most recently, they have received much attention as a novel type of filler into polymers to form composites. These polymer composites show promising flame retardancy and thermal stability [3,4,5]

Methods

Results

Conclusion