Effect of Polyolefin Elastomers’ Characteristics and Natural Magnesium Hydroxide Content on the Properties of Halogen-Free Flame-Retardant Polyolefin Composites

Michela Meucci,Camillo Cardelli,Andrea Pucci,Sara Haveriku,Marco Badalassi,Giacomo Ruggeri

doi:10.3390/micro2010011

Michela Meucci, Camillo Cardelli + Show 4 more

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https://doi.org/10.3390/micro2010011

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Abstract

This study examines the preparation of several composites that are based on natural magnesium hydroxide (n-MDH) and various poly(ethylene-co-octene) polyolefin elastomers (POEs). Design of experiment (DoE) principles have been applied in order to optimize the mechanical, rheological, and flame-retardant properties of the final composites. DoE allows one to evaluate the influence of each variable on an experiment’s final properties. By increasing the density and crystallinity of the POE, a higher elastic modulus was obtained, which resulted in greater tensile strength and lower elongation at break. Improved flame retardant properties (as measured by the limiting oxygen index (LOI) and vertical burning tests) were obtained by increasing the amount of filler within the composite up to 65% and using a polymer with high crystallinity. More specifically, the best balance between mechanical, rheological, and flame retardant properties was provided by DoE using 63.75% n-MDH filler. The agreement between the predicted performance and the final properties of the composites has enabled the innovative use of DoE to provide reliable predictions about the final mechanical and flame retardant properties of the compounds that are used for low voltage electrical cable applications.

Highlights

In recent years, the use of halogen-free flame retardant (HFFR) compounds has attracted significant and increasing interest since they do not produce heavy smokes during combustion, reducing their toxicity and corrosion issues
The design of experiment method that was adopted here has been exploited in order to study the effects of the different molecular properties (MFI and density) of polymers and the effects of different amounts of filler on polyolefin elastomers (POEs) composites
A wide variety of parameters were studied for the design of experiment, such as the tensile strength, elongation at break, and Young’s modulus for measuring the mechanical properties and the limiting oxygen index and vertical burning tests for measuring the fire properties

Summary

Introduction

The use of halogen-free flame retardant (HFFR) compounds has attracted significant and increasing interest since they do not produce heavy smokes during combustion, reducing their toxicity and corrosion issues. HFFR polymer compounds are mainly based on ethylene-vinyl acetate (EVA) copolymers [1]. Ethylene-octene or ethylene-butene copolymers, which are produced by metallocene catalysis, named ULDPE or more generally POE [2]. Both of these polymeric families are highly flexible, having low crystallinity, a melting point between 60 ◦ C and 100 ◦ C, and a broad array of molecular weights [3]. POEs are used in various industries, such as transport, building, textiles, electronics, and wires and cables [4].

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