Green Highly Clay-Filled Polyethylene Composites as Coating Materials for Cable Industry-A New Application Route of Non-Organophilised Natural Montmorillonites in Polymeric Materials.

Stanisław Wysocki,Sandra Paszkiewicz,Krzysztof Kowalczyk,Elżbieta Piesowicz,Paweł Figiel

doi:10.3390/polym12061399

Stanisław Wysocki, Sandra Paszkiewicz + Show 3 more

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https://doi.org/10.3390/polym12061399

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Abstract

In order to develop flame retardant and relatively green cable coating materials, polyethylene (PE) was melt blended with 5, 7.5, or 10 wt. % of a natural calcium montmorillonite (C–Ca) pre-dispersed in EBA (ethylene-butyl acrylate copolymer), EVA (ethylene-vinyl acetate copolymer), or mEVA (EVA modified with maleic anhydride). For comparison, an organophilised montmorillonite (CW9) was tested. The main study of composites containing EBA/C–Ca, EVA/C–Ca, and mEVA/CW9 pre-dispersions revealed that both clays were not fully exfoliated in the matrix, however, C–Ca (7.5 wt. %) markedly increased limited oxygen index (LOI) from 18% O2 (PE) up to 22.0% O2. An insignificantly higher LOI value (22.2% O2) was noted for a sample with 10 wt. % of CW9. The fillers did not affect hardness, but spectacularly increased Young’s modulus of the compression-moulded samples (tensile strength and elongation at break values were reduced). Thermal features of the matrix were not unpredictably changed by the clays. Generally, all the tests revealed that PE filled with the chemically untreated natural C–Ca reached similar or better mechanical and thermal features than materials containing the ammonium salt-modified montmorillonite.

Highlights

Modern polymeric materials for cable sheaths should exhibit low flammability and smoke production as well as no emission of toxic gases during their combustion [1,2]
It shows that platelets of the organophilised montmorillonite (CW9) were more effectively dispersed in the PE matrix contained the ethylene-vinyl acetate copolymer (EVA) copolymer enriched with maleic anhydride
The enthalpy values decrease with increasing content of the pre-dispersions and they were mostly reduced for the samples with EVA/C–Ca

Summary

Introduction

Modern polymeric materials for cable sheaths should exhibit low flammability and smoke production as well as no emission of toxic gases during their combustion [1,2]. One of the most commonly used thermoplastics in the cable industry is polyethylene (PE) due to its relatively high electrical resistivity, easy processing, and lack of halogen elements, it is a highly flammable material and must be flame retarded. An application of organophilised montmorillonites (OMMTs)—as flame retardants for various polymeric materials—has attracted great interest of industrial. Montmorillonites (MMTs) are members of the smectite clay group and exhibit a 2:1 type platelet structure. The preparation of valuable OMMTs-based PE nanocomposites is difficult due to the extraordinary low polarity of the matrix (polar groups usually facilitate dissipation of the individual OMMT platelets in polymers [13,14,15]). Due to the limited solubility of polyolefines in the commonly used solvents, OMMT dissipation in the polymers is usually realised via melt compounding methods. Correlation between OMMTs and fire resistance of LDPE was studied, for example, by Zhang and Wilkie [16]

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