J.M. Lopez Cuesta

Flame retardant and mechanical properties of a copolymer PP/PE containing brominated compounds/antimony trioxide blends and magnesium hydroxide or talc

The incorporation of two brominated compounds/antimony trioxide blends into a PP–PE copolymer were studied. Both brominated trimethylphenyl indane (FR 1808) and poly(pentabromobenzyl acrylate) (FR 1025) confer good flame retardancy at 40% loading. A comparison was made with the incorporation of magnesium hydroxide at higher loadings (up to 64%) in the same copolymer. The mineral filler improves both fire resistance and stiffness of the copolymer, nevertheless the high loading causes a dramatic decrease in impact resistance. Moreover, the necessary surface treatment of the filler significantly lowers the maximal tensile strength. In order to maximize both fire resistance and mechanical properties, we combined each brominated flame-retardant system (20% in weight) with magnesium hydroxide or talc (20% in weight). Talc is used as reference. These composites show interesting fire-retardant properties in comparison with the copolymers containing only 40% of the brominated flame-retardant systems. In addition, the mechanical properties are on the whole improved.

Incorporation of a grafted brominated monomer in glass fiber reinforced polypropylene to improve the fire resistance

Glass fiber reinforced polypropylene composites have been flame retarded using a brominated acrylate as both monomer (PBB-MA) and polymer (PBB-PA), associated with Sb2O3 (Sb/Br) and Mg(OH)2. We have shown that the brominated monomer can react either by grafting onto the polymer matrix or onto the glass fibers or by polymerizing around the Sb2O3 particles. We have highlighted that the efficiency of this FR system is connected to its high bromine content and to its reactivity with polypropylene. We have observed that grafting of brominated monomer onto glass fibers does not strongly modify the fire properties of the composites. We have demonstrated that the action of PBB-MA/Sb2O3 can be improved in reinforced PP by combination with Mg(OH)2, which delays ignition. Improvement of the fire properties of the composites has been achieved to the detriment of mechanical properties which are strongly affected by the presence of the brominated polyacrylate.

Study of the degradation of fire-retarded PP/PE copolymers using DTA/TGA coupled with FTIR

Abstract A PP/PE copolymer was successively flame retarded using Mg(OH) 2 , then using brominated trimethylphenyl indane associated with Sb 2 O 3 (Br/Sb), and finally using blends of equal weights of this last combination with Mg(OH) 2 or talc-containing non-hydrated fillers. Decompositions of pure and additive-containing copolymer were studied by DTA/TGA coupled with FTIR. A good correlation exists between the maxima of Gram–Schmidt curves and the derivatives of TGA curves. The coupling of techniques shows that the incorporation of the Br/Sb flame retardant limits strong exothermic phenomena due to sample ignition. In the case of Mg(OH) 2 associated with Br/Sb, the decomposition of the hydrated mineral occurs at a lower temperature than the reaction between brominated trimethylphenyl indane and Sb 2 O 3 . This delays the action of Br/Sb flame retardant towards higher temperatures, improving the thermal stability of the polymer. A good agreement is also found between DTA/TGA-FTIR conclusions and fire resistance tests carried out on standardized samples. When magnesium hydroxide is replaced by the fillers, the interest in using a pure talc, which appeared in fire resistance tests, is not strongly confirmed by DTA/TGA-FTIR. This discrepancy may be ascribed to the reduced influence of mass diffusion phenomena due to the small weight of the sample used in thermal analysis experiments.

Incorporation of natural flame retardant fillers in an ethylene-propylene copolymer, in combination with a halogen-antimony system

Abstract The aim of our research is to optimize the flame retardant and mechanical properties of an ethylene-propylene copolymer filled by various natural fillers. These fillers act by releasing water, producing an endothermic effect. They also mechanically reinforce the copolymer. Nevertheless, the filler loadings required to meet flame resistance requirements (French standard M.3) lead to low values of impact resistance, limiting the range of applications. Consequently, we decided to combine a mineral filler able to release water with an inhibitory blend made up of a brominated compound and antimony trioxide. All the results presented hereafter concern an industrial mineral containing mainly calcium borate, whose commercial name is ‘Portabor’. It was used alone in the copolymer at first, and then in combination with antimony trioxide and decabromodiphenyl oxide. Thermal analysis revealed the individual features of each component and its reactivity. The mixture proved to have good complementary mechanical and flame retardant properties.

Talcs and brominated trimethylphenyl indane/Sb2O3 blend in a PP-PE copolymer

Several fillers containing various percentages of talc were incorporated at 40% loading, and at 20% in combination with 20% of a brominated flame retardant system in a PP-PE copolymer. Fire resistance and mechanical properties were studied. Ignition time at dripping test, UL 94 behaviour, and tensile yield stress are improved by the use of fillers with high percentages in talc, low median diameter and high lamellarity index. These correlations are interpreted by the crystallisation ability of talc which creates a strong filler-polymer adhesion. The melting of this crystalline phase around the filler is expected to protect the filled material when a heat source is applied. Mixed compositions with micronic and quite pure talc exhibit V0 class at the UL 94 test and interesting tensile and flexural mechanical properties.

Distribution of a brominated acrylate flame retardant in polypropylene

Abstract Thermal polymerization of pentabromobenzylacrylate (PBBMA) in a polypropylene (PP) composite that contains glass fibers and magnesium hydroxide has been studied using scanning and transmission electron microscopy techniques coupled with energy-dispersive spectrometry. The addition of PBBMA imparts flame retardant (FR) properties to the PP composite but also affects adversely its mechanical properties. It is of practical importance to determine the spatial distribution and the extent of polymerization of the FR in the PP composite in order to understand better its role in the system. The methods presented here allow the distinction between the monomeric and polymeric forms of the FR and to determine their spatial distributions. PP itself shows poor adhesion to the glass fibers, which may be improved by the addition of the reactive PBBMA. The latter is polymerized during reactive extrusion through an antimony-catalyzed reaction. Antioxidant hinders self-thermal polymerization but the presence of antimony overcomes this interference. PP shows good adhesion to sized Mg(OH) 2 as expected from a properly surface-treated filler.

Dynamic rheological studies and applicability of time–temperature superposition principle for PA12/SEBS-g-MA blends

The viscoelastic behaviour of PA12/SEBS-g-MA blends was studied. Time sweep, amplitude sweep, and frequency sweep tests were analysed by the use of parallel-plate rheometer. Time sweep test shows time-independent viscoelastic behaviour of the polymer and blends during the entire duration of test. The critical shear strain was higher for PA12 as compared to that of SEBS-g-MA and the blends in amplitude sweep test. However, the plateau modulus was higher for SEBS-g-MA as compared to PA12. The complex viscosity, dynamic storage, and loss moduli of PA12 increased with the addition of SEBS-g-MA as a consequence of phase interaction between them. The influence of phase morphology of blend composition on their rheological properties was also examined. The blend showed a transformation from liquid-like to solid-like behaviour. The decrease in viscosity for PA12 and blends was observed with increasing temperature. The van Gurp plots was successfully used to validate time–temperature superposition principle (TTS) for PA12, SEBS-g-MA and blend compositions. PA12 holds TTS with a horizontal shift factor that fits Arrhenius equation. Whereas TTS fails for SEBS-g-MA and the blends studied because of different temperature-sensitive response and microstructural changes of melt during shear application.

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

AbstractThe present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.