ABSTRACT:In this study, several flame retardants (FRs), containing phosphorus, nitrogen, and silicon, were synthesized. These synthesized FRs were blended with polypropylene (PP) to obtain mixture samples. The flame-retardant properties of these mixture samples were estimated by the limiting oxygen index (LOI) value and thermal stabilities were characterized by thermogravimetric analysis. The LOI values of these samples were improved from 17.0 to 26.0 and the char yield increased from 0 to 27 wt %. A comparison of these samples, with respect to their LOI values and carbon yield, showed that the FRs, which simultaneously contained phosphorus, nitrogen, and silicon elements, can provide materials with the best flame-retardant properties, suggesting that there is a synergistic effect among the three elements on the flame-retardant properties and char yield when they are used in PP.

ABSTRACT:The mechanical properties and morphological structures of blends based on Zn 2ϩ neutralized low degree sulfated ethylene propylene diene monomer rubber (Zn-SEPDM) ionomer and polypropylene (PP) were studied. It was found that Zn 2ϩ neutralized low degree sulfated EPDM ionomer and PP blends, which are new thermoplastic elastomeric materials, have better mechanical properties than those of PP/EPDM blend. Theoretical analysis of tensile data suggests that there is an increase of the extent of interaction between PP and EPDM in the presence of a low degree of Zn 2ϩ , which is also an indicator of better interfacial adhesion between PP and Zn-SEPDM than that between PP and EPDM. SEM results proved that the finer dispersed phase sizes and the shorter interparticle distances are the main reasons for the improved mechanical properties of the PP/EPDM blend.

The flame retardant and mechanical properties of polypropylene (PP), highly filled with aluminum hydroxide (Al(OH)3) and toughened with ethylene propylene diene monomer (EPDM) and zinc neutralized sulfated EPDM ionomer (Zn-S-EPDM), were studied along with their morphology. The PP matrix when highly filled with Al(OH)3 particles can achieve an adequate level of flame retardancy, but there is a decrease in the mechanical properties because of inadequate adhesion between the Al(OH)3 particles and the PP matrix and the strong tendency of the filler to agglomerate. The rubber incorporated in the PP/Al(OH)3 composites has two roles: as compatibilizer and toughening agent. Although ordinary EPDM significantly improves the Izod impact strength of the composites, the tensile properties are much worse because of the weak interfacial adhesion between the modifier and the matrix. Using Zn-S-EPDM instead EPDM, the tensile properties are much improved with only a slight decrease in toughness, because of improvements in the interfacial adhesion between modifier and matrix. SEM micrographs show that the rubber phase is dispersed in the continuous PP matrix and that most Al(OH)3 particles are uniformly distributed in the rubbery phase. Larger, obviously rubbery, domains can be seen in the PP/EPDM/Al(OH)3 ternary composites. Much finer rubbery domains were found in the PP/Zn-S-EPDM/Al(OH)3 composites.

ABSTRACT:The mechanical and electric performances of linear low-density polyethylene (LLDPE) highly loaded with aluminum hydroxide (Al(OH) 3 ) by the grafting of methacrylic acid (MAA) to the LLDPE matrix were studied. The results of Fourier transform infrared spectroscopy showed that the grafting reaction occurred by melt grafting. Mechanical testing of composites of LLDPE highly loaded with Al(OH) 3 showed that the strength and elongation at break were significantly improved after the grafting of MAA to the LLDPE matrix. The results of the electric tests showed similar trends. The results of scanning electron microscopy showed better decentralization of Al(OH) 3 loaded in the LLDPE matrix in the tensile fractured surface and a transition layer between Al(OH) 3 and the LLDPE matrix in the fractured surface after the grafting of MAA to the LLDPE matrix.

Flame retardants containing phosphorus, nitrogen and silicone elements have been synthesized. The thermal stabilities of polypropylene (PP), PSiN and PP/PSiN have been studied by thermogravimetric (TG) analysis in nitrogen, air and oxygen atmospheres. The initial decomposition temperature (IDT), maximum-rate degradation temperature (Tmax), integral procedure decomposition temperature (IPDT) and char yield at 800 °C in various atmospheres have been investigated. Although the IDT of PP was reduced by the introduction of PSiN, the Tmax, IPDT and char yield were all increased. The flame retardancy of PP/PSiN composites were evaluated by measuring their Limiting Oxygen Index (LOI) values. Their thermal stabilities agreed with the results of the flame retardancy tests: the PP/PSiN-A exhibited good flame retardancy with LOI of 26.0 and its char yields at 800 °C were 27 wt.% (in nitrogen), 12 wt.% (air) and 12 wt.% (in oxygen). The activation energies of PP, PSiN and PP/PSiN composites in various atmospheres were calculated using the method of Horowitz-Metzger.