Enhanced Polypropylene, Flame Retardant And Transparent

Polypropylene (PP) is a rapid development thermoplastic general plastic, and has been found wide applications in electric, automotive, construction industry, agriculture, and so on. However, the weak strength, low temperature brittleness and inflammability limit its further applications. Therefore, how to improve the performance of PP has realistic significance in improving its application value and application range. In this text, the inorganic nano-particle reinforced PP, the non-halogen flame retardance modification of PP and the elastomer toughened transparent PP system were investigated, and the co-incorporation effect of different types of nanofillers in PP matrix, the synergistic effects of halogen-free flame retardant on the flame retardance of PP and the influence of elastomer on the crystallization behavior and transparency of PP were also discussed.(1) Inorganic nano-particles reinforced PPIn this system,50nm CaCO3and20nm SiO2were selected to prepare PP nanocomposites, such as SiO2/PP, CaCO3/PP and SiO2/CaCO3/PP were prepared. The microstructure, crystallization and mechanical properties of those PP nanocomposites were studied by the approaches of rheology, and thermal and mechanical analysis. The co-incorporation effect of nanofillers with different types and sizes in PP matrix was investigated. The results showed that co-incorporation of nano-SiO2and nano-CaCCO3favored the uniform dispersion of nanoparticles in the PP matrix. The co-incorporation of SiO2and CaCO3nanoparticles in PP gave rise to a lower supercooling temperature (ΔT), a shorter crystallization half life (t1/2) and a smaller spherulite size in comparison with those nanocomposites incorporating only one type of CaCO3or SiO2nanoparticles. Because of the uniform dispersion of nanoparticles and superior crystallizability of PP composite with the co-incorporation of nanoparticles, the SiO2/CaCO3/PP nanocomposites have superior flexural strength and impact strength. (2) Non-halogen flame retardance modification of PPSEBS-g-MAH was used as a compatibilizer, and the synergistic effects of zinc oxide (ZnO), nylon6(PA6) and ammonium polyphospha (APP) on the flame retardance of polypropylene were studied. The influence of additives on mechanical properties of PP was also investigated. Flammability testing results indicated that the addition of1%ZnO can improve the flame retardance of APP/PP, while addition of PA6can improve the flame retardance of APP/ZnO/PP significantly. The LOI value of APP/ZnO/PP increases to36.8%by adding10wt%PA6, and further improves to38.9%with SEBS-g-MAH used as compatibilizer. The residual char morphology and composition analysis demonstrated that the residue char layer displayed compact after filling ZnO and exhibited compact structure with layered morphology with the addition of PA6, and the final chemical structure of burning residues doesn’t vary with filler changes. The addition of ZnO, PA6and SEBS-g-MAH can not only improve the flame retardance of APP/PP composite, but also improve the mechanical performance significantly, make up the decrease of mechanical properties with APP additional, which is very important for the extensive application of flame resistant PP.(3) Elastomer toughened transparent PPFirstly, the clarified polypropylene was prepared with the addition of1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) in PP matrix, then poly(styrene-b-ethylene butylene-b-styrene)(SEBS) was used to toughen DMDBS/PP. The influence of SEBS on the crystallization behavior, aggregation structure, mechanical properties, as well as optical performance of DMDBS/PP were investigated. The study results of crystallization behavior revealed that the supercooling temperature (ΔT) of DMDBS/PP did not change significantly while the melting peak shifted to a lower value and became sharper with the addition of SEBS. DMDBS/PP system demonstrates obvious cross-hatched crystal morphology, while SEBS in the SEBS/DMDBS/PP system dispersed uniformly with400-600nm sizes and disrupted the cross-hatched morphology, as revealed by scanning electronic microscope (SEM). Wide-angle X-ray diffraction (WAXD) results indicated that the crystallite size and average interplanar space increased and β-form crystal appeared in DMDBS/PP after blending with SEBS. The transparent composite has superior toughness, stiffness and optical transparency with the co-incorporation of SBES and DMDBS.