Preparation And Properties Of Polypropylene/Polyhedral Oligomeric Silsesquioxane Composites

Polypropylene(PP),as the lightest general-purpose plastics,is often used in the fields of building materials,vehicles,medical equipment and daily necessities,but its ease of burning,aging,poor toughness and low temperature brittleness significantly affect the application of shortcomings to further expand the scope.In order to improve the mechanical properties of PP,such as heat stability,flame retardant and other properties,this paper through domestic and foreign literature research,reviewed the progress of PP modification,and the use of nano-particles polyhedral oligomeric silsesquioxane(POSS)to modify it.The main research content includes the following aspects.1.In this paper,four kinds of POSS with typical representative structure were selected for modification.They were octaPhenyl POSS POSS(B-POSS),octalsobutyl POSS(Oib-POSS),octaVinyl POSS(OV-POSS)and glycidyl POSS(G-POSS).The PP/POSS composites were prepared by melt blending and the thermal and mechanical properties of the composites were tested.The results show that the thermal stability of PP composites containing G-POSS and OV-POSS is better than that of Oib-POSS and B-POSS in the same amount of POSS(2wt%).The results show that G-POSS can increase the elongation of PP,while B-POSS will decrease the elongation of PP.Oib-POSS can improve the strength of PP.The other three kinds of POSS have little effect on PP strength.In this paper,the properties of PP/POSS composites were further studied by using OV-POSS and G-POSS as POSS substrates.2.PP/OV-POSS and PP/DCP/OV-POSS composites were prepared by melt blending,and the thermal properties of the composites were compared.The results show that the thermal stability of PP/OV-POSS composites is better than PP/DCP/OV-POSS composites in air atmosphere.The activation energies of the physical blend composites were further studied from the perspective of thermal decomposition kinetics using Kissinger and Flynn-Wall-Ozawa kinetic models..It was found that OV-POSS could improve the activation energy of PP by thermal decomposition kinetics.3.PP/G-POSS and PP/MAPP/G-POSS composites were prepared by melt blending.The effects of G-POSS and compatibilizer MAPP on the properties of composites were studied.TG test shows that the introduction of G-POSS improves the thermal oxidation stability of PP matrix.When the compatibilizer MAPP is added,G-POSS will synergize with MAPP to further enhance the thermal oxidation stability of the composites.The thermal stability of the composites increased with the increase of the G-POSS content,but when the G-POSS content was 5wt%,the thermal stability of the composites increased with the increase of the thermal oxidation stability of the composites.Oxidation stability will be reduced.Mechanical studies have shown that G-POSS plays an important role in improving PP elongation,reducing PP strength and elastic modulus,especially after adding MAPP.The PP/G-POSS composites with G-POSS content of 5wt%were tested by pyrolysis photoionization time-of-flight mass spectrometry.18 major pyrolysis products were found,including olefins containing monoolefins and diolefins.Some are aromatic hydrocarbons.However,silicon and oxygen are not found in the peaks of pyrolysis products,and these two elements are the main components of G-POSS,because both elements of silicon are generated during the pyrolysis of the composites SiO2 and Si-O-C solid residues,which are not carried by the carrier gas to the ionization chamber.4.PP/IFR/G-POSS flame retardant composite was prepared by using APP and CFA(APP:CFA=3:1)as expansion flame retardant,G-POSS as synergist and MAPP as compatibilizer.The LOI and SEM tests show that the LOI of flame retardant composites increases first and then decreases with the increase of G-POSS content,and reaches the maximum at 2wt%.When a very small amount of crosslinking agent DCP was added to the composites,it was found that the LOI of the composites increased by 2.5 points because DCP could increase the degree of cross-linking between G-POSS and flame retardants and PP substrates.The fuel is more stable at the time of combustion,because it reduces the amount of volatiles and increases the amount of charcoal.