Influence of caged bicyclic phosphate and CaCO3 nanoparticles on char-forming property of PU rigid foams

Char-forming property of PU rigid foams, which can be assessed by char residue (%) when PU is burned at certain temperature, was studied by TG and DTG. The results showed that pure PU rigid foam had low char residue of only 17%, while 33% of char residue was achieved when PU rigid foam was modified by adding 8 wt% of 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2,2,2] octane (PEPA), which is a caged bicyclic phosphate. The experiment results of FTIR and XPS showed that the PEPA modified PU rigid foam could be dehydrogenated and dehydrated at temperature between 380 and 450 °C, resulting in the increase of char residue of PU rigid foam. Further study also revealed that the addition of CaCO₃ nanoparticles could enhance the char stability when the PEPA modified PU rigid foam was being burned. The mechanism was investigated and it was found that the enhanced char stability could be attributed to the limited permeation of oxygen caused by the formation of calcium phosphate and calcium pyrophosphate by the reaction of PEPA and CaCO₃ at high temperature, which were covered on or buried in the char layer.     

Fundamental results on the reaction–diffusion equations associated with a PEPA model

This paper presents an extension of the fluid approximation of a PEPA model by augmenting with diffusion to take spatial information into account, which is described by a reaction–diffusion system with homogeneous Neumann boundary conditions. The existence and uniqueness of the solution are given, positivity and boundedness of the solution to the system are also established. Moreover, sufficient conditions for the convergence are discussed under different cases. Our results show that the action rates determine the behavior of positive solutions. Numerical simulations are presented to illustrate the analytical results.     

MnO_2对PP/MPP/PEPA膨胀阻燃体系的协同作用研究

以MnO2为阻燃协效剂,采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的无卤阻燃PP.研究了MnO2用量对PP阻燃性能和协同作用的影响.结果表明:添加少量的MnO2即可显著提高PP的阻燃性能;当MPP/PEPA/MnO2添加量分别为12%、8%和2%时,阻燃PP的氧指数高达32.TGA、FTIR分析和体式显微镜和SEM观测结果表明:添加MnO2可以催化MPP/PEPA间的酯化反应,促进体系成炭,形成更致密的炭层,从而提高材料的阻燃性能.