Synthesis And Application Of The Novel DOPO-substitued And Triazinyl Charring Agent In PP

Polypropylene(PP) is one kind of plastics which is widely used in many fields like construction, Automobile, household and military due to overwhelming advantages such as corrosion resistance, non-toxicity, high transparency, easy molding and excellent mechanical property, etc. But its application is limited due to its inflammability, large total heat release, dripping effect and post-combustion phenomenon. Therefore the flame retardant modification to PP is a hot research topic in this filed. Intumescent flame retardant is the most commonly used flame retardant for PP, because it possess high flame retardant efficiency, non-toxicity and no corrosive gases properties.There are three parts in the widely used intumescent flame retardant, including acid source, carbonization agent and blowing agent. Polyalcohol is the commonly used as carbonization agent, which is characterized with larger polarity, bad compatibility, easy to aggregate, bad thermal stability, migration and low flame retardant efficiency, etc. Among those the bad carbon forming ability is the fatal weaknesse. It means we must add more APP to produce enough acidic substance, as to catalyze polyalcohol. However, APP is known as easy to solve in water and aggregate, resulting in the decrease of flame retardant efficiency. What’s more, much more APP brings harmful effects on the mechanical properties.In order to solve the above problems, two kinds of novel DOPO-substitued and triazinyl charring agent were synthesized, using 6H-dibenz(C, E)(1, 2)oxaphosphorin-6-oxide, 4, 4’-diphenylmethane diisocyanate and melamine as raw material. The chemical structures of the charring agents as well as flame retardant and mechanical properties of PP/IFR were tested.The TGA results of the two charring agents showed excellent char-forming ability and the final carbon residues were 36.59 % and 40.58 % respectively. The limiting oxygen index(LOI) and UL-94 vertical burning tests suggested that there was a best ratio between the charring agent and APP to obtain a best flame retardant effect. The best ratio was 2:1 for the two kinds of PP/IFR as tested. And their final carbon residues increased to 21.24 % and 22.98 % respectively with a 30 wt% dosage of IFR. What’s more, the thermostability of PP/IFR systems improved either. Cone calorimeter and scanning electron microscope(SEM) tests results revealed that there exists good synergistic effects between flame retardant groups and APP. This effect greatly decreased HRR and THR of PP/IFR and leaved the biggest residue mass at the end of burning. The final carbon residues were dense, uniform and high strength. It can reduce the heat and air transfer during burning and stop the radicals from exchanging, thus protecting the substrate. The tensile strength and breaking elongation of the PP/IFR were both decreased with the increasing of IFR in some degree, while the impact strength was opposite. SEM tests results explained that the compatibilities between the two IFR systems and the substrate were not so bad as to reduce the tensile strength and breaking elongation a lot. But the impact properties of IFR/PP systems can be improved, because the IFR particles can absorb the impact energy and prevent the crack from spreading.