Effect of molecular weight on flammability and melt dripping behaviour of intumescent based flame retardant polypropylene

• Main Author: Ng, Wei Kang
• Other Authors: Aravind Dasari
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science::Chemistry::Organic chemistry
• Online Access: https://hdl.handle.net/10356/157212
• Institution: Nanyang Technological University

This report evaluates the flammability and melt dripping behaviour of different melt flow index (MFI) of polypropylene (PP) containing nitrogen-based intumescent flame-retardant (IFR) additives. Fire retardant (FR) additive loading was set at 20.5% to determine the possibility of a low loaded PP polymer. Additives tested are Melamine Pyrophosphate (MPP), Piperazine Pyrophosphate (PAPP) and Zinc Borate (ZB) It was found that regardless of MFI or ratio of additives loaded, UL94 performance for 20.5% loaded samples have only managed to achieve a V-2 or NR rating. Char formation of samples tested were insufficient in fully protecting samples and resulted in flame drips or the samples burning to completion. As samples only achieved V-2 or NR ratings, their extinguish times will be used to compare their flammability performance. Thermogravimetric analysis (TGA) reveals that a 3:2 or higher ratio of PAPP:MPP results in greater char residue which is shown to improve flammability performance. A higher MFI for FR loaded samples have also been shown to improve flammability performance as they remove the ignited portions through flame drips quicker, thereby preventing the rest of the sample from combusting. The conclusion drawn is that at such a low FR loading of 20.5%, there is little potential for a good FR product using current additives. The main issues to tackle would be the flame drips as well as the poor intumescent char formation as a result of said low FR loading.