TY - THES

T1 - Investigations on the flame retardant and crosslinking properties of polypropylene compounds grafted with nitrogen and phosphorus containing monomers

AU - Spörk, Martin

N1 - embargoed until null

PY - 2015

Y1 - 2015

N2 - In the present work, the formation mechanisms and resulting properties of non- halogenated flame-retarded polypropylene (PP) were investigated. Monomers containing vinyl and phosphorus or nitrogen groups were grafted onto PP, and crosslinking of PP was attempted by means of three different mechanisms, in order to improve both the burning and the dripping properties. In the first part of the work, the monomers vinylphosphonic acid (VPA), 1-vinylimidazole (VIM), diethyl vinylphosphonate (DEVP) and 4- (diphenylphosphino)styrene (DPPS) were polymerised using various initiators (2,2′- azobis(2-methylpropionamidine)dihydrochloride (AIBA), 2,2′-azobis(2-methylpropionitrile) (AIBN) and dicumylperoxide), and studied in terms of reactivity. In the second part, the products showing the highest degree of polymerisation as determined by 1H-, 13C-, and 31P-NMR spectroscopy, i.e. VPA and VIM, were subsequently mixed with PP in the melt state, as well as with various initiators, industrial flame retardants and silanes. The burning and dripping properties of the compounds were investigated by fire tests, and classified according to a detailed scheme proposed in the present work. Oscillatory rheometry tests were used to characterise the materials’ crosslinking behaviour. High amounts of VPA (3 wt.-% of PP or more) in combination with PP, 3-(trimethoxysilyl)propyl methacrylate and dicumylperoxide were found to yield the most promising results. The application of smaller amounts of VPA did not result in immediate crosslinking. However, after annealing the compounds at room temperature for 24 hours, crosslinking could be observed. All successfully crosslinked compounds were found to behave as good anti- dripping agents. Differential scanning calorimetry experiments revealed the presence of a second crystal modification within the crosslinkable PP compounds, the β-modification, which can enhance the mechanical properties of the material. Thermogravimetric analysis showed that the selection of the flame retardant or crosslinking additive does not impact the optimum processing temperature of the PP compounds.

AB - In the present work, the formation mechanisms and resulting properties of non- halogenated flame-retarded polypropylene (PP) were investigated. Monomers containing vinyl and phosphorus or nitrogen groups were grafted onto PP, and crosslinking of PP was attempted by means of three different mechanisms, in order to improve both the burning and the dripping properties. In the first part of the work, the monomers vinylphosphonic acid (VPA), 1-vinylimidazole (VIM), diethyl vinylphosphonate (DEVP) and 4- (diphenylphosphino)styrene (DPPS) were polymerised using various initiators (2,2′- azobis(2-methylpropionamidine)dihydrochloride (AIBA), 2,2′-azobis(2-methylpropionitrile) (AIBN) and dicumylperoxide), and studied in terms of reactivity. In the second part, the products showing the highest degree of polymerisation as determined by 1H-, 13C-, and 31P-NMR spectroscopy, i.e. VPA and VIM, were subsequently mixed with PP in the melt state, as well as with various initiators, industrial flame retardants and silanes. The burning and dripping properties of the compounds were investigated by fire tests, and classified according to a detailed scheme proposed in the present work. Oscillatory rheometry tests were used to characterise the materials’ crosslinking behaviour. High amounts of VPA (3 wt.-% of PP or more) in combination with PP, 3-(trimethoxysilyl)propyl methacrylate and dicumylperoxide were found to yield the most promising results. The application of smaller amounts of VPA did not result in immediate crosslinking. However, after annealing the compounds at room temperature for 24 hours, crosslinking could be observed. All successfully crosslinked compounds were found to behave as good anti- dripping agents. Differential scanning calorimetry experiments revealed the presence of a second crystal modification within the crosslinkable PP compounds, the β-modification, which can enhance the mechanical properties of the material. Thermogravimetric analysis showed that the selection of the flame retardant or crosslinking additive does not impact the optimum processing temperature of the PP compounds.

KW - Polypropylene (PP)

KW - gepfropftes Polypropylene

KW - Flammschutz

KW - halogenfrei

KW - Vernetzung

KW - Silan

KW - Vinylphosphorsäure

KW - 1-Vinylimidazol

KW - polypropylene (PP)

KW - grafted polypropylene

KW - flame retardance

KW - halogen-free

KW - crosslinking

KW - silane

KW - vinylphosphonic acid

KW - 1-vinylimidazole

M3 - Master's Thesis

ER -