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Q1. Study the effect of hydrogen as a chain transfer agent on the ethylene and propylene polymerization.
Hydrogen is mainly used for the control over molecular weight of all polyolefins prepared with Ti-based Ziegler-
Natta catalysts.
It generally happens that the Ti−C bond in a growing polymer chain undergoes the hydrogenolysis reaction in the presence of molecular hydrogen with the formation of the Ti−H bond and separation of a polymer chain from the active center as per following reaction:
Ti−CH2−CH(CH3)−Polymer + H2 → Ti−H + (CH3)2CH−Polymer
Due to above reaction, it helps to control the molecular weight of polymers. Basically, the amount of hydrogen needed to reduce the molecular weight of polypropylene or ethylene to a commercially useful level is relatively small and the decrease of the molecular weight is correlated with the hydrogen concentration, CH in practical industrial applications. Amount of hydrogen required in less amount to control the molecular weight of polyolefins. Hence, in less amount molecular hydrogen can perform this function.