STUDIES IN ANTIOXIDANTS .4. BRIDGED BIS(THIOSEMICARBAZONE) AS MELT STABILIZER FOR UNSTABILIZED ISOTACTIC POLYPROPYLENE

Polypropylene's high processing temperatures initiate thermal oxidativ e degradation and loss of physical properties. Stabilisation efficienc y of 2,6-di-tert-butyl-4-methyl phenol (BHT) and 4,4'-di-{2-[(3,5-di-t ert-butyl-4-hydroxy phenyl) methylene] hydrazine carbothionmido} biphe nyl ether has been investigated in unstabilised isotactic polypropylen e. Test techniques used to evaluate the stabilisation efficiency are t he melt flow index (MFI), impact strength, heat deflection temperature , tensile strength and modulus and flexural strength and modulus. From the results it was observed that 4,4'-di-{2-[(3,5-di-tert- butyl-4-hy droxy phenyl) methylene] hydrazine carbothionmido} biphenyl ether with 0.05% concentration could stabilise unstabilised isotactic polypropyl ene.