Chain-extending of Hydroxytelechelic Polybutadiene: Synthesis and Characterization

Extension of hydroxytelechelic polybutadiene oligomers ( 3200 g/mol) is performed in mild conditions, in order to avoid backbone modifications, using succinic anhydride or methylenedicyclohexyl diisocyanate. The two routes present significative extension of the initial oligomers. Extension through the anhydride route, in the presence of DCC and DMAP, leads to new hydroxytelechelic oligomers ( 8000 g/mol). Extension through the diisocyanate route, catalyzed by DBTL at 65°C leads to hydroxytelechelic oligomers of higher average molecular weight ( 20000 g/mol). New materials are characterized by FTIR/¹H-NMR and changes in their Tg according to , are discussed. The influence of reaction time on the length of the macromolecular chains is also studied.     

Thermal Degradation of HDPE in a Batch Pressure Reactor: Reaction Time and Mechanical Stirring Effect

The effect of reaction time and mechanical stirring on thermal degradation of high density polyethylene(HDPE) was studied at 350°C under nitrogen atomosphere in a batch pressure reactor. Changes in molecular weight(MW), molecular weight distribution (MWD), and crystalline behaviors of the degraded products were investigated by gel chromatography (GPC) and differential scanning calorimetry (DSC). It was found that MWD curves all shifted toward lower molecular weight with increasing reaction time, with both the extent of the movement and its showing a rapid initial drop and then leveling off. In a short period of reaction time, the MW, MWD and crystalline behaviors of the degraded products were affected notably by the mechanical stirring. The of the degraded products without stirring was lower than that of products with stirring in the same time, which should be related to the large difference of temperature distributions in the reactor. When the reaction time reached 4 h, the of the degraded products had dropped to about 5 × 10³g/mol from about 3 × 10⁵g/mol for the original , and the product did not show the melting and crystallization behaviors of high density polyethylene again.     

POLYPROPYLENE: AN INTRODUCTION

Polypropylene now has a history of nearly 45 years since its discovery and 40 years since its commercialization. It has established itself as one of the most important polymers that has engineering plastic properties at commodity plastics prices. The end of the growth of polypropylene is not in sight.