A solid-state mechanochemical pulverization process, that is, pan milling, was used to prepare a polypropylene (PP)/carbon nanotube (CNT) composite powder. The composite powder was then melt-mixed with a twin-roll masticator to obtain a PP/CNT composite. The morphology of the PP/CNT powder and the PP/CNT composite was investigated. The crystallization and mechanical properties of the latter were also studied. After 20 milling cycles (ca. 60 min), the average diameter of PP/3 wt % CNT composite powder particles was a few micrometers. The length of the CNTs was reduced from a few micrometers to 0.4 -0.5 m. The CNTs became straighter and more uniform in length. The effects of incorporating the CNTs into PP were as follows: (1) the crystallization rate and temperature of PP increased, (2) a strong b-plane orientation of PP was induced, and (3) the Young's modulus and yield strength of PP increased. Interfacial adhesion between PP and the CNTs was improved by the mechanical action of the solid-state pulverization process used, which favored the dispersion of the CNTs into PP.

Cycloalkyl-modified 8-arylimino-5,6,7-trihydroquinolylnickel pre-catalysts highly polymerize ethylene into branched polyethylene waxes.

No abstract

A series of 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridine derivatives (L1-L3) was synthesized, and reacted with nickel halides to form their corresponding nickel complexes (bromide: Ni1-Ni3; chloride: Ni4-Ni6). All organic compounds and nickel complexes were well characterized. The structure of a representative complex Ni1 was determined by a single crystal X-ray study, revealing a distorted trigonal bipyramidal geometry at the nickel centre. Upon activation with either modified methylaluminoxane (MMAO) or diethylaluminium chloride (Et 2 AlCl), all nickel complexes showed high activities toward ethylene polymerization. The obtained polymers were confirmed to be polyethylene waxes with low molecular weights (in the range of 1.83 to 6.78 kg mol À1 ) and narrow polydispersity (PDI:1.38-1.78); moreover, the obtained polyethylenes were highly branched ones. These polyethylene waxes have potential application as functional adducts of lubricants or pour-point depressants.