The Effects Of Chemical Structure Of Comb-type Copolymers On The Cold Flowability Of Diesel

A series of MAC copolymers as cold flow improvers were synthesized and the relationship between the molecular structure and their effects on the cold flowability of diesel were also studied in this paper. CFPP test, DSC analysis, optical microscopy and rheological measurement were used to investigate the mechanism of performance of comb-type copolymer in diesel.Comb-type copolymers were synthetized by free radical polymerization method. The chemical structures of comb-type copolymers were characterized by1H NMR and the ratios between polar and nonpolar group were also analyzed. Urea was used to coordinate with diesel to separate the normal alkanes. Besides, average carbon number of0#diesel oil,-10#diesel and Longyu0#diesel was measured by GC-MS. The results indicate that comb-copolymers can improve the flowability of diesel, and their effects on diesel are not always identical. Among copolymers, MAC has the best performance on Longyu diesel. The influences of MAC on CFPP and crystal morphology were studied by CFPP test and polarizing light microscope. It is emphasis on the effects of the lengths of side-chain, the ratios between polar and nonpolar group and the lengths of main-chain on the crystallization of diesel. The results showed that the alkyl chain away from the polar group participate the co-crystallization of diesel. So the actual average carbon number of alkyl chain which participates in the co-crystallization is smaller than the alkyl chain. Therefore, when the length of side-chain of MAC is slightly longer than that of normal alkanes in diesel, the best performance can be obtained. In addition, moderate ratio of polar/nonpolar groups in MACs is benefit for the better adsorption of main chain in molecule on the wax crystal. The polar group in the copolymers can inhibit the growth of wax crystal and help acquiring good flowability of diesel. Moderate length of main chain can improve the solubility and crystallization ability of copolymer, which better makes the crystalline temperature of copolymer and that of the wax crystal match with each other, enhancing the performance of copolymers.Finally, the mechanism of improvement of cold flowability of diesel by MAC copolymers was suggested. It is proved that MAC can improve the cold flow ability of diesel and the structure of MAC is the most important factor. Therefore, research on the chemical structure of comb-type copolymers and the corresponding mechanism has vital research meaning and economic benefits.