No abstract

To examine the effect of aromatic units in a polymer on the crystallization behaviors of waxy gels with a low content of asphaltenes, new comb-type co-polymers of poly(maleic anhydride-co-R-olefin-co-styrene) (MASC) with different ratios of styrene/R-octadecene were designed and synthesized. 1 H nuclear magnetic resonance (NMR) spectra were obtained to characterize the chemical structure of the co-polymers. Solubility and melting point tests were also performed to confirm the as-synthesized MASC co-polymers. The effect of co-polymers on the yield stress of model oils with and without asphaltenes was studied by means of rheology. The morphology of wax crystals was observed by polarizing light microscopy. Upon the addition of MASCs to the model waxy oil, the yield stresses decreased with the increase of aromatic units in MASC chains while increased when 0.1% asphaltenes were added. The morphology of model waxy oil with 0.1% asphaltenes was also changed with the content of aromatic units in MASC. A higher content of aromatic units in MASC and a higher amount of MASC lead to a smaller size of wax crystals.

Poly(styrene-co-maleic anhydride) (SMA) ionomers were synthesized and designed as a new kind of nucleation agent according to the crystallization theory for improving the crystallization of poly(ethylene terephthalate) (PET). The crystallization behavior of PET with the addition of nucleation agents was investigated by differential scanning calorimetry, polarized-light microscope, and X-ray diffraction (XRD). Avrami equation and Hoffman-Lauritzen theory are adopted for analyzing isothermal and nonisothermal crystallization kinetics, respectively. The results show that the addition of 1 wt % SMA ionomers effectively accelerates the crystallization rate and reduces the fold surface free energy of PET at high temperature regions. PLM results also indicated that the crystals impinge on each other, thus decreasing the spherulite size for PET/SMA ionomers samples compared with PET. XRD measurement revealed that the introduction of SMA ionomers does not change the crystal structure but indeed accelerates the crystallinity of PET. The results clearly demonstrate that our synthesized SMA ionomers are an efficient nucleating agent for PET.