Polyolefins Journal
Volume:3 Issue: 1, Winter 2016

High density polyethylene (HDPE) films were produced using cast film extrusion process with different draw ratios, ranging from 16.9 to 148.8. Morphology, crystallinty and orientation state of crystalline and amorphous phases of the cast films were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and polarized Fourier transform infrared spectroscopy (FTIR) analyses, respectively. The anisotropic crystalline structures of row nucleated lamellar morphology were observed for the films produced with high draw ratios. The crystalline phase axes orientation functions were found to be significantly dependent on the applied draw ratios. As expected, annealing increased the crystallinity and melting point temperature (Tm) of the cast films and on the other hand, it also enhanced the crystalline phase orientation. However, the results revealed that annealing also promoted non-twisted lamellar structures, since it increased fc values (c-axis orientation function) and decreased fa values (a axis orientation function) simultaneously. Additionally, it was found that the annealing induced enhancement in c-axis orientation function was more significant for the cast films with lower draw ratios, therefore, it was dependent on the draw ratio.

Due to easy availability of cheaper raw material and increase in new applications, the use of polyolefins in various industries is becoming a major priority. The Middle East region, on account of its vast oil and gas reserves has, in the last decade or so, been developing many new petrochemical complexes with their expansion into colossal polyolefin production capacities. The predictions are that by 2020 the Middle East region will dominate the polyolefin industry as a whole. Furthermore, with proven oil reserves of about 21.7 thousand million tons ( th world ranking) and natural gas of 34.0 trillion cubic meters (1st world ranking), Iran’s petrochemical industry is supported by diverse and abundant feedstock reserves. In line with other polyolefin producers’ developments in the Middle East, Iran's National Petrochemical Company (NPC) has undergone massive structural and technological transformations in the last two decades in order to set up ambitious plans for further capacity increase and native technology developments. This article mainly focuses on Iran today’s position and its future plans in the polyolefins industry.

Ethylene polymerization was carried out using Phillips chromium catalyst based on silica supports such as silica aerogel, SiO2 (Grace 643), and titanium modified SiO2 (G 643), and the results were compared with other catalysts based on SiO2 (Aldrich), SBA-15(Hex), SBA-15(Sp) and MCM-41. A combination of TGA, DSC, XRD, nitrogen adsorption, SEM, ICP, FTIR and other analyses were used to characterize the materials. The results showed that the chromium was successfully introduced into silica supports. Shish-kebab polyethylene was prepared via in situ ethylene polymerization with the Cr/SiO2 (G 643) and Cr/Ti/SiO2 (G 643) catalytic systems. A comparison between different types of catalysts revealed that the polymerization activity of Cr/SiO2 (G 643) was significantly increased to 191 kg PE (g Cr)-1 h-1 due to the higher pore volume and pore diameter of Grace silica compared to the other supports. Also, the polymerization activity of the Cr/SiO2 (G 643) catalyst was significantly improved by Ti modification.

9,10-Dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid disodium salt (DHEAS) was synthesized and used as a nucleating agent for poly(1-butene) (iPB). The isothermal crystallization kinetics of iPB having different nucleating agents were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results showed that the nucleating agents increased the crystallization temperature and the crystallization rate and shortened the crystallization half-time (t1/2). As well, the nucleating agents could be used as heterogeneous nuclei in the iPB matrix and decreased the size of iPB. When the nucleating agent was DHEAS, the crystallization temperature of iPB was up to 93.6°C which was higher than that of other nucleating agents for iPB and pure iPB. The crystallization half-time in the presence of DHEAS was 0.58 min which was less than that of other nucleating agents for iPB and pure iPB. In this case, the spherulitic size of iPB was the smallest and the morphology was changed, which indicated that DHEAS displayed better nucleation effect among the studied nucleating agents.

Mg(OEt)2 with spherical morphology is one of the most important precursors for the preparation of industrial Ziegler-Natta catalysts. In the present article, morphology evolution of Mg(OEt)2 particles is studied in the course of the synthesis. The morphology of Mg(OEt)2 particles is observed throughout the process by SEM. The results show that Mg(OEt)2 particles are formed through i) seed generation on Mg surfaces, ii) seed growth and isolation as independent particles, and iii) further growth and shaping into smoother and more spherical particles. The size of Mg sources greatly affects the rates of these processes to different extents. A larger size of Mg leads to slower seed formation and growth, and detachment of clustered seeds, making the final particles larger and less spherical, respectively. The crystal growth of Mg(OEt)2 is also affected by the size of Mg sources, which in turn differentiates the pore size distribution to affect the catalyst composition and performance.

In this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation process the PP samples were characterized according to their morphological and physical properties and the CO2 generated during the biodegradation in soil was monitored. The CO2 production by the PP films modified with the organic pro-degradant was proportional to the oxidation rate and weight loss of the samples. The reduction in the average viscosimetric molecular weight could be attributed to chain scission due to the weathering conditions to which the samples were exposed (natural ageing followed by biodegradation in soil). Scanning electron microscopy (SEM) of the PP films revealed surface deterioration of the films with the organic pro-degradant after the combined degradation process.