Polymerization Mechanism of α-Linear Olefin

The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of α-linear olefin in TiCl3/AlEt2Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetry restrictions for reactants, products, the possible transition states, and intermediates was calculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as flloes： （i） Coordination compounds were formed on the optimum configuration of TiCl3/AlEt2Cl.（ii） The transition states were formed. The energy di？erence between transition states and the coordination compounds was 40.687 kJ/mol. （iii） Double bond opened and Ti-C（4） bond fractured, and the polymerization was completed. The calculation results also showed that the chain growth mechanism did not essentially change with the increase of carbon atom number of α-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the α-linear olefin, it can be seen that the α-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.

近期国内塑料市场行情

一、PE市场 目前国内PE市场,各主要品种价格继续反弹,但反弹的空间有限。由于进口货到货量较前阶段略有减少,大庆、吉化等企业也进入检修期,市场供应量略有减少,贸易商借机炒作,使PE市场本不应在需求相对淡季的月份出现反弹。

One-step synthesis of hydrophobic magnesium hydroxide nanoparticles and their application in flame-retardant polypropylene composites

Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties(e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index(LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.

Bubble Formation in Non-Newtonian Fluids Using Laser Image Measurement System

A self-developed laser image measurement system was established to study the behavior of bubble for- mation at a single orifice in non-Newtonian polyacrylamide(PAAm)solutions.Images of bubbles were captured by a CCD camera and volumes of bubbles were digitally analyzed online.The effects of rheological property of PAAm solution,orifice,reservoir,and gas flowrate on bubble formation were studied experimentally.It is found that the volume of bubble increases with the concentration of PAAm solution,the diameter of the orifice,and the gas flowrate,respectively,whereas little effect of reservoir is observed in experiments.

Development of Palm Oil Based Bio-product Industrial Wax and Its Application Performance Study

Machining is a mechanical process where excess material from a work is removed to produce a product. At the moment different ferrous, non-ferrous materials and industrial blue wax have been used for prototype models. However such materials is very expensive. Hence an attempt is made to substitute these materials by the palm oil based bio-wax produced in Malaysia. In this research, the authors will analyze and investigate whether there is a possibility to use the palm oil based bio-wax material to substitute with the petroleum based industrial-wax. Experimental analyses are carried out to investigate the capability and the strength of the palm oil based bio-wax material. The matrix blends were prepared of fatty acids from oleo-chemicals, palm oil wax, natural ash fibre and low linear density polyethylene （LLDPE） by stirring and melt-mixing. Sample b!ends are machined with lathe machining process. The sample blends showed there was no built edge formation and good smooth surface production.

UV-Polarizing Linear Polyyne Molecules Aligned in PVA

Electronic absorption bands of conjugated linear carbon chain molecules, namely polyynes H(C≡C)nH (n=5-7), are exploited to devise light-polarizing films applicable to the UV. Laser ablated polyynes are separated in size and dispersed in a film of polyvinyl alcohol (PVA), which is stretched to align the trapped linear polyyne molecules inside. As a nature of the structural anisotropy, transition dipole of the UV absorption for polyyne molecules is in parallel with the molecular axis and the absorption occurs only for the electromagnetic wave having the amplitude of its electric vector along the molecular axis. Aligned and fixed orientationally in the solid PVA film, polyyne molecules act as selective absorbers of one of the polarization components of incident light at particular wavelength. Using a light source of linearly polarized UV light, whose direction of polarization is rotatable, angular dependence of the absorption intensity is investigated for the stretched PVA film containing aligned polyyne molecules and analyzed in terms of an order parameter in the theory of linear dichroism.

Flame retardancy effect of surface-modified metal hydroxides on linear low density polyethylene

Metal hydroxides （MAH） consisting of magnesium hydroxide and aluminum hydroxide with a mass ratio of 1：2 were surface-modified by y-diethoxyphosphorous ester propyldiethoxymethylsilane, boric acid and diphenylsilanediol in xylene under dibutyl tin dilaurate catalyst at 140 ℃. Phosphorus, silicon and boron elements covalently bonded to metal hydroxide particles were detected by X-ray photoelectron spectroscopy. The degradation behavior of the surface-modified MAH was characterized by thermogravimetric analysis. The results show that linear low density polyethylene （LLDPE） composite, filled with 50% （mass fraction） of MAH modified by 5.0% （mass fraction） of modifiers, passes the V-0 rating of UL-94 test and shows the limited oxygen index of 34%, and its heat release rate and average effective heat combustion in a cone calorimeter measurement decrease obviously; The mechanical properties of MAH can be improved by surface-modification. The uniform dispersion of particles and strong interfacial bonding between particles and matrix are obtained.

Linear extrapolation for prediction of tensile creep compliance of polyvinyl chloride

The universal creep equation is successful in relating the creep （ε） to the aging time （t） , coefficient of retardation time （β） , and intrinsic time （ to ）. This relation was used to treat the creep experimental data for polyvinyl chloride （ PVC ） specimens at a given stress and different aging times. The βgs found by the “polynomial fitting” method in this work instead of the “middle - point” method reported in the literature. The unified master line was constructed with the treated data and curves according to the universal equation. The master line can be used to predict the long- term creed behavior and lifetime by extrapolating.

Microbial Aspects in Comparing Modified Atmosphere Packaging and Vacuum Packaging on Shelf Life of Fresh Bull Meat

The importance of meat preservation and various reports on different types of packaging, and to compare the effects of modified atmosphere packaging （MAP） and vacuum packaging （VP） on shelf life of flesh bull meat, and microbiological tests on meat together with some chemical and sensory tests was on tight observation. It was an experimental study, 96 samples were randomly packaged in two groups of MAP and VP equally. The package consists of five layers which are Polyvinylidin Chloride （PVDC）, Ethyl Vinyl Alcohol （EVOH）, Poly Ethylene （PE）, Linear Low Density Poly Ethylene （LLDPE）, and poly Amid （PA）, respectively. MAP meat with 700 mL of CO2 per kg of meat. The packaging were made in at-ameh-pars factory and transported in chilled condition to a well prepared refrigerator in National Research Institute of Food Science （NRIFS） of Shahidbeheshti University of Medical Sciences. These samples tested weekly, since first day after packaging, and week 2, 3, 4, 5, 6, 7, and 8. Microbial tests include Total Microbial, Coliform, Lactic Acid Bacteria, Pseudomonas Counts, and Clostridium. Chemical and sensory tests also carried out. Total volatile bases （TVN）, TBA, and pH as chemical analyses and color, odor, and weep as sensory analyses are also added. Results revealed that total microbial count was in standard range within the 6 weeks for VP, and 5 weeks for MAP technique. Other microbial factors including coliforms, lactic acid bacteria are less and somehow in chemical and sensory tests emphasized the microbial figures. recommended for meat packaging. similar pattern to total count, and no clostridia were found. By the way, The results showed that according to our existing facilities, VP is

Non-Linear Analysis of Energy Absorption Systems under Impact Loads through FEM

This paper presents a non-linear simulation of the impact on a structure with different energy absorption systems using finite element models. Literature review on bistable structure, aluminum foam and expandable polystyrene is presented and taken as basis to propose energy absorption systems. Using a base structure, these systems are implemented by means of finite element modeling. A comparison of the damage caused to the structure in case of impact without implementing energy absorption system, and implementing energy absorption systems based on bistable structures, polystyrene foam and aluminum foam are shown here in. The results demonstrate the advantages of using energy absorption systems on structures under impact loads.

Highly linear polyethylenes using the2-(1-(2,4-dibenzhydrylnaphthylimino)ethyl)-6-(1-(arylimino)ethyl)-pyridylcobalt chlorides: synthesis, characterization and ethylene polymerization

The series of 2-（1-（2,4-dibenzhydrylnaphthylimino）ethyl）-6-（1-（arylimino）ethyl）pyridine derivatives and their cobalt chlorides （Col-Co5） were synthesized and fully characterized. The representative complexes Co2 and Co3 were confirmed by single crystal X-ray diffraction analyses, indicating pseudo-square-pyramidal geometry around the cobalt centre. All cobalt complexes, activated with either methylaluminoxane （MAO） or modified methylaluminoxane （MMAO）, exhibited high activities towards ethylene polymerization, and produced polyethylenes with high molecular weight and highly linear feature as well as unimodal distribution.

Different influences of nucleating agents on crystallization behavior of polyethylene and polypropylene

The crystallization behavior of polyethylene (PE) and polypropylene (PP), including the neat ones and the ones nucleated with the same nucleating agent (NA), was studied by DSC. It was found that the nucleating agent decelerated the PE nonisothermal crystallization process. NA did enhance the nucleating rates for both PE and PP, but the linear growth rate dominated the volumetric growth rate for PE, and the volumetric growth rate dominated the overall crystallization rate. That is why PE nucleated with NA had a slower overall crystallization rate than the neat one.

Measurement of the anisotropy factor with azimuthal light backscattering

The potential capability of low coherence backscattering(LBS) is explored to determine the anisotropy factor based on azimuthal light backscattering map. The scattering intensity signal measured at azimuthal angle φ=0° is extracted for analysis. By performing nonlinear regression fitting on the experimental signal to the Henyey-Greenstein phase function, the anisotropy factor is determined. The experiments with tissue phantom consisting of the aqueous suspension of polystyrene microspheres are carried out. The results show that the measured anisotropy factor is well described by Mie theory.