JournalTOCs

Polyolefins Journal
Number of Followers: 0

This is an Open Access Journal

Open Access journal
ISSN (Print) 2322-2212 - ISSN (Online) 2345-6868
Published by Iran Polymer and Petrochemical Institute

[2 journals]

Analyzing the mechanical behavior of iPP/iPP-g-MA/EPDM blends after
substituting a high molecular weight amorphous poly(1-hexene) for EPDM in
them.
- Abstract: Varying amounts of a high molecular weight poly(1-hexene) (PH, Mv=1.7×10^6 Da) are substituted for EPDM in an iPP/iPP-g-MA/EPDM blend (weight ratio: 76:4:20) and mechanical properties as well as phase morphology of the blends are studied and compared. The results show that upon substituting the entire EPDM by PH, tensile strength at break increases from 18.7 to 21.1 MPa, elongation at break increases from 15.5% to 370.8%, and impact strength increases from 6.4 to 50.1 kJ.m-2. Dynamic mechanical thermal analysis (DMTA) of the blends proves immiscibility in them and SEM analysis corroborates these findings by showing droplet-matrix morphologies. Studying the creep behavior of the samples shows that the blends containing PH have more creep such that by substituting all of EPDM in the blends by PH the permanent deformation increases from 0.425% to 0.505%. According to the results, PH is introduced as a candidate for improving impact properties of iPP/iPP-g-MA/EPDM blend.
Synergistic effects of metal stearate, calcium carbonate, and recycled
polyethylene on thermo-mechanical behavior of polyvinylchloride
- Abstract: The thermo-mechanical recycling process is the cheapest way to recover plastic waste such as LDPE with low ecological impact. Thus, the goal of this work is to obtain high-performance microcomposites from polyvinyl chloride (PVC), recycled low-density polyethylene (r-LDPE), calcium carbonate (CaCO3), and calcium/zinc stearate (CaSt2/ZnSt2). The effect of the two ratios of thermal stabilizers with different concentrations on the mechanical properties and thermal stability of PVC and PVC/r-LDPE (1:1) blend were studied. The samples were characterized using infrared spectroscopy (FTIR), mechanical tests, thermal analysis, and scanning electron microscopy (SEM). The addition of 5 phr of CaSt2:ZnSt2 (9:1) to PVC (MC4) resulted in optimal tensile strength and elongation at break values. In addition, MC4 showed high thermal stability. Moreover, the incorporation of r-LDPE into PVC made the PVC matrix stronger and more stable than pure PVC, which yields high mechanical and thermal performances. Furthermore, an outstanding synergistic effect is obtained when a heat stabilizer rich in calcium is combined with CaCO3 and r-LDPE. This PVC/r-LDPE blend as waste a composite can be used in several industrial fields. 
Nitroxide mediated radical polymerization of styrene from poly(ethylene
terephthalate) and its polymer/montmorillonite nanocomposite
- Abstract: In this study, for the first time, a novel strategy for the synthesis of graft copolymers using polystyrene (PSt) monomer from surface modification of Poly(ethylene terephthalate) PET through surface-initiated nitroxide mediated radical polymerization was performed. For this purpose, the PET surface was first aminated by 1,3-diamino propane, which was used as an amination agent. Second, phenyl chloro acetylation of PET was prepared by coupling amino and hydroxyl groups with α-phenyl chloro acetyl chloride. Afterward, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was synthesized, then 1-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPO–OH) was obtained by reduce of TEMPO with sodium ascorbate and coupled with chloroacetylated PET to obtain PET-TEMPO macroinitiator. Furthermore, the (St) monomer was grafted onto PET surfaces through the “grafting from” technique. The obtained macroinitiator for living radical polymerization was heated in the adjacency of (St) monomer to obtain the graft copolymer (PET-g-PSt) onto PET surfaces. Finally, PET-g-PSt/MMt nanocomposite was synthesized by the solution intercalation method. The surface combination, morphology, and thermal properties of the modified PET films were proved using various characterization methods such as transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), Differential scanning calorimetric (DSC), thermogravimetric analysis, X-ray photoelectron spectroscopy, and termination electron microscopy (TEM).
Effect of different catalyst ratios on the ring-opening metathesis
polymerization (ROMP) of dicyclopentadiene
- Abstract: The polymerization process of polydicyclopentadiene (PDCPD) obtained by dicyclopentadiene (DCPD) and the 2nd generation Grubbs’ catalyst is optimized. The curing reaction kinetics was studied by differential scanning calorimetry (DSC), and the solidification reaction process was obtained. The effects of different ratios of monomer to catalyst on the product performance were investigated. And the current common modification methods of PDCPD have been summarized and improved. The results showed that with the increase of the ratio of monomer to the catalyst, the tensile strength and modulus, bending strength and modulus of PDCPD all showed a downward trend, and the impact strength showed an upward trend. When nDCPD: nCat =10000:1, the comprehensive mechanical properties of PDCPD reached the best. The bending modulus, tensile strength and impact strength of PDCPD achieved 2100 MPa, 52.4 MPa and 30 kJ/m2, respectively. The glass transition temperature (Tg) of PDCPD also showed a decreasing trend with the increase of the ratio of monomer to the catalyst, at this ratio, the Tg of the polymer reached 147.6 ℃. The catalyst concentration had a large effect on the product performance.
The effect of 5-ethylidene-2-norbomene or cyclopentene comonomers on the
micro-structures, mechanical and dynamic mechanical properties of
polydicyclopentadiene
- Abstract: The copolymerization reaction was carried out by adding different contents of 5-ethylidene-2-norbomene or cyclopentene to DCPD using an optimized polymerization process. The effects of different amounts of the comonomers on the conversion, mechanical properties and thermal stability of the polymer products were investigated and compared. The results showed that the addition of 5-ethylidene-2-norbomene accelerated the reaction rate and had little effect on the overall conversion rate of the reaction, while the addition of cyclopentene decreased the reaction rate and conversion rate. The tensile modulus and strength and flexural modulus and strength of the copolymer showed a trend of increasing and then decreasing with the increase of the comonomers content, reaching a peak at 5wt% of 5-ethylidene-2-norbomene or 3wt% of cyclopentene. At this peak condition, its impact strength can be improved by 50% compared to DCPD homopolymer. Below this peak condition, the Tg and thermal stability of the copolymer did not change significantly.
Foam rotational molding of hybrid polyethylene nanocomposites: synergistic
effect of microtalc and nanoclay
- Abstract: Rotational molding is a process used to produce seamless, one-piece, and hollow polymeric parts. Foam rotational molding has recently become an increasingly important process in the foam industry. However, foam rotational molding is still a challenging process to fabricate polymeric foams. The focus of this manuscript was to assess the effect of material parameters on the foam properties of samples produced by rotational molding. Rotational molding experiments were performed on a laboratory-scale two-axis rotational machine, designed and manufactured by the authors. The effects of microtalc as the nucleating agent, nanoclay as the reinforcing agent, and their synergetic effect were investigated on the cell density, cell size, and expansion ratio of hybrid microtalc/nanoclay polyethylene nanocomposites. The cell density was improved by 96% and 89% by addition of 1 wt% of microtalc and nanoclay, respectively, compared to pure polyethylene foams. The cell size was reduced by 20% and 17.5% in 1 wt% of microtalc and nanoclay, respectively. However, the synergetic effect of using both microtalc and nanoclay at 1 wt% was more significant compared to their individual effects. The cell density was enhanced by 313% and the cell size was decreased by 35% compared to pure samples.
Characterization of phthalate internal donor in MgCl2 supported
Ziegler-Natta catalyst by solid state 13C NMR
- Abstract: Ziegler-Natta catalyst for propylene polymerization, which TiCl4 and di-alkyl phthalate were supported on MgCl2, was analyzed by solid state 13C NMR. It was confirmed that the spin-lattice relaxation time (“relaxation time” hereafter) of carbonyl group in phthalate was shortened with increasing measurement temperature as a general manner because of the enhancing of molecular mobility at high temperature. The degree of the relaxation period reduction with temperature was influenced by the alkyl group size in phthalate molecule; larger alkyl group showed more shorting of the relaxation period. The short relaxation time should suggest weak interaction between phthalate molecule and MgCl2 support surface.The catalytic performance change was discussed by active site formation mechanism involving phthalate removal step. 
Regulation of Molecular Weight, Molecular Weight Distribution and
Branching Distribution in Polyethylene, Produced by Supported Catalysts
Bearing bis(imino)pyridyl Fe(II) and N,N-α-diimine Ni(II) Complexes
- Abstract: For preparation of highly active supported catalyst with bis(imino)pyridyl Fe(II) complexes (Fe1, Fe2) and N,N-α-diimine complex of Ni (Ni3) silica, modified with alumina (SiO2(Al), was used as a support. Data about the possibility to regulate molecular weight (MW) and molecular weight distribution (MWD) of polyethylene (PE), produced over the supported catalyst Fe1/SiO2(Al)+TIBA by variation of polymerization temperature, addition of hydrogen and hexene-1, are obtained. The prepared PE samples are characterized by Mw values varied from 80 to 350 kg/mol and various MMD (Mw/Mn=4.6-11.7).By grafting on SiO2(Al) of two different iron bis(imino)pyridyl complexes, producing PE with diverse MW, bi-component catalyst was prepared. This catalyst generates linear PE with broad and bimodal MWD (Mw/Mn=33). Fixation on SiO2(Al) of α-diimine Ni(II) pre-catalyst (Ni3), yielding high molecular weight branched PE at the ethylene homopolymerization, and bis(imino)pyridyl Fe(II) complex (Fe2) that forms lower molecular weight linear PE, affords formation of a new bi-component catalyst. The catalyst produces PE with broad MWD and high content of branches, concentrated in high molecular weight PE fraction.
The influence of the oxygen donor capacity of polystearylmethacrylate over
polyethylene bulk density when using modified methylaluminoxane as
co-catalyst
- Abstract: In this work, the interaction between a polystearylmethacrylate (Mn = 8,900 g mol-1, Xn = 26, Ð = 1.1) and modified methylaluminoxane 12 (MMAO-12) co-catalyst is studied using different spectroscopic methods. The effect of this oxygen-donor additive is measured by the changes in the bulk density of the raw polyethylene's which resulted increased respect to those obtained in blank reactions. A decrease in the activity is also observed as a penalty for the improvement of the bulk density enhancing the possibility of reducing fouling. The coordination of the carbonyl oxygens of polystearylmethacrylate to aluminum(III) centers is confirmed by 1H-NMR, FT-IR studies, and by a simple semi-empirical computational calculation. A method for obtaining a tri-component co-catalyst mixture is described making use of the methyl-bridging capacity of trimethylaluminum and its Lewis acidity to get the polystearylmethacrylate and MMAO-12 linked together. This robust adduct introduces a hierarchy over the PE chain growing, leading to higher bulk densities for PE beads (0.43 g cm-3) concerning blank reactions (0.26 g cm-3).
Preparation and characterization of nano WO3/Bi2O3/GO and BaSO4/GO
dispersed HDPE composites for x-ray shielding application
- Abstract: Researchers have studied the possibility of various polymer composites for radiation shielding applications. Lightness and non-toxicity of these materials are their significant advantages compared to Pb base traditional and common shields. In this research, Polyethylene (HDPE)-based composites for shielding against X- ray radiations were prepared by utilizing several weight fractions of the nano tungsten oxide, bismuth oxide, and barium sulfate which decorated on the nano graphene oxide (10, 15, 20, and 25 % wt.). Linear and mass attenuation coefficient value of the samples were investigated experimentally with a X-ray tube at radiology energy ranges and estimated theoretically by using MCNP code (Mont Carlo Nanoparticle program). Results illustrate that by increasing amount of the nanoparticles, the linear attenuation coefficient parameter and the absorbed dose values were increased dramatically. Shielding efficiency of the prepared samples has been shown by measuring HVL values. Furthermore, the effect of sample thicknesses on the attenuation properties of Nanocomposites was studied in this research The morphological properties of the samples were evaluated with SEM. Collected results showed that particle size of utilized nanoparticles had uniform dispersion in the polymer matrix. The mechanical properties of nano composite samples were characterized by DMTA and tensile test. Nano Composites containing 20, and 25 % of tungsten oxide, and bismuth oxide particles reached to 88 and 90 % of dose absorption, respectively.
Synthesis and assessment of the effect of monomer feed ratio and Lewis
acids on the copolymerization of Butyl methacrylate/1-octene
- Abstract: This study was designed to investigate the effect of molar ratio of 1-octene and type as well as concentration of Lewis acids on the free radical copolymerization of butyl methacrylate (BMA) with 1-octene. The synthesized copolymers have been substantially described by FTIR, 1H NMR, GPC and DSC. The quantitative 1H NMR and GPC demonstrated that by increase in the molar ratio of 1-octene and Lewis acids to BMA, the incorporation of 1-octene in the copolymer backbone enhanced, Mn reduced and polydispersity became narrower. The maximum incorporation of 1-octene (13.7%) was observed for sample CSC7 having [1-octene/BMA] of 3 mol% and [AlCl3/BMA] of 1.5 mol%. DSC results confirmed the NMR and GPC outcomes, suggesting a decrease in Tg by increasing 1-octene in the copolymer backbone. Moreover, it is found that temperature has a remarkable influence on the copolymerization behavior. The results also showed that by substituting the acrylate monomer from butyl methacrylate to butyl acrylate, the incorporation of 1-octene increased.