Composites and nanocomposites
Tohid Abdolahzadeh; Jalil Morshedian; Shervin Ahmadi
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 ...
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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 were decorated on nanographene oxide (10, 15, 20, and 25 wt%). The linear and mass attenuation coefficient values of samples were investigated experimentally with an X-ray tube at radiology energy ranges and estimated theoretically by using MCNP code (Mont Carlo Nanoparticle program). Results illustrate that by increasing the nanoparticles content, the linear attenuation coefficient parameter and the absorbed dose values increased dramatically. The shielding efficiency of the prepared samples has been shown by measuring the 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. The collected results showed that the particle size of the nanoparticles used has a uniform dispersion in the polymer matrix. The mechanical properties of nanocomposite samples were characterized by DMTA and tensile test. Nanocomposites containing 20% and 25% of tungsten oxide and bismuth oxide particles reached to 88% and 90% dose absorption, respectively.
Polymer processing
Mohammadreza Rahnama; Abdulrasoul Oromiehie; Shervin Ahmadi; Ismaeil Ghasemi
Abstract
In this research, high oxygen-barrier films were organized based on low-density polyethylene (LDPE)/ ethylene vinyl alcohol (EVOH)/ polyethylene-grafted maleic anhydride (LDPE-g-MA) compatibilizer. The effects of 10–30 wt. % EVOH and 0–10 wt. % LDPE-g-MA loadings on the properties of final ...
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In this research, high oxygen-barrier films were organized based on low-density polyethylene (LDPE)/ ethylene vinyl alcohol (EVOH)/ polyethylene-grafted maleic anhydride (LDPE-g-MA) compatibilizer. The effects of 10–30 wt. % EVOH and 0–10 wt. % LDPE-g-MA loadings on the properties of final films were evaluated. The morphology of specimens was observed by using scanning electron microscopy (SEM). Oxygen transfer rate (OTR) results revealed that the addition of EVOH up to 30 wt. % to neat LDPE could significantly decrease oxygen permeability. The LDPE-g-MA which increased the permeability needed to be fine-tuned its amount based on the EVOH loading in different samples. The experimental results revealed that the addition of 30 wt. % EVOH to the LDPE matrix without adding LDPE-g-MA gave the best oxygen barrier properties. Elastic modulus and tensile strength increased with incorporation of EVOH and LDPE-g-MA into the polyethylene matrix. On the other hand, elongation-at-break decreased with the addition of EVOH and increased with the introduction of compatibilizer to the samples. Incorporation of EVOH and LDPE-g-MA into the LDPE matrix and increasing their amounts led to higher storage modulus and zero shear rate viscosity, but lowered the frequency value at the intersection point of storage modulus (G') and loss modulus (G''). The only exception was that in the samples without compatibilizer, the increase in the EVOH content resulted in a lower zero shear rate viscosity and a higher frequency value at the intersection point of G' and G''.
