Low Density Poly Research Articles

Thermal and rheological characterization of antibacterial nanocomposites

In this study, the filler–matrix interactions are assessed in two nanocomposites having different antibacterial activity. The two polymers used as matrix are poly(amide) 6 (PA6) and low-density poly(ethylene) (LDPE). The filler, zinc oxide (ZnO) nanoparticles, with a content as low as 1 w/w% in the polymers showed great antibacterial activity against Escherichia coli and Staphylococcus aureus. However, the bacterial slaying capability of composites was found better when ZnO was dispersed in PA6, where the efficiency is similar to pure ZnO particles. The dispersion of ZnO and its interactions with the matrix have been investigated by means of scanning electron microscope, rheology, thermogravimetric analysis and differential scanning calorimeter. This study shows stronger interactions of ZnO particles with LDPE, which could have an effect on final antibacterial properties.

Three‐dimensional density measurements of ultra low density materials by X‐ray scatter using confocal micro X‐ray fluorescence spectroscopy

Targets used in high energy density physics experiments, such as those fielded at the National Ignition Facility, are typically made of multi‐component systems that include metals, metal coatings, and very low density materials. These very low density materials with densities as low as ~10 mg/cm3 must have uniform density throughout. Characterizing their density in 3D is a very difficult problem. One technique used is confocal micro X‐ray fluorescence. This technique, which uses a polycapillary optic to focus the X‐rays from the X‐ray source and another on the detector, measures the density of these materials based upon their X‐ray scatter. In order to gain a complete picture of their X‐ray scatter, the sample is rastered in 3D to generate a complete 3D density map. As proof of technique, the examination of very low density poly(styrene‐divinylbenzene) foams, poly(methylpentene) foams, as well as silica aerogels were completed. Results for the polymer foam materials show a linear correlation (R2 = 0.99) between X‐ray scatter intensity and bulk density. However, for higher atomic number materials (e.g. aerogels) the amount of X‐ray scatter is very dependent upon the depth of data collection as a result of the absorption of the X‐rays by the upper portions of the sample. This self‐absorption reduces the ability of this technique to quantify the density of the material in full 3D. Self‐absorption modeling will be required to compensate. Scans through the aerogel surface indicate an increased density at the surface due processing. Finally, a 3D image of a machined aerogel tube is presented. Copyright © 2012 John Wiley & Sons, Ltd.

Melt Strength and Extensional Viscosity of Low-Density Polyethylene and Poly(butylene succinate) Blends Using a Melt-Spinning Technique

The melt strength (MS) and extensional viscosity of low-density polyethylene/poly(butylene succinate) (LDPE/PBS) blends were measured using a melt-spinning technique to investigate the effects of extrusion conditions and mixing ratios on the extensional flow. The experimental results indicated that maximal extensional length and MS of the LDPE/PBS blends decreased with an increase of PBS content. The response of the MS to the extrusion rate depended on the components of the blends. The extensional viscosity of the LDPE/PBS blends decreased with the increases of PBS content, extrusion rate, and extensional strain rate. Extensional master curves were suitable for the LDPE/PBS blends, and the scaling factor decreased with the increase of extrusion rate according to a power law. When the PBS content was not more than 40%, with the further increase of the PBS content, the sensitivity of the scaling factor to the extrusion rate decreased. However, when the PBS content was 60%, the sensitivity of the scaling factor to the extrusion rate increased, and was close to the sensitivity of the LDPE melt. Based on the extensional master curve and the back propagation (BP) neural network model, predicted extensional viscosities were compared with the experimental results.

Migration study of optical brighteners from polymer packing materials to jam squeeze and fruit drink by spectrofluorimetry and RP-HPLC methods.

Optical brighteners are commonly used to modify the appearance and to improve polymer properties of packaging. They are not chemically bound to polymers and able to migrate from packaging into the foods. These migrants are potentially harmful to human health. In concern with human safety an approach was made to analyze three optical brighteners such as diphenylbutadiene, Uvitex-OB, benzophenone in commercial fruit juice and jam. The migration level of these optical brighteners from low density poly ethylene packaging into fruit juice and jam was studied. Two optimized and validated analytical techniques such as spectrofluorimetry and high performance liquid chromatography with photo diode array detector used for migration study. Both methods have shown high correlation coefficients (>0.999), over a concentration range of 0.1-3.2μg/mL, 0.1-1μg/mL, 0.05-3.2μg/mL for diphenylbutadiene, Uvitex-OB and benzophenone respectively. The preliminary studies confirm that the low density poly ethylene layer taken for study contained of diphenylbutadiene and the other two were absent. The migration level of diphenylbutadiene was studied at room temperature and different elevated temperature from 30°C to 60°C for up to 3weeks. At room temperature no migration of diphenylbutadiene was observed where as at higher temperature migration could be observed. The maximum quantity of diphenylbutadiene migrated was found to be 0.0462mg/kg from tetrapak, and 0.0382mg/kg from jam squeeze after 3weeks treatment at 60°C. The migration of diphenylbutadiene was found to be less than allowable concentration during the study period.

Comparison of partial discharge characteristics and degradation in several polymeric insulators

Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. These materials are degraded, however, when they are subjected to partial discharge (PD) with different polymeric materials possessing different levels of PD resistance. In this study the PD characteristics and degradation caused by PD are analysed and compared for four different polymers – poly(ether sulphone) (PES), poly(ethylene terephthalate) (PET), poly(propylene) (PP) and low-density poly(ethylene) (LDPE). An artificial void is created in each of the polymer samples and electrically stressed above PD inception voltage (PDIV) for 4 h. The simulated electric field distribution inside the void for each of the polymer materials at the respective PDIVs is modelled using COMSOL to validate the experimental results. Little work has correlated void PD characteristics with material degradation induced by PD across a range of different polymers and subsequently categorised them according to their PD resistances. This study therefore presents a comparative study of the N–Q patterns of PD pulses (a plot of the number of discharges against the measure of apparent charge), PD repetition rate and the chemical and morphological changes occurring on the void surfaces for each type of polymer. The results show that the PD resistance of these four polymers can be categorised in a decreasing order according to the following sequence: LDPE, PP, PET and PES with LDPE being most resistant to PD and PES the least resistant.

NANO REACTIVE POLYMER BASED ON POLYANILINE AS ASPHALT MODIFIER FOR ANTICORROSION APPLICATION

Recently, the application of nanotechnology in the corrosion protection of metals has gained momentum. On the other hand, polymers are used as corrosion inhibitor coatings that are physically, chemically or electrochemically deposited on the metal substrate. Although asphalt has low cost, high cohesive nature, rheological properties and high thermal resistance but it is not practically used on a large scale in anticorrosion applications. So, the aim of this research is to use the nanotechnology science in preparing modified asphaltic materials to produce new and more qualified anti-corrosive coatings. To achieve this aim, nanoparticles of polyaniline (PANI-H2SO4) using template free polymerization method are prepared and characterized by FTIR, XRD and SEM. Another nonreactive polymer of type low density poly ethylene (LDPE) has been used for comparison purpose. The two types of modifiers have mixed with asphalt of type 85/25 in different percentages as 2, 4, 6, 8& 10

Effect of Cobalt Stearate and Vegetable Oil on Uv and Biodegradation of Linear Low-Density Poly(Ethylene)-Poly(Vinyl Alcohol) Blends

The main objective of this study was to enhance the rate of UV and biodegradation of polyethylene by incorporating biodegradable materials and prooxidants. Prooxidants such as transition metal complexes are capable of initiating photooxidation and polymer chain cleavage, rendering the product more susceptible to biodegradation. In this work, the effect of (1) a metallic photoinitiator, cobalt stearate, and (2) different combinations of cobalt stearate and vegetable oil on the photooxidative degradation of linear low-density poly(ethylene)-poly(vinyl alcohol) (LLDPE/PVA) blend films has been investigated. For this, film-grade LLDPE was blended with different proportions of PVA. PVA is widely used in the industrial field, and recently it has attracted increasing attention as a water-soluble biodegradable polymer. Cobalt stearate and vegetable oil were added to the blends as prooxidants. The blends were prepared by melt mixing in a Thermo HAAKE Polylab system. Thin films containing these additives were prepared by a subsequent compression moulding process. The effect of UV exposure on LLDPE/PVA films in the presence as well as absence of these additives was investigated. Tensile properties, FTIR spectra, and scanning electron microscopy (SEM) were employed to investigate the degradation behaviour. It was found

The effect of electrode parameters on the performance of anion exchange polymer membrane fuel cells

An investigation of several electrode parameters on performance of an alkaline membrane fuel cell is described. The studied parameters were: ionomer content, anode and cathode catalyst layer thickness, electrode aminating agent and membrane thickness. It was found that an optimum ionomer content depended on a balance between the OH − ion/water mobility and the oxygen solubility/diffusivity through it and which varied with temperature. Thick catalyst layers were necessary for the anode as thin anode catalyst layers suffered from flooding. 40%Pt/C provided the best thickness (with loading of 0.4 mg Pt cm −2) for cathodes operating with air. An aminated low density poly(ethylene- co-vinyl benzyl chloride) (LDPE-VBC) membrane was shown to be a good membrane for an alkaline membrane fuel cell, giving conductivities up to 0.13 S cm −1 at 80 °C. A Membrane Electrode Assembly (MEA) utilizing this membrane with fully hydrated thickness of 57 μm produced good peak power density, at a high potential of 500 mV, of 337 mW cm −2 with air (1 bar gauge) at 60 °C.

Partition coefficients of organic molecules in squalane and water/ethanol mixtures by molecular dynamics simulations

Accurate partition coefficient data of migrants between a polymer and a solvent are of paramount importance for estimating the migration of the migrant over time, including the concentration of the migrant at infinite time in the two solvents. In this article it is shown how this partition coefficient can be estimated for both a small hydrophilic and a hydrophobic organic molecules between squalane (used here to mimic low density poly ethylene) and water/ethanol solutes using thermodynamic integration to calculate the free energy of solvation. Molecular dynamics simulations are performed, using the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard–Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the OPLS-AA (all-atom). The computational cheaper TraPPE-UA force field showed to be more accurate over the whole range of systems compared to the OPLS-AA force field. Moreover, some of the calculations were done with five different water models to investigate the influence of the specific water model on the calculations. It was found that the combination of the TraPPE-UA force field and the TIP4p water model gave the best results. Based on the methodology proposed in this article, it is possible to obtain good partition coefficients only knowing the chemical structure of the molecules in the system.

Rheological and mechanical properties of poly (ethylene acrylic acid) and low density polyethylene blends

AbstractRheological properties of poly (ethylene‐acrylic acid) (PEA) and low density poly ethylene (LDPE) blends having varied amounts of LDPE from 0 to 100% have been evaluated at different temperatures (115, 120, and 130°C) and shear rates (61.33–613.30 s−1) using a Monsanto processability tester. A reduction in the melt viscosity of the PEA/LDPE blends was noticed with increasing the shear rate. The observed positive deviation in the experimental melt viscosities of the blends is an indication of the synergy present in the blends during melt processing. The activation energy (Ea) of flow calculated using Arrhenius relation for PEA, LDPE, and their respective blends lies in the range 29.98–40.56 kJ mol−1. The experimental activation energy of flow of the blends was higher than that obtained from the additivity rule. Highest activation energy was noticed for the blends containing 60–80% by weight of LDPE in PEA/LDPE blends, which is an indication for the miscibility of the blends at these ratios. The physicomechanical properties such as density, tensile behavior, tear strength, and hardness (Shore A) of PEA, LDPE, and their blends have been evaluated as a function of varying amounts of LDPE. The obtained physicomechanical properties of the PEA/LDPE blends lie in between that of pure polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Life Cycle Assessment of multilayer polymer film used on food packaging field

The environmental impact of a multilayer polymer film, Low Density Poly Ethylene/Polyamide system (LDPE/PA), generally used on food packaging field, was estimated using life cycle assessment (LCA). The aim of the work was to understand how to reduce the environmental pressure from plastic packages for its lower recovery and reuse, which can be improved by developing material recovery or other appropriate recycling technology to improve the cyclic materials flows and recycling ratio. LCA is a tool specifically developed for assessing the overall environmental burden of a product, including the system used for manufacturing it and its end-of-life treatment. This work provides a cradle-to-grave LCA study of a food packaging envelope made with a multilayer polymer film, with two different depth of 70 and 90 micron, and a study of the possibility to utilize a 50% of recycled LDPE and PA polymer pellets in order to reduce the environmental impact. A one square meter envelope is used as functional unit.

TPX Foams for Inertial Fusion Laser Experiments: Foam Preparation, Machining, Characterization, and Discussion of Density Issues

Low density foams (in this work, foam density refers to apparent density) are materials of interest for fusion experiments. Low density poly(4-methyl-1-pentene) (commercial name TPX) foams have been produced for ˜30 years. TPX foams have been shown to have densities as low as 3 mg·cm-3, which is very close to air density (1.2 mg·cm-3). Around this density foams are very light and highly fragile. Their fabrication is thus a real technological challenge.However, shrinking always appears in ranges ranking from 25% to almost 200%. As a result, the apparent density of the final foam never matches the expected value given by the precursor solution concentration. Besides, even if the mold dimensions are precisely known, shrinkage is never linear, and foams have to be machined for precise density measurement.In our work we present a fabrication process for TPX foams and discuss machining and density measuring issues.Particularly, we have found that there are volume and weight limits for a determination of density within the range of 3% uncertainty. This raises the question whether density should rather be determined directly on millimeter-sized targets or should be performed on a bigger scale sample prepared from the same batch.

Dimensional Standard for Micro X-ray Computed Tomography

The decrease in the cost of high end computing and the availability of high quality X-ray sources in the laboratory environment has led to an increased use of three-dimensional (3D) X-ray micro computed tomography (μCT). In the medical community, the primary concern for CT is calibrating for X-ray absorption and ascertaining the difference between healthy tissue and cancerous tissue or examining fractures. Absorption calibration is also important in the materials community, however confirming dimensional accuracy of voids, defects, machined parts, cracks, or the distribution of dispersed particles is typically more important. One key aspect of μCT that is often overlooked in the literature is the number of radiographs required for dimensional accuracy of the 3D reconstruction and minimization of image noise. In μCT, a number of radiographs are collected in theta increments as the sample is rotated at least 180°. They are typically collected in 1° increments (or 181 radiographs), 0.25° increments (721 radiographs), or some other multiple. The question that arises, especially in a laboratory based instrument, where the required exposure times are longer to get high-quality signal-to-noise compared to synchrotron sources, is what is the optimal number of images required to reach the volumetric statistics of the sample, and minimize the noise while not overly scanning the sample at a cost in time? A dimensional standard based upon NIST certified glass microspheres dispersed in a low density poly(styrene) matrix to answer this question is proposed. Experiments are shown that describe the microsphere size statistics as a function of number of radiographs calculated using a commercial software package, AvizoFire. These results are important in understanding the distribution of voids in a foam and confirming the accuracy of the 3D measurements obtained.

Effect of multiwalled carbon nanotubes on tensile stress-strain diagrams of amorphous-crystalline thermoplastic polymers

The effect of multiwalled carbon nanotubes (MWNTs) on the stress-strain diagrams of uniaxially extended thin films of low-density polyethylene (LDPE) and poly(vinyl alcohol) (PVA) has been studied. MWNTs were synthesized by the thermocatalytic method. The introduction of MWNTs decreases the plasticity of LDPE, while significantly increasing that of PVA. The results can be explained by assuming that crystallites are key structural elements that ensure large plastic deformation. The manifestation of the plasticity of crystallites implies that amorphous regions occur in a rubberlike state. Both of these prerequisites are important for the mechanics of amorphous-crystalline thermoplastic polymers.

Synthesis and characterizations of Cd2+, Pb2+ and Sr2+ containing divinyl monomers and their melt grafting reaction with LLDPE: an FTIR approach

The divinyl esters containing divalent metal ions like Cd, Pb and Sr are synthesized and characterized by various analytical tools such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, thermogravimetric analysis and X-ray diffractogram. Further, it is subjected to melt graft functionalization reaction with linear low-density poly(ethylene) (LLDPE) at 160 °C under inert atmosphere. The FTIR–relative intensity method is used to calculate the % grafting of metal esters onto LLDPE backbone. The results are critically compared and discussed. Suitable reaction mechanism is proposed.

Melt grafting of metal salts onto LLDPE backbone – An FTIR study

The melt graft functionalization of metal di(meth)acrylates onto linear low density poly(ethylene) (LLDPE) at 160 °C under inert atmosphere is reported here. The post melt grafting FTIR–RI method was used to find out the % grafting of metal salts onto LLDPE backbone. Further, DSC, TGA and HRTEM techniques were introduced to explain the results. A plausible reaction mechanism was proposed.

Oxidation and biodegradation of polyethylene films containing pro-oxidant additives: Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation

Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation on the oxidation and biodegradation of linear low density poly(ethylene) PE-LLD films containing pro-oxidant were examined. To achieve oxidation and degradation, films were first exposed to the sunlight for 93 days during the summer months followed by their incubation with fungal strains previously isolated from the soil based on the ability to grow on the oxidized PE-LLD as a sole carbon source. Some films were also thermally aged at temperatures ranging between 45°C and 65 °C, either before or after fungal degradation. Films with pro-oxidant additives exhibited a higher level of oxidation as revealed by increase in their carbonyl index (CO i). In addition to increase in the CO i, films showed a slight increase in crystallinity and melting temperature ( T m), considerably lower onset degradation temperatures, and a concomitant increase in the % weight of the residues. The level of oxidation observed in thermally aged films was directly proportional to the aging temperature. The PE-LLD films with pro-oxidant exposed to sunlight followed by thermal aging showed even higher rate and extent of oxidation when subsequently subjected to fungal biodegradation. The higher oxidation rate also correlated well with the CO 2 production in the fungal biodegradation tests. Similar films oxidized and aged but not exposed to fungal biodegradation showed much less degradation. Microscopic examination showed a profuse growth and colonization of fungal mycelia on the oxidized films by one strain, while another spore-producing strain grew around the film edges. Data presented here suggest that abiotic oxidation of polymer's carbon backbone produced metabolites which supported metabolic activities in fungal cells leading to further biotically-mediated polymer degradation. Thus, a combined impact of abiotic and biotic factors promoted the oxidation/biodegradation of PE-LLD films containing pro-oxidants.

Processibility and Miscibility Studies of Uncompatibilized Linear Low Density Polyethylene/Poly(Vinyl Alcohol) Blends

This work investigates the processibility and miscibility of linear low density polyethylene (LLDPE) and poly(vinyl alcohol) (PVA) blends. The linear low density polyethylene/poly(vinyl alcohol) was blended to give the following blend ratio (wt%): 100/0, 90/10, 80/20, 60/40, 50/50, 40/60. The blends were melt mixed using a Haake Rheometer at 150°C and 50 rpm for 10 min. Thermal properties and morphology of the blends were investigated by using differential scanning calorimetry and scanning electron microscopy (SEM). The effect of blend ratio on tensile properties of LLDPE/PVA blends was also examined. Both components were immiscible, as been confirmed by double melting temperature, corresponding to linear low density polyethylene and poly(vinyl alcohol). Increasing content of poly(vinyl alcohol) resulted in decreased in the tensile strength and elongation at break but an increased in Young's modulus of linear low density polyethylene/poly(vinyl alcohol) blends up to a certain level beyond which these values gradually decreased. Evidence of immiscibility of LLDPE/PVA blends was also confirmed by the presence of agglomerates as revealed by SEM. It was purposed that the difference in degree of polarity contribute to the low miscibility between the two components.

Synthesis and characterizations of calcium di(meth)acrylate divinyl monomers and melt surface graft functionalization with linear low density poly(ethylene)

AbstractCalcium diacrylate (CDA) and calcium dimethacrylate (CDM) divinyl monomers were synthesized by a solvo thermal method. The FTIR spectra showed a peak at 1650 cm−1 due to the presence of a CC for both CDA and CDM. Proton NMR and carbon NMR confirmed the structure of CDA and CDM synthesized by a solvo thermal method. DSC determined the melting temperatures of CDA and CDM. XRD indicated the presence of a d110 plane peak for CDA and CDM. The % weight residue that remained above 700°C in TGA method confirmed the higher thermal stability of CDA. Thus, synthesized CDA and CDM were surface grafted on linear low density poly(ethylene) (LLDPE) at 160°C under inert atmosphere by thermolysis method. FTIR confirmed the presence of CO stretching due to CDA and CDM in LLDPE backbone after thermolysis reaction. 1H‐NMR confirmed the chemical grafting of CDM onto LLDPE. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Modeling the phase behavior in binary mixtures involving blowing agents and thermoplastic resins

AbstractThe thermophysical properties of mixtures of thermoplastic resins and blowing agents, together with the knowledge of the solubilities of these components, are the basis for the manufacturing of plastic foams. In this work, the solubilities of blowing agents trichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromehane, and 1,2‐dichloro‐1,1,2,2‐tetrafluoroethane in thermoplastic resins poly(styrene), high density poly(ethylene), low density poly(ethylene), poly(propylene), poly(vinyl chloride), poly(carbonate) and poly(propylene oxide) were modeled by using the Perturbed Chain‐Statistical Associating Fluid Theory (PC‐SAFT) and the Sánchez‐Lacombe equations of state (EoS), fitting a single temperature‐dependent binary interaction parameter. PC‐SAFT is a theoretically based equation of state with three pure component parameters that describe efficiently the thermodynamics of complex systems. Earlier works with this EoS have already predicted the phase coexistence properties of various refrigerants and higher order alkane series compounds, along with their mixtures. The pure component parameters for the blowing agents were obtained by regression of vapor pressure and liquid density data, while the pure component parameters for the thermoplastic resins were obtained by regression of pure liquid PVT data. The parameter estimation was performed by using a modified maximum likelihood method. The solubility results obtained with both EoS have been compared; the results from PC‐SAFT showed a higher accuracy in terms of solubility pressure deviations. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers