No description available.

No description available.

A variety of modified minerals have been screened to determine their effectiveness as agents for the catalytic transformation of the thermally generated off gases arising from the pyrolysis of the polyolefinic plastic High Density Polyethylene (HDPE). This polymer has been shown to degrade through a series of known mechanisms to yield a hydrocarbon product mixture consisting of an homologous series of saturated and unsaturated hydrocarbons which include alk-1-enes, n-alkanes, alk-x-enes and a-w-dienes. Modification treatments have been wide ranging having included activation of the parent mineral by means of pillaring, ion exchange and acid activation. The activated products have been characterised by XRD, XRF, TGA and vibrational spectroscopy. Moreover, evolved gas analysis has been employed to perform catalytic screening runs on these modified minerals. In particular, attention has been paid to the activity of these materials in respect of the formation of potentially fuel applicable hydrocarbons, namely those exhibiting high octane ratings, including aromatics and branched aliphatics from the feedstock species present in the HDPE pyrolysate gas mixture. Pillared clays (PILC's) have proven ineffective in this role as a consequence of their poor reproducibility and lack of selectivity towards the formation of single ring aromatics. Likewise, ion exchange has been found to influence strongly the catalytic behaviour of previously acid activated clays, with autotransformed samples offering dehydrocyclisation (DHC) activity at levels significantly greater than seen with some ion exchanged samples, particularly protons. Acid activated metakaolinites have demonstrated poor selectivity in terms of aromatic formation, although total DHC activity is good. Metakaolin also gave rise to appreciable activity in respect of the formation of the single ring aromatics selected for monitoring in this work. Isomerisation activity was prevalent over these materials, but coking levels were high. Acid activated smectites represent the most suitable candidates to fulfil the role of single step fuel generation from the transformation of the gas stream resulting from HDPE pyrolysis. It has been found that careful control over the chemical and physical properties of acid activated clays can be achieved through consideration of the severity of the activation parameters chosen to induce modification. In addition, the nature of the activated product is strongly dependant on the nature of the base clay. In particular, acid activated beidellites have been shown to exhibit high levels of surface acidity as determined through the thermal desorption of cyclohexylamine. These materials consequently give rise to respectable activity and selectivity in terms of the formation of highly octane rated methyl substituted single ring aromatics, principally trimethylbenzene. In contrast, acid activated montmorillonites have been seen to offer lower levels of total surface acidity and have been shown to be active in promoting skeletal isomerisation reactions to yield branched aliphatics, again, highly octane rated. This activity variation has been attributed to the formation of highly Bronsted acidic silanol containing Surface Localised Acid Pools (SLAP's) on the exposed surfaces of the former as a consequence of the isomorphous substitution patterns observed in the tetrahedral sheets of beidellites.

The effects of polyethylene, (PE), type, compatibilizer type and organoclay type on the morphology, rheological, thermal, and mechanical properties of ternary low density polyethylene (LDPE), high density polyethylene (HDPE), and linear low density polyethylene (LLDPE), matrix nanocomposites were investigated in this study. Ethylene &ndash / Methyl acrylate &ndash / Glycidyl methacrylate terpolymer (E-MAGMA) and Ethylene &ndash / Butyl acrylate- Maleic anhydrate terpolymer (E-BA-MAH) were used as the compatibilizers. The organoclays selected for the study were Cloisite 30B and Nanofil 8. Nanocomposites were prepared by means of melt blending via co-rotating twin screw extrusion process. Extruded samples were injection molded to be used for material characterization tests. Optimum amounts of ingredients of ternary nanocomposites were determined based on to the mechanical test results of binary blends of PE/Compatibilizer and binary nanocomposites of PE/Organoclay. Based on the tensile test results, the optimum contents of compatibilizer and organoclay were determined as 5 wt % and 2 wt %, respectively. XRD and TEM analysis results indicated that intercalated and partially exfoliated structures were obtained in the ternary nanocomposites. In these nanocomposites E-MA-GMA compatibilizer produced higher d-spacing in comparison to E-BA-MAH, owing to its higher reactivity. HDPE exhibited the highest basal spacing among all the nanocomposite types with E-MA-GMA/30B system. Considering the polymer type, better dispersion was achieved in the order of LDPE&lt / LLDPE&lt / HDPE, owing to the linearity of HDPE, and short branches of LLDPE. MFI values were decreased by the addition of compatibilizer and organoclay to the matrix polymers. Compatibilizers imparted the effect of sticking the polymer blends on the walls of test apparatus, and addition of organoclay showed the filler effect and increased the viscosity. DSC analysis showed that addition of compatibilizer or organoclay did not significantly affect the melting behavior of the nanocomposites. Degree of crystallinity of polyethylene matrices decreased with organoclay addition. Nanoscale organoclays prevented the alignment of polyethylene chains and reduced the degree of crystallinity. Ternary nanocomposites had improved tensile properties. Effect of compatibilizer on property enhancement was observed in mechanical results. Tensile strength and Young&rsquo / s modulus of nanocomposites increased significantly in the presence of compatibilizers.

No description available.

The effect of molecular weight on the dispersion of relatively polar montmorillonite (MMT) in non polar, unmodified high density polyethylene (HDPE) was examined. Polymer layered silicate (PLS) nanocomposites were compounded using three unmodified HDPE matrices of differing molecular weight and an organically modified MMT in concentrations ranging from 2 wt% to 8 wt% via single screw extrusion. The weight average molecular weights of the HDPE matrices used in this study ranged from 87,000 g/mol to 460,000 g/mol. X-ray diffraction (XRD), mechanical testing, dynamic mechanical thermal analysis (DMTA), as well as dynamic and capillary rheometry were performed on the nanocomposites. Nanocomposites generated from the high molecular weight (HMW) HDPE matrix exhibited increased intercalation of the MMT as shown by XRD as well as greater improvements in the Young's modulus compared to nanocomposites generated from both the low (LMW) and middle molecular weight (MMW) matrices. This was attributed to higher shear stress imparted to MMT during compounding from the more viscous matrix facilitating their separation and orientation during injection molding. DMTA showed that the torsional response of the HMW nanocomposites was not as great compared to their LMW and MMW counterparts as observed from a lower percentage enhancement in the storage modulus (Gâ ) and estimated heat distortion temperature (HDT) due to anisotropy in mechanical properties. Dynamic rheology indicated that a percolated network did not exist in any of the nanocomposites as shown by no change in the terminal behavior of Gâ upon addition of clay. / Master of Science

Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.

Defects in polyethylene film are often caused by contaminant particles in the polymer melt. In this research, particle properties obtainable from in-line melt monitoring, combined with processing information, are used to predict film defect properties. “Model” particles (solid and hollow glass microspheres, aluminum powder, ceramic microspheres, glass fibers, wood particles, and cross-linked polyethylene) were injected into low-density polyethylene extruder feed. Defects resulted when the polyethylene containing particles was extruded through a film die and stretched by a take-up roller as it cooled to form films 57 to 241mm in thickness. Two off-line analysis methods were further developed and applied to the defects: polarized light imaging and interferometric imaging. Polarized light showed residual stresses in the film caused by the particle as well as properties of the embedded particle. Interferometry enabled measures of the film distortion, notably defect volume. From the images, only three attributes were required for mathematical modeling: particle area, defect area, and defect volume. These attributes yielded two ”primary defect properties”: average defect height and magnification (of particle area). For all spherical particles, empirical correlations of these properties were obtained for each of the two major types of defects that emerged: high average height and low average height defects. Analysis of data for non-spherical particles was limited to showing how, in some cases, their data differed from the spherical particle correlations. To help explain empirical correlations of the primary defect properties with film thickness, a simple model was proposed and found to be supported by the high average height defect data: the “constant defect volume per unit particle area” model. It assumes that the product of average defect height and magnification is a constant for all film thicknesses. A numerical example illustrates how the methodology developed in this work can be used as a starting point for predicting film defect properties in industrial systems. A limitation is that each prediction yields two pairs of primary defect property values, one pair for each defect type. If it is necessary to identify the dominant type, then measurement of a length dimension of sufficient defects in the film is required.

Defects in polyethylene film are often caused by contaminant particles in the polymer melt. In this research, particle properties obtainable from in-line melt monitoring, combined with processing information, are used to predict film defect properties. “Model” particles (solid and hollow glass microspheres, aluminum powder, ceramic microspheres, glass fibers, wood particles, and cross-linked polyethylene) were injected into low-density polyethylene extruder feed. Defects resulted when the polyethylene containing particles was extruded through a film die and stretched by a take-up roller as it cooled to form films 57 to 241mm in thickness. Two off-line analysis methods were further developed and applied to the defects: polarized light imaging and interferometric imaging. Polarized light showed residual stresses in the film caused by the particle as well as properties of the embedded particle. Interferometry enabled measures of the film distortion, notably defect volume. From the images, only three attributes were required for mathematical modeling: particle area, defect area, and defect volume. These attributes yielded two ”primary defect properties”: average defect height and magnification (of particle area). For all spherical particles, empirical correlations of these properties were obtained for each of the two major types of defects that emerged: high average height and low average height defects. Analysis of data for non-spherical particles was limited to showing how, in some cases, their data differed from the spherical particle correlations. To help explain empirical correlations of the primary defect properties with film thickness, a simple model was proposed and found to be supported by the high average height defect data: the “constant defect volume per unit particle area” model. It assumes that the product of average defect height and magnification is a constant for all film thicknesses. A numerical example illustrates how the methodology developed in this work can be used as a starting point for predicting film defect properties in industrial systems. A limitation is that each prediction yields two pairs of primary defect property values, one pair for each defect type. If it is necessary to identify the dominant type, then measurement of a length dimension of sufficient defects in the film is required.

High density polyethylene (HDPE) is a widely used plastic but it is also a combustible material. One way of reducing flammability is to add fillers, such as magnesium hydroxide (Mg(OH)2). However, this has a deleterious effect on the mechanical properties of composites. It has been found that one possible method of restoring mechanical properties is to modifY the filler particles with coating agents, such as stearic acid. In the present work, this idea was taken a stage further with the use of various metal stearates (e.g. magnesium stearate, calcium stearate, and zinc stearate) for modifying filler. The fillers examined were magnesium hydroxide and calcium carbonate. A filler loading of 40% w/w was used in all samples. Samples were moulded into a variety of shapes for mechanical testing. Such tests included, tensile, flexural, and impact testing. To obtain deeper understanding of the effect of the coating agents on the fillers, a variety of fundamental tests were carried out. These included Diffuse Reflectance FTIR (DRIFT), Thermal Analysis using a DSC cell, Xray Diffraction (XRD), contact angle measurement. Unfilled HDPE, uncoated filled-HDPE, and coated filled-HDPE were compared using uncoated filled-HDPE as a base line. Uncoated filled-HDPE is more brittle than unfilled HPDE. Surface modification of filler improves the toughness properties. Comparing coated filled-compounds, stearic acid and zinc stearate caused a small improvement, magnesium stearate improved the properties significantly with calcium carbonate while calcium stearate gave the best results for coating magnesium hydroxide. One monolayer coating gave the best compound properties compared to other degrees of coating. Although, tensile/flexural strength was not greatly affected elongation at yield, extension at maximum load, and impact properties increased significantly. DSC was used to observe the disappearance and conversion of coating agents as coating proceeded. X-ray diffraction showed the effect of injection moulding on the orientation of the filler and polymer. During coating of the filler particles, XRD and DSC were used to follow incorporation of stearate particles to produce the monolayer coverage. Surface free energy results showed that surface modification of filler resulted in the reduction of hydrophilicity of filler leading to tougher composites compared with uncoated filled-compounds.