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Conference Proceedings
The Effect of Additives on the Processing and Physical Properties of Recycled Polyethylene Terephthalate (RPET)
Mark Kegel, Igor Sbarski, Edward Kosior, Syed Masood, May 2002
This paper describes the effect of individual additives that are present in masterbatch formulations, and the role they play in modifying physical properties and processability of blends based on RPET. Additives such as titanium dioxide, carbon black, linear low-density polyethylene and polyethylene wax are often incorporated in masterbatch compositions. The blends based on these additives have been analysed for shifts in thermal transition points, levels of crystallinity and physical properties such as tensile and impact strength. The results show that at the addition rates used, some additives had significant effects on processability and crystallinity, negligible effects on physical properties and antagonistic effects were noted when additives were combined.
Effect of Aging on Film Properties of Ethylene-Alpha Olefin Copolymers
H. Mavridis, May 2002
Film toughness of certain ethylene – alpha olefin copolymers of high impact strength, shows significant aging effects, decreasing with time. In this work we studied the time and temperature dependence of film aging of several copolymers of varying molecular structure. Film aging appears to be associated with the presence of highly branched polymer chains (>30 branches per 1000 carbon atoms). It is speculated that the thermally activated rearrangement of such branched species, over time and under film storage conditions, leads to film aging. Higher film storage temperatures lead to faster aging. It is possible to employ an “accelerated aging” testing protocol, so as to obtain longer-term aged data from a short-term test, which would be useful in an industrial production setting.
The Effect of Boron Nitride on the Rheological Properties and Processability of Polyethylene
Sang Myung Lee, Jae Wook Lee, May 2002
The processability of the polymer in capillary extrusion is closely related to the interface between the polymer melts and die wall, and wall surface energy affects the flow of polymer melts in extrusion dies. In this paper, when used Boron Nitride (BN) with low surface energy as the processing aid, we studied about changes of the rheological behavior and processability of metallocene polyethylene (m-LDPE). It also studied about the effect of the hot-pressed BN die on the instability of capillary flow. The equipment used includes a capillary rheometer with two kinds of dies, namely the tungsten carbide and hot-pressed BN dies. The rheological properties of resins with and without BN particles were analyzed by parallel-plate and capillary rheometers. Two types of BN powders with a different the agglomerated particle size and distribution, are tested at various contents. It was found that the BN powder has an influence on the processability of the polymer, depending on the BN content and particle size.Lastly, it must be underlined that it is possible to significantly delay or eliminate the melt fracture, by considering the polymer flow through the hot pressed BN die instead of the tungsten carbide die.
The Effect of Calcium Carbonate Size and Loading Level on the Impact Performance of Rigid PVC Compounds Containing Varying Amounts of Acrylic Impact Modifier
William S. Bryant, Henry E. Wiebking, May 2002
This study demonstrates how the impact performance of a rigid polyvinyl chloride (PVC) compound can be affected by the particle size of the calcium carbonate filler and its loading level. The test compounds contain 0 to 8phr of acrylic impact modifier and fillers ranging in size from 3 to 0.07 microns. By taking all three variables into consideration one can, not only optimize a compound's performance, but also lower its cost. Notched Izod and falling weight impact data will be reviewed. Flexural modulus and low temperature impact data are also included.
The Effect of Carbon Dioxide on the Viscoelastic Properties of an Epoxy Resin: CO2 Pressure Jumps
Francesco Briatico-Vangosa, Mataz Alcoutlabi, Gregory B. McKenna, May 2002
We report results from tensile creep tests performed on an epoxy resin in the presence of carbon dioxide pressure (Pco2) at a constant temperature below the glass transition temperature Tg. Time - Pco2 superposition was applied to the data to account for the plasticization effect due to the interaction between the carbon dioxide molecules and the polymer. In addition, physical aging of the epoxy films was investigated using sequential creep tests after carbon dioxide pressure down-jumps at constant temperature and also after temperature down-jumps at ambient carbon dioxide pressure. The isothermal pressure down-jump experiments showed physical aging responses similar to the isobaric temperature down-jump experiments. However, the aging rate for the CO2–jump was lower than that for the T-jump.
Effect of Chemical Modification on Polyolefin Crystalline Structures
N. Villarreal, J.M. Pastor, R. Perera, C. Rosales, J.C. Merino, May 2002
A thermal treatment of Successive Self-Nucleation and Annealing (SSA) of LDPE, LLDPE, PP, PP grafted with diethyl maleate and PP grafted with maleic anhydride were made. The study of these materials was combined using capillary rheometry, DSC measurements, FTIR and Low-Frequency Raman-Active Longitudinal Acoustical Mode (LAM). The results indicated that the grafting process mechanism in a co-rotating twin-screw extruder and their effects on the polyethylenes structures occur through secondary carbons. The SSA technique is a useful tool for the characterization of grafted PEs. However, more work is needed for the grafted MA polypropylenes.
The Effect of Cure Conditions on the Mechanical, Shore Hardness and Frictional Properties of Styrene Butadiene Rubber for Industrial Conveying Applications
G.M. Mc Nally, J.L. Clarke, C.M. Small, W.J. Skelto, V. Monroe, May 2002
A range of samples were prepared from a commercial styrene butadiene rubber (SBR), over a range of cure temperatures (140°C – 170°C) and cure times (30min – 120min), using a high temperature moulding press held at a constant pressure of 5000 psi. Mechanical analysis of the various samples showed considerable increase in modulus, shore hardness and break strength with progressive increase in cure temperature, especially at lower cure times. Dynamic frictional analysis under different loadings, of the SBR samples with HMWPE and 90 Shore A Polyurethane (PU), showed progressive decrease in frictional force with increase in SBR cure temperature and time. Some reversion of the SBR was shown to occur at higher temperatures and longer cure times.
Effect of DCP Crosslinking on the Mechanical and Electrical Properties of LDPE
M. Rafizadeh, S. Mohseni, May 2002
The good electrical and mechanical properties of low density polyethylene (LDPE) make it an ideal insulation for the electric cables. The main draw back of polyethylene is its softening temperature. Crosslinking of polyethylene improves its properties.The effect of dicumyl peroxide (DCP) on mechanical, thermal and electrical properties of crosslinked polyethylene (XLPE) have been investigated. Crosslinking of LDPE improves its mechanical properties and, to some extent, improves its thermal degradation. DCP increases dielectric breakdown voltage, elongation at break, tensile strength and gel-content of XLPE, but decreases young modulus, crystallinity, heat of fusion and melting point of XLPE.According to the results, an optimized amount of DCP is determined. In this study, the LDPE (POLIRAN LF0200) was used to produce insulators for medium and high-voltage electrical cables.
The Effect of Extrusion Processing Conditions and Polyisobutylene Concentration on the Properties of Polyethylene for Stretch and Cling Film Applications
C.M. Small, G.M. Mc Nally, A. Marks, W.R. Murphy, May 2002
A range of LLDPE films with polyisobutylene (PIB) content from 2%-8% was manufactured using a Killion blown film extrusion system and a cast film extrusion system. The films were aged at 25, 35 and 45°C for up 28 days, to enable tack (cling) development. The results show that tack, in both blown and cast films, improved significantly with ageing, at increased storage temperatures and at higher film blow up ratios. DSC analysis showed only a slight decrease in film crystallinity with increasing PIB concentration. The film tensile modulus, elongation and tear properties in both MD and TD were not significantly affected by increase in PIB concentration.
The Effect of Extrusion Processing Conditions on the Thermal and Mechanical Performance of Extrusion Cast Metallocene Polyethylene Films
B.G. Millar, G.M. Mc Nally, W.R. Murphy, May 2002
Cast extruded films were prepared from a range of mPE resins with various co-monomer types (hexene, octene), using different chill roll temperatures from 30 to 60°C. Mechanical analysis showed that the tensile modulus of the films increased with progressive increase in chill roll temperature. DSC analysis showed increases in crystallinity with increasing quench temperature and decreasing MFI. Rheological and molecular weight distribution analysis showed that activation energies of flow for mPE (18-28kJ/mol) were low, this is attributable to the narrower polydispersity of mPE (2.1-3.1) compared to the wider distribution of conventional polyethylenes (4.0-5.0).
Effect of Fluoropolymer Processing Aids on the Processibility of an Octene LLDPE
Kasinath Nayak, Mohan Gownder, Glen Giacoletto, May 2002
Polymer processing additives (PPA) have found their niche in the extrusion and processing of polyolefins, especially to improve their processing characteristics. It has been known that PPA can be used in the range of 100 – 1000 ppm to eliminate surface defects including melt fracture and gels, as well as to reduce die build up. The main focus of this paper is to determine the effect of various fluoropolymer processing aids in the elimination of melt fracture of an octene linear low density polyethylene. Also the influences of both antiblocking agent and slip additive on the performance of PPA are assessed.
Effect of Functionalized Polyolefin Coupling Agent Types on the Mechanical Properties of HDPE/Wood-Flour Composites
Qingxiu Li, Laurent M. Matuana, May 2002
The performance of fiber reinforced thermoplastic composites strongly depends on solid fiber-matrix adhesion to allow stress transfer between the phases. Fiber surface modification with coupling agents is generally needed to induce bond formation between the fiber and the polymer. This study investigated the effects of coupling agent's functional monomer (acrylic acid vs. maleic anhydride) and base resin (polyethylene vs. polypropylene) types on the on the tensile and flexural properties of high-density polyethylene (HDPE)/wood-flour composites. The experimental results indicate that the types of functional monomer and base resin are important factors determining the effectiveness of functionalized coupling agents for HDPE/wood-flour composites. Maleic anhydride-functionalized polyolefins perform better than acrylic acid counterparts whereas polyethylene-based maleated coupling agents are more effective than polypropylene-base counterparts in improving the mechanical properties of HDPE/wood-flour composites.
Effect of Gamma-Irradiation on the Mechanical Behavior of PS/PP Blends
C. Albano, J. Reyes, M. Ichazo, J. González, M. Hernández, M. Rodríguez, May 2002
The effect of Gamma-irradiation on the tensile behavior of PS/PP blends (80/20) and its mathematical analysis indicates that the blend presents a high radiation resistance to low doses (80-70 kGy), since mechanical properties present no significant changes; this is due to the presence of the aromatic ring in the PS structure, factor which was confirmed by the lineal mathematical adjustment. On the other hand, at high doses of irradiation (70-1300 kGy), a dramatic change on the mechanical properties was observed and the mathematical adjustment showed a third order polynomial behavior, which indicates a competition between crosslinking and degradation mechanisms, being the latter predominant.
The Effect of High Barrier Emulsion Polymers on the Reduction in Water Vapour Transmission Rates of Laminated Carton
S. Lendrum, N.M. Ryan, G.M. McNally, May 2002
The water vapour transmission rate (WVTR), or moisture vapour transmission rate, of carton boards can often be critical, especially in high performance packaging applications. A range of laminated two-ply carton boards were prepared using litho-lamination techniques. These boards were manufactured using a range of polymer based emulsions and adhesives. Different carton board materials and polymer/adhesive layer thicknesses were used during this investigation.The WVTR of these carton boards were measured using a MOCON Permatran automatic water vapour permeability analyser at 60% relative humidities (RH) and at 20°C temperature. The results show significantly lower WVTR with the EVOH based emulsion than with the other polymer based emulsions and the adhesives.
Effect of High Density Polyethylene Concentration and Melt Temperature on Crystalization Dynamics during Film Blowing of Linear Low Density Polyethylene
G.A. Campbell, O.Y. Alothman, M.D. Bullwinkel, May 2002
The crystallization of low density Polyethylene is investigated relative to the influence of small, up to 4 wt.%, of high density PE at different melt temperatures. The process was evaluated by the use of simultaneous on-line SALS (Small Angle Light Scattering) and IR (Infrared) temperature measurements to study structure development as influenced by nucleation during tubular blown film extrusion of LLDPE. As the concentration of the nucleation aid, HDPE, was increased, the observed scattering intensity was decreased probably due to impingement and truncation of spherulites. The effect of melt temperature was also investigated and the scattering intensity increased as the temperature increased as a result of lower internal disorder.
The Effect of Internal Cooling on Fingering in the Gas-Assisted Injection Molding
Jun Seok Lee, Sooyoung Cha, Francis Lai, May 2002
A new approach of liquid cooling of gas channel in the gas-assisted injection molding process was adapted in the development and investigation of a water injection system. The gas channel was used as an internal cooling by a liquid injection to increase the process efficiency.The major goal for this study is to minimize the fingering region by introducing the water in the conventional gas-assisted injection molding system. The gas penetration length and the gas fingering area were reduced with increase of the amount of water. The decrease of the penetration length is an undesirable effect and reduces the productivity. The gas injection pressure and the amount of water should be balanced to obtain the optimal part quality.
Effect of Mold Size on the Average Density and Density Gradients in a Polyurethane Foam System
Brendan O’Toole, Michael Mullin, Michelle Cameron Nelson, Dacia Jackovich, Robert Mohan, May 2002
Polyurethane foam is often molded directly in place as a thermal or vibration insulator, energy absorbing material, or core material for a sandwich structure. During the foaming process a smooth thin skin forms between the mold and the interior cellular structure of the foam. This thin skin is only part of a density variation within the cellular structure. This paper examines the effects of mold type on the density gradient. A general trend was found within three mold types; samples taken from the center were less dense than those taken near the mold side. From the center outward, all three molds exhibited a density increase in the form of a power curve. Another general trend was discovered within all three mold types; samples taken from the top section were less dense than those taken from the bottom section of the molds. It was also shown that as the mold size decreased, the vertical density gradient decreased.
The Effect of Molecular Structure on the Coalescence of Ethylene/?-Olefin Copolymers
S.A. Guillén-Castellanos, C.T. Bellehumeur, M. Weber, May 2002
An experimental study on the coalescence of polymer particles has been conducted on ethylene/?-olefin copolymers. Experimental evidence suggests that copolymers with a more homogeneous structure generally coalesce faster than their heterogeneous counterparts. In a few cases, however, the presence of some heterogeneities in the molecular structure seemed to be beneficial to the coalescence process. A controlled level of heterogeneities, while not significantly impacting the relative elasticity of the material, affected the thermal properties of the material in a favorable way.
The Effect of Molecular Weight and Polydispersity on the Rheological Properties of Pigmented Polypropylene
A.F. Marks, G.M. McNally, W.R. Murphy, P. Orr, May 2002
The rheological characteristics of a range of pigmented polypropylene (iPP) of different MFI values and molecular weight distributions, were investigated using dual capillary rheometry techniques, over the temperature range 190°C to 230°C and shear rate range of 10s-1 to 800s-1 . The various iPP resins were compounded with pigment masterbatch concentrations ranging from 0.2% to 3.0%, using a 38mm Killion compounding line. The pigment masterbatches investigated were iron oxide, titanium dioxide and phthalocyanine blue. The rheological data, showed that there were considerable increases in apparent viscosity of pigmented iPP even at relatively low pigment loadings. Calculation of the non-Newtonian index (n) from the rehological data, also showed the iPP with the narrower polydisperty were less shear thinning than the wider molecular weight distribution polymer resins, especially at the lower shear rates. Activation energies (Ea) calculated from the rheological data showed large increases in Ea especially for wide molecular weight distribution pigmented iPP resins, and compared favorably with crystallinity developed in the polypropylene during the low shear compounding process.
Effect of Molecular Weight on Mechanical and Morphological Properties of High Density Polyethylene Foams
Yaolin Zhang, Abdellatif Ait-Kadi, Denis Rodrigue, May 2002
Morphological and mechanical properties of linear polyethylene (HDPE) foams were investigated as function of polymer molecular weight and blowing agent concentration. The objective of this systematic study was to understanding the effect of polymer molecular weight via rheology on the final morphology of the foams. Shear and elongational properties of linear polyethylenes with a wide range of molecular weights were first measured using, respectively, a rotational rheometer (Bohlin CVO) and an elongational rheometer (RME). Azodicarbonamide (ACA) was used as the chemical blowing agent and concentrations between 1 and 3 wt% were used to produce HDPE foams. We present here the morphology of the foams and their tensile mechanical properties. The results are discussed in terms of the rheological properties of the polymer matrix which is related to their molecular weight.


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