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Low Density Polyethylene (low + density_polyethylene)
Kinds of Low Density Polyethylene Selected AbstractsEstimation of elongational viscosity of polymers from entrance loss data using individual parameter optimizationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2002Mahesh Gupta The elongational viscosity model proposed by Sarkar and Gupta (Journal of Reinforced Plastics and Composites 2001, 20, 1473), along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the elongational viscosity model. To improve the computational efficiency, various elongational viscosity parameters are optimized individually. Estimated elongational viscosity for a Low Density Polyethylene (Dow 132i) is reported for two different temperatures. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 98,107, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10017 [source] AN EMPIRICAL APPROACH FOR ASSESSMENT OF SAFE STORAGE PERIOD FOR BUTTON MUSHROOM (AGARICUS BISPORUS) BASED UPON COLOR CHANGES UNDER MODIFIED ATMOSPHERE PACKAGINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2010SHASHI PAUL ABSTRACT White button mushroom accounts for 35,45% of the total mushroom produced in the world. Modified atmosphere packaging or MAP is a technology that, along with low temperature storage, helps in extending the shelf life and maintenance of quality of the produce packaged in polymeric films. The present study mathematically modeled the various transport processes associated with the mushroom under MAP at 15C and 75% relative humidity (RH) using the enzyme kinetics approach. Low density polyethylene (LDPE), polypropylene (PP) and oriented polypropylene (OPP) films were used to pack the mushroom. Numerical solutions to the transient state equations were programed in a computer programing language to predict the in-pack gaseous partial pressures at any instant of time. The model was experimentally validated, and a simple qualitative tool based upon optimum whiteness of mushroom was developed using the predictions to determine the safe period of storage. The predicted and experimental in-pack partial pressures of O2 and CO2 were in fair agreement with each other. In the OPP film packages, the O2 and CO2 levels stabilized around 6.87 and 12.93 kPa, respectively. Whereas, O2 levels decreased drastically in LDPE and PP film packages. A combination of predicted in-pack environment in all the film packages, storage time and whiteness of mushroom led to the conclusion that mushrooms can be stored safely for 32, 44 and 108 h in the gaseous environment available in the LDPE, PP and OPP film packages, respectively. PRACTICAL APPLICATIONS The empirical approach followed in this study through assimilation of various transient state in-pack variables with a single qualitative attribute of mushroom can serve as a measure of assessment of the mushroom's safe storage period under modified atmosphere packaging. Further, the mathematical approach suggested in this study can also serve as a benchmark for its application to other fruits and vegetables, taking into consideration their respective limiting qualitative characteristics. Thus, the results detailed in the study can be easily applied for their direct practical application during storage as well as for further academic exercises. [source] Improving the properties of LDPE/glass fiber composites with silanized-LDPEPOLYMER COMPOSITES, Issue 7 2009Felipe W. Fabris Low density polyethylene (LDPE) is a widely used thermoplastic. The dispersion of inorganic fillers in thermoplastic matrices such as polyethylene has been largely employed to improve some of its properties. However, interaction between both components is a major issue so the presence of a coupling agent is usually necessary to increase the interaction among the phases. In this study, LDPE chemically modified with vinyltriethoxysilane (VTES) was used as a coupling agent in glass fiber-reinforced LDPE. The composites were prepared in a mixing chamber and subsequently analyzed by tensile tests, rotational rheometry, and scanning electron microscopy (SEM). The mechanical properties were significantly increased by the use of small amounts of the coupling agent. Moreover, the rheological behavior and the SEM micrographs showed higher interaction between the matrix and the reinforcing phase in the composites containing LDPE modified with VTES, confirming the suitability of using this coupling agent in these systems. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Polyolefins,biofibre composites: A new way for an industrial productionPOLYMER ENGINEERING & SCIENCE, Issue 4 2007J. Soulestin Low density polyethylene (LDPE) composites based on cellulose fibres have been processed by high shear extrusion with water injection to help dispersion of fibres and release nanofibres from cellulose. Influence of extrusion parameters as shear, residence time, storage conditions of the matrix, and effect of water injection on the morphological properties of the composites have been studied using microscopy. Optimization of the extrusion parameters is necessary to reach a dispersion of the fibres. Increasing shearing forces and residence time allows limiting the presence of large aggregates of cellulose fibres. Use of powdered LDPE, even for short residence time and low shear, is efficient to produce well-dispersed composites. Injection of water during the extrusion also improves the quality of the dispersion. However, no nanofibres are observed. The main effect is a spectacular decrease of the discoloration (yellowing) due to cellulose degradation. Mechanical properties of the composites have been investigated. Young modulus increases with cellulose content and reinforcing effect is more important above 10% by weight. For well-dispersed composites, the extrusion parameters have no significant influence on the stiffness of the composites. However, due to the weakness of the interface, the ductility of composites is reduced compared with LDPE. POLYM. ENG. SCI., 47:467,476, 2007. © 2007 Society of Plastics Engineers. [source] Recycling of poly(ethylene terephthalate) as polymer-polymer composites,POLYMER ENGINEERING & SCIENCE, Issue 4 2002M. Evstatiev Microfibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer-polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations. The MFC dogbone samples show impressive mechanical properties,the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short-glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers. [source] Low density polyethylene and grafted lignin polyblends using epoxy-functionalized compatibilizer: mechanical and thermal propertiesPOLYMER INTERNATIONAL, Issue 12 2005RRN Sailaja Abstract Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene- co -(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco-friendly products. Copyright © 2005 Society of Chemical Industry [source] Dynamic mechanical and thermal properties of PE-EPDM based jute fiber compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Gautam Sarkhel Abstract The present investigation deals with the mechanical, thermal and viscoelastic properties of ternary composites based on low density polyethylene (LDPE)-ethylene,propylene,diene terpolymer (EPDM) blend and high density polyethylene (HDPE)-EPDM blend reinforced with short jute fibers. For all the untreated and compatibilizer treated composites, the variation of mechanical and viscoelastic properties as a function of fiber loading (10, 20 and 30 wt %) and compatibilizer concentration (1, 2, and 3%) were evaluated. The flexural strength, flexural modulus, impact strength, and hardness increased with increasing both the fiber loading and the compatibilizer dose. The storage modulus (E,) and loss modulus (E,) of the HDPE-EPDM/jute fiber composites were recorded higher compared to those of the LDPE-EPDM/jute fiber composites at all level of fiber loading and compatibilizer doses. The tan, (damping efficiency) spectra showed a strong influence of the fiber loading and compatibilizer dose on the , relaxation process of polymer matrix in the composite. The thermo-oxidative stability was significantly enhanced for treated composites compared to untreated composites. Scanning electron microscopy investigation confirmed that the higher values of mechanical and viscoelastic properties of the treated composites compared to untreated composites is caused by improvement of fiber-matrix adhesion as result of compatibilizer treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Blends of triazine-based hyperbranched polyether with LDPE and plasticized PVCJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Jyotishmoy Borah Abstract Triazine-based hyperbranched polyether was obtained by earlier reported method and blended with low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC) separately to improve some desirable properties of those linear polymers. The properties like processability, mechanical properties, flammability, etc. of those linear polymers were studied by blending with 1,7.5 phr of hyperbranched polyether. The mechanical properties were also measured after thermal aging and leaching in different chemical media. SEM study indicates that both polymers exhibit homogenous morphology at all dose levels. The mechanical properties like tensile strength, elongation at break, hardness, etc. of LDPE and PVC increase with the increase of dose level of hyperbranched polyether. The flame retardant behavior as measured by limiting oxygen index (LOI) for all blends indicates an enhanced LOI value compared to the polymer without hyperbranched polyether. The processing behavior of both types of blends as measured by solution viscosity and melt flow rate value indicates that hyperbranched polyether acts as a process aid for those base polymers. The effect of leaching and heat aging of these linear polymers on the mechanical properties showed that hyperbranched polyether is a superior antidegradant compared to the commercially used N -isopropyl- N -phenyl p -phenylene diamine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 648,654, 2007 [source] Morphology and electrical properties of carbon black filled LLDPE/EMA compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Ping Zhou Abstract The morphology and electrical properties of linear low density polyethylene (LLDPE)/poly (ethylene-methyl arylate) (EMA) blends filled with carbon black (CB) are investigated in this work. Comparing to LLDPE/CB composite, the higher percolation threshold of EMA/CB composite is attributed to the good interaction between EMA and CB. However, carbon black is found to locate preferentially in the LLDPE phase of LLDPE/EMA immiscible blends from the characterization of SEM and electrical properties, which greatly decreases the percolation threshold of the composites. The viscosity of the two polymers is the key factor to determine the distribution of CB instead of interfacial energy in this system. This suggests a method to control the distribution of CB in the immiscible blends by choosing the viscosity ratio of polymer blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 487,492, 2007 [source] A BATCH CULTURE METHOD FOR MICROALGAE AND CYANOBACTERIA WITH CO2 SUPPLY THROUGH POLYETHYLENE MEMBRANES,JOURNAL OF PHYCOLOGY, Issue 4 2010Yvonne Pörs A new method for CO2 supply to photoautotrophic organisms was developed, and its applicability for measuring specific growth rates in shaken batch cultures of cyanobacteria and unicellular algae was shown. Small bags containing a concentrated carbonate buffer with a CO2 partial pressure of 32 mbar were prepared from a thin foil of low density polyethylene (LDPE). These bags were inserted as CO2 reservoirs (CRs) into polystyrene culture flasks with gas-permeable screw caps, which were suitable to photometric growth measurement. CO2 was released directly into the medium with membrane-controlled kinetics. The CRs were not depleted within 1 week, although the atmosphere in the culture vessel exchanged rapidly with the ambient air. Rates of initial growth and final densities of the cultures of six different unicellular algal species and one cyanobacterium were markedly increased by diffusive CO2 supply from the CR. In the presence of a CR, growth was exponential during the first 2 d in all cultures studied. The method described allowed a high number of measurements of specific growth rates with relatively simple experimental setup. [source] Waste and Virgin LDPE/PET Blends Compatibilized with an Ethylene-Butyl Acrylate-Glycidyl Methacrylate (EBAGMA) Terpolymer, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Mustapha Kaci Abstract Summary: This work is aimed at studying the morphology and the mechanical properties of blends of low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) (10, 20, and 30 wt.-% of PET), obtained as both virgin polymers and urban plastic waste, and the effect of a terpolymer of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) as a compatibilizer. LDPE and PET are blended in a single screw extruder twice; the first extrusion to homogenize the two components, and the second to improve the compatibilization degree when the EBAGMA terpolymer is applied. Scanning electron microscopy (SEM) analysis shows that the fractured surface of both the virgin polymer and the waste binary blends is characterized by a gross phase segregation morphology that leads to the formation of large PET aggregates (10,50 µm). Furthermore, a sharp decrease in the elongation at break and impact strength is observed, which denotes the brittleness of the binary blends. The addition of the EBAGMA terpolymer to the binary LDPE/PET blends reduces the size of the PET inclusions to 1,5 µm with a finer dispersion, as a result of an improvement of the interfacial adhesion strength between LDPE and PET. Consequently, increases of the tensile properties and impact strength are observed. SEM micrographs of the fracture surface of a waste 70/30 LDPE/PET blend (R30) and of its blend with 15 pph of EBAGMA (R30C). Magnification,×,1,000. [source] Technology and Stress Relaxation of Biaxially Oriented Polyolefin Shrink FilmsMACROMOLECULAR SYMPOSIA, Issue 1 2004Arthur Bobovitch Abstract In the present study the influence of the heating rate on the stability of the double bubble technological process was investigated. It was shown that increasing the heating rate decreases the stability of the process and causes the lower elongation of the films produced. The morphological transformations of linear low density polyethylene (LLDPE) film were explained using X-ray and transmission electrom microscopy (TEM) methods. The stress relaxation behavior of co-extruded LLDPE/ethylene-vinyl-acetate (EVA) film was studied using the relaxation time spectrum approach. The influence of vinyl-acetate (VA) content in EVA copolymers on the relaxation time spectrum was observed. [source] Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymerMACROMOLECULAR SYMPOSIA, Issue 1 2003Francesco Paolo La Mantia Abstract Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrillation is increased, especially for the blends with the higher molar mass LDPE grade. The mechanical properties of the latter blends were found to be considerably enhanced by the addition of EAA, whereas the improvement was relatively modest for the blends with the lower molar mass LDPE. The fracture properties of double end notched samples of the ribbons prepared with the blends containing the lower molar mass LDPE grade were also studied. It was shown that, despite of the increased interfacial adhesion caused by the presence of EAA, the latter plays a measurable positive effect on the fracture properties only for the blends with LDPE as the matrix. [source] Development of a liquid extraction method and comparison with dynamic thermal stripping,thermal desorption (DTS,TD) method: sorption of D -limonene by flexible packaging filmsPACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2004Cengiz Caner Abstract The sorption of D -limonene into polymeric structures in contact with food simulant liquids (ethanol and acetic acid solutions) was determined using two methods, liquid extraction (LE) and dynamic thermal stripping,thermal desorption (DTS,TD). The polymeric films studied were PP (polypropylene), PE/nylon/EVOH/PE (polyethylene/nylon/ethylene vinyl alcohol/polyethylene) and metPET/VA EVA/LLDPE (metallized polyethylene terephthalate/ethylenevinyl acetate/linear low density polyethylene). Our assessment showed that both LE and DTS,TD techniques are valuable procedures. LE was evaluated as an alternative method with the advantage of being a simplified process. It was possible to measure the amount of D -limonene in the polymers using both methods. Correlation between methods was >82% and for the single layer polymers >92%. The respective sorption values obtained by the two methods were also found to be in good agreement. LE is simple and rapid to perform and, in general, gives slightly lower results compared to DTS,TS sorption tests conducted with adequate food simulants. The results indicate that the liquid extraction method is an excellent technique for the determination of sorbate concentration in polymeric structures. Copyright © 2004 John Wiley & Sons, Ltd. [source] The impact of silane chemistry conditions on the properties of wood plastic composites with low density polyethylene and high wood contentPOLYMER COMPOSITES, Issue 5 2010Yu Geng Silane chemistry was implemented on various formulations of wood/thermoplastic polymer composites (WPCs) with low density polyethylene (LDPE) and high wood content (60 wt%). Taguchi analysis was used to evaluate the impact of vinyltrimethoxysilane content (VTMS), dicumyl peroxide content (DCP), and processing temperature on the rheological, morphological, and dynamic mechanic properties of WPCs. The torque power was measured by a Haake torque rheometer and indicated that the VTMS content and temperature most significantly impacted the rheological properties related to silane reactions. Differential scanning calorimetry also showed a larger depression in LDPE melting point and crystallinity index when a high VTMS content (35 phr), high DCP content (0.5 phr), and a high compounding temperature (200°C) were used. With dynamic mechanical analysis (DMA), it was shown that the compounded formulations had a higher storage modulus over a wide range of temperature whereas the , transition temperature increased with higher content in silane reactants. Interestingly, the high humidity/temperature conditioning step aimed at crosslinking resulted in a drop of dynamic moduli compared to the freshly compounded formulations. This was explained by the fact that during compounding of LDPE with high wood content and silane reactants, significant amounts of matrix and interfacial silane crosslinking already occurred. Subsequent conditioning in a high humidity and temperature environment was proposed to hydrolyze the interfacial siloxane bonds resulting in a degradation of mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] PANI,LDPE composites: Effect of blending conditionsPOLYMER COMPOSITES, Issue 1 2009M. Cote A composite based on polyaniline (PANI) and low density polyethylene (LDPE) with electrical conductivity was developed. Polyaniline was polymerized by chemical oxidation and doped with dodecyl-benzene-sulfonic acid (DBSA). PANI,LDPE composites were prepared via melt blending and the films were obtained by compression molding. The influence of three variables of the blending (temperature, [PANI], rotor speed) on conductivity, microstructure and mechanical properties of the composites was studied by means of statistical tools and a 23 experimental design. The results show that the PANI concentration is the most influential variable, which mainly affects the conductivity and the elongation at break of the composites. These changes are related to the microstructure of the composites. Statistically, the other variables don't show significant influence on conductivity and mechanical properties in the studied range. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers. [source] Dynamic viscoelasticity of hybrid kevlar and glass fiber reinforced LLDPE in the molten statePOLYMER COMPOSITES, Issue 4 2002S. A. R. Hashmi Kevlar and glass fibers were used to reinforce linear low density polyethylene (LLDPE), and composite sheets of 0.8, 1.5 and 2.5 mm thicknesses were obtained by using a compression molding technique. Dynamic viscoelastic properties of non-hybrid and hybrid composites of various compositions at 200°C are evaluated. Storage modulus (G,) and loss modulus (G,) increase with angular frequency (,) and reinforcement. Replacement of glass fiber by Kevlar at constant loading of fibers in LLDPE increases the value of G,, G, and ,,. The fractured surface of composite shows the gradient orientation of fibers particularly in 2.5 mm thick sheet. Top and bottom layers show relatively two-dimensional orientation as compared to the middle layer, which shows random orientation. The orientation of fibers decreases G, and ,, of Kevlar fiber and hybrid fiber hybrid fiber reinforced LLDPE composites. The effect of change in distance between parallel plate of rheometer (change in strain amplitude) on dynamic rheological properties is studied and reported here. [source] Dynamic mechanical behavior of LCP fiber/glass fiber,reinforced LLDPE compositesPOLYMER COMPOSITES, Issue 2 2001S. A. R. Hashmi Liquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical , and , relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from ,50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE. [source] Electrical conductivity and rheological behavior of multiphase polymer composites containing conducting carbon blackPOLYMER ENGINEERING & SCIENCE, Issue 11 2008Qinghua Zhang Multiphase polymer composites of carbon black (CB), polypropylene (PP) and low density polyethylene (LDPE) were prepared by melt-mixing method to reduce the amount of CB in the conductive composites. SEM images showed that CB preferably located in LDPE phase and formed electrically conductive path. The measurement of conductive properties showed that the ternary materials possessed lower percolation than binary composites of CB/PP or CB/LDPE, the former was ,6 wt% and the latter was 9,10 wt%. Positive temperature coefficient (PTC) effects of the binary and ternary composites were investigated, indicating that the latter exhibited a relatively high PTC intensity. A rheological percolation estimated by a power law function is 2.66 wt% of CB loading, suggesting an onset of solid-like behavior at low frequencies. This difference between the electrical and rheological percolation thresholds may be understood in terms of the smaller CB,CB distance required for electrical conductivity as compared with that required to impede polymer mobility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effect of intercalating agents on clay dispersion and thermal properties in polyethylene/montmorillonite nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2008Karen Stoeffler Alkyl pyridinium, 1-vinyl alkyl imidazolium, 1,3-dialkyl imidazolium, and tetraalkyl phosphonium bromides were successfully used as intercalants for the preparation of highly thermally stable organophilic montmorillonites. Nanocomposites of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE/LLDPE- g -MAH) were prepared from those organoclays. The micro- and nano-dispersions were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM): intercalation and/or partial exfoliation were found to occur only for formulations based on organoclays having an initial basal distance higher than 20 Å, suggesting the existence of a critical interfoliar distance for the delamination of silicate layers in a noninteracting polymer matrix. The properties of the nanocomposites were analyzed through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and oscillatory rheometry. The dynamic crystallization of LLDPE was not significantly affected by the presence of clay. TGA in oxidative atmosphere proved to be very sensitive to the dispersion state of the organoclay: the thermal stability was drastically enhanced for intercalated and partially exfoliated formulations. However, the inherent thermal stability of the organoclay did not appear to influence significantly the overall thermal stability of the composite in the range of temperatures investigated (160,230°C). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source] The effect of recycling on LDPE foamability: Elongational rheologyPOLYMER ENGINEERING & SCIENCE, Issue 1 2008Eddy Twite Kabamba The purpose of this work was to investigate changes in the elongational rheology of low density polyethylene (LDPE) when recycled. Both foamed and unfoamed LDPE were submitted up to 10 generations in a closed loop using constant extrusion conditions and azodicarbonamide as a chemical blowing agent. For both foamed and unfoamed polymers, decreasing elongational properties in terms of strain hardening was observed, indicating progressive loss of foamability with the number of time the polymer is recycled. It was also found that the elongational properties of the foamed polymer decreased more rapidly than its unfoamed counterpart. It is believed that higher mechanical degradation of polymer may be the result of higher deformation rates (biaxial) associated with foaming and the accumulation of blowing agent residues limiting polymer chain mobility and entanglement. POLYM. ENG. SCI., 48:11,18, 2008. © 2007 Society of Plastics Engineers [source] Mechanical and oxygen barrier properties of organoclay-polyethylene nanocomposite filmsPOLYMER ENGINEERING & SCIENCE, Issue 7 2007Yang Zhong An organically modified montmorillonite was compounded with ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) in a twin-screw extruder. The resulting organoclay-polyethylene nanocomposites were then blown into films. Tensile properties and oxygen permeability of these nanocomposite films were investigated to understand the effects of organoclay on different types of polyethylene. It was found that the clay enhancing effects are function of the matrix. The mechanical and oxygen barrier properties of clay/EVA systems increased with clay loading. Both the tensile modulus and oxygen barrier of EVA doubled at 5 wt% clay. Maleic anhydride grafted polyethylene (MAPE) usually is used as a compatibilizer for LDPE and HDPE-based nanocomposites. However, the MAPEs were found to weaken the oxygen barrier of the PEs, especially for HDPE. This is believed to be a result of less compactness caused by the large side groups and the increase in polarity of the MAPEs. Incorporating 5 wt% clay improves the oxygen barrier by 30% and the tensile modulus by 37% for the LDPE/MAPE system. Incorporation of clay does not enhance the properties of the HDPE-based systems, likely due to large domain structure and poor bonding. Halpin,Tsai equation and the tortuous path equation were used to model the tensile modulus and oxygen permeability of the clay/EVA nanocomposite films. POLYM. ENG. SCI., 47:1101,1107, 2007. © 2007 Society of Plastics Engineers [source] Low density polyethylene and grafted lignin polyblends using epoxy-functionalized compatibilizer: mechanical and thermal propertiesPOLYMER INTERNATIONAL, Issue 12 2005RRN Sailaja Abstract Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene- co -(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco-friendly products. Copyright © 2005 Society of Chemical Industry [source] Ultrasonic improvement of rheological and processing behaviour of LLDPE during extrusionPOLYMER INTERNATIONAL, Issue 1 2003Shaoyun Guo Abstract The effects of ultrasonic oscillations on die pressure, productivity of extrusion, melt viscosity and melt fracture of linear low density polyethylene (LLDPE) as well as their mechanism of action were studied in a special ultrasonic oscillation extrusion system developed in our Laboratory. The experimental results showed that, in the presence of ultrasonic oscillations, the melt fracture or surface distortion of LLDPE extrudate is inhibited or disappears. The surface appearance of the LLDPE extrudate was greatly improved. The productivity of LLDPE extrudate was increased in the presence of ultrasonic oscillations. The die pressure, melt viscosity and flow activation energy of LLDPE decreased with the rise in ultrasonic intensity. The shear sensitivity of LLDPE melt viscosity decreased due to the increase of its power law index in the presence of ultrasonic oscillations. Inducing ultrasonic oscillations into LLDPE melt greatly improved its processability. A possible mechanism for the improved processibility is proposed. © 2003 Society of Chemical Industry [source] Mechanical properties and thermal analysis of low-density polyethylene,+,polypropylene blends with dialkyl peroxidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2010Kamil, irin Abstract Polypropylene,+,low density polyethylene (PP,+,LDPE) blends involving 0, 25, 50, 75 and 100,wt% of PP with dialkyl peroxide (DAP) were prepared by melt blending in a single-screw extruder. The effects of adding dialkyl peroxide on mechanical and thermal properties of PP,+,LDPE blends have been studied. It was found that at lower concentrations of peroxide (e.g., 0,0.08,wt% of dialkyl peroxide) LDPE component is cross-linked and Polypropylene (PP) is degraded in all compositions of PP,+,LDPE blends. Mechanical properties (Tensile strength at break, at yield and elongation at break), Melt flow index (MFI), hardness, Scanning Electron Microscope (SEM) and thermal analyses (DSC) of these blends were examined. Because of serious degradation or cross-linking the mechanical properties and the crystallinty (%) of those products were decreased as a result of increasing peroxide content. Copyright © 2009 John Wiley & Sons, Ltd. [source] The Characteristics of Polyethylene Film for Stretch and Cling Film ApplicationsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004C.M. Small Part I. A range of polyethylene films were prepared from metallocene linear low density polyethylene (m-LLDPE), linear low density polyethylene (LLDPE) and ultra low density polyethylene (ULDPE) resins, containing 0 and 8% polyisobutylene (PIB). FTIR, DSC and mechanical analysis techniques were used to investigate the effect of co-monomer type, density and melt flow index (MFI) on the mechanical performance, orientation and crystallinity of these films. The study established that co-monomer type and MFI were the greatest factors influencing mechanical performance and crystallinity. Crystallinity was found to be the most influential factor governing PIB migration in these films and this in turn was related to polymer type, density and MFI, High MFI, octene co-monomer films exhibited the highest orientation, tear resistance and tack strength and would therefore be suitable for stretch film applications. Ultra low-density polymers gave relatively low tack strength and poor overall mechanical performance. Part II. A range of ethyl vinyl acetate (EVA)/m-LLDPE/EVA co-extruded films was manufactured, with vinyl acetate (VA) co-monomer content of 6, 12 and 18% and PIB content from 0,20%. The films were aged at 45d,C for up to 28 days, to enable tack (cling) development. The results show that film tack strength improved significantly with ageing. Increased VA concentration in the surface layer also showed significant improvement in film tack strength. The film tensile strength, elongation and tear properties in both machine direction (MD) and transverse direction (TD) were not significantly affected by increase in PIB concentration. However, increased VA content showed slight improvement in MD mechanical performance of the films, TD properties were relatively unaffected. Films with 12 to 18% VA in the surface layers produced high surface tack film and the mechanical performance of these films were comparable to mono-layer polyethylenes. These films are suitable for stretch wrap applications and have reduced the overall concentrations of tack additives, though high VA films were more difficult to process. [source] The Effect of Orientation on Extrusion Cast Metallocene Polyethylenes and the Role of Processing Conditions in the Die Swell of Metallocene and Conventional PolyethylenesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004B.G. Millar Cast films were prepared from a range of metallocene polyethylenes (mPEs) of varied co-monomer types (hexene, octene) using a Killion single-screw extruder, using different haul off speeds (8,4 m/min) and die gaps (700,250 m,m). Samples with greater orientation in one direction had increased tensile strength and shrinkage in that direction. DSC analysis showed crystallinity to decrease with decreasing haul of speed. Extrusion of mPEs and conventional linear low density polyethylenes (LLDPEs) by single capillary rheology showed that die swell increased with increasing extrusion rate and decreasing melt temperature. Increased die swell was found for the broader molecular weight distribution (M.W.D.) LLDPEs and in the higher molecular weight resins. Furthermore, long chain branching was found to increase die swell. [source] | ||||||||||||||||