Linear Low Density Polyethylene Samples Research Articles

Analyzing Impact Strength Improvement in Polymer Laminates: A Comparative Study of Machine Direction Oriented (MDO)-PE/LLDPE and Polyamide (PA)/LLDPE Structures

The mechanical strength of 2 film structures, machine-direction-oriented polyethylene (MDO-PE) laminated with linear low-density polyethylene (LLDPE) and polyamide (PA) laminated with LLDPE was evaluated. PA/LLDPE films demonstrated superior impact strength (0.834 J/mm²) compared to MDO-PE/LLDPE films (0.445 J/mm²). Tensile strength for modified LLDPE (C₆) was 40 N/mm², higher than standard LLDPE (C₈) at 33 N/mm². The elongation at break for LLDPE reference C₈ was 689 %, compared to 682 % for LLDPE sample C₆. Film stiffness was measured at 162 MPa for the LLDPE reference C₈ and 122 MPa for the LLDPE sample C₆. PA films exhibited increased mechanical strength due to their intrinsic polyamide structure, while MDO-PE films benefited from molecular orientation during production. The modified LLDPE or C₆ displayed improved impact resistance and tensile strength with reduced stiffness. MDO-PE/LLDPE films are promising for sustainable and robust food packaging. HIGHLIGHTS Comparative Mechanical Strength of Films: Polyamide (PA) films, owing to their chemical structure rich in amide groups, exhibit superior mechanical strength compared to machine direction-oriented polyethylene (MDO-PE) films. Peeling Strength Dynamics: PA/LLDPE laminates display greater initial peeling strength; however, MDO-PE/LLDPE laminates show a gradual increase in peeling strength, indicating potential for improved long-term adhesion. Impact of LLDPE Density on Mechanical Properties: A comparison between LLDPE C₈ and LLDPE C₆ highlights the influence of polymer density on mechanical characteristics, with LLDPE C₆ demonstrating enhanced impact and tensile strengths at the expense of modulus and elongation. Strength Variability Among Laminates: The mechanical properties of laminated films are significantly influenced by the nature of their constituent layers, revealing the complexity of integrating polymers with differing characteristics. Potential of MDO-PE/LLDPE Laminates: Despite the superior properties of PA/LLDPE laminates, MDO-PE/LLDPE emerges as a viable alternative for sustainable and cost-effective packaging solutions, necessitating further validation to fully harness its advantages. GRAPHICAL ABSTRACT

Investigating the influence of peak internal air temperature (PIAT) on material characteristics of linear low-density polyethylene (LLDPE) during rotational moulding

In present study, six samples of ICORENE 1613 LLDPE fuel tank with homogeneous composition were analysed for six different PIAT values of 165 °C, 170 °C, 180 °C, 190 °C, 195 °C and 200 °C in the first stage. In the second phase of the study, the samples with optimum PIAT values were considered for the Tensile and Flexural strength study at different temperatures. Peak Internal Air Temperature (PIAT) values were obtained using the rotolog instrument, while the tensile and flexural tests were performed utilizing the Universal Testing Machine for accurate characterization of the material properties. The tensile and flexural strength were carried out at three different operating temperatures considering the tank will be subjected to variable operating conditions in real world exercise. The maximum value for both all the process parameters studied were observed at PIAT value of 195 °C, the same has been chosen for the further investigation. The failure data obtained from these two destructive testing will be helpful to mitigate the defects during the process. The tensile test results indicate that the LLDPE sample exhibits the maximum tensile strength of 17.3 MPa at 23 °C and the highest elongation percentage at failure, which is 182.7% at 80 °C. Moreover, the sample shows a remarkable flexural strength of 75.97 MPa at 23 °C, which is indicative of its superior ability to resist deformation under applied bending stresses.

Effect of the Processing Conditions on the Supercritical Extraction and Impregnation of Rosemary Essential Oil in Linear Low-Density Polyethylene Films

The supercritical fluid extraction of essential oil from rosemary leaves and its subsequent impregnation in linear low-density polyethylene (LLDPE) films were studied. The effects of temperature (318 and 338 K), pressure (15 and 25 MPa) and rosemary particle size (0.9 and 0.15 mm) on the extraction yield were investigated. Impregnation assays were developed at two different values of pressure (12 and 20 MPa), temperature (308 and 328 K), and impregnation time (1 and 5 h). The extraction yield of rosemary essential oil was increased by increasing pressure and decreasing particle size and temperature. ANOVA results showed that temperature, pressure, and time significantly impacted the essential oil impregnation yield in LLDPE films. The maximum impregnation yield (1.87 wt. %) was obtained at 12 MPa, 328 K, and 5 h. The antioxidant activity and the physical-mechanical properties of impregnated films were analyzed. The IC50 values for all the impregnated LLDPE samples were close to the IC50 value of the extract showing that the impregnated films have a significant antioxidant activity.

Fabrication and Radiation Attenuation of Linear Low Density Polyethylene with Iron Slag in the Range of Peak Potentials 50 kVp to 150 kVp

The emergence of polymer composite materials has potential advantages for shielding application form low energy radiation. Four different samples of different ratio of iron slag (0%, 1%, 5%, and 10%) based on a linear low-density polyethylene (LLDPE) polymer mixed were prepared and examined in this study. The measured densities of fabricated LLDPE samples were in the range of 0.925 to 1.004 g cm−3. The distribution of ironpreserving particles in an LLDPE polymer sample was also demonstrated in this study by scanning electron microscopy (SEM). The linear and mass attenuation coefficients of the four samples were determined by using eight standard radiation qualities of different applied voltages (kVp) of 50, 60, 70, 84, 90, 105, 119, and 150 kVp. Moreover, the exposure radiation quality used with different energies was calculated through the half value layer (HVL). It was found that the dose value for different combinations of beam quality including the HVL and kVp did not exceed the recommended values given by the IEC 61267 standard with the effective energies of 28.7, 30.0, 33.0, 36.2, 37.7, 39.6, 44.3, and 50.0 keV. The results of the linear attenuation coefficients of four LLDPE samples were between 0.1886 cm−1 and 0.8412 cm−1. The composite that includes 10% iron slag has the highest attenuation across all incident beam energies. In addition, it exhibited the greatest mass attenuation coefficient among the selected samples. Furthermore, when the mean free path (MFP) was measured, the LLDPE + 10% iron slag composite has a lower MFP value which indicates it is best material for shielding photons in the selected energy range in our investigation.

Nitrogen Poisoning of HDPE and LLDPE based on Chemically Recycled Post‐Consumer Plastic via a Kinetic and Microstructural Modeling Technique

AbstractChemical recycling of plastic waste has promise as a complementary technology to increase eco‐efficiency of plastics life cycles. Accumulation of impurities in feed streams can affect sensitive compounds such as the Ziegler–Natta catalyst systems commonly used to produce polyolefins such as high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). In a poison study, the influence of impurities—more specifically NO and N2O—on the catalyst system are investigated comprehensively in terms of kinetic behavior and activity rates. A product composition analysis gives insights into product properties such as molecular weight distribution (MWD), comonomer composition distribution (CCD), melting point, and crystallinity. By applying known modeling techniques (kinetic modeling, MWD, and CCD deconvolution modeling), information beyond analytical data is obtained. The results of the study show that both poisons significantly affect catalyst kinetics and reduce catalyst activity. N2O influences primarily the MWD, while NO poisoning strongly affects the CCD of LLDPE samples. Since the mechanical properties of the polymers produced depend on factors such as MWD and CCD, NO and N2O poisoning may reduce their processability and applicability.

Circular Economy Assessment in Recycling of LLDPE Bags According to European Resolution, Thermal and Structural Characterization.

According to the Circular Economy Package promoted by the European directive, plastic bags companies must use in their formulations a percentage of polyethylene waste (industrial and/or domestic) greater than 70%. Following that regulation requires an understanding of its consequences in the final product from an industrial point of view. This manuscript analyzes the thermal and morphological changes related to the tear resistance of linear-low density polyethylene (LLDPE) samples from industrial waste generated by the company Sphere Spain subjected to the degradation produced by the recycling cycles. The process is analogue to the industrial, starts from samples in pellets then a film by blow extrusion is obtained (odd steps) and posteriorly this film is recycled to pellets again (even steps). The results obtained show that the LLDPE samples develop two crystalline structures (CS1 and CS2) which evolve differently through the recycling cycles with a tendency to decrease in crystallinity due to degradation that is not the same for the process of obtaining film or recycling to pellet. The molecules with a more linear structure and a longer chain break and branch. The more branched structure increases and tends to crosslinking. This leads to a decrease in tear strength in the longitudinal direction, which is not so evident in the transversal direction. The samples could admit four recycling cycles with and acceptable tear resistance. The longitudinal tear strength value decreases by 40% for each film and 20% in the case of tearing in the transverse direction. The results obtained in this research work show that the regulations included in the cited circular economy package can be applied in the manufacture of consumer bags, helping also to reduce the dependence of manufacturers on fluctuations in delivery by collapses in shipping.

Effect of silane concentration on the properties of crosslinked linear low density polyethylene‐montmorillonite nanocomposite

AbstractIn this study, linear low density polyethylene (LLDPE) was grafted and crosslinked by reactive extrusion melt compounding using different silane concentration with and without the presence of montmorillonite (MMT) nanoclay. The effects of different silane concentration and the addition of nanoclay filler on the degree of crosslinking, mechanical, thermal, rheological, and morphological properties were investigated and reported. Gel content results for all crosslinked samples were found to increase with increasing silane concentration. Tensile strength and Young's modulus of crosslinked LLDPE samples increased with increasing silane concentration compared to neat LLDPE; while the crosslinked LLDPE samples containing nanoclay have achieved higher tensile strength and Young's modulus, indicating strong interfacial interaction between silane grafted LLDPE matrix and nanoclay. However, the decrease of elongation at break for all crosslinked samples were observed compared to neat LLDPE. A reduction in the degree of crystallinity for crosslinked samples, particularly crosslinked samples containing nanoclay, was shown by thermal analysis results; whereas the melting temperature did not change significantly with increased silane concentration and subsequent addition of nanoclay. Thermogravimetric analysis results have revealed significant thermal stability improvement for neat LLDPE with increased silane concentration. Furthermore, crosslinked samples containing nanoclay have achieved better thermal stability compared to crosslinked samples without nanoclay. At lower frequency, it was found that viscosity, and storage modulus of neat LLDPE increased with increased silane concentration due to crosslinking and further addition of nanoclay into crosslinked LLDPE. The transmission electron microscopy results confirmed the intercalated structure of the nanocomposite for the crosslinked samples containing nanoclay.

Thermal pyrolysis of LDPE and LLDPE films in post-consumer packaging

Thermoplastics are increasingly present in the daily life of society in the most varied applications. Among the thermoplastics, polyethylene is the one that presents the higher volume of worldwide production and consumption. However, a large part of its applications are for products with a short shelf life, especially the food packaging sector. This way, they become expressive constituents in the composition of urban solid waste, leading to large quantities often being deposited in landfills. Pyrolysis appears as a technology for recycling plastic waste, allowing the recovery of the monomers that originated it. Through this thermochemical process, the waste is converted into three different products: oil or, in some cases wax, non-condensable gases, and a solid fraction named char. Thus, the goal of this study is to contribute for the development of pyrolysis as a technology for the final treatment of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) waste from post-consumer packaging, through the analysis of the influence of the pyrolysis temperature in the chemical composition of the oil produced, as well as the discussion of possible applications. For this purpose, the waste was initially characterized through analyses of attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC), and X-ray fluorescence (XRF). The characterization experiments showed that the plastic waste is constituted of 4.07% ash, 0.52% fixed carbon, and 95.54% volatile matter, showing its great potential to produce pyrolytic oil. Thermal degradation of the waste initiated at around 410°C and continued through about 530°C, with maximum rate of thermal degradation at about 488°C. The pyrolysis process was carried out with 50g samples of post-consumer LDPE and LLDPE, previously agglutinated, with particle size ranging from 0.001mm to 4mm, in a horizontal quartz reactor, with an inert atmosphere of N2, heating rate of 10°C/min, and residence time of 30 minutes. The experiments were conducted with experimental temperatures of 500°C and 700°C, in order to verify the influence of the temperature in the chemical composition of the oil obtained in the process. The analysis of the oil collected at 500°C by infrared spectroscopy revealed a specter similar to the one of commercial diesel. Through gas chromatography coupled with mass spectrometry, it was verified a composition constituted mostly by olefins (44%), from 8 to 35 carbon atoms, followed by paraffins (23.8%), and cycloparaffins (10%). There was also a considerable percentage of alpha-olefins, important for the petrochemical industry, and a percentage of aromatic compounds on a trace level. By varying the temperature to 700°C, an increase in the level of aromatic compounds to 16.6% occurred, accompanied by a decrease in the percentage of olefins, paraffins, and cycloparaffins. The oils obtained in both temperatures have potential for application in steam cracking or conventional catalytic cracking processes to obtain the raw materials of the petrochemical industry.

Structure Evolution of Polyethylene in Sequential Biaxial Stretching along the First Tensile Direction

Two linear low-density polyethylene samples (PE-A and PE-B), with similar melt index and molecular weight but different molecular structures, were used to explore the structural evolution during sequential biaxial stretching. Only PE-A could be successfully stretched into a film with the biaxial draw ratio of 6 × 6. The interlamellae crossing adjacent lamellar stacks were observed in PE-A but not in PE-B, which could increase the lateral tie connection. Moreover, the amount of fibril was less in PE-A than that in PE-B and the fibrillar structure lacked tie chains between each other. In addition, the newly formed lamellae in PE-A (derived from fine lamellae) could lock the molecular chains of different crystals, which increased the lateral connection via anchoring the tie chains from adjacent lamellae. Therefore, the above specific structures increased the lateral connection and were beneficial for biaxial stretching. Furthermore, the relationship between molecular structure and condensed structure was als...

Thermo-oxidative degradation study of melt-processed polyethylene and its blend with polyamide using time-resolved rheometry

Time-resolved mechanical spectroscopy (TRMS) was conducted to study the thermo-oxidative degradation of linear low density polyethylene (LLDPE) samples with different thermal histories and their blends with a polyamide (PA6) in the melt state. Neat LLDPE was first melt-processed at 180, 220, 250, and 260 °C in an extruder and then pre-processed LLDPE samples were further extruded with PA6 at 260 °C to form various LLDPE/PA6 blends. TRMS measurements were conducted under an air atmosphere at 0.5% strain and a constant frequency of 0.1 rad/s for LLDPE samples and at a range of frequencies between 0.1 and 60 rad/s for LLDPE/PA blend samples, over a 1 h period. In the case of LLDPE samples, time-sweep experiments were carried out at 190, 220, and 240 °C, whereas the temperature was fixed at 240 °C for the LLDPE/PA blend samples. The observed rheological behaviors revealed that the degradation resulted in an increase in the elastic moduli of the LLDPE and LLDPE/PA blends regardless of the thermal history. LLDPE processed at different processing temperatures produced different viscoelastic behaviors in cases where the LLDPE samples were processed at lower temperatures (180 and 220 °C) where a rapid increase in the modulus over a short period was seen. On the other hand, a change in the pre-processing temperature of the LLDPE had no effect on the rheological property of the corresponding LLDPE/PA6 blends. Cross-linking reactions during measurements under an air atmosphere could be the main reason for the growth in the modulus as a result of thermo-oxidative degradation. It was found that degradation was only a function of the temperature and exposure time, not the frequency. The most important result of this study was that collecting data on the isochronal moduli at different scanning frequencies was a more accurate way to understand the degree of cross-linking compared to running conventional frequency sweep tests, where the molecular structure of the material was unstable as a result of rapid degradation.

Degradation in soil behavior of artificially aged polyethylene films with pro‐oxidants

ABSTRACTBio‐based, biodegradable in soil, as well as degradable polyethylene mulching films with pro‐oxidants, have been introduced in the market in an effort to deal with the serious problem of managing plastic waste streams generated from conventional mulching films. In a previous experimental investigation, a series of naturally degraded under water melon cultivation conditions linear low density polyethylene (LLDPE) mulching films with pro‐oxidants, buried in the field for 8.5 years, were recovered intact even though undergoing a continuous slow abiotic degradation in soil. The aim of the present article was to simulate the behavior of the LLDPE mulching films with pro‐oxidants under a much longer time‐scale (e.g. some decades). Toward this purpose, samples of LLDPE with pro‐oxidants film were artificially degraded to simulate severe degradation/fragmentation of these films while been buried in the soil for many years, following the end of the cultivation season. Further degradation of these severely degraded samples was investigated by burying them in the soil over a period of seven years. During this burial period, all degradation parameters and their evolution with time were measured. The artificially degraded LLDPE film samples with pro‐oxidants, in contrast to the naturally degraded film that remained intact for 8.5 years, were gradually transformed into tiny micro‐fragments in the soil. These fragments, through a continuing abiotic degradation process under natural soil conditions are eventually transformed into invisible micro‐fragments. The fate of these micro‐fragments and their long‐term impact to the environment and human health is unpredictable. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42289.

Preparation, Characterization and Properties of Reactive Type Dripping Agent Tween 60-IAH and Their Grafting Copolymer With Linear Low Density Polyethylene

A kind of reactive type dripping agent (Tween 60-IAH) was synthesized with polyethylene glycol sorbitan monostearate (Tween 60) and itaconic anhydride (IAH) as main starting materials. The chemical structure of Tween 60-IAH was characterized by means of Fourier transform infrared (FT-IR) spectroscopy. The effect of reaction time on conversion of Tween 60-IAH was studied. The results of thermogravimetric analysis (TGA) measurement demonstrated that Tween 60-IAH exhibited a better thermal stability than Tween 60. Grafting copolymer of linear low density polyethylene (LLDPE) with Tween 60-IAH was prepared in twin-screw extruder. Thermal and rheological properties of grafted LLDPE samples were investigated with differential scanning calorimetry (DSC) and rotational rheometer. Crystallization temperatures of grafted LLDPE were higher than that of LLDPE. Complex viscosities of grafted LLDPE at high shear rates were lower than that of LLDPE. The dripping properties of film samples were investigated at 60°C.

On properties of graft copolymers of LLDPE and novel fluorine surfactants obtained via reactive extrusion

A series of nonionic fluorin surfactants containing poly(ethylene glycol) (PEG) and their acrylates were synthesized using PEGs of different molecular weight (Mw 600, 1000, 1500, 2000, 4600 g/mol), TDI, acryloyl chloride, and pentadecafluorooctanoic chloride as the main starting materials. Their chemical structures were characterized by means of FTIR and 1H NMR. The surface tension (γ) of the fluorine surfactants were evaluated by drop weight method. The γ value was found to increase with the length of PEG chains. The acrylates were adopted as functionalizing monomers and grafted onto linear low-density polyethylene (LLDPE) through a melt reactive extrusion procedure. The graft degrees of LLDPE were determined by FTIR. Five graft LLDPE samples with grafting degrees of 0.79% (A-I), 0.72% (A-II), 0.68% (A-III), 0.63% (A-IV), and 0.57% (A-V) were prepared. Their surface properties were characterized by measuring contact angles with water and by X-ray Photoelectron Spectroscopy (XPS). Thermal properties of graft LLDPE samples were studied using differential scanning calorimetry. Crystallization rates of graft LLDPEs were faster than that of plain LLDPE at a given crystallization temperature because graft chains could act as nucleating agents. The isothermal crystallization behavior of grafted LLDPE was in accordance with the Avrami model only in the first stage of the process, and deviated from the model by increasing the crystallization time.

Properties of co-extruded nanoclay-filled aliphatic nylon (PA6)/linear low-density polyethylene and aromatic nylon (MXD6)/ linear low-density polyethylene multilayer films

In this study, coextruded multilayer films with aliphatic (polyamide 6) and aromatic (poly (m-xylene adipamide)) nylons as well as their in-situ polymerized nanocomposites with 4 wt% nanoclay, as an oxygen barrier layer (core), and a linear low-density polyethylene, as a moisture barrier layer (skin), were produced and characterized. Five-layer films were prepared by cast coextrusion and rapidly cooled using an air knife. Dynamic rheological measurements showed that the selected materials can be coextruded with a minimum interfacial instability between the melt flows in the feed block. Type of crystals, crystallinity and thermal transitions of layers were investigated using differential scanning calorimetry and modulated differential scanning calorimetry. The mechanical, optical, oxygen and water vapor barrier properties of the coextruded multilayer films were measured and discussed. Although the crystallinity of the poly (m-xylene adipamide) layer in the multilayer films was lower compared to the polyamide 6 layer, the impermeability to oxygen and water vapor was much better for the former multilayer films. In addition, substituting the neat polyamide 6 and poly (m-xylene adipamide) by their nanocomposites improved the oxygen barrier of the multilayer films by more than 50%. The series resistance model was not able to predict the barrier properties of the multilayer films due to the difference in polymer behavior for the single layer and multilayer, and boundary adjacent layer effects. The coextruded polyamide linear low-density polyethylene multilayer films showed higher toughness, tear and flex crack resistance compared to the poly (m-xylene adipamide)/linear low-density polyethylene samples. The pristine poly (m-xylene adipamide)-based multilayer film showed a lower haze compared to the polyamide 6 films due to very little crystallinity in the former.

Assessment of the Whole Environmental Degradation of Oxo-Biodegradable Linear Low Density Polyethylene (LLDPE) Films Designed for Mulching Applications

The current paper is aimed at understanding the environmental fate of linear low density polyethylenes (LLDPE) films designed for mulching purposes and loaded with different pro-degradant additives. These were analyzed, upon exposure to natural sunlight for a period intended to mimick a general crop season in the mediterranean region. The selected samples underwent a relatively low extent of degradation as monitored by carbonyl index, molecular weight variation, extractability by solvent, changes in the onset of the decomposition temperature and crystallinity. The tendency to biodegradation of outdoor exposed LLDPE was then assessed under different environmental compartments including soil medium, aqueous medium as well as in axenic culture of white-rot fungus Phanerochaete chrysosporium. That fungus is known to be effective in the degradation of recalcitrant organic materials and plastic items. During the soil burial biodegradation test, lasted for 27 months, samples specimen were withdrawn at time intervals and characterized by means of structural and thermal analysis. These analytical assessments allowed to monitor any progress of oxidative degradation as a direct effect of the incubation in an active microbial environment. Analogous characterizations were carried out at the end of the biodegradation tests in aqueous medium and in P. chrysosporium axenic cultures. Data presented here are in keeping with the initial abiotic oxidation via a free radical chain reaction promoted by a pro-degradant additive acting on hydroperoxides and peroxide moieties present initially in the polymer bulk. This step was followed by a free radical cascade reactions leading to degradation once the oxidation started under relatively mild conditions (sunlight exposure). During the incubation step in soil, the abiotically degraded samples underwent significant variation in the level of oxidation and degradation with respect to the detected starting values. Indications were gained on the synergistic effect of a random fashion microbial metabolization coupled to biotically mediated oxidation of the original abiotically fragmented samples. Similar results were obtained in the biodegradation tests carried out in the aqueous media and in presence of P. chrysosporium axenic cultures. These evidences are suggesting the role of natural occurring microorganisms in promoting both partial oxiditation and degradation of LLDPE samples in combination with contextual mineralization process of the oxidized fragments.

Effect of short‐chain branching on melt fracture behavior of metallocene and conventional poly(ethylene/α‐olefin) copolymers

AbstractA phenomenon that can represent a great problem in melt processing is extrudate distortion. This effect can range in intensity from a loss of gloss to gross distortion and is the factor that limits the production rate in certain processes such as the blown film extrusion of linear low‐density polyethylene (LLDPE). The aim of this work was to investigate the effects that molecular weight distribution and short‐chain branch length have on the observed melt fracture phenomena for poly(ethylene/α‐olefin) resins with similar weight comonomer content and molecular weight. The flow stability analysis conducted in this study has shown that, even increasing of few carbon atoms the short‐chain branch length of the resins, the surface melt fracture phenomena are reduced and/or eliminated. Moreover, the comparison between the metallocene (mLLDPE) and conventional LLDPE samples, with the same comonomer (hexene), showed that the metallocene‐catalyzed resin exhibits early onset and more severe melt fracture, due to its narrower molecular weight distribution. POLYM. ENG. SCI., 52:1968–1977, 2012. © 2012 Society of Plastics Engineers

Structure development and melt viscoelastic properties of PE/organoclay nanocomposite blown films

AbstractThe effects of compatibilizer and the type of polyethylene (PE) matrix on structure development of PE/organoclay nanocomposite samples were investigated by means of X‐ray diffraction technique and transmission electron microscopy in conjunction with melt viscoelastic measurements. It was shown that the presence of compatibilizer plays a key role in determining the extent of intercalation and resulting structure development in both linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE). The LLDPE/organoclay nanocomposite samples exhibited a pronounced low‐frequency nonterminal storage modulus whose values were found to be greater than those of LDPE/organoclay nanocomposite samples. The percentage increase in storage modulus values for the compatibilized LLDPE/organoclay nanocomposite sample compared to the virgin LLDPE sample was 1080, while the percentage increase in storage modulus values for the compatibilized LDPE/organoclay nanocomposite sample compared to the virgin LDPE sample was 200, at frequency 0.1 s−1. The melt viscoelastic measurements performed on the nanocomposite blown film samples indicated that at higher draw‐down ratio the organoclay platelets and/or tactoids were aligned in the flow direction. Comparing the melt viscoelastic results obtained for annealed and unannealed nanocomposite blown film samples, it was demonstrated that the reorientation of the induced organoclay alignment, which led to network structure formation in the amorphous phase of PE, is very slow, and the time required to complete the reorientation was found to be longer than 3 h at annealing temperature (100°C). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effects of organic peroxide and polymer chain structure on mechanical and dynamic mechanical properties of sisal fiber reinforced polyethylene composites

AbstractThree types of polyethylene (PE), low‐density PE (LDPE), linear low‐density PE (LLDPE), and high‐density PE (HDPE) were used as polymer matrices to prepare untreated as well as dicumyl peroxide (DCP) treated sisal fiber composites. The effect of polymer chain structure, addition of DCP, and sisal fiber loadings on the mechanical and dynamic mechanical properties of the composite was investigated in this study. It was found that the extent of improvement in tensile properties of the composite samples varied with respect to the polymer molecular characteristics. The elongation at break for all the composites decreased significantly. Young's modulus and the tensile strength of the treated LDPE and LLDPE composites increased significantly compared with the untreated composites, whereas Young's modulus of the treated HDPE samples decreased observably compared with the untreated samples. DCP treatment, however, did not change the tensile strength of HDPE and its composites. The storage modulus results for all the PE composites correlate well with the tensile testing results. In the case of the LDPE and LLDPE samples, the curves of the mechanical loss factor (tan δ) show a clear relaxation around −18°C, which shifted to higher temperature in the treated composites, whereas for HDPE this transition was not seen. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Ultra small angle X-ray scattering studies on density heterogeneity of linear low density polyethylene

We have investigated density heterogeneity of linear low density polyethylene (LLDPE) in the order of submicron scale with 2 dimensional ultra small angle X-ray scattering (2D USAXS). We found that power-law behaviour in small q- region of isotropic scattering patterns of LLDPE studied here, indicating that the density heterogeneity obeys mass fractal. Under stretching, isotropic 2D USAXS patterns of some LLDPE samples were transformed into butterfly patterns caused by heterogeneous deformation.

Superficial degradation evaluated through color change in weathered orange LLDPE

AbstractWe report the evaluation of superficial degradation of orange and colorless linear low density polyethylene samples exposed to weather. Color change and UV–VIS absorption were measured on samples exposed to the weather conditions of the city of Aguascalientes, Mexico, for more than a year. The color change was calculated in CIELAB units. Color change and absorption presented an exponential decay with time for orange samples, whereas they remained constant for colorless samples. No degradation products from the polymer matrix were revealed by UV–VIS spectroscopy, and apart from color change, no other degradation was noticed. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 458–463, 2009