Density Polyethylene Blends Research Articles

Study on the co-pyrolysis of high density polyethylene and potato blends using thermogravimetric analyzer and tubular furnace

The interactions between high density polyethylene (HDPE) and potato during their primary and secondary co-pyrolysis process were investigated by a thermogravimetric analyzer (TGA) and a tubular furnace. Kinetic analysis has shown that the devolatilization of potato was relatively faster compared to those of cellulosic materials, which has been ascribed to the multi-side-chain structure and lower polymerization degree of starch. The pyrolysis process of potato can be divided into three stages, and the main thermal degradation took place between 178 and 378°C, while the HDPE decomposition occurred in a single stage in the temperature range of 380–517°C. In the case of blends, the weight loss differences (ΔW) between experimental and theoretical ones were less than ±8% in all cases, and the co-pyrolysis process of potato and HDPE can be described as two consecutive first order reactions, the apparent activation energies of blends were almost invariable, suggested that only physical step limitation was found in the primary co-pyrolysis process of potato and HDPE. On the contrary, the results of tubular furnace experiment showed that due to the relatively long gas resident time, the interaction occurred in the gas phase not only favored the formation of gaseous products, but also improved the bio-oil quality by significantly reducing the oxygen-to-carbon ratios (O/C) of the pyrolysis oil.

Effect of EVA Content upon the Dielectric Properties in LDPE-EVA Films

Low density polyethylene (LDPE) blends with different percentages of ethylene vinyl acetate polymer membranes were prepared by a hot press casting method. The effects of EVA content on the electrical properties of LDPE were studied. The results on the electrical properties revealed that the surface resistance, volume resistivity, and breakdown voltage of the LDPE decrease with EVA content and reach a minimum at a 30 wt% of EVA. Dielectric constant and dielectric loss factor were increased with increasing EVA content up to 30 wt% of EVA. It can be deduced that the electrical properties of LDPE are improved by blending with EVA.

Low Density Polyethylene (LDPE) blends based on Poly(3-Hydroxi-Butyrate) (PHB) and Guar Gum (GG) biodegradable polymers

LDPE blends based on PHB and GG biodegradable polymers were prepared by melt mixing in a twin screw extruder. The mechanical properties of the materials were evaluated. Preliminary information about the biodegradation behavior of the specimens was obtained by visual observation of samples removed from the simulated soil in 90 days. The results indicated that LDPE/PHB blends may be used for designing LDPE based materials with increased susceptibility to degradation, if elongation at break and impact properties are not determinant factors of their performance. LDPE based materials on GG present values of flexural and mechanical strength lower than those of LDPE/PHB blends. LDPE/PHB/GG blends exhibit unsatisfactory properties. Apparently, the effect of addition of GG to LDPE on the biodegradation behavior of LDPE/GG blends was less intense than the effect caused by addition of PHB to the blends. Similar observation has occurred with the partial replacement of GG by PHB in the ternary blends.

Effect of confinement on glass dynamics and free volume in immiscible polystyrene/high‐density polyethylene blends

AbstractThe effect of confinement on glass dynamics combined with the corresponding free volume changes of amorphous polystyrene (PS) in blends with semi‐crystalline high‐density polyethylene (HDPE) have been investigated using thermal analyses and positron annihilation lifetime spectroscopy (PALS). Two different glass transition temperatures (Tg) were observed in a PS/HDPE blend due to the dissimilarity in the chemical structure, consistent with an immiscible blend. However, Tg of PS in the incompatible PS/HDPE blend showed an upward trend with increasing PS content resulting from the confinement effect, while Tg of the semi‐crystalline HDPE component became lower than that of neat HDPE. Moreover, the elevation of Tg of PS was enhanced with a decrease of free volume radius by comparing annealed and unannealed PS/HDPE blends. Positron results showed that the free volume radius clearly decreased with annealing for all compositions, although the free volume hole size agreed well with linear additivity, indicating that there was only a weak interaction between the two components. Combining PALS with thermal analysis results, the confinement effect on the glass dynamics and free volume of PS phase in PS/HDPE blends could be attributed to the shrinkage of HDPE during crystallization when HDPE acted as the continuous phase. © 2015 Society of Chemical Industry

Fabrication of Cellulose Based Reinforced Linear Low Density Polyethylene with Polyethylene Terephthalate Composite: Effect of <i> Acacia catechu </i> as Coupling Agent

Biodegradable reinforced composites are playing a vital role in the variety of application for their outstanding performance. Linear Low Density Polyethylene (LLDPE) and Polyethylene Tere-phthalate (PET) blends were prepared by twin screw extruder in different composition. The mechanical properties in 10% PET with LLDPE blend showed the best results where as tensile strength (TS) 9 MPa and percentage elongation at break (%Eb) 33. Cellulose based reinforced PET + LLDPE composite were prepared by compression molding with the optimized jute content 62% that revealed the highest mechanical properties. Cellulose based composites treated with Acacia catechu (AC) solutions (0.1% - 5% w/v) at different soaking time (2 - 20 min.) where observed significant improvement of the mechanical properties. Cellulose treated with 0.1% AC for 2 minutes soaking time depicted the highest mechanical properties and TS is 115% higher than untreated. Composite prepared with 0.1% AC treated showed the best mechanical properties as tensile strength (TS), bending strength (BS), tensile modulus (TM) and bending modulus (BM) were to be 47 MPa, 39 MPa, 1220 MPa and 1784 MPa respectively. The properties of TS, BS, TM and BM were improved as 9%, 30%, 14% and 34% respectively, which were better to untreated composite. Electrical properties such as dielectric constant and loss of the treated and untreated composites were found to be higher dielectric constant of treated jute composite than that of untreated samples. Water uptake and soil degradation of untreated and treated composites performed in significant study. The effect of AC with cellulose composites has found in remarkable changes in the mechanical properties.

Effects of reprocessing cycles and ageing on the rheological and mechanical properties of virgin-recycled HDPE blends

The reprocessing ability of virgin and recycled High Density Polyethylene (HDPE) blends has been investigated to examine the recycling feasibility in industrial production. Virgin-recycled HDPE blends were re-processed and re-formed up to three cycles by extrusion moulding. The effect of recycled HDPE content and reprocessing cycles coupled with ageing through “transyl” on the properties of the prepared blends was evaluated by tensile test and by melt flow index (MFI) tests. Furthermore, the ageing of the blends were studied via an immersion in “transyl” lubricant (Hydrocarbons, C10-C13, N-Alkanes, Isoalckanes, Cyclics, Aromatics (2–25%)). The sorption process was analyzed by gravimetric measurements at different temperatures. Also, diffusion coefficients of solvent molecules in the HDPE samples were identified. Results revealed that the mechanical properties of the samples worsened on increasing the level of recycled HDPE and after each reprocessing operation even if the most relevant decreases were observed after the first reprocessing. The processability of virgin-recycled HDPE blends has lead to slight decrease of viscosity, more remarkable on increasing the recycled HDPE content. The rheological behaviour was not influenced by the reprocessing only at the first three reprocessing cycles. The combination of reprocessing and accelerated ageing has degraded the material faster than either processing or ageing performed separately.

Mechanical and morphological properties of high density polyethylene and polylactide blends

Abstract Polyblend films were prepared from high-density polyethylene (HDPE) and poly(l-lactic acid) (PLLA) up to 20% PLLA by the melt blending method in an extrusion mixer with post-extrusion blown film attachment. The 80/20 (HDPE/PLLA) blend was compatibilized with maleic anhydride grafted polyethylene (PE-g-MA) in varying ratios [up to 8 parts per hundred of resin (phr)]. Tensile properties of the films were evaluated to obtain optimized composition for packaging applications of both non-compatibilized and compatibilized blends. The compositions HDPE80 (80% HDPE and 20% PLLA) and HD80C4 (80% HDPE, 20% PLLA and 4 phr compatibilizer) were found to be optimum for packaging applications. However, better tensile strength (at yield) and elongation (at break) of 80/20 (HDPE/PLLA) blend were noticed in the presence of PE-g-MA. Further, thermal properties and morphologies of these blends were evaluated. Differential scanning calorimetry (DSC) study revealed that blending does not much affect the crystalline melting point of HDPE and PLLA, but heat of fusion of 80/20 (HDPE/PLLA) blend was decreased as compared to that of neat HDPE. Spectroscopy studies showed evidence of the introduction of some new groups in the blends and gaining compatibility in the presence of PE-g-MA. The compatibilizer influenced the morphology of the blends, as apparent from scanning electron microscopy (SEM) and supported by Fourier transform infrared (FTIR).

Melt elongation flow behaviour of LDPE/LLDPE blends

The extensional rheological properties of low density polyethylene (LDPE)/linear low density polyethylene (LLDPE) blend melts were measured using a melt spinning technique under temperatures ranging from 160 to 200 °C and die extrusion velocities varying from 9 to 36 mm/s. The results showed that the melt elongation stress decreased with a rise of temperature while it increased with increasing extensional strain rate and the LDPE weight fraction. The dependence of the melt elongation viscosity on temperature roughly obeyed the Arrhenius equation, it increased with increasing extensional strain rate and the LDPE weight fraction when the extensional strain rate was lower than 0.5 s−1, and it reached a maximum when the extensional strain rate was about 0.5 s−1, which can be attributed to the stress hardening effect.

Development and Properties of High Density Polyethylene (HDPE) and Ethylene-Vinyl Acetate Copolymer (EVA) Blend Antioxidant Active Packaging Films Containing Quercetin

The antioxidant quercetin was incorporated into high density polyethylene (HDPE) and ethylene-vinyl acetate copolymer (EVA) films by flat compression. The mass ratio of HDPE : EVA was 65 : 35, and the amount of quercetin in the films was 0.74% (wt%) and 1.23%, respectively. The method of manufacturing the films achieved a high quercetin retention rate. The addition of quercetin did not significantly modify the thermal stability or the oxygen barrier of the films, while the water vapour barrier was weakened to some extent. Release of quercetin from the active antioxidant films into 50% ethanol (simulant for high alcohol containing products and milk as well as some dairy products) and 95% ethanol (simulant for fatty foods) at 37°C was periodically measured by HPLC over 45 days. The diffusion of antioxidant followed Fick's law. In 50 and 95% ethanol, the release content of quercetin was 70 and 10%, respectively, the diffusion coefficient (D) was 10−13 and 10−15 m2/s, and the partition coefficient (K) was 44 and 5863, respectively. The films showed a good release profile and could be used for the protection of foods. Copyright © 2014 John Wiley & Sons, Ltd.

The design and performance of a vane mixer based on extensional flow for polymer blends

ABSTRACTA new laboratory‐scale mixing device called the “Vane Mixer” was designed, built, and tested. The vane mixer consists of three vane plasticizing and conveying unit. In comparison with the existing laboratory mixers, material flow in this vane mixer is characterized by a high contribution from extensional flow. As the mixer has mixing chamber of very simple geometry, the cleaning is very easy and the material lost is very small. The influences of mixing time and rotor speed on dispersed phase size were characterized and discussed. Morphology data on model immiscible polystyrene/high density polyethylene (PS/HDPE) blend have proved the high distributive and dispersive mixing efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41551.

Potential role of nanofillers as compatibilizers in immiscible PLA/LDPE Blends

ABSTRACTThis article describes the use of commercial silica (SiO2) and calcium carbonate (CaCO3) nanofillers as compatibilizers in immiscible polylactide/low‐density polyethylene (PLA/LDPE) blends. The general aim of the study was to investigate the possibilities of replacing standard commodity plastics such as LDPE based on non‐renewable mineral oil resources with the biodegradable renewable polymer PLA in compatibilized PLA/LDPE blends for use in the packaging industry. The calculations of the minimal interfacial energy and optimal wetting abilities indicated that SiO2 filler was a better potential compatibilizer than CaCO3 for a given PLA/LDPE blend. This was due to its preferential localization at the interface. The significantly improved morphology of the ternary PLA/LDPE/SiO2 blend was found to present an increased strength, toughness, and crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41414.

Rheological behavior and mechanical properties of wood flour/high density polyethylene blends: Effects of esterification of wood with citric acid

This study explored the modifying effects of wood flour (WF) with citric acid (CA) on the rheological and mechanical properties of WF/high density polypropylene (HDPE) composites. WF was treated with CA, which acts a cross‐linking agent and melt‐blended with HDPE with a twin‐screw extruder. Injection molding was used to make tensile and impact tests samples. The rheological properties of the blends were characterized using a Haake microcompounder, torque‐, capillary‐, and rotational‐rheometer, respectively. Results show that the thermal stability of WF decreased after treatment. Compared with those of untreated composites, the tensile strength, elongation‐at‐break, and impact strength of the composites treated with 5% CA were reduced by 6%, 14%, and 16%, respectively. This reduction was attributed to embrittlement of WF, which may negatively influence the mechanical properties of the resulting composites. Scanning electron microscopy revealed better dispersion of CA‐treated WF in the composites than the untreated WF. For composites treated with 5% CA, the melt torque, viscosity, moduli, and shear stress decreased significantly, indicating an improvement in processibility. This improvement is attributed to uniform dispersion of the modified WF, as well as to better interfacial adhesion between WF and the matrix. Results suggest that treating WF with CA shows promise for improving the processibility of highly filled thermoplastic composites via extrusion/injection molding processing. POLYM. COMPOS., 37:553–560, 2016. © 2014 Society of Plastics Engineers

Effect of Maleic Anhydride (MA) on Properties of Recycled High Density Polyethylene/Ethylene Vinyl Acetate/Egg Shell Powder (rHDPE/EVA/ESP) Composites

The difference in polarity of recycled high density polyethylene (rHDPE) and ethylene vinyl acetate (EVA) blends leads to poor mechanical properties (Atul Rajan, 2013). Present works aim at finding the effects of maleic anhydride on the mechanical, morphological, and water resistance properties of rHDPE/EVA/ESP blends. It is shown that there is a significant improvement on tensile strength, interfacial adhesion between components, and water absorption resistance of adding maleic anhydride (MA) to rHDPE/EVA/ESP blends. This study may suggest that the MA can act as compatibilizer to enhance the interfacial interaction between the rHDPE and EVA matrix in the rHDPE/EVA/ESP composites.

Effects of electron beam irradiation on the structural properties of polylactic acid/polyethylene blends

The purpose of this research was to investigate the effects of electron beam irradiation on the properties of polylactic acid (PLA) and low density polyethylene (LDPE) blends. The PLA were compounded with 20–80% LDPE and were exposed to electron beam irradiation dosages of 20–120kGy. The results from gel content and X-ray diffraction analyses showed that the addition of LDPE to PLA effectively increased the gel content and crystallinity. However, an increasing percentage of LDPE reduced the tensile strength and Young’s modulus of the PLA/LDPE samples due to the lower intermolecular bonding of LDPE than of PLA. Moreover, an increase in irradiation dosages gradually decreased the mechanical properties of low-LDPE PLA/LDPE. In contrast, the increasing irradiation dosage enhanced the mechanical properties of higher-LDPE PLA/LDPE. These results indicate that higher amounts of LDPE effectively react with the release of free radicals within the amorphous phase if the blends are subjected to irradiation. The higher amounts of free radicals induce the formation of three-dimensional cross-linked networks in the polymer matrix and thus increase the gel content. The irradiation-induced cross-linking in PLA/LDPE samples improves the mechanical properties and crystallinity by promoting a structural rearrangement of the polymer matrix into a highly ordered structure.

Stress–Strain and Diffusion Behavior of Industrial Waste-filled Acrylonitrile–Butadiene Rubber/High Density Polyethylene Blends

Abstract The mechanical properties and diffusion behavior of marble waste (MW)-filled acrylonitrile–butadiene rubber (NBR)/high density polyethylene (HDPE) blends were studied as a function of blend composition. A sulfur curing system was employed to crosslink the thermoplastic elastomer (TPE) blends. The results obtained showed that the physical properties of vulcanized NBR/HDPE blends were enhanced with the addition of HDPE in MW-filled vulcanized NBR/HDPE blends. Mechanical properties such as stress–strain behavior, tensile strength, modulus, and % elongation at break and tear strength, were assessed and found to fluctuate with the blend ratio. HDPE-incorporated vulcanized NBR/HDPE blends have been found to reveal a reduced toluene uptake trend compare to the NBR compound.

Mechanical and shape memory behavior of chemically cross-linked SBS/LDPE blends

A series of polymeric shape memory system of chemically cross-linked poly(styrene-b-butadiene-b-styrene) triblock copolymer(SBS) and linear low density polyethylene(LDPE) blends were developed and characterized. The chemically cross-linked SBS/LDPE blends were prepared by varying the amount of initiator (DCP) between 0 and 1.5 wt.% and the ratio of SBS/LDPE ranges from 90/10 to 60/40. The cross-linked SBS/LDPE blends were fully characterized by gel content, tensile test, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC) and shape memory behavior. Results demonstrate that the cross-linking degree increases with the increment of the DCP content, leading to reductions in tensile strength and elongation at break. The transition temperature of cross-linked SBS/LDPE blends is tunable through changing SBS/LDPE ratio and DCP content. DMA test shows that the melt strength of the blends is influenced by the DCP and LDPE content. The chemically cross-linked SBS/LDPE blends have excellent shape memory effect when the cross-linking degree between 46 and 77 %. The shape recovery time decreases as the test temperature increases and the shape recovery rate decreases with cycle times increasing.

Carbon Black-Filled PE/PP/EPDM Blends: Phase Selective Localization of Carbon Black and EPDM-Induced Phase Stabilization

Higher filler loading in incompatible polymer blends generally leads to catastrophic deterioration of physico-mechanical properties. This investigation reports effect of an elastomeric compatibili-zer on the mechanical properties of carbon black (CB) filled immiscible Polypropylene (PP)/Low density polyethylene (PE) blends. The composites were prepared by melt compounding of PE, PP, ethylene propylene diene monomer (EPDM) and CB in different proportions. Elongation at break for 30wt.% CB-filled PE/ PP (1:1) blends did not show any improvement up to 10wt.% EPDM addition, suggesting absence of any comptabilization effect of EPDM in CB-filled blends, whereas unfilled blends exhibited good comptabilization and about 200% improvement in elongation at break was observed at 10wt.% EPDM content. DSC studies revealed good interactions between PE and EPDM phases, and there was no reduction in the crystallinity of either PE or PP phases up to 50% EPDM loading. The phase inversion was observed in 50–75wt.% EPDM loading. The micromechanical modeling of the composite suggests selective incorporation of CB in PE and EPDM phases. The results have been explained in the light of the percolation of carbon black in different phases and the role of EPDM as a compatibility modifier of PE and PP phases.

Effect of acrylonitrile–butadiene–styrene on flow behavior and mechanical properties of polylactic acid/low density polyethylene blend

ABSTRACTThe influence of acrylonitrile–butadiene–styrene (ABS) copolymer content on the properties of polylactic acid (PLA)/low density polyethylene (LDPE) blend (50/50) was investigated in the present paper. The blend (PLA/LDPE/ABS) was prepared in different ratios using a laboratory scale single screw extruder. The prepared blends were characterized in terms of rheological and mechanical properties. Rheological properties were studied using a capillary rheometer, and the Bagley's correction was performed. Shear rate (γr), shear stress (τr), shear viscosity (ηr), and non‐Newtonian index (n) were determined. The relationship between shear viscosity and temperature was also studied, and the flow activation energy at a constant shear rate (Eγ) was determined. The mechanical properties of the blends were investigated on dog‐bone‐shaped samples obtained by an injection molding machine. The tensile tests were performed using Testometric M350‐10KN, and the stress at break, strain at break, and Young's modulus were determined. Rheological properties revealed that the blend exhibited shear‐thinning behavior over the range of the studied shear rates, and the viscosity of the blend increased as the ABS content increased, whereas the flow activation energy decreased. Based on the mechanical properties determined for the prepared blends, it was found that no relation between ABS content and stress at break of the blend was regarded, whereas Young's modulus was significantly improved by the addition of ABS. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Study on filler content dependence of the onset of positive temperature coefficient (PTC) effect of electrical resistivity for UHMWPE/LDPE/CF composites based on their DC and AC electrical behaviors

Composites of carbon fibers (CF) filled with ultrahigh molecule weight polyethylene/low density polyethylene blend matrix (UHMWPE/LDPE) were prepared by kneading method. The positive temperature coefficient (PTC) effect of electrical resistivity of UHMWPE/LDPE/CF composites was investigated by direct current (DC) and alternating current (AC) measurements over the frequency range of 100–106.5 Hz from 30 to 150 °C. The onsets of PTC effect were found to be strongly depended upon the CF content even the melting behaviors were almost same for all composites. To interpret this phenomenon, a master curve of temperature–frequency–resistivity superposition was constructed for composites with different CF contents based on the AC resistivity. The CF content dependence of correlation length was related to the onset of PTC effect. The transitions of conductor–insulator were studied quantitatively by complex planes of AC impedance, and the calculated capacitances and resistances showed a similar PTC effect under DC. Based on the analysis of AC capacitance, the average distances between CFs were calculated using a plane capacitance model which varied with CF concentration and temperature, and the tendency was consistent to the PTC effect.

Effects of ionic liquid on the rheological properties of wood flour/high density polyethylene composites

Wood flour was treated with an ionic liquid, 1-(2-hydroxyethyl)-3-methylimidazolium chloride ([Hemim]Cl), to various weight percent gains. The treating effects on the rheological properties of the resulting wood flour/high density polyethylene (HDPE) blends were investigated using a Haake microcompounder and torque-, capillary-, and rotational-rheometer, respectively. Treatment with [Hemim]Cl caused a decrease in the crystallinity and an improvement in the thermoplasticity of wood flour. At low processing speeds, the melt torque and viscosity increased with increasing [Hemim]Cl content; while at high speed, they decreased or remained the same. [Hemim]Cl can broaden the processing window of wood flour/HDPE composites with stable flow and smooth product surfaces. The dynamic rheological results show that storage and loss moduli and complex viscosity of the composite melts increased with increasing [Hemim]Cl content.