Rheological,thermal, and morphological properties of low‐density polyethylene/ultra‐high‐molecular‐weight polyethylene and linear low‐density polyethylene/ultra‐high‐molecular‐weight polyethylene blends

The dynamic rheological behavior of low‐density polyethylene (LDPE)/ultra‐high‐molecular‐weight polyethylene (UHMWPE) blends and linear low‐density polyethylene (LLDPE)/UHMWPE blends was measured in a parallel‐plate rheometer at 180, 190, and 200°C. Analysis of the log–additivity rule, Cole–Cole plots, Han curves, and Van Gurp curves of the LDPE/UHMWPE blends indicated that the blends were miscible in the melt. In contrast, the rheological properties of LLDPE/UHMWPE showed that the miscibility of the blends was decided by the composition of LLDPE. The differential scanning calorimetry results and scanning electron microscopy photos of the LLDPE/UHMWPE blends were consistent with the rheological properties, whereas with regard to the thermal and morphological properties of LDPE/UHMWPE blends, the results reveal three endothermic peaks and phase separation, which indicated a liquid–solid phase separation in the LDPE/UHMWPE blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of recycled high‐density polyethylene by low‐density and linear‐low‐density polyethylenes

The present study investigated mixed polyolefin compositions with the major component being a post‐consumer, milk bottle grade high‐density polyethylene (HDPE) for use in large‐scale injection moldings. Both rheological and mechanical properties of the developed blends are benchmarked against those shown by a currently used HDPE injection molding grade, in order to find a potential composition for its replacement. Possibility of such replacement via modification of recycled high‐density polyethylene (reHDPE) by low‐density polyethylene (LDPE) and linear‐low‐density polyethylene (LLDPE) is discussed. Overall, mechanical and rheological data showed that LDPE is a better modifier for reHDPE than LLDPE. Mechanical properties of reHDPE/LLDPE blends were lower than additive, thus demonstrating the lack of compatibility between the blend components in the solid state. Mechanical properties of reHDPE/LDPE blends were either equal to or higher than calculated from linear additivity. Capillary rheological measurements showed that values of apparent viscosity for LLDPE blends were very similar to those of the more viscous parent in the blend, whereas apparent viscosities of reHDPE/LDPE blends depended neither on concentration nor on type (viscosity) of LDPE. Further rheological and thermal studies on reHDPE/LDPE blends indicated that the blend constituents were partially miscible in the melt and cocrystallized in the solid state.     

Effect of cellulose nanofibers and acetylated cellulose nanofibers on the properties of low‐density polyethylene/thermoplastic starch blends

The aim of this study was to evaluate the effect of cellulose nanofibers (CNFs) and acetylated cellulose nanofibers (ACNFs) on the properties of low‐density polyethylene/thermoplastic starch/polyethylene‐grafted maleic anhydride (LDPE/TPS/PE‐g‐MA) blends. For this purpose, CNFs, isolated from wheat straw fibers, were first acetylated using acetic anhydride in order to modify their hydrophilicity. Afterwards, LDPE/TPS/PE‐g‐MA blends were reinforced using either CNFs or ACNFs at various concentrations (1–5 wt%) with a twin‐screw extruder. The mechanical results demonstrated that addition of ACNFs more significantly improved the ultimate tensile strength and Young's modulus of blends than addition of CNFs, albeit elongation at break of both reinforced blends decreased compared with the neat sample. Additionally, biodegradability and water absorption capacity of blends improved due to the incorporation of both nanofibers, these effects being more pronounced for CNF‐assisted blends than ACNF‐reinforced counterparts. © 2018 Society of Chemical Industry     

High performance modified thermoplastic starch/linear low‐density polyethylene blends in one‐step extrusion

In this study, the morphology and the mechanical properties of thermoplastic starch (TPS)/linear low‐density polyethylene (LLDPE) blends prepared by one‐step and two‐step extrusion processing conditions were contrasted. In the presence of citric acid (CA), the compatibility of TPS/PE blends were proved to transfer to a high continuous dispersion in one‐step extrusion process by scanning electron microscopy analysis. By increasing the interaction between two phases, the mechanical properties of the blends were markedly improved, even reached the levels of the conventional plastics. The rheological study proved that the viscosity (η) of TPS and TPS/PE blends were both decreasing with increase in the content of CA at the same temperature, which ascribed to the acidity of CA was propitious to fragmentation and dissolution of cornstarch granules, deteriorated the chain entanglement in starch, and weakened the interaction of starch molecules. Both FTIR spectroscopy and thermal properties analysis of TPSs and TPS/PE blends showed that the interactions between starch and plasticizer became stronger in the presence of CA. POLYM. COMPOS. 28:89–97, 2007. © 2007 Society of Plastics Engineers     

Effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on thermal properties,morphology, and tensile properties of low‐density polyethylene (LDPE) and corn starch blends

The effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the thermal properties, morphology, and tensile properties of blends of low‐density polyethylene (LDPE) and corn starch were studied with a differential scanning calorimeter (DSC), scanning electron microscope (SEM), and Instron Universal Testing Machine, respectively. Corn starch–LDPE blends with different starch content and with or without the addition of PE‐g‐MA were prepared with a lab‐scale twin‐screw extruder. The crystallization temperature of LDPE–corn starch–PE‐g‐MA blends was similar to that of pure LDPE but higher than that of LDPE–corn starch blends. The interfacial properties between corn starch and LDPE were improved after PE‐g‐MA addition, as evidenced by the structure morphology revealed by SEM. The tensile strength and elongation at break of corn starch–LDPE–PE‐g‐MA blends were greater than those of LDPE–corn starch blends, and their differences became more pronounced at higher starch contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2904–2911, 2003     

Photobiodegradation of low‐density polyethylene/banana starch films

The effects of the starch content, photosensitizer content, and compatibilizer on the photobiodegradability of low‐density polyethylene (LDPE) and banana starch polymer blend films were investigated. The compatibilizer and photosensitizer used in the films were PE‐graft‐maleic anhydride (PE‐g‐MA) and benzophenone, respectively. Dried banana starch at 0–20% (w/w) of LDPE, benzophenone at 0–1% (w/w) of LDPE, and PE‐g‐MA at 10% (w/w) of banana starch were added to LDPE. The photodegradation of the blend films was performed with outdoor exposure. The progress of the photodegradation was followed by determining the carbonyl index derived from Fourier transform IR measurements and the changes in tensile properties. Biodegradation of the blend films was investigated by a soil burial test. The biodegradation process was followed by measuring the changes in the physical appearance, weight loss, and tensile properties of the films. The results showed that both photo‐ and biodegradation rates increased with increasing amounts of banana starch, whereas the tensile properties of the films decreased. The blends with higher amounts of benzophenone showed higher rates of photodegradation, although their biodegradation rates were reduced with an increase in benzophenone content. The addition of PE‐g‐MA into polymer blends led to an increase in the tensile properties whereas the photobiodegradation was slightly decreased compared to the films without PE‐g‐MA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2725–2736, 2006     

Influence of maleic anhydride on the compatibility of thermal plasticized starch and linear low‐density polyethylene

In the presence of dicumyl peroxide, the compatibility of thermal plasticized starch/linear low‐density polyethylene (TPS/LLDPE) blends using maleic anhydride (MAH) as compatibilizer was investigated. The thermal plasticization of starch and its compatibilizing modification with LLDPE was accomplished in a single‐screw extruder at the same time. We prepared three types of blends containing different percentages of TPS and MAH. The content of MAH based on LLDPE was 0, 1, and 2 wt %, respectively. The morphology of the blends was studied by SEM. It was found that, with the addition of MAH, the blends have good interfacial adhesion and finely dispersed TPS and LLDPE phases, which is reflected in the mechanical and thermal properties of the blends. The blends containing MAH showed higher tensile strength, elongation at break, and thermal stability than those of blends without MAH. The rheologic properties of the blends demonstrated the existence of processing. Finally, the dynamic thermal mechanical analysis results indicated that, with the addition of MAH, the compatibility between TPS and LLDPE in the blends was substantially improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 686–695, 2004     

Preparation and characterization of low‐density polyethylene/banana starch films containing compatibilizer and photosensitizer

Composite films containing various percentages of banana starch and low‐density polyethylene (LDPE) were prepared. The effects of the compatibilizer, banana starch content, and photosensitizer content on the thermal and tensile properties of these films were investigated. The banana starch content was varied from 5 to 20 wt % of LDPE, whereas benzophenone was added as a photosensitizer in three different amounts (0.25, 0.5, and 1 wt %) based on LDPE. In these films PE‐graft‐maleic anhydride (PE‐g‐MA) was used as a compatibilizer at 10 wt % banana starch. It was found that the thermal stability of the composite films remained unchanged with respect to the amount of banana starch and benzophenone content. The addition of banana starch had no effect on the melting temperature and degree of crystallinity of the films. Similarly, PE‐g‐MA had no effect on the melting temperature but decreased the degree of crystallinity of the LDPE phase. Benzophenone caused an increase in the melting temperature but decreased the degree of crystallinity of LDPE in the films. Increasing the amount of banana starch decreased the tensile properties of the composite films. The addition of PE‐g‐MA as a compatibilizer increased the tensile properties compared with the uncompatibilized films. However, benzophenone had no effect on the tensile properties of the blend films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2717–2724, 2006     

The properties of blends of maleic‐anhydride‐grafted polyethylene and thermoplastic starch using hyperbranched polyester polyol as a plasticizer

The first aim of this study was to prepare thermoplastic starch (TPS), namely blends of tapioca starch and hyperbranched polyester polyol and to evaluate the hyperbranched polyester polyol (HBP) as a plasticizing agent for tapioca starch. The second aim was to prepare blends of maleic‐anhydride‐grafted low‐density polyethylene (LDPE‐g‐MA) and TPS, and to evaluate the effect of the mass ratio LDPE‐g‐MA/TPS on the structural, thermal, rheological, morphological, and mechanical properties of the blends. The melting and crystallization temperatures of the LDPE‐g‐MA/TPS blends did not correlate well with the ratio of LDPE‐g‐MA/TPS. The blends exhibited a reduction in the A‐type crystallinity and a pseudoplastic rheological behavior. V‐type crystallinity was not observed for neither TPS nor LDPE‐g‐MA/TPS blends. Scanning electronic microscophy provided an evidence for the presence of starch granules in all the blends and for low interaction degree between LDPE‐g‐MA and TPS. Young's modulus and tensile strength of the LDPE‐g‐MA/TPS blends decreased with the decreasing LDPE‐g‐MA/TPS ratio. POLYM. ENG. SCI., 55:2526–2533, 2015. © 2015 Society of Plastics Engineers     

Effects of ultrasonic oscillations on processing behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene/low‐density polyethylene blends

The influences of ultrasonic oscillations on rheological behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene (mLLDPE)/low‐density polyethylene (LDPE) blends were investigated. The experimental results showed that the presence of ultrasonic oscillations can increase the extrusion productivity of mLLDPE/LDPE blends and decrease their die pressure and melt viscosity during extrusion. Incorporation of LDPE increases the critical shear rate for sharkskin formation of extrudate, crystallinity, and mechanical properties of mLLDPE. The processing behavior and mechanical properties of mLLDPE/LDPE blends were further improved in the presence of ultrasonic oscillations during extrusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2522–2527, 2004     

Thermal and mechanical properties of linear low‐density polyethylene/low‐density polyethylene/wax ternary blends

The thermal and mechanical properties of uncrosslinked three‐component blends of linear low‐density polyethylene (LLDPE), low‐density polyethylene (LDPE), and a hard, paraffinic Fischer–Tropsch wax were investigated. A decrease in the total crystallinity with an increase in both LDPE and wax contents was observed. It was also observed that experimental enthalpy values of LLDPE in the blends were generally higher than the theoretically expected values, whereas in the case of LDPE the theoretically expected values were higher than the experimental values. In the presence of higher wax content there was a good correlation between experimental and theoretically expected enthalpy values. The DSC results showed changes in peak temperature of melting, as well as peak width, with changing blend composition. Most of these changes are explained in terms of the preferred cocrystallization of wax with LLDPE. Young's modulus, yield stress, and stress at break decreased with increasing LDPE content, whereas elongation at yield increased. This is in line with the decreasing crystallinity and increasing amorphous content expected with increasing LDPE content. Deviations from this behavior for samples containing 10% wax and relatively low LDPE contents are explained in terms of lower tie chain fractions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1748–1755, 2005     

Morphological and rheological properties of (low‐density polyethylene)/thermoplastic starch blend: investigation of the role of high elastic network

Rheological and morphological properties of low‐density polyethylene (LDPE) and thermoplastic starch (TPS) with low‐density polyethylene‐grafted‐maleic anhydride as a compatibilizer were investigated. The results showed that the circularity of the droplets decreased with increasing TPS content. The presence of compatibilizer led to finer morphology and higher continuity. The rheological analyses showed that TPS and compatibilizer can increase elasticity and viscosity of the blend dramatically. In addition, the compatibilizer enhanced the compatibility of the blends, as evidenced by the shifting of the relaxation time peak of TPS to longer times. The rheological properties of the neat components and their blends were discussed by the Carreau‐Yasuda and fractional Zener models. The fractional Zener model results proved the existence of network structure in the compatibilized blends. The transient properties of blends showed that TPS and compatibilized blends had strong overshoot compared with the uncompatibilized blend, owing to the formation of high elastic network in their structure. J. VINYL ADDIT. TECHNOL., 20:250–259, 2014. © 2014 Society of Plastics Engineers     

Transparent low‐density polyethylene/starch nanocomposite films

Low‐density polyethylene (LDPE)/starch nanocomposite films were prepared by melt extrusion process. The first step includes the preparation of starch–clay nanocomposite by solution intercalation method. The resultant product was then melt mixed with the main matrix, which is LDPE. Maleic anhydride‐grafted polyethylene (MAgPE), produced by reactive extrusion, was used as a compatibilizer between starch and LDPE phases. The effects of using compatibilizer, clay, and plasticizers on physico‐mechanical properties were investigated. The results indicated that the initial intercalation reaction of clay layers with starch molecules, the conversion of starch into thermoplastic starch (TPS) by plasticizers, and using MAgPE as a compatibilizer provided uniform distribution of both starch particles and clay layers, without any need of alkyl ammonium treatment, in LDPE matrix. The nanocomposite films exhibited better tensile properties compared to clay‐free ones. In addition, the transparency of LDPE film did not significantly change in the presence of TPS and clay particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical properties and morphology of polylactide,linear low‐density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer‐grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882‐91. On the basis of this, LLDPE 80 [80 wt % LLDPE and 20 wt % poly(L ‐lactic acid) (PLLA)] and MA‐g‐low‐density polyethylene 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) were found to be an optimum composition. The blends were characterized according to their mechanical, thermal, and morphological behavior. Fourier transform infrared spectroscopy revealed that the presence of compatibilizer enhanced the blend compatibility to some extent. The morphological characteristics of the blends with and without compatibilizer were examined by scanning electron microscopy. The dispersion of PLLA in the LLDPE matrix increased with the addition of compatibilizer. This blend may be used for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Co‐crystallization in ternary polyethylene blends: tie crystal formation and mechanical properties improvement

Understanding the co‐crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co‐crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler ? Natta linear low density polyethylene (ZN‐LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40 wt% and the LDPE/ZN‐LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X‐ray scattering, small angle X‐ray scattering and field emission SEM techniques revealed the formation of two distinct co‐crystals in the blends. Fine LDPE/ZN‐LLDPE co‐crystals, named tie crystals, dispersed within the amorphous gallery between the coarse HDPE/ZN‐LLDPE co‐crystals were characterized for the first time in this study. It is shown that the tie crystals strengthen the amorphous gallery and play a major role in the mechanical performance of the blend.© 2016 Society of Chemical Industry     

Rheology and morphology study of immiscible linear low‐density polyethylene/poly(lactic acid) blends filled with nanosilica particles

The objectives of this study are to investigate the effect of silica nanoparticles on the morphology and rheological behavior of immiscible linear low‐density polyethylene/poly(lactic acid) (LLDPE/PLA) blends. Melt blending method is applied to prepare the blends and their nanocomposites. Scanning electron microscope and parallel plate rheometer were used to investigate morphology and rheological behavior of the blend nanocomposites. Scanning electron microscope results demonstrated a significant change in morphology behavior by incorporation of silica nanoparticles. A significant reduction in the PLA droplet for LLDPE/PLA (75/25) with 8 wt % silica was observed. The rheological studies illustrated that for all samples storage modulus and complex viscosity of blend nanocomposites are higher than neat blends. Finally, melt rigidity of blend nanocomposites was estimated by measurement of rheological properties using a rotational rheometer through small amplitude oscillatory shear experiments. As a result, through the shear data, a high value quantity as a criteria for melt rigidity is obtained for the LLDPE/PLA (75/25) with 8 wt % silica in comparing to the other samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45526.     

Effects of glycerol and PE‐g‐MA on morphology,thermal and tensile properties of LDPE and rice starch blends

The effects of glycerol and polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the morphology, thermal properties, and tensile properties of low‐density polyethylene (LDPE) and rice starch blends were studied by scanning electron microscopy (SEM), differential scanning calorimetry, and the Instron Universal Testing Machine, respectively. Blends of LDPE/rice starch, LDPE/rice starch/glycerol, and LDPE/rice starch/glycerol/PE‐g‐MA with different starch contents were prepared by using a laboratory scale twin‐screw extruder. The distribution of rice starch in LDPE matrix became homogenous after the addition of glycerol. The interfacial adhesion between rice starch and LDPE was improved by the addition of PE‐g‐MA as demonstrated by SEM. The crystallization temperatures of LDPE/rice starch/glycerol blends and LDPE/rice starch/glycerol/PE‐g‐MA blends were similar to that of pure LDPE but higher than that of LDPE/rice starch blends. Both the tensile strength and the elongation at break followed the order of rice starch/LDPE/glycerol/PE‐g‐MA blends > rice starch/LDPE/glycerol > LDPE/rice starch blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 344–350, 2004     

Toughening of polylactide by melt blending with linear low‐density polyethylene

Melt blending of polylactide and linear low‐density polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactide‐polyethylene (PLLA‐PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA‐PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA–;PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3757–3768, 2003     

Linear low‐density polyethylene/(soya powder) blends containing polyethylene‐g‐(maleic anhydride) as a compatibilizer

Blends were made from linear low‐density polyethylene (LLDPE) and various amounts of soya powder. The soya powder content was varied from 5 to 20 wt%. Polyethylene‐g‐(maleic anhydride) (PE‐g‐MA) was used as a compatibilizer. Tensile strength and elongation at break (EB) decreased with increasing soya powder content. However, Young's modulus increased with the incorporation of soya powder. The addition of PE‐g‐MA as a compatibilizer increased the tensile strength, EB, and modulus of the blends. The interfacial adhesion between soya powder and LLDPE was improved by the incorporation of PE‐g‐MA, as demonstrated by scanning electron microscopy. Increasing the content of soya powder reduced the crystallinity of the LLDPE phase. The addition of PE‐g‐MA had no significant effect on melting temperature, but the degree of crystallinity of the LLDPE was increased. The thermal stability of the blends was determined by using thermogravimetric analysis. Thermal stability decreased with increasing soya powder loading. However, the addition of PE‐g‐MA slightly increased the thermal stability of LLDPE/(soya powder) blends. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Influence of branching characteristics on thermal and mechanical properties of Ziegler–Natta and metallocene hexene linear low‐density polyethylene blends with low‐density polyethylene

The effect of the branch content (BC) and composition distribution (CD) of linear low‐density polyethylene (LLDPE) on the thermal and mechanical properties of its blends with LDPE were studied. All blends and pure resins were conditioned in a Haake PolyDrive blender at 190°C and in the presence of adequate amounts of antioxidant. Two metallocene LLDPEs (m‐LLDPE) and one Ziegler–Natta (ZN) hexene LLDPE were melt blended with the same LDPE. The effect of the BC was investigated by blending two hexene m‐LLDPEs of similar weight‐average molecular weights and molecular weight distributions but different BCs with the same LDPE. The effect of the CD was studied by using a ZN and an m‐LLDPE with similar weight‐average molecular weights, BCs, and comonomer type. Low‐BC m‐LLDPE blends showed separate crystallization whereas cocrystallization was observed in the high‐BC m‐LLDPE‐rich blends. However, ZN‐LLDPE/LDPE blends showed separate crystallization together with a third population of cocrystals. The influence of the crystallization behavior was reflected in the mechanical properties. The BC influenced the modulus, ultimate tensile strength, and toughness. The addition of a small amount of LDPE to a low‐BC m‐LLDPE resulted in a major improvement in the toughness, whereas the results for the high‐BC pair followed the additivity rule. ZN‐LLDPE blends with LDPE blends were found to be more compatible and exhibited superior mechanical properties compared to m‐LLDPE counterparts with the same weight‐average molecular weight and BC. All mechanical properties of ZN‐LLDPE blends follow the linear rule of mixtures. However, the CD had a stronger influence on the mechanical properties in comparison to the BC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2488–2498, 2005