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     

Oxidative degradations of oxodegradable LDPE enhanced with thermoplastic pea starch: Thermo‐mechanical properties,morphology, and UV‐ageing studies

The abiotic UV‐degradation behavior of oxodegradable LDPE was investigated in the presence of thermoplastic pea starch (TPPS) in this study. Oxodegradable LDPE was first melt‐blended with thermoplastic pea starch (TPPS) using an internal mixing chamber to enhance the abiotic oxidative degradation of oxodegradable LDPE. Because of their different affinity, maleated polyethylene was added as compatibilizer. Tensile properties, thermal properties, and morphology of resulting melt‐blends were determined at different content in TPPS. High content in TPPS (40 wt %) could be readily added to oxodegradable LDPE without affecting the tensile properties of resulting melt‐blends. UV‐ageing studies on compatibilized TPPS/oxodegradable LDPE melt‐blends were carried out by Attenuated Total Reflectance infrared spectroscopy (ATR‐FTIR), Dynamic Thermomechanical Analyses (DMTA) and Differential Scanning Calorimetry (DSC) under abiotic conditions. These results suggested a synergistic effect on the UV‐ageing of TPPS‐based melt‐blends provided by both components during the first stage of UV‐irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

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     

Tensile properties,morphology, and biodegradability of blends of starch with various thermoplastics

In the present study, blends of starch with different thermoplastics were prepared by a melt blending technique. The tensile properties and morphology of the blends were measured. It was found that with increasing starch content in starch/ionomer blends, the tensile strength and modulus increase. But for starch/low‐density polyethylene (LDPE) and starch/aliphatic polyester (APES) blends, tensile strength and modulus decrease with increasing the starch loading. Elongation at break values of all the blend systems decrease with increasing starch loading. The scanning electron micrographs (SEM) support the findings of tensile properties. Better homogeneity is observed in starch/ionomer systems compared with that in starch/APES and starch/LDPE systems. Up to 50% starch content, the starch/ionomer blends appear as a single phase. The extent of phase interactions of starch/APES system lies in between the starch/LDPE and starch/ionomer systems. From the biodegradability studies of the blends it was found that, although the pure LDPE and ionomer are not biodegradable, the starch/LDPE and starch/ionomer blends are biodegradable with an appreciable rate. The rate of biodegradation of the starch/APES is very high as both the components are biodegradable. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2907–2915, 2002     

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     

Rheological and thermal properties of single‐site polyethylene blends

Branched polyethylenes, low‐density polyethylenes (LDPE1 and LDPE2) or long‐chain‐branched very low density polyethylenes (VLDPE2), were blended with very low density polyethylenes containing short branches (VLDPE1 and VLDPE3). The rheological and thermal measurements of the pure copolymers and their blends (VLDPE1–LDPE1, VLDPE1–LDPE2, VLDPE1–VLDPE2, and VLDPE2–VLDPE3) were taken by controlled stress rheometry and differential scanning calorimetry, respectively. The shear‐thinning effect became stronger with increasing long‐chain‐branched polymer compositions when it was correlated with the flow behavior index, and the extent of shear thinning was different for each blend set. Stronger shear thinning and a linear composition dependence of the zero‐shear viscosity were observed for the VLDPE1–LDPE1 and VLDPE1–LDPE2 blends. These blends followed the log additivity rule, and this indicated that they were miscible in the melt at all compositions. In contrast, a deviation from the log additivity rule was observed for the VLDPE1–VLDPE2 blend compositions with 50% or less VLDPE2 and for the VLDPE3–VLDPE2 blends with 50% or more VLDPE2. The thermal properties of the blends were consistent with the rheological properties. VLDPE1–LDPE1 and VLDPE1–LDPE2 showed that these blends were characteristic of a single‐component system at all compositions, whereas the phase separation (immiscibility) was detected only for VLDPE1–VLDPE2 blends with 50% or less VLDPE2 and for VLDPE3–VLDPE2 blends with 50% or more VLDPE2. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1549–1557, 2005     

Development of nanofibrous morphology in LDPE/LLDPE/PP blends and its effect on mechanical properties of blend films

Nanofibrous morphology has been observed in ternary blends of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and isotactic polypropylene (PP) when these were melt‐extruded via slit die followed by hot stretching. The morphology was dependent on the concentration of the component polymers in ternary blend LDPE/LLDPE/PP. The films were characterized by wide angle X‐ray diffraction (XRD), scanning electron microscopy (SEM), and testing of mechanical properties. The XRD patterns reveal that the β phase of PP is obtained in the as‐stretched nanofibrillar composites, whose concentration decreases with the increase of LLDPE concentration. The presence of PP nanofibrils shows significant nucleation ability for crystallization of LDPE/LLDPE blend. The SEM observations of etched samples show an isotropic blend of LDPE and LLDPE reinforced with more or less randomly distributed and well‐defined nanofibrils of PP, which were generated in situ. The tensile modulus and strength of LDPE/LLDPE/PP blends were significantly enhanced in the machine direction than in the transverse direction with increasing LLDPE concentration. The ultimate elongation increased with increasing LLDPE concentration, and there was a critical LLDPE concentration above which it increased considerably. There was a dramatic increase in the falling dart impact strength for films obtained by blow extrusion of these blends. These impressive mechanical properties of extruded samples can be explained on the basis of the formation of PP nanofibrils with high aspect ratio (at least 10), which imparted reinforcement to the LDPE/LLDPE blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Low‐density polyethylene/plasticized tapioca starch blends with the low‐density polyethylene functionalized with maleate ester: Mechanical and thermal properties

In this study, the mechanical and thermal properties of low‐density polyethylene (LDPE)/thermoplastic tapioca starch blends were determined with LDPE‐g‐dibutyl maleate as the compatibilizer. Mechanical testing for the evaluation of the impact strength and tensile properties was carried our as per standard ASTM methods. Thermogravimetric analysis and differential scanning calorimetry were also used to assess the thermal degradation of the blends. Scanning electron micrographs were used to analyze fracture and blend morphologies. The results show significant improvement in the mechanical properties due to the addition of the compatibilizer, which effectively linked the two immiscible blend components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1109–1120, 2006     

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.     

Blends of low‐density polyethylene and liquid crystalline polymer

Blends of low‐density polyethylene (LDPE) and a glass‐filled thermotropic liquid crystalline polymer (LCP‐g) have been prepared by melt mixing techniques. The thermal transitions, dynamic behavior, morphology and crystalline properties of the blends have been measured by DSC, DMTA, SEM and XRD respectively. The crystallinity decreased with increase in LCP‐g content in the blends. At higher levels of LCP‐g, crystal growth is favored in the PE phase. From DSC, it is found that the thermal stability of the blends increased with the LCP‐g content. The variation of storage modulus, loss modulus and stiffness as a function of blend ratio suggested the phase inversion at the 40–50% level of LCP‐g in the blend. SEM studies revealed that with the increase in LCP‐g content, the flow of the matrix was restricted.     

Natural weather,soil burial and sea water ageing of low‐density polyethylene: Effect of starch/linear low‐density polyethylene masterbatch

Degradation of the blends of low‐density polyethylene (LDPE) with a starch‐based additive namely, polystarch N was studied under various environmental conditions such as natural weather, soil and sea water in Saudi Arabia. Stress–strain properties and thermal behavior were investigated for the LDPE and LDPE/polystarch N blend having 40% (w/w) of polystarch N. Environmental ageing resulted in the reduction of percentage of elongation and crystallinity for the blend. Rheological studies and scanning electron microscope photomicrographs of the polymer samples retrieved after ageing showed that addition of polystarch N enhanced the degradation of LDPE. This is ascribed to high extent of chain scission and leaching out of starch present in polystarch N, which was corroborated by the results of morphology and Fourier transform infrared spectroscopy analyses. In the case of underground soil ageing, microbes present in the soil consume the starch in the blend, thus accelerating the degradation process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical and thermal properties of LDPE‐cellulose acetate phthalate blends—Effect of maleic anhydride‐grafted LDPE compatibilizer

Biodegradable blends of LDPE and cellulose acetate phthalate have been prepared. Maleic anhydride‐grafted LDPE has been added as a compatibilizer to this blend. The elastic modulus and tensile strength has been considerably improved by adding LDPE‐g‐maleic anhydride compatibilizer. Scanning electron microscope micrographs reflected the observed results for the increase in mechanical properties of the blend. Further blend morphology exhibited a deformed matrix for the compatibilized blends. Thermogravimetric analysis studies showed two‐stage degradation for the blends. Differential scanning calorimetry thermograms showed a loss of crystallinity for the LDPE phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Improving low‐density polyethylene/poly(ethylene terephthalate) blends with graft copolymers

Blends of low‐density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) were prepared with different weight compositions with a plasticorder at 240°C at a rotor speed of 64 rpm for 10 min. The physicomechanical properties of the prepared blends were investigated with special reference to the effects of the blend ratio. Graft copolymers, that is, LDPE‐grafted acrylic acid and LDPE‐grafted acrylonitrile, were prepared with γ‐irradiation. The copolymers were melt‐mixed in various contents (i.e., 3, 5, 7, and 9 phr) with a LDPE/PET blend with a weight ratio of 75/25 and used as compatibilizers. The effect of the compatibilizer contents on the physicomechanical properties and equilibrium swelling of the binary blend was investigated. With an increase in the compatibilizer content up to 7 phr, the blend showed an improvement in the physicomechanical properties and reduced equilibrium swelling in comparison with the uncompatibilized one. The addition of a compatibilizer beyond 7 phr did not improve the blend properties any further. The efficiency of the compatibilizers (7 phr) was also evaluated by studies of the phase morphology (scanning electron microscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Fabrication and properties of poly(l‐lactide) nanofibers via blend sea‐island melt spinning

Poly(l ‐lactide) (PLLA) nanofibers were prepared by melt extrusion of immiscible blends of PLLA/low density polyethylene (LDPE) and subsequent removal of the LDPE matrix from the blend fibers. The effect of blends composition and draw ratio on the phase structure of the blend fibers, crystallization, mechanical properties, and the diameter of the PLLA nanofibers was investigated. It is found that the diameter of the PLLA phase gradually increases with the increase of PLLA content. With the variation of PLLA content from 50 to 60 wt %, the average diameter of acquired PLLA nanofibers changes from 119 to 153 nm under the draw ratio of 1.5. When further increasing the content of PLLA to 65%, it is difficult to acquire PLLA nanofibers due to the poor dissolving properties between PLLA and LDPE components. Oriented PLLA nanofibers with the average diameter of 92 nm can be fabricated from PLLA/LDPE (50/50, wt %) blends under the draw ratio of 2. The present results suggest that it is possible to acquire polymer nanofibers with high output using blend sea‐island melt spinning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41228.     

Crystallization of low‐density polyethylene‐ and linear low‐density polyethylene‐rich blends

The crystallization of a series of low‐density polyethylene (LDPE)‐ and linear low‐density polyethylene (LLDPE)‐rich blends was examined using differential scanning calorimetry (DSC). DSC analysis after continuous slow cooling showed a broadening of the LLDPE melt peak and subsequent increase in the area of a second lower‐temperature peak with increasing concentration of LDPE. Melt endotherms following stepwise crystallization (thermal fractionation) detailed the effect of the addition of LDPE to LLDPE, showing a nonlinear broadening in the melting distribution of lamellae, across the temperature range 80–140°C, with increasing concentration of LDPE. An increase in the population of crystallites melting in the region between 110 and 120°C, a region where as a pure component LDPE does not melt, was observed. A decrease in the crystallite population over the temperature range where LDPE exhibits its primary melting peaks (90–110°C) was noted, indicating that a proportion of the lamellae in this temperature range (attributed to either LDPE or LLDPE) were shifted to a higher melt temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1009–1016, 2000     

Use of Functionalized Metallocene Copolymers from Ethylene and Polar Olefins as Compatibilizers for Low‐Density‐Polyethylene/Starch and Low‐Density‐Polyethylene/Dextran Blends

Summary: Functionalized metallocene copolymers synthesized from ethylene with 5‐hexen‐1‐ol and ethylene with 10‐undecen‐1‐ol were used as compatibilizers in LDPE/starch and LDPE/dextran blends in order to improve the interfacial adhesion between hydrophobic LDPE and hydrophilic natural polymers. An increase in tensile modulus and a slight decrease in tensile strength was observed when poly[ethylene‐co‐(10‐undecen‐1‐ol)] was added to a 70:30 wt.‐% LDPE/dextran blend, whereas the addition of poly[ethylene‐co‐(5‐hexen‐1‐ol)] as compatibilizer resulted in obtaining a more rigid material with a slightly higher modulus. Scanning electron microscopy of modified dextran blends containing 3 wt.‐% of both compatibilizers showed some degree of phase cocontinuity. Enhanced interfacial adhesion and decrease in particle size of starch was observed when 5 wt.‐% of poly [ethylene‐co‐(5‐hexen‐1‐ol)] copolymer was used as the compatibilizer in starch blends. The crystallization temperature of LDPE, determined by DSC, was shifted to a slightly higher temperature as a consequence of the addition of the compatibilizers. The existence of phase segregation was also revealed by thermal analysis when 5 wt.‐% of the copolymers were used as blend modifiers.

SEM micrograph of 70:30 wt.‐% LDPE/dextran blend with added poly[ethylene‐co‐(5‐hexen‐1‐ol)] compatibilizer.     

Effect of propylation of starch with different degrees of substitution on the properties and characteristics of starch‐low density polyethylene blend films

Corn starch was modified by propylation and degree of substitution (DS) of four starch modifications were 0.61, 1.56, 2.27, and 2.51. Different films were prepared by blending native and propylated starch with low‐density polyethylene (LDPE). The mechanical properties, thermal properties, water absorption capacity, and biodegradability of the blend films varied with the quantity of starch as well as DS. Tensile strength, elongation, and melt flow index of propylated starch blend films were higher compared to the corresponding native starch blend film. These properties improved with increase in DS from 1.56 to 2.51. Propylated starch blend films were found thermally stable than native starch blend films. There was a decrease in water absorption capacity for the films containing propylated starch at high DS. Enzymatic and soil burial degradation results showed that biodegradability of starch‐LDPE films increased with the increase in the starch concentration but it decreased with increase in the DS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Tailoring the morphology and properties of poly(lactic acid)/poly(ethylene)‐co‐(vinyl acetate)/starch blends via reactive compatibilization

Poly(lactic acid)/poly(ethylene‐co‐vinyl acetate)/starch (PLA/EVA/starch) ternary blends were prepared by multi‐step melt processing (reactive extrusion) in the presence of maleic anhydride (MA), benzoyl peroxide and glycerol. The effects of MA and glycerol concentration on the morphology and properties of the PLA/EVA/starch blends were studied using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, the Molau experiment, dynamic mechanical thermal analysis and differential scanning calorimetry etc. The plasticization and compatibilization provided a synergistic effect to these blends accompanied by a significant reduction in starch particle size and an increase in interfacial adhesion. Starch was finely dispersed in the ternary blends with a dimension of 0.5 ? 2 µm. Furthermore, EVA‐coated starch or a starch‐in‐EVA type of morphology was observed for the reactively compatibilized PLA/EVA/starch blends. The EVA with starch gradually changed into a co‐continuous phase with increasing MA concentration. Consequently, the toughness of the blends was improved. Since property stability of starch is an issue, the tensile properties of these blends were measured after different storage times and the blends showed good property stability. Copyright © 2012 Society of Chemical Industry     

Miscibility,thermal behaviour,morphology and mechanical properties of binary blends of poly[(R)‐3‐hydroxybutyrate] with poly(γ‐benzyl‐L‐glutamate)+

The miscibility, thermal behaviour, morphology and mechanical properties of poly[(R)‐3‐hydroxybutyrate] (PHB) with poly(γ‐benzyl‐L ‐glutamate) (PBLG) are investigated by means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile tests. The DSC results show that PHB and PBLG are immiscible in the melt state. Such immiscibility also exists in the amorphous state due to a clear two‐phase separated structure observed by SEM measurements. The blend samples with different thermal history, namely as original and melt samples separately, display differences in thermal behaviour such as the DSC scan profile, the crystallinity and the melting temperature of PHB. The crystallization of PHB both from the molten state and the amorphous state is retarded on addition of the second component. The SEM measurements reveal that a phase inversion occurs between the PHB/PBLG (60/40) and PHB/PBLG (40/60) blends. Except for the PHB/PBLG (40/60) blend, a microphase separated structure is observed for all blend compositions. The mechanical properties vary considerably with blend composition. Compared with pure components, the PHB/PBLG (20/80) blend shows a certain improvement in mechanical properties. © 2001 Society of Chemical Industry