Morphology and deformation of compatibilized polystyrene low density polyethylene blends

This investigation deals with the morphology and tensile behavior of polystyrene/low density polyethylene blends compatibilized by hydrogenated styrene‐b‐butadiene‐b‐styrene triblock copolymer. The stress‐strain measurements indicate that blends with excellent toughness were achieved, due to the compatibilizing role of the triblock copolymer in the system. The morphology of the blends was observed by scanning electron microscopy (SEM), and the results show that the state of polystyrene changes from continuous phase to dispersed phase with increasing LDPE content. The correlation between mechanical properties and morphology is discussed. The morphologies of the tensile bars were also examined by SEM, and the deformation mechanisms of the blend were further analysed according to fractography. © 1999 Society of Chemical Industry     

Mechanical properties of uncrosslinked and crosslinked linear low‐density polyethylene/wax blends

The mechanical properties of uncrosslinked and crosslinked linear low‐density polyethylene (LLDPE)/wax blends were investigated, using differential scanning calorimetry (DSC), tensile testing, and melt flow indexing. A decrease in the degree of crystallinity, as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. The Young's modulus increased with increased wax portions, and there was a higher increase for crosslinked blends. The yield stress generally decreased with increased peroxide content. Crosslinking caused an increase in elongation at yield, but increased wax content caused a decrease in elongation at yield. The stress at break generally increased with increasing peroxide content, but it decreased with increased wax content. The elongation at break decreased with an increase in the DCP concentration. Melt flow rate measurements indicated a mutual miscibility in LLDPE/wax blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 973–980, 2001     

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     

Melt rheology of compatibilized polystyrene/low density polyethylene blends

Investigations have been made on the melt rheological behaviors of compatibilized blends composed of polystyrene, low density polyethylene and hydrogenated (styrene‐butadiene‐styrene) triblock copolymer used as a compatibilizer. The experiments were carried out on a capillary rheometer. The effects of shear stress, temperature and blending ratio on the activation energy for viscous flow and melt viscosity of the blends are described. The study shows that the viscosity of the blends exhibits a maximum or minimum value at a certain blending ratio. The activation energy for viscous flow decreases with increasing LDPE content. Furthermore, the concept of equal‐viscosity temperature is presented and its role in the processing of the blend is discussed. In addition, the morphology of the extrudate sample of the blends was observed by scanning electron microscopy and the correlation between the morphology and the rheological properties is explored. © 1999 Society of Chemical Industry     

Effect of epoxy functionalized compatibilizer on the mechanical properties of low‐density polyethylene/plasticized tapioca starch blends

A series of low‐density polyethylene (LDPE) blends with varying proportions of plasticized tapioca starch have been used for the study of their mechanical properties. A functionalized epoxy resin, namely, poly(ethylene‐co‐glycidyl methacrylate) has been used as the compatibilizer. The impact and tensile properties have been measured by standard ASTM methods. The mechanical properties are seen to improve significantly with the addition of the epoxy compatibilizer, approaching values close to those of virgin LDPE. The scanning electron micrographs of the compatibilized blends show ductile failure which evidently contribute to improved mechanical properties. © 2001 Society of Chemical Industry     

Morphology and tensile properties of high-density polyethylene/natural rubber/thermoplastic tapioca starch blends: The effect of citric acid-modified tapioca starch

The effect of citric acid on the tensile properties of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends was investigated. The ratio between HDPE/NR was fixed at 70/30 and used as the matrix system. TPS loadings, after modification with citric acid (TPSCA) and without modification (TPS), were varied from 0 to 30 wt %. The morphologies and tensile properties of HDPE/NR blends were evaluated as a function of TPS loadings. The tensile strength, Young's modulus, and elongation at break were found to decrease with increasing TPS loading. However, a slight improvement in the tensile strength of HDPE/NR/TPSCA blends at 5 and 10 wt % TPS loadings were observed. TPS can be partly depolymerised to produce a low viscosity product when processed with citric acid. TPS with low viscosity can easily disperse in the thermoplastic natural rubber (TPNR) system and reduce the surface tension at the interphase of TPS-HDPE/NR as shown by scanning electron microscopy (SEM). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Melt strength of blends of linear low density polyethylene and comb polymers

The melt strength of a metallocene linear low-density polyethylene (m-LLDPE) can be enhanced significantly by blending in less than 10 wt% of long chain branched comb polymer. The extent of the enhancement could be ten-fold and depends on the architectural details of the comb polymer. Comb polymers primarily affect melt strength and have little effect on other properties such as shear thinning, melt index, melt index ratio, and intrinsic tear.Balancing melt strength properties against shear-thinning properties is important in LLDPE fabrication processes. One approach would be to augment the effect of comb polymer by blending in another component, namely an easy processing (also known as sparsely long chain branched) LLDPE. In the examples given here, the enhancements in melt strength and shear thinning properties of the base polymer were found to be additive, i.e. a simple weighted sum of component properties matched the blend properties within 10%.     

Crystallization behaviour of isotactic polypropylene/linear low density polyethylene blends

Crystallization behaviour of isotactic polypropylene/linear low density polyethylene (iPP/LLDPE) blends has been investigated by optical microscopy and DSC. Crystallization of iPP depends upon blend composition and thermal history. When blended with LLDPE, the crystallization temperature of iPP, T_c, decreased slightly. Crystallinity did not change in the range 0-80wt% LLDPE; there were only slight changes in the crystalline structure, but LLDPE seemed to resist forming the β type of spherulites. Below 80 wt% of LLDPE, iPP was a continuous phase. The iPP spherulite growth rate was almost constant; however, overall crystallization decreased due to decreasing primary nuclei density.     

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,mechanical, and dielectric behaviors of crosslinked linear low density polyethylene/polyolefin elastomers blends

Crosslinked linear low density polyethylene (XLPE) containing polyolefin elastomers (POE) has been evaluated. The blends with different dicumyl peroxide (DCP) and POE contents have been prepared and processed by compression molding. A series of the samples obtained have been investigated by gel content determination, scanning electron microscopy (SEM), different scanning calorimetry (DSC), mechanical, and dielectric behaviors measurements. The results obtained clearly show the relevant influence of the POE content, as well as of the DCP content, which tends to enhance crosslinking. As expected, the toughness of XLPE is improved by using adequate content of POE, and the blends exhibit a much more similar tensile behavior to that of elastomer. In addition, the results indicate that the blends possess the excellent dielectric behaviors, such as dielectric constant and dissipation factor. The crystallinity of the blends decreases as the DCP and POE contents increase. The melting temperature of the blends also decreases with the increase of DCP content, while POE content has few influences on the melting temperature of the blends. The SEM images strongly reveal that the blends are partially compatible, and the POE can be dispersed well in the matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1920–1927, 2007     

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     

Morphology and rheological properties of compatibilized low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch blends

Morphology and rheological properties of low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch (LDPE/LLDPE/TPS) blends are experimentally investigated and theoretically analyzed using rheological models. Blending of LDPE/LLDPE (70/30 wt/wt) with 5–20 wt % of TPS and 3 wt % of PE‐grafted maleic anhydride (PE‐g‐MA) as a compatibilizer is performed in a twin‐screw extruder. Scanning electron micrographs show a fairly good dispersion of TPS in PE matrices in the presence of PE‐g‐MA. However, as the TPS content increases, the starch particle size increases. X‐ray diffraction patterns exhibit that with increase in TPS content, the intensity of the crystallization peaks slightly decreases and consequently crystal sizes of the blends decrease. The rheological analyses indicate that TPS can increase the elasticity and viscosity of the blends. With increasing the amount of TPS, starch particles interactions intensify and as a result the blend interface become weaker which are confirmed by relaxation time spectra and the prediction results of emulsion Palierne and Gramespacher‐Meissner models. It is demonstrated that there is a better agreement between experimental rheological data and Coran model than the emulsion models. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44719.     

线性低密度聚乙烯/有机蒙脱土纳米复合材料的制备及性能研究

通过熔融共混法制备了线性低密度聚乙烯／有机蒙脱土（LLDPEtOMMT）纳米复合材料,采用X-射线衍射分析（XRD）和透射电镜（TEM）对材料的结构进行表征,研究了OMMT的用量对LLDPE／OMMT纳米复合材料力学性能及阻燃性能的影响。结果表明,当OMMT的用量为30％（重量百分比）8寸,材料的极限氧指数（LOI）从180％提高到23．8％,热释放速率峰值（PHRR）从LLDPE的771．9kW／m2下降到5113kW／m2,下降幅度高达33．8％,表现出较好的阻燃性能;同时材料也呈现出良好的力学性能。     

茂金属线型低密度聚乙烯的结构与性能

利用傅里叶变换红外光谱、凝胶渗透色谱、差式扫描量热法和力学性能测量等手段表征了茂金属线型低密度聚乙烯(mLLDPE)和传统线型低密度聚乙烯(LLDPE)的结构及性能,用热分级法表征了LLDPE的片晶厚度多散性,测试了mLDPE薄膜的相关性能。结果发现,mLLDPE的片晶厚度分布指数为1.1347,小于传统LLDPE,表明其具有更好的支化均匀性,但其相对分子质量分布窄;mLLDPE薄膜具有较高的落镖冲击强度、撕裂强度、热封强度和突出的光学性能。     

Nonisothermal crystallization kinetics of linear bimodal–polyethylene (LBPE) and LBPE/low‐density polyethylene blends

Nonisothermal crystallization kinetics of linear bimodal–polyethylene (LBPE) and the blends of LBPE/low‐density polyethylene (LDPE) were studied using DSC at various scanning rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the nonisothermal crystallization process of LBPE and LBPE/LDPE blends. The theory of Ozawa was also used to analyze the LBPE DSC data. Kinetic parameters such as, for example, the Avrami exponent (n), the kinetic crystallization rate constant (Z_c), the crystallization peak temperature (T_p), and the half‐time of crystallization (t_1/2) were determined at various scanning rates. The appearance of double melting peaks and double crystallization peaks in the heating and cooling DSC curves of LBPE/LDPE blends indicated that LBPE and LDPE could crystallize, respectively. As a result of these studies, the Z_c of LBPE increases with the increase of cooling rates and the T_p of LBPE for LBPE/LDPE blends first increases with increasing LBPE content in the blends and reaches its maximum, then decreases as the LBPE content further increases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2431–2437, 2003     

Nanocomposites formed from linear low density polyethylene and organoclays

Polyethylene-clay nanocomposites were prepared by melt compounding various combinations of a maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA), a linear low density polyethylene (LLDPE), and two organoclays. The two types of organoclay were selected to show the effect of the number of alkyl groups attached to the nitrogen of the organic modifier on exfoliation and improvement of mechanical properties. Nanocomposites derived from the organoclay having two alkyl tails, M₂(HT)₂, exhibited better dispersion and improvement of mechanical properties than nanocomposites based on the organoclay having one alkyl tail M₃(HT)₁. This result is the opposite of what is observed for nylon-6 nanocomposites. In addition, the rheological properties and gas permeability of the nanocomposites derived from the organoclay having two alkyl tails, M₂(HT)₂ were investigated. Both melt viscosity and melt tension (melt strength) increased with increased content of clay (MMT) and LLDPE-g-MA. Gas permeability was decreased by the addition of MMT.     

Spherulite nucleation in polypropylene blends with low density polyethylene

Primary nucleation of spherulites in blends of isotactic polypropylene (iPP) with low density polyethylene (LDPE) was investigated by means of differential scanning calorimetry and optical microscopy. The number of iPP spherulites in the blend decreases with increasing LDPE concentration to a much greater extent than follows from the decreasing amount of iPP. The shapes of spherulite size distributions indicate that athermal (heterogeneous) primary nucleation is inhibited. The density of primary nucleation in the blends decreases strongly with increasing mixing time. The same effect was observed in the blends with the nucleating agent which was added to iPP or LDPE. These experiments demonstrate that heterogenoeus nuclei migrate across interphase boundaries from the iPP melt to the LDPE melt during the mixing process. It is suggested that the interfacial energy difference between the nuclei and the molten components of the blend is responsible for the migration of nuclei.     

Effect of different metallic hydroxides on flame‐retardant properties of low density polyethylene/melamine polyphosphate/starch composites

The flame retardancy of synthesized melamine polyphosphate (MPP) in combination with starch (ST) and different metallic hydroxides was investigated in low density polyethylene (LDPE) by limiting oxygen index (LOI) and vertical burning test. The results indicated that the LOI value of composite comprising Al(OH)₃(ATH) was higher than those of composites at the same additive loading with Mg(OH)₂(MH)or Fe(OH)₃(FH), which increased from 22 to 27%. And the composite comprising ATH passed V1 rating without causing molten drops. In addition, thermostability and morphology were characterized by differential scanning calorimeter (DSC), thermogravimetry (TG), derivative thermogravimetry (DTG), and scanning electron microscope (SEM). The results demonstrated that the crystallization of the composites remained unaffected after the incorporation of metallic hydroxide. The thermal degradation behavior of LDPE composites and the morphology of residual charred layer were changed. It also can be concluded that there was a synergy between certain metallic hydroxide and MPP after analyzing the residual charred layer using X‐ray diffraction (XRD). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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