Rheological behavior of ultrahigh molecular weight polyethylene/low‐density polyethylene blending gels with high solid content

For developing polyethylene (PE) fibers with relatively high mechanical properties but low cost, the rheological behaviors of ultrahigh molecular weight polyethylene (UPE) and low density polyethylene (LDPE) blending gels (UL blending gels) were investigated in terms of the shear‐induced chain interactions and the sol–gel transitions. UL blending gels with a fixed blend ratio 1/1 of UPE and LDPE but different solid contents (SCs) ranging from 2 wt% (UL‐2) to 10 wt% (UL‐10) were prepared using paraffin oil as solvent. The UL‐10 showed a more significant shear thinning behavior than others, and exhibited a little bit lower apparent viscosity than UPE gel with 5% SC (UPE‐5) at elevated temperature even though the SC of UL‐10 is double of that of UPE‐5. UL blending gel with low apparent viscosity and high SC could ensure smoothly and high‐efficient spinning. Rheological measurements confirmed no significant solid‐liquid phase separation of the system of UPE and LDPE in paraffin oil. At the same time, the macromolecular orientation under shear and structural viscosity also assured the blending gel UL‐10 an excellent spinning performance. UL blending fibers were prepared. The tensile strength of UL‐10 fiber reached 1.2 GPa which would satisfy industrial applications demanding relative high mechanical properties. POLYM. ENG. SCI., 58:22–27, 2018. © 2017 Society of Plastics Engineers     

复合添加剂对石蜡性能影响的研究

以聚乙烯蜡和硬脂酸为添加剂,采用水浴加热混合蜡测量滴熔点和粘度,在聚乙烯蜡质量百分含量为0％ ～ 15％、硬脂酸质量百分含量为0％ ～ 60％范围内,对石蜡的使用性能进行改性研究.实验结果表明,聚乙烯蜡和硬脂酸均对石蜡滴熔点和运动粘度有一定的影响.在聚乙烯蜡添加量为0％ ～ 15％的范围内,改性石蜡的性能得到明显改善,其中改性石蜡的滴熔点呈缓慢增高趋势,后保持稳定;当其添加量在3％～5％的范围内,改性石蜡的熔点快速升高.在聚乙烯蜡加入量为3％时加入质量分数为5％～60％硬脂酸进行对比试验.硬脂酸在添加量为5％～25％时,改性石蜡滴熔点呈下降趋势;硬脂酸添加量为25％～60％时,改性石蜡滴熔点上升,但上升效果不明显.     

Improvement of the polarity of polyethylene with oxidized Fischer–Tropsch paraffin wax and its influence on the final mechanical properties

The easy, low‐cost modification of the polarity of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) through blending with oxidized Fischer–Tropsch wax was investigated. A 10 wt % concentration of the wax increased the polar component of the total surface free energy 10 times for LDPE and 4.5 times for HDPE. Modified LDPE also had significantly higher adhesion to the polar substrate, which was represented by a crosslinked epoxy‐based resin. This behavior was not observed for HDPE. The conservation of the good mechanical properties of polyethylene was observed. The wax content had only a moderate influence on the mechanical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1164–1168, 2005     

Studies on LDPE—Cyanoethylated lignocellulosics blends using epoxy functionalized LDPE as compatibilizer

Rubberwood flour and cellulose have been plasticized by cyanoethylation and then blended with low‐density polyethylene (LDPE). A small quantity of epoxy functionalized polyethylene i.e., polyethylene‐co‐glycidyl methacrylate (PEGMA) has been added to further enhance the mechanical properties. The mechanical properties were measured according to the standard ASTM methods. SEM analysis was performed for both fractured and unfractured blend specimens. The mechanical properties were improved by the addition of PEGMA compatibilizer. LDPE blends with cyanoethylated wood flour (CYWF) showed higher tensile strength and modulus than cyanoethylated cellulose CYC‐LDPE blends. However CYC‐LDPE blends exhibited higher relative elongation at break values as compared with the former. The TGA analysis showed lowering of thermal stability as the filler content is increased and degradation temperature of LDPE is shifted slightly to lower temperature. DSC analysis showed loss of crystallinity for the LDPE phase as the filler content is increased for both types of blends. Dielectric properties of the blends were similar to LDPE, but were lowered on adding PEGMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 219–237, 2006     

Preparation and characterization of low density polyethylene/ethylene methyl acrylate glycidyl methacrylate/organoclay nanocomposites

The effects of organoclay type, compatibilizer, and the addition order of components during melt‐blending process on the morphology and thermal, mechanical, and flow properties of ternary nanocomposites based on low‐density polyethylene (LDPE) were investigated. As a compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA), as organoclays Cloisites® 15A, 25A, and 30B were used. All samples were prepared by a corotating twin screw extruder, followed by injection molding. The highest increase of the basal spacing for ternary nanocomposites was obtained in LDPE/E‐MA‐GMA/Cloisite® 30B nanocomposites with interlayer spacing of 59.2 Å. Organoclay and compatibilizer addition did not influence the melting/crystallization behavior of the compositions, and both compatibilizer and organoclays had no significant nucleation activity in LDPE. Among the ternary nanocomposites, the maximum increase in tensile strength and tensile modulus values was observed for nanocomposites containing organoclay Cloisite® 15A. The improvement with respect to neat LDPE was 43% for tensile strength and 44% for tensile modulus. According to the mechanical analysis, the best sequence of component addition was the one in which LDPE, organoclay, and compatibilizer were simultaneously fed to the extruder in the first run, and the product of the first run was extruded once more. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 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     

木质素填充LDPE、EVA对复合物性能的影响

以木质素为填充剂分别与低密度聚乙烯(LDPE)、乙烯-乙酸乙烯酯共聚物(EVA)共混,经双螺杆造粒机共混挤出造粒,再经吹塑成膜。研究了木质素/LDPE、木质素/EVA共混物薄膜的表面形貌、力学性能、热性能和红外光谱。热分析表明木质素与EVA共混物的热稳定性比木质素与LDPE的共混物热稳定性好;红外光谱分析表明木质素与EVA分子间产生了强烈的相互作用,扫描电镜分析表明木质素与EVA共混的相容性较好,力学性能分析表明低于30%的木质素与LDPE、EVA共混力学性能较好。     

The effect of paraffin on fiber dispersion and mechanical properties of polyolefin–sawdust composites

This article reports on the influence of the paraffin (PAR) on the wood fiber (WF) dispersion in different polyethylene (low‐density polyethylene, high‐density polyethylene, recycled polyethylene) matrices, as well as on the melt flow behavior and mechanical properties of WF‐reinforced polyethylene (PE) composites. In the presence of paraffin, the composites showed improved tensile and flexural strength and modulus, but lower impact strength and elongation at break. The extent of improvement in mechanical properties depends on paraffin content and type of polyethylene; the most effective paraffin was in LDPE‐based composites. Paraffin‐treated WF showed lower moisture absorption ability in comparison with unmodified wood fiber. The phase segregation process was investigated for PE/PAR blends by DSC method. It was shown that an increase of paraffin concentration in the PE/PAR blend leads to a decrease of PE melting temperature and an increase of paraffin melting temperature; it indicates a net exchange of material from paraffin towards polyethylene. However, generally both components of PE/PAR blends remain immiscible. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2385–2393, 2004     

Properties of different chitosan/low‐density polyethylene antibacterial plastics

A series of low‐density polyethylene (LDPE) antibacterial functional plastics were prepared by mechanical blending with commercial chitosan (CS), self‐made water‐soluble chitosan (W‐CS), and microchitosan as antibacterial agents. The effects of the antibacterial agent content on the elongation at break of the obtained plastics were tested, and the bacteriostatic effects against Escherichia coli, Bacillus subtilis, and Proteus species were investigated. The results indicate that the elongation at break of LDPE with antibacterial agent decreased and had a slower decline when the mass ratio of CS to LDPE was greater than 0.5 : 100. The LDPE‐based plastics showed different antibacterial activities against the three experimental strains, and plastics with W‐CS exhibited the best antibacterial activity against B. subtilis. However, the antibacterial content had little effect on the antibacterial ratio. Moreover, 6‐week soil burial tests indicated that the addition of CS caused a decrease in the resistance of LDPE to microbiological deterioration in a natural environment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Blends of triazine‐based hyperbranched polyether with LDPE and plasticized PVC

Triazine‐based hyperbranched polyether was obtained by earlier reported method and blended with low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC) separately to improve some desirable properties of those linear polymers. The properties like processability, mechanical properties, flammability, etc. of those linear polymers were studied by blending with 1–7.5 phr of hyperbranched polyether. The mechanical properties were also measured after thermal aging and leaching in different chemical media. SEM study indicates that both polymers exhibit homogenous morphology at all dose levels. The mechanical properties like tensile strength, elongation at break, hardness, etc. of LDPE and PVC increase with the increase of dose level of hyperbranched polyether. The flame retardant behavior as measured by limiting oxygen index (LOI) for all blends indicates an enhanced LOI value compared to the polymer without hyperbranched polyether. The processing behavior of both types of blends as measured by solution viscosity and melt flow rate value indicates that hyperbranched polyether acts as a process aid for those base polymers. The effect of leaching and heat aging of these linear polymers on the mechanical properties showed that hyperbranched polyether is a superior antidegradant compared to the commercially used N‐isopropyl‐N‐phenyl p‐phenylene diamine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 648–654, 2007     

Interfacial adhesion evaluation in (low‐density polyethylene)/elastomer blends

Low‐density polyethylene (LDPE) with different elastomers at a ratio of 50/50 wt% blends was prepared by using a co‐rotating twin‐screw extruder. Three kinds of elastomers were used: ground tire rubber (GTR), partially crosslinked butyl rubber (Kalar^®), and styrene‐butadiene‐rubber block copolymer (SBS; Kraton^®). For better characterization of interaction between polyethylene and elastomer, influence of the type of elastomer on the properties of compositions LDPE/elastomer was determined. In the studies, two types of partially crosslinked butyl rubber (differing over filler content and Mooney viscosity) and two types of SBS (differing over structure: linear/branched) were used. The influence of kind and type of elastomer on static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties, and morphology of obtained compositions were characterized. LDPE/linear SBS copolymer blend had the best mechanical properties, as a result of better compatibility in comparison with other investigated blends. The reason for improved compatibility was an increase of mobility of chain segments in the amorphous phase of polyethylene associated with their partial plasticization by flexible polybutadiene blocks present in SBS copolymer. J. VINYL ADDIT. TECHNOL., 22:492–500, 2016. © 2015 Society of Plastics Engineers     

PA6/LDPE/PE-g-MAH共混纳米纤维的制备及结构研究

采用共混海岛纺丝法制备聚酰胺6/低密度聚乙烯/聚乙烯接枝马来酸酐(PA6/LDPE/PE-g-MAH)共混纤维,溶解剥离出LDPE基体相,可制备出PA6纳米纤维;研究了共混物的组成和纺丝条件对共混纤维的相结构、结晶、力学性能及PA6纳米纤维直径的影响。结果表明:随着共混物中PA6分散相含量增加,PA6纳米纤维的直径逐渐增大;PA6质量分数从30%增加至60%时,PA6纳米纤维平均直径由107 nm增至149nm;PA6质量分数为70%时,由于相逆转无法得到PA6纳米纤维;在PA6质量分数为55%条件下,提高拉伸倍数,PA6纳米纤维的直径进一步降低,且结晶度、力学性能增加。     

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.     

Binary and ternary blends of recycled high‐density polyethylene containing polypropylenes

Binary and ternary blends of the high viscosity recycled high‐density polyethylene (reHDPE) from milk bottles, containing either homopolymer polypropylene (PP) or copolymer polypropylene (coPP), were developed in an effort to reduce viscosity and encourage ease of processing by injection molding, without a significant loss in mechanical properties. A grade of PP and a grade of coPP that had crystallization temperatures close to and slightly lower than that of reHDPE were chosen for blending in order to obtain simultaneous crystallization of the reHDPE and (co)PP phases. The resulting reHDPE/(co)PP blends (reHDPE wt% = 77) generally showed very good mechanical properties and, in particular, sufficiently high impact strength while engendering considerably lower viscosity than reHDPE. The PP was more useful at very high and low shear rates whereas the coPP was the most efficient in the mid‐range of shear rates (10² – 10³ sec^?1). Good impact resistance shown by the reHDPE/(co)PP blends was attributed in part to the fine dispersion of (co)PP phase, possible involvement of a portion of the polymers in a co‐continuous structure and simultaneous crystallization of the components. Ternary blends of reHDPE (reHDPE wt% = 77), PP and low‐density polyethylene (LDPE) showed good mechanical performance, although they were more viscous than (co)PP blends. In the ternary blends, co‐crystallization of reHDPE and LDPE phases was preserved (1).     

Rheological and mechanical properties of composites made from wood flour and recycled LDPE/HDPE blend

The effect of compounding method is studied with respect to the rheological behavior and mechanical properties of composites made of wood flour and a blend of two main components of plastics waste in municipal solid waste, low-density polyethylene (LDPE) and high-density polyethylene (HDPE). The effects of recycling process on the rheological behavior of LDPE and HDPE blends were investigated. Initially, samples of virgin LDPE and HDPE were thermo-mechanically degraded twice under controlled conditions in an extruder. The recycled materials and wood flour were then compounded by two different mixing methods: simultaneous mixing of all components and pre-mixing, including the blending of polymers in molten state, grinding and subsequent compounding with wood flour. The rheological and mechanical properties of the LDPE/HDPE blend and resultant composites were determined. The results showed that recycling increased the complex viscosity of the LDPE/HDPE blend and it exhibited miscible behavior in a molten state. Rheological testing indicated that the complex viscosity and storage modulus of the composites made by pre-mixing method were higher than that made by the simultaneous method. The results also showed that melt pre-mixing of the polymeric matrix (recycled LDPE and HDPE) improved the mechanical properties of the wood–plastic composites.     

Modification of the polarity and adhesive properties of polyolefins through blending with maleic anhydride grafted Fischer–Tropsch paraffin wax

The modification of the polarity and adhesive properties of linear low‐density polyethylene, low‐density polyethylene, and isotactic polypropylene through blending with paraffin wax (Fischer–Tropsch synthesis), grafted by maleic anhydride, was investigated. Maleic anhydride grafted paraffin wax significantly increased the polar component of the total surface free energy of polyolefins. Modified polyolefins also had significantly higher adhesion to the polar substrate, a crosslinked, epoxy‐based resin. The conservation of the good mechanical properties of the blends was observed up to 10 wt % wax, except for isotactic polypropylene blends, for which there was a reduction in the stress and strain at break at wax concentrations higher than 5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3069–3074, 2006     

Influence of octyl substituted octakis(dimethylsiloxy)octasilsesquioxane on the morphology and thermal and mechanical properties of low density polyethylene

Low density polyethylene (LDPE) was melt blended with octyl substituted octakis(dimethylsiloxy)octasilsesquioxane (AS8) prepared in high yield by hydrosilylation of octene with octakis(hydrodimethylsiloxy)octasilsesquioxane. Two procedures were used to incorporate AS8 into LDPE at nanolevel and their efficiency was investigated by X‐ray diffraction (XRD), scanning electron microscopy, atomic force microscopy (AFM), differential scanning calorimetry, thermogravimetry and mechanical characterization. A slight increase of crystallite mean dimensions was observed by XRD in both types of LDPE‐AS8 composites compared with neat LDPE. Better AS8 dispersion was observed by AFM in the composite prepared by the first procedure and the increase of both tensile strength and elongation at break in this composite confirmed the nanolevel dispersion and interface improvement in this case. AS8 influence in the final stages of polyethylene fracture was illustrated by AFM of elongated tensile specimens and a new mechanism of AS8 action was suggested. An interesting behavior consisting of simultaneous improvement of elastic modulus, strength and ductility was detected in the low range of polyhedral oligomeric silsesquioxane concentration in LDPE (0.5 wt%). © 2013 Society of Chemical Industry     

Application of paraffin and silver coated titania nanoparticles in polyethylene nanocomposite food packaging films

In this work, 3% and 5% TiO₂/Ag nanoparticles were dispersed in low‐density polyethylene through melt blending process, and subsequently nanocomposite films were prepared by hot pressing. Paraffin was used for the first time in this work as compatibilizer agent. The effect of TiO₂/Ag nanoparticle content, as well as compatibilizer dosage on the antimicrobial, morphological, mechanical, and optical performance of the nanocomposite films was investigated. Improved mechanical properties of the nanocomposite films were found on using paraffin as compatibilizer in comparison with the neat low‐density polyethylene (LDPE) films. The optical study results also showed that the addition of TiO₂/Ag to the LDPE films does not drastically change the film appearance other than making them more reddish. The fabricated nanocomposites presented in this study could be a suitable choice for food packaging (subject to further investigation of the food packaging behavior). The results showed that both TiO₂/Ag nanoparticle and compatibilizer are needed to prevent the bacteria growth in the film. The best result was obtained by using 5% nanoparticle and 4% paraffin compatibilizer where the bacteria growth rate was significantly reduced by 95%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45913.     

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