Structure development and property changes in high‐density polyethylene/calcium carbonate blends during pan‐milling

A new self‐designed mechanochemical reactor, inlaid pan‐mill, was used in studying high density polyethylene (HDPE) and calcium carbonate (CaCO₃) blends. The effects of CaCO₃ on the crushing and structure of HDPE matrix and the properties of HDPE/CaCO₃ blends were investigated. Scanning electron microscopy, Fourier transformed IR spectroscopy, dynamical mechanical testing analysis, capillary rheometer, and Instron material testing system were used to characterize the structure of HDPE and evaluate the properties of HDPE/CaCO₃ blends. The introduction of calcium carbonate during milling improved milling efficiency, and time needed for each cycle was greatly reduced. Oxygen‐containing groups on HDPE chains, which were produced during milling, increased interfacial interactions and improved the dispersion and distribution of calcium carbonate particles in HDPE/CaCO₃ blends. Rheological, thermal, and mechanical properties were also improved. The elongation at break of milled blends with high concentrations of calcium carbonate was significantly higher than that of unmilled blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1459–1464, 1999     

Tensile property and interfacial dewetting in the calcite filled HDPE, LDPE, and LLDPE composites

Mechanical properties and complex melt viscosity of unfilled and the calcite (calcium carbonate: CaCO₃) filled high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE) composites using dumbbell bar and film specimens are studied. In addition, the formation of air holes between calcium carbonate and the resin matrix was investigated from the phase morphology and interfacial behavior between the above constituents upon stretching using scanning electron microscopy. The tensile stress and the complex melt viscosity of the calcite filled (50%) polyethylene composites were higher than that of unfilled ones, implying that the reinforcing effect of calcium carbonate. The crack was initiated up to first 50% elongation along the transverse direction and the formation of air holes was originated by dewetting occurring through machine direction in the interface between calcium carbonate surface and HDPE. The propagation mechanism of the air hole formation was proposed to firstly originate by dewetting up to 300% elongation, and enlarged not only by breaking of a superimposed fibril structure, but also by merging effect air holes between fibrous resin matrix. However, the crack propagation was not observed at the very beginning elongation for the calcite filled LDPE and LLDPE systems. Less fibril structure was observed in LLDPE, then LDPE composites. The observed shape and the average size of the air holes were different from system to system. This sort of different interfacial behavior and mechanical properties may arise from different configuration of polyethylene.     

Thermoplastic composites from maleic anhydride modified post-consumer plastics

In attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co-rotating intermeshing twin-screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” applications.     

Blend of high‐density polyethylene and a linear low‐density polyethylene with compositional‐invariant mechanical properties

This article presents the tensile properties and morphological characteristics of binary blends of the high‐density polyethylene (HDPE) and a linear low‐density polyethylene (LLDPE). Two constituents were melt blended in a single‐screw extruder. Injection‐molded specimens were evaluated for their mechanical properties by employing a Universal tensile tester and the morphological characteristics evaluated by using a differential scanning calorimeter and X‐ray diffractometer. It is interesting to observe that the mechanical properties remained invariant in the 10–90% LLDPE content. More specifically, the yield and breaking stresses of these blends are around 80% of the corresponding values of HDPE. The yield elongation and elongation‐at‐break are around 65% to corresponding values of HDPE and the modulus is 50% away. Furthermore, the melting endotherms and the crystallization exotherms of these blends are singlet in nature. They cluster around the corresponding thermal traces of HDPE. This singlet characteristic in thermal traces entails cocrystallization between these two constituting components. The clustering of thermal traces of blends near HDPE meant HDPE‐type of crystallites were formed. Being nearly similar crystallites of blends to that of HDPE indicates nearness in mechanical properties are observed. The X‐ray diffraction data also corroborate these observations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2604–2608, 2002     

小型中空吹塑料的研制

采用CaCO3和HDPE对LLDPE进行改性,研究了CaCO3和HDPE用量对共混体系力学性能的影响。结果表明,当m（LLDPE）∶m（HDPE）∶m（CaCO3）=55∶30∶15时,体系的综合力学性能最好。HDPE对LLDPE具有增强增韧作用,此外,添加少量的CaCO3能显著改善共混材料的力学性能,所制得的改性材料可用于生产小型中空制品。     

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     

Melt miscibility and mechanical properties of metallocene linear low‐density polyethylene blends with high‐density polyethylene: influence of comonomer type

In this paper, the implications of melt miscibility on the thermal and mechanical properties of linear low‐density polyethylene (LLDPE)/high‐density polyethylene (HDPE) blends were assessed with respect to the influence of the comonomer type. The influence of the latter was examined by selecting one butene LLDPE and one octene LLDPE of very similar weight‐average molecular weight (M_w), molecular‐weight distribution (MWD) and branch content, keeping the comonomer type as the only primary molecular variable. Each of the two metallocene LLDPEs was melt‐blended with the same HDPE at 190 °C in a Haake melt‐blender. The rheological, thermal and mechanical properties were measured by the use of an ARES rheometer, differential scanning calorimeter and Instron machine, respectively. The rheological measurements, made over the linear viscoelastic range, suggested no significant influence of the branch type on the melt miscibility. The rheology results are in agreement with those obtained from previous transmission electron microscopy (TEM) and small‐angle neutron scattering (SANS) studies. The dynamic shear viscosity and total crystallinity of the metallocene (m)‐LLDPE blends with HDPE followed linear additivity. At small strains, the branch type has little or no influence on the melt miscibility and solid‐state properties of the blends. Even the large‐strain mechanical properties, such as tensile strength and elongation at break, were not influenced by the comonomer type. However, the ultimate tensile properties of the HDPE‐rich blends were poor. Incompatibility of the HDPE‐rich blends, as a result of the weak interfaces between the blend components, is suggested to develop at large strains. Copyright © 2005 Society of Chemical Industry     

不同密度聚乙烯共混物性质的研究

讨论了HDPE与LDPE及HDPE与LLDPE共混物的性质。研究表明共混物的力学性能、结晶度、熔点及维卡软化点都随密度ρ的变化呈规律性变化,由此总结出综合性能较好的共混物密度范围。     

Implications of melt compatibility/incompatibility on thermal and mechanical properties of metallocene and Ziegler–Natta linear low density polyethylene (LLDPE) blends with high density polyethylene (HDPE): influence of composition distribution and branch content of LLDPE

In this paper, the implications of melt compatibility on thermal and solid‐state properties of linear low density polyethylene/high density polyethylene (LLDPE/HDPE) blends were assessed with respect to the effect of composition distribution (CD) and branch content (BC). The effect of CD was studied by melt blending a metallocene (m‐LLDPE) and a Ziegler‐Natta (ZN) LLDPE with the same HDPE at 190 °C. Similarly, the effect of BC was examined. In both cases, resins were paired to study one molecular variable at a time. Thermal and solid‐state properties were measured in a differential scanning calorimeter and in an Instron mechanical testing instrument, respectively. The low‐BC m‐LLDPE (BC = 14.5 CH₃/1000 C) blends with HDPE were compatible at all compositions: rheological, thermal and some mechanical properties followed additivity rules. For incompatible high‐BC (42.0 CH₃/1000 C) m‐LLDPE‐rich blends, elongation at break and work of rupture showed synergistic effects, while modulus was lower than predictions of linear additivity. The CD of LLDPE showed no significant effect on thermal properties, elongation at break or work of rupture; however, it resulted in low moduli for ZN‐LLDPE blends with HDPE. For miscible blends, no effect for BC or CD of LLDPE was observed. The BC of LLDPE has, in general, a stronger influence on melt and solid‐state properties of blends than the CD. Copyright © 2004 Society of Chemical Industry     

Effect of the Incorporation of PVC on the Mechanical Properties of the Jute-Reinforced LLDPE Composite

Jute fabrics-reinforced linear low density polyethylene (LLDPE) matrix composites (50 wt% fiber) were prepared by compression molding and mechanical properties were studied. Polyvinyl chloride (PVC) matrix was incorporated instead of LLDPE in the jute based composites and their mechanical properties were investigated and compared with the control composites. It was found that with the increase of PVC in the LLDPE based composites, the mechanical properties were found to improve significantly. Degradation tests of the composites for upto 24 weeks were performed in soil medium. Water uptake and Thermo-mechanical properties of the composites were also studied.     

Compatibility of HDPE/postconsumer HDPE blends using compatibilizing agents

Mechanical properties, molecular weight, X‐ray diffraction, and differential scanning calorimetry (DSC) characterization of blends of virgin high‐density polyethylene (HDPE) with two types of recycled material were investigated. The recycled came from urban plastic waste; one kind was only washed and grounded and the other was extruded and pelletized to remove most of contaminant particles. Starting with the 30/70 virgin/grounded recycled and 50/50 virgin/pelletized recycled blends the recycled content was increased in both blends and compatibilizing agents were used to increase the blend performance. A mixture of phenolic antioxidants and phosphite costabilizers under the name of Recycloblend?, ethylene vinyl acetate (EVA) copolymer, low‐density polyethylene (LDPE), and linear low density polyethylene (LLDPE) were used as compatibilizers. The effect of these additives and the recycled content on the performance of extrusion blow‐molded bottles was determined. The results suggest that blends of virgin/grounded recycled and virgin/pelletized recycled HDPE, in general, were not significantly different among each other and both had a quite similar behavior than the virgin HDPE when compatibilizing agents were used. The addition of compatibilizing agents yielded a material with properties similar to those for the virgin HDPE, helping to reduce the effect of polymers degradation on the rheological and mechanical behavior, with Recycloblend and LLDPE being the most effective for the blends with grounded recycled material, and LLDPE y EVA, for the blends with pelletized recycled. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3696–3706, 2006     

Rheological and mechanical properties in polyethylene blends

Melt rheology and mechanical properties in linear low density polyethylene (LLDPE)/low density polyethylene (LDPE), LLDPE/high density polyethylene (HDPE), and HDPE/LDPE blends were investigated. All three blends were miscible in the melt, but the LLDPE/LDPE and HDPE/LDPE blends exibiled two crystallization and melting temperatures, indicating that those blends phase separated upon cooling from the melt. The melt strength of the blends increased with increasing molecular weight of the LDPE that was used. The mechanical properties of the LLDPE/LDPE blend were higher than claculated from a simple rule of mixtures, whiele those of the LLDPE/HDPE blend conformed to the rule of mixtures, but the properties of HDPE/LDPE were less than the rule of mixtures prediction.     

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.     

Recycled milk pouch and virgin low‐density polyethylene/linear low‐density polyethylene based coir fiber composites

The viability of the thermomechanical recycling of postconsumer milk pouches [a 50 : 50 low‐density polyethylene/linear low‐density polyethylene (LDPE–LLDPE) blend] and their use as polymeric matrices for coir‐fiber‐reinforced composites were investigated. The mechanical, thermal, morphological, and water absorption properties of recycled milk pouch polymer/coir fiber composites with different treated and untreated fiber contents were evaluated and compared with those of virgin LDPE–LLDPE/coir fiber composites. The water absorption of the composites measured at three different temperatures (25, 45, and 75°C) was found to follow Fickian diffusion. The mechanical properties of the composites significantly deteriorated after water absorption. The recycled polymer/coir fiber composites showed inferior mechanical performances and thermooxidative stability (oxidation induction time and oxidation temperature) in comparison with those observed for virgin polymer/fiber composites. However, a small quantity of a coupling agent (2 wt %) significantly improved all the mechanical, thermal, and moisture‐resistance properties of both types of composites. The overall mechanical performances of the composites containing recycled and virgin polymer matrices were correlated by the phase morphology, as observed with scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The use of cryogenically ground rubber tires as a filler in polyolefin blends

The effects of cryogenically ground rubber tires (CGT) on some of the mechanical properties of blends with linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) are presented. Precoating the CGT particles with an ethylene-acrylic acid copolymer is shown to overcome most of the deleterious effects of adding CGT to LLDPE, while still retaining composite processability. A blend of 40 wt% EAA coated CGT particles with LLDPE is shown to have impact and tensile strengths that are 90% of those for the pure LLDPE, representing increases of 60 and 20%, respectively, over blends with uncoated particles. Blends of LLDPE with ground tire bladders demonstrate that even better mechanical properties can be obtained with similar large rubber particle size but somewhat better adhesion. For HDPE, however, it is shown that with large rubber particles, moderate adhesion is not sufficient to produce useful composites.     

LLDPE/LDPE blends. I. Rheological,thermal, and mechanical properties

Structure and mechanical properties were studied for the binary blends of a linear low density polyethylene (LLDPE) (ethylene‐1‐hexene copolymer; density = 900 kg m⁻³) with narrow short chain branching distribution and a low density polyethylene (LDPE) which is characterized by the long chain branches. It was found by the rheological measurements that the LLDPE and the LDPE are miscible in the molten state. The steady‐state rheological properties of the blends can be predicted using oscillatory shear moduli. Furthermore, the crystallization temperature of LDPE is higher than that of the LLDPE and is found to act as a nucleating agent for the crystallization of the LLDPE. Consequently, the melting temperature, degree of crystallinity, and hardness of the blend increase rapidly with increases in the LDPE content in the blend, even though the amount of the LDPE in the blend is small. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3153–3159, 1999     

Mechanical and morphological properties of recycled high‐density polyethylene,filled with calcium carbonate and fly ash

In this study, mechanical and morphological properties of composites made up of recycled high‐density polyethylene (HDPE) filled with calcium carbonate and fly ash (FA) were studied. Interfacial interactions were modified to improve the filler compatibility and mechanical properties of the composites by surface treatment of the FA filler with 3‐amino propyl triethoxy silane. The composites were prepared by using a Thermo Haake Rheomixer. Effect of filler loading and treatment of FA with silane coupling agent on mechanical and morphological properties were investigated and it was found that silane treatment indicated significant improvements on the mechanical properties of the HDPE‐FA composites. The improvement with silane treatment of FA was also confirmed by applying the Pukanszky model. Scanning electron microscopy on the fracture surface of composites had given direct evidence of better interfacial adhesion via silane treatment. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4460–4467, 2006     

Mechanical properties and morphology of polyethylene–polypropylene blends with controlled thermal history

The effect of time–temperature treatment on the mechanical properties and morphology of polyethylene–polypropylene (PE–PP) blends was studied to establish a relationship among the thermal treatment, morphology, and mechanical properties. The experimental techniques used were polarized optical microscopy with hot‐stage, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and tensile testing. A PP homopolymer was used to blend with various PEs, including high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), linear low‐density polyethylene (LLDPE), and very low density polyethylene (VLDPE). All the blends were made at a ratio of PE:PP = 80:20. Thermal treatment was carried out at temperatures between the crystallization temperatures of PP and PEs to allow PP to crystallize first from the blends. A very diffuse PP spherulite morphology in the PE matrix was formed in partially miscible blends of LLDPE–PP even though PP was present at only 20% by mass. Droplet‐matrix structures were developed in other blends with PP as dispersed domains in a continuous PE matrix. The SEM images displayed a fibrillar structure of PP spherulite in the LLDPE–PP blends and large droplets of PP in the HDPE–PP blend. The DSC results showed that the crystallinity of PP was increased in thermally treated samples. This special time–temperature treatment improved tensile properties for all PE–PP blends by improving the adhesion between PP and PE and increasing the overall crystallinity. In particular, in the LLDPE–PP blends, tensile properties were improved enormously because of a greater increase in the interfacial adhesion induced by the diffuse spherulite and fibrillar structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1151–1164, 2000     

Influence of mixing cycle on the degree of mixing of calcite‐filled polyethylene upon stretching

The mixing cycle‐dependent degree of dispersion and degree of mixing of a calcite (calcium carbonate) agglomerate in high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), and linear low‐density polyethylene (LLDPE) matrices upon stretching was investigated using three different techniques: mechanical property, morphological behavior, and image analyzer analyses. The mechanical properties analyzed in terms of the tensile strength and maximum elongation resulted in that the second mixing was the best for giving a better property for all systems except the LDPE system, which exhibited no significant difference between the second and third mixings. The morphological behavior of the three compounds were different, but no distinctive difference was observed to differentiate the degree of mixing from system to system. The number‐, weight‐, and z + 1‐average diameters of the air hole and the aspect ratio upon the stretching and mixing cycle were calculated to analyze the degree of mixing of the calcite‐filled composites. As a consequence, no difference in the average diameter of the air hole was obtained among the three systems, but the aspect ratios of the air hole varied significantly. Thus, the degree of dispersion and the degree of mixing may be influenced by the average calcite agglomerate size, the average diameter of the air hole, and the aspect ratio upon stretching and mixing cycles. Those factors would be formed by the difference in chemical characteristics upon various microstructures of polyethylene and its molecular weight and molecular weight distribution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 311–321, 2003     

Effect of the various coupling agents on the mechanical and physical properties of thermoplastic‐bagasse fiber composites

Various types of bonding agents have been tried with blends of bagasse fibers and some thermoplastics such as low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC). These bonding agents are, namely, pentaerythritol tetracrylate (PETA), 1,6 hexandiol diacrylate (HDA), and dicumyl peroxide (DCP). In addition, a traditional coupling agents 3‐aminopropyltrimethoxy silane (AMPS) and di‐aminopropyltrimetoxy silane (DAMPS) were included for comparison. Electron beam (EB) irradiation is applied only for LDPE and HDPE at 40 and 10 kGy, respectively, before mixing with bagasse fibers. The data obtained reveal that incorporation of bonding agents remarkably increases the mechanical properties for all samples under investigation; the maximum improvement is observed in LDPE followed by HDPE, PP, PS, and PVC composites. Also, the physical properties enhanced but not at the same degree as mechanical properties. Among the tested bonding agents, it was found that PETA, DCP followed by DAMPS have highest efficiency in LDPE, whereas in case of HDPE, EB radiation was higher than PETA followed by DCP. PETA was superior in case of PS composites. Furthermore, PETA and HDA experienced higher efficiency than DAMPS and AMPS in case of PP and PVC composites. Comparison between the properties of thermoplastic composites and medium density fiberboard (MDF) reveals that most of the properties of thermoplastics composites are better than MDF. However, modulus of rupture of MDF was found to be slightly higher than thermoplastics except for PVC composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers