High Density Polyethylene Blends Research Articles

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.

The Gas Permeability of Polyolefin Blends Containing a Glass Flake Filler

The results of investigating the influence of the concentration of glass flake filler on oxygen, carbon dioxide, and water vapour permeability in composites based on high-density polyethylene blends are given.

Study on the co-pyrolysis of rice straw and high density polyethylene blends using TG-FTIR-MS

The effects of interactions between RS and HDPE on the evolution of volatile species and their distributions during co-pyrolysis of rice straw (RS) and high density polyethylene (HDPE) was investigated by thermogravimetric analyzer coupled with fourier transform infrared spectroscopy and mass spectrometry technology (TG-FTIR-MS). It can be found that the pyrolysis process of RS and HDPE blends was characterized by two stages. The first stage primarily consisted of the decomposition of RS. The second stage was dominant by the degradation of HDPE. The interactions between RS and HDPE were obvious in the temperature range of 435–520°C. The existence of HDPE delayed the decomposition of RS in the first step, while in the second step, the existence of RS delayed the degradation of HDPE. The primary gaseous products for the blends arose from the overlap of the decomposition products from the individual RS and HDPE. However, no new substance can be observed in the blends compared to the decomposition of individual RS and HDPE. The primary gaseous products were H2, H2O, CO2, CO, aldehydes (C2H4O), alcohols (C2H5OH), carboxyls (CH3COOH) and hydrocarbons (CH4, C2H2, C2H4, C2H6, C3H6, C3H8). The addition of HDPE in the blends could decrease the amount of the oxygen-containing compounds, and improve the yield of H2 and hydrocarbons. The effects of the interaction between RS and HDPE on the evolving of volatile species were affected by the percentage of RS in the blends.

Toughening high density polyethylene submitted to extreme ambient temperatures

The use of polyethylene is limited due to its low impact strength among other mechanical properties at extreme ambient temperatures, for example at −46 °C and 66 °C. In this work, different polymer components, such as ultra-high molecular weight polyethylene (UHMWPE) and ethylene-vinyl acetate (EVA), were incorporated in high density polyethylene (HDPE) to test their ability to improve toughness of HDPE at extreme ambient temperatures. The polymer blends were processed by extrusion and injection molding and characterized by rotational rheometry, electron microscopy, thermal analysis, tensile, impact and dynamic mechanical tests. The results showed that low concentrations of EVA and UHMWPE in HDPE increased substantially the impact strength of HDPE at room temperature as well as in extreme ambient temperatures (−46 °C and 66 °C). This result indicates that these HDPE blends can be considered good candidates to replace pure HDPE in applications in which high values of toughness are required at extreme ambient temperatures.

Mechanical and thermal properties of Polypropylene (iPP)-High density polyethylene (HDPE) binary blends

In this study, the mechanical and thermal properties of polypropylene (PP) and high density polyethylene (HDPE) blends in different mixture ratios are investigated. PP and HDPE 10 wt. % added blends are investigated by different tests; thermal analysis such as; melting temperature, crystalline temperature, crystalline energy, involved crystalline ratio, mechanical properties such as; Tensile strength at break, at yield and elongation at break) fitness and the impact resistance. PP and HDPE polymers are semi-crystalline, involving crystalline ratio for PP and HDPE 2.08 to 38.44 % and 4.66 to 62.80 respectively. For these homopolymer’s crystalline phase and blends have two melting points, but they have only one crystalline temperature. The degree of melting and crystalline of blends is not different from the values of PP and HDPE. The tensile strength at the point of flow and breaking point are not varied according to the original homopolymer but the properties of strain at the breaking point are much weakened. Moreover, polymer blends at the value of non-bending, when the comparison make with the homopolymer, an improvement can observed 2.6 % by the increased ratio of HDPE and also the impact properties of the PP can be improved by adding more than 70 wt. % HDPE in to the PP.

Strain Hardening of Polyethylene/Polypropylene Blends via Interfacial Reinforcement with Poly(ethylene-cb-propylene) Comb Block Copolymers

A poly(ethylene-cb-propylene) comb block copolymer (P(E-cb-P)), prepared by copolymerization of vinyl-terminated atactic polypropylene and ethylene, was used to compatibilize immiscible blends of high-density polyethylene (HDPE) and isotactic polypropylene (iPP). Addition of 5 wt % P(E-cb-P) resulted in 5-fold microdomain size reductions and the concomitant increase in the elastic modulus, as typically observed in immiscible blends compatibilized with linear block copolymers. We report an unexpected phenomenon, namely, the development of extensional flow hardening by the addition of P(E-cb-P) to the HDPE/iPP blends. This unprecedented effect is stronger in blends with cocontinuous morphology (50/50 HDPE/iPP) than in blends with matrix-droplet morphology (75/25 or 25/75 HDPE/iPP). We postulate that the melt strength enhancement and extensional strain hardening observed in the compatibilized blends may arise from the interfacial stiffening as a result of the interfacial stitching by the P(E-cb-P) comb block...

Detailed comparison of compatibilizers MAPE and SEBS-g-MA on the mechanical/thermal properties, and morphology in ternary blend of recycled PET/HDPE/MAPE and recycled PET/HDPE/SEBS-g-MA

In this study, for recycling polyethylene terephthalate, a blend of recycled polyethylene terephthalate (RPET) and high-density polyethylene (HDPE) with maleic anhydride polyethylene (MAPE) and maleic anhydride-grafted styrene–ethylene/butylene–styrene (SEBS-g-MA) were used. The effect of compatibilizers in RPET was investigated by mechanical test (tensile and flexural tests), thermal test (differential scanning calorimetry (DSC)), and melt flow index test. The morphology of fracture surface of samples was investigated by scanning electron microscopy (SEM). The mechanical tests showed that elongation at break point and the fracture energy of samples with composition of RPET (70 wt%)/HDPE (15 wt%)/MAPE (15 wt%) and RPET (75 wt%)/HDPE (10 wt%)/SEBS-g-MA (15 wt%) increased significantly. Results of DSC test and SEM photography showed that ternary blend of RPET/HDPE/MAPE has better compatibility compared with RPET/HDPE/SEBS-g-MA. SEM images showed that MAPE provides better bonding between RPET and HDPE compared with SEBS-g-MA. MAPE was dispersed in RPET better than SEBS-g-MA.

Crystal Structure Evolution of UHMWPE/HDPE Blend Fibers Prepared by Melt Spinning.

Ultra-high molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) blend fibers with the highest tensile strength of 1.13 GPa were prepared by a melt spinning process. The mechanical behavior and crystal structure of the as-spun filaments and fibers were studied by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD), sound velocity orientation testing, and tensile testing. The orientation degree, crystallinity, tensile strength, and initial modulus of the fibers increased with the increasing of the draw ratios. The grain size was shortened in the radial direction and elongated in the axial direction. The results suggested that the improvement of the tensile strength and initial modulus was a result of the compact crystal structure formed by slender grains composed of highly oriented molecular chains. Blending with HDPE could improve the formation of a slender and compact crystal structure, and the tensile strength and initial modulus of the blend fibers were higher.

Conceptualizing Physical and Chemical Interactions in the Compatibilized HDPE/PA6 and HDPE/EVOH Pairs: Theoretical and Experimental Analyses

ABSTRACTPhysical/chemical interaction in blends of high-density polyethylene with polyamide 6 and polyethylene-co-vinyl alcohol compatibilized with maleic anhydride-grafted high-density polyethylene was discussed. The performance of maleic anhydride-grafted high-density polyethylene was assessed by domain size variation and interfacial adhesion examination. Analysis of impact strength elucidated physical interaction improvement by compatibilization (entanglements and hydrogen bonding), while chemical reactions between ‒OH and ‒NH (from polyethylene-co-vinyl alcohol and polyamide 6, respectively) and ‒COOH functional groups resulting from ring-opening of maleic anhydride determined interfacial adhesion reinforcement, where interfacial adhesion parameter changed from 0.75 for noncompatibilized to 0.96 compatibilized high-density polyethylene/polyamide 6, but remained unchanged for high-density polyethylene/polyethylene-co-vinyl alcohol blends, from 0.98 to 1.02.

Effect of UHMWPE Incorporation on Microstructural and Mechanical Responses of HDPE Matrix

<span>Binary blends of High density Polyethylene (HDPE) / Ultra high molecular weight polyethylene (UHMWPE) were prepared using Twin Screw Extruder (TSE). The blends were then Injection molded and analyzed for their thermal, mechanical and morphological characteristics. Differential scanning calorimetry (DSC) analyses showed an increase in melting temperature, while other properties such as crystallization temperature and percentage crystallinity were unaffected. Investigated HDPE/UHMWPE blends showed improvement in tensile, impact and flexural properties with UHMWPE content. However, strain at break suffered a decrease. Scanning electron microscopy (SEM) of cryo-fractured surface (Samples fractured after dipping in liquid nitrogen) revealed distinct two-phase morphology for such blends. SEM analyses of tensile fractured surfaces facilitated in qualitatively understanding the underlying failure mechanisms. </span>

Assessing the use of binary blends of acrylonitrile butadiene styrene and post-consumer high density polyethylene in fused filament fabrication

Several experiments were conducted to assess the suitability of binary blends of recycled high-density polyethylene and virgin acrylonitrile butadiene styrene for use in fused filament fabrication. Binary blends of the two plastics were extruded into feedstock for a 3D printer in varying proportions. Filament extrusion consistency, dimensional accuracy of 3D printed benchmarking objects, and tensile strength were each assessed. When compared against commercial acrylonitrile butadiene styrene filament, binary blends of recycled high-density polyethylene and acrylonitrile butadiene styrene were found to have inferior filament extrusion consistency and tensile strength. They also produced less accurate benchmarking objects. Despite this, binary blends were shown to produce objects with dimensional accuracy and tensile strength that would render them suitable for many applications.

Assessing the use of binary blends of acrylonitrile butadiene styrene and post-consumer high density polyethylene in fused filament fabrication

Several experiments were conducted to assess the suitability of binary blends of recycled high-density polyethylene and virgin acrylonitrile butadiene styrene for use in fused filament fabrication. Binary blends of the two plastics were extruded into feedstock for a 3D printer in varying proportions. Filament extrusion consistency, dimensional accuracy of 3D printed benchmarking objects, and tensile strength were each assessed. When compared against commercial acrylonitrile butadiene styrene filament, binary blends of recycled high-density polyethylene and acrylonitrile butadiene styrene were found to have inferior filament extrusion consistency and tensile strength. They also produced less accurate benchmarking objects. Despite this, binary blends were shown to produce objects with dimensional accuracy and tensile strength that would render them suitable for many applications.

Two-step positive temperature coefficient effect with favorable reproducibility achieved by specific “island-bridge” electrical conductive networks in HDPE/PVDF/CNF composite

Distinct “island-bridge” structure was purposely designed by appointing carbon nanofiber (CNF) filled high density polyethylene (HDPE) and polyvinylidene fluoride (PVDF) blend, in which, very dense electrical conductive networks were formed in HDPE dispersion phase (islands) and these islands were then linked by CNF particles partly stretched out from HDPE phase or distributed in PVDF phase (bridges). The HDPE/PVDF/CNF composites with “island-bridge” electrical conductive network showed unique positive temperature coefficient (PTC) effect, namely, a two-step PTC effect companied extremely favorable PTC reproducibility. The first sharp increase and the second increase of resistivity could be attributed to the sequential volume expansion of HDPE and PVDF at their melting point, where the electrical conductive networks were broken twice. In addition, the existence of dense electrical conductive networks in HDPE phase and the additional compression on them by the volume shrinkage of PVDF phase during the cooling process resulted in the favorable PTC reproducibility.

Influence of triallyl cyanurate as co-agent on gamma irradiation cured high density polyethylene/reclaimed tire rubber blend

Utilization of waste from tire industry as reclaimed tire rubber (RTR) by formation of blends with high density polyethylene (HDPE) is great area to be focused. Enhancement of properties by the addition of triallyl cyanurate (TAC) as a co-agent with 1%, 3% and 5% to blend of HDPE 50wt% and RTR 50wt% in presence of gamma irradiation curing were investigated. Specifically, mechanical and thermal properties were studied as a function of amount of TAC and gamma irradiation dose in range of 50–200 kGy. The resultant blends were evaluated for the values of impact strength, gel content, thermal stability, tensile properties, rheological properties and morphological properties with increasing irradiation dosage and TAC loading. The mechanical properties tensile strength, hardness, impact strength of blend containing 3% of TAC were substantially increased with increasing irradiation dosage up to 150 KGy. Rheological analysis has shown increase in viscosity with increase in TAC loading up to 3% and 150 KGy irradiation dosages. 3% loading of TAC lead to better set of properties with150 KGy gamma irradiation dosage.

Thermal, Rheological, Mechanical and Morphological Behavior of High Density Polyethylene and Carboxymethyl Cellulose Blend

In this study water soluble sodium carboxymethyl cellulose (CMC) was blended with high density polyethylene (HDPE) by peroxide-initiated melt compounding technique. The compatibility of the blended polymers were carried out by silane crosslinking agent. A series of blends were prepared by varying the CMC contents up to a maximum of 50 phr. The physical properties of non-crosslinked and crosslinked blends were investigated in detail. FTIR analysis of crosslinked blend confirmed the presence of Si–O–Si and Si–O–C absorption peaks at 1050 and 1159 cm−1. Thermal stability of crosslinked blends improved as compared to its non-crosslinked congener. Rheological study of crosslinked blends illustrated high complex viscosity and dynamic shear storage modulus. The tensile strength of virgin polyethylene was 8.1 MPa whereas the maximum tensile strength of 19.6 MPa was observed in crosslinked blend. Similarly lower deformation was observed in crosslinked blends under static load. Scanning electron microscopy of crosslinked formulations also showed strong adhesion between the polymers interface. The compatibility of HDPE and CMC is attributed to both free radical and condensation reactions.

Bimodal poly(ethylene-cb-propylene) comb block copolymers from serial reactors: Synthesis and applications as processability additives and blend compatibilizers

Abstract Two solution reactors in series are utilized to synthesize poly(ethylene-cb-propylene) comb block copolymers, P(E-cb-P), where the first reactor prepares vinyl terminated atactic polypropylene (aPP) macromers from propylene using an organometallic catalyst favoring beta methyl elimination and the second reactor copolymerizes aPP macromers with ethylene using a different organometallic catalyst capable of incorporating macromers. The products are P(E-cb-P) comb block polymers with bimodalities in molecular weight, composition, and long chain branching. Low molecular weight (MW) components are linear and of mixed compositions consisting of random copolymers of ethylene and propylene and residual vinyl terminated aPP macromers. High MW components are comb branched with constant composition, and block copolymers. Even though the PE backbone is immiscible with the aPP comb arms, the presence of linear low MW ethylene-propylene random copolymer prevents the high MW comb block components from self-association into segregated domains or micelles when it is blended into high density polyethylene (HDPE) or isotactic polypropylene (iPP). By hindering micelle formation, this bimodal P(E-cb-P) can be intimately entangled with HDPE and with iPP delivering extensional flow hardening when it was added at 5%. Extensional strain hardening is observed at 5% addition of the bimodal P(E-cb-P) comb block copolymer in 50/50 HDPE/iPP blends with exceptionally high strain hardening ratio. It was found that this bimodal P(E-cb-P) comb block copolymer can compatibilize immiscible blends of HDPE and iPP resulting in domain size reductions and diffused interfaces. The enhanced strain hardening observed in blends with the bimodal P(E-cb-P) comb block addition may arise from the increases in the blend interfacial area and the entanglement of the blocks within the homopolymer phases.

Morphology and properties of bio-based poly (lactic acid)/high-density polyethylene blends and their glass fiber reinforced composites

Poly (lactic acid) (PLA)/high-density polyethylene (HDPE) blends of various proportions and their glass fiber reinforced composites were prepared by melt-compounding. The miscibility, phase morphology, thermal behavior and mechanical properties of the blends were investigated. The blends were immiscible systems with two typical morphologies, spherical droplet and co-continuous, and could be obtained at various compositions. Water contact angle and SEM images indicated that PLA and HDPE are immiscible but can be successfully compatibilized by ethylene-butyl acrylate-glycidyl methacrylate (PTW). Thermal degradation of all blends led to two weight losses, for PLA and HDPE. The incorporation of HDPE improved the thermal stability of the blend. With the addition of 5 wt% PTW, the impact strength of PLA/HDPE/PTW blends (60/40/5 w/w/w) is increased to 18.0 kJ/m2. The effect of glass fiber (GF) on the morphology and mechanical properties of PLA/HDPE/PTW blends (60/40/5 w/w/w) was also investigated. The addition of GF improved the thermal stability of the PLA/HDPE/PTW blends to some extent. The tensile strength of these blends increased and impact strength decreased with increasing GF content.

Compatibility and epitaxial crystallization between Poly(ethylene) and Poly(ethylene)-like polyesters

This work describes the phase behavior of blends of ‘polyethylene-like’ polypentadecalactone (PPDL) and polyethylene. Blends of high-density polyethylene (HDPE) and PPDL were shown to be immiscible at the onset of crystallization of polyethylene, resulting in phase-separated morphologies. However, epitaxial crystallization of PPDL onto the HDPE crystals was observed by transmission electron microscopy (TEM), resulting in lamellae penetrating through the interface of the two polymers. Furthermore, PPDL/low-density polyethylene (LDPE) blends were produced and used for film extrusion, yielding clear films with good optical properties, despite the presence of fully phase-separated morphology. For PPDL-rich blends, TEM analysis revealed the formation of highly elongated crystalline domains of LDPE, from which the PPDL domains were epitaxially crystallized yielding a shish-kebab type of morphology. In these structures, the extended LDPE domains formed shishes with LDPE micro-kebabs, onto which PPDL macro-kebabs crystallized. The shish-kebab morphology was furthermore confirmed using x-ray analysis. The high aspect ratio of the LDPE domains is caused by the long relaxation times of LDPE in combination with the low interfacial tension between LDPE and PPDL. As a consequence of the lower relaxation time of PPDL (due to the linear chain architecture), the PPDL domains in the LDPE-rich blends have a lower aspect ratio. The strong epitaxial crystallization in combination with anisotropy in the morphology has a positive effect on the optical properties of the films.

Determination of thermal and mechanical properties of HDPE-based polymer blends for use in traffic signs

Two recycled high-density polyethylene specimens and two recycled high-density polyethylene blends were characterized in terms of their thermal and mechanical properties with the purpose of assessing their suitability for the construction of traffic signs. Traffic signs constructed from recycled plastics provide an application for materials that otherwise with end up in landfills. The HDPE composite containing 25% LDPE and 5% ABS had the best mechanical and thermal performance. Of importance is the recycling of ABS that traditionally had not been recycled locally and found its final fate in landfills.

Fracture characterization of recycled high density polyethylene/nanoclay composites using the essential work of fracture concept

The effect of nanoclay on the plane-strain fracture behavior of pristine High density polyethylene (HDPE) and recycled HDPE blends was studied using the essential work of fracture (EWF) concept. The failure mode of EWF tested specimens was found to be associated with the specific non-EWF (βBwp,B). Adding 6-wt% of nanoclay to pristine HDPE and 2-wt% to recycle-blends greatly decreased the βBwp,B values and led to a transition from ductile to brittle failure mode. A fractographic study revealed that the difference in failure modes was caused by the changes in micro and macro morphologies, which could be related with the specific EWF (we,B). In the ductile failure, we,B is governed by the fibril size; adding nanoclay and recycled HDPE to pristine HDPE decreased the fibril size and subsequently lowered the we,B value. In the brittle failure, the we,B value was enhanced by creating a rough fracture surface. Adding nanoclay to pristine HDPE, a steadily decrease in we,B was measured until 4-wt% after which the change was insignificant. Conversely, nanoclay content more than 2-wt% in recycle-blends greatly decreased the we,B value. A transition map was constructed to illustrate the potential failure mode and the associated fracture morphology based on the tested material compositions. POLYM. ENG. SCI., 56:222–232, 2016. © 2015 Society of Plastics Engineers