Neat High Density Polyethylene Research Articles

Effect of entangled state of nascent UHMWPE on structural and mechanical properties of HDPE/UHMWPE blends

ABSTRACTIn this study, a synthesized ultra‐high molecular weight polyethylene (UHMWPE) with a less entangled state and a commercial UHMWPE with a highly entangled state were blended with high‐density polyethylene (HDPE) by melt blending, respectively. Rheology, 2D small‐angle X‐ray scattering (2D‐SAXS), differential scanning calorimetry (DSC), and tensile test were used to study the relationship between the microstructure and the mechanical properties of blends. It was demonstrated that the UHMWPE with the less entangled state was easy to be oriented at a given flow. More mechanical networks were achieved among the HDPE matrix and the UHMWPE chains due to the fewer entanglements of synthesized UHMWPE, improving the melting recovery of blends. Furthermore, notably oriented structures (shish‐kebabs) with increased long‐periods were made in the blends of weakly entangled UHMWPE and HDPE. The tensile strength of this blend was thus enhanced, i.e., the tensile strength raised for neat HDPE from 45.7 to 83.1 MPa for HDPE/UHMWPE blends containing 10 wt % of less entangled UHMWPE. However, the phase separation of blends was characterized when more weakly entangled UHMWPE was incorporated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44728.

Nanoclay reinforced polyethylene composites: Effect of different melt compounding methods

Nanoclay (NC) reinforced high‐density polyethylene (HDPE) composites were prepared by different melt compounding methods using (1) a single screw extruder (SSE), (2) twin screw extruder (TSE), (3) a combination of SSE and extensional flow mixer (EFM), and (4) a bowl mixer masterbatch method (MB). PE‐grafted maleic anhydride (PE‐g‐MA) was used as a compatibilizer. EFM increased complex melt viscosity (η*) of the HDPE/NC composites as compared to the neat HDPE and also provided a better interaction between HDPE and NC to create slightly lower melt η* as compared to MB and PE‐g‐MA composites. The low viscosity melt behavior of the pure HDPE changes to more solid like melt behavior in the PE‐g‐MA HDPE/NC composites in the low frequency (ω) region. PE‐g‐MA + EFM method exhibited better impact strength compared to the other HDPE/NC composites. Using the PE‐g‐MA and masterbatch compounding methods had a beneficial role in improving mechanical properties. POLYM. ENG. SCI., 57:324–334, 2017. © 2016 Society of Plastics Engineers

Determination of the mechanical, thermal and physical properties of nano-CaCO3 filled high-density polyethylene nanocomposites produced in an industrial scale

The objective of this study is to examine the mechanical, thermal, and physical properties of industrially produced nano-CaCO3 filled high-density polyethylene nanocomposites. For this purpose, 1.0, 3.0, 5.0, 10.0, and 15.0 wt.% loading of nano-CaCO3 filled high-density polyethylene nanocomposites were prepared by the melt mixing method using a compounder system, which consist of industrial banbury mixer, single screw extruder, and granule cutting. The effect of nano-CaCO3 on mechanical, thermal, and physical properties of nano-CaCO3/HDPE nanocomposites was investigated. As a result of all experiments, the tensile strength of nano-CaCO3 filled high-density polyethylene nanocomposite increased about 5% with addition of 1.0 wt.% nano-CaCO3. But did not increase further as more nano-CaCO3 was added. The flexural strength of nano-CaCO3 filled high-density polyethylene nanocomposite increased about 4.5% with addition of 15.0 wt.% nano-CaCO3.Then increased slightly as the nano-CaCO3 content increased to 15.0 wt.%. The tensile and flexural modulus of high-density polyethylene were significantly improved after (from 1.0 wt.% up to 15.0 wt.%) addition of nano-CaCO3. The tensile elongation at break and shore D hardness was consistently decreased with the addition of nano-CaCO3. The nano-CaCO3 filled high-density polyethylene nanocomposites were determined to have lower impact energy level than neat high-density polyethylene. The occurred fracture areas with the impact were detected by scanning electron microscopy examination. It is understood that fracture surface morphology changes when nano-CaCO3 ratio increases. The fracture surface changes were examined to determine the fracture mechanism of nano-CaCO3 filled high-density polyethylene nanocomposites. Density, melting flow index, differential scanning colorimetry, and vicat softening temperature were used to characterize the physical and thermal properties of the nanocomposites. The X-ray diffraction, the fourier transform infrared spectrophotometry, the transmission electron microscopy, and the scanning electron microscopy were used to analyze the structural characteristics of the nanocomposites. It is concluded that the addition of the nano-CaCO3 in high-density polyethylene has significantly influenced the mechanical, thermal, and physical properties of the nanocomposites.

Studies on High Density Polyethylene Reinforced with Phosphate Ore Particles: Thermal, Rheological, Mechanical and Morphological Properties

ABSTRACTCalcareous phosphate ore can be utilized as a cost-effective alternate to other inorganic fillers for polymer-based composites. In this study, composites of high-density polyethylene and phosphate rock ore particles were prepared by melt blending and injection-molding techniques. The thermomechanical, rheological, and mechanical properties of these composites were studied to investigate the effect of filler loading on their functionality. The reduction in the crystallinity of phosphate ore/high-density polyethylene composites was observed compared to that of the neat high-density polyethylene. The relative crystallinity of the neat high-density polyethylene decreases from 53 to 30% by the addition of 2.5–15 wt% of ore, respectively. Comparison of the linear dynamic viscoelasticity for the neat high-density polyethylene and the ore-filled composites shows t a monotonic increase in both storage modulus and loss modulus with the increasing frequency. The viscoelastic behavior at high frequencies remains unaffected. However, at lower frequencies, both G′ and G″ exhibit diminished frequency dependence. It was also observed that higher filler content decreased the tensile and impact strength, whereas the Young's modulus of the composites increased. The morphological analysis shows relatively weak interaction between the fillers and the matrix because of agglomeration which in turn adversely affects the mechanical properties of the composites.

Thermal degradation kinetics and lifetime of HDPE/PLLA/pro-oxidant blends

Abstract The effect of adding poly(L-lactic acid) (PLLA) with and without a pro-oxidant additive cobalt stearate (CoSt) and compatibilizer maleic anhydride grafted polyethylene (MA-g-PE) on the thermal degradation and stability of high-density polyethylene (HDPE) films was analyzed using thermogravimetric analysis (TGA). The kinetic parameters [i.e. activation energy (E a), order of reaction (n), and frequency factor ln(A)] of the samples were studied over a temperature range of 25°C–600°C at four heating rates (i.e. 5, 10, 15, and 20°C/min) through model-free techniques (e.g. Friedman, second Kissinger, and Flynn-Wall-Ozawa) and model-fitting techniques (e.g. Freeman-Carroll and Kim-Park). The value of E a for neat HDPE was found to be much higher than PLLA; for the HDPE/PLLA blend, it was nearer to that of HDPE. An increase in the activation energy of 80/20 (HDPE/PLLA) blend was noticed by the addition of MA-g-PE. The TGA data and degradation kinetics were also used to predict the lifetime of the film samples. The lifetime of HDPE was found to decrease with the increase in the concentration of CoSt, thereby revealing its pro-oxidative ability. Minimum lifetime was noted for the HDPE/PLLA (80/20) sample blended with CoSt, which increased slightly in the presence of MA-g-PE. Studies indicated that the thermal degradation behavior and lifetime of the investigated film samples depends not only on the fractions of their constituents but also on the heating rates and calculation technique.

Manufacturing and characterization of vine stem reinforced high density polyethylene composites

Abstract Vine stem is an agricultural side product and has limited economic value. Alternative uses of such agricultural powder into value-added products such as thermoplastic composites can provide remarkable environmental and economic benefits. Vine stem filler may be used as a potential reinforcement in polymeric materials. In this study, vine stem reinforced high density polyethylene (HDPE) composite materials were manufactured and characterized. Agricultural waste of vine stem was collected from Manisa region, Turkey. Vine stem was ground in a grinder and thereby turning into the powder form. Composites were obtained using twin screw extruder by adding different amounts of vine stem powder (5, 10 and 20% wt.) into HDPE. Mechanical, thermal, water absorption and crystallographic properties of waste vine stem reinforced HDPE composites were investigated. HDPE containing 10% waste vine stem exhibited the highest tensile strength and flexural strength. Vine stem powder addition into HDPE delayed the thermal decomposition of HDPE. DMA analyses showed that the storage modulus values of reinforced HDPE are higher than neat HDPE throughout the whole temperature scale.

Synthesis and Non-Isothermal Crystallization Behaviors of Maleic Anhydride onto High Density Polyethylene

The grafting reaction for maleic anhydride (MA) onto high density polyethylene (HDPE) was investigated from solution process with initiators. The chemical modification of neat HDPE was carried out with various contents of MA (3-21 wt.%) and initiator (0.2-1 wt.%) at different temperature (80-130℃). The grafting degree was obtained from the titration and the highest grafting degree was 3.1%. The grafting degree increased as the content of MA and initiator increased, however, the highest grafting degree was demonstrated for a particular content of MA and initiator. In the non-isothermal crystallization kinetics, the Ozawa model was unsuitable method to investigate the crystallization behavior of MA onto HDPE, whereas the Avrami and Liu models found effective. The crystallization rate was accelerated as the cooling rate increased, but postponed by combination of MA onto neat HDPE backbone.

The effect of Poly-ethylene-co-glycidyl methacrylate efficiency and clay platelets on thermal and rheological properties of wood polyethylene composites.

Global ecological concerns have resulted in an interest in renewable natural materials. Composites based on high density polyethylene (HDPE), wood fiber (Veneer) and containing coupling agents like nanoclay (NC) and poly-ethylene-co-glycidyl methacrylate (PEGMA) were made by melt compounding and then injection molding. In this study, the effects of two variable parameters namely nanoclay and coupling agent on the rheological and thermal properties of wood polyethylene composites (WPECs) were investigated. The study investigates the morphology phase, rheology behaviors and thermal properties by scanning electron microscope, capillary rheometer and thermal gravimetric analyzer. The SEM micrographs of the composites showed that the outer surfaces of the wood were coated by a section of amorphous lignin. The state of dispersion in HDPE/pine/clay composites was improved by EGMA because it could interact with pine flour in addition to clay. The interaction of reinforcement with coupling agent and HDPE matrix is strong based on the observation of the fracture surface of composites when EGMA is present. However the addition of 2.5% clay slightly lowered the initial degradation temperature (Td) but did not improve the thermal stability. Obviously, all the composites materials exhibit viscoelastic values greater than those of neat HDPE.

Thermal degradation kinetics and lifetime of high-density polyethylene/poly (l-lactic acid) blends

In this work, a kinetic study on the thermal degradation of films prepared from high-density polyethylene (HDPE), poly(l-lactic acid) (PLLA) and their blends is presented. Activation energy ( Ea), order of reaction ( n) and frequency factor (ln ( A)) were studied through thermogravimetric analysis (TGA) over a temperature range of 25–600°C at four heating rates, that is, 5, 10, 15, and 20°C min−1. The TGA data were used to predict the thermal stability of the film samples, comparing the kinetic parameters obtained by three model-free isoconversional techniques and estimating the lifetime of the films. The value of Ea for neat HDPE was found to be much higher than that for PLLA, but for HDPE/PLLA blends, it was nearer to that of HDPE. An increase in Ea of 80/20 (HDPE/PLLA) blends was noticed with the addition of compatibilizer, maleic anhydride-grafted HDPE. Overall, the thermal kinetics of the polymer samples depends on fractions of their constituents, heating rates and calculation technique used. It was proved, through lifetime estimation method, that the lifetime of neat HDPE decreases by addition of PLLA. With increase in temperature, the lifetime of all samples decreased exponentially. Scanning electron microscopy studies verified that HDPE and PLLA interfaces became fairly compatible by adding the compatibilizer.

Insert injection molding of high‐density polyethylene single‐polymer composites

A process for making high‐density polyethylene (HDPE) single‐polymer composites (SPCs) by insert injection molding was investigated. HDPE SPCs with relatively good tensile and interfacial properties were prepared within a short cycle time within a temperature range of 40°C. Melt‐spun HDPE fibers were made from the same resin as the matrix. The fibers were heat treated in silicone oil, with and without tension, to study the changes of fiber properties upon exposure to high temperature. HDPE SPCs containing about 30 wt% lab‐made HDPE fabric achieved a tensile strength of 50 MPa, 2.8 times that of neat HDPE. The peel strength of HDPE SPCs increased with increasing injection temperature and achieved a maximum value of 16.7 N/cm. Optical micrographs of polished transverse cross‐sections of the SPC samples showed that higher injection temperature is beneficial to the wetting and permeation properties of the matrix. Scanning electronic microscope photographs suggested good bonding and compatibility between the fibers and the matrix. POLYM. ENG. SCI., 55:2448–2456, 2015. © 2015 Society of Plastics Engineers

Thermal, physico‐mechanical, and morphological properties of HDPE graft‐copolymerized with polystyrene

In this study, polystyrene was graft‐copolymerized onto high‐density polyethylene (HDPE) by in situ polymerization of styrene monomer to change the physico‐mechanical and thermal properties of HDPE. The grafting was carried out in a Brabender‐type static mixer by injecting styrene monomer directly into the molten HDPE in the presence of a free‐radical initiator (lauroyl peroxide or LP). The effect of wt% of styrene and initiator concentrations on thermal, physico‐mechanical, and morphological properties of HDPE was investigated. The neat and modified HDPE was characterized by differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and also by tensile strength and contact angle measurements. It was found that the increase in wt% of styrene and LP dosage reduced elongation at break, hygroscopic expansion and also the melting, and the crystallization temperatures of HDPE but increased its tensile strength. The tensile strength was increased from 14.6 MPa for the neat HDPE to 20.6 MPA for the 10 wt% of styrene grafted onto HDPE using 0.8% LP. Scanning electron microscopy results show that there was no phase separation, and the grafted polystyrene became integral part of HDPE. The results demonstrate that styrene could be used in melt compounding to improve various properties of HDPE. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of confinement on glass dynamics and free volume in immiscible polystyrene/high‐density polyethylene blends

AbstractThe effect of confinement on glass dynamics combined with the corresponding free volume changes of amorphous polystyrene (PS) in blends with semi‐crystalline high‐density polyethylene (HDPE) have been investigated using thermal analyses and positron annihilation lifetime spectroscopy (PALS). Two different glass transition temperatures (Tg) were observed in a PS/HDPE blend due to the dissimilarity in the chemical structure, consistent with an immiscible blend. However, Tg of PS in the incompatible PS/HDPE blend showed an upward trend with increasing PS content resulting from the confinement effect, while Tg of the semi‐crystalline HDPE component became lower than that of neat HDPE. Moreover, the elevation of Tg of PS was enhanced with a decrease of free volume radius by comparing annealed and unannealed PS/HDPE blends. Positron results showed that the free volume radius clearly decreased with annealing for all compositions, although the free volume hole size agreed well with linear additivity, indicating that there was only a weak interaction between the two components. Combining PALS with thermal analysis results, the confinement effect on the glass dynamics and free volume of PS phase in PS/HDPE blends could be attributed to the shrinkage of HDPE during crystallization when HDPE acted as the continuous phase. © 2015 Society of Chemical Industry

Enhanced dispersion of carbon nanotubes in high density polyethylene matrix using secondary nanofiller and compatibilizer

In this study, we have attempted to explain the influence of secondary filler on the dispersion of carbon nanotube (CNT) reinforced high density polyethylene (HDPE) nanocomposites (CNT/HDPE). In order to understand the mixed-fillers system, Montmorillonite (MMT) in addition with Maleic anhydride grafted high density polyethylene (PE-g-MA) was added to CNT/HDPE nanocomposites. It was followed by investigating their effect on the thermo-mechanical, rheological and morphological properties of the aforesaid nanocomposite. Incorporation of 3 wt% each of MMT and PE-g-MA into CNT/HDPE nanocomposites resulted to the increased values for the tensile and flexural strength (32 % increase in both), as compared to the pure HDPE matrix. The thermal analysis result showed improved thermal stability of the formulated nanocomposites. The initial decomposition temperature (T i ) for such nanocomposite with 9 wt% of MMT and 3 wt% of PE-g-MA reached to 296 °C from 265 °C (T i for neat HDPE matrix). Addition of MMT to CNT/HDPE nanocomposites also increased the rheological properties indicating a dominating elastic response. A significant increase in loss, storage modulus and complex viscosity was observed upon addition of PE-g-MA, whereas Tan δ was found to be reduced. This might be due to better interfacial adhesion between MMT and HDPE phases that attributes to the elastic dominance. Improvement in dispersion of CNT upon addition of MMT and PE-g-MA was further supported by the morphological analysis. Transmission electron microscopy (TEM) images revealed that larger aggregates of CNTs were disappeared upon addition of these two components leading to the enhancement of thermo-mechanical properties for such composites.

Ionic Liquid-Facilitated Preparation of Lignocellulosic Composites

Lignocellulosic composites (LCs) were prepared by partially dissolving cotton along with steam exploded Aspen wood and burlap fabric reinforcements utilizing an ionic liquid (IL) solvent. Two methods of preparation were employed. In the first method, a controlled amount of IL was added to preassembled dry matrix of cotton and Aspen wood with a burlap weave reinforcement. In the second method, IL solvent, cotton, and Aspen wood were mixed to produce a thick paste matrix that was subsequently pressed into the burlap weave reinforcement. The IL-based solvent was removed via water soaking, and the flexural and tensile properties of the LCs were examined. In this study, the matrix paste method produced a superior LC. Variables such as processing time (IL interaction time) and fabric weaves were found to influence the mechanical properties of the LCs. Although significant process optimization can still be realized, the mechanical properties of several of the LCs fabricated in this study were comparable to injection molded test specimens of neat high density polyethylene or neat polypropylene.

High-Density Polyethylene and Heat-Treated Bamboo Fiber Composites: Nonisothermal Crystallization Properties

The effect of heat-treated bamboo fibers (BFs) on nonisothermal crystallization of high-density polyethylene (HDPE) was investigated using differential scanning calorimetry under nitrogen. The Avrami-Jeziorny model was used to fit the measured crystallization data of the HDPE/BF composites and to obtain the model parameters for the crystallization process. The heat flow curves of neat HDPE and HDPE/heat-treated BF composites showed similar trends. Their crystallization mostly occurred within a temperature range between 379 K and 399 K, where HDPE turned from the liquid phase into the crystalline phase. Values of the Avrami exponent (n) were in the range of 2.8~3.38. Lamellae of neat HDPE and their composites grew in a three-dimensional manner, which increased with increased heat-treatment temperature and could be attributed to the improved ability of heterogeneous nucleation and crystallization completeness. The values of the modified kinetic rate constant (KJ) first increased and then decreased with increased cooling rate because the supercooling was improved by the increased number of nucleating sites. Heat-treated BF and/or a coupling agent could act as a nucleator for the crystallization of HDPE.

Vinyl acetate-modified microcrystalline cellulose-reinforced HDPE compositesprepared by twin-screw extrusion

In order to compare the effects of microcrystalline cellulose (MCC) as a filler, MCC and high-density polyethylene (HDPE) composites were produced with 4 different wt.% MCC loadings (1 wt.%, 5 wt.%, 10 wt.%, and 20 wt.%). To improve the compatibility between MCC and the matrix, MCC was acetylated with vinyl acetate (VA), and 2 different MCC-HDPE composites were produced with 5 wt.% and 10 wt.% VA-modified MCC loadings. Untreated MCC and VA-modified MCC-reinforced HDPE pellets were produced by using a twin-screw extruder. The MCC-HDPE composites were then compression-molded and the mechanical properties of the composites were determined. The thermal and morphological properties of the MCC-HDPE composites were characterized by using thermogravimetric and electron microscopy techniques, respectively. The VA-modified MCC-filled HDPE had a significantly higher tensile strength than the unmodified MCC-filled or the neat HDPE composites. The thermal stability of MCC was also improved with VA modification.

Development and characterization of post-consumer rubber tire powder, high density polyethylene and ethylene-octene-1copolymer ternary mixtures

Scrap tires are considered a type of waste that litters landfills and the environment in general. Due to its chemically cross-linked structure, this material cannot be recycled by conventional processes because it does not melt. This work examined the production of polymeric composites using high density polyethylene (HDPE) filled with rubber tire powder (RTP). Ethylene-octene-1 copolymer (C2C8), an elastomeric material, was also added to improve the mechanical properties. Morphological analysis showed a good interfacial adhesion when C2C8 is added to the mixture. Raman spectroscopy coupled to optical microscopy revealed that the HDPE phase encapsulated the rubber tire particles. The mixtures containing C2C8 and RTP presented lower ultimate tensile strength and elastic modulus, but the impact strength of the binary and ternary mixtures was much higher than that of neat HDPE.

Mechanical and morphological properties of high density polyethylene and polylactide blends

Abstract Polyblend films were prepared from high-density polyethylene (HDPE) and poly(l-lactic acid) (PLLA) up to 20% PLLA by the melt blending method in an extrusion mixer with post-extrusion blown film attachment. The 80/20 (HDPE/PLLA) blend was compatibilized with maleic anhydride grafted polyethylene (PE-g-MA) in varying ratios [up to 8 parts per hundred of resin (phr)]. Tensile properties of the films were evaluated to obtain optimized composition for packaging applications of both non-compatibilized and compatibilized blends. The compositions HDPE80 (80% HDPE and 20% PLLA) and HD80C4 (80% HDPE, 20% PLLA and 4 phr compatibilizer) were found to be optimum for packaging applications. However, better tensile strength (at yield) and elongation (at break) of 80/20 (HDPE/PLLA) blend were noticed in the presence of PE-g-MA. Further, thermal properties and morphologies of these blends were evaluated. Differential scanning calorimetry (DSC) study revealed that blending does not much affect the crystalline melting point of HDPE and PLLA, but heat of fusion of 80/20 (HDPE/PLLA) blend was decreased as compared to that of neat HDPE. Spectroscopy studies showed evidence of the introduction of some new groups in the blends and gaining compatibility in the presence of PE-g-MA. The compatibilizer influenced the morphology of the blends, as apparent from scanning electron microscopy (SEM) and supported by Fourier transform infrared (FTIR).

Thermo and photo-oxidation of functionalized metallocene high density polyethylene: Effect of hydrophilic groups

Incorporation of a small content of undecenoic acid is proposed as an approach to introduce polar groups within the macromolecular architecture of high density polyethylene-based materials in order to promote an easier degradation after their useful service life. The influence of these hydrophilic groups during thermo and photo-oxidation processes has been then evaluated by several complementary techniques. In addition to different degradation rates, distinct ratios of oxidized species (lactones, ketones, carboxylic acids, esters and aldehydes) are found depending on: a) the initial material (neat high density polyethylene or ethylene-co-undecenoic acid copolymer); b) the type of oxidation (thermo or photoinduced); and c) the absence or presence of a specific prodegradant additive. An important increase of crystallinity has been observed in the final oxidized samples, indicating that the extent of degradation is rather significant.

Preparation, characterization and fouling analysis of ZnO/polyethylene hybrid membranes for collagen separation

In this study, high density polyethylene (HDPE) membranes embedded with ZnO nanoparticles were fabricated via thermally induced phase separation (TIPS) method. A series of tests including FESEM, XRD, TGA, AFM, contact angle measurement, pure water flux, porosity and mean pore radius were performed for characterization of membranes. FESEM images showed that the membranes had leafy structure indicating solid–liquid phase separation mechanism. The results of XRD and TGA analysis confirmed the presence of ZnO nanoparticles in the polymer matrix. AFM images showed that the surface roughness of ZnO embedded membranes were higher than that of neat HDPE membrane. Pure water flux as well as surface hydrophilicity of membranes improved as the ZnO content increased. In addition, the fouling behavior of membranes was investigated by filtration of collagen protein solution. The governing fouling mechanisms of membranes were also investigated using classic models as well as combined fouling models. The results showed that for all membranes the best fit of the data occurred with the cake filtration-complete blockage model (CFCBM). Moreover, the deviation between experimental data and CFCBM prediction decreased by increasing the content of ZnO.