Low Density Polyethylene Blends Research Articles

A new approach for silane curing polyolefin elastomer/linear low density polyethylene blends by Monosil and Sioplas processes

Silane cross-linking of metallocene-based polyethylene-octene elastomer (POE)/linear low density polyethylene (LLDPE) blend was carried out using the single-step Monosil process and two-step Sioplas process in an industrial scale twin-screw extruder. The study revealed that benzoyl peroxide (BPO) is a better initiator than dicumyl peroxide (DCP) for grafting reaction of vinyl trimethoxysilane (VTMS). The optimum values of compression set, gel content and tear strength which were, respectively, found to be 40.4%, 79% and 22.6% obtained at 0.2 w% of BPO. Addition of 0.3 w% antioxidant cause the curing time decreased from 14 to 16 h to 8 h. Oit of the sample was increased linearly with increasing the antioxidant content up to 0.5 w%. The effect of dibutyltin dilaurate (DBTDL) as catalyst on the melt flow index (MFI) of the silane grafted compounds, with the aim of selecting an appropriate silane grafting process, was investigated. The results showed a MFI= 6.4 g/10 min for the silane grafted compound obtained from the Sioplas process, but, MFI= 1.9 g/10 min which was due to the presence of the catalyst in the Monosil process indicated that this method is not a promising process for silane grafting.HighlightsSilane crosslinking POE/LLDPE blend was carried out using the Monosil and Sioplas processes in a twin-screw extruder.BPO is better initiator for grafting reaction of VTMS than DCP.The curing time required for confirming hot set test was decreased from 14 to 16 h to 8 h by addition of 0.3 wt% antioxidant, Irganox 1010.OIT time increased linearly with increasing the antioxidant concentration.Sioplas process caused lower crosslinking degree as well as minimum pre-crosslinking, which prevented the formation of gell spots and rough surface.

Flame retardancy properties and thermomechanical behavior of the nanocomposite of thermoplastic Polypropylene/Linear Low-density Polyethylene blend filled with nano calcium carbonate

The flammability of thermoplastic polymers, especially of polypropylene, considers one of the crucial global concerns because of the numerous applications of these materials in different aspects of modern life. So, the efforts of scientists are focused on developing the effective flame retardants especially with the progress in the nanotechnology. In this work, Fire retardancy performance, mechanical properties, thermomechanical behavior and thermal stability of the blend of polypropylene (PP) - linear Low density polyethylene (LLDPE) filled with nano calcium carbonate (NCC) were examined. The blend was contained on 90% PP and 10% LLDPE with different loadings of nano calcium carbonate (1.5%, 3%, 6%, 9% of PP weight). The samples were prepared by the extrusion method. The mechanical tests were tensile and bending tests while fire retardancy tests were limited oxygen index (L.O.I), U-94 protocol tests and ash content. The thermomechanical tests were thermal expansion coefficient, and thermal E-modulus. Thermal stability was examined using differential scanning calorimetry (DSC) and Differential Thermal Analysis (DTA). The results of tests showed the positive role of using nano calcium carbonate as filler for this blend. The mechanical properties, thermal expansion coefficient and thermomechanical behaviour were increasing and the highest values were recorded for 6% sample. While the maximum values of thermal stability, and fire resistance properties were recorded for 9% sample. The other nano calcium carbonate addition ratios showed varies responses. The fire retardancy properties were enhanced with using NCC filler. The results of the present work showed the success of using nano calcium carbonate with PP-LLPE blend as a fire retardant.

HDPE/LLDPE blends: rheological, thermal, and mechanical properties

ABSTRACT This work investigated the rheological, thermal and mechanical properties of High-Density Polyethylene/Linear Low-Density Polyethylene (HDPE/LLDPE) blends. The results of rheological properties showed an increase in the complex viscosity with the increase in LLDPE content and miscibility between HDPE and LLDPE phases. X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) analyses showed a decrease in the degree of crystallinity of HDPE/LLDPE blends with the increase in the LLDPE content. The HDPE/LLDPE blends showed higher thermal stability than HDPE/LLDPE blends. Morphology analysis by SEM indicated an increase in the plastic deformation with the increase in the LLDPE content, leading to a substantial increase in the impact strength.

PCO-LLDPE thermoresponsive shape memory blends. Towards a new generation of breathable and waterproof smart membranes

Different polycyclooctene (PCO) and linear low-density polyethylene (LLDPE) blends were crosslinked with 2 wt% of dicumyl peroxide (DCP) in order to obtain thermoresponsive shape memory materials with transition temperatures close to bodýs external temperature. These polymeric blends allow tailoring properties by the synergic combination of shape-memory capability of PCO and effective mechanical and processing performance of polyethylene. Thermal stability of these materials was characterised by thermogravimetric analysis (TGA), whereas mechanical performance was measured by dynamic mechanical analysis (DMA) and tensile tests. Besides, thermal properties were measured by differential scanning calorimetry (DSC), where the melting temperature of crystalline PCO phase around 40–50 °C were observed. Considering this shape memory triggering temperature, the shape memory capabilities of the samples were studied by thermo-mechanical analysis (TMA), and outstanding shape recovery ratios were obtained. Finally, water contact angle (WCA) and water vapour transmission rate (WVTR) were measured above and below that transition temperature to assess moisture permeability changes. In this case, observed increase by an order of magnitude in vapour permeability with temperature offers promising opportunities in developing thermo-active membranes for textile applications with these PCO-LLDPE blends.

Improvement in volume resistivity and morphology of a blend of polyolefin elastomer with linear low-density polyethylene

A silane moisture-cured polyolefin elastomer/linear low-density polyethylene (LLDPE) blend was prepared through a two-step silane-grafting method (Sioplas Process) in an industrial scale twin-screw extruder. The silane-grafted compound was used to make wire and cable coatings. In this work, the effect of some interactive parameters on quality of the products prepared by the above method has been studied, while so far, there have been less experimental investigations. The volume resistivity of cross-linked compound was changed from 2.96 × 1014 to 7.41 × 1014 Ω cm with increasing LLDPE component by maximum 10 wt%. Surface morphology of the product was corrected with reduction in benzoyl peroxide (BPO) concentration from 0.2 wt% to 0.13 wt%. BPO at this level acted as an initiator in grafting reaction of vinyl trimethoxysilane. The curing condition and specimen preparation method by injection molding and/or extrusion were factors which influenced the hot-set test results at 200 °C. The results of tensile and elongation studies showed a maximum value of 9 MPa and 397% for the tests, after 6 h curing. With increases in curing time at a specified temperature, the gel content of the cross-linked compound was increased and reached its maximum value. The maximum gel content values were found to be approximately 60%, 80%, and 82% at temperatures of 25, 60, and 85 °C, respectively. The hardness, density, and tear strength of the samples did not vary significantly with the curing temperature.

Graphene Enhanced Electrical Properties of Polyethylene Blends for High-Voltage Insulation

Graphene as a novel additive in low density polyethylene (LDPE), high density polyethylene–low density polyethylene blend (10%HDPE–LDPE) and polypropylene–low density polyethylene blend (10%PP–LDPE), is investigated for promising eco-friendly insulating materials in high voltage cables. The composites with graphene amounts of 0, 0.002 wt%, 0.02 wt%, and 0.2 wt% are prepared by the solution mixing method. With attempt to disclose the structure–property relationships, the composites are extensively characterized by physical techniques including Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis and differential scanning calorimetry, and electrical measurements including electrical treeing, direct current conductivity and space charge distributions. Results show that graphene can significantly enhances the thermal stability of LDPE and 10%PP–LDPE, slightly decrease the degree of crystallinity, change the size of the crystal diameters, and improve the phase distribution of the polymer blends. Consequently, graphene can prolong the electrical tree initiation time and block the extension of electrical tree. Besides, it can modulate the trap distributions, which will further change the conductivity and ability to suppress space charge accumulations. This excellent performance of graphene could be attributed to its good exfoliation, uniform dispersion and outstretched morphology in the polymer matrix, as well as its strong ability to capture electrons.

Effect of hydrophilic and hydrophobic cyclodextrins on the release of encapsulated allyl isothiocyanate (AITC) and their potential application for plastic film extrusion

ABSTRACTAllyl isothiocyanate (AITC), a natural pungent flavor from wasabi and horseradish, is well‐known antimicrobial agents against foodborne pathogens. However, its highly volatile nature and low thermal stability restrict its application in the food packaging industry. Also, its strong organoleptic characteristics hinder its application at a higher dosage. We encapsulated AITC in β‐cyclodextrin (β‐CD) and triacetyl‐β‐CD (TA‐β‐CD) and evaluated the performance as slow releasing active compounds through low‐density polyethylene (LDPE)–cyclodextrins (CDs) matrix. Also, the thermal, optical, mechanical, and barrier properties of two ternary blends, LDPE/β‐CD/AITC(L‐CDs) and LDPE/TA‐β‐CD/AITC(L‐TACDs), were investigated to compare their compatibility under the plastic extrusion process. During the 15 days of the storage period, L‐TACDs maintained more consistent AITC release and a higher concentration than L‐CDs. Also, the blending of LDPE and TA‐β‐CD was more compatible with that of LDPE and β‐CD. No significant optical, mechanical, and barrier property changes were observed in LDPE with less than 3% of TA‐β‐CD while L‐CDs showed substantial agglomeration on the ternary blend films and the lower mechanical and barrier properties than pure LDPE. The results indicate that the LDPE films containing TA‐β‐CD/AITC can be applied as an effective antimicrobial packaging material for food and nonfood applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48137.

An analysis of melt spinning master-curves of low-density polyethylene/linear low-density polyethylene blends

Abstract The melt elongation rheological behavior of a low-density polyethylene (LDPE) blended with a linear low-density polyethylene (LLDPE) was studied using a melt spinning technique. Based on the extension properties of the LDPE/LLDPE blend melt under experimental conditions, the melt spinning master-curves were plotted by introducing scaling factor b. The results showed that the extension load increased with increasing extension rate while decreased with increasing die extrusion temperature. It was found that the melt spinning master-curves could describe the elongation rheological behavior of the LDPE/LLDPE melt melts under different conditions including various die extrusion temperatures, die extrusion rates and LLDPE weight fractions. In addition, both the relationship between the scaling factor and absolute temperature and the relationship between lg b and lg v 0 were linear.

Microcellular Foaming Behaviors of Poly (Lactic Acid)/Low-Density Polyethylene Blends Induced by Compatibilization Effect

A facile methodology for improving the crystallization ability, rheological properties and microcellular foaming behaviors of poly (lactic acid)/low-density polyethylene (PLA/LDPE) blends through compatibilization was proposed. Poly (ethylene octene) grafted with glycidyl methacrylate (GPOE) as reactive compatibilizer was introduced into PLA/LDPE blends and the resultant PLA/LDPE/GPOE blends were foamed by supercritical CO2. Torque curves and Fourier transformation infrared spectroscopy results confirmed that GPOE reacted with PLA successfully. The crystallization ability and rheological properties of PLA was promoted obviously by the addition of LDPE and GPOE. The size of LDPE dispersion phase in PLA/LDPE blends decreased from 4.4 ± 0.1 to 1.2 ± 0.1 µm, owing to the compatibility effect. When the content of GPOE reach 8 phr, microcellular structure appeared in the PLA/LDPE/GPOE blending foam. An interesting flower-like cellular structure was observed in PLA/LDPE/GPOE blending foams, with the foaming temperature at 85 and 90 °C. Finally, the microcellular foaming mechanism for various PLA foams was proposed and clarified using schematic diagram.

Effect of LLDPE-g-MA on the rheological, thermal, mechanical properties and morphological characteristic of PA6/LLDPE blends

The development of polyamide 6 (PA6) and linear low-density polyethylene (LLDPE) blends is of great technological interest, as they have the potential to combine the good mechanical and thermal properties of PA6 with the high impact properties and good processability of the LLDPE. However, these two polymers are chemically and structurally different and therefore immiscible, and in general incompatible. The objective of this study was to evaluate the effect of maleic anhydride-grafted linear low-density polyethylene (LLDPE-g-MA) as compatibilizer agent on rheological, thermal, mechanical and morphological properties of PA6/LLDPE blends. PA6/LLDPE blends with different contents of LLDPE (10, 20, 30, 40 and 50 wt%) and with the addition of LLDPE-g-MA (5 wt%) were prepared in a twin screw extruder and the thermal and mechanical analysis were performed. The addition of LLDPE-g-MA as compatibilizer agent resulted in a better distribution and dispersion of LLDPE in PA6 matrix and a significant improvement in mechanical and thermal properties. The addition of the compatibilizer agent increased 160% the impact strength for the 50/50 (PA6/LLDPE) blend.

Study of the degradation profile for virgin linear low-density polyethylene (LLDPE) and polyolefin (PO) plastic waste blends

In this study, the properties of virgin linear low-density polyethylene (LLDPE) and its blends with reclaimed plastic solid waste (PSW) are investigated by thermogravimetry, differential scanning calorimetry (DSC), infrared spectroscopy and scanning electron microscopy (SEM). The PSW constituted polyolefin (PO) polymers recycled mechanically via extrusion/blown-film and exposed to accelerated weathering tests to determine the change in their degradation behaviour. The oxidation products determined using the FTIR analysis and thermal stability studies points toward the blend constituting 25% of waste by weight as the most stable. Changes in crystallinity of the polymers were attributed to the crystal size change as a consequence of the weathering mechanism. The DSC results revealed that both oxidation induction temperature (OIT) and crystallinity were affected by the PO waste content. This points towards the impact of polymers immiscibility and polydispersity within the matrix of the blends due to chain scission reaction and oxidation with the UV exposure.

A New Strategy for the Use of Post-Processing Vacuum Bags from Aerospace Supplies: Nucleating Agent to LLDPE Phase in PA6/LLDPE Blends

In the aerospace industry, many composite parts are manufactured by processes using plastic vacuum bags made of polyamide 6 (PA6) as a consumable material. This implies that after demolding the part, this plastic material should be discarded, generating a considerable amount of waste. Tons of vacuum bags are discarded and incinerated per month by several companies in this sector, which highlights the need to recycle and/or reuse this material. PA6/linear low-density polyethylene (LLDPE) blends are of great technological interest because they can combine the excellent thermo-mechanical and oxygen barrier properties of the PA6 with high impact strength, good processability, and low cost of LLDPE. The replacement of neat PA6 by the post-processing vacuum bags residue PA6 may be a new strategy for the recycling of this material. In this work, PA6/LLDPE/maleic anhydride-grafted LLDPE (LLDPE-g-MA) (90/5/5) blends were prepared using a co-rotational twin-screw extruder and the neat PA6 was replaced by different contents of post-processing PA6 (5, 10, 15 and 20 wt.%). The mechanical, thermal, and morphological characterization was evaluated. The increase in the content of post-processing PA6 caused an increase in the crystallinity degree of the LLDPE phase, acting as a nucleating agent to the LLDPE phase, reducing the toughening effect of this phase in the blends and, therefore, providing this phase to act as a reinforcing agent.

Shape Memory Behavior of Natural Eucommia ulmoides Gum and Low-Density Polyethylene Blends with Two Response Temperatures.

A series of shape memory blends of natural Eucommia ulmoides gum (EUG) and low-density polyethylene (LDPE) with a bicontinuous cross-linked structure were prepared by a physical blending method, which could be used in the field of thermal response with two different temperatures. We report the shape memory properties of these blended materials with two response temperatures for the first time. The mechanical, curing, thermal and shape memory properties of the blends were studied in this manuscript. Schematic diagrams are proposed to illustrate the dual shape memory behaviors of the EUG/LDPE blends. Our study focused on observing the relationship between the shape memory behavior and the microscopic crystalline phase states in the blends. In the blends, both the cross-linked network and the LDPE crystalline regions could act as fixed domains, while the crystalline regions of LDPE or EUG could act as the reversible domain. The shape memory properties were mainly determined by the components of the fixed and reversible domains. We focused on the shape memory behavior of blends at 60 °C and 130 °C in this manuscript. The results showed that when the peroxide dicumyl peroxide (DCP) dosage was 1.0 phr, the blends exhibited acceptable shape behavior at 60 °C (R1f = 74.8%, R1r = 63.3%). At the same time, when DCP dosage was 0.4 phr, the shape memory behavior of the blends at 130 °C was good and much better than that at 60 °C (R2f = 91.1%, R2r = 89.4%).

Sustainable blends of LDPE/NR and sugarcane bagasse ashes with PE-g-MA thermomechanical relationships

ABSTRACT The polymer blends obtained with residues that before were called wastes has been growing as a viable solution, allowing improvements in the mechanical properties and as sustainable alternative. This work reports the effects of blends of low-density polyethylene (LDPE) and natural rubber (NR), with sugar cane bagasse ash (SCBA) as filler, with and without polyethylene-graft-maleic anhydride (PE-g-MA) how coupling agent. The dynamic mechanical behavior and a stress-strain analysis were studied. The materials were further evaluated by differential scanning calorimetry and morphological observations. The results showed that incorporation of the PE-g-MA reduced the strain and improved the stress and the Young module of the mixtures. Moreover, the presence of SCBA increased the hardness while maintaining the tensile strength and the elongation behavior of the polymer. The results demonstrate the potential use of SCBA in the elastomer and thermoplastic mixture, free of vulcanization agents.

Environmentally Friendly Packaging Materials Based on Thermoplastic Starch

Low-density polyethylene (LDPE) is extensively used as packaging material, and as such has a short service life, but long environmental persistence. The alternative to reducing the impact of LDPE as packaging material on the environment is to blend it with carbohydrate-based polymers, like starch. Therefore, the focus of this investigation was to prepare bio-based blends of LDPE and thermoplastic starch (TPS) containing different amounts of TPS using a Brabender kneading chamber. Due to incompatibility of LDPE/ TPS blends, a styrene–ethylene/butylene–styrene block copolymer, grafted with maleic anhydride (SEBS-g-MA) containing 2 mol % anhydride groups, was added as a compatibilizer. The effect of the biodegradable, hydrophilic TPS, its content, and the incorporation of the compatibilizer on the properties of LDPE/TPS blends were analysed. The characterization was performed by means of thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and water absorption (WA). Based on the results of the morphological structure, a good dispersion of the TPS phase in LDPE matrix was obtained with the incorporation of compatibilizer, which resulted in better thermal and barrier properties of these materials.

Eco-friendly polymer materials for agricultural purposes

The paper deals with various polymer materials for agricultural purposes. To date, there are many technologies for growing crops that use polymer films: greenhouses, greenhouses, planting seeds in capsules. There are a lot of works on the study of biodegradable compositions based on biopolymers with synthetic polymers, as well as the analysis of the impact of destructive environmental factors on samples. Binary polylactide–low-density polyethylene blends of various compositions were prepared, and their biodegradability in soil and water absorption kinetics. The degree of water absorption is higher for the blends than for the pure polymers. The weight loss is higher upon incubation in laboratory soil compared to open soil. Changes in the specimen macrostructure after exposure to soil were demonstrated by optical microscopy.

In-situ grafting of carboxylic acid terminated poly(methyl methacrylate) onto ethylene-glycidyl methacrylate copolymers:One-pot strategy to compatibilize immiscible poly(vinylidene fluoride)/ low density polyethylene blends

Reactive compatibilization is an effective strategy to improve compatibility of incompatible polymer blends. However, the strategy is usually limited to the polymer blends that one of the components contains reactive groups. In this work, we have succeeded in the reactive compatibilization of the immiscible poly(vinylidene fluoride)/low density polyethylene (PVDF/LDPE) blends of which both components do not contain the reactive groups. We simultaneously incorporated the carboxylic acid terminated poly(methyl methacrylate) (PMMA) oligomer (PMMA−COOH) and ethylene-glycidyl methacrylate copolymer (EGMA) into the PVDF/LDPE blend. The ring-opening reactions of the carboxylic acid groups of PMMA oligomer and epoxide groups on the EGMA main chains happen during the melt blending and the in-situ formed EGMA-g-PMMA graft copolymers enhance the compatibility of PVDF/LDPE blends significantly. The reactive compatibilized PVDF/LDPE blends have the elongation at break and fracture strength of 507% and 40.2 MPa, respectively, as compared with the 11% and 25.6 MPa of the uncompatibilization blends. Moreover, the architecture effects of the in-situ formed EGMA-g-PMMA by varying PMMA-COOH oligomer loadings, PMMA-COOH molecular weight and the processing time on the compatibilization efficiency have been investigated. It was found that compatibilizing efficiency increases with increasing the grafted density, the length of the side chain and the degree of reaction. This one-pot strategy with the in-situ formed graft compatibilizers in incompatible blends paves new possibility for unreactive blends by reactive compatibilization.

Hollow Fiber Porous Nanocomposite Membranes Produced via Continuous Extrusion: Morphology and Gas Transport Properties.

In this work, hollow fiber porous nanocomposite membranes were successfully prepared by the incorporation of a porous nanoparticle (zeolite 5A) into a blend of linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE) combined with azodicarbonamide as a chemical blowing agent (CBA). Processing was performed via continuous extrusion using a twin-screw extruder coupled with a calendaring system. The process was firstly optimized in terms of extrusion and post-extrusion conditions, as well as formulation to obtain a good cellular structure (uniform cell size distribution and high cell density). Scanning electron microscopy (SEM) was used to determine the cellular structure as well as nanoparticle dispersion. Then, the samples were characterized in terms of mechanical and thermal stability via tensile tests and thermogravimetric analysis (TGA), as well as differential scanning calorimetry (DSC). The results showed that the zeolite nanoparticles were able to act as effective nucleating agents during the foaming process. However, the optimum nanoparticle content was strongly related to the foaming conditions. Finally, the membrane separation performances were investigated for different gases (CO2, CH4, N2, O2, and H2) showing that the incorporation of porous zeolite significantly improved the gas transport properties of semi-crystalline polyolefin membranes due to lower cell wall thickness (controlling permeability) and improved separation properties (controlling selectivity). These results show that mixed matrix membranes (MMMs) can be cost-effective, easy to process, and efficient in terms of processing rate, especially for the petroleum industry where H2/CH4 and H2/N2 separation/purification are important for hydrogen recovery.

Studies on reactive blending of LDPE and cenosphere

The present work aims to modify conventional low density polyethylene (LDPE) by preparing its particulate composite with cenosphere. Cenosphere is a potential waste produced in bulk from the coal fired thermal power plant. In this context, surface modification of cenosphere was done by γ- aminopropyl triethoxy silane (ATS) coupling agent. Furthermore, LDPE was grafted by glycidyl methacrylate (GMA) to be used as compatibilizer. The resulting surface modified and unmodified cenosphere as well as glycidyl methacrylate grafted LDPE (LDPE-g-GMA) were functionally characterized by Fourier Transform Infrared (FT-IR) spectroscopy. LDPE-cenosphere particulate composites were processed in their different formulations and evaluated with various properties such as thermal stability, mechanical properties, chemical resistance and flow behaviour. Dispersibility of cenosphere in LDPE matrix was studied by Scanning Electron Microscopy (SEM). Series of analysis was performed in order to understand the effect of cenosphere content and its modification on the final properties of particulate composites. Mechanical properties were found to be statistically significant as per ANOVA and Post hoc Tukey HSD test. Particulate composites prepared with modified interphase were observed to possess good combination of properties.

Development of co-continuous morphology in blends of thermoplastic starch and low-density polyethylene

This study focuses on the morphology development in blends of thermoplastic starch (TPS) with Low Density Polyethylene (LDPE) in the 40 to 80 TPS wt% concentration range. The effect of glycerol and water content on TPS rheology and the subsequent morphology development after blending with LDPE of various viscosity levels was investigated. The TPS/LDPE viscosity ratio was modified either by increasing the TPS plasticization or by proper selection of the LDPE grade. Particular attention was given to the effect of TPS humidity on viscosity and therefore humidity levels were carefully measured by Karl Fisher titration prior to rheometry. It was found that the viscosity of the TPS was highly dependent on the plasticizer level and that the flow activation energy of TPS was around 3 times higher than that of LDPE. Different types of blend morphologies were achieved from dispersed to co-continuous. It was found that the co-continuous structure appeared at higher TPS concentration when increasing the TPS/LDPE viscosity ratio.