Polyethylene Blends Research Articles

Manufacturing of wood plastic composite from polyethylene/poly(ethylene terephthalate) waste/ultra high molecular weight polyethylene blends and rice husk fiber: Effect of blends ratio and peroxide/silane crosslink system

Lowering processing temperature of poly(ethylene terephthalate) waste (rPET) and ultra-high molecular weight polyethylene (UHMWPE) by blending to avoid decomposition of rice husk fiber (RHF) during the manufacturing of wood plastic composite (WPC) was one of the main goals of the research study. (rPET/LDPE)-g-MA and (HDPE/LDPE/UHMWPE)-g-MA blends were prepared with good flowability at 240°C. The MA grafted chain in the blends were verified by FTIR. Good miscibility and compatibility of the blends were revealed by SEM. The effect of blends ratios employed as blended matrices on performance properties of the manufactured WPC were explored. MFI and HDT were increased with decreasing (rPET/LDPE)-g-MA ratio. The reversed domain phase between rPET and blended PE mixture was pronounced at 50:50 ratio. Mechanical performances were generally reduced upon decreasing the (rPET/LDPE)-g-MA ratios. The reduction of high strength rPET fraction in the blended matrices was taken as the main cause. Exceeding the reversed phase ratio, the declining of the toughness was retarded due to rising on the interfacial strength and UHMWPE toughener fraction. The effect of DCP/VTMS crosslinker on the properties of the macro crosslinked WPC (XWPC) was investigated. The elastomeric bridges on the sauna cured WPC samples were revealed by SEM. High crosslink density upon increasing the crosslinker fraction had an obvious effect on MFI, HDT, toughness and ductility of the macro crosslinked XWPC. However, the flexible characteristic of the elastomeric amorphous PE chains in the blended matrices at high DCP/VTMS usage was manifested as brittleness retardant for the macro crosslinked XWPC.

Silver/Hydrogen-Exchanged Zeolites Embedded in Modified Polyethylene Blends for Antibacterial Packaging with Prolonged Color Stability

Silver/Hydrogen-Exchanged Zeolites Embedded in Modified Polyethylene Blends for Antibacterial Packaging with Prolonged Color Stability

Effects of compositional parameters on morphology and rheological properties of HDPE/PVA blends

AbstractPolymeric blends are relevant for research and industry because of their versatility, being able to accomplish property tailoring with competitive cost and ease to scale up, when compared to the development of in‐reactor new polymers. Blends of thermoplastics, however, might have their morphology and properties altered upon processing, therefore, there is uncertainty to some outputs after melt processing. Therefore, having a fixed morphology that is capable of being further processed without significant changes have industrial and academic value. This work presents a comprehensive study of rheological properties and morphology of a selectively crosslinked blend of polyethylene (HDPE) and poly(vinyl alcohol) (PVA), where the effect of the following parameters are evaluated: dispersed phase (PVA) weight fraction, continuous phase (HDPE) rheological properties, compatibilizer (PE‐g‐MAh) and crosslinking agent (maleic anhydride) content. Overall, melt complex viscosity and elasticity have increased with PVA weight fraction and HDPE viscosity. The compatibilizer content has not severely affected melt rheology, although it influenced blend morphology. Crosslinking agent content affected melt rheology and glass transition temperature in a complex way due to the probable competition of some phenomena (crosslinking and reaction vs reduction of crystallinity degree and H bond attenuation), with little effect over PVA morphology.

A Systematic Investigation on the Influence of Intumescent Flame Retardants on the Properties of Ethylene Vinyl Acetate (EVA)/Liner Low Density Polyethylene (LLDPE) Blends.

Because of their high filler loadings, commercial-grade clean flame-retardant materials have unstable mechanical properties. To address this issue, intumescent polymers can be used to develop clean flame retardants with very low levels of smoke and toxicity generation. An intumescent flame retardant (IFR) system composed of red phosphorus (RP), zinc borate (ZB), and a terpolymer of ethylene, butyl acrylate, and maleic anhydride (EBM) was used to prepare EVA (ethylene-vinyl acetate) and EVA/LLDPE (linear low-density polyethylene) composites; their mechanical and flammability properties were systematically investigated. The limiting oxygen index (LOI) of the EVA/LLDPE (as base material) composite containing RP and ZB mixed with nonhalogenated flame retardant, mainly magnesium hydroxide (MH) and coadditives, including processing aids and thermal stabilizers, was established. RP was found to have little effect on the tensile properties of EVA/LLDPE 118W/120 phr flame-retardant (MH + RP) composites. There was a minute difference in the effective trend of RP between tensile strength and elongation at break. Following the addition of ZB, the elongation at break of the composites gradually decreased with increasing RP content and then leveled off when the RP content was over 10 phr. Mechanical properties (elongation at break and tensile strength) can be best maintained at below 10 phr content of RP. The mechanical properties decreased with lower amounts of EBM content. In addition, flame retardancy increased when the EBM content decreased. The findings further revealed that MH and RP have poor compatibility, yielding poor mechanical properties. The LOI greatly increased with RP content, even though the total content of flame retardants (main + intumescent flame retardant) was the same in all formulations. Only over 5 phr RP content formulations passed V-0 of the UL-94 test. When under 5 phr, the RP content formulations did not pass V-0 of the UL-94 test.

Blending of Low-Density Polyethylene and Poly(Butylene Succinate) (LDPE/PBS) with Polyethylene-Graft-Maleic Anhydride (PE-g-MA) as a Compatibilizer on the Phase Morphology, Mechanical and Thermal Properties.

It is of significant concern that the buildup of non-biodegradable plastic waste in the environment may result in long-term issues with the environment, the economy and waste management. In this study, low-density polyethylene (LDPE) was compounded with different contents of poly(butylene succinate) (PBS) at 10-50 wt.%, to evaluate the potential of replacing commercial plastics with a biodegradable renewable polymer, PBS for packaging applications. The morphological, mechanical and thermal properties of the LDPE/PBS blends were examined in relation to the effect of polyethylene-graft-maleic anhydride (PE-g-MA) as a compatibilizer. LDPE/PBS/PE-g-MA blends were fabricated via the melt blending method using an internal mixer and then were compression molded into test samples. The presence of LDPE, PBS and PE-g-MA individually in the matrix for each blend presented physical interaction between the constituents, as shown by Fourier-transform infrared spectroscopy (FTIR). The morphology of LDPE/PBS/PE-g-MA blends showed improved compatibility and homogeneity between the LDPE matrix and PBS phase. Compatibilized LDPE/PBS blends showed an improvement in the tensile strength, with 5 phr of compatibilizer providing the optimal content. The thermal stability of LDPE/PBS blends decreased with higher PBS content and the thermal stability of compatibilized blends was higher in contrast to the uncompatibilized blends. Therefore, our research demonstrated that the partial substitution of LDPE with a biodegradable PBS and the incorporation of the PE-g-MA compatibilizer could develop an innovative blend with improved structural, mechanical and thermal properties.

Manufacturing of wood plastic composite from polyethylene/poly(ethylene terephthalate) waste/ultra high molecular weight polyethylene blends and rice husk fiber: Raw materials preparation and preliminary processing investigation

The processing temperature of poly(ethylene terephthalate) waste (rPET) and ultra-high molecular weight polyethylene (UHMWPE) was lowered by blending to avoid decomposition of rice husk fiber (RHF) during the manufacturing of wood plastic composite (WPC). Maleic anhydride (MA) grafted blends of HDPE/LDPE/UHMWPE-g-MA and rPET/LDPE-MA were prepared. Those blends were flowable at 240 °C. They were employed as blended matrices to make HDPE/LDPE/UHMWPE-g-MA/rPET/LDPE-MA/RHF wood composite at processing temperatures not exceeding 240 °C. The study of RHF loading on the WPC performance revealed that melt flow index (MFI) and mechanical performances measured by impact, flexural, and tensile properties were weakened, but heat distortion temperature (HDT) was enhanced at high RHF loading. When the stabilizer content did not exceed 2 phf, the toughness and ductility were improved. Surface treatment of RHF by MA and dicumyl peroxide (DCP) enhanced the interfacial surface adhesion, but the toughness and ductility of the WPC were reduced at high MA/DCP dosing. The formation of crosslink structure via peroxide free radical initiated reaction at the MA grafted branch chains was the prime suspect for the inferiority of the mechanical performances.

Influence of high-density polyethylene content on the rheology, crystal structure, and mechanical properties of melt spun ultra-high-molecular weight polyethylene/high-density polyethylene blend fibers

High-density polyethylene (HDPE) content significantly influences the structure and mechanical properties of ultrahigh molecular weight polyethylene (UHMWPE)/HDPE blend fibers. The molecular chain disentanglement and crystallization characteristics of as-spun filaments and fibers and how the structure affects the final mechanical properties of the fibers were thoroughly studied by adding different contents of HDPE. Dynamic mechanical analysis (DMA) and rheological analysis indicated that the molecular entanglement decreased with increasing HDPE content, improving the UHMWPE melt processability. Sound velocity orientation (SVO) studies indicated that the UHMWPE/HDPE as-spun filaments and fibers with an HDPE content of 40 wt% (U6H4) had a higher molecular chain orientation level. Furthermore, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analyses indicated that U6H4 had the highest crystallinity and the thinnest grains in the axial direction, respectively. The compact crystal structure and fully stretched molecular chains of U6H4 yielded the best mechanical properties. The present work disclosed the effect mechanism of HDPE contents on the preparation and properties of UHMWPE/HDPE fibers, which provided an effective and universal strategy for manufacturing high-strength UHMWPE/HDPE fibers with the melt spinning method.

Crystallization, Phase and Mechanical Behaviors of Linear Low Density Polyethylene/Thermoplastic Polyolefin Elastomer Blends

Blending polyethylene with thermoplastic polyolefin elastomers (TPOs) is a promising way to manipulate its structures and tailor its properties. Herein, three TPOs, i.e., two ethylene–octene copolymers (EOCs) and an olefin block copolymer (OBC) with different structures, were used to comparatively investigate the miscibility, crystallization, and phase behavior of their blends with a linear low-density polyethylene (LLDPE). It was found that large differences occurred in the crystallization and phase behaviors of the blends due to the different extent of similarity in the molecular structure between the TPO and the LLDPE matrix. In particular, a unique segregated phase morphology comprised a less stable crystalline phase and a rubbery phase was found in an LLDPE/EOC blend. The tensile performance and elasticity of the blends were also studied and correlated with the structures of the blends. This work not only provides novel results on the miscibility and phase behavior of the similar-structured LLDPE/TPO blends, but can also guide the design of LLDPE-based products with tailored performances.

Intrinsically Heat Tolerant, UV Resistant EVA/ LDPE thermoplastic elastomeric encapsulant – An alternative for conventional crystalline silicon PV module encapsulant

28% vinyl acetate content Ethylene Vinyl Acetate copolymer (EVA) and Low Density Polyethylene (LDPE) blend is a newly developed thermoplastic elastomeric encapsulating system for silicon Photovoltaic (PV) module. Differential scanning calorimetry (DSC) studies has been revealed the inter-miscibility nature of these two polymers blend in the amorphous zones. Thermogravimetric analysis (TGA) result confirms that the EVA-LDPE blend is more thermal stable than the pristine EVA. Encapsulation provides electrical insulation between the solar cells and the electrical circuit of the PV module. Electrical insulation property in terms of DC surface resistivity (SR) and DC volume resistivity (VR) were studied. Insulation property of EVA-LDPE blends under UV radiation has been explored in this article and the change in insulation property has been correlated with the degradation factors. Accelerated UV ageing was performed as per cycle 2 of ASTM G 154 – 2016 for 1000 hours. The thermal resistance and electrical insulation properties were significantly reduced for pristine EVA after 1000 hours UV ageing while >52% property retention found for EVA-LDPE blend.

Effect of Nano-SiO2 on Different Stages of UHMWPE/HDPE Fiber Preparation via Melt Spinning

Ultra-high molecular weight polyethylene (UHMWPE)/high-density polyethylene (HDPE) blend with lower viscosity is more suitable for melt spinning compared to pure UHMWPE; however, the mechanical property of the blend fiber is hard to dramatically improve (the maximum tensile strength of 998.27 MPa). Herein, different content modified-nano-SiO2 is incorporated to UHMWPE/HDPE blend fiber. After adding 0.5 wt% nano-SiO2, the tensile strength and initial modulus of UHMWPE/HDPE/nano-SiO2 fiber are increased to 1211 MPa and 12.81 GPa, respectively, 21.57% and 43.32% higher than that of UHMWPE/HDPE fiber. Meanwhile, the influence of the nano-SiO2 content on the performance for as-spun filament and fiber are emphatically analyzed. The crystallinity and molecular chain orientation of as-spun filament reduces with the addition of nano-SiO2. On the contrary, for fiber, the addition of nano-SiO2 promoted the crystallinity, molecular chain orientation and grain refinement more obvious at a lower content. Furthermore, the possible action mechanism of nano-SiO2 in the as-spun filament extrusion and fiber hot drawing stage is explained.

Crystallization Kinetics in an Immiscible Polyolefin Blend.

Motivated by the problem of brittle mechanical behavior in recycled blends of high density polyethylene (HDPE) and isotactic polypropylene (iPP), we employ optical microscopy, rheo-Raman, and differential scanning calorimetry (DSC) to measure the composition dependence of their crystallization kinetics. Raman spectra are analyzed via multivariate curve resolution with alternating least-squares (MCR-ALS) to provide component crystallization values. We find that iPP crystallization behavior varies strongly with blend composition. Optical microscopy shows that three crystallization kinetic regimes correspond to three underlying two-phase morphologies: HDPE droplets in iPP, the inverse, and cocontinuous structures. In the HDPE droplet regime, iPP crystallization temperature decreases sharply with increasing HDPE composition. For cocontinuous morphologies, iPP crystallization is delayed, but the onset temperature changes little with the exact blend composition. In the iPP droplet regime, the two components crystallize nearly concurrently. Rheological measurements are consistent with these observations. DSC indicates that the enthalpy of crystallization of the blends is less than the weighted values of the individual components, providing a possible clue for the decreased iPP crystallization temperatures.

Adhesion Properties of Polyethylene and Ethylene-Vinyl Acetate Copolymer Blend with Acrylate Copolymers of Ethylene

Adhesion Properties of Polyethylene and Ethylene-Vinyl Acetate Copolymer Blend with Acrylate Copolymers of Ethylene

Thermal degradation and thermal kinetic of SEBS block copolymer compatibilized PS/HDPE blends

The effect of styrene-ethylene/butylene-styrene block copolymer (SEBS) on the thermal degradation of polystyrene (PS)/high density polyethylene (HDPE) blends have been investigated. Polystyrene and (HDPE) are widely used thermoplastics, which have extensive application in everyday life. The main disadvantage of PS/PE systems is their poor miscibility which can be improved by adding compatibilizer. The blends were prepared by melt mixing in a twin screw extruder Haake Record 90. The behavior of the thermal degradation of PS/HDPE and PS/HDPE/SEBS blends has been investigated in inert nitrogen atmosphere by using thermogravimetric analysis (TGA) to obtain the degradation temperature and activation energy ( E a). The Ea for the PS/HDPE blends as well as for the PS/HDPE/SEBS blends was determined by the isoconversional Kissinger–Akahira–Sunose (KAS) method. The results indicated that the HDPE enhance thermal properties of the blends. The addition of SEBS in PS/HDPE blends increased the E a in all blends.

Self-nucleation and heterogeneous nucleation in ethylene/1-octene random copolymer and its linear polyethylene blends

Self-nucleation normally denotes an increase in the crystallization temperature during cooling down from certain preheated (seeding) temperature due to the existence of unmolten crystalline nuclei or some heterogenous structures which can induce melt memory effect. It is one of the crucial parts in the study of polymer crystallization behavior which provides a meaningful guidance in both academia and industry to accelerate crystallization of polymers. In this work, self-nucleation effects of a commercial ethylene/1-octene random copolymer with 12 mol% 1-octene content and its blends with small amount of linear polyethylene (LPE) were investigated. The ethylene/1-octene random copolymer possesses strong self-nucleation effect whereas in the blends the crystallization temperature increases with the seeding temperature and eventually stabilized at certain constant temperature when the seeding temperature is high enough. This result is clearly due to the heterogenous nuclei generated by the crystallization of LPE during cooling. The strength of the heterogenous nucleation effect i.e. the crystallization temperature is positively related to the degree of dispersion of LPE in the mixture.

Aging phenomena in non-crosslinked polyolefin blend cable insulation material: Electrical treeing and thermal aging.

Non-crosslinked polyolefin blends have become a favorable alternative material to crosslinked polyethylene (XLPE) cable insulation owing to their low power consumption in the production process and good recyclability at the end of service life. Although studies on non-crosslinked materials have achieved significant results, the electrical and thermal aging properties of these materials undeniably need extensive research attention and systematic exploration. Aging performance is directly related to the lifetime and reliability of cables. In this study, the electrical treeing and thermal aging phenomena of 70wt.% linear low-density polyethylene (LLDPE) and 30wt.% high-density polyethylene (HDPE) blends (abbreviated as 70L-30H) were studied and compared with those of XLPE by investigating the microstructural feature, electrical treeing behavior, and mechanical performance during thermal aging. Electrical treeing tests show that 70L-30H blends exhibited smaller treeing dimensions and lower electrical tree growth rates than those of XLPE. Thermal aging tests exhibit that the mechanical property degradation of 70L-30H blends is less than that of XLPE under the same aging time. Through differential scanning calorimetry analysis and microstructure observation, the 70L-30H blend shows higher melting temperature, thicker lamellae, and higher crystallinity with a uniform and fine spherulite structure, which are responsible for good anti-aging performance. This study indicates that the blends exhibit better electrical and thermal aging resistance than XLPE, which provides a performance guarantee for its further application in the non-crosslinked cable system.

Carbon Nanotube Migration in Melt-Compounded PEO/PE Blends and Its Impact on Electrical and Rheological Properties.

In this work, the effects of MWCNT concentration and mixing time on the migration of multi-walled carbon nanotubes (MWCNTs) within polyethylene oxide (PEO)/polyethylene (PE) blends are studied. Two-step mixing used to pre-localize MWCNTs within the PE phase and subsequently to observe their migration into the thermodynamically favored PEO phase. SEM micrographs show that many MWCNTs migrated into PEO. PEO/PE 40:60 polymer blend nanocomposites with 3 vol% MWCNTs mixed for short durations exhibited exceptional electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity (14.1 dB and 22.1 S/m, respectively), with properties dropping significantly at higher mixing times, suggesting the disruption of percolated MWCNT networks within the PE phase. PE grafted with maleic anhydride (PEMA) was introduced as a compatibilizer to arrest the migration of MWCNTs by creating a barrier at the PEO/PE interface. For the compatibilized system, EMI SE and electrical conductivity measurements showed a peak in electrical properties at 5 min of mixing (15.6 dB and 68.7 S/m), higher than those found for uncompatibilized systems. These improvements suggest that compatibilization can be effective at halting MWCNT migration. Although utilizing differences in thermodynamic affinity to draw MWCNTs toward the polymer/polymer interface of polymer blend systems can be an effective way to achieve interfacial localization, an excessively low viscosity of the destination phase may play a major role in reducing the entrapment of MWCNTs at the interface.

Influence of Quaternary Ammonium Salt Functionalized Chitosan Additive as Sustainable Filler for High-Density Polyethylene Composites.

In this study, an antimicrobial packaging material was successfully developed with blends of high-density polyethylene (HDPE) and chitosan (CS) made by melt processing. In the different HDPE/CS composites, the CS content effect (up to 40%), and the addition of quaternary ammonium salt functionalized chitosan (CS-CTAB) as an additive were evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile strength, scanning electron microscopy (SEM) and antimicrobial activity. When analyzing the effect of the additive in the different HDPE/CS composites, it was observed that the compositions with 10 and 20 %wt of chitosan showed better elongation values (~13% and 10%) as well as a higher decomposition temperature at 20% mass loss (T20) varying from (321-332 °C and 302-312 °C), respectively, in relation to the other compositions, regardless of the type of additive used, it acted as an antimicrobial agent, promoting inhibition of microbial growth against the strains gram-positive and gram-negative used in this work, making the different HDPE/CS composites suitable candidates for use in food packaging.

Effects of film tension and contamination on the seal quality of flexible food packaging films made of polypropylene and low density polyethylene blends containing talc filler

Seal integrity and seal strength are important requirements in the heat sealing of flexible packaging. In this article, the influence of talc compounds and different process parameters, such as film tension and contamination on the sealant films consisting of polypropylene and low‐density polyethylene blend were investigated. According to the results, increasing the talc ratio from 0% wt to 30% wt positively influenced both hot and cold seal strength. Among different polymer blends having same talc ratio, the sample having the lowest melt flow index (2.84 dg/min at 230°C and 2.16 kg) showed the highest cold seal strength with 9.07 N/25 mm. On the other hand, in the samples with higher melt flow indexes, less seal integrity issues were observed in the presence of contaminants. Elevated film tensions from 0 to 0.4 N/mm2 enhanced the seal strengths significantly at the seal initiation temperatures of each film. However, this situation changed at higher operating temperatures due to the increased orientation and brittleness. Besides, in the presence of contaminant coffee particles at the seal interphase, high film tensions adversely affected the seal integrity since the average leakage increased 2.7% for samples A and B, and 7.4% for sample C. In summary, it has been shown that talc incorporation can improve seal strength, high MFI can fill the gaps at the seal interphase and the high levels of film tension (above 0.16 N/mm2) during sealing as well as the contamination need to be avoided to ensure integrity sealing.

Compatibilization of Recycled Polypropylene with Polyethylene Blends Via Ionic Liquid to Enhance Mechanical Properties

Polypropylene (PP) is the world's second-largest plastic resin based on production volume, after polyethylene (PE). In 2021, the global production volume of PP amounted to 80 million tons. Less than 2% of total produced PP is recycled annually. PP is sensitive to mixed polymers, and a minor amount of other polymeric contaminants reduces physical properties (Figure 1). To increase the recyclability of PP, there is a specific need to have additives that upcycle. PP represents the most significant opportunity in increasing recycling rates. Ionic liquids (ILs) are universal solvents and can promote compatibilization among different polymers. RoCo has developed several ILs that are non-toxic, and when mixed with polyolefins, they enhance the dispersion of fillers and improve mechanical properties thus opening doors to upcycling of recycled polymers. We have been evaluating the recycling of PP by using ionic liquids. We will be sharing our data on ILs compatibilizer results in retaining and enhancing the mechanical properties of PP even when mixed with 15% PE. Both the tensile and impact properties were improved resulting in upcycling of PP. We are in the process of investigating additional properties such as conductivity and surface properties.

Development and Characterization of LLDPE Blends with Different UHMWPE Concentrations Obtained by Hot Pressing.

To modify its characteristics, expand its applicability, and, in some cases, its processability, new blends using ultra-high-molecular-weight polyethylene (UHMWPE) have been developed. In this study, three different formulations of linear low-density polyethylene (LLDPE) and UHMWPE blends were prepared with 15, 30, and 45% (% w/w) UHMWPE in the LLDPE matrix. All mixtures were prepared by hot pressing and were immersed in water for one hour afterwards at a controlled temperature of 90 °C to relieve the internal stresses that developed during the forming process. The thermal characterization showed that the blends showed endothermic peaks with different melting temperatures, which may be the result of co-crystallization without mixing between the polymers during the forming process. The mechanical characteristics presented are typical of a ductile material, but with the increase in the percentage of UHMWPE, there was a decrease in the ductility of the blends, as the elongation at rupture of the blends was higher than that of the pure components. The morphologies observed by SEM indicate that there were two phases in the blends. This is the result of the system’s immiscibility due to the mode of preparation of the blends, wherein the two polymers may not have mixed intimately, confirming the results found with the thermal analyses.