Virgin Linear Low Density Polyethylene Research Articles

Evaluating Effectiveness of Multi-Component Waste Plastic Bags on Bitumen Properties: Physical, Rheological, and Aging.

This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to identify the type of plastics and the level of impurity. Asphalt binder performance was examined for rutting, thermal, and age resistance. The results revealed that the waste plastic bags, predominantly consisted of Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) and contained 6.1% impurities. The binder tests indicated that the waste plastic bags enhanced the rutting resistance of bitumen by one grade, with its modification more similar to LLDPE, rather than LDPE. The thermal degradation and aging properties of the modified binders demonstrated that the bitumen modified by the waste plastic bags exhibited slightly lower resistance to temperature and aging compared to virgin LDPE and LLDPE. This was attributed to the impurities contained in the waste plastic. In conclusion, the analyzed waste plastic bags proved to be suitable for use in binder modification, presenting a viable alternative to virgin LLDPE.

Optimizing the blending ratio and processing parameters for ternary blends of recycled polypropylene with recycled high and virgin linear low-densities polyethylene

The thermoplastic polymer of polypropylene (PP) is employed in many different applications. A huge amount of PP waste is produced by using its discarded parts. Recycled polypropylene (rPP) does not provide virgin properties and further reuse causes more loss of properties. This study investigates experimentally the effect of adding different ratios of recycled high-density polyethylene (rHDPE) and virgin linear low-density polyethylene (vLLDPE) with different process variables on the rPP's tensile strength. The most significant injection factors of melt temperature, injection pressure, holding pressure, holding time, and cooling time with the ternary blend ratio were proposed with three levels. Also, three different compositions of I, II and III with 85/12/3, 85/3/12, and 85/8/7 wt percent are considered respectively to the levels of the rPP/rHDPE/vLLDPE blend. Accordingly, 18 experiments are designed based on Taguchi's orthogonal array (OA) of L18. An injection molding die is designed and manufactured to produce tensile test samples. Scanning electron microscopic (SEM) is applied to show the microstructure of the blends. The response data of ultimate tensile stress are transmitted to signal-to-noise ratio (S/N) to facilitate their analysis by analysis of variance (ANOVA). Finally, the optimum set of parameters that provides the optimal blend with the highest ultimate stress of 21.62 MPa was defined. Additionally, according to the P-values the most significant parameters are holding pressure, injection pressure, and cooling time, respectively.

Into the Plastisphere, Where Only the Generalists Thrive: Early Insights in Plastisphere Microbial Community Succession

The ubiquity of plastic debris in marine environments raises the question, what impacts do plastics have on our marine microbiota? To investigate this, we applied bacterial 16S rRNA gene and fungal ITS2 region sequencing to identify changes in microbial biofilm community compositions on marine plastic, over time. We sampled biofilm on virgin linear low-density polyethylene (LLDPE), nylon-6 (PA) and glass after 2, 6 and 12 weeks of constant immersion in Te Whakaraupō-Lyttelton Harbour, Aotearoa-New Zealand. Of the prokaryotes, Proteobacteria and Bacteroidetes were predominant in all samples and Verrucomicrobiota were most abundant in mature biofilms. Microbial communities on the three substrate types were significantly distinct from those in the surrounding seawater, regardless of age, but not between attachment substrates. Bacterial communities occurring two weeks after immersion and fungal communities at six weeks were found to vary more among substrate types than at other times; however, no significant substrate-specific communities were identified overall. Taxa closely related to previously reported plastic-biodegrading species were found in very low abundance across all substrates, including on the glass slides. Our findings suggest that microorganisms do not selectively persist on the LLDPE or PA surfaces to gain significant direct metabolic benefit, instead using these plastics primarily as an attachment surface on which they form generalist biofilm communities.

Use of recycled materials as mid layer in three layered structures-new possibility in design for recycling

Challenges of using recycled polymer materials in food packaging are related both to the properties of the material and demanding safety issues for food contact materials. The aim of this research was to detect possible risks using recycled post-consumer plastic waste in three-layered polyethylene (PE) films produced with virgin outer layers and a mid-layer from recycled flexible PE material. Migration tests were performed as risk assessment for identifying possible migrating substances from the mid-recycled layer. Overall migration was determined on various 3-layered structures made from virgin low-density PE (LDPE) and virgin linear low-density PE (LLDPE), respectively, with two different recycled PE from post-consumer waste (R1 and R2). 95% ethanol was used as a simulant for screening at 20, 40 and 60 °C for 10 days. Specific migration was performed using sophisticated analytical techniques (liquid and gas chromatography). Overall migration values for all temperatures were from < 2 mg/dm2 at lowest and 5.6 ± 0.1 mg/dm2 at highest temperature, thus well below the overall migration limit (OML) of 10 mg/dm2. Specific migration of intentionally and non-intentionally added substances were detected, identified and quantified. Similarly, specific migration values were under specific migration limit (SML) defined in legislation. Optical properties of the reference samples were significantly different in appearance and on cross section for samples with recycled materials R1 compared to recycled material R2 which caused only slight changes in the appearance of both reference films. This research presents a valuable study on migration from recycled flexible PE films and use of recycled materials in food packaging applications. Use of virgin materials as outer layer in combination with commercially available recycled material can increase the use of recycled materials in packaging as well as reduce the total amount of flexible plastic solid waste.

On the Kinetics of Degradation Reaction Determined Post Accelerated Weathering of Polyolefin Plastic Waste Blends.

Polyolefin (PO) polymers constitute the majority of consumer plastic commodities. The reliance on such materials make it near imposable to avoid touching one in any given day. Therefore, the accumulation of plastic solid waste (PSW) in developed and developing societies alike requires immediate attention to manage and valorize this type of waste. In this work, PSW originating from real life sources and virgin linear low-density polyethylene (LLDPE) films were compounded in a mechanical recycling effort. The recycled blends constituted up to 100% (by weight) of the waste material. Accelerated weathering (aging) was conducted on the blends, reaching threshold limit of exposure to study the major changes occurring on the recycled blends. Thermogravimetry and differential scanning calorimetry (DSC) were used to determine their characteristics and applicability for future recycling using thermo-chemical treatment (TCT) methods. Analytical solution methods following the international committee of thermal analysis and calorimetry (ICTAC) were followed in conducting the measurements and kinetic calculations alike. A novel analytical mathematical solution model is also introduced to determine both the pre-exponential factor (Ao) and apparent activation energy (Ea) of the degradation reaction. The model proved to be a more accurate analysis tool, and the work in whole enabled the determination of future plans for using such waste components as a feedstock to thermal units.

Influential parameters on natural weathering under harsh climatic conditions of mechanically recycled plastic film specimens

In this work, real life reclaimed plastic solid waste (PSW) secured from the municipal sector was mechanically recycled and compounded with virgin linear low density polyethylene (LLDPE). The compounding of the plastic film samples utilised the means of extrusion and blown filming to produce various formulations of the blends containing up to 100% (by weight) of the PSW in the examined specimens. The film samples were compared to market products used in the State of Kuwait where PSW accumulation presents a major obstacle. Natural weathering under arid and harsh climatic conditions was also performed to determine the degradation extent of the film samples. Haze (%), light transmission (%) and the total change in colour (ΔE) were measured as indicators to the degradation profile of the polymeric materials, in addition to tensile pull mechanical properties. Properties were noted to deteriorate as a function of weathering time and waste content. Statistical analysis was also performed on the properties measured and climatic conditions including airborne pollutants levels. The abundance of the secondary airborne pollutant (ozone) was determined to be a significant variable on the studied properties. This can be attributed to induced photo-oxidation the polymeric matrix is subjected to under such climatic conditions which increases oxygen diffusion throughout the polymeric matrix. Future development of the recycled blends studied in this work can be a route for the decrease of associated environmental stressors with virgin plastic resin conversion.

The Usage of Recycled Material in Rotational Molding Process for Production of Septic Tank

Rotational molding is the forming process that use in produce large product, complexity product and hollow product with the limitation of process ability and material. Most of the rotational molding is a large product with a longer useful life compare to other technique, so to reused the material from other process can help to increase the competition of rotational molding in the market. This paper chooses recycled HDPE from blowing process due to it generally used by the market and not difficult to find. So in this paper choose to studies the blend of virgin LLDPE (linear low density polyethylene) and recycled HDPE (high density polyethylene) for application in septic tank by rotational molding process. Various ratio of blending were investigated to find the morphology, mechanical properties and the relation of melt flow rate and rheology. Mechanical properties are generally referred to tensile test, hardness test, impact strength and Morphology by Scanning Electron Microscope. Many studies have carried out to investigate about rotational molding forming process control, mold and process condition, some on material ability and new material to used in rotational molding to improve the mechanical properties and various technique in forming by rotational molding. But this article will investigated more about the use of recycled material from other forming technique process (which refer to blowing process in this article) to use in rotational molding process for produce septic tank compare to the commercial quality.

Deterioration of irradiation/high-temperature pretreated, linear low-density polyethylene (LLDPE) by Bacillus amyloliquefaciens

A Bacillus amyloliquefaciens strain was isolated from composted plastics and identified using microbial identification system BIOLOG and 16S rDNA sequences. The capability to attack virgin and ɣ-irradiation/high temperature-pretreated LLDPE films was investigated for comparison to evaluate the effect of pretreatment. A biodeteriorating effect characterized by low weight reductions of 1.1 ± 0.3 to 3.2 ± 1.3% was observed with the pretreated LLDPE within 40–60 days. The precision of the gravimetric method was sometimes negatively affected by the fragmentation of plastic films during the biological treatment or by traces of microbial biofilm firmly adhering to the plastic material. FTIR spectra before and after 60-day treatment indicated a decrease of carbonyl band and flattening of the 1300-1100 cm−1 zone due to bacterial action. GPC showed an increase of Mn and Mw of 2300–3700 and 32 200–35 500 g mol−1, respectively, and a decrease of polydispersity index suggesting presence of low molar weight LLDPE oligomers in pretreated LLDPE. The analysis of crystallinity and melting enthalpy detected the removal of oligomers during biodeterioration. ESI-MS analysis of the medium after 60-day biotreatment of pretreated LLDPE showed a presence of 3-hydroxybutyrate oligomers linked to the disappearance of low molar weight LLDPE oligomers that was not observed with virgin LLDPE. Coincidence of the removal of LLDPE oligomers and the appearance of 3-hydroxybutyrate oligomers suggested metabolization of low molecular LLDPE fractions present in the pretreated LLDPE by B. amyloliquefaciens. The experiments with virgin LLDPE demonstrated a positive effect of the pretreatment.

Non-isothermal degradation kinetics of virgin linear low density polyethylene (LLDPE) and biodegradable polymer blends

The thermal degradation kinetics of several polymers, including biodegradable blends were investigated in non-isothermal thermogravimetry using several analytical methods. Virgin linear low density polyethylene (LLDPE) and LLDPE blends with polystarch-N (PSN), a prodegradant starch additive material used in 20 and 40 wt%., were investigated to determine the degradation behaviour of such materials in pyrolysis conditions. The results were compared to those obtained with virgin low (LDPE) and high density polyethylene (HDPE). An analytical solution model was also developed to assess the two degradation steps of the biodegradable blends which enabled the assessment of the apparent activation energy (Ea) of each material in the blend on its own based on the initial and final degradation temperatures. It was observed that the thermal behaviour and Ea value didn’t change significantly with the increase of biodegradable prodegradant, which shows that biodegradable blends can be treated with similar conditions regardless of the content of the biodegradable masterbatch present in the blend.

Investigating the effect of accelerated weathering on the mechanical and physical properties of high content plastic solid waste (PSW) blends with virgin linear low density polyethylene (LLDPE)

In developing countries, plastic solid waste (PSW) poses a serious threat due to the increase in the dependency on landfilling as well as other environmental issues. Hence, valorising the accumulated waste is essential to promoting more environmentally friendly practices. In this work, the mechanical and physical properties of virgin linear low density (LLDPE) and LLDPE blends with PSW are reported. The formulations studied contained the following virgin to waste ratios (wt.%/wt.%): 100/0, 75/25, 50/50, 25/75 and 10/90. The effect of photo-degradation on the studied specimens was investigated using accelerated weathering tests in a UV chamber. Young's modulus showed an increase with exposure duration due to change in the samples' crystallinity. The loss of mechanical integrity (i.e. stress and strain at rupture) of the samples studied was related to the photo-degradation mechanisms, namely cross-linking and photo-oxidation. Haze and light transmission measured indicated that there was a loss of the amorphous regions in the samples studied after about 200 h of continuous exposure. The total change in colour (ΔE) was estimated but did not show a clear trend, indicating a clear dependency on wash mechanism and continuous loss of polymer colour and degradation.

Structure development and melt viscoelastic properties of PE/organoclay nanocomposite blown films

AbstractThe effects of compatibilizer and the type of polyethylene (PE) matrix on structure development of PE/organoclay nanocomposite samples were investigated by means of X‐ray diffraction technique and transmission electron microscopy in conjunction with melt viscoelastic measurements. It was shown that the presence of compatibilizer plays a key role in determining the extent of intercalation and resulting structure development in both linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE). The LLDPE/organoclay nanocomposite samples exhibited a pronounced low‐frequency nonterminal storage modulus whose values were found to be greater than those of LDPE/organoclay nanocomposite samples. The percentage increase in storage modulus values for the compatibilized LLDPE/organoclay nanocomposite sample compared to the virgin LLDPE sample was 1080, while the percentage increase in storage modulus values for the compatibilized LDPE/organoclay nanocomposite sample compared to the virgin LDPE sample was 200, at frequency 0.1 s−1. The melt viscoelastic measurements performed on the nanocomposite blown film samples indicated that at higher draw‐down ratio the organoclay platelets and/or tactoids were aligned in the flow direction. Comparing the melt viscoelastic results obtained for annealed and unannealed nanocomposite blown film samples, it was demonstrated that the reorientation of the induced organoclay alignment, which led to network structure formation in the amorphous phase of PE, is very slow, and the time required to complete the reorientation was found to be longer than 3 h at annealing temperature (100°C). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Analysis of thermal properties and rheological behavior of LLDPE/EPDM and LLDPE/EPDM/SRT mixtures

Linear low-density polyethylene (LLDPE) and ethylene–propylene–diene terpolymer (EPDM) blends, with and without scrap rubber tire (SRT), has been prepared in a single-screw extruder with a temperature profile of 180/190/200/200/210 °C. The thermal behavior of virgin LLDPE and the extrusion products have been characterized by differential scanning calorimeter (DSC), and the rheological behavior also has been determined. It was observed that when EPDM is partially replaced by SRT, LLDPE/EPDM/SRT mixtures do not show, at first, an expressive diminution in the crystallization temperature ( T c), crystallinity (%χ), heat of crystallization (Δ H c) and melting temperature ( T m) values. SRT also does not impose substantial increase in the elastic modulus ( G′), viscous modulus ( G″) and complex viscosity ( η*) values of LLDPE/EPDM/SRT mixtures. The possible formation of a composite of SRT–EPDM particles is suggested as reason for these results.

Morphology and thermal stabilization mechanism of LLDPE/MMT and LLDPE/LDH nanocomposites

The morphology and thermal stabilization mechanism of polymeric nanocomposites prepared by solution intercalation of linear low density polyethylene (LLDPE) with montmorillonite (MMT), MgAl layered double hydroxide (LDH), and ZnAl LDH have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Both LLDPE/MMT and LLDPE/MgAl LDH nanocomposites exhibit mixed intercalated–exfoliated structures, whereas the LLDPE/ZnAl LDH nanocomposites exhibit completely exfoliated structures because the ZnAl LDH layers can be easily broken during the refluxing process. All nanocomposites show significantly enhanced thermal stability compared with virgin LLDPE due to the increases of the effective activation energy ( E α ) during degradation process. However, LDHs nanocomposites show much higher thermal degradation temperatures than MMT nanocomposites with the same filler content because they have much higher E α than MMT nanocomposites at the early degradation stage. The data of real time FTIR spectroscopy and morphological evolution reveal a catalytic dehydrogenation effect presents in MMT nanocomposites, which may decrease the E α of degradation and thermal stability of MMT nanocomposites.

A novel processing aid for polymer extrusion: Rheology and processing of polyethylene and hyperbranched polymer blends

The use of hyperbranched polymers (HBPs) as a processing aid for linear low density polyethylene (LLDPE) was investigated. Various generation (or pseudo-generation) HBPs were used which had either 16 carbon atom alkanes or a mixture of 20/22 carbon atom alkanes on the end groups. In addition, the degree of end group substitution was studied. Blends of up to 10% HBP content were mixed via extrusion at 170 °C to produce 1 mm diameter fibers. Processability, surface appearance and the rheological properties of the blends were evaluated. It was found the power requirement for extrusion was significantly decreased as a result of reduced blend viscosity, and also, the mass flow rate for a given extruder speed was greater than virgin LLDPE for all HBP blends. Melt fracture and sharkskin of the blends was successfully eliminated, and minimal preprocessing time was required for the effect to take place. Surface analysis using x-ray photoelectron spectroscopy and transmission electron microscope techniques were performed with both showing that the HBP had a preference to accumulate at the fiber surface. Rheological experiments were similarly affected, therefore, the blend viscosity is really a composite of a HBP rich phase and a neat LLDPE phase. It is hypothesized that the HBP rich phase acted as a lubricating layer at the polymer/die wall interface. The HBP with a greater degree of end group substitution acted better as a processing/rheological property aid. Blends of LLDPE and paraffin wax were also studied. The surface appearance of HBPs/LLDPE blends was superior to those blends mixed with paraffin wax, as was the extruder performance. The results suggest that HBPs, at trace levels (≈500 ppm), may offer a number of advantages when used as a processing aid for LLDPE.

Steady-state bulk trap-modulated hopping conduction in doped linear low-density polyethylene

A mathematical model is developed for trap-modulated, steady-state, hopping transport of space-charge-limited carriers, injected into linear low-density polyethylene, doped with oxidized low-density polyethylene. Poole field lowering of the trap depth is also included. The hopping sites are carbonyl groups provided by the dopant, lying in the amorphous regions of the sample. We assume band-tail or band conduction, i.e., little or no energy barrier to transport within the crystalline regions, and deep traps located at the crystalline-amorphous matrix boundaries. Two adjustable parameters, the hopping and trap site separations, are used to give good agreement with the experimental current-applied field characteristics in the temperature range 50–85 °C for fields less than 4×105 V/cm, and hopping site concentrations of 2×1019/cm3 and 4×1019/cm3. For the latter concentration, (corresponding to a separation of about 28 Å) at temperatures (35–60 °C) that are too low to thermally detrap injected carriers (that are trapped before reaching the steady state), conduction takes place by hopping in the amorphous regions over an energy barrier of 0.30 eV. At elevated temperatures (60–85 °C), detrapping contributes to the steady-state current. The activation energy in this latter temperature range is 1.17 eV (at 2×105 V/cm). The final current, field, and temperature equation shows that the hopping and trap energies are additive on a semilog plot of I/T vs 1/T. Thus, the field-lowered trap depth is 0.87 eV. This result agrees well with a previously determined crystalline-amorphous trap depth in virgin linear low-density polyethylene.

Use of grafted aspen fibers in thermoplastic composites: IV. Effect of extreme conditions on mechanical properties of polyethylene composites

AbstractHardwood fibers of aspen in the form of chemithermo‐mechanical pulp (CTMP) have been used as reinforcement in linear low density polyethylene (LLDPE). The effect of composite treatment (immersion in boiling water, heat exposure at 105°C for seven days or at a temperature of −40°C) on resulting mechanical properties were evaluated. The grafted aspen CTMP composites showed by far the best results with regard to secant modulus, tensile strength, energy, and strain when compared to those of wood flour, mica or glass–fiber filled LLDPE, as well as to virgin LLDPE. Finally, the dimensional stability of CTMP aspen‐filled LLDPE composites immersed for four hours in boiling water was better than that of mica or glass–fiber filled LLDPE.