Linear Low-density Polyethylene Research Articles

Degradation of HDPE, LLDPE, and blended polyethylene geomembranes in extremely low and high pH mining solutions at 85 °C

The durability of five 1.5-mm thick geomembranes (GMBs) is investigated in pH 0.5 and 13.5 synthetic mining solutions using immersion tests. Two high density polyethylene (HDPE), two linear low density polyethylene (LLDPE), and one blended polyethylene (BPO) GMBs are investigated at 85 °C for incubation durations of 4.5–6.5 years. It is shown that the degradation of all five GMBs in the high pH solution is faster than in the low pH solution. In the pH 0.5 solution, one of the HDPEs and the BPO GMBs exhibited polymer degradation before or at the time of the depletion of their antioxidants. In pH 13.5, four out of the five GMBs exhibited degradation and followed the conceptual three-stage degradation model until nominal failure. However, there is no correlation between the long-term performance of these GMBs and their resin type or their initial properties since one of the examined LLDPEs outperformed all the higher density/crystallinity GMBs with higher initial properties while the other LLDPE did not perform well. Thus, when selecting a GMB for a desired application, the relative performance of different candidate GMBs can be only assessed using immersion tests using the solutions expected in the field.

Functionalized Poly(ethylene-octene)/Linear Low-Density Polyethylene Prepared by Melt Free-radical Grafting Reaction and Its Potential in Toughening Poly(butylene terephthalate) Resins

Glycidyl methacrylate (GMA) and styrene (St) were used as the graft monomer and co-graft monomer, respectively, and grafted onto poly(ethylene-octene) (POE) and linear low-density polyethylene (LLDPE) to prepare a series of GMA-functionalized (POE/LLDPE)-g-(GMA-co-St) graft copolymers. The copolymers were then blended with poly(butylene terephthalate) (PBT) to produce PBT/(POE/LLDPE)-g-(GMA-co-St) blends. The effects of grafting factors and copolymer content on the mechanical properties, thermal properties, rheology, morphology, and deformation mechanism of the blends were studied in detail. The results showed that GMA and St were successfully grafted onto the molecular chains of POE and LLDPE. In the grafting reaction, the best grafting degree and comprehensive performance were achieved when the amounts of dicumyl peroxide and GMA were 0.3 and 5 wt %, respectively, the mass ratio of GMA to St was 1:2, and the screw rotation speed was 60 rpm. By introducing graft copolymers into the PBT matrix, the toughness and thermal stability of the blends were improved. At the same time, the crystallinity and fluidity decreased, and the blends possessed the best mechanical properties when the copolymer content was 20 wt %, with the elongation at break and notched impact strength increasing to 409.98% and 945.90 J/m, respectively. Scanning electron microscopy analysis showed that the copolymers were uniformly dispersed in the PBT matrix. The principal toughening mechanisms were the shear-yielding properties of the PBT matrix and cavitation of (POE/LLDPE)-g-(GMA-co-St) phases.

Application of the ramp test from a closed cavity rheometer to obtain the steady-state shear viscosity η(γ̇)

Abstract The steady-state shear viscosity η ( γ ̇ ) \eta (\dot{\gamma }) is required in controlling processing parameters for the extrusion processing of polymer melts. A new method, the so-called ramp test, is investigated in this study to obtain the steady-state shear viscosity with a closed cavity rheometer (CCR). To verify the method and the accuracy of the CCR data, three commercial polyolefin polymers, a low-density polyethylene (LDPE), a linear low-density polyethylene (LLDPE), and a polybutadiene (PBD), were used as model systems. Measurements of the magnitude of the complex viscosity ∣ η ⁎ ( ω ) ∣ | {\eta }^{\ast }(\omega )| were compared with the steady-state shear viscosity data obtained by capillary rheometer and CCR. Further, time–temperature superposition master curves of the magnitude of the complex viscosity and steady-state shear viscosity obtained by CCR were developed for LLDPE and PBD. The influence of the cavity sealing on the instrument’s accuracy to obtain the steady-state shear viscosity was investigated using the finite element method simulations. Thus, it was shown that the ramp test performed by CCR is a practical method to determine reliable and reproducible data of the steady-state shear viscosity within a wide range of temperatures (T = 50–180°C) for low and high viscous materials ( ∣ η ⁎ ( ω ) ∣ | {\eta }^{\ast }(\omega )| = 1.6–480 kPa s, M w = 144–375 kg mol−1).

Improved balance between dimensional stability, mechanical properties and processability of linear low density polyethylene for rotational molding

AbstractThe linear low density polyethylene (LLDPE) products made by rotational molding (RM) usually involve two main problems of poor dimensional stability and insufficient mechanical properties. Although the decline in thermal expansion coefficient and rise in mechanical strength can be attained by filling with inorganic particles, the melt fluidity of LLDPE, which is of great importance for RM, would be significantly reduced. In this study, a combination of crosslinker low‐temperature blending and partial chemical crosslinking strategy is employed to enhance the dimensional stability and mechanical properties of LLDPE without sacrificing the melt fluidity. The structure–property relationships in the crosslinked specimens are analyzed based on X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and dielectric spectrometry. The results show that our simple, low‐cost and universal strategy not only contributes to a better dimensional stability and significantly improved mechanical properties, but also endow the samples with promising processability and thermal stability.

Decoupling the interplay of polymer properties and particle size in stability of co-continuous blend composites

Interfacially localizing particles in co-continuous polymer blends requires a complex interplay between the properties of polymers, such as interfacial tension between them, Γ, viscosity, η, viscosity ratio between them, and particle properties, such as particle size and particle surface chemistry. Here, we investigate the formation and coarsening dynamics of four co-continuous blend composites based on polypropylene, PP (or linear low-density polyethylene), and poly(ethylene-co-vinyl acetate), EVA filled with pristine silica of two sizes (140 and 250 nm). By choosing polymer blend components with different viscosities and interfacial tensions and particles with varying size and size distributions, we were able to elucidate their relative contributions in the stabilization of co-continuous polymer microstructures. By utilizing confocal rheology, we show that the evolution of storage modulus during coarsening of polymer blend composites is primarily dependent on the strength of the initial interfacial particle network. Our findings indicate that the initial domain size and kinetic control of interfacial particle localization in co-continuous polymer blends are determined by the Γ/η ratio of the neat blend. However, this relationship does not hold in low viscosity systems. When polymer blend viscosity is lower, it reduces the kinetic barrier at the interface, leading to a higher proportion of particles localizing in the favorable EVA phase. We also find that the smaller particles have a higher propensity for interfacial localization. These findings provide insight into the success of kinetic particle trapping at the interface of co-continuous blends and the resulting composite properties based on the choice of component properties.

Acidic Influence in Conversion of Hospital Plastic Waste into Liquid Fuel using Kaolin Base-supported Catalysts

Assessing acidic influence in conversion of hospital plastic waste into liquid fuel with kaolin base supported catalysts was carried out using samples collected from a tertiary University teaching Hospital Sokoto, which encompassed Drip bags (Linear low density polyethylene LLDPE), Hand gloves (Polyethylene terephthalate PET) and Urine bags (Polyureathane PU). Uncatalyzed pyrolysis was first carried out using thermal cracking only at 300, 350, and 4000C. Catalyzed pyrolysis was also carried out using three different active catalyst mounted on same support and equal catalytic ratio of active catalyst to support. CuO/Kaolin-SO4, FeO/Kaolin-SO4 and CaO/Kaolin-SO4. The liquid fuel obtained from uncanalyzed and catalyzed pyrolysis of the sample were all subjected to GCMS and FTIR analysis. Uncatalyzed pyrolysis was first carried out using thermal cracking only at 300, 350, and 4000C. Catalyzed pyrolysis was also conducted using three different active catalyst mounted on same support and equal catalytic ratio of active catalyst to support. Fe2O3/Kaolin-SO4 (CAT.D), CuO/Kaolin-SO4 (CAT.E), and CaO/Kaolin-SO4 (CAT.F). The catalytic activities of all the three synthesized catalysts were successfully tested in the conversion of hospital plastic waste in to liquid fuel. However the conversion using (CAT.D) was found to be more promising and selective to liquid fraction then followed by CAT. E and F. Therefore, the results shows that CAT.D has lower cocking tendency that result to high liquid than the other catalysts. The FTIR and GC/MS analysis revealed that the chemical composition and carbon number distribution of the liquid fraction which indicate the presence of paraffinic, naphthenic and olefins hydrocarbons as the dominant component in the liquid fraction obtained, and high amount of lower hydrocarbon range was also obtained using CAT.D. Thus, sulphated kaolin catalyst (CAT.D) was found to be better in modifying the product than CAT.E and F.

Effect of alkali treated groundnut shell powder in the basalt fiber reinforced polyethylene hybrid composites: A sustainable approach towards green composites

AbstractWith the widespread use of natural polymers in composites, advances in mechanical, thermal, and thermomechanical characteristics have become necessary. This study explores, the hybridizing effect of alkali‐treated groundnut shell powder (T‐GSP) to the basalt fiber (BF) reinforced linear low‐density polyethylene (LLDPE) composites in different weight fractions. Twin screw extrusion machines were used to mix fresh LLDPE matrix with various weight fractions of T‐GSP particles (0, 5, 10, and 15 wt%) and 20 wt% of fresh BF. It has been found to be that adding up to 15 wt% of T‐GSP with 20 wt% of fresh basalt fibers in the LLDPE matrix produced better results in the mechanical, thermal, and thermomechanical properties of the hybrid composites. FE‐SEM analysis was performed on the tensile fracture surfaces of the hybrid composites to determine the effect of the T‐GSP particles on the wettability and interfacial adhesion of the fiber and the LLDPE matrix. Likewise, mechanical properties of 15 wt% of T‐GSP with 20 wt% of BF hybrid composite reported an increment of 76.39% and 397.05% in tensile strength and modulus, 230.88% and 324.70% in flexural strength and modulus. Also, a decrement of 14.32% in impact strength of the hybrid composites was reported compared to fresh LLDPE polymer. Shore D hardness testing recorded a 27% increment in hardness, while TGA and DSC reported a reduction in degradation temperature and an increment in crystallization and melting temperature of the fabricated composites. dynamic mechanical analysis (DMA) shows an increment in the glass transition temperature of all the composites.

Polyethylene Slurries: Swelling and Solubility

AbstractThe solubility of different alkanes in polyethylene (PE) of different densities, as well as the solubility of the polymers in the alkanes, and the degree of swelling of the powders are studied as a function of temperature. It is found that the solubility of linear low‐density polyethylene (LLDPE) is as much as 6 times greater than that of high‐density polyethylene (HDPE) at the same temperature, and that LLDPE swells at least 50% more than HDPE the same diluent at the same temperature. The breakthrough curves also show that lighter alkanes swell the PE more at a given temperature than heavier ones. Also, the breakthrough points (the temperature at which the swelling versus temperature curves change slope) occur at lower temperatures for PE of lower density. Gel formation is observed for medium and low density polyethylenes in pentane and hexane. This quantitative information will be useful in developing process models for different industrial polymerization processes, as particle swelling can have a significant impact on slurry viscosity and the flow stability and solids loading of commercial reactors.

Catalyst-mediated pyrolysis of waste plastics: tuning yield, composition, and nature of pyrolysis oil

With ever-increasing plastic waste, a robust and sustainable methodology to valorize the waste and tweak, the composition of the value added product is the need of the hour. The present study describes the effect of different heterogeneous catalyst systems on the yield, composition and nature of the pyrolysis oil produced from various waste polyolefins like high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP). The waste polyolefins were subjected to thermal as well as catalytic pyrolysis. Liquid, gas, and solid products were obtained during the pyrolysis. Various catalysts such as activated alumina (AAL), ZSM-5, FCC catalyst, and halloysite clay (HNT) were used. Usage of catalysts has reduced the temperature of the pyrolysis reaction from 470 to 450°C with better liquid product yield. PP waste generated higher liquid yield compared to LLDPE and HDPE waste. The highest liquid yield of 70.0% was achieved with PP waste using AAL catalyst at 450°C. The sulfur and chloride content was found to be < 10 and < 20ppm respectively in all the pyrolysis liquid. Pyrolysis liquid products were analyzed using gas chromatography (GC), nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray fluorescence (XRF) spectroscopy, and gas chromatography coupled with mass spectrophotometry (GC-MS). The obtained liquid products consist of paraffin, naphthene, olefin and aromatic components. Catalyst regeneration experiments with AAL showed that the product distribution profile remains the same up to three cycles of regeneration.

Process Simulation Modeling of the Linear Low-Density Polyethylene Catalytic Pyrolysis in a Fluidized Bed Reactor

In this work, a comprehensive process simulation was developed to study and predict the pyrolysis of linear low-density polyethylene (LLDPE) in a fluidized bed reactor (FBR). The comprehensive simulation operated at 600 and 700 °C to investigate the pyrolytic oil and wax yields. These products were chosen as they mimic fuel range products available as a renewable fuel and energy source. The results showed that the oil yield decreased from 600 to 700 °C. This is because of an increase in the polyolefin polymer matrix’s vibration leading to an increase in temperature and absorbed thermal energy. In addition, there is a higher gas yield produced and negligible wax formation at 700 °C, which is beneficial in controlling accrued plastic waste (PW), of which polyethylene (PE) represents a vast proportion of via thermo-chemical conversion (TCC) technologies. The detailed process simulation was compared with experimental data under the same technology and operating conditions, and it was found that less than 10% discrepancy was observed between the two sets of data, suggesting a good validation between the two studies. Further studies showed that the diesel fuel lumped hydrocarbon (HC) range (C10–C19) was between 40 and 63% in the pyrolysis oil yield obtained. Moreover, the temperature profiles and fluidized bed distributor parameters were compared and investigated. The current simulation has proven that it can successfully predict the pyrolysis of LLDPE in an FBR.

Mechanical Properties of Metallocene Linear Low-Density Polyethylene Mulch Films Correlate with Ultraviolet Irradiation and Film Thickness

Mulching technology has created a major problem of agricultural plastic pollution. This is because the mulch is severely degraded by UV (ultraviolet) irradiation and the mechanical properties deteriorate, which makes mechanical recycling or manual recycling difficult. This study was conducted on m-LLDPE (metallocene linear low-density polyethylene) mulch films. The difference in mechanical properties of specimens in the TD (transverse direction) and PD (parallel direction) was investigated, and the changes in the mechanical properties after UV irradiation were compared. Finally, an initial mulch mechanical property evaluation model was developed to adapt to different recovery machines and crop agronomic requirements. The results suggest that the mechanical properties of m-LLDPE mulch films were strongly influenced by the film thickness, and also showed directional differences in tensile and tear properties. After UV irradiation, the mechanical properties of the specimens were enhanced after a short period of time, but the overall trend was a non-linear decay which gradually slowed down with time.

Development of plastic-degrading microbial consortia by induced selection in microcosms.

The increase in the production of highly recalcitrant plastic materials, and their accumulation in ecosystems, generates the need to investigate new sustainable strategies to reduce this type of pollution. Based on recent works, the use of microbial consortia could contribute to improving plastic biodegradation performance. This work deals with the selection and characterization of plastic-degrading microbial consortia using a sequential and induced enrichment technique from artificially contaminated microcosms. The microcosm consisted of a soil sample in which LLDPE (linear low-density polyethylene) was buried. Consortia were obtained from the initial sample by sequential enrichment in a culture medium with LLDPE-type plastic material (in film or powder format) as the sole carbon source. Enrichment cultures were incubated for 105 days with monthly transfer to fresh medium. The abundance and diversity of total bacteria and fungi were monitored. Like LLDPE, lignin is a very complex polymer, so its biodegradation is closely linked to that of some recalcitrant plastics. For this reason, counting of ligninolytic microorganisms from the different enrichments was also performed. Additionally, the consortium members were isolated, molecularly identified and enzymatically characterized. The results revealed a loss of microbial diversity at each culture transfer at the end of the induced selection process. The consortium selected from selective enrichment in cultures with LLDPE in powder form was more effective compared to the consortium selected in cultures with LLDPE in film form, resulting in a reduction of microplastic weight between 2.5 and 5.5%. Some members of the consortia showed a wide range of enzymatic activities related to the degradation of recalcitrant plastic polymers, with Pseudomonas aeruginosa REBP5 or Pseudomonas alloputida REBP7 strains standing out. The strains identified as Castellaniella denitrificans REBF6 and Debaryomyces hansenii RELF8 were also considered relevant members of the consortia although they showed more discrete enzymatic profiles. Other consortium members could collaborate in the prior degradation of additives accompanying the LLDPE polymer, facilitating the subsequent access of other real degraders of the plastic structure. Although preliminary, the microbial consortia selected in this work contribute to the current knowledge of the degradation of recalcitrant plastics of anthropogenic origin accumulated in natural environments.

Crystal and morphology development in immiscible nonpolar polymer blend nanocomposite based on low‐density polyethylene and linear low‐density polyethylene in presence of clay and compatibilizer

AbstractIn this work, polyolefin‐blend/clay nanocomposites based on low‐density polyethylene (LDPE), linear low‐density polyethylene (LLDPE), and organically modified clay (OC) were prepared by melt extrusion. Various grades of maleic anhydride (MA) grafted polyethylene (PE‐g‐MA) were used and examined as compatibilizers in these nanocomposites. Differential scanning calorimetry analysis showed that OC and compatibilizer affect the crystallization behavior of LDPE/LLDPE with different mechanisms. Thermodynamic calculations of wetting coefficient based on interfacial energy between OC, LD, and LL, Morphological characterization based on field emission scanning electron microscopy, X‐ray diffraction, small angles X‐ray scattering, and dynamic rheology measurements revealed that the compatibilizer and OC were localized at the interface of LDPE and LLDPE phases with a preferred tendency toward one phase. Results demonstrated that at a specific amount of OC, there is an optimum compatibilizer concentration to achieve nanodispersed OC and beyond that the compatibilizer causes a structural change in the polymer crystalline morphology. It was also found that the tensile property enhancement of LDPE/LLDPE/OC nanocomposites is closely related to the crystalline structure development made by incorporation of both OC and compatibilizer.

Effect of Processing Temperature on Crystallization, Phase Morphology and Mechanical Property of a Linear Low Density Polyethylene/Ethylene-Octene Copolymer Blend

Temperature is one of the key parameters to determine the structures and properties of polymers during processing, but the effect of processing temperature on similar-structured polymer blends has rarely been reported. In this work, a linear low-density polyethylene (LLDPE)/ethylene-octene copolymer (EOC) blend with similar-structured components was chosen as a model system to study the effect of processing temperature (including compounding temperature and molding temperature) on its crystallization, phase morphology, and tensile behavior. It was found that the blends presented evenly distributed rubbery domains at lower processing temperatures, whereas a special, EOC-rich phase domain consisting of a less stable crystalline phase and a rubbery phase was observed at higher processing temperatures. The phase morphology was mainly determined by the final processing temperature, which had a major effect on the yield stress of the material. This work not only reports novel results on processing-structure-performance relations of similar-structured blends but can also guide the design and production of LLDPE-based products with tailored properties.

The role of porosity and acidity in the catalytic upcycling of polyethylene

Plastics have become fundamental and widespread materials in our everyday life. Nowadays, the most demanded plastics are polyolefins, accounting for nearly half of the Global plastic production. However, the end-of-life disposal of these materials is an issue inevitably connected to their increased production. Among chemical recycling techniques, the most thoroughly investigated process is the catalytic pyrolysis, showing a vast panorama of different set-ups optimized for the major production of either gaseous or liquid compounds. In this contribution a series of mesoporous silica-based materials, either pure SiO2 or substituted with Zr and Al, were systematically synthetized varying both porous framework and surface acidity, in the attempt of rationalizing the effect of each parameter (deeply characterized by physico-chemical methods) on the catalytic pyrolysis of linear low-density polyethylene (LLDPE). The synthetized materials together with some zeolites and aluminas reference samples were tested towards LLDPE degradation in a batch reactor set-up optimized for the formation and accumulation of the gaseous compounds, coupled with IR spectroscopy for in situ monitoring the evolution of the most abundant species (mostly propylene and branched C4-C6 olefins, together with a minor fraction of ethylene and short hydrocarbons). This work points out the necessity of the presence of Brønsted acid sites for a good activity (in terms of both the yield of gaseous products and lowering of the process temperature), but it also reveals a non-negligible role of the Lewis acid sites and it warns about the importance of controlling not only the amount of acid sites but also their strength.

Ethyl Formate Fumigation for Control of the Scale Insect Asiacornococcus kaki, a Quarantine Pest on Sweet Persimmon, Diospyros kaki: Efficacy, Phytotoxicity and Safety

Sweet persimmons are a valuable export commodity. However, the presence of live insects such as Asiacornococcus kaki limits their access to many export markets. Methyl bromide, traditionally used for pest control, is damaging to human health and the environment. Ethyl formate (EF) is a viable alternative; however, its effectiveness against A. kaki on sweet persimmon fruit is unknown. We evaluated the effectiveness of EF fumigation in controlling A. kaki present under the calyx of persimmon fruit. The hatching rate of eggs and the survival rates of nymphs and adults of A. kaki at low temperatures, its LCt50 and LCt99 after EF exposure, and phytotoxic damage caused by EF were evaluated in laboratory-scale and commercial-scale tests. The dose-response tests showed that the EF LCt99 at 5 °C was 9.69, 42.13, and 126.13 g h m-3 for adults, nymphs, and eggs, respectively. Commercial-scale tests demonstrated EF efficacy against all A. kaki stages without causing phytotoxic effects on persimmons, though the eggs of A. kaki were not completely controlled in linear low-density polyethylene (LLDPE)-packaged fruit. This study demonstrated that EF is a potential fumigant for quarantine pretreatment, especially before persimmon fruit is packed with LLDPE film, to control A. kaki infesting sweet persimmon fruit.

Customizing the comonomer incorporation distribution in Ziegler–Natta‐based LLDPE: Harnessing the influences of the titanation temperature during catalyst synthesis and of polymerization process parameters

AbstractThe microstructure of linear low‐density polyethylene (LLDPE) is strongly influenced by short‐chain branches (SCBs) incorporated into the polymer backbone. Varying the number, distribution, and length of SCBs allows the properties of the resulting polymer to be tailored to meet specific requirements. Using Ziegler–Natta (ZN) catalysts for synthesis has disadvantages in terms of the comonomer incorporation distribution (CID) compared to, for instance, metallocene and post–metallocene catalysts. Nevertheless, ZN catalysts continue to be widely used, as many of the new generations of catalysts are more difficult to handle and cannot match the cheap cost of ZN catalysts. To improve this aspect of ZN catalysts, we investigated the influence of catalyst titanation temperature and polymerization process parameters on the CID. Our results show that it is possible to manipulate the process parameters of the present ZN catalyst system to yield a desired comonomer amount and CID in the polymer. Varying the titanation temperature clearly influenced the titanium content of the catalyst. Molecular‐weight distribution analysis and deconvolution results indicate that changes in the amounts of comonomer incorporated and in the CID are directly related to the catalyst's active site that produces the lowest‐molecular‐weight fraction.

Comprehensive investigation of corrugated fiberboard boxes with edge vents for ambient loading of Chinese cabbage: Part Ⅱ – Quality changes in cellulose paper- and LLDPE film-wrapped Chinese cabbage stored in ventilated corrugated fiberboard boxes

Consumption of fresh produce has increased in recent years, as have the post-harvest losses during produce distribution. This has generated a need for optimum post-harvest treatment to increase the longevity of the produce. In this study, the temperature and relative humidity for the storage test were set as the refrigerated container conditions (ambient loading) and the quality change in Chinese cabbage wrapped with a cellulose paper sheet or linear low-density polyethylene (LLDPE) film in ventilated corrugated fiberboard boxes was evaluated. Weight loss, trimming loss, total soluble solid, pH, firmness, and color were measured every 10 d from 0 to 30 d. The weight loss values of Chinese cabbage wrapped with cellulose paper and LLDPE film at 30 d were approximately 3.7–4.4% and less than 1%, respectively. The trimming loss and firmness of Chinese cabbage wrapped with an LLDPE film were significantly better than those wrapped with a cellulose paper sheet at 30 d. However, the outer leaf surface measured by color meter was more damaged in Chinese cabbage wrapped with the LLDPE film than in those wrapped with the cellulose paper sheet because the wrapping of the former was tighter than that of the latter. In addition, the reduction in the mechanical properties of the boxes with 0%, 2%, and 3% of vent hole area against the horizontal cross section containing Chinese cabbage was measured at 0 and 30 d by performing not only mechanical property tests, such as edge crush test, bursting strength test, and box compression strength test, but also data logging of relative humidity in the headspace of each box. The relative humidity in the headspace of each box was constant at 75 ± 5% after the first increase during 0–24 h. Further, we evaluated the results of the box compression strength test at 30 d, comparing them with the required box compression strengths calculated by the equations provided in the criteria of the Fibre Box Association and American Society for Testing and Materials D4619. Thus, our findings can explain the changes in the quality of Chinese cabbage and the mechanical properties of corrugated fiberboard boxes prepared using two different internal package treatments.

Dynamics of temperature dependence of the dielectric properties of a nanocomposite material based on linear polyethylene in the vicinity of the percolation transition

Within the frequency range of 30 to 105 Hz and temperatures of 18 to 80 °C, the dielectric properties of linear low-density polyethylene with impurities of flame retardant (20 wt.%) and multilayer carbon nanotubes (1.5 wt.%) were investigated using the oscilloscopic method. This concentration value of carbon nanotubes slightly exceeds the concentration of nanotubes (1%), at which the percolation transition begins for the dependence of the polymer electrical conductivity on the content of nanotubes. It has been shown that the frequency dependence of electrical conductivity can be approximated by two exponential dependences. It has been found that when the sample is cooled, changes in the values of dielectric permittivity and electrical conductivity do not occur in the same way as when heated. The temperature dependences of conductivity for low (102 Hz) and high (104 Hz) frequencies have been obtained.

Eco-friendly tiles: fabrication and testing of composite tile made from industrial gypsum wastes

PurposeThe purpose of this study is to utilize two types of gypsum mold wastes from two different factories as novel and economical reinforcing fillers for composites that may be useful for building materials and floors. Two types of gypsum mold wastes from two different factories as raw materials were incorporated into linear low density polyethylene (LLDPE) aiming to get rid of that waste in one hand and obtaining useful economical composites suitable for building materials and floors.Design/methodology/approachComposites were prepared from two types of gypsum mold wastes substituted with different ratios from raw gypsum and LLDPE throughout the melt blending technique. The physico-mechanical and electrical investigations in addition to the morphology of the composites were included.FindingsThe mechanical results illustrate that substituting commercial gypsum with gypsum mold waste positively affects tensile strength, flexural strength and hardness shore D for the LLDPE composites. The tensile strength increased from 5 MPa for LLDPE filled with commercial gypsum as blank samples to 11.2 and 13.2 MPa for LLDPE filled with D and S waste. Also, electrical properties which include both permittivity ɛ′ and dielectric loss ɛ″ increased with increasing the waste content in the LLDPE matrix. In addition to the electrical conductivity values, σ lies in the order of insulation materials. Consequently, it is possible to produce materials with a gypsum matrix by adding industrial waste, improving the behavior of the traditional gypsum and enabling those composites to be applied in various construction applications as eco-friendly tiles.Originality/valueThis study aims to prepare eco-friendly composites based on LLDPE and waste gypsum mold to preserve resources for the coming generations, other than lowering the environmental footprint and saving the costs of getting rid of it.