Low Density Polyethylene Samples Research Articles

Effect of thermal-oxidative and mechanical degradation of recycled LDPE on foaming

In this study, we investigated the effect of recycling process on the molecular structure, viscoelasticity and foaming behavior of low density polyethylene (LDPE). A series of LDPE samples with different recycling process was prepared by multiple extrusion using a twin-screw extruder. The molecular weight distribution (MWD) was characterized by gel permeation chromatography (GPC). Wider MWD indicated the generation of higher molecular weight products. Small-amplitude oscillation rheology showed reduced loss factors, indicating that the chain entanglement was more difficult to relax. Moreover, nonlinear viscoelasticity was investigated using elongational rheology and molecular stress function (MSF) model. The results showed a steeper strain hardening exhibited in recycled LDPE. The correlated parameter β in the MSF model indicated that the recycling did not significantly change the branches regularity in LDPE, while the increasing [Formula: see text], the other correlated parameter, indicated that the chain entanglement was enhanced, which was corresponded to the improvement of high molecular weight component. The foaming results revealed that the recycled LDPE had finer cellular structure and higher nucleation density. Moreover, despite adding PP and active CaCO3 to simulate the impurities, the foamability loss of these mixed samples was well restricted and still valuable. Recycled LDPE is instead better than its corresponding virgin one in foaming performance, exhibiting the application potential for further developments.

Influence of a biodegradable contaminant on the mechanical recycling of a low‐density polyethylene sample

AbstractMechanical recycling of oil‐derived polymers is certainly our best option to reduce pollution, save raw materials, and protect ourselves and the environment from the adverse effects of waste disposal. However, the presence of contaminants, including other types of plastics, that are mixed in during the recycling collection process or during the mechanical waste sorting stage could adversely affect the quality of the recycled product, leading to the recycling of a poor‐quality secondary material. In this work, the influence of a biodegradable contaminant on the mechanical recycling of a low‐density polyethylene (LDPE) sample was investigated by rheological (shear and non‐isothermal elongation) and mechanical analyses. The results showed that 2% of the contaminant is able to influence the rheological, shear, and isothermal elongation properties of recycled LDPE, while the results of the mechanical tests showed that after one extrusion cycle, the main tensile properties were not significantly affected by the presence of the contaminant, but after only two cycles of extrusions, some significant reduction in the final properties began to appear. In short, the presence of 2% of a biodegradable co‐polyester in a LDPE matrix gives rise to a more pronounced decay of the rheological and mechanical properties, but, after two extrusion steps, both rheological and mechanical properties seem still useful for the production of film.Highlights To what extent the contaminant affects the quality and usability of the recycled LDPE; The effects of contamination on the LDPE sample during the recycling process; Reduction in properties, compromising product quality; Compromised product quality after only two additional processing steps; Important implications for the recycling industry.

In-situ photocatalytic degradation of low-density polyethylene: A pathway towards eco-sustainability and circular economy

The present study demonstrates the accelerated rate of photo-degradation in low-density polyethylene (LDPE) films using nanomaterials like titanium dioxide (TiO2) in a photochemical reactor, an efficient, environmentally benign, and sustainable chemical. The effect of various parameters such as source of light, catalyst loading, pH, and temperature was investigated to achieve maximum degradation on a laboratory scale. The surface morphology with molecular and chemical structure changes in the nanocomposite films was monitored before and after degradation using various analytical techniques. It is found that the degradation reaction rate is greatly affected by pH and temperature and follows the first-order photo-thermal kinetics reactions. The calculated activation energies for the different properties range from 77.6 kJ/mol for carbonyl group formation to 55 kJ/mol for vinyl group formation at an optimum pH of 4 and temperature of 30 °C, respectively. The optimized sample's storage modulus (Esm) increased from 17.76 to 210 MPa, demonstrating the loss of tensile strength after irradiation and increased elasticity. Thus, it clearly demonstrated that the LDPE sample loaded with 12% catalyst and exposed to 288 h at pH 4 and 30 °C temperature degraded most efficiently with 6.25% weight loss. In addition, there is a high correlation between the area of degradation and carbonyl index with R2 > 0.96, which helps in validating the fact that during the degradation process, there is volatilization of degradation products that leads to the formation of 0.523 mm (in length) of holes (microscopic analysis). This study brings new insights into reducing plastic pollution by minimizing waste prevention and generation at the source by promoting the usage of intermediates (formed during degradation) as a secondary material for producing new plastic products.

Crystallinity and Oscillatory Shear Rheology of Polyethylene Blends.

Crystallinity and rheological behavior are significant for processing semi-crystalline polymers with fine mechanical properties. There is always an economical need to create a less expensive new material with better properties. Non-isothermal crystallization and oscillatory shear rheology of different branch-type polyethylene-polyethylene blends were investigated. Samples of high-density and low-density polyethylene (HDPE/LDPE) (20/80, 40/60, 60/40 and 80/20 weight ratios) and two types of high-density and linear low-density polyethylene (HDPE/LLDPE) (40/60 and 60/40 weight ratios) were prepared via extrusion. The materials were tested by differential scanning calorimetry (DSC) at several cooling rates (5, 10, 20, 30 and 40°/min) and by oscillation rheometry (ARES G2) at low angular frequency range to prove their miscibility or immiscibility. It was found that the one-peak melting endotherm of the 80-20% HDPE-LDPE blend could indicate miscibility in the solid phase, while the other HDPE-LDPE blends with two-peak curves are partially or not miscible. In contrast, all the HDPE-LLDPE blends indicate co-crystallization, but the 40-60% HDPE-LLDPE butylene blend is probably immiscible. It was revealed that complex viscosity decreases with angular frequency: linearly for HD-LD blends and not linearly for HD-LLDPE blends. The complex viscosity shows linear behavior with composition for HD-LLDPE blends, while there is a positive-negative deviation for HD-LD blends. In the liquid phase, according to rheological measurements, the HDPE-LDPE blends are not or partially miscible, while the HDPE-LLDPE blends are probably miscible.

Biodegradation of polyethylene, biodegradable-polyethylene bags and corn residues using Tenebrio molitor larvae

The degradation capacity of different types of plastic from its ingestion by mealworms (the larvae of Tenebrio molitor), as well as its survival, was studied. Bags build from plastic nominally known as low-density polyethylene (LDPE); compostableplastic, made from corn waste (CPE); and polyethylene with d2w technology (d2wPE) plastic, were used. T. molitor larvae were subjected to a 7-day starvation period and then only fed with the different types of plastics for 56 days. Two groups of samples were prepared with the different plastics. On the one hand, the plastics were exposed to a UV photodegradation pretreatment from 260 to 285 nm and then used as the only source of food for the larvae. On the other hand, the same experiment was carried out without the UV pretreatment. The objective was to compare the possible effects of UV radiation on the plastics and their subsequent degradation by the larvae. The maximum degradation rates with UV pretreatment were 98%, 77% and 4% for CPE, LDPE, and d2wPE samples, respectively. Degradation rates without pretreatment were 79%, 54%, and 3%, and were obtained in the same order. In both scenarios, larval survival was significantly affected just for the d2wPE samples, reaching an average mortality rate of 98%. For the rest of the samples, the average mortality rate was only 12%.

Influence of irradiance on the photooxidation of HALS stabilized low-density polyethylene

This paper concerns the experimental analysis of the effect of irradiance on the photooxidation of low-density polyethylene (LDPE) stabilized with different HALS. Infrared analysis in transmission mode was used to monitor the extent of oxidation provoked by the exposure of thin samples (100 µm thick) in a SEPAP MHE unit (Atlas/Ametek) at two different irradiances (90 W.m − 2 and 300 W.m − 2 between 300 and 420 nm). The temperature of the samples was maintained constant in order to focus on the impact of irradiance on the kinetics, without interfering with the temperature. The intended goal was to characterize the effect of the irradiance in accelerated testing and the consequences on the lifetime prediction. Previous results obtained in the case of unstabilized LDPE samples showed that no acceleration was obtained when increasing the irradiance from 90 W.m − 2 and 300 W.m − 2 while keeping the temperature constant. In the case of the stabilized samples, the results presented in the present article show that the rates of photo oxidation tended to increase when increasing the irradiance. However, the ratio of these rates never reaches the ratio of the irradiances, and these ratios depends on the stability of the samples.

Investigate the effect of short chain branching and lamellar thickness on mechanical and optical properties of linear low-density polyethylene by successive self-nucleation/annealing (SSA) technique

In this article, various polyethylenes based on Ziegler-Natta and metallocene catalysts with different comonomer contents were investigated by successive self-nucleation and annealing (SSA) technique. Lamellar thickness, short chain branches content (SCBC) and methyl sequence lengths (MSL) were calculated by the modified Thomson-Gibbs equation and suitable calibration curves available in the literature. Moreover, linear low-density polyethylene (LLDPE) samples with different physical, mechanical and optical properties were investigated according to heat of fusion, the lamellar thickness, SCBC and methyl sequence length (MSL) of the multiple peaks. The results showed that the mechanical and optical properties such as dart drop impact strength, Elmendorf tear resistance, softening point and haze are associated with the lamellar thickness and SCBC of the resins.

Decontamination of recycled LDPE using different washing methods

Post-consumer low density polyethylene samples were analysed for PAHs, PCDD/Fs and dioxin-like PCBs content. Subsequently, various treatments were applied to determine a process capable of decontaminating the plastic samples: extraction with polyethylene glycol at different temperatures with and without agitation; extraction using subcritical and hot water at different temperatures in a basic medium; compound degradation by ultraviolet radiation; and compound degradation by advanced oxidation processes using H2O2. The most effective treatment was extraction with polyethylene glycol (agitated) at 120 °C, reducing contamination by 89%, 85% and 95% of PAHs, PCDD/Fs, and dioxin-like PCBs, respectively. The least effective treatments (subcritical and hot water), maximum reductions of 47% and 19% of PAHs were obtained for the temperatures of 160 °C and 90 °C. UV oxidation increased the toxic equivalency of the samples (calculated using the toxicity equivalency factors) by up to 1400%, through the co-formation of the most toxic congeners, e.g., the non-ortho PCBs

Force-Based Characterization of the Wetting Properties of LDPE Surfaces Treated with CF4 and H2 Plasmas.

Low-density polyethylene (LDPE) films are widely used in packaging, insulation and many other commodity applications due to their excellent mechanical and chemical properties. However, the water-wetting and water-repellant properties of these films are insufficient for certain applications. In this study, bare LDPE and textured LDPE (T-LDPE) films were subjected to low-pressure plasmas, such as carbon tetrafluoride (CF4) and hydrogen (H2), to see the effect of plasma treatment on the wetting properties of LDPE films. In addition, the surface of the LDPE film was textured to improve the hydrophobicity through the lotus effect. The LDPE and T-LDPE films had contact angle (θ) values of 98.6° ± 0.6 and 143.6° ± 1.0, respectively. After CF4 plasma treatments, the θ values of the surfaces increased for both surfaces, albeit within the standard deviation for the T-LDPE film. On the other hand, the contact angle values after H2 plasma treatment decreased for both surfaces. The surface energy measurements supported the changes in the contact angle values: exposure to H2 plasma decreased the contact angle, while exposure to CF4 plasma increased the contact angle. Kinetic friction force measurements of water drops on LDPE and T-LDPE films showed a decrease in friction after the CF4 plasma treatment, consistent with the contact angle and surface energy measurements. Notably, the kinetic friction force measurements proved to be more sensitive compared to the contact angle measurements in differentiating the wetting properties of the T-LDPE versus 3× CF4-plasma-treated LDPE films. Based on Atomic Force Microscopy (AFM) images of the flat LDPE samples, the 3× CF4 plasma treatment did not significantly change the surface morphology or roughness. However, in the case of the T-LDPE samples, Scanning Electron Microscopy (SEM) images showed noticeable morphological changes, which were more significant at sharp edges of the surface structures.

Cross-sectional microstructural analysis to evaluate the crack growth pattern of weathered marine plastics

Fragmentation of degraded plastics and release of smaller secondary microplastics is usually attributed to the growth of environmental stress cracks. Analysis of crack patterns derived from chemical degradation can be useful not only for assessing the cause of plastic fracture and evaluating the useful lifetime of a product, but it can also potentially provide valuable information on the generation of microplastics. However, the literature with respect to microplastics generation is generally limited to surface observations of polypropylene and polyethylene. Here, we used ion-beam milling to prepare cross-sections of fragments of 15 plastic products made from five commodity plastics (polypropylene, polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate) that were collected at two beaches in Japan, and then we examined the microstructures of those cross-sections by means of scanning electron microscopy and energy dispersive X-ray spectroscopy. Crack growth in the depth direction was examined to provide insights into microplastic generation behavior. In all of the polypropylene samples, and some of the low-density polyethylene and polystyrene samples, cracks with a depth exceeding 100 μm from the sample surface were observed. Considering that crack growth causes fracture of degraded plastic and microplastic release, these observations suggest the release of sharp-edged microplastics from the crack fracture surface. In contrast, in the high-density polyethylene and polyvinyl chloride samples, crack growth was limited to within 20 μm of the sample surface, suggesting the release of irregularly shaped microplastics and additive particles. The present results suggest that the degradation behavior of plastic products in the depth direction is dependent on the type of plastic.

Mechanical, thermal, and morphological properties of low-density polyethylene nanocomposites reinforced with montmorillonite: Fabrication and characterizations

Nanoparticle incorporation in polymeric matrices to generate polymer nanocomposite with the intention of maximizing the “nano-effect” derived from the nanoparticles and minimizing the drawbacks of the polymer is an emerging field of research. In this study, low-density polyethylene (LDPE) was mixed with varying concentrations of montmorillonite (MMT) nanoclays to create a polymer nanocomposite with desirable characteristics. Composite sheets with nanoclays contents of (0, 1, 2, 3, and 4 wt%) were prepared for hardness, tensile-fractography, thermal conductivity, and tensile testing (elongation and stress-at-break). The results showed that, according to scanning electron microscope (SEM) study, LDPE has a low flexibility temperature and is prone to corrosion. For larger MMT filler loadings (>3% wt), tensile-fractography showed nanoclays particle micro-aggregation. The pure LDPE sample fracture’s tensile-fractography showed plastic deformation. MMT/LDPE samples with 3% wt hard MMT filler have brittle fractures without appreciable plastic deformation. Thermal conductivity test results show that LDPE/MMT composite thermal conductivity decreased with increasing clay concentration. The thermal conductivity values were reduced from a value of 0.13 W/m.K to a value of 0.039 W/m.K when reinforced with 0% wt to 3% wt filler loading, respectively. With 4% wt filler loading, LDPE/MMT composites had the highest shore hardness at 47.4. Yet, tensile tests indicated that increasing clay content improved the composite’s characteristics. At modest loading percentages (1–2 wt%), tensile results were excellent. Furthermore, the elongation at break of the unadulterated LDPE was reduced by 20% and 30% after introducing 1% wt and 2% wt of MMT as reinforcement additives, respectively. Hence, MMT clay can improve the mechanical properties and thermal insulation of LDPE polymer matrix.

Safety assessment of 'waxes, paraffinic, refined, derived from petroleum-based or synthetic hydrocarbon feedstock, low viscosity' for use in food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP Panel) assessed the safety of the 'waxes, paraffinic, refined, derived from petroleum-based or synthetic hydrocarbon feedstock, low viscosity' (FCM No. 93), for which the uses were requested to be extended for articles in contact with fatty foods. Migration from low-density polyethylene samples containing 1% w/w of a representative wax was tested in food simulants. In fatty food simulants, the migration of mineral oil saturated hydrocarbons (MOSH) ≤ C35 was 142mg/kg food, exceeding the overall migration limit for plastic FCM. Mineral oil aromatic hydrocarbons (MOAH) with at least two rings are largely removed during the manufacturing process. Based on various lines of evidence, the Panelconcluded that any concern for the potential presence of MOAH with two or more conjugated aromatic rings can be ruled out. Based on the genotoxicity studies and on the content of polycyclic aromatic hydrocarbons (PAHs), the substance does not raise a concern for genotoxicity. Available toxicokinetic data showed a limited accumulation of MOSH. No adverse effects were observed up to the highest tested dose of 9g/kg body weight per day in a 90-day repeated oral toxicity study in Sprague-Dawley rats. The available results showed that FCM No. 93 is devoid of endocrine activity. The provided information on chronic toxicity and carcinogenicity was limited and inadequate to reach conclusions on these endpoints. Therefore, the CEP Panelconcluded that under the intended and tested conditions of uses, the substance does not raise safety concern for the consumer if used to a level ensuring that its migration into food is no more than 5mg/kg.

Important modifications in dielectric properties of LDPE after contact with some foods

We analyzed the dielectric properties of low density polyethylene (LDPE) grad (LA071) materials after different time intervals of contact with apple, pineapple, mango, and cow’s milk. Cole–Cole plots show the distribution of relaxation, depending on the time of contact and the type of food. Furthermore, chemical processes between LDPE and foods lead to significant changes in the dielectric properties of LDPE samples, relying on contact time and food type. In our study, contact with cow’s milk causes the most LDPE degradation, whereas contact with mango causes the least LDPE degradation. It is suggested that dielectric measurements be used as indicators of LDPE degradation and some other defects.

Effects of flame retardants on extinction limits, spread rate, and smoke release in opposed-flow flame spread over thin cylindrical polyethylene samples in microgravity

Though flame retardants are considered for use in spacecraft, their performances in microgravity are still poorly understood. To assess their effects on flame extinction, opposed flame spread rate, and smoke emission in the absence of buoyant flows, thin cylindrical samples of Low Density Polyethylene (LDPE) loaded with intumescent flame retardants are ignited in parabolic flights. Two types of flame retardants characterized by different mechanisms of intumescence are considered, namely Expandable Graphite, (EG), and Ammonium polyphosphate / Pentaerythritol, (AP), for which thermal stress and chemical recombination drive physical expansion, respectively. Observations are then reported and contrasted with results obtained at normal gravity for different flame retardant loads, under varying oxygen content at given ambient pressure and flow velocity. Focusing on the flame leading edge, results related to flame spread and flame extinction are analyzed first. At normal gravity, increasing the flame retardant load improves fire safety through an increase in the flame extinction limit on the one hand, and a reduction in the average flame spread rate for all oxygen contents studied on the other hand. In contrast, results in microgravity show no modification in the extinction limit over the range of flame retardant loads studied, and the benefits in average flame spread rate reduction are less pronounced. Investigating then radiative quenching at the flame trailing edge, smoke emission is never evidenced at normal gravity. However, in microgravity, the addition of flame retardants increases the range of conditions leading to smoke emission, which is detrimental to fire safety. These observations are valid for both flame retardants, yet more pronounced for EG-loaded samples than AP-loaded samples. These ambivalent effects on fire safety of AP and EG addition in microgravity, which are not evidenced at normal gravity, call for a cautious integration of flame retardants in the scope of space exploration.

Biodegradation of Low-Density Polyethylene-LDPE by the Lepidopteran Galleria Mellonella Reusing Beekeeping Waste.

Plastic pollution is one of the most serious environmental problems of this century because most plastics are single-use, and once their useful life is over, they become pollutants, since their decomposition takes approximately 100–400 years. The objective of this research is to evaluate the efficacy of low-density polyethylene (LDPE) biodegradation by G. mellonella in the district of Pangoa, Junín, Peru. For the development of the study, the G. mellonella was conditioned in three groups of beekeeping residues (beeswax, balanced diet, and wheat bran); after the conditioning stage, the biodegradation treatment was developed, which consisted of placing the G. mellonella in terrariums with the LDPE, the treatments were carried out at three different times (24, 36, and 48 h). To evaluate the efficacy of biodegradation, two analyses were taken into account: the Raman analysis of the low-density polyethylene samples and the weight reduction of the treated LDPE. The results of the Raman analysis indicated that the best treatment was the one applied with G. mellonella conditioned with beeswax, obtaining a wavelength intensity of 0.45 μ.a., while the weight reduction of the LDPE indicated that the best results were given at 36 h and conditioned with beeswax with a reduction of 236.3 mg. In conclusion, the use of G. mellonella for the biodegradation of low-density polyethylene is effective when it is conditioned with beeswax and the treatment is carried out at 36 h.

Melt flow ratio: A way to identify the type of polyethylene

Melt flow ratio (MFR or I21/I2) was measured for dozens of polyethylene (PE) in the melt index (MI or I2) range of 1–10 for various types of PE. I21/I2 for samples of linear low density polyethylene (LLD) polymerized by a Ziegler-Natta catalyst (ZN-LLD) lie near I21/I2 = 25, whereas those for specimens of metallocene linear low density polyethylene (m-LLD) scatter close to I21/I2 = 18. The plot of I21/I2 vs I2 for LLD showed that I21/I2 is almost independent on molecular weight and short chain branching (SCB), but strongly dependent on molecular weight distribution (MWD). The broader MWD, the larger I21/I2. This rule basically holds for both low density polyethylene (LDPE) and high density polyethylene (HDPE). However, at a certain I2 around 6 a discontinuous jump of I21/I2 for HDPE samples exits, where I21/I2 for samples of I2 less than 6 lie near those of LDPE and I21/I2 for ones having I2 bigger than 6 disperse close to those of ZN-LLD. In addition, bimodal PE or PE with long chain branching has a bigger I21/I2 in some case. Further, the relationship between the viscosity and melt index was discussed, indicating that I21/I2 as well as MWD is characteristic of all types of PE. Consequently, I21/I2 can be used as a convenient and efficient approach to identifying the type of PE.

Influence of nitric acid on biodegradation of polystyrene and low-density polyethylene by Cephalosporium species.

Petroleum-based polymers are not susceptible to microorganisms because of its high molecular weight. Acid treatments convert the polymers into a more oxidized form having low molecular weight. The present in-vitro degradation study focuses on the potential of Cephalosporium species to degrade acid-treated polystyrene (PS) and low-density polyethylene (LDPE) films. A weight loss of around 12% and 13% was achieved for PS and LDPE films respectively in eight weeks of treatment with Cephalosporium species. Fourier transform infrared spectroscopy analysis showed the formation of hydroxyl and carbonyl groups in nitric acid treated PS and LDPE films, respectively. Scanning electron microscopy indicated modifications in the surface morphology of PS and LDPE films after chemical and microbial treatment. An increase in crystallinity of pre-treated polymer samples was observed after fungal treatment. The observations of present study confirmed the enzymatic deterioration and assimilation of pre-treated PS and LDPE samples by the microbial species.

A rapid method for approximative evaluation of thermooxidative stability of organic materials.

In this work, a novel procedure for fast assessment of the material residual stability is proposed. The method resides in integral isoconversional kinetic analysis of the thermal oxidation of unaged material employing the Berthelot–Hood temperature function. Subsequently, the obtained conversion-independent kinetic parameter D is also employed for samples aged in various regimes. The value of conversion-dependent parameter A for aged samples is calculated from the oxidation onset temperature measured at 5 °C min−1. The residual stabilities are then calculated as a simple ratio of the parameter A of aged material to that of the unaged one. The method has been applied and verified for the samples of low-density polyethylene aged by thermal, radiation and combined ageing. The method can also be employed for high-throughput screening of the effect of various stabilizers and antioxidants in a given organic matrix.

Biodegradation of polyethylene based films used in water packaging by dumpsite bacteria

Water sachet bags are Low-density polyethylene (LDPE) based polymers that are of widespread use in Nigeria. The accumulation of these sachet bags has resulted to severe environmental pollution. Microorganisms have been found to provide an eco-friendly and practical alternative to conventional methods in the clean-up of LDPE wastes in the environment. This study investigated the potentials of six bacteria strains Lysinibacillus xylanilyticus PE4, Pseudomonas aeruginosa PE2, Pseudomonas aeruginosa S1, Stenotrophomonas maltophilia S6, Pseudomonas aeruginosa W5 and Achromobacter xylosoxidans strain to degrade water sachet films. The degradation was monitored for a period of 56 days in vitro and the extent of degradation was measured using Fourier transform infrared spectroscopy and scanning electron microscopy coupled with EDX. FTIR spectroscopy analysis of the bacteria treated LDPE samples revealed changes in functional groups of LDPE samples as a result of hydrolysis and oxidation of bonds in the LDPE polymer. Also, the EDX elemental analysis of the treated LDPE and the untreated control showed a reduction in percentage elemental carbon and increase in the elemental oxygen of the treated LDPE films which is evident of degradation. The findings indicate strongly the degradation potentials of these bacteria strains on LDPE polymer, they therefore show significant promise for bioremediation of plastic wastes.

Characterization of Dendritic Defects of Polyethylene Insulation Materials Based on Microstrip Gap Resonator

This article attempts to reveal the detection ability of microstrip slot resonator for water and electrical tree defects in insulating samples. The characteristics of microstrip gap resonator are analyzed in high-frequency electromagnetic simulation software. A gap capacitance extraction method is proposed based on two-port transmission theory, and the gap capacitances under different dielectric constants are analyzed based on this method. The resonant frequency of sensor is found to be negatively correlated with the dielectric constant of the materials. In the experimental part, the sensor made of double-sided copper clad plate with medium FR4 was used to detect the water tree and electrical tree in low-density polyethylene (LDPE) samples, and the experiment results showed good feasibility.