Transparent Polyethylene Film Research Articles

Measuring Photosynthesis of Entire Tree Crowns and Pulse Label Trees in Large Closed Chamber with 13CO2 in the Field: Design and Testing

Measuring the photosynthesis of entire tree crowns and pulse labelling trees with 13CO2 are valuable approaches to study carbon acquisition, transfer, and allocation; however, it is challenging for trees in the field. The objective was to develop and field test large chambers (35 - 45 m3) that enclosed the entire crown of a tree, provided a reliable estimate of tree crown photosynthesis, and ensured efficient 13CO2 labelling. The chambers, made of transparent polyethylene film pulled tightly over a frame, were equipped with an air conditioner, fans, and air blowers. Air temperature, relative humidity, and photosynthetic photon flux density were measured outside and inside each chamber. Six of 4-year-old rubber trees (Hevea brasiliensis) were pulsed-labelled with 18 L of 13CO2 in June and October 2016. The mean air temperature inside the chambers was 1.2 °C higher and the relative humidity 8 % lower than the outside air. The crown photosynthesis, calculated from the decrease in the CO2 concentration inside the chamber, was in the range 140 - 249 µmol s–1 and was significantly related to photosynthetic photon flux density, total leaf area of the tree, and average net CO2 assimilation at leaf level. The labelling efficiency, estimated as the ratio of the amount of 13C recovered in the foliage immediately after labelling divided by the amount of 13C delivered to the tree, was in the range 43 - 68 %. The designed chamber was suitable to estimate crown photosynthesis and perform 13CO2 pulse labelling of 5-m-tall trees in the field. HIGHLIGHTS Measuring carbon acquisition, transfer, and allocation of entire trees in the field is a challenge The paper describes in detail the system including a 45 m3 chamber that was developed and tested to measure crown photosynthesis and to label trees 5 - 6 m tall with 13CO2 The system and methodology proved efficient in controlling the chamber temperature and providing appropriate conditions for leaf gas exchanges The rates of crown photosynthesis were consistent with measurements at the leaf and ecosystem levels, providing a clear relationship with photosynthetic photon flux density More than 1-half the injected 13CO2 was recovered in the leaves after the end of labelling, showing that the design of the chamber and the labelling protocol were effective for studying C allocation within the tree GRAPHICAL ABSTRACT

Biodegradable film mulching promotes better soil quality and increases summer maize grain yield in North China Plain

ABSTRACT Soil pollution caused by the residual polyethylene film is a potential threat to agricultural sustainability. Biodegradable films are generally effective alternatives to reduce this pollution. However, soil quality changes responding to continuous biodegradable film mulch are still unclear. To reveal the accumulative effects of biodegradable film mulch on soil quality, we conducted a positioning experiment from 2016 to 2019 in North China Plain (NCP). Four treatments, including transparent polyethylene film mulching (PM), transparent biodegradable film mulching (TM), black biodegradable film mulching (BM), and non-mulching (CK) were employed. The results showed that compared with CK, both BM and TM treatments significantly reduced soil bulk density and increased soil microbial activity and soil enzyme activity; however, BM and TM did not affect soil nutrient content. Compared with CK, BM treatment significantly increased soil quality index (SQI) by 7.2% (in 2019) due to higher soil fertility content and bioactivity; however, TM and PM treatments decreased SQI by 3.2% and 3.8%, respectively. Besides, compared with CK, BM significantly enhanced summer maize grain yield by 30.35%. Therefore, black biodegradable film is a potential alternative to polyethylene film to improve soil quality and maize production in NCP.

Environmental and Economic Impacts of Biodegradable Plastic Film Mulching on Rainfed Maize: Evaluations on Sustainability and Productivity

Fully biodegradable (Bio) plastic film is an alternative option to replace widely used polythene film in semiarid rainfed regions. However, its productivity and environmental friendliness remain unclear. Field observations were conducted using maize variety Pioneer 335 to evaluate the effects of Bio film mulching on soil hydrothermal status, carbon sequestration, and water productivity in a semiarid site of northwest China from 2016 to 2017. Six treatments were designed as (1) CK-1, ridge and furrow (RF) without mulching, (2) CK-2, conventional flat planting without mulching, (3) RFT, RF with transparent polyethylene film mulching, (4) RFB, RF with black polyethylene mulching, (5) RFS, RF with wheat straw mulching, and (6) RFBIO, RF with Bio film mulching. The results indicated the growth prophase of maize from sowing to silking stage received 160 mm of rainfall in cool and wet 2016, but decreased to 119.8 mm in warm and dry 2017. Bio film degradation was advanced at the mid stages of maize growth by 10 days in 2017 compared with 2016. Similarly to RFT, RFBIO significantly improved soil hydrothermal conditions compared with RFS, CK-1, and CK-2; however, its magnitude decreased at the maturity stage (P < 0.05). Both RFT and RFB had significantly higher grain yields, economic benefits and water use efficiencies than RFBIO and RFS did across two growing seasons (P < 0.05). RFBIO led to a steady improvement in soil organic carbon, light fraction organic carbon, and carbon to nitrogen ratio, which were better than those of RFT. Therefore, Bio film mulching might be environmentally friendly but not highly productive.

GROWTH AND DEVELOPMENT OF TABLE BEET DEPENDING ON DIFFERENT METHODS OF MULCHING IN THE CONDITIONS OF THE RIGHT BANK FOREST STEPPE OF UKRAINE

Goal. Study the influence of soil mulching methods on the growth, development of table beet plants, root crop yield and their quality indicators in the conditions of the Right-Bank Forest-Steppe of Ukraine. Methods. Analysis, synthesis, generalization, laboratory and field experiment. Results. The use of mulching crops with organic and inorganic materials has a positive effect on reducing the duration of the growing season of table beets. The emergence of seedlings in the control variant was observed on the 17th day after sowing, and in the variants where mulching was used - on the 15th day. The formation of the first pair of real leaves during mulching of the soil with a transparent and black polyethylene film was ahead of the control by 3 days, and by humus, sawdust and agrofiber by 4 days. The use of inorganic materials promotes faster onset of technical ripeness, namely 3-6 days earlier, and mulching with organic materials - 6-7 days, respectively. The use of different methods of mulching crops contributes to the growth of the leaf surface of table beets by 4.3-5.8 thousand m2 / ha, or 15.5-20.9%, respectively. The period "beginning of root formation-technical ripeness" was characterized by the largest accumulation of biomass in table beet plants compared to the previous period. Based on this, the productivity of photosynthesis increased - 2.7-3.0 g / m2 × day, depending on different methods of mulching. The use of polyethylene film provided an increase in photosynthesis net productivity by 8% in the case of agrofiber by 12%. The most favorable conditions for the formation of the maximum indicator of photosynthesis net productivity have developed in the case of arable materials use (sawdust, humus). In the period "beginning of root formation-technical ripeness" the productivity of photosynthesis in this case was 2.9-3.0 g / m2 × day, which is 16-20% higher than the control. Conclusions. The results of research show that the use of different methods of mulching seedlings with polyethylene film, agrofiber and local organic materials, contributes to the intensification of physiological and biochemical processes occurring in the plant of table beet. Further study and improvement should focus on in-depth study of innovative mulching methods using modern high-yielding varieties and hybrids of table beets.

Guided-mode resonance pressure sensor based on a stretchable low-density polyethylene film

In this study, we demonstrate a method to fabricate a guided-mode resonance (GMR) device on a flexible and transparent low-density polyethylene (LDPE) film and present the measurement results of this device as a pressure sensor. A simple thermal-nanoimprinting process was used to fabricate a grating structure on the LDPE film substrate. This very flexible film was attached to a glass plate using an adhesive and sacrificial layer for coating high-refractive-index titanic oxide on the grating surface to form the GMR device. The LDPE-GMR device was equipped with a gas chamber to act as a pressure sensor. When the pressure inside the chamber was increased, the grating period of the GMR sensor also increased, resulting in a shift in the resonance angle of the GMR device. Owing to the higher flexibility of the LDPE film, a better pressure detection sensitivity and resolution can be obtained. Using the transmitted-intensity detection approach, we show that the transmitted laser power changes proportionally with the pressure increase. The experimental results showed that the LDPE-GMR pressure sensor could achieve a sensitivity of 8.27 µW/mbar and a limit of detection of 0.012 mbar at a power meter noise of 0.1 µW.

Nanosecond pulsed laser ablation of a transparent polyethylene film moving around the beam waist

A nanosecond pulsed laser that can induce the breakdown of air in the focal region was used to irradiate a transparent PE film having a thickness of 0.6 mm. A high-speed Schlieren optics system was used to record the ablation process. The results indicate that the irradiation process was sensitive to the specific positions of the PE film. When the front surface of the PE film was positioned slightly away from the beam waist, the initiated plasma, the generated plume and the crater on the surface of PE film differed significantly with the position of PE film in relation to the beam waist.

BATATA PRODUCTIVITY DEPENDING ON CULTIVATING CONDITIONS IN THE UDMURT REPUBLIC

One of the important issues of crop production in the context of global warming is introduction of vegetable plants. Batata (Ipomoea batatas (L.) Lam.) is a promising vegetable crop for introduction under the conditions of climate change. Analysis of temperature data from the Izhevsk weather station showed a steady increase of average annual and average temperature for April-September, which is a significant factor for cultivation of heat-requiring plants such as batata in an annual crop in the Middle Urals. The purpose of our research was to study the influence of shelter methods and temperature on productivity of batata in the collection of the Department of Introduction and Acclimatization of Udmurt Federal Research Center of the Ural Branch of the Russian Academy of Sciences. Studies on temperature effect on batata productivity were carried out for a number of years on the territory of the Udmurt Republic in two agro-climatic regions. Experiment on studying of shelter methods was laid in 2017 in the central agro-climatic region of Udmurtia. A close relationship between productivity and the sum of active and effective temperatures was revealed. The highest dependence was found on the sum of effective temperatures above 15 °C (correlation coefficient 0.95). Grocery-ware tubers were obtained in variants with application of temporary film shelters and a combination of shelters with polyethylene film mulching. Significant increase of the mass of tubers per plant (by 311.17 g) and yield (by 1.25 kg/m2) is noted in the variant of temporary film shelters in combination with transparent polyethylene film mulching. It is proved that it is necessary to use temporary film shelters or a combination of shelter and mulching in order to obtain high yields and grocery-ware tubers in the conditions of insufficient heat supply.

Fabrication of superhydrophobic P(VDF-HFP)/SiO2 composite film for stable radiative cooling

Daytime radiative cooling that cools down an object by reflecting solar light and radiating heat simultaneously is expected to be a promising technology for dissipating heat without any energy consumption. However, radiative cooling materials’ solar reflection and infrared emissivity will be affected by the rain or dust pollution, therefore reducing the cooling performance under outdoor environments. A superhydrophobic radiative cooling composite film with hydrophobic SiO2 embedded in poly(vinylidene fluoride-co-hexafluoropropene) was proposed via phase separation technology. The SiO2 particles not only imparted to the film porous micro-nano tier rough structure to enhance the surface hydrophobicity, but also improved the mid-infrared emissivity of the film. As a consequence, the as-prepared film achieved 10.3 °C cooling under direct sunlight with convective heat reduced by transparent polyethylene film, and excellent superhydrophobicity with water contact angle greater than 160° and sliding angle close to 0°. Moreover, the cooling performance and superhydrophobicity of the film changed little after immersion in different pH solution and long-time exposure to UV irradiation. Importantly, the obtained film demonstrated great self-cleaning property making it hardly to be contaminated in outdoor environments, which is significant for sustainable applications.

Effect of Different Nethouses on the Incidence of Insect on Vegetable Crops

In this study, the effects of different types of nethouses viz., NH1, NH2, and NH3, were investigated at the research farm of the Olericulture Division, Bangladesh Agricultural Research Institute (BARI) from Sep 2021 to Mar 2022 and compared to control (open field) in terms of the incidence of white fly, aphid, leaf miners, mites, and eggplant shoot and fruit borer (ESFB). This study included six vegetables 1) Tomato, 2) Eggplant, 3) Sweet pepper, 4) Broccoli, 5) Cucumber; 6) Okra, as well as four nethouse treatments: 1) UV stabilized transparent polyethylene film with 60 mesh insect net along with green shade net (NH1); 2) UV stabilized transparent polyethylene film with 60 mesh insect net (NH2); 3) 60 mesh insect net (NH3); 4) Open field infestation of white fly, aphid, leaf miners, mites, and ESFB was observed under open field conditions followed by NH1 conditions, while the lower infestation was observed in NH2 and NH3 for all vegetables. From the study, we found the use of stabilized transparent polyethylene film with a 60 mesh insect nethouse provided a negative effect on the presence of different types of notorious insects on vegetables. So, this type of protected nethouse will provide a new dimension to producing safe and quality vegetables in Bangladesh.

Electron transport and photosynthetic performance in Fragaria × ananassa Duch. acclimated to the solar spectrum modified by a spectrum conversion film.

Functional films have been used in greenhouses to improve the light environment for plant growth. Among them, a spectrum conversion film converting the green light of incident sunlight into red light has been reported to increase the crop productivity. However, the results are not always consistent, and the reasons for the improvement are not fully understood. The objectives of this study were to reveal the cumulative effects of a green-to-red spectrum conversion film (SCF) on the electron transport and photosynthetic performance of Fragaria × ananassa Duch. The photosynthetic efficiency, leaf optical properties, chlorophyll content, chlorophyll fluorescence, growth, and fruit qualities when the plant was grown under a transparent polyethylene film (PE) and SCF were evaluated. The sunlight modified by SCF did not change the leaf optical properties and chlorophyll content but significantly increased the chlorophyll fluorescence parameters related to reduction end electron acceptors at PSI acceptor side and the efficiency of electron transport. Without an increase in nonphotochemical quenching, the effective quantum yields of PSII and PSI of leaves grown under SCF were significantly higher than those parameters when grown under PE. Forty eight days after transplanting, the photosynthetic efficiency and photosynthetic rates of leaves and whole plants increased significantly under SCF compared to PE. The vegetative growth was not affected by SCF, but the fruit weight, sweetness, acidity, and firmness under SCF were significantly improved. These results indicated that sunlight modified by SCF stimulates electron flow and improves photosynthetic capacity and fruit quality of Fragaria × ananassa Duch.

The response of photosynthetic capacity and yield of cotton to various mulching practices under drip irrigation in Northwest China

Mulched drip irrigation is regarded as an effective water-saving irrigation technique that is adopted widely in dryland regions. However, due to the lack of efficient mulch film recovery, residual plastic film fragments accumulating in soil nowadays pose a risk to agricultural production sustainability. To mitigate the pollution result from polyethylene (PE) film mulching and demonstrate the relationship between soil microenvironment, photosynthetic capacity, yield, and water use efficiency of cotton (Gossypium hirsutum L.) in various mulching practices, a two-year field experiment was carried out to test five mulching practices (sprayable degradable film mulching; biodegradable transparent film with an 80-day induction period mulching; biodegradable transparent film with a 100-day induction period mulching; conventional transparent polyethylene film mulching; no film mulching) in Xinjiang, Northwest China. The results showed that mulching significantly increased soil water content and temperature by 23.83% and 15.01% (average on two years) in topsoil compared to the bare soil surface, associated with a higher plant height, leaf area index, photosynthetic rate and aboveground biomass accumulation. Soil moisture, temperature, and crop height all significantly influenced cotton leaf photosynthetic rate, and soil moisture had the most significant impact (the direct path coefficient was 0.450). The highest cotton yield and WUE were observed in PE film mulching (5480.59 kg ha−1 and 1.35 kg m−3, respectively, average on two years) and the biodegradable transparent film with a 100-day induction period was comparable with PE film in yield increased and reduction of water loss (yield and WUE was 5357.51 kg ha−1 and 1.29 kg m−3, respectively, average on two years). The sprayable biodegradable film also had good wetting and warming effects on soil, but notably, sprayable film performances were still weaker than that in solid films. Compared to solid degradable films mulching, soil moisture, soil temperature, photosynthetic rate, yield, and WUE in sprayable film mulching was decreased by 5.55%, 7.19%, 31.41%, 5.31%, and 8.58% on average, respectively. In general, biodegradable transparent film with a 100-day induction period could significantly improve soil water-heat status, enhance cotton development, reduce water evaporation, increase cotton yield and WUE, which provides a cotton-cultivation option to control residual PE fragments pollution and maintained cotton yield.

Effects of corona treatment on surface properties of co‐extruded transparent polyethylene film

AbstractCurrent study encompasses that the effect of corona treatment on the outer surface of transparent co‐extruded polyethylene films was at various levels by applying different wattages, in tandem with the blown film extrusion process. A maximum treatment of 42 dynes/cm was achieved at 4.5 KW of applied wattage. The heat seal joint strength of the films sealed at different combinations of treated/untreated surfaces was evaluated and an untreated/untreated surface combination was found to exhibit maximum strength (2.8 kgf/25 mm), while a treated/treated surface combination showed the minimum (1.41 kgf/25 mm) under identical conditions of sealing and testing. The peel adhesion to ascertain the treatment level on the treated surfaces was inspected by a standard Scotch tape method, and the results exhibited a linear relationship between the applied wattage and the pulling force of adhesion. The Fourier transform infrared spectroscopy (FTIR) spectra of the treated and untreated film samples in an attenuated total reflection (ATR) mode showed the peaks' characteristics mostly of polyolefin films. The morphologies of the treated surfaces displayed relatively rough surface compared to the untreated one. The barrier properties of the treated films in respect of water vapor and oxygen transmission rate do not undergo any appreciable change.

Irradiation of successive pulsed and continuous-wave lasers on a transparent polyethylene film

It is difficult to cut through a transparent material such as polyethylene (PE) film with a continuous-wave (CW) laser of the near-infrared wavelength, because of the low absorption of laser energy. The plasma induced by a pulsed laser, however, can damage the surface of a film, which can change the transparency of the material. In this study, a transparent PE film with a thickness of 0.6 mm was irradiated by various combinations of focused laser pulses and a CW laser. The test conditions and the processes were recorded visually by a Schlieren optics system on the side surface of the film and by a high-speed camera on the front surface. From the results, it can be concluded that, though it is difficult to cut through a transparent material such as PE film with only a pulsed or CW laser alone, once the transparency of the surface has been modified by multiple focused laser pulses, the PE film can be cut through easily by a CW laser with a near-infrared wavelength.

Soil hydro-thermal characteristics, maize yield and water use efficiency as affected by different biodegradable film mulching patterns in a rain-fed semi-arid area of China

The farming practice of fully mulched double ridge-furrow with polyethylene (PE) film has been widely used to improve productivity of many staple crops in arid and semi-arid regions of northwest China. However, the residual PE film has caused many environmental problems such as “white pollution” and land degradation. Biodegradable film might be a good substitute for PE film in agriculture production, but the evidence for the appropriate biodegradable film mulching pattern for maize is lacking. A 2-year field experiment was carried out to identify a suitable biodegradable film mulching pattern for maize at a typical rain-fed semi-arid site on the Loess Plateau. The local widely cultivated maize variety ‘Luodan 9′ was sown in five planting patterns: 1) conventional flat planting without film mulching (CK); 2) flat planting with full mulching with biodegradable film (FB); 3) ridge-furrow planting with biodegradable film mulching on ridges (RFB); 4) double ridge-furrow planting with full biodegradable film mulching (DRFB) and with full transparent PE film mulching (DRFP). The results indicated that biodegradable film mulching patterns (including FB, RFB and DRFB) significantly increased soil hydrothermal conditions, improved leaf area index, shoot and root biomass, and thus enhanced maize yield and water use efficiency (WUE) in comparison to CK (P < 0.05). Among the three biodegradable film mulching patterns, maize yield and WUE in DRFB (average across two growing seasons) were 9.7% and 11.7% significantly greater than FB, and were 9.9% and 12.2% significantly greater than RFB. In addition, maize yield and WUE in DRFB did not differ significantly from those in DRFP, except that the maize yield was 5.2% (P < 0.05) lower than DRFP in 2013 (a warm and dry season). Present field demonstration clearly indicated that DRFB could serve as a promising option to ameliorate soil hydrothermal conditions, improve maize growth and yield performance, boost WUE, and simultaneously reduce environmental risks such as “white pollution” in rain-fed semi-arid regions of northwest China.

The Role of Polyethylene Wax on the Thermal Conductivity of Transparent Ultradrawn Polyethylene Films.

Transparency and thermal conductivity of ultradrawn, ultrahigh-molecular-weight polyethylene films containing different contents of low-molecular-weight polyethylene wax (PEwax) are explored from experimental and theoretical viewpoints. It is shown that the addition of PEwax decreases light scattering in all directions, resulting from a reduction of defects while having little effect on crystallinity or chain orientation of ultradrawn films. In general, upon the addition of PEwax, the thermal conductivity of ultradrawn films increases with the highest conductivity being 47 (W m–1 K–1) and subsequently decreases at higher concentrations. The thermal conductivity also depends on draw ratio and number-average molecular weight (Mn) of the films. A model is presented which correlates the thermal conductivity of the films with the draw ratio and Mn, enabling explanation of the experimental results. Hence, the thermal conductivity of ultradrawn polyethylene films can be predicted as a function of Mn and draw ratio.

Biofumigation Potentials of Some Brassica Crops to Control Root-knot Nematodes Meloidogyne spp., on Tomato Under Field Conditions

The experiments were conducted to study the efficacy of fodder radish (Raphanus sativus var. Terranovah) and rocket salad (Eruca sativa cv. Baladi) as biofumigation crops for controlling root-knot nematodes Meloidogyne spp., on tomato plants during two successive seasons 2017 and 2018 under field conditions. Three months after cultivation of fodder radish, and rocket salad (the full blooming stage) all parts were incorporated with soil and covered with a transparent polyethylene film. After 4 weeks, the plastic sheets were removed and soil was left for two weeks later, before transplanting tomato seedlings. Results in both seasons, indicated significant reduction (p≤0.05) of nematode parameters on tomato plants. Results revealed that effect of R. sativus var. Terranovah as biofumigation crop as indicated by the percentage reduction in number of galls, egg-masses/root system, and a number of second-stage juvenile (j2) /250 g soil (84, 90, and 84%), and (90,87, and 88%) in seasons 2017 & 2018 respectively. On the other hand, nematicide Vydate (oxamyl) 24% L recorded the percentage reduction in the number of galls, egg-mass/ root system as well as number of second-stage juveniles in soils j2 (90,87, and 87%), and (95,93, and 90%) in season 2017& 2018 respectively. Results revealed that all plant growth criteria on tomato plants increased significantly (p≤0.05) by using the tested treatments. Results indicated that the effect of R. sativus as biofumigation crop recorded the average highest percentages (57, and 92%), and (64, and 102%) in seasons 2017 &2018 respectively. At the same time, nematicide Vydate (oxamyl) 24% L was the most effective in the average highest percentages. i.e., the plant growth vigor, increase, and fruit yield per plant (64, and 98), (73, and 107) in two successive seasons 2017 & 2018 respectively. Gas liquid chromatography-mass spectrometry (GLC-MS) analysis of dichloromethane extract of fodder radish indicated the presence of four glucosinolates, which were identified through their volatile autolysis products. Gluconapin, the major compound was identified by 3- butenyl isothiocynate, while glucoerucin was identified by 4-(methylthio) butyl isothiocynate, which is commonly known as erucin. Sulphoraphane was released from 4-(methylsulfinyl) butyl glucosinolate (glucoraphanin) while 4-(methylsulphony) butyl isothiocyanate commonly known as erysolin was liberated from glucoerysolin. Furthermore, five GLS were also identified in rocket salad. Gluconapin was detected and its presence was identified through its epithionitrile; 4,5-epithiopentanenitrile. The isomers progoitrin and epiprogoitrin were detected by the two hydrolysis products diastereomers threo and erythro 1-cyano-2-hydroxy-3,4-epithiobutane respectively. The aromatic glucosinolate; gluconasturtiin could be identified through its liberated nitrile named as 1-benzenepropane nitrile. Sativin, the major identified compound is 4-mercaptobutyl isothiocyanate.

Effect of hairy vetch (Vicia villosa Roth.) and vetch-rye (Secale cereale L.) biculture cover crops and plastic mulching in high tunnel vegetable production under organic management

ABSTRACTEffects of cover crops on soil physical and chemical properties and yield of the following cash-crops were evaluated in an organic system in a high tunnel. The sequence of crops in the two-year study was: vetch or vetch-rye followed by zucchini (Cucurbita pepo) and then lettuce (Lactuca sativa L) in 2016 and celery (Apium graveolens L.) in 2017. In the plots with cover crops, two mulches (black and transparent polyethylene (PE) film) were used to cover the soil at the end of the first season during the winter period. The differences in the biomass between vetch grown on its own and the vetch-rye mixture were not significant, but the total amount of N accumulated in the biomass of the vetch (252 kg N ha−1) was greater than that of the vetch-rye mixture (174 kg N ha−1). The use of cover crops improved soil properties in the first season (2016), including water stable aggregate index and soil organic matter. In the second season (2017), the use of cover crops combined with PE mulching had a beneficial effect on soil the pH, the water-stable aggregate index, and the availability of Ca, Mg, B and Fe. Covering the soil with black PE mulch during the winter (in both the vetch and the vetch-rye treatments), increased celery yield, compared with the transparent PE mulch and the untreated soil. The use of black PE mulch in the vetch treatment and transparent PE mulch in the vetch-rye treatment reduced soil organic carbon.

Transparent, Lightweight, and High Strength Polyethylene Films by a Scalable Continuous Extrusion and Solid‐State Drawing Process

AbstractThe continuous production of transparent high strength ultra‐drawn high‐density polyethylene films or tapes is explored using a cast film extrusion and solid‐state drawing line. Two methodologies are explored to achieve such high strength transparent polyethylene films; i) the use of suitable additives like 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (BZT) and ii) solid‐state drawing at an optimal temperature of 105 °C (without additives). Both methodologies result in highly oriented films of high transparency (≈91%) in the far field. Maximum attainable modulus (≈33 GPa) and tensile strength (≈900 MPa) of both types of solid‐state drawn films are similar and are an order of magnitude higher than traditional transparent plastics such as polycarbonate (PC) and poly(methyl methacrylate). Special emphasis is devoted to the effect of draw down and pre‐orientation in the as‐extruded films prior to solid‐state drawing. It is shown that pre‐orientation is beneficial in improving mechanical properties of the films at equal draw ratios. However, pre‐orientation lowers the maximum attainable draw ratio and as such the ultimate modulus and tensile strength of the films. Potential applications of these high strength transparent flexible films lie in composite laminates, automotive or aircraft glazing, high impact windows, safety glass, and displays.

Glass-like transparent high strength polyethylene films by tuning drawing temperature

High performance transparent polymeric materials are of great interests in many fields including automotive and electronics. Conventional transparent plastics like polycarbonate (PC) and poly(methyl methacrylate) (PMMA) possess relatively unsatisfactory mechanical performance, while high performance polymeric systems like solid-state drawn high-density polyethylene (HDPE) typically have an opaque appearance, limiting applications where both mechanical and optical properties are required. In this study, we successfully combined high transparency and high strength in HDPE films by carefully controlling processing parameters during solid-state drawing. By tuning the drawing temperature, highly oriented HDPE films with a transmittance of ∼90% are achieved even in the far field. Greater chain mobility at high drawing temperatures is believed to be responsible for fewer defects in the bulk and on the surface of the drawn films, resulting in less light scattering and hence high clarity. These highly transparent films possess a maximum Young's modulus of 27 GPa and a maximum tensile strength of 800 MPa along the drawing direction, both of which are more than 10 times higher than those of PC and PMMA. Results showed that a wide processing window ranging from 90 °C to 110 °C can be used to tailor the required balance between optical and mechanical performance. It is anticipated that these lightweight, low-cost, highly transparent, high strength and high stiffness HDPE films can be used in laminates and laminated composites, replacing traditional inorganic and polymeric glass for applications in automotive glazing, buildings, windshields, protective visors, displays etc.

Integrated model and field experiment to determine the optimum planting density in plastic film mulched rainfed agriculture

Ridge–furrow mulching with plastic film is widespread in northern China because it can significantly improve crop yields. Whether maize grain yield would further increase with higher plant density, due to the better soil moisture conditions under plastic mulch, is unknown. A process-based model (DeNitrification–DeComposition) coupled with a field experiment during the 2014–2015 growing seasons was used to evaluate the effect of plant density on yield. The field experiment included three treatment groups: soil fully covered with transparent polyethylene film (PM) with plant densities 35,000 (PM35), 45,000 (PM45), and 65,000 plants ha–1 (PM65) and bare soil with a maize planting density of 45,000 plants ha–1 as the control (CK). The DNDC simulated yield in PM and CK was well-matched with the measured values and maize growth pattern, and explained 64% of the yield variation and had an RMSE of 176 kg ha–1. At the same planting density (45,000 plants ha–1), individual plant weight, grain weight per plant, 100-seed weight, and grain yield in the non-mulched plots were 45, 28, 52, and 28% of the values for mulched plots, respectively. In the mulched plots, the individual plant size, grain weight, and seed size significantly decreased as planting density increased. The PM65 had 8% and 19% higher grain yield than PM45 and PM35, respectively. Increasing planting density above 45,000 plant ha–1 in the PM resulted in a small but non-significant increase in grain yield. We concluded that increasing plant density in PM will not necessarily increase maize yield, and the optimum planting density could be determined by combining the field experiment with the model.