Black Low-density Polyethylene Research Articles

Biodegradable Mulching Film vs. Traditional Polyethylene: Effects on Yield and Quality of San Marzano Tomato Fruits.

Mulching is a common practice for improving crop yield and obtaining an out-of-season production, but when made using plastic materials it can bring environmental problems due to the management and the disposal of films at the end of the cropping seasons. To increase the sustainability of this practice, recently, mulching films made with biodegradable organic materials have become more widely used. Our aim was to evaluate the effect of a biodegradable mulching film on yield and qualitative traits of the San Marzano tomato fruits over two years (2014 and 2015). Two different types of mulching were tested: (i) black biodegradable film (MB12) and (ii) black low-density polyethylene (LDPE) were compared to bare soil (BS). Both mulching films elicited a 25% increase in yield, mainly due to the significantly higher number of fruits per square meter, compared to BS. Both mulching films also elicited a 9.9% increase in total soluble solids and a 57% increase in carotenoid content, while firmness showed the highest value in BS fruits. MB12 determined the highest value of the Hunter color ratio a/b of tomato fruits, followed by LDPE, while the lowest value was recorded in BS fruits. Both mulching films elicited an increase of 9.6%, 26.0%, and 11.7% for flavonoids, polyphenols, and AsA, respectively. In 2014, the MB12 degradation started at 71 days after transplant (DAT); in 2015, at 104 DAT. Therefore, replacing polyethylene with biodegradable film would seem to be an agronomically efficient and environmentally sustainable practice.

Biodegradation of low-density polyethylene (LDPE) using the mixed culture of Aspergillus carbonarius and A. fumigates

Low-density polyethylene (LDPE) possesses various applications in several industries owing to its durability, low-cost, and many mechano-thermal properties. Unfortunately, LDPE waste creates an environmental threat. The level of biodegradation of black LDPE sheets with fungi isolated from different landfills sites in Sharqiyah Governorate, Egypt, was evaluated. LDPE sheets, the only source of carbon, along with minimal salt medium were incubated on a rotary shaker at 30 °C and 120 rpm for 16 weeks. Aspergillus carbonarius MH 856457.1 and A. fumigatus MF 276893 confirmed to be good candidates for LDPE biodegradation. A mixed culture of two strains showed the excellent weight loss% of sheets as compared to single isolate. Further efforts to improve the degrading capacity through physical and chemical treatments were performed. The biodegradation was significantly stimulated by 39.1% (thermal treatment), 17.76% (HNO3 treatment), and 5.79% (Gamma-irradiation treatment). Laccases and manganese peroxidases activities were assayed. LDPE biodegradation was analyzed by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and gas chromatography–mass spectrometry (GC–MS). FTIR spectra showed the appearance of new functional groups assigned to hydrocarbon biodegradation and confirmed the role of manganese peroxidase in process. The changes in the FTIR spectra of the mixed culture biomass before and after the biodegradation (Δ73 cm−1) and the surface changes in the biodegraded LDPE (as indicated from SEM) confirmed the depolymerization of LDPE. From GC–MS analysis, the plasticizers bis(2-ethylhexyl) phthalate, Diisssctyl phthalate, 1,2-benzenedicarboxylic acid diisooctyl ester, and tributyl acetylcitrate completely biodegraded. Moreover, several antioxidants, antimicrobial, and anticancer compounds, and methyl esters of fatty acids were produced.

Opposed-Flow Flame Spread and Extinction in Electric Wires: The Effects of Gravity, External Radiant Heat Flux, and Wire Characteristics on Wire Flammability

Combustion of electric wires is the most probable cause of fire in human space activities. Therefore, the fire performance of electric wires in microgravity conditions must be thoroughly analyzed. This study investigates the opposed-flow flame spread and its limits in electric wires preheated by external radiation, under both normal gravity and microgravity, to understand their fire performance when exposed to external heat sources in such gravity conditions. The experiments were performed on low-density polyethylene (LDPE)-insulated copper (Cu) wires having an outer diameter of 4 mm and differing in core diameter (2.5 and 0.7 mm, corresponding to insulation thicknesses of 0.75 and 1.65 mm, respectively). Both standard and black LDPE insulations were used to study the effect of radiation absorption on the wire preheating and subsequent flame spread. The comparison of the flame spread limits revealed that the wire with the thicker Cu core was less flammable under both normal gravity and microgravity; in particular, its flammability further decreased in the case of microgravity, in contrast with thinner electric wires (~ 1 mm outer diameter), which exhibited higher flammability in the same gravity condition. These results suggest that different mechanisms, for thicker and thinner wires, determining the critical conditions to sustain flame spread under microgravity. This study provides valuable information about the fire performance of electric wires in space gravity.

The effect of novel biodegradable films on agronomic performance of zucchini squash grown under open-field and greenhouse conditions

The soil mulching is an important agricultural practice for increasing crop productivity and earliness. Mulching can be made with natural or synthetic materials. The common films being used these days are usually made of low density polyethylene (LDPE), but its disposal can represent a serious environmental and economic problem. The biodegradable mulching can overcome these problems. Two experiments were carried out comparing the effects of biodegradable and LDPE mulching films on yield and quality of zucchini (Cucurbita pepo L.) grown in two environments (open-field vs. greenhouse). In both the environments a randomized complete block design was adopted. The treatments composed of no-mulched crop (control), soil covered by 15 microns black biodegradable film (MB15) and soil covered by 50 microns black LDPE film. The results showed that MB15 was able to maintain discrete technical proprieties until the end of cycle, especially in greenhouse, assuring a sufficient heating of soil, similar to LDPE. The soil heating promoted crop development. Furthermore, earliness was increased (84 in greenhouse vs. 99 days in open air) in greenhouse. The early production of zucchini grown on MB15 was similar to the one in LDPE production in greenhouse. The total marketable yield of plants grown on both films was not different but it was lower in open air. The biodegradable film significantly improved fruits quality, with higher values of firmness and total soluble solid than fruits grown on LDPE.

Teores de clorofila nas plantas e produtividade de frutos de morangueiros cultivados sobre mulching

This study aimed to evaluate productive characteristics and levels of photosynthetic pigments in two strawberry cultivars on different types of mulching, in an open cultivation system. The experiment was a 2 x 4 factorial completely randomized block design, with 2 varieties (Camarosa and Camino Real) and 4 ground covers (black low-density polyethylene, silver low-density polyethylene, non-woven and no mulching), with three replications. The cultivars were analyzed for chlorophyll a and b content, total chlorophyll, and chlorophyll a/b ratio, number of fruits per plant, yield (ton ha-1), weight fruit mass, soluble solids (oBrix), total acidity, pH and soluble solids/total acidity ratio. The Camarosa showed higher yield than cv. Camino Real. The silver low-density polyethylene and non-woven mulching treatment exhibited negative results, and are not recommended for the cultivation of Camarosa and Camino Real strawberries. The black low-density polyethylene mulching was the most recommended for growing such cultivars. Among the types of mulchings evaluated, the black low-density polyethylene achieved the best results and it is recommended for the Camarosa and Camino Real strawberry cultivars.

Effect of plastic mulch and burial depth on purple nutsedge (Cyerperus rotundus) emergence and growth

ABSTRACTCyperus rotundus L. causes high yield losses in fruiting vegetables and cucurbits in eastern and southeastern parts of Iran. Greenhouse and field experiments were conducted to investigate the effect of mulch type (1- and 2-layer black and clear low-density polyethylene (LDPE) sheets as well as a non-mulched control) and tuber burial depth (0, 2.5, 5, 10, 20, 30, 40, and 50 cm) on C. rotundus above- and belowground growth. All experiments were conducted using three different populations from Birjand, Kahnooj, and Jiroft. It was found that the greatest suppression of C. rotundus growth in all populations was observed in plots covered with 2-layer black LDPE, so that no above- or belowground growth was found with this type of LDPEs. It was also concluded that C. rotundus can emerge from tuber burial depths in the range of 30–50 cm depending on the population studied, indicating mechanical operations that bury the tubers in soil depths even as deep as 50 cm (e.g. moldboard ploughing), cannot guarantee to suppress the emergence and tuber production of this noxious weed species. Our study clearly showed that using a 2-layer black LDPE can be recommended as a promising technique for the control of C. rotundus rather than implementing a deep tillage.

Rolled Cotton Mulch as an Alternative Mulching Material for Transplanted Cucurbit Crops

Cantaloupe and watermelon growers in the southeastern United States use a system of hybrid transplants grown on narrow low-density polyethylene (LDPE) mulch-covered seedbeds with overhead irrigation and use the mulch cover for only one crop. LDPE mulches are costly to remove from the field and dispose. Biodegradable mulches that eliminate removal and disposal costs would be of significant benefit, provided that weeds are adequately suppressed. Cotton gin trash is a biodegradable waste product, composed of fiber fragments and seed pieces. Using a proprietary process, cotton gin trash can be chopped, pressed, and heated into a loose mat and stored on a continuous roll. Preliminary studies were conducted in 2010 and 2011 to determine if rolled cotton fiber mulch made from gin trash could be applied as a seedbed cover using conventional application equipment and adequately suppress weeds. Mulching materials (rolls 91 cm wide) were applied with a mulch layer that produced a finished seedbed 40 cm wide. ‘Athena' cantaloupe and ‘Crimson Sweet' watermelon were transplanted using a waterwheel transplanter. Mulching materials included rolled cotton fiber mulch sprayed with boiled linseed oil after mulch application, rolled cotton fiber mulch sprayed with black latex paint, black LDPE, and bare ground. Herbicide treatments included ethalfluralin, halosulfuron, and glyphosate applied as directed spray and nontreated with herbicides. Rolled cotton fiber mulch was easily applied with a conventional mulch layer with no modification and minimal adjustment, producing no tears or holes. Biodegradable cotton fiber mulch treated with boiled linseed oil or black latex paint suppressed weeds equally well as LDPE and all were better than bare-ground plots. Herbicides improved control of all weeds over the nontreated control and this effect was independent of weed suppression provided by seedbed mulches. Cantaloupe and watermelon yields were not affected by seedbed mulches, but were increased by weed control provided by herbicides.

Expanded microchannel heat exchanger: design, fabrication, and preliminary experimental test

This article first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This article presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effectiveness. This article discusses one possible joining method – a new type of laser welding named ‘forward conduction welding’, used to fabricate the prototype. The expanded heat exchanger has the potential to have counter-flow, cross-flow, or parallel-flow configurations, be used for all types of fluids, and be made of polymers, metals, or polymer–ceramic precursors. The cost and ineffectiveness reduction may be an order of magnitude or more, saving a large fraction of primary energy. The measured effectiveness of the prototype with 28 µm thick black low-density polyethylene walls and counterflow, water-to-water heat transfer in 2 mm channels was 72 per cent, but multiple low-cost stages could realize the potential of higher effectiveness.

Barriers Prevent Emergence of Yellow Nutsedge (Cyperus esculentus) in Annual Plasticulture Strawberry (Fragaria × ananassa)

Yellow nutsedge is a problematic weed in plasticulture strawberry because herbicides and fumigants currently used in California provide little to no control and because nutsedge shoots easily penetrate standard low-density polyethylene (LDPE) mulch to rapidly establish and compete with the crop. Field studies were conducted at two California locations near Oxnard and Camarillo from 2007 to 2009 to evaluate yellow nutsedge control with physical barriers. Nutsedge germinated in both autumn and spring through LDPE mulch alone, but paper placed between two layers of standard 0.15-mm black LDPE mulch, weed barrier fabric commonly used in landscapes placed under LDPE mulch, and Tyvek Home Wrap placed under LDPE mulch suppressed nutsedge emergence. In 1 yr, the size of strawberry plants grown with weed barrier fabric was reduced 23% compared with the other treatments and the number of marketable fruit in the third month of harvest was reduced 20% compared with LDPE mulch alone, likely because inadequately cut planting holes in this barrier restricted plant growth. Estimated costs for barrier treatments ranged from $5,000 to $12,000 ha−1compared with estimated hand-weeding costs of up to $24,000 ha−1. In 2007 to 2008 barrier treatments reduced the number of wind-dispersed weeds that commonly land and germinate in strawberry planting holes 67% compared with LDPE mulch alone. Removing the barriers at the end of the two seasons revealed that nutsedge plants sprouted but failed to grow and produce new tubers under the barriers. This observation suggests that nutsedge-impermeable barriers may aid in depletion of the soil tuber bank and therefore can be an effective tool in managing nutsedge for the length of the growing season.

Cultural control of yellow nutsedge ( Cyperus esculentus) in transplanted cantaloupe ( Cucumis melo) by varying application timing and type of thin-film mulches

Irrigated field trials were conducted in Tifton, GA, at the Coastal Plain Experiment Station to determine the effectiveness of thin-film mulch application times and mulching materials in suppressing yellow nutsedge in transplanted cantaloupe production. Thin-film mulches were applied to freshly tilled seedbeds the day of transplanting, 1, 2, and 3 weeks prior to transplanting. Mulching materials were clear, black, and white on black low-density polyethylene (LDPE), along with a non-covered (bareground) control. Yellow nutsedge emergence in transplanted cantaloupe was suppressed by the combined effects of a physical barrier provided by thin-film mulches and competitive size differential provided by using cantaloupe transplants. All of the thin-film mulches applied to freshly prepared seedbeds either the day of transplanting or 1 week before transplanting effectively suppressed yellow nutsedge in transplanted cantaloupe production, without the need for fumigants or herbicides. Yellow nutsedge suppression in bareground seedbeds freshly prepared within 1 week of transplanting was nearly as effective as suppression from thin-film mulches. Seedbed preparation and applying thin-film mulch 2 or 3 weeks before transplanting did not effectively suppress yellow nutsedge and cantaloupe yields were reduced. In systems where soil fumigation and herbicide use are not possible, yellow nutsedge can be effectively suppressed and crop yields protected by applying thin-film mulches immediately prior to transplanting cantaloupe.

Early detection of degradation in a semi-crystalline polyolefin by a successive self-nucleation and annealing technique

Samples taken from a black pipeline liner that became fragile while in service were analyzed by a Successive Self-Nucleation and Annealing (SSA) technique. Two types of polyethylene, Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) were aged in air, at several temperatures, and changes in the molecular structure were followed simultaneously by infrared and calorimetric techniques. Samples with and without antioxidants were prepared, aged, and evaluated for the same oxidative treatments. The LDPE type was chosen to be identical to the black LDPE originally used for making the pipeline liner. Oxidative reactions of LDPE and LLDPE were quantified via carbonyl group concentrations measured by FTIR. Changes in the crystallization behavior of the original and aged polymers, and of the black pipeline liner, were monitored via the SSA technique. Changes of the fraction of lamellae of specific thickness in the crystallized polymer could be correlated linearly with the formation of carbonyls, and thus this calorimetric method is proposed to be suitable as a tool for early quantitative monitoring of LDPE degradation.

Efficacy of Mulches and Methyl Bromide Alternatives on Soilborne Pests and Weeds in Spring Tomato

Tomato (Lycopersicon esculentum Mill.) field studies were conducted to determine the impact of mulch types combined with soil fumigants on spring tomato yields and on soilborne pests and weeds. Fumigants were: a) untreated control, b) methyl bromide + chloropicrin (67/33%, respectively) at a rate of 400 kg haG , c) chloropicrin at 400 kg haG plus the herbicide pebulate at 4.5 kg haG , d) 1,3-dichlopropene 1 1 1 at 325 kg haG + chloropicrin at 67 kg haG (83/17%, respectively) plus pebulate at 4.5 kg haG and e) metam 1 1 1 sodium at 485 kg haG plus pebulate at 4.5 kg haG . Mulch types were either black low-density polyethylene film 1 1 (0.038 mm thick) or black paper mulch. Results indicated that all fumigants with either mulch type had higher tomato yield and more effective soilborne disease and purple nutsedge (Cyperus rotundus L.) control than the non-fumigated control. Paper mulch appeared to be a valuable alternative to control purple nutsedge with no fumigants and with low-volatility fumigants, such as metam sodium, whereas plastic mulch might retain high-volatility fumigants, such as methyl bromide, longer, thus increasing efficacy.

MANAGEMENT OF THE SILVERLEAF WHITEFLY ON FRESH MARKET TOMATOES WITH SOIL AND FOLIAR INSECTICIDE APPLICATIONS, SPRING 2002

On 28 Feb, transplants were set 18 inches apart on raised beds of EauGallie fine sand soil covered with white on black low density polyethylene mulch. Plots were three, 21-ft-long rows on 10-ft aisles and 5-ft centers and were irrigated by a seepage sub-irrigation system. Treatments were replicated four times in a RCB design. Admire, Platinum and V-10112 were applied on 28 Feb to each plant in 4 oz of water. Activol, Aza-Direct and Hexacide were applied weekly. The remaining products were to have been applied at the pre-determined density of five whitefly sessile nymphs and/or pupae/10 leaflets (Table 1); however, on 9 May only treatments with Oberon were applied before uncontrollable circumstances stopped spraying. All treatments were applied on 26 May. Foliar applications were made with a high clearance, self-propelled sprayer operated at 200 psi and 3.4 mph. It was fitted with eight Albuz orange nozzles per row and delivered 90 (six nozzles open) or 120 (eight nozzles open) gpa. Because of a heavy population of southern armyworm larvae, Javelin (2 lb/acre), XenTari (2 lb/acre), Confirm 2F(16 oz/acre) or Avaunt 30WG (3.5oz/acre) were applied weekly. The number of plants in each plot with definite visual symptoms of whitefly-vectored geminivirus, primarily tomato yellow leaf curl virus (TYLCV), were recorded weekly beginning 19 Mar. The numbers of sessile nymphs (2nd and 3rd instars) and pupae (4th instar or red eye nymphs) of the silverleaf whitefly were counted on the terminal leaflet from the 7th to 8th leaf counting from the top of each of ten plants in the center row of each plot about weekly beginning on 31 Mar. Fruit were harvested on 4 Jun from the middle 10 plants of the middle row of check plots and plots treated only with either Admire or Platinum. Fruit with zippering, cat-facing or large blossom-end scars were culled as defective and counted and weighed. The remaining fruit were graded for size by machine where extra large fruit were > 2.75 inches in diam, large were 2.51 to 2.75 inches in diam, medium were 2.26 to 2.5 inches in diam and small were ≤ 2.25 inches in diam. All size categories were counted and weighed. Small fruit are considered too small for marketing and are culled.

Influence of filler structure on microhardness of carbon black-polymer composites

The microhardness, H, of carbon black–polycarbonate and carbon black–low-density polyethylene composites was investigated. Two types of microadditives with different average particle sizes were employed. It has been shown that the morphology of the polymeric matrix conspicuously influences the hardness dependence of the composites with volume concentration of filler, ϕ. The microhardness of the carbon black–polycarbonate composites shows a steplike behavior with respect to carbon black content, while the H value of the carbon black–low-density polyethylene composite linearly increases with increasing ϕ. The influence of filler structure on the microhardness of the carbon black–polymer composites is also discussed. Results favor the concept that a smaller carbon black particle size (smaller aggregate diameters and interaggregate distances) enhances the microhardness of the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 90–95, 2001