A Novel Method to Prepare Transparent, Flexible and Thermally Conductive Polyethylene/Boron Nitride Films

The high thermal conductivity and good insulating properties of boron nitride (BN) make it a promising filler for high-performance polymer-based thermal management materials. An easy way to prepare BN-polymer composites is to directly mix BN particles with polymer matrix. However, a high concentration of fillers usually leads to a huge reduction of mechanical strength and optical transmission. Here, we propose a novel method to prepare polyethylene/boron nitride nanoplates (PE/BNNPs) composites through the combination of electrostatic self-assembly and hot pressing. Through this method, the thermal conductivity of the PE/BNNPs composites reach 0.47 W/mK, which gets a 14.6% improvement compared to pure polyethylene film. Thanks to the tight bonding of polyethylene with BNNPs, the tensile strength of the composite film reaches 1.82 MPa, an increase of 173.58% compared to that of pure polyethylene film (0.66 MPa). The fracture stress was also highly enhanced, with an increase of 148.44% compared to pure polyethylene film. Moreover, the addition of BNNPs in PE does not highly reduce its good transmittance, which is preferred for thermal management in devices like light-emitting diodes. This work gives an insight into the preparation strategy of transparent and flexible thermal management materials with high thermal conductivity.

Study of the efficiency of sweet potato growing in the Forest-Steppe of Ukraine by different methods of soil mulching

Sweet potato (Ipomoea batatas L.) is a new crop for soil and climatic conditions of Ukraine, the active implementation of which is hindered by the lack of recommendations on technological aspects of cultivation. One of the important technological measures for growing sweet potatoes is the use of soil mulching, which improves the water regime and regulates the thermal regime of the soil; prevention of weed growth and growth of sweet potato shoots to the soil. Thus, the aim of the research is to determine the efficiency of growing sweet potatoes in the Forest-Steppe of Ukraine by different methods of soil mulching. Field research was carried out on typical low-humus light loamy chernozem on loess loam. It was noted, that when growing sweet potatoes on ridges, the introduction of mulching the soil with black polyethylene film provides more active growth of the vegetative mass throughout the growing season (5.33 shoots/plant with a total length of 252.1 cm), while growing without ridges has a positive effect on plants growth due to the general absence of mulch (2.53 shoots/plant with a total length of 107.8 cm). The use of ridges and mulching the soil with black polyethylene film causes the yield of sweet potato tubers at 34.8 t/ha, while the mulching of the soil with straw, the yield was 18.3–21.9 t/ha, without mulching – 13.0–17, 1 t/ha. Mulching with black polyethylene film ensures the accumulation of vitamin C and starch in sweet potato tubers. When growing the culture on ridges by this method of mulching, the maximum level of vitamin C according to the experiment (4.78 mg/100 g) and starch (11.73 %) was noted. The introduction of mulching and ridge formation involves additional material and labor costs, but helps to reduce weed control and tuber digging costs. When growing sweet potatoes on ridges with mulching with black polyethylene film, the minimum additional labor costs for the formation of a unit of yield (1.95 man-minutes/kg of tubers) were noted, while without mulching and without ridges this figure was 6.76 man-minute/kg

Pigments in flower stems of lisianthus under different photoselective shade nets

The lisianthus culture is demanded to produce cut flowers and pot vases, grown in a greenhouse using advanced techniques. The present study aimed to evaluate the pigments of different lisianthus cultivars in different photoselective shade nets. The cultivars Flare Deep Rose (pink), Echo Blue BL (purple) and Allemande White BI (white) were cultivated under light-diffusing polyethylene film cover and blue and red color photoselective nets with a shading capacity of 30%, in addition to the control treatment, without the use of the net. The results showed higher values of chlorophyll b and total in the red photoselective net, independent of the cultivar. Leaf colorimetry showed the most intense shade of green was from the cultivar Echo Blue BL. On the other hand, the control showed more intensity, with no significant difference in the leaf green intensity on the blue and red shade nets. In the petals, the cultivar Echo Blue BL showed a more intense blue shade in the red net, however low grade of anthocyanin than in the blue one. In the anthocyanin pigment, this cultivar had lower levels in the treatment of the red net. The results indicate that the use of photoselective shade nets in the culture of lisianthus changes the content of the pigments studied, in varying intensity, depending on the cultivar.

Preparation and Evaluation of the Polyethylene Film Deposited With a Multilayer Graphene Membrane for Tensile Properties

This study aims to improve the tensile properties of the polyethylene film deposited with a multilayer graphene membrane, in order to establish the understanding of the influence of the methane to hydrogen ratio on the tensile properties of the multilayer graphene membrane. Multilayer graphene membranes were prepared using the chemical vapor deposition method. Four types of multilayer graphene membranes were prepared with different ratios of methane to hydrogen before depositing a membrane on the polyethylene film. Experiments showed that the tensile strength of the polyethylene films with multilayer graphene deposition increased 7 times and the Young’s modulus 5 times more than that of pure polyethylene films, when the ratio of methane to hydrogen was set to 35/100 sccm. A compromise between hydrogen and methane mixture is required to achieve uniform growth of graphene. Insufficient hydrogen cannot activate the surface bound carbon that is necessary for continuous growth. Continuous and well-defined multilayer graphene was synthesized when the ratio of methane to hydrogen reached up a proper value.