In this study, three different sizes of tripolyphosphate‐modified expandable graphite (EGp) are prepared and incorporated into rigid polyurethane foam (RPUF) in order to obtain a flame retardant material with low density, good mechanical properties, and hydrophobicity. The influence of particle size on material combustibility, thermal stability, compression strength, pore cell structure, diathermancy, and hydrophobic property is investigated. Synergistic effect between the EGp and ammonium polyphosphate (APP II) is also examined. Results show the limiting oxygen index value and residue yield increase as the EGp size increases. On the contrary, the heat release rate and total heat release decrease as the EGP size increases. In addition, the chemical char formation effect of APP on RPUF is more important than the char formation of the graphite intercalation compounds. EGp and APP show synergistic effect in improving flame retardancy, thermal stability, and hydrophobicity. POLYM. ENG. SCI., 59:1381–1394 2019. © 2019 Society of Plastics Engineers

Influence of independent Mg-Al-layered double hydroxide (LDH), silicate modified expandable graphite (EG), mixture of LDH and EG at various ratios on ethylene vinyl acetate copolymer (EVA) combustion behavior and thermal stability was detected in sequence through the limiting oxygen index (LOI), vertical combustion (UL-94) level, microscale combustion calorimeter (MCC) tests and thermal gravimetric/differential thermal gravimetric (TG/DTG) analysis. Results show that the 30 wt % LDH can improve the LOI of 70EVA/30LDH to 27.0%, but the combustion accompanies with serious melt-dropping. While, the same amount of the EG can increase the LOI, UL-94 level to 28.5%, V-0 respectively. However, the combination of LDH and EG can further enhance the 70EVA/20LDH/10EG flame retardancy, it presents the LOI of 29.7%, UL-94 level of V-0, and total heat release of 29.5 kJ g 21 . The excellent flame retardancy is attributed to its compact residue. Compared with residue mass, the residue compactness plays a more important role in improving flame retardancy.

A borate-modified expandable graphite (written as MEG) was prepared through one step intercalating reaction of natural graphite, using KMnO 4 as oxidant, H 2 SO 4 and sodium tetraborate as intercalator and assistant intercalator, respectively. The dilatability, structure, element contents, thermal stability, and flame retardancy on acrylonitrile-butadiene-styrene (ABS) were investigated. Compared with the normal expandable graphite (written as EG, which was prepared with only H 2 SO 4 as intercalator), the results show that MEG exhibits higher expandable property, thermal stability and flame retardancy on ABS. The EDS, FT-IR, and XRD results reveal that borate has been inserted into graphite layers. With the addition of MEG or EG at a 30 wt%, LOI of 70ABS/30MEG composite improved to 27.9%, 2.2% higher than that of 70ABS/30EG. Moreover, the synergistic effect between MEG and traditional intumescent flame retardant (IFR, consists of ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL) with a mass ratio of 7.5:4.5:3.0) improves the LOI of 70ABS/15MEG/15IFR composite to 32.6%, and the UL-94 level reaches V-0. This synergistic efficiency is attributed to the formation of continuous and compact residual char. Addition of MEG together with IFR changes the ABS pyrolysis behavior, and there is not only physical synergy, but also chemical reaction. POLYM. COMPOS., 37:2673-2683, 2016.

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Tomato was cultured in an organic substrate with two parts vermiculite and one part sheep manure. The effects of different chemical fertilizer application doses on N, P and K absorption and utilization of tomato were investigated under solar greenhouse conditions. Based on the results, N, P and K absorption and yield of tomato were enhanced by proper fertilizer application. The amount of N, P and K absorbed increased with the increasing chemical fertilizer dose. Also the utilization rate of N and K in organic substrate decreased with increasing fertilizer dose. However, the utilization rate of P increased with increasing of fertilizer dose. Furthermore, transformation of slow-releasing nutrients to available nutrient improved by proper fertilizer application. Under the organic cultivation, producing 1 000 kg tomato required 2.540 kg N, 0.751 kg P, 4.347 kg K. The calculation method of optimal chemical fertilizer dose under organic substrate culture was advanced in the study. The calculation formula was: chemical fertilizer dose = (1.5 times fertilizer dose needed for target yield − available nutrient content in organic substrate)/chemical fertilizer nutrient uptake ratio.