Fire Resistance, Thermal and Anti-Ageing Properties of Transparent Fire-Retardant Coatings Modified with Different Molecular Weights of Polyethylene Glycol Borate

Four kinds of polyethylene glycol borate (PEG-BA) with different molecular weights were grafted into cyclic phosphate ester (PEA) to obtain flexible phosphate esters (PPBs), and then applied in amino resin to obtain a series of transparent intumescent fire-retardant coatings. The comprehensive properties of the transparent coatings containing different molecular weights of PEG-BA were investigated by various analytical instruments. The transparency and mechanical analyses indicate that the presence of PEG-BA slightly decreases the optical transparency of the coatings but improves the flexibility and adhesion classification of the coatings. The results from fire protection and cone calorimeter tests show that low molecular weight of PEG-BA exerts a positive flame-retarded effect in the coatings, while high molecular weight of PEG800-BA behaves against flame-retarded effect. Thermogravimetric and char residue analyses show that the incorporation of low molecular weight of PEG-BA clearly increases the thermal stability and residual weight of the coatings and generates a more compact and stable intumescent char on the surface of the coatings, thus resulting in superior synergistic flame-retarded effect. In particular, MPPB1 coating containing PEG200-BA exerts the best flame-retarded effect and highest residual weight of 36.3% at 700 °C, which has 57.6% reduction in flame spread rate and 23.9% reduction in total heat release compared to those of MPPB0 without PEG-BA. Accelerated ageing test shows that low molecular weight of PEG-BA promotes to enhance the durability of structural stability and fire resistance of the coatings, while PEG800-BA with high molecular weight weakens the ageing resistance. In summary, the fire-resistant and anti-ageing efficiencies of PEG-BA in the coatings depend on its molecular weight, which present the order of PEG200-BA > PEG400-BA > PEG600-BA > PEG800-BA.

Multi-source localization by using offset residual weight

Multiple sound source localization is a hot issue of concern in recent years. The Single Source Zone (SSZ) based localization methods achieve good performance due to the detection and utilization of the Time-Frequency (T-F) zone where only one source is dominant. However, some T-F points consisting of components from multiple sources are also included in the detected SSZ sometimes. Once a T-F point in SSZ is contributed by multiple components, this point is defined as an outlier. The existence of outliers within the detected SSZ is usually an unavoidable problem for SSZ-based methods. To solve this problem, a multi-source localization by using offset residual weight is proposed in this paper. In this method, an assumption is developed: the direction estimated by all the T-F points within the detected SSZ has a difference along with the actual direction of sources. But this difference is much smaller than the difference between the directions estimated by the outliers along with the actual source localization. After verifying this assumption experimentally, Point Offset Residual Weight (PORW) and Source Offset Residual Weight (SORW) are proposed to reduce the influence of outliers on the localization results. Then, a composite weight is formed by combining PORW and SORW, which can effectively distinguish the outliers and desired points. After that, the outliers are removed by composite weight. Finally, a statistical histogram of DOA estimation with outliers removed is used for multi-source localization. The objective evaluation of the proposed method is conducted in various simulated environments. The results show that the proposed method achieves a better performance compared with the reference methods in sources localization.

Visual and Keeping Quality of Stored Bulb Onions as Affected by Harvest and Postharvest Treatments

Productivity of onion (Allium cepa L.) in Kenya is constrained by postharvest losses. Most postharvest strategies applicable to onions are applied singularly, and therefore, their combined effects have not been well studied. This study evaluated the combined effects of harvesting stage, curing period, and time of topping on postharvest visual and keeping quality of red bulb onions. The study was carried out in Yatta Sub-County, Machakos County, Kenya. The experimental design was a split-split plot laid out in 3 × 3 × 2 factorial arrangement. The treatments consisted of harvesting stage (25%, 50%, and 75% top fall), curing period (none, 1 week, and 2 weeks) and time of topping (before and after curing). After three months of storage, the bulbs were assessed for visual and keeping quality using incidences of skin rots, skin colour, percent of marketable bulbs, residual weight of the bulbs after curing, and days to 50% sprouting. Bulbs that were harvested at 75% top fall and cured for one or two weeks before topping were found to have significantly better visual and keeping quality. Although seasonal variations were significant for some of the parameters assessed, a similar trend was observed in both seasons. The study recommends harvesting of onions at 75% top fall and curing for at least one week before topping for enhanced visual and keeping quality of harvested bulb onions.

The structural transformation and reburning characteristics of gas coal in Ningwu coalfield fire

With the expansion of the scale of coal mining, the safety problems caused by the reburning of coal are becoming more and more serious. In this paper, the pyrolysis characteristics of gas coal and the exothermic characteristics of reoxidation of residues were studied by using a synchronous thermal analyzer. The functional groups of pyrolysis residues were tested, and the group content and characteristic structural parameters were calculated based on quantum chemistry method. The results show that with the increase of pyrolysis temperature, Volatile maximum separation rate (Vmax) and the change in the residual weight of the coal sample (ΔWvp) increase. The increase of temperature will lead to the decrease of hydroxyl and aliphatic hydrocarbon content in coal, and the increase of aromatic hydrocarbon. With the deepening of pyrolysis, the ignition point temperature of coal samples decreases first and then rises, the combustion intensity and combustion concentration are strengthened. The pyrolysis results show that 462.8°C is the critical temperature for the transition during pyrolysis. The ignition point of the residue is less affected by the pyrolysis conditions, and the ignition temperature of the raw coal and the pyrolysis residue varies within 330.57°C–334.98°C.

Modifikasi Polietilen sebagai komposit Plastik Polimer Biodegradable dengan Filler Tepung Kulit Pisang Talas

Synthetic polymer polyethylene LDPE has been grafted with natural polymers of banana talas (Musa paradisiacal Var sapientum L.) peels flour. The aim of this research is to make compossed plastic of the thermoplastic banana peels flour with LDPE resins plastic based on mechanic and degradation behaviours. Low Density Polyethylene (LDPE) resins, glycerol, banana peels, humus soil, xylene p.a as the raw materials. Thermoplastic banana peels flour produced by added 30% glycerol concentration and then by aging for 2 weeks. The mixing of the thermoplastic banana peels flour with LDPE resins using a ratio of 1:3, 2:3 and 3:3. Xylene (coupling agent) 6 times of the total mass were added to increase compatibility between thermoplastic banana peels flour and LDPE. The mechanical properties of composite were analyzed using ASTM D638 method and the biodegradation capability composite were charactherized using soil burial test method. The results show that tensile strength in the ratio of 1:3, 2:3, 3:3 respectively were 28.94 kg/cm2, 36.16 kg/cm2, 29.94 kg/cm2. The percentage of residual weight show the biodegradation capability in the ratio of 1:3, 2:3, 3:3 was 98.46%, 97.67%, 98.24%. Mixing ratio of 2:3 thermoplastic banana peels flour and LDPE has the best value of tensile strength and degradation capability. Mixing ratio of 2:3 thermoplastic banana peels flour and LDPE has the best value of tensile strength and degradation capability.

Physicochemical Analysis of Graphene Oxide-Reinforced Cassava Starch Biocomposites

Despite the proven application of cassava starch as biocomposites, the starch still has several drawbacks in physical and mechanical properties that need to improve to ensure its commercialization in the future. Thus, in this study, the modification of cassava starch-based (CP) properties was made by adding graphene oxide (GO) filler into cassava starch solution via starch intercalation method. Several physicochemical analyses were performed using Fourier-Transform Infrared (FTIR) Spectrometer and Scanning Electron Microscopy (SEM). The effects of GO content in different concentrations to the mechanical, water uptake, biodegradation, and fungi observation under the microscope were also determined. FTIR spectra of GO-reinforced cassava exhibited all significant peaks from CP and GO present. SEM images show an irregular texture and layered structure of GO. The biocomposites produced from 10% GO (C10) has superior properties with a tensile strength of 1.60 MPa, Young Modulus of 189 MPa, and elongation at a break of 2.88 mm. The decrease of residual weight and water uptake percentages at higher concentrations of GO elucidate the biocomposites' enhanced properties. The improved resistance against fungus also resulted from the incorporation of GO into the cassava starch matrix.

SiBCN ceramic precursor modified phthalonitrile resin with high thermal resistance

In order to expand the application of phenolic-type phthalonitrile resin in high-temperature fields, a series of organic–inorganic hybrid materials have been prepared via conventional blending and doping method. The chemical transformations were monitored by various measurements, while the curing behavior was evaluated by differential scanning calorimetry (DSC), and these new blends could be also cured under auto-catalytic process. The onset polymerization exothermic temperature shifted to lower temperatures (195.3°C). Later, the compatibility within the cured products was analyzed by using energy dispersive spectrometer (EDS) and scanning electron microscope (SEM), where no phase separation occurred between the ceramic domain and the phthalonitrile polymer. Upon curing, the thermal properties of the polymers were characterized by dynamic thermomechanical analysis (DMA) and thermogravimetric analysis (TGA), where enhanced heat resistance and thermal stability were discovered, The blends residual weight (Cy) value was 57.6% with 15 wt.% SiBCN at 1000°C. And when blended with SiBCN precursor, no peak or onset point could be observed in the temperature range (50 to 500°C), which indicated the glass transition temperature greater than 500°C. Additionally, the dielectric properties were evaluated. And when the content was 5 wt.%, the blends dielectric loss was 0.0043 and the permittivity was 4.31. The above results indicated that the introduction of ceramic precursors could enhance the thermal performance of phthalonitrile polymers, consequently the hybrid materials shown great potential in the application of higher temperature fields.

Thermal and fire properties of medium-density fiberboard prepared with huntite/hydromagnesite and zinc borate

Effects of mineral-based fire retardants were investigated relative to the thermal and fire properties of medium-density fiberboard (MDF) via thermogravimetric analysis (TGA), limiting oxygen index (LOI), and thermal conductivity testing. Mineral-based chemicals containing huntite /hydromagnesite and zinc borate (ZB) were used at different concentrations. Changes in all values were observed depending on the type and concentration of chemicals. According to TGA evaluation, the residual weights in the MDF samples manufactured with mineral-based chemicals were higher than the residual weight in the control MDF sample. Limiting oxygen index testing results showed higher values for the MDF samples manufactured with mineral-based chemicals than for the control sample. The LOI values increased with the increment of chemical concentration, and the highest value was observed in group B12. The thermal conductivity trends of the MDF samples varied depending on the type and concentration of chemicals. Generally, the thermal conductivity values of the MDF samples manufactured with chemicals were found to be higher than the value of the control. These results suggested that these chemicals with various combinations should be evaluated as fire retardants for wood and wood-based panel industry.

Vinyl-functionalized polysiloxane as radical scavenger during the degradation of poly(vinyl chloride)

Siloxane polymer containing vinyl groups was blended with poly(vinyl chloride) (PVC) to convey plasticization and stability against decomposition, that is likely to happen during thermal processing or following exposure to the ultraviolet (UV) light. The immiscibility between silicone rubber and PVC was proved from images acquired using scanning electron microscopy (SEM), which revealed worsening of the situation at higher loading (10 wt%) of silicone polymer. The thermal degradation profiles indicated that the inclusion of silicone polymer did not affect the thermal resistance significantly between 200°C and 350°C. However, it protected the matter from intensive decomposition at higher temperatures and increased the residual weight. Fourier transform infrared spectra were collected for the blends after exposure to UV radiation for 168 h, from which the absence of appreciable dehydrochlorination or change in the nature of the material was ensured. The hampering of dehydrochlorination is expected to have proceeded by instant attack of any appearing radicals on PVC backbone onto vinyl groups of the silicone polymer and buildup of a network structure.

Effect of curing degree on mechanical and thermal properties of 2.5D quartz fiber reinforced boron phenolic composites

Abstract2.5D quartz fiber reinforced boron phenolic composites with different curing degrees were prepared by different curing temperatures and curing times. The effects of curing degree on the flexural strength and thermal properties of the composites were investigated by mechanical properties test, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The results show that the flexural strength increases to the increase in the degree of cure, but the rate of increase is non-linear. When the degree of cure is higher than 90%, the flexural strength of the composite is more than 300 MPa and the bending failure mechanism of the composite is analyzed by SEM. The TG test showed that the degree of cure had little effect on the residual weight of the composite at 1000°C, but had a greater effect on the temperature of the previous weight loss.