Char Yield Values Research Articles

Thermal Degradation of Hemp Treated with Guanidine Carbonate

Hemp was treated with guanidine carbonate to impart flame retardance. The thermal degradation of the samples were studied by thermogravimetry (TG) and differential thermal analysis (DTA). The flame retardance was determined by LOI. Morphology of the char structure was studied by SEM to obtain information concerning the thermal degradation mechanism. For hemp treated with guanidine carbonate, which has higher LOI and char yield values, the oxidative decomposition stages include a decomposition stage at lower temperatures (172-210°C) , leading to more carbonaceous residue and small amount of flammable products to get the good flame retardance. The SEM of the chars of hemp treated with guanidine carbonate also indicate the structure of the charring layer may increase heat insulation, and protect inner matrix materials.

Nonisocyanate polyurethane/silica hybrid coatings via a sol–gel route

AbstractPolyurethane/silica hybrids by a nonisocyanate route were prepared by reacting cyclic carbonate‐modified bis(4‐glycidyloxy phenyl)phenyl phosphine oxide (BGPPO), and poly(propyleneglycol)diglycidyl ether (PPG‐DGE) with hexamethylene diamine. The incorporation of silica was achieved via a sol–gel method. The effect of silica and phosphine oxide moiety on polyurethane coating properties was studied by physical, mechanical, and thermal tests. Modulus and hardness of the coatings were enhanced by increasing the amount of silica and phosphine oxide based resin. The improvement in flame retardancy and thermal stability of nanocomposites was proved with increased char yield values and decomposition temperatures in thermogravimetric analyses. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 31: 390–400, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20262

Synthesis of New Benzoxazine from Cardanol-Furfural Resin and the Properties of the Corresponding Polymer

A novel benzoxazine-based phenolic resin containing furan groups and long alkyl side-chain (CFB) was synthesized using cardanol-furfural resin as phenolic raw materials. The new benzoxazine-based cardanol-furfural resin derived from renewable resources was characterized by FTIR,1H NMR spectra and Differential scanning calorimeter (DSC) etc. The thermal ring-opening reaction of the benzoxazine ring and the polymerization of the double bond were demonstrated with FTIR measurement. The thermal behavior of the cured product was also investigated with thermogravimetric analysis. The corresponding polybenzoxazine showed Tgvalue higher than that of polybenzoxazine prepared from cardanol, ammonia and formaldehyde. The char yield value at 800°C of the corresponding polybenzoxazine is 46.2% in N2atmosphere. The results showed that the polybenzoxazine cured from CFB had good heat resistance and toughness.

Synthesis and characterization of poly(dimethylsiloxane‐urethane) nanocomposites: Effect of (in)completely condensed silsesquioxanes on thermal, morphological, and mechanical properties

AbstractThe structural properties of completely condensed and incompletely condensed silsesquioxane in the polyurethane nanocomposites containing 17.5 wt % of silsesquioxane was investigated by FTIR, TGA, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and DMA techniques. FTIR spectra shows the existence of hydrogen bonding in the PU‐POSS system. The intensity of hydrogen bonding decreases with the increase in POSS‐H loading suggesting the prevention of the formation of hydrogen bonding by the addition of POSS‐H molecule. SEM analysis reveals the incompatibility of POSS‐H molecule in the PU matrices exhibiting greater extent of phase separation and a large number of POSS aggregates on the addition of POSS‐H molecule in the PU‐POSS matrices. The TGA thermograms show that the POSS‐PU hybrids possess excellent thermal stabilities. However, the incorporation of POSS‐H molecule leads to a decrease in the thermal properties and only the char yield values increase with the increase in the POSS‐H content in the PU‐POSS hybrids. The XRD pattern reveals that the crystalline structure of POSS molecules are destroyed by the polymer matrices in the PU‐POSS hybrid films. The decrease in the bending storage modulus E′ values with the increase in the POSS‐H content proves the retardation of hydrogen bonding formation by the POSS‐H molecule in the PU‐POSS hybrid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Fixed-Bed Pyrolysis of Hazelnut (Corylus Avellana L.) Bagasse: Influence of Pyrolysis Parameters on Product Yields

Fixed-bed slow pyrolysis experiments have been conducted on a sample of hazelnut bagasse to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields. The temperature of pyrolysis, heating rate, particle size and sweep gas flow rate were varied in the ranges 350–550° C, 10 and 50° C/min, 0.224–1.800 mm and 50–200 cm3/min, respectively. Under the various pyrolysis conditions applied in the experimental studies, the obtained char, liquid, and gas yield values ranged between 26 and 35 wt%, 23 and 34.40 wt%, and 25 and 32 wt%, respectively. The maximum biooil yield of 34.40% was obtained at the final pyrolysis temperature of 500°C, with a heating rate of 10° C/min, particle size range of 0.425–0.600 mm and a sweep gas flow rate of 150 cm3/min.

Thermal and viscoelastic properties of sequentially polymerized networks composed of benzoxazine, epoxy, and phenalkamine curing agents

AbstractBy using different ratios of phenalkamine/epoxy (EP) and benzoxazine/epoxy (EB), copolymer networks have been prepared sequentially by partially curing at low temperature followed by a final cure at high temperature. A single exothermic peak was observed in the differential scanning calorimetry (DSC) for the high‐temperature curing. Dynamic mechanical thermal analysis showed a single tan δ peak, indicating no phase separation. The copolymer networks showed Tg values lower than the parent EB polymer network. Incorporation of EP in small percentage in the copolymer networks has improved the storage modulus and crosslink densities and the maximum value was observed for a sample containing 80% EB with respect to EP content. The thermal stability of the copolymer networks is better than that of the individual networks. The char yield value at 600°C increased with increasing EB percentage in the networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3956–3965, 2006

Pyrolysis of waste tires with partial oxidation in a fluidized-bed reactor

The effects of feed rate of waste tires (0.21*0.52 kg/h), oxygen concentration (0–11%), pyrolysis temperature (700–800°C), and fluidizing gas velocity (1.5−3.0 μ mf) on product (gas, oil, char) yield, composition, energy recovery, and heating value of the product gas have been determined in a fluidized-bed reactor (0.076 m i.d. × 1.2 m-high). The product yield, composition and heating value of the product-gas, and energy recovery are found to be independent of the feed rate of waste tires. The effects of oxygen concentration (0–6.5%) on the yield and production rate of product gas (H 2, CH 4) are small but both decrease with oxygen concentrations above 6.5%. With increasing pyrolysis temperature, the gas yield and energy recovery increase, oil yield decreases, whereas the char yield remains constant. With increasing fluidizing gas velocity ( u o), the heating value of the product gas increases linearly, the total gas-production rate decreases, but energy recovery remains almost constant.