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Abstract  

The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350‡C and the other at 450‡C (onset 467‡C). The DIG curves of the blend containing 70% CNSL exhibit decomposition at 240‡C. The DSC curves show that the samples containing a high percentage of EVA reject are incompatible, withT g values around −30‡C.

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New rocket insulator compositions have been studied by adding various types and amounts of fillers, such as graphite and asbestos fibres, Al2O3, MgZrO2, Cr2O3, SiC, carbon powders and phenolic resin to the base EPDM gum and graphite, kevlar,E type glass fibres to the base phenolic resin in order to improve thermal and ablative efficiency. The degradation of the insulators has been investigated by thermogravimetry (TG) analysis to 900°C and DSC analysis to 500°C. Conversion curves of the insulators at different heating rates were performed and maximum degradation temperatures were found as 646 and 661°C for EPDM P and phenolic resin, respectively. The kinetic parameters for degradation have been evaluated and the lifetime of the rocket insulators has been estimated. Thermal analysis has been conducted on the insulators and the indepth temperature distribution was evaluated in order to find optimum insulation thickness.

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Thermochemical characterization of phenolic resins

Thermogravimetric and pyrolysis-GC studies

Journal of Thermal Analysis and Calorimetry
Authors: M. Rao, S. Alwan, K. Scariah, and K. Sastri

Abstract  

Phenol-formaldehyde resins (I andII), synthesised at a monomer feed ratio of F/P = 1.0 and 1.5, were cured at 130‡C for 48 h without any catalyst (Ia, IIa), with 0.1% ferric acetyl acetonate (Ib, IIb) and with 0.1 %p-toluenesulphonic acid (Ic, IIc). Thermogravimetric studies indicate that the decomposition of the cured products takes place in two distinct stages: The first stage (T=340–480‡C; α=0.045–0.16; δE 1 = 140±10-239±24 and 60±3–65±2 kJ mol−1 for seriesI andII respectively) was attributed to the predominant cleavage of formal linkages. The main stage decomposition (T=460–640‡C; α=0.114–0.393; δE 2=115±8–169±8 and 91±6–103±7 kJ mol−1 for seriesI andII respectively) was attributed to reactions leading to graphitisation. δE 2 values were correlated to the extent of cure as measured by IR spectroscopy and pyrolysis-GC. The effect of catalysts on the extent of cure and on the activation energy was evaluated.

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The formation and thermal behaviour of pyropolymers based on novolak resin synthesized under carefully controlled processing conditions have been studied by various thermoanalytical techniques. A suitable reaction scheme has been proposed for the formation of these pyropolymers. Only a small (3–8%) weight loss has been observed up to 800 °C in static air. DTA curves confirmed multistage exothermic processes predominantly due to two different linkages which control their thermo/thermo-oxidative stability. Hot metal filtration (≈700 °C) in an inert atmosphere exhibited only negligible weight loss.

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Abstract  

The curing kinetics of lignin-novolac and methylolated lignin-novolac resins were studied using non-isothermal methods employing differential scanning calorimetry (DSC) at different heating rates. The Belichmeier, Ozawa and Kissinger methods were applied, which give the kinetic parameters of the curing process studied. In addition, the model-fitting Coats-Redfern method was used to analyze the experimental data. The kinetic study evaluated the effect of the lignin (softwood ammonium lignosulfonate), methylolated or not, on the resin curing process. Results for lignin-novolac and modified lignin-novolac resins were compared with a commercial novolac resin as a reference. When lignosulfonate is modified by methylolation and is incorporated in the novolac resin, there is an important reduction in activation energy. The lignin-novolac showed slightly higher values of activation energy than methylolated-lignin resins, but lower values than commercial resins. This behavior has been attributed to the extra methyol groups introduced by lignosulfonate.

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Abstract  

Kinetics of thermosetting polymers curing is difficult to study by isothermal methods based on the differential scanning calorimetry (DSC) technique. The difficulty is due to the low sensitivity of the equipment for total reaction heat measurements during high temperature process. The aim of this paper is to display the equivalence between a dynamic model, the Ozawa method, and an isothermal isoconversional fit, which allows predicting the isothermal behavior of the resol resins cure through dynamic runs by DSC. In this work, lignin–phenol–formaldehyde and commercial phenol–formaldehyde resol resins were employed. In addition, the isothermal kinetic parameters for both resins were performed by means of transformation of the data obtained from the dynamic Ozawa method.

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made using a phenolic resin impregnated into chopped 1.27-by-1.27 cm glass fabric. MXB-71 experiments A TA Instruments Model Q5000 TGA was used to obtain changes in mass as the temperature of a 4.9 mg sample was increased at

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The decomposition reactions of polystyrene, phenolic resin and a protective undercoating material for automobiles which contains PVC were tested using a new type of thermal analysis — mass spectrometry coupling system for measurements to 1500‡C or 2000‡C, which is based on the principle of a two-step skimmer orifice system. The results will be presented, with particular emphasis on the detection sensitivity of the new system for the products of decomposition.

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Abstract  

The gun system of the M1 series tank rides on a pair of self-aligning spherical bearings that allows the elevation and depression of the cannon. Because these bearings are encapsulated within the rotor housing, periodic lubrication or maintenance is impossible. To overcome this problem self-lubricating bearings were incorporated into the system. There are two basic liner designs, molded and fabric. Molded liners are produced by applying a formulation of teflon and typically asbestos into a phenolic resin, which is applied to the bearing surface, then cured. Fabric liners utilize a woven fabric bonded to the bearing surface, then teflon which is mixed into phenolic resin is applied to the bearing surface and cured. Initial studies of the existing bearing liner were completed to determine the liner composition and establish a baseline or standard to compare thermal and mechanical properties with potential vendors. DSC revealed an average teflon content of 39.53%, which varied significantly throughout the liner. TG analysis showed an asbestos concentration of 12.22%. The remainder of the liner was phenolic resin. Physical testing of the bearing from −20 to 120‡C under normal loading conditions demonstrated excellent thermal stability with little wear. Bearings from each vendor were tested and compared to the standard properties of the baseline bearing. Some properties were difficult to compare or insignificant due to the design differences between molded and fabric liners. The testing program resulted in the qualification of two bearings, which met or exceeded the established standards. Both of these bearings were designed with fabric liners.

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