Co-microencapsulate of ammonium polyphosphate and pentaerythritol in intumescent flame-retardant coatings

Co-microencapsulated ammonium polyphosphate (APP) and pentaerythritol (PER) [M (A&P)] is prepared using melamine–formaldehyde resin by in situ polymerization method and characterized using energy dispersive spectrometer and Fourier transform infrared spectra. Thermal stability and fire resistance behavior have been analyzed and compared. The co-microencapsulation of APP and PER leads to a great improvement of its thermal stability investigated by thermogravimetric analysis. The temperature of maximum mass loss rate of M (A&P) is 30 °C higher than that of APP/PER mixture. The flame-retardant effect of M (A&P) in coating composite is evaluated by carbonization volume, flame spread rate, and cone calorimeter. Results show that the flame-retardant properties of M (A&P) in coating composite is much better than that of APP/PER mixture coating composite.     

Kinetics of thermal degradation and thermal oxidative degradation of poly(p-dioxanone)

The kinetics of the thermal degradation and thermal oxidative degradation of poly(p-dioxanone) (PPDO) were investigated by thermogravimetric analysis. Kissinger method, Friedman method, Flynn-Wall-Ozawa method and Coats-Redfern method have been used to determine the activation energies of PPDO degradation. The results showed that the thermal stability of PPDO in pure nitrogen is higher than that in air atmosphere. The analyses of the solid-state processes mechanism of PPDO by Coats-Redfern method and Criado et al. method showed: the thermal degradation process of PPDO goes to a mechanism involving random nucleation with one nucleus on the individual particle (F₁ mechanism); otherwise, the thermal oxidative degradation process of PPDO is corresponding to a nucleation and growth mechanism (A₂ mechanism).     

Characterization and thermal degradation of polypropylene-montmorillonite nanocomposites

Polypropylene (PP)-montmorillonite nanocomposites have been prepared using isotactic PP homopolymers with different rheological properties, and a maleic anhydride grafted PP. Morphology and structure of the composites were investigated by using X-ray techniques (WAXD, SAXS) and transmission electron microscopy (TEM). The absence of pristine clusters of the clay and the presence of intercalated and exfoliated structures were shown for all the investigated samples. The nanocomposite prepared by using maleic anhydride grafted PP showed a widespread exfoliation. The thermal behaviour and degradation have been studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The incorporation of the montmorillonite improves the thermal stability in air atmosphere of all the investigated PPs, thanks to a physical barrier effect of the silicate layers.     

Kinetics of thermal degradation and estimation of lifetime for polypropylene particles: Effects of particle size

The thermal stability and degradation behavior of polypropylene (PP) particles having diameter varying from few micrometers to nanometers were studied by thermogravimetric analysis (TGA). The PP particles of average diameter ∼20 μm, ∼10 μm, ∼5 μm, ∼1 μm and <500 nm were studied over a range of temperature from 25 to 600 °C in N₂ atmosphere and heating rates of 5, 10 and 15 °C/min. Thermal stability of PP particles initially decreases and then increases as particle size further decreases to nanometer scale. The five single heating rate techniques such as Friedman, Freeman-Carroll, Chang, Coats-Redfern and second Kissinger; and three multiple heating rate techniques such as the first Kissinger, Kim-Park and Flynn-Wall were used to compute the kinetic parameters of degradation reaction, e.g., activation energy (E_a), order of reaction (n) and frequency factor [ln(Z)]. The lifetime of macro-, micro- and nanosized PP particles was also estimated by a method proposed by Toop. It was found that the activation energy and lifetime of nanosized PP particles are moderately high compared to the microsized PP particles. Moreover, the decomposition temperature, order of reaction (n), frequency factor [ln(Z)] not only depend on the heating rate and calculation technique but also on the particle size of polymer. The results are compared with macrosized PP.     

Fabrication, morphology and thermal degradation behaviors of conductive polyaniline coated monodispersed polystyrene particles

This study describes the preparation of polyaniline (PANI) coated on the surface of monodispersed 400 nm polystyrene (PS) particles by in situ chemical oxidative polymerization. The monodispersed 400 nm PS particles served as cores were synthesized using the emulsion polymerization. Both images observed by field-emission scanning electron microscopy and transmission electron microscopy show the presence of a thin PANI layer uniformly coated on the surface of PS particle. The electrical conductivity of various amounts of PANI-coated PS particles is significantly increased about 13 orders of magnitude compared to that of the pristine PS particles. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to investigate the thermal stability and thermal degradation behavior of PS and PANI-coated PS particles. Both DSC and TGA curves revealed that the coating of a thin PANI layer on the surface of PS can drastically increase the thermal stability of PS matrix. TGA isothermal degradation data illustrate that the activation energy of the PANI-coated PS particle is larger than that of PS. This phenomenon can be attributed to the incorporation of PANI coating on the surface of PS particle caused a decrease in the degradation rate and an increase in the residual weight for the PANI-coated PS particle.     

Non-isothermal kinetics of reactions whose activation energy depends on the degree of conversion

A procedure for evaluating the non-isothermal kinetic parameters of reactions for which the activation energy depends on the degree of conversion is suggested. The procedure has been applied to the dehydration of calcium oxalate monohydrate and to the thermal degradation of poly(vinyl chloride) (PVC) and polychloroprene rubber.     

Study of kinetics of thermal degradation and to determine the activation energies of polyamides based on s-triazine

A series of ten polyamides was prepared by the high-temperature polycondensation of 4,6-bis(N-(4-(benzoylchloride)amino))-2-(N-phenyl- piperazin-1-yl)-1,3,5-triazine with different aromatic and aliphatic diamines. The synthesized polyamides were analyzed by physico-chemical properties such as solubility, density, viscosity etc. The structure of prepared polyamides was evaluated by ¹H NMR and FTIR spectrum. Thermogravimetric analysis used to study the kinetics of thermal degradation of some synthesized polyamides. Broido, Horowitz & Metzger, Coats Redfern and Chan et al. models were applied to respective thermograms to determine the activation energy (E_a). Activation energy data shows that the polyamides obtained from aromatic diamine has greater stability than the polyamides obtained from aliphatic amine.     

Thermal degradation kinetics of polystyrene/cadmium sulfide composites

The thermal degradation kinetics of polystyrene/CdS composites were studied by thermogravimetry. The samples were heated in nitrogen, with three different heating rates: 5, 20 and 40 °C min⁻¹. We calculated kinetic parameters using KAS isoconversion method. The results showed that the maximum activation energy of thermal degradation is achieved for PS/CdS composite with about 10% of the CdS filler. Higher concentration of CdS in the composite (20%) induced acceleration of the thermal degradation, approaching the rate of degradation of the pure polystyrene matrix.     

Synthesis and thermal degradation behaviors of hyperbranched polyphosphate

A novel epoxy-terminated hyperbranched polyphosphate (E-HBPP) was synthesized by employing an A₂ + B₃ polycondensation and characterized by FTIR, ¹H NMR and GPC. E-HBPP was used as a reactive-type flame retardant for diglycidyl ether of bisphenol-A/m-phenylene diamine (DGEBA/mPDA) system. A series of flame retardant resins were prepared and their flame retardancy was monitored by the limiting oxygen index (LOI). The results showed that the LOI value of the cured samples and the degree of expansion of the formed char after burning increased along with the E-HBPP content. Their thermal degradation behaviors were investigated by thermogravimetric analysis and in situ FTIR and showed that the phosphate group of E-HBPP first degraded to form poly(phosphoric acid)s at around 300 °C, which had a major contribution to form the compact char to protect the sample from further degradation. The dynamic mechanical thermal properties were studied by dynamic mechanical thermal analysis (DMTA) and the results showed a good miscibility between E-HBPP and DGEBA. The mechanical properties of the cured films were also investigated. Less than 20% E-HBPP addition improved both the tensile strength and elongation at break.     

Thermal degradation kinetics of poly(methylphenylsiloxane) containing methacryloyl groups

The kinetics of the thermal degradation of polymethylphenylsiloxane containing methacryloyl groups (PMPS-M) were investigated by thermogravimetric analysis (TGA). Thermal degradation of PMPS-M had two different processes: “unzipping degradation” and “rearrangement degradation”. The corresponding kinetic parameters of the two degradation stages were determined by using Friedman and Flynn-Wall-Ozawa methods, respectively. Coats-Redfern and Phadnis-Deshpande methods were also used to discuss the probable degradation mechanisms of the two different stages. The results showed that the activation energy obtained from Friedman method was in good agreement with the value obtained using Flynn-Wall-Ozawa method. The solid-state decomposition mechanism followed by the first degradation stage of PMPS-M was a decelerated D₄ type (three-dimensional diffusion controlled reaction). However, as for the second degradation stage of PMPS-M, its solid-state decomposition mechanism corresponded to a sigmoidal A₃ type, a nucleation and growth mechanism.     

Effect of zinc borate on the thermal degradation of ammonium polyphosphate

The thermal behaviour of a mixture containing an ammonium polyphosphate based compound (AP760) and zinc borate (ZB) is investigated. After an investigation of the degradation of the pure components, the interactions between them are examined by thermogravimetry. Then, X-ray diffraction (XRD) and ¹¹B and ³¹P solid-state nuclear magnetic resonance (NMR) measurements have been carried out on residues of mixtures of AP760 and FBZB heat treated at different characteristic temperatures. It reveals the nature of the interactions taking place between the two components. It is demonstrated that reactions lead to the formation of zinc phosphate and of borophosphates. Mechanisms of thermal degradation are proposed.     

Influence of hydrogenated oligo(cyclopentadiene) on the structure and the thermal degradation of polypropylene-based nanocomposites

Polypropylene has been compounded with a commercial organoclay both in the absence and in the presence of hydrogenated oligo(cyclopentadiene) (HOCP) as a compatibiliser. The characteristics and the properties of the nanocomposites were evaluated and compared. HOCP favours the intercalation of the polypropylene in the organoclay galleries and enables a more homogeneous dispersion of the nanoclay throughout the polymer matrix. In the compatibilised nanocomposite, the diluent effect ascribed to the HOCP component is associated with the nucleating action of the nanoclay, resulting in the development of the β-crystalline form of the polypropylene. The presence of HOCP preserves the molecular weight of the polymer during the processing and gives good overall mechanical properties to the compatibilised nanocomposite. The thermo-oxidative degradation of the polypropylene is strongly delayed in the compatibilised nanocomposite.     

Simulation of the thermal degradation and curing kinetics of fly ash reinforced diglycidyl ether bisphenol A composite

Thermogravimetric Analysis (TGA) is concluding expanding applicability in determination of the thermal stability and degradation nature of materials. The present study investigates the thermal degradation behavior and the kinetics of degradation of epoxy mixed with varying percentages of 0, 2.5, 5, and 7.5 ​wt% fly ash. Thermal stability and degradation behavior of fly ash modified epoxy cast were determined by thermogravimetric analysis. The kinetic parameters of the EF composites were calculated by using Coats–Redfern, Broido and Horowitz–Metzger models under best-fit analysis and further proved by linear regression analysis. The kinetics of thermal degradation was calculated from data scanned at a heating rate of 10 ​°C/min. The obtained results reveal that kinetic parameters and thermal behavior of EF composites were improved with the reinforcement of fly ash. The cure kinetics of the varying content of fly ash reinforced epoxy cast were also studied by using a nonisothermal differential scanning calorimetric (DSC) technique at four different heating rates 5 ​°C/min, 10 ​°C/min, 15 ​°C/min and 20 ​°C/min. The curing kinetics of the EF composite was derived from the nonisothermal differential scanning calorimetry (DSC) data with the three Kissinger, Ozawa, and Flynn–Wall–Ozawa models, respectively.     

Mechanism and kinetics of the isothermal thermodegradation of ethylene-propylene-diene (EPDM) elastomers

The thermal degradation behavior of a range of ethylene-propylene-diene (EPDM) elastomers, covering the whole range of composition, has been examined under isothermal conditions between 410 and 440 °C using thermogravimetric analysis. The kinetic parameters of degradation for the polymers have been evaluated using different mathematical models based on different proposed mechanisms of degradation. The experimental data were fitted to the models using non-linear regression analysis technique based on Marquardt-Levenberg algorithm. It appears that the degradation of EPDMs follows the Avrami-Erofeev two-dimensional nucleation model or a random chain-scission mechanism. No observable trend was found between the ethylene content of EPDM and the activation energy of degradation.     

The thermal degradation kinetics of dextran and pullulan

The effect of molar mass and, in the case of dextran, of the degree of branching on the thermal degradation kinetics of dextran and pullulan was studied in the presence and absence of oxygen. Although the initial mass loss of the dextran samples occurred at higher temperatures than that of the pullulan samples, the overall thermal degradation activation energies were lower for dextran than for pullulan. In the case of dextran the thermal stability was found to decrease with molar mass and degree of branching. The molar mass of pullulan, in the range of 10⁴ to 10⁵ g/mol, appeared to have no significant influence on the thermal characteristics of the samples.     

Effects of synthetic and natural zeolites on morphology and thermal degradation of poly(lactic acid) composites

Poly(lactic acid) (PLA) composites containing 5 wt% synthetic (type 4A) and natural (chabazite) zeolites were prepared using extrusion/injection molding. Morphological, structural, and thermal properties of composites were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). DSC results revealed that the glass transition and melting temperatures were not significantly changed; however, the incorporation of both type 4A and chabazite zeolites enhanced the nucleation of PLA crystallites as well as increased the percent crystallinity. Thermal degradation properties of PLA and PLA/zeolite composites were studied by non-isothermal thermogravimetric analysis (TGA) in nitrogen atmosphere. TGA results showed that at temperatures above 300 °C, PLA/type 4A synthetic zeolite composites were thermally decomposed more easily than the PLA and PLA/chabazite natural zeolite composites. The apparent activation energies of thermal degradation of PLA and PLA/zeolites composites estimated using both the Flynn-Wall-Ozawa and Kissinger methods followed the same order: PLA/type 4A < PLA/chabazite < PLA.     

Flame retardancy and thermal degradation of halogen-free flame-retardant biobased polyurethane composites based on ammonium polyphosphate and aluminium hypophosphite

In this work, based on castor oil (CO), flame retardant polyurethane sealants (FRPUS) with ammonium polyphosphate (APP) and aluminum hypophosphite (AHP) were prepared. The synergistic flame retardant effects between APP and AHP on flame retardancy, thermal stability, and flame retardant mechanisms of FRPUS were investigated. It was found that when the mass ratio of APP and AHP was 5:1, the limiting oxygen index (LOI) value of FRPUS increased to 35.1%, In addition, at this ratio, the parameters from cone calorimeter testing (CCT) were reduced; these parameters include peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP). The thermal decomposition behavior of the FRPUS was investigated by thermogravimetric analysis (TGA). The results showed that AHP improved the thermal stability of the PUS/APP system and increased char residue at high temperatures. Moreover, the residual carbon was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), gas phase pyrolysis products were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and thermogravimetric analysis/mass spectrometry (TG-MS). It was observed that the flame retardant mechanisms of the APP/AHP system was the combination of gas and condensed phase flame retardant mechanisms.     

Synthesis and thermal behaviour of polyamide 6/bentonite/ammonium polyphosphate composites

In order to achieve acceptable levels of flame retardancy of polymers, phosphorus-based flame retardant (FR) additives at about 20-30% w/w are required which is too high for conventional synthetic fibres. To know whether more finely sized particles of conventional FRs with or without nanoclay are more effective at the same concentration, composites of PA6 with bentonite and ammonium polyphosphate (APP) have been prepared by melt processing in a twin-screw extruder. XRD peaks and TEM images of PA6/Org-bentonite composite show partially ordered intercalation and ordered exfoliation. Thermal analysis in He shows that thermal stability of PA6 nanocomposite has increased by 18 °C compared with pure PA6 during degradation after 425 °C but it has decreased by 100 °C on inclusion of APP in PA6/nanoclay composites. The char yield is increased by 20% in PA6/bentonite/APP composites. No effect on thermal stability or char yield is observed by reducing the particle size of APP.     

Thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends: Thermogravimetric analysis

Thermal stability of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends has been investigated by thermogravimetric analysis (TGA) in dynamic and isothermal heating regime. PVC/PEO blends were prepared by hot-melt extrusion (HME). According to TG analysis, PEO decomposes in one stage, while PVC and PVC/PEO blends in two degradation stages. In order to evaluate the effect of PEO content on the thermal stability of PVC/PEO blends, different criteria were used. It was found that thermal stability of PVC/PEO blends depends on the blend composition. The interactions of blends components with their degradation products were confirmed. By using multiple heating rate kinetics the activation energies of the PVC/PEO blends thermal degradation were calculated by isoconversional integral Flynn–Wall–Ozawa and differential Friedman method. According to dependence of activation energy on degree of conversion the complexity of degradation processes was determined.     

Thermal degradation kinetics of poly(methylvinylsilylene-co-styrene)

Thermal degradation kinetics of poly(methylvinylsilylene-co-styrene) copolymers, viz., PMVSS-I to PMVSS-V obtained by reacting methylvinyldichlorosilane (MVDCS) and styrene in 1:0.25, 1:0.5, 1:1, 1:3 and 1:7 mole ratios under dechlorination conditions, using sodium, was studied by thermogravimetry. The homopolymer, poly(methylvinylsilane) (PMVS), synthesized from MVDCS using sodium was also subjected to the above study for comparative evaluation. The kinetic parameters for thermal degradation, viz., activation energy (E) and pre-exponential factor (A) for the above polymers were estimated by non-isothermal kinetic methods such as Mac Callum-Tanner (M-T), Horowitz-Metzger (H-M), Madhusudhanan-Krishnan-Ninan (MKN) and Coats-Redfern (C-R). The order for thermal degradation of PMVS was found to be almost 0. In the case of the copolymers, the order was 1 for PMVSS-I and 2 for PMVSS-II to PMVSS-V. The observed difference in the order for thermal degradation of PMVSS-I when compared to the other copolymers is attributed to the presence of polysilyl linkages in PMVSS-I. It was found that the activation energy and pre-exponential factor showed an increase in trend with increase in concentration of styrene in the copolymer system.