Thermal Stability Of Resins Research Articles

Reinforcement of mica on phthalonitrile resin and composites: Curing, thermal, mechanical and dielectric properties

High performance composites not only pursue high strength, light weight, but also need to have multifunctional characteristics. To further improve curing efficiency and mechanical properties of phthalonitrile resin (PN75) and give full play to its excellent thermal and dielectric properties, mica as reinforcement was introduced into PN75 to form particle-filled resin (Mica/PN75) and CFRP (Mica/PN75/CF) composites. The introduction of mica reduced the curing temperature of PN75 and improved the curing efficiency. The thermal stability of resin and composites was further improved. The bending strength of the two groups of mica reinforced resin increased by 44.87% and 55.97%, and the dielectric constant decreased from 3.3 to 2.7 and 2.5, respectively. The bending strength of the composites was increased by up to 19.9%, and the glass transition temperature of composites was increased by up to 26 °C after reinforcement. The multidirectional reinforcement of PN75 by mica was studied and analyzed in this work.

Study of the Thermal Stability of Heavy Oil Resins and Asphaltenes by Thermogravimetry

The thermal stability of resins and asphaltenes of naphthenic and methane heavy oils was studied by thermogravimetry. Based on the data of physicochemical methods of analysis, it was shown that the resins and asphaltenes of the test oils had significant differences in molecular weight, elemental composition, and distribution of carbon atoms in structural fragments. Thermogravimetric analysis was performed by heating the samples from 25 to 650°С at a rate of 10 K/min in an atmosphere of argon. It was shown that the maximum rate of weight loss of naphthenic oil resins and asphaltenes occurred at lower temperatures, as compared to similar components of methane oil. The thermal stability of resins and asphaltenes depended on the composition and structural organization of these components due to their formation from oil dispersed systems of various chemical types. It was established that the thermal stability of resins and asphaltenes of methane oil was higher than the thermal stability of similar components of naphthenic oil.

Effect of Chelating Agents on Removal of Heavy Metal Cations of Cellulose-based Ion Exchange Resins from Water Hyacinth

Presently, heavy metal pollution in natural water resources is considered very hazardous. The purpose of this research is to develop the novel cellulose-based ion exchange resins from water hyacinth and the effect of chelating agents on the removal of heavy metal cations from single-metal aqueous solutions has been investigated. Cellulose was prepared from the stem of water hyacinth by alkaline treatment process then cellulose-based ion exchange resins were prepared via esterification reaction between cellulose with two different chelating agents such as pyromellitic dianhydride and 3,3’,4,4’- benzophenone tetracarboxylic dianhydride. The chemical structure, crystallinity index, surface morphology, and thermal stability of resins were characterized and analyzed with FTIR, XRD, SEM, and TGA, respectively. The results confirmed the esterification reaction between anhydride groups of chelating agents with hydroxyl groups of celluloses due to the apparent peak of the ester group. Heavy metal cations adsorptions were studied in optimum conditions and the residual concentration of heavy metal cations was measured by ICP. These resins showed high adsorption capacities of more than 98 mg/g for Pb2+, Cd2+, Cu2+, and Ni2+. Moreover, the adsorption process was controlled by the ion exchange mechanism. Therefore, the novel cellulose-based ion exchange resins could be suitable for the removal of pollutants from wastewater.

Free formaldehyde reduction in urea-formaldehyde resin adhesive: Modifier addition effect and physicochemical property characterization

Melamine, polyvinyl alcohol, and adipic acid dihydrazide as modifiers were added to urea-formaldehyde (UF) resin for reducing the free formaldehyde. The influence of addition amount and addition stage of modifiers on the physicochemical property and free formaldehyde content of UF resin was tested. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA) were used to determine the structural change and thermal stability of the resins. The results revealed that the UF resin added with 6% melamine had the lowest free formaldehyde content of 0.31%. Among all modified resins added with equal amount of modifier in different stages, the UF resin added with 3% polyvinyl alcohol in the second alkaline stage achieved the lowest free formaldehyde content of 0.33%. More importantly, the comprehensive effect of melamine, polyvinyl alcohol, and adipic acid dihydrazide on the free formaldehyde content of resin was studied. The free formaldehyde content in the UF resin added with the comprehensive modifiers achieved 0.24% content, and formaldehyde emission of this kind of adhesive was just 0.21 mg/g. Coupling the experimental results with the characterization data, comprehensive modifiers can reduce the formation of chemical bonds (methylene and ether bonds) in the resin and improve thermal stability of UF resin effectively.

Role of higher aromatic content in modulating properties of cardanol based benzoxazines

Abstract Mono-benzoxazine monomers based polybenzoxazines suffer from a lower crosslink density and char yield that especially is further diluted by the presence of longer alkylene chain in cardanol (C). In order to improve the crosslink density, char yield and to understand the role of higher aromatic content vs functionality, a series of cardanol-based benzoxazine monomers were synthesised. The amine condensed with cardanol and paraformaldehyde were aniline (a), 4-triphenylmethylaniline (ta), and tetra-aminophenyl methane (tapm) via solventless methodology. The C-a and C-ta are mono-benzoxazines while C-tapm is a tetra-benzoxazine monomer. The monomers were structurally characterised using FT-IR, 1 H and 13 C NMR spectroscopy and mass spectrometry. The ring opening polymerisation temperature (ROP) of monomers and thermal stability of resins was determined using DSC and TGA while mechanical properties were determined using rheometry. The curing kinetic study using FT-IR and DSC showed C-ta has intermediate curing behaviour between the C-a and C-tapm. The E a for curing reaction C-a, C-ta and C-tapm was found to be 143, 126 and 70 kJ/mol. The lowest E a for curing reaction of C-tapm (tetra-benzoxazine) is due to its highest functionality but C-ta (mono-benzoxazine) has lower E a than C-a which can be accounted to the presence of more reactive sites provided by the additional aromatic rings in the former. It was found that the incorporation of higher aromatic ring in benzoxazine monomers is another route in enhancing the crosslink density besides higher functionality to modulate their properties.

Effects of o-Methoxy Groups on the Properties and Thermal Stability of Renewable High-Temperature Cyanate Ester Resins

Renewable phenols derived from biomass sources often contain methoxy groups that alter the properties of derivative polymers. To evaluate the impact of o-methoxy groups on the performance characteristics of cyanate ester resins, three bisphenols derived from the renewable phenol creosol were deoxygenated by conversion to ditriflates followed by palladium-catalyzed elimination and hydrolysis of the methoxy groups. The deoxygenated bisphenols were then converted to the following cyanate ester resins: bis(4-cyanato-2-methylphenyl)methane (16), 4,4′-(ethane-1,1′-diyl)bis(1-cyanato-3-methylbenzene) (17), and 4,4′-(propane-1,1′-diyl)bis(1-cyanato-3-methylbenzene) (18). The physical properties, cure chemistry, and thermal stability of these resins were evaluated and compared to those of cyanate esters derived from the oxygenated bisphenols. 16 and 18 had melting points 37 and >95 °C lower, respectively, than the oxygenated versions, while 17 had a melting point 14 °C higher. The Tg’s of thermosets generated from the deoxygenated resins ranged from 267 to 283 °C, up to 30 °C higher than the oxygenated resins, while the onset of thermal degradation was 50–80 °C higher. The deoxygenated resins also exhibited water uptakes up to 43% lower and wet Tgs up to 37 °C higher than the oxygenated resins. TGA-FTIR of thermoset networks derived from 16–18 revealed a different decomposition mechanism compared to the oxygenated resins. Instead of a low-temperature pathway that resulted in the evolution of phenolic compounds, 16–18 had significantly higher char yields and decomposed via evolution of small molecules including isocyanic acid, CH4, CO2, and NH3.

In situ processing of epoxy composites reinforced with graphene nanoplatelets

Abstract Several conventional techniques for nanofiller dispersion (high shear mixing, calendering, or a combination of the two) based on applying shear mechanical forces were studied in order to analyze their efficiency in manufacturing epoxy resin reinforced with graphene nanoplatelets (GNPs). Both provide composites with uniform GNP distributions although the calendering process also induces partial exfoliation of graphene. High-shear mixing could induce the reduction of flakes’ lateral size due to breakage and the rolling of nanoplatelets. Several physical properties of manufactured composites were measured. The density and glass transition temperature increase for composites manufactured by the calendering method due to the steric hindrance of exfoliated graphene nanosheets. Finally, the thermal stability of resin is increased by the addition of GNPs. The degradation temperature is increased up to 20 °C for composites manufactured by the calendering method.

The combined effect of epoxy nanocomposites and phosphorus flame retardant additives on thermal and fire reaction properties of fiber-reinforced composites

This study investigates the thermal stability of an aerospace grade epoxy resin containing a silicate-based nanoclay modified by an organophosphorus moiety (vinyl triphenyl phosphonium bromide; VTP), double-walled carbon nanotubes (DWCNTs) and/or conventional phosphorus containing flame retardants (FRs) at weight fractions up to 20% using thermogravimetric analysis (TGA). When FR additives (15 wt%) or VTP containing nanoclay (5 wt%) are used independently, the overall thermal stability enhancement of the epoxy resin follows the order; ammonium polyphosphate (APP) > nanoclay VTP > resorcinol bis-(diphenyl phosphate) (RDP) > tris-(tribromoneopentyl) phosphate (TBP). The addition of DWCNTs alone did not significantly alter the thermal stability of the epoxy resin matrix. The concomitant addition of VTP together with RDP, APP, and TBP at a cumulative weight fraction of 20% led to synergistic improvements in the thermal stability of the resin. The fire reaction properties of the glass fiber-reinforced laminates prepared from modified resin formulations were measured under cone calorimetry conditions at an incident heat flux of 50 kW/m2. The addition of conventional FRs with or without the nanoclay significantly reduced the peak value heat release rate and total heat release relative to the control sample. DWCNTs alone did not show a significant effect on the fire reaction properties of the epoxy resin composites. The burning behavior of the flame-retarded samples as evaluated by cone calorimetry correlated very well with TGA and differential thermal analysis (DTA) data. The depolymerization intensity as measured from DTA data agreed with PHRR from cone calorimetry while the TTI showed a direct correlation to the onset of thermal degradation as determined from TGA data. According to a fire risk assessment based on cone calorimetry data, nanocomposites containing APP achieved the highest fire safety rating.

Preparation and application of polybenzoxazine adsorption resin

AbstractThe synthesis and application of polybenzoxazine adsorption resin was studied. First, the precursor was synthesized by the solventless method. And then a kind of spherical and granular polybenzoxazine resin was obtained using reverse‐phase suspension polymerization technique in the process of solidification. Besides, the influence of dispersion medium, the volume ratio of precursor to medium, the solidification temperature, and the agitation speed were studied in detail in the process of polymerization. Second, the spherical shape of the polybenzoxazine resin was identified by scanning electronic microscope and the thermal stability of resin was measured by thermogravimetric analysis. Finally, the adsorption capacity of the spherical resin on pyridine was studied in cyclohexane systems. The correlation coefficient of Langmuir adsorption constant temperature line was bigger than 0.99, which indicated that the equilibrium sorption date was coincident with the Langmuir isotherm equation. And the saturated adsorptive capacity of dried resin achieved 222.2 mg g−1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Heat‐resistant resins obtained from polymer precursors bearing β,β′‐dicyanovinyl terminal groups

AbstractCertain polymer precursors of the general formula: magnified image where A is an aromatic structure bearing ester, amide, azomethine, or imide linkages were synthesized. Particularly, 4‐hydroxybenzaldehyde was condensed with malonitrile to afford 4‐hydroxy‐β,β′‐dicyanostyrene which reacted with a half molar amount of terephthaloyl dichloride in the presence of an acid acceptor. In addition, 3‐nitrobenzaldehyde was condensed with malonitrile to yield 3‐nitro‐β,β′‐dicyanostyrene that was catalytically hydrogenated to the corresponding amine. The latter reacted with a half molar amount of terephthaloyl dichloride, terephthaldehyde, pyromellitic dianhydride, or benzophenone tetracarboxylic dianhydride. The polymer precursors were characterized by elemental analyses as well as IR and 1H‐NMR spectroscopy. Their curing behavior was investigated by DTA. Crosslinked polymers were obtained by curing the monomers at 300°C for 24 h. They were stable up to 407–437°C in N2 and afforded an anaerobic char yield of 65–50% at 800°C. The thermal stability of resins was correlated with their chemical structures. © 1993 John Wiley & Sons, Inc.

Curing of bismaleimides—I. Effect of amines on the curing behaviour and thermal stability

This paper describes the curing behaviour of 4,4′-(bismaleimido)diphenyl ether (BE) in the presence of diamines containing amide groups in the back-bone. The effects of the concentration of diamine on the melting point ( T m), exothermic peak position ( T exo) and heat of polymerization were studied by differential scanning calorimetry. Increase in the concentration of amines in bismaleimide-amine adducts reduced T m and T exo. Thermal stabilities of resins, cured at 200° C for 30 min were evaluated by dynamic thermogravimetry in nitrogen. Char yields and the decomposition temperatures of BE increased in the presence of diamines.

Effect of substituents in the styrene aromatic ring on water absorption and thermal stability of an unsaturated polyester resin

The water absorption at 50°C and dynamic and isothermal thermogravimetric properties were studied for a series of resins made from the same maleic/phthalic anhydride-based unsaturated polyester cross-linked with each of styrene, 4-methyl styrene, 4-ethyl styrene, 4-n-butyl styrene, 4-isopropyl styrene, tertiary butyl styrene, 4-chlorostyrene and 3,4-dichlorostyrene. Chloro substituents and most alkyl groups give rise to a loss of water resistence. However, the tertiary butyl group leads to a decrease in both water absorption and water damage. The thermal stability of the resin is decreased by chloro substituents and increased by n-alkyl groups, and the results suggest that the main degradation step involves styrene residues, but that the initial decomposition does not do so.

Thioetherglycidyl resins. I. Products of condensation of 1‐mercaptomethylnaphthalene and 1,4‐, 1,5‐di‐(mercaptomethyl) naphthalene and their mixtures with epichlorohydrin

AbstractNew thioetherglycidyl resins produced by condensation of 1‐mercaptomethylnaphthalene, 1,4‐di(mercaptomethyl)naphthalene, 1,5‐di(mercaptomethyl)naphthalene, and their mixture of 1,4‐ and 1,5‐di(mercaptomethyl)naphthalene with epichlorohydrin were obtained. The condensation was carried out in two ways. In the first way, potassium salt of mercaptans and epichlorohydrin were used. In the second, epichlorohydrin was added to mercaptans and then the obtained chlorohydrin thioether was dehydrohalogenated by the alkaline hydroxide in water and n‐butanol or isopropyl alcohol solution. The method of heterogeneous condensation of dithiol with epichlorohydrin in water and isopropyl alcohol solution proved to be the most effective. Yield, the epoxide content, and the total chlorine content for all resins were found. The structure of thioetherglycidyl resins with the highest epoxide content was determined by elementary analysis, and infrared (IR) and NMR spectra. Thermal stability of resins was studied during long controlled heating at unchanged temperature and short heating carrying the thermal gravimetric analysis (TGA) mainly in air. As follows from the studies, thioetherglycidyl resins can be cured both chemically and thermally.

Studies of Nitrogen—Phosphorus Compounds. XXIX. Synthesis and Thermal Stability of Phosphorus Diamide Nitride Resins

The synthesis of resins by the reaction of trimeric or tetrameric phosphorus diamide nitride (NnPn(NH2)2n, n=3, 4) with formalin (CH2O), and the possibility of the formation of co-condensation resins through the addition of urea (CO(NH2)2) or melamine (C3H6N6) in the above reaction system have been investigated. Moreover, the thermal stability of resins has been studied by the DTA and TGA methods. In the NnPn(NH2)2n—CH2O system (n=3, 4), the rate of gelation increased with a decrease in pH, and remarkably accelerated with an increase in temperature. A mixture of these components in a suitable molar ratio was neutral and gelatinized gradually at 50°C within a period of 1—4 h. The gelatinous product was converted into a transparent resin at 80°C. The proper quantities of formalin were 7.5—9 and 16—20 mol to 1 mol of N3P3(NH2)6 and N4P4(NH2)8, respectively. The rate of gelation for the tetramer was distinctly greater than that of the trimer variety. In the N3P3(NH2)6—CO(NH2)2—CH2O and N3P3(NH2)6—C3H6N6—CH2O systems, the transparent resins were obtained in molar ratios of 1:2.5—10 and 1:1—20 of urea and melamine to the trimer variety, respectively. The resin of NnPn(NH2)2nCH2O system was found to be P 23—26%, and N 29—33%. The resin formed by the addition of urea or melamine naturally decreased the P content, while the N content did not vary appreciably. The thermal decomposition of resins reacted with NnPn(NH2)2n shifted more to the lower temperature side than did the urea—formalin and melamine—formalin resins. However, their carbonized residues formed remarkably, checked the spread of fire, and were incinerated at about 80°C.

Thermal Stability of Resins - Infrared Spectroscopic Study of Isomeric Phthalic Alkyds and Silicone

Thermal Stability of Resins - <i>Infrared Spectroscopic Study of Isomeric Phthalic Alkyds and Silicone</i>