Syntheses and thermal properties of ether-containing bismaleimides and their cured resins

Aromatic bismaleimides (BMIs) were prepared by the condensation of malefic anhydride with multiring diamines containing ether bridges. The thermal behavior of the bismaleimides was investigated by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) and thermomechanical analysis (TMA) were utilized to characterize the thermal properties of the cured resins. The effect of the structures of bismaleimides on their thermal behavior and the thermal properties of the cured resins is discussed. Increasing molecular weight between reactive endgroups lowered melting points of BMIs, leading to a large temperature range between their melting point and the initial polymerization temperature. The introduction of ether bonds together with other flexible partners to bismaleimide resins decreased the glass transition temperatures or softening temperatures and the brittleness of the cured bismaleimide resins without extreme loss of their thermal stability. The cured bismaleimides were stable up to 450°C in both air and nitrogen.     

Synthesis and characterization of pyridine and anthracene containing bismaleimides,bisnadimides and polyaspartimides

Three different novel diamines containing pyridine and anthracene moiety were prepared and subsequently converted into bismaleimides (BMI) and bisnadimides (BNI) and their structure was confirmed by elemental analysis, FT-IR, ¹H-NMR and ¹³C-NMR techniques. Chain extension of bismaleimides and bisnadimides was accomplished by incorporating various ether or ester groups. Owing to pendant anthracene moiety, pyridine unit and flexible linkages, the bismaleimides and bisnadimides were found to possess an excellent balance of properties; solubility and thermal stability and the curing behaviour was investigated by differential scanning calorimeter. In addition, a series of polyaspartimides containing anthracene and pyridine unit was prepared by the polyaddition of bismaleimides with various diamines via a Michael-type addition. The thermal stability of bismaleimides, bisnadimides and polyaspartimides was evaluated by thermo gravimetric analysis. All the polyaspartimides are soluble in many organic solvents and exhibit T _g in the range of 189–242 °C and 10% weight loss (T ₁₀) takes place in the range of 389–487 °C in N₂.     

Electric strength of epoxide resins and its relation to the structure

Epoxide resins having various ratios of ether and ester bonds were investigated as to the relation between electric strength and polymer characteristics. The electric strength over a wide range of temperature is presented here. A marked reduction of strength characteristics of the epoxide resins occurs at a critical temperature indistinguishable from the glass transition temperature T_g, which is related to the free volume and molecular relaxation process. At temperatures exceeding T_g, the electric strength has a strong dependence on polymer structure, film thickness, and applied pulse width. This behavior is considered to obey the thermal breakdown mechanism, and it is assumed that the ion is important in the precursory region of electric breakdown.     

Fluorinated bismaleimide resin with good processability,high toughness,and outstanding dielectric properties

In this study, novel fluorinated bismaleimide (BMI) resins were prepared by the copolymerization of 2,2′‐bis[4‐(4‐maleimidephenoxy)phenyl]hexafluoropropane (6FBMP) and diallyl hexafluorobisphenol A (6FDABPA) to enhance their dielectric properties. The dielectric properties of the resins were investigated in the frequency range 7–18 GHz through a cavity method. Through the incorporation of a hexafluoroisopropyl group with the polymer chain, the dielectric constant (ε) was effectively decreased because of the small dipole and the low polarizability of the carbon‐fluorine (C? F) bonds. The 6FBMP/6FDABPA resin possessed excellent dielectric properties, with ε being 2.88 and the dielectric loss being 0.009 at 10 GHz and 25°C. In comparison with the 4,4′‐bismaleimidodiphenylmethane (BDM)/2,2′‐diallyl bisphenol A (DABPA) resin, the glass‐transition temperature (T_g) of 6FBMP/6FDABPA decreased. The flexible ether group in the long chain of 6FBMP was considered to disrupt chain packing and cause a decreased crosslinking density and a lower T_g. 6FBMP/6FDABPA showed a similar thermal decomposition temperature and good thermal properties like the BDM/DABPA resin, whereas the impact strength of the 6FBMP/6FDABPA resin was almost 1.6 times higher than that of the BDM/DABPA resin. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42791.     

Thermal behavior of cast polyurethane elastomers

Thermal properties like glass transition temperature (T_g), initial decomposition temperature (idt), integral procedural decomposition temperature (ipdt), and temperature at various % weight loss of a number of polyurethane systems are reported in this paper. Glass transition temperature was determined on TMA, and other thermal properties were determined by thermogravimetry. The experiments were designed to understand various factors such as length of chain extender moiety, flexibility of chain extender units by substitution of ether link in the diol chain, nature of bonds (unsaturation) in the extender unit, and nature of diisocyanates.     

Chain-Extended bismaleimides. I. Preparation and characterization of maleimide-terminated resins

Starting from aromatic diamines, a series of bismaleimides (BMIs) and maleimide-terminated structural resins were prepared in solution and characterized. Maleimide-terminated resins were prepared through Michael addition reaction with 3/2 molar ratio of bismaleimide and aromatic diamine as reactants. The structural analysis was performed by FTIR and ¹H-NMR spectroscopy. Thermal properties are investigated by TGA, DTA, and DSC. Number-average molecular-weights of the resins were determined by cryoscopy. The presence of methylene ( CH₂ ) and ether ( O ) groups in the starting materials affect the reactivity and the degree of chain extension of the resins. From the viscosity measurements it was also found that thermal polymerization of BMIs could be taking place together with the Michael addition. © 1996 John Wiley & Sons, Inc.     

Copolymers of poly(arylene sulfide sulfone)/poly(ether sulfone): Synthesis,structure, and rheology properties

In order to overcome the poor flowability of poly(arylene sulfide sulfone) (PASS), we introduced ether bonds into the polymer main chain. A series poly(arylene ether sulfide sulfone) copolymers (PAESS) containing different proportion of ether bonds were synthesized with 4,4′‐dichlorodiphenyl sulfone (DCDPS), sodium sulfide (Na₂S·xH₂O), and 4,4′‐dihydroxydiphenyl ether (DHDPE). The copolymers were characterized by Fourier transform infrared (FTIR), ¹H‐nuclear magnetic resonance (NMR), differential scanning calorimetry, dynamic mechanical analysis (DMA), and rheometer. The results of FTIR and ¹H‐NMR indicate the copolymers are synthesized successfully. PAESS were found to have excellent thermal properties with glass transition temperature (T_g) of 175.7–219.1 °C and 5% weight lost temperature were all above 420 °C. The tensile and DMA test indicates that these resultant copolymers have good mechanical properties with tensile strength of 60 MPa and storage modulus of 1.5 GPa. From the results of rheology properties testing, we found that the melt stability and melt flowability of PASS were improved distinctly from 25,470 Pa s down to 355 Pa s with the incorporation of ether bonds. That will be quite beneficial to the processing of PASS, especially for the thermoforming of precision products. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46534.     

Synthesis and properties of trifluoromethyl groups containing epoxy resins cured with amine for low Dk materials

The study synthesized a trifluoromethyl (CF₃) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (T_g) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (T_d5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (D_k) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF₃ groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of bismaleimide resins of aromatic sulfone ether diamine

Aromatic sulfone ether diamine, bis[4-(4-aminophenoxy)phenyl]-sulfone (SED), was prepared by the nucleophilic aromatic substitution of 4,4′-dichlorodiphenylsulphone by p-aminophenolate. The reaction was conducted in the presence of excess potassium carbonate as a weak base, toluene as the dehydrating agent and N-methylpyrrolidone as the dipolar aprotic solvent. SED showed good solubility in common organic solvents, such as dioxan, tetrahydrofuran, butanone and acetone. SED was reacted with maleic anhydride to obtain aromatic sulfone ether bismaleimide, bis[4-(4-maleimidophenoxy)phenyl]-sulfone (SEM). The compounds were characterized by FTIR and ¹H NMR analysis. Furthermore, copolymer resins of SED with 4,4′-bismaleimidodiphenyl methane (BMI) and SEM were prepared. After curing, crosslinked resins with better thermal stability resulted. The temperature at maximum rate of weight loss (T_max) and the heat-resistant temperature index (T_i) in air were found to be 426°C, 208°C and 579°C, 221°C for BMI/SED and SEM/SED resins, respectively. Compared with the corresponding 4,4′-diaminodiphenyl methane (DDM) system, BMI/SED and SEM/SED showed a slight decrease in T_max and T_i SED-modified BMI/amine resin based glass cloth laminates for printed circuit boards showed higher mechanical properties than those of the corresponding unmodified system. With SED instead of the original amine component in 3–5% weight fraction, the tensile strength, flexural strength and impact strength of the laminates increased markedly. Meanwhile, the stripping strength and weld resistance were also improved by the addition of SED.     

Physical aging of linear and network epoxy resins

Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers have been prepared and studied. Both diamine and anhydride crosslinking agents were utilized. In addition, some rubber modified epoxies and a carbon fiber reinforced composite was investigated. All of these materials display time-dependent changes in many of their properties when they are stored (following quenching) at temperatures below their glass transition temperature (sub-T_g annealing). For example, the degree of stress relaxation for a given time period is observed to decrease in a linear fashion with the logarithm of time during sub-T_g annealing. Young's modulus and yield stress were also found to increase ire physical aging. Solvent sorption experiments initiated after different sub-T_g annealing times have demonstrated that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. The effect of water on the physical aging of these epoxy resins was not found to be a significant variable. Residual thermal stresses were also found to have little effect on the physical aging process, although this variable was not studied in detail. Finally, the physical aging process also affected the sub-T_g properties of uniaxial carbon fiber reinforced epoxy material and the effects were as expected. The importance of the recovery or physical aging phenomenon, which affects the durability of epoxy glasses, is considered in view of the widespread applications for these resins as structural materials.     

Bismaleimides,bisnadimides, and polyaspartimides containing ether and ester linkages and pyridine

A series of bismaleimides (BMI) and bisnadimides (BNI) containing pyridine ring and flexible linkages were prepared and the structural characterization of the resins was carried out by elemental analysis, FTIR, ¹H NMR, and ¹³C NMR spectroscopy. Their curing behavior were characterized by differential scanning calorimetry and thermal stability of the cured resins were investigated by thermogravimetric analysis. In addition, a series of polyaspartimides were prepared by the polyaddition of the bismalemide with various dimaines. The polymers were characterized by FT‐IR, inherent viscosity, and molecular weight measurements. All the polyimides were soluble in many organic solvents, the glass transition temperature of the polyaspartimides are in the range of 194–231°C, 10% weight loss (T₁₀) takes place in the temperature range of 379–482°C in N₂ and char yield in the range of 44.31–53.31%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of phenoxy resins prepared from diglycidyl ether of bisphenol a and various aromatic dihydroxyl monomers

This work describes the synthesis of various phenoxy resins by in situ fusion reaction of aromatic dihydroxyl and low molecular weight liquid diglycidyl ether of bisphenol A (DGEBA) with an aryl phosphonium salt catalyst. FTIR and ¹H-NMR spectra and GPC analyses were performed to characterize the resins. Analyses results indicated that resins have an adequate high molecular weight and physical properties when the reaction occurred after 5–10 min at 225–230°C. In addition, DSC and TGA analyses were performed to investigate the thermal properties of these phenoxy resins. According to these results, the lack of steric hindrance of the molecular structure in these phenoxy resins depressed the changes of T_g and weight loss. A series of phenoxy modified epoxy networks containing narrower polydisperity and higher M_n will exhibit the most significant effect on impact toughness. Moreover, the FTIR spectrum of the phenoxy resin as a function of temperature correlates well with the glass transition temperature. Furthermore, results presented herein demonstrate effective miscibility with thermoplastic polyurethane elastomer (TPU). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2369–2376, 1999     

New Bismaleimide-Epoxy Resin System

New functional epoxy resins were prepared by the reaction of dialyldiglycicylbisphenol A (DADGBPA) with diaminodiphenylmethane. DADGBPA was prepared by reaction of o,o′-diallylbisphenol A with epichlorhydrine. By reaction of functional epoxy resins with bismaleimides, new epoxy-bismaleimide resins with good thermostability were obtained. The thermal properties of epoxy resins and epoxy-bismaleimide resins were determined by DSC and TGA measurements.     

Study on poly(ether ether ketone)/organically modified montmorillonite composites

Abstract

Novel poly(ether ether ketone) (PEEK)/organically modified montmorillonite (OMMT) composites containing 0–10 wt-% fractions of OMMT were prepared by melting blending method and the microstructure, thermal and mechanical properties were investigated using different characterisation techniques. X-ray diffraction and transmission electron microscopy showed that the OMMT was well dispersed with microscale in the PEEK matrix. Differential scanning calorimetry indicated that the glass transition temperature T _g and melt temperature T _m of PEEK/OMMT composites (POMCs) were hardly affected by the addition of OMMT, while the crystal temperature T _c decreased when the amount of OMMT excessed 1 wt-%. The data of thermogravimetric analysis exhibited that the thermal stability of POMCs in higher temperature region was better than that of pure PEEK. The results of mechanical properties test revealed that modulus and strength of POMCs increased with the content of OMMT, whereas the elongation at break and impact strength of POMCs decreased.     

Thermal studies: A comparison of the thermal properties of different oligomers by thermogravimetric techniques

Thermal properties of conventional organic oligomers and organically modified ceramic hybrid materials (Ormoresin) were characterized and compared by using thermogravimetric techniques. Thermal properties were compared in terms of initial thermal decomposition temperature (T₀, which is the temperature at which 5% weight loss occurred), the temperature at which 50% weight loss occurred (T₅₀), and the percentage of residue remained at 600°C. Organically modified ceramic resins are found to have improved thermal stability. It is also found that the type of inorganic material incorporated in organically modified ceramics resin (Ormoresin) has considerable influence on its thermal characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 977–985, 2004     

Synthesis and properties of methyl hexahydrophthalic anhydride‐cured fluorinated epoxy resin 2,2‐bisphenol hexafluoropropane diglycidyl ether

The fluorinated epoxy resin, 2,2‐bisphenol hexafluoropropane diglycidyl ether (DGEBHF) was synthesized through a two‐step procedure, and the chemical structure was confirmed by ¹H n uclear magnetic resonance (NMR), ¹³C NMR, and Fourier transform infrared (FTIR) spectra. Moreover, DGEBHF was thermally cured with methyl hexahydrophthalic anhydride (MHHPA). The results clearly indicated that the cured DGEBHF/MHHPA exhibited higher glass transition temperature (T_g 147°C) and thermal decomposition temperature at 5% weight loss (T₅ 372°C) than those (T_g 131.2°C; T₅ 362°C) of diglycidyl ether of bisphenol A (DGEBA)/MHHPA. In addition, the incorporation of bis‐trifluoromethyl groups led to enhanced dielectric properties with lower dielectric constant (D_k 2.93) of DGEBHF/MHHPA compared with cured DGEBA resins (D_k 3.25). The cured fluorinated epoxy resin also gave lower water absorption measured in two methods relative to its nonfluorinated counterparts. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2801–2808, 2013     

Crosslinking by etherification of bisepoxide with adducts of divalent metal salts of p-aminobenzoic acid and anhydride

Crosslinking by etherification of a large excess of bisepoxide with adducts of divalent metal salts of p-aminobenzoic acid and dicarboxylic acid anhydride was investigated. As the divalent metals, Mg and Ca were selected and hexahydrophthalic anhydride was the anhydride used. As the bisepoxide, bisphenol A diglycidyl ether was used. In the crosslinking reactions, the metal carboxylate groups showed catalytic action and the Ca carboxylate group showed higher catalytic activity than did the Mg carboxylate group. Therefore, the crosslinking reactions were supposed to proceed via an ionic mechanism in which the carboxylate anion is concerned. As for the physical and other properties of the metal-containing cured resins, the T_g determined by dynamic mechanical properties increased with increase in the metal content. Also, the heat-distortion temperature increased with increase in the metal content. Interestingly, the cured resins showed very high impact strength and the strength increased markedly with decrease in the T_g. Scanning electron micrographs for fracture surfaces of the cured resins with high impact strength showed uneven patterns, which suggests microphase separation. From TGA and DTA, it was suggested that the metal carboxylate groups accelerated thermal decomposition. In addition, the cured resins exhibited high boiling water and water resistances. © 1996 John Wiley & Sons, Inc.     

Fabrication and characterization of the mechanical properties of multi-walled carbon nanotube-reinforced epoxy resins by e-beam irradiation

In this study, the multi-walled carbon nanotubes (MWNT) were reinforced to epoxy resin as fabrication of epoxy/MWNT nanocomposites by electron beam (e-beam) curing. An attempt is made to disperse MWNT into diglycidyl ether of bisphenol A (DGEBA) as epoxy resins, using triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. E-beam irradiation effect on the curing of the epoxy resin was investigated in oxygen and nitrogen atmospheres at room temperature. The flexural modulus was measured by a universal testing machine (UTM). Here, the flexural modulus factor exhibits an upper limit at 0.3 wt% MWNT. The dynamic mechanical and thermal properties of the irradiated epoxy resins were characterized using DMA, DSC and TGA machines. DMA curves of the storage modulus revealed an increase with an increasing MWNT content and radiation dose. However, the T_g curve decreased as a function of the increasing MWNT content and radiation dose. The thermal properties of the TGA and DSC data were improved by increasing the content of the MWNT and the radiation dose. Likewise, the thermal properties were stabilized by increasing the amount of initiator and irradiating the resins in a nitrogen atmosphere.     

Preparation and properties of high performance phthalide‐containing bismaleimide modified epoxy matrices

A series of intercrosslinked networks formed by diglycidyl ether of bisphenol A epoxy resin (DGEBA) and novel bismaleimide containing phthalide cardo structure (BMIPP), with 4,4′‐diamino diphenyl sulfone (DDS) as hardener, have been investigated in detail. The curing behavior, thermal, mechanical and physical properties and compatibility of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, scanning electron microscopy (SEM) and water absorption test. DSC investigations showed that the exothermic transition temperature (T_p) of the blend systems shifted slightly to the higher temperature with increasing BMIPP content and there appeared a shoulder on the high‐temperature side of the exothermic peak when BMIPP content was above 15 wt %. TGA and DMA results indicated that the introduction of BMIPP into epoxy resin improved the thermal stability and the storage modulus (G′) in the glassy region while glass transition temperature (T_g) decreased. Compared with the unmodified epoxy resin, there was a moderate increase in the fracture toughness for modified resins and the blend containing 5 wt % of BMIPP had the maximum of impact strength. SEM suggested the formation of homogeneous networks and rougher fracture surface with an increase in BMIPP content. In addition, the equilibrium water uptake of the modified resins was reduced as BMIPP content increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal behavior and properties of naphthalene containing bismaleimide–triazine resins

A series of bismaleimid·triazine (BT) resins were prepared from various dicyanate esters and 2,7-bis(4-maleimidophenoxy)naphthalene (BMPN), which contains a naphthalene group and an aryl ether linkage in the backbone. Their curing behaviors were characterized by differential scanning calorimetry. The exotherm temperature and polymerization reactivity were strongly affected by the chemical structure of the various dicyanate ester monomer. Thermal behaviors were investigated by thermogravimetric analyses and dynamic mechanical analyses. The glass transition temperatures (T_g) of these cured resins with bismaleimide/dicyanate ester at the 1/2 molar ratio were in the range of 250–322°C, and exhibited excellent thermal stability up to 400°C in nitrogen. These results provided a structure–properties relationship for the cured bismaleimid·triazine resins. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1199–1207, 1998