High glass transition temperature bismaleimide‐triazine resins based on soluble amorphous bismaleimide monomer

A novel bismaleimide (DOPO‐BMI) with unsymmetrical chemical structure and DOPO pendant group has been prepared. The particular molecular structure makes DOPO‐BMI show an intrinsic amorphous state with a T_g about 135°C and excellent solubility in most organic solvents, which is beneficial to the processability of bismaleimide composite materials. A series of bismaleimide‐triazine (BT) resins have been prepared based on DOPO‐BMI and 2,2‐bis(4‐cyanatophenyl)propane at various weight ratios. The prepared BT resins show outstanding solubility in organic solvent and low viscosity about 10–671 mPa s at 180°C. The cured BT resins exhibit high glass transition temperature (T_g) over 316°C. As the weight ratio of DOPO‐BMI increases to 80% (BT80), the T_g can rise to 369°C (tan δ). The cured BT resins also show good thermal stability with the 5% weight loss temperature over 400°C under both nitrogen and air atmosphere. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42882.     

Nitrile functionalized benzoxazine/bismaleimide blends and their glass cloth reinforced laminates

A novel high‐performance resin blend composed of nitrile functionalized benzoxazine (CNBZ) and bismaleimide (4,4′‐bismaleimidodiphenyl methane) (BMI) was prepared via solvent method. Its curing behaviors, thermal properties, and mechanical properties were studied by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal testing machine, respectively. The results showed that the addition reaction between phenolic hydroxyl group and the double bond occurred except for the homopolymerization of CNBZ and BMI. When BMI content was more than 40%, the cured CNBZ/BMI blends exhibited higher glass transition temperatures (T_gs) than CNBZ and BMI homopolymers, which reached up to 334°C. Meanwhile, when BMI content was 40%, the tensile strength, flexural strength, and shearing strength reached up to 69, 235, and 12.9 MPa, respectively, which exhibited the comparable mechanical properties with BT resin. Furthermore, the glass cloth (GF) reinforced laminates based on these blends were prepared. The results showed that when BMI content was 40%, their tensile strength, flexural strength, and impact strength reached up to 334 MPa, 593 MPa, and 145 KJ m^?2, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41072.     

Investigation of the curing mechanism and properties of bismaleimide-triazine resins containing phenolphthalein and cyano group

A series of bismaleimide-triazine (BT) resins with and without O, O′-diallyl bisphenol A (DABPA) were produced by mixing 2, 2-bis (4-cyanatophenyl) propane (BADCy) and MCBMI (2,6-bis(4-(1-(4-(4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)phenoxy)-3-methylphenyl)-3-oxo-1,3-dihydroisobenzofuran-1-yl)-2-methylphenoxy)benzonitrile). The resins show just one glass-transition temperature (T _g) and enhanced flexural properties as well as superior fracture toughness compared with commercial BDM/BADCy system, in which BDM is (N,N′-bismaleimido-4,4′-diphenylmethane). Introduction of DABPA can decrease the curing temperature of bismaleimide-triazine (BT) resins but increase its impact strength. When the mole of DABPA reach up to 1.2, the impact strength was increased by 1.34 times in comparison with BDM/ BADCy system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 136, 47420.     

Synthesis of a novel azaphosphorine flame retardant and its application in epoxy resins

A novel P? C? N bond containing azaphosphorine, 5‐(4‐hydroxy)anilinomethyl‐1,3‐di(4‐hydroxy)phenyl‐1,3,5‐diazaphosphorinane (ADDPP‐OH), which could be used as both a cocuring agent and a flame‐retarding agent for epoxy resins (EPs), was synthesized from tetrakis(hydroxymethyl)phosphonium sulfate and characterized by FTIR, ¹H‐NMR, ¹³C‐NMR, ³¹P‐NMR, and so on. Compared with the pure EP, the ADDPP‐OH–EP composites showed increased decomposition temperatures and char yields. When the content of ADDPP‐OH was 10 wt %, the cured EP composite possessed a limiting oxygen index value of 33.7% and passed the V‐0 rating of the UL‐94 test. The mechanical properties of the ADDPP‐OH–EP composites was improved because of the increased crosslinking density. In addition, the morphology of the residual char indicated an intumescent and multiporous structure in the inner space and a compact and continual appearance in the outer layer; this was important in preventing the materials from burning further. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45721.     

Thermosetting allyl resins derived from soybean fatty acids

A novel class of thermosetting resins based on allylated and transesterified epoxidized soybean oil (AE‐ESBO) curable by radical mechanism was developed. The AE‐ESBO was prepared from ESBO by oxirane ring‐opening and then transesterification with allyl alcohol. A family of rubbery to glassy resins was prepared by radical copolymerization of AE‐ESBO with different concentrations of maleic anhydride (MA). Glass transition temperatures (T_g) of these resins ranged from below room temperature to about 130°C based on the amount of MA. In spite of the presence of anhydride groups, water absorption was low <2% even when maleic anhydride was 30% of total weight. Low sol content after extraction and low swelling in toluene indicated high crosslinking density. Tensile moduli of these resins were up to 1.4 GPa and tensile strengths up to 37 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biobased thermosetting resins composed of terpene and bismaleimide

Prepolymers prepared by reactions of 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) with myrcene (Myr) and limonene (Lim) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 150°C were compressed at 250°C to produce crosslinked Myr/BMI [molar ratio = 2:2–2:5 (MB22–MB25)] and Lim/BMI [molar ratio = 1:1 (LB11)] resins. The ¹H‐NMR analysis of the model reaction products of Lim and Myr with N‐phenyl maleimide (PMI) in DMI at 150°C revealed that a Diels–Alder reaction for Myr/PMI and a vinyl copolymerization for Lim/PMI preferentially proceeded in addition to the occurrence of the ene reaction to some extent. The Fourier transform infrared data of the cured resins were consistent with the results of the model reactions. All of the cured resins, except for MB22, showed tan δ peak values and 10% weight loss temperatures that were higher than 330 and 440°C, respectively. The flexural strength and modulus values of the MBs were higher than those of LB11. Field emission scanning electron microscopy analysis revealed that MB22–MB24 were homogeneous, whereas some combined particles appeared in LB11. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and properties of bisphenol A‐based bis‐phthalonitrile composite laminates

A series of bisphenol A (BPA)‐based 2,2‐bis‐[4‐(3,4‐dicyanophenoxy)phenyl]propane (BAPh) prepolymers and polymers were prepared using BPA as a novel curing agent. Ultraviolet–visible and Fourier transform infrared spectroscopy spectrum were used to study the polymerization reaction mechanism of the BAPh/BPA polymers. The curing behaviors were studied by differential scanning calorimetry and dynamic rheological analysis, the results indicated that the BAPh/BPA prepolymers exhibit large processing windows (109.5–148.5°C) and low complex viscosity (0.1–1 Pa·s) at moderate temperature, respectively. Additionally, the BAPh/BPA/glass fiber (GF) composite laminates were manufactured and investigated. The flexural strength and modulus of the composite laminates are 548.7–632.8 MPa and 25.7–33.2 GPa, respectively. The thermal stabilities of BAPh/BPA/GF composite laminates were studied by thermogravimetry analysis. The temperatures at 5% weight loss (T_5%) of the composite laminates are 508.5–528.7°C in nitrogen and 508.1–543.2°C in air. In conclusion, the BAPh/BPA systems can be used as superior matrix materials for numerous advanced composite applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improving properties of ceramic silicone rubber composites using high vinyl silicone oil

Reactive high vinyl silicone oil (HVSO) was selected to prepare the ceramic silicone rubber composites. The effects of HVSO on the mechanical properties and thermal stabilities of ceramic silicone rubber composites were investigated. The structures of the cross‐linked network of silicone rubber with or without HVSO were studied. The intermolecular space of silicone rubber was enlarged, and the cross‐linked point was concentrated by addition of HVSO, which was demonstrated by cross‐linking densities, scanning electron microscope (SEM) images, and dynamic mechanical analysis (DMA). The cross‐linked network model was formed with the slipping of the cross‐linked points along with the silicone rubber chain. Mechanical properties of composites were enhanced by the formation of this cross‐linked network. The tear strength, tensile strength, and elongation at break of the composites were increased by 18.5%, 13.2%, and 37.4% by the adding of 2 phr HVSO, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41864.     

Properties and paper sizing application of waterborne polyurethanemicroemulsions: Effects of extender,cross‐linker,and polyol

A series of waterborne polyurethane (WPU) microemulsions were synthesized through self‐emulsification methodology, using toluene‐2,6‐diisocyanate, polytetramethylene glycol (PTMG), poly‐caprolactonediol (PCL), and dimethylol propionic acid (DMPA) as monomers; isophorone diamine (IPDA) as chain extender; and aziridine as cross‐linking agent. The resultant WPU microemulsions were utilized as surface‐sizing agents for cellulose fiber paper. The influences of IPDA content, PTMG/PCL molar ratio, and aziridine content on the physicochemical properties of the resultant emulsions and sized paper have been investigated in detail. The WPU microemulsion displayed better surface sizing properties when it was prepared under the following conditions: the IPDA content of 2.96%, PTMG/PCL molar ratio of 0:4, and aziridine content of 2.0 wt %. The relationships between the WPU structure and properties of WPU films and sized paper were clearly illustrated. The mechanical properties and water resistance of sized paper were not only depended on the interactions, chain entanglements, and cross‐linking density among the WPU chains, but also relied on the interactions among polymers and fibers, as well as the polarity and stiffness of surface sizing agent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43211.     

Synthesis of epoxy curing agents containing different ring structures and properties investigation of the cured resins

Two kinds of aliphatic epoxy curing agents containing ring structures were synthesized from rosin acid and isosorbide, respectively. They were cured with diglycidyl ether bisphenol A (DER331) and the ultimate propertied of the cured resins were investigated. For comparison, the petroleum‐based curing agent containing planar benzene ring was synthesized from terephthalic acid. The chemical structures of the synthesized curing agents were identified by Fourier transform‐infrared and H‐nuclear magnetic resonance. The ultimate properties of the cured epoxy resins were investigated by thermogravimetric analysis and dynamic mechanical analysis. Especially, the effects of ring structure on their shape memory properties were studied in terms of shape fixity, shape recovery, and shape recovery time. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44219.     

The influence of cross‐linking reaction on the mechanical and thermal properties of polyarylene ether nitrile

The processing of cross‐linked polyarylene ether nitrile (PEN), which has a triazine rings structure, has been investigated under different reaction times and temperatures. In this study, the PEN films prepared by the tape‐casting formed the thermally stable triazine rings by catalytic cross‐linking reaction gradually, which was characterized by Fourier transform infrared spectroscopy. The chemical cross‐linking reaction occurred as the CN group absorption of PEN at 2221 cm⁻¹ decreased and a new absorption peak, at 1682 cm⁻¹, was observed, and the absorption peak intensity would be progressively larger, with the extension of the processing time. After the formation of cross‐linking networks, the cross‐linking degree and thermal and mechanical properties of the processed films were improved substantially, compared with the untreated films. The film with added ZnCl₂ as the catalyst was more rapidly cross‐linked, and its properties were better than that without catalyst at the same treatment conditions. The glass‐transition temperature (T_g) of PEN films processed at 350°C for 4 h (213.65°C) was higher than that of PEN films before the treatment (161°C), and the tensile strength was also improved significantly. The PEN was processed at 350°C for 2 h, whose initial decomposition temperature increases by about 10°C, compared with that of untreated film, at one time. The rheology behavior of the cross‐linked films was processed on dynamic rheometer to monitor and track the process of polymer cross‐linking reaction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of silicon-containing bismaleimide resins

Two novel bismaleimide (BMI) monomers containing silicon atom in the structure, i.e., bis[4-(4-maleimidophenylcarbonyloxy)phenyl]dimethylsilane (BMI-SiE1) and bis[4-(4-maleimidophenyloxycarbonyl)phenyl]dimethylsilane (BMI-SiE2), were designed, synthesized, and polymerized with and without the use of diamine as comonomers to yield novel silicon-containing BMI resins. Both monomers obtained are readily soluble in organic solvents, such as chloroform and N, N-dimethylformamide. Differential scanning calorimetry and thermogravimetric analysis investigation of these two monomers indicated a high polymerization temperature (T_p > 240°C) and a good thermal and thermo-oxidative stability of cured BMI resins. The onset temperature for 5% weight loss was found to be above 450°C in nitrogen and above 400°C in the air. Polymerization of BMI-SiE1 and BMI-SiE2 with 4,4′-diaminodiphenylether (DPE) yielded a series of polyaspartimides that had good solubility and could be thermally cured at 250°C. TGA investigations of the cured diamine-modified BMI resins showed onset of degradation temperatures (T_ds) in the range of 344–360°C in nitrogen and 332–360°C in the air. Composites based on the cured diamine-modified BMI resins and glass cloth were prepared and characterized for their dynamic mechanical properties. All the composites showed high glass transition temperatures (e.g., >190°C) and high bending modulus in the range of 1000–2700 MPa. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Deeper insights into the thermal properties of epoxy thermoset resins using torsion measurements

The glass transition temperature (T_g) of epoxy thermosets is a critical material property that depends on the component chemistry, the final cross-link density, and processing conditions. This study incorporates dynamic mechanical analysis (DMA) testing with a torsion clamp geometry on a TA Instruments DHR-2 and differential scanning calorimetry (DSC) to characterize five different two-component epoxy-amine systems. Investigation of the T_g dependence on DMA frequency and heating shows that lowering the frequency from 1 to 0.01 Hz results in a T_g very similar to that measured using DSC, while a heating rate of 0.3°C/min using DMA gives a T_g comparable to the DSC measured value at 30°C/min. The DMA technique reveals secondary relaxation transitions and peak broadening in the tan(δ) plots of poorly mixed epoxy blends, quantified using full width at half maximum (FWHM) of tan(δ) peaks, and are indicative of a non-homogeneous cross-linked network and off-ratio blending, respectively. The increase in the FWHM due to poor mixing ranges from 8% to 96%. These parameters are easily measurable and quantifiable in DMA, but are not observed in DSC. The additional DMA insights are valuable for process development and failure analysis, and can improve the understanding of epoxies.     

Thermal properties of new bismaleimide resins containing hydrogen silsesquioxane and diallyl bisphenol A

Bismaleimide (BMI) resins modified with hydrogen silsesquioxane (HSQ) and diallyl bisphenol A (DABPA) (BMI‐HSQ‐DABPA resins) were prepared. DSC, FTIR, and TGA were used to characterize the curing behaviors, structures, and thermal properties of the BMI‐HSQ‐DABPA resins, respectively. The results showed that the glass transition temperatures and thermal stabilities of the cured BMI‐HSQ‐DABPA resins increased with the rise of the contents of HSQ. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Multi‐point monitoring of cross‐linking reactions

The feasibility of deploying optical fiber sensors to obtain qualitative and quantitative information on the cross‐linking characteristics of thermosetting resin systems has been demonstrated by a number of researchers. This article is concerned with the demonstration of a low‐cost fiber‐optic Fresnel sensor system for monitoring the cross‐linking reactions at multiple locations. Cross‐linking reactions can be influenced by a number of parameters including the stoichiometry of the resin and hardener, and the heat‐transfer rates in and out of the preform as a function of the cross‐section of the preform. In situations where there is a variation in the thickness of the preform or when large components are processed, a facility to monitor the cross‐linking reactions at multiple locations will be valuable because the rate and extent of the cross‐linking can be inferred. In this article, six Fresnel sensors were immersed in individual vials containing an epoxy/amine resin system and processed (cross‐linked) in an air‐circulating oven. One additional vial with a Fresnel sensor immersed in the neat epoxy resin (no hardener) was co‐located in the oven to enable the effect of temperature to be monitored. The feasibility of using the multiplexed Fresnel sensors for cure monitoring was demonstrated successfully. The sensors in the post‐cross‐linked samples were used to study the effects of heating and cooling cycles. The feasibility of detecting the glass transition temperature using the Fresnel sensor is discussed along with the factors that give rise to variability in the output Fresnel signals. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41088.     

Effect of dynamic crosslinking on tensile yield behavior of polypropylene/ethylene‐propylene‐diene rubber blends

Tensile yield behavior of the blends of polypropylene (PP) with ethylene‐propylene‐diene rubber (EPDM) is studied in blend composition range 0–40 wt % EPDM rubber. These blends were prepared in a laboratory internal mixer by simultaneous blending and dynamic vulcanization. Vulcanization was performed with dimethylol phenolic resin. For comparison, unvulcanized PP/EPDM blends were also prepared. In comparison to the unvulcanized blends, dynamically vulcanized blends showed higher yield stress and modulus. The increase of interfacial adhesion caused by production of three‐dimensional network is considered to be the most important factor in the improvement. It permits the interaction of the stress concentrate zone developed at the rubber particles and causes shear yielding of the PP matrix. Systematic changes with varying blend composition were found in stress‐strain behavior in the yield region, viz., in yield stress, yield strain, width of yield peak, and work of yield. Analysis of yield stress data on the basis of the various expressions of first power and two‐thirds power laws of blend compositions dependence and the porosity model led to consistent results from all expression about the variation of stress concentration effect in both unvulcanized and vulcanized blend systems. Shapes and sizes of dispersed rubber phase (EPDM) domains at various blend compositions were studied by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2104–2121, 2000     

Synthesis of isocyanurate-based imidazole carboxylate as thermal latent curing accelerator for thermosetting epoxy resins

A novel thermal latent curing accelerator, 1-(2-cyanoethyl)-2-methylimidazole/tris (2-carboxyethyl) isocyanurate adduct (2MICN-T), was successfully synthesized through an acid–base neutralization of tris(2-carboxyethyl)isocyanurate (TCEIC) and 1-(2-cyanoethyl)-2-methylimidazole (2MICN). It was further added into diglycidylether of bisphenol A based epoxy resin/methylhexahydrophthalic anhydride mixture to form one-component curing systems. With the addition of 2 wt% of 2MICN-T, the one-component system could be steadily stored for more than 1 month at room temperature, while the shelf life of 2MICN curing system was only 2 days. Nonisothermal differential scanning calorimeter also demonstrated the excellent thermal latency of 2MICN-T in low-temperature region and rapid initiation of the curing reaction when raising temperature. Compared to the cured resins with original 2MICN as accelerator, the resulted thermosets exhibited enhanced glassy storage modulus, glass transition temperature, and thermal stability when 2 wt% of 2MICN-T was applied. It was attributed to the chemical incorporation of the isocyanurate moieties with multi carboxyl groups and nitrogen-contained heterocyclic ring, effectively increasing the crosslinking density, chain rigidity, and heat resistance of the cured resin. Thus, it is suggested that 2MICN-T can play both roles as latent curing accelerator and modifier for one-component epoxy compounds, and is particularly recommended for application in electronic packaging fields.     

A facile way via integrating sol–gel and Grignard reaction to prepare siloxane/carbosilane hybridized benzocyclobutene resins with hyperbranched structure,low dielectric constant,and high thermal stability

The hybridization of siloxane- and carbosilane-based structures in molecular scale could combine their advantages of high thermal resistance and low dielectric constant. However, the hybridization still remained a big challenge in lacking convenient synthesis method. Herein, in this work, we developed a new method via simultaneous Grignard and sol–gel reactions of (chrolomethyl)trimethoxysilane to directly generate siloxane/carbosilane hybridized oligomers with hyperbranched structure. The oligomers were subsequently functionalized by benzocyclobutene and cured to produce crosslinked resins. As-resulted resins have low dielectric constant (~2.60) as compared with silica and higher thermal stability compared with polycarbosilane. The integrated high performance and facile preparation for these resins make them potentially used as low dielectric materials in integrating circuits insulating and wave transmitting.     

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.     

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.