Modification of epoxy–anhydride thermosets using a hyperbranched poly(ester‐amide): I. Kinetic study

An epoxy‐anhydride formulation used for the coating of electrical devices was modified with a commercially available hyperbranched poly(ester‐amide), Hybrane? S2200, in order to improve the thermal degradability of the resulting thermoset and thus facilitate the recovery of substrate materials after use of the component. The curing kinetics of the unmodified and modified formulations were studied in detail with differential scanning calorimetry, Fourier transform infrared spectroscopy and rheology. The results suggest that S2200 gets incorporated into the network structure and the curing kinetics are accelerated by the presence of hydroxyl groups from S2200. Copyright © 2012 Society of Chemical Industry     

Novel epoxidized hyperbranched poly(phenylene oxide): Synthesis and application as a modifier for diglycidyl ether of bisphenol A

A novel epoxidized hyperbranched poly(phenylene oxide) (EHPPO) is designed and synthesized successfully. The structure of EHPPO is characterized by Fourier transform infrared spectra‐ and quantitative ¹³C nuclear magnetic resonance spectrum. The synthesized EHPPO is added into diglycidyl ether of bisphenol A as a modifier in different ratios to form hybrids and cured by an anhydride curing agent. Effects of EHPPO addition on the properties of the cured hybrids are investigated. Thermal mechanical analysis results suggest that addition of EHPPO can increase the free volume of the cured hybrid materials. Dynamic mechanical analysis characterizations show that the crosslinking density increases with the increase in EHPPO content. Furthermore, addition of EHPPO results in an improvement in thermal and mechanical properties. The toughening mechanism is also discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An epoxy‐ended hyperbranched polymer as a new modifier for toughening and reinforcing in epoxy resin

A new epoxy‐ended hyperbranched polyether (HBPEE) with aromatic skeletons was synthesized through one‐step proton transfer polymerization. The structure of HBPEE was confirmed by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements. It was proved to be one high efficient modifier in toughening and reinforcing epoxy matrix. In particular, unlike most other hyperbranched modifiers, the glass transition temperature (T_g) was also increased. Compared with the neat DGEBA, the hybrid curing systems showed excellent balanced mechanical properties at 5 wt % HBPEE loading. The great improvements were attributed to the increased cross‐linking density, rigid skeletons, and the molecule‐scale cavities brought by the reactive HBPEE, which were confirmed by dynamical mechanical analysis (DMA) and thermal mechanical analysis (TMA). Furthermore, because of the reactivity of HBPEE, the hybrids inclined to form a homogenous system after the curing. DMA and scanning electron microscopy (SEM) results revealed that no phase separation occurred in the DGEBA/HBPEE hybrids after the introduction of reactive HBPEE. SEM also confirmed that the addition of HBPEE could enhance the toughness of epoxy materials as evident from fibril formation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1064‐1073, 2013     

Solid–solid phase‐change materials based on hyperbranched polyurethane for thermal energy storage

A hyperbranched polyol (HBP) was synthesized with poly(ethylene glycol) (PEG) as the core molecule and 2,2‐bis(hydroxymethyl) propionic acid as the chain extender. Then, a series of hyperbranched polyurethane phase‐change materials (HP‐PCMs) with different crosslinking densities was synthesized with isophorone diisocyanate and HBP as a molecular skeleton and PEG 6000 as a phase‐change ingredient. ¹H‐NMR, gel permeation chromatography, and Fourier transform infrared spectroscopy confirmed the successful synthesis of the HBP and HP‐PCMs. The polarization optical microscopy and wide‐angle X‐ray diffraction results show that the HP‐PCM exhibited good crystallization properties, but the crystallinity was lower than that of PEG 6000. The analysis results from differential scanning calorimetry indicated that the HP‐PCMs were typical solid–solid phase‐change materials with suitable phase‐transition temperatures. In addition, HP‐PCM‐3, with an appropriate degree of hyperbranched structure, possessed the highest thermal transition enthalpy of 123.5 J/g. Moreover, thermal cycling testing and thermogravimetric analysis showed that the HP‐PCMs exhibited good thermal reliability and stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45014.     

Six‐arm star‐shaped polymer with cyclophosphazene core and poly(ε‐caprolactone) arms as modifier of epoxy thermosets

A six‐arm star‐shaped poly(ε‐caprolactone) (s‐PCL) based on cyclophosphazene core was obtained by presynthesis of a hydroxy‐teminated cyclophosphazene derivative and subsequent initiation of the ring‐opening polymerization of ε‐caprolactone, and its use in different proportions as toughening modifier of diglycidylether of bisphenol A/anhydride thermosets was studied. The star‐shaped polymer was characterized to have approximately 30 caprolactone units per arm. Differential scanning calorimetry revealed a nonsignificant influence on the curing process of the epoxy‐anhydride formulation by the addition of s‐PCL. The s‐PCL‐modified epoxy thermosets exhibited a great improvement in both toughness and strength compared with the neat resin, as the result of a joint effort by the internal rigid core and the external ductile polyester chains of s‐PCL. When the addition of the modifier was 3 wt %, an optimal mechanical and thermomechanical performance was achieved. The impact resistance and tensile strength of the cured epoxy resin were enhanced by 150% and 30%, respectively. The glass transition temperature was also increased slightly. Moreover, the addition of the star‐shaped modifier had little harmful effect on the thermal stability of the material. Thus s‐PCL was proved to be a superior toughening agent without sacrificing thermal and mechanical properties of the thermosets. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44384.     

Synthesis and properties of novel hyperbranched polyimides end‐capped with metallophthalocyanines

A fluorinated hyperbranched polyimide (HBPI) is synthesized by using a triamine monomer, 1,3,5‐tris(2‐trifluoromethyl‐4‐aminophenoxy)benzene (TFAPOB) (B₃), as a “core” molecule, 4,4′‐oxydiphthalic anhydride (ODPA) as a A₂ monomer, and 4‐aminophthalonitrile as an end‐capping reagent. After that, a series of novel fluorinated hyperbranched polyimides end‐capped with metallophthalocyanines were prepared by the reactions of dicyanophenyl end‐capped hyperbranched polyimide with excessive amounts of 1,2‐dicyanobenzene and the corresponding metal salt in quinoline. The resulting polyimides containing metallophthalocyanine unites shows optical absorption in the visible region. The absorption bands of the polymers in chloroform solution are in the range of 665–701 nm. These polyimides show glass transition temperatures between 216 and 225°C, and the 5 wt % weight loss temperature of the polymers varied from 440 to 543°C under nitrogen. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of epoxy‐functionalized hyperbranched poly(phenylene oxide) and its modification of cyanate ester resin

High curing temperature is the key drawback of present heat resistant thermosetting resins. A novel epoxy‐functionalized hyperbranched poly(phenylene oxide), coded as eHBPPO, was synthesized, and used to modify 2,2′‐bis (4‐cyanatophenyl) isopropylidene (CE). Compared with CE, CE/eHBPPO system has significantly decreased curing temperature owing to the different curing mechanism. Based on this results, cured CE/eHBPPO resins without postcuring process, and cured CE resin postcured at 230°C were prepared, their dynamic mechanical and dielectric properties were systematically investigated. Results show that cured CE/eHBPPO resins not only have excellent stability in dielectric properties over a wide frequency range (1–10⁹Hz), but also show attractively lower dielectric constant and loss than CE resin. In addition, cured CE/eHBPPO resins also have high glass transition temperature and storage moduli in glassy state. These attractive integrated performance of CE/eHBPPO suggest a new method to develop high performance resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The preparation,characterization, and properties of silver nanoparticle reinforced reduced graphene oxide–poly(amidoamine) nanocomposites

A simple approach was employed to synthesize silver nanoparticle (Ag NP) reinforced reduced graphene oxide–poly(amidoamine) (Ag‐r‐RGO–PAMAM) nanocomposites. The structural changes of the nanocomposites with the PAMAM and Ag NPs were confirmed by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Raman spectroscopy, and scanning electron microscopy. In addition, the performance was characterized with thermogravimetric and electrical conductivity instruments. The results indicate that the Ag NPs are well dispersed in fine size on the surface of the RGO–PAMAM composites, which results in an increase of at least 38% in thermostability and a certain enhancement in electrical conductivity. It is worth noting that the electrical conductivity of the nanocomposites was approximately 5.88 S cm^?1, which was higher than that of RGO–PAMAM, and increases with the rising content of silver nanoparticles. Meanwhile, the Ag‐r‐RGO–PAMAM nanocomposites still maintain a favorable dispersion in organic solvents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45172.     

Thermomechanical and chemorheology properties of a thermosetting acrylic/melamine clearcoat modified with a hyperbranched polymer

The work presented here aims at studying the thermomechanical and chemorheological properties of an automotive clearcoat containing an acrylic/melamine resin modified with a hyperbranched poly ester‐amide (HBP) additive. Rheological experiments were conducted at ambient (25°C) and curing temperature (140°C). Dynamic mechanical thermal analysis and hardness measurements were performed to reveal the influence of HBP content on the behavior of the cured samples. It was found that the viscosity of the resin containing HBP samples considerably decreased. Although curing degree and mechanical properties were improved at low HBP loadings, a reverse effect was seen at higher contents. Dynamic rheological results during curing showed that although low amount of HBP resulted in an early gel point (GP), higher HBP loading postponed the GP. This loading‐dependent behavior was explained by the influence of HBP on viscosity and reactivity of the system on which the curing performance was influenced oppositely. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Curing behavior and dielectric properties of hyperbranched poly(phenylene oxide)/cyanate ester resins

A novel hyperbranched poly(phenylene oxide) (HBPPO) modified 2,2′‐bis(4‐cyanatophenyl) isopropylidene (BCE) resin system with significantly reduced curing temperature and outstanding dielectric properties was developed, and the effect of the content of HBPPO on the curing behavior and dielectric properties as well as their origins was thoroughly investigated. Results show that BCE/HBPPO has significantly lower curing temperature than BCE owing to the different curing mechanisms between the two systems, the difference also brings different crosslinked networks and thus dielectric properties. The dielectric properties are frequency and temperature dependence, which are closely related with the content of HBPPO in the BCE/HBPPO system. BCE/2.5 HBPPO and BCE/5 HBPPO resins have lower dielectric constant than BCE resin over the whole frequency range tested, while BCE/10 HBPPO resin exhibits higher dielectric constant than BCE resin in the low frequency range (<10⁴ Hz) at 200°C. At 150°C or higher temperature, the dielectric loss at the frequency lower than 10² Hz becomes sensitive to the content of HBPPO. These phenomena can be attributed to the molecular relaxation. Two relaxation processes (α‐ and β‐relaxation processes) are observed. The β‐relaxation process shifts toward higher frequency with the increase of temperature because of the polymer structure and chain flexibility; the α‐relaxation process appears at high temperature resulting from the chain‐mobility effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Epoxide‐terminated hyperbranched polyether sulphone as triple enhancement modifier for DGEBA

Epoxide‐terminated hyperbranched polyether sulphones (EHBPESs) with different backbone structures were synthesized and used as tougheners for diglycidyl ether of bisphenol‐A (DGEBA) curing system, which result in nonphase‐separated cured networks. Effects of backbone structure (at comparable degree of polymerization) and loading contents on the mechanical and thermal properties of cured hybrids were investigated. The hybrid containing EHBPES3, which has the most flexible backbone, shows the best mechanical performance and highest glass transition temperature (T_g). Compared with unmodified system, the impact strength, tensile strength, elongation at break of the hybrid containing 5% EHBPES3 increased by 69.8%, 9.4%, and 60.2%, respectively. The balanced improvements were attributed to the increased crosslink density and fractional free volume as well as the unique inhomogeneous network structure because of incorporation of hyperbranched modifiers with proper structure and loading contents. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41910.     

Simultaneously reinforcing and toughening epoxy network with a novel hyperbranched polysiloxane modifier

A novel hyperbranched polysiloxane (HBPSi) was prepared and cured into an epoxy–aromatic amine network without phase separation. A moderate content of HBPSi increased the crosslinking density of the crosslinking network because of the active amino groups on the HBPSi. Meanwhile, the secondary amine on the HBPSi molecules improved the homogeneity of the epoxy network. At a 5 wt % HBPSi content, the tensile strength, tensile modulus, and flexural modulus were enhanced by 17.6%, 13.7%, and 17.5%, respectively, compared with those of the neat epoxy resin. Meanwhile, the elongation at break and impact strength were 63.3% and 49.1% higher than those of the neat epoxy resin, respectively. HBPSi also significantly increased the char yield of the material and decreased the thermal weight loss rate; this indicated an improved thermal stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46340.     

Synthesis and characterization of hybrid films from hyperbranched polyester using a sol–gel process

Hybrid organic/inorganic materials were prepared by an in situ sol–gel process using tetraethoxysilane (TEOS) in the presence of hyperbranched polyester. The influences of hyperbranched polyester molar mass as well as the amount of TEOS were examined. The condensation degree was characterized by solid state ²⁹Si NMR. The combination of solubility tests, calcination tests, SAXS and dynamic mechanical analysis allowed us to investigate the hybrid material nanostructure. The results show high compatibility between the inorganic silica phase and the organic polymer phase, due to the spherical shape of the hyperbranched polymer and its numerous hydroxyl groups. As a consequence, a continuous inorganic phase was formed even with a low silica precursor content without any macroscopic phase separation. These hybrid materials have a high T_g and high storage modulus even at an elevated temperature combined with improved thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39830.     

Flame retardant and mechanical properties of epoxy composites with ammonium polyphosphate and hyperbranched silicon-containing polymers

The epoxy resin was mixed with ammonium polyphosphate (APP) and hyperbranched silicon-containing polymers (HBP-B2). The cured composites were investigated by thermogravimetric analysis, Underwriters Laboratory standard for the flammability properties under vertical burning (UL-94V), and limited oxygen index (LOI) test methods. The LOI of 43.5 and could be obtained at the weight ratio of 70:25:5 for the epoxy resin:APP:HBP-B2, Sample A25B5, and the LOI was higher than that of the composite with 30 wt % APP only, Sample A30B0, of which the LOI was 34.5. It suggested that the HBP-B2 could cooperate with the epoxy/APP composite to form a more effective protection layer during combustion, which resulted in a higher second-stage thermal degradation temperature. During the UL-94V test, the flame was extinguished immediately once the burner was removed. Furthermore, the tensile and impact strength of the epoxy/APP composite could also be improved by using HBP-B2 compound as the toughening agent. The composite containing 20% of APP and 10% of HBP-B2, Sample A20B10, still had excellent flame retardant properties with a V-0 rating. Moreover, the tensile strength and impact strength of that composite got 19 and 25% increases compared with the Sample A30B0, which contained 30% of APP only. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48857.     

Aging properties and hydrophilicity of maize starch plasticized by hyperbranched poly(citrate glyceride)

Hyperbranched poly(citrate glyceride)s (HBPETs) as plasticizers were mixed with maize starch (S) via cooking and film formation. The structure, aging properties, and hydrophilicity of the plasticized starches were studied by means of Fourier transform infrared spectroscopy, X-ray diffraction, tension testing, contact angle testing, solubility measurements, moisture absorption, and water vapor permeability (WVP). Compared with a glycerol–S plasticized film, the HBPET–S composite films had better mechanical properties in terms of both strength and elongation at break, better aging resistance, less moisture absorption, less WVP, and more hydrophobicity on the film surface. The mechanisms behind the performances resulted from stronger and more stable H bonds between the abundant active end groups of HBPET and hydroxyls of starch and the high branching degree of the HBPETs; this was helpful for effectively inhibiting the recrystallization of starch. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46899.     

Synthesis and application of hyperbranched poly(urethane‐urea) finishing agent with amino groups

The isocyanate‐terminated linear polyurethane prepolymer (LPPU) was successfully synthesized via step‐by‐step polymerization, with isophorone disocyanate (IPDI) and polytetramethylene ether glycol (PTMG, M_n = 2000 g/mol) used as raw materials, dibutyltin dilaurate (DBTDL) as the catalyst, 1,4‐butanediol (BDO) as the chain extender and anhydrous ethanol (EtOH) as the blocking agent. Then the hyperbranched poly (urethane‐urea) (HBPU) containing amino groups was synthesized by grafting LPPU on amino‐terminated hyperbranched polymers (NH₂‐HBP). The molecular structure of LPPU and HBPU were characterized by means of FT‐IR and ¹H‐NMR. It was founded that LPPU and HBPU were successfully synthesized as anticipated. The thermal stability and crystalline morphology of LPPU and HBPU were characterized and analyzed by TG and XRD. Additionally, it was also found that, after addition of 10% HBPU, the water absorption rate, water vapor transmission rate, and water vapor permeability increased markedly by 162.02%, 400.00%, 260.00%, respectively. The tensile strength of membrane decreased by 24.57% and the elongation at break increased by 26.92%. Compared with the leather finished by commercial PU finishing agent, the leather finished by HBPU presented better properties. The water vapor permeability of the leather finished by increased by 13.0%, and the dry‐ and wet‐rub resistances and the physical and mechanical performances were excellent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44139.     

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

The rheological behavior of two series of aliphatic hyperbranched (HB) polyesters, based on 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) and di‐trimethylol propane (Di‐TMP) as a tetrafunctional core, was studied. The effect of the size (pseudo‐generation number, from second to eight) and structure on the melt rheological properties was investigated for a series of hydroxyl‐terminated HB polyesters. In addition, the influence of the nature and degree of modification of the terminal OH groups in a series of fourth‐generation polyesters end‐capped with short and long alkyl chains and some aryl groups on the rheological properties was analyzed. The time–temperature superposition procedure was applied for the construction of master curves and for the analysis of the rheological properties of HB polyesters. The data obtained from WLF analysis of the HB polyesters showed that the values of the thermal coefficient of expansion of free volume α_f and the fractional free volume at the glass transition temperature, f_g, increase with increasing size of the HB polyesters. It was shown that the modified HB polyesters exhibited lower T_g and T_G′=G″ temperatures, above which viscous became dominant over elastic behavior. From an analysis of the master curves of the modified HB polyesters, it was observed that with increasing degree of modification, both storage and loss modules and complex dynamic viscosity and apparent energy for viscoelastic relaxation decrease, because of reduced intermolecular hydrogen interactions. They do not exhibit a plateau of rubbery behavior, which confirms that no entanglements are present and that the molar masses are below the critical molar mass. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41479.     

Non‐isothermal degradation kinetics of N,N′‐bismaleimide‐4,4′‐diphenylmethane/barbituric acid based polymers in the presence of hydroquinone

The non‐isothermal degradation kinetics of the cured polymer samples of N,N′‐bismaleimide‐4,4′‐diphenylmethane/barbituric acid [BMI/BTA = 2/1 (mol/mol)] based polymers in the presence of hydroquinone (HQ) and native BMI/BTA was investigated by the thermogravimetric (TG) technique. By adding 5 wt % HQ into the BMI/BTA polymerization, the activation energy (E_a) of the thermal degradation process increased significantly in comparison with native BMI/BTA. Thus, the thermal stability of the cured polymer sample in the presence of HQ was greatly improved. The thermal degradation process exhibits three distinct stages. The key kinetic parameters associated with these stages were attained via the model‐fitting method. For the sample of native BMI/BTA, the thermal degradation process was primarily controlled by nucleation, followed by the multi‐decay law in the first stage. In contrast, the reaction order model adequately described the thermal degradation kinetics in the second stage. As to the last stage, the complex processes were described satisfactorily by the best‐fitted reaction model. For the sample of BMI/BTA/5 wt % HQ, the degradation process was controlled by the nucleation mechanism, followed by the multi‐molecular decay law in the first stage. In contrast, the second stage was controlled by the mixed mode of the competitive reaction order mechanism and 3‐D diffusion mechanism. In the third stage, the complex processes were also adequately described by the best‐fitted reaction model. All the experimental results illustrated that incorporation of 5 wt % HQ into the BMI/BTA based polymer resulted in the best thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1923–1930, 2013     

Effect of hyperbranched poly(citric polyethylene glycol) with different polyethylene glycol chain length on starch sizing and compatibility with blended yarns

Blend of starch and water-soluble polyester has been widely used in warp sizing because of its good film-forming, biodegradability, and adhesion to polyester/cotton blended yarns (T/C). In this study, a series of hyperbranched polyesters poly(citric polyethylene glycol) (PCPEG) with varied chain length of polyethylene glycol (PEG) were prepared with citric acid and PEG at molar ratio of 1:3 and 150 °C for 3 h in vacuum and characterized by Fourier transformed infrared, gel permeation chromatography, and ¹H nuclear magnetic resonance. PCPEG blended maize starch (PCPEG/MS) as sizing agent of T/C 80/20 and effects of PEG chain length of PCPEG on the property of the blending sizing agent were studied. Results indicated PCPEG could improve the compatibility between starch and T/C 80/20 and the optimum content of PCPEG as blended sizing agent was 8%. PCPEG not only decreased apparent viscosity of MS paste but also increased viscosity stability of the paste. In addition, with increase of PEG chain length of PCPEG, viscosity stability of PCPEG/MS paste increased, but the value of all adhesion performances of T/C 80/20 after sizing decreased. Long chain of PEG is not good for compatibility between PCPEG and starch. The starch blending PCPEG has potential applications in sizing blended yarns in textile industry. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48928.