Toward poly(furfuryl alcohol) applications diversification: Novel self‐healing network and toughening epoxy–novolac resin

Poly(furfuryl alcohol) bioresin (PFA) was synthesized and utilized through two distinct alloying strategies. It was crosslinked by a bismaleimide (BMI) via a Diels–Alder (DA) reaction. The novel PFA–BMI polyadduct network was spectrally, thermally, and thermo‐mechanically characterized and its thermally repeatable self‐healing behavior was visually established. The network showed a high pyrolytic thermostability (char yield ∼51% at 600 °C). PFA was also used for modification of epoxy–novolac resin (EP). EP hybrid resins containing 5, 10, and 15 wt % of PFA were cured by a polyamine hardener. Despite of different curing mechanisms of the two resins, PFA had no effect on EP curing behavior as revealed by differential scanning calorimetry, which proved homogeneous formation of the thermosets. PFA at the composition of 15 wt % improved tensile properties and toughness of EP, so that it almost doubled tensile modulus and elongation at break. However, PFA slightly deteriorated flexural properties of EP. PFA also decreased T_g of EP, with a maximum decrease of 22 °C. Besides, PFA disfavored initial thermostability of EP, but improved its pyrolytic char yield. In conclusion, PFA can be beneficial from smart materials to toughen hybrid epoxy thermosets with potential applications in composites, adhesives, and surface coatings. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45921.     

Curing and thermal behaviors of inorganic–organic hybrid polyarylacetylene resins with polyhedral oligomeric octa(propargylaminophenyl)silsesquioxane

Polyhedral oligomeric octa(propargylaminophenyl)silsesquioxane (OPAPS) was used to prepare composite resins with prepolyarylacetylene (prePAA). The curing and thermal behaviors of the PAA/OPAPS composites were studied through Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimetric (DSC), thermogravimetric (TGA), and scanning electron microscopic (SEM) analysis and by direct observation. The morphologies of the PAA/OPAPS resins proved that there was good compatibility between PAA and OPAPS. FTIR analysis indicated formation of a conjugated diene and aromatic ring groups in the thermal curing process of the resins. DSC analysis implied that the addition of OPAPS to prePAA could decrease the exothermic heat and widen the temperature range in the curing process of prePAA. According to TGA analysis, a 10 wt % addition of OPAPS to PAA can maintain the thermal stability of PAA in N₂ atmosphere and somewhat enhance the thermal‐oxidative stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flexible aliphatic poly(isocyanurate–oxazolidone) resins based on poly(ethylene glycol) diglycidyl ether and 4,4′‐methylene dicyclohexyl diisocyanate

New flexible aliphatic oxazolidone‐isocyanurate networks (AISOX) are obtained by reacting a low molecular weight diisocyanate (4,4′‐methylene dicyclohexyl diisocyanate, H₁₂MDI) and a macro‐diepoxyde (poly(ethylene glycol) diglycidyl ether, M_n = 526, PEGDGE) in different molar ratio. The curing reaction, carried out from 25 °C to 200 °C, is studied by using DSC and FTIR. The effect of the molar ratio of the two monomers on thermal and mechanical properties of AISOX resins is investigated by DSC, thermogravimetric analysis, stress?strain measurements and optical microscopy. Independently from the feed composition, it is observed that the reaction steps are: (i) partial hydrolysis of isocyanate caused by water traces, (ii) incomplete trimerization of isocyanate to give isocyanurate, and (iii) formation of oxazolidone and complete conversion of isocyanate. At the highest concentration of the soft macrodiepoxyde (PEGDGE), the AISOX resin is in the rubbery state at room temperature and shows an elastomeric behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43404.     

The mechanical and thermal properties of graphitic carbon nitride (g-C3N4)-based epoxy composites

Numerous ways to reinforce epoxy resin and improve its thermomechanical properties have been attempted using organic and inorganic nanoparticles. In this paper, graphitic carbon nitride (g-C₃N₄) nanoparticles were synthesized and used to improve the mechanical properties and thermal stability of epoxy composites. The g-C₃N₄ was synthesized from cheap melamine powder using a simple one-step thermal treatment, then was used to reinforce the resin at different weight percentages (wt%). X-ray diffraction, scanning electron microscopy (SEM), and Fourier infrared spectroscopy were used to characterize the g-C₃N₄ and ensure its successful synthesis by studying the changes in its crystal structure, morphology, and chemical structure. The filler was dispersed in the resin using a combination of ultrasonication and high shear mixing. The results showed that the mechanical properties were optimum when 0.5 wt% g-C₃N₄ was used. The tensile strength and fracture toughness of the resulting epoxy composite improved by 21.8% and 77.3%, respectively. SEM was used to investigate the morphologies of cracks formed in epoxy composite specimens after the tensile testing. The SEM micrographs of the fracture surface showed a transition from a brittle to a rough morphology, signifying the enhancement in the composites' toughness. Thermogravimetric analysis showed a good improvement in degradation temperature of up to 8.86% while dynamic mechanical analysis showed that the incorporation of g-C₃N₄ did not affect the material's glass transition temperature.     

Synthesis of biphenylated cyanate esters: Thermomechanical resin comparisons within two isomeric series

Three isomeric tetraaryl cyanate esters containing biphenyl moieties {bis‐[4‐(4′‐cyanatophenyl)phenyl]propane, 2,2‐bis‐[4‐(3′‐cyanatophenyl)phenyl]propane, and 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane} and three isomeric triaryl cyanate esters {2‐(4′‐hydroxyphenyl)‐2‐[4′‐(4‐hydroxyphenyl)phenyl]propane, 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(3‐hydroxyphenyl)phenyl]propane, and 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(2‐hydroxyphenyl)phenyl]propane} were synthesized from their corresponding bisphenols. The structures of the monomers were confirmed with IR and ¹H‐NMR spectroscopy. The curing behavior was investigated with differential scanning calorimetry. Cyanate esters were cured thermally in the absence of a catalyst and were characterized by dynamic mechanical analysis. The results were compared to the properties of commercial bisphenol A polycyanurate. Of the three tetraaryl isomers, 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane had the highest melting point, and its corresponding resin had the lowest glass‐transition temperature (T_g). The para isomer displayed the highest T_g value of the three novel tetraaryl resins. The triaryl dicyanate isomers were low‐melting solids, with the ortho and meta isomers existing as liquids at room temperature. The T_g value of the para‐triaryl isomer was the highest of the three triaryl isomers and was about the same as that of bisphenol A polycyanurate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and thermal stability of a novel cycloaliphatic epoxy resin system

A novel cycloaliphatic epoxy resin was synthesized from dicyclopentadiene, ethylene glycol, and nadic anhydride. The chemical structures of the resultant epoxy resin and its precursor were characterized with Fourier transform infrared spectroscopy, ¹H‐NMR, and mass spectrographic analyses. The thermal stability of the cured polymer was investigated with differential scanning calorimetry and thermogravimetric analysis. Compared with the thermal stability of the commercial cycloaliphatic epoxy resin 3,4‐epoxy cyclohexyl methyl‐3′,4′‐epoxy cyclohexyl carboxylate, a higher thermal stability for the cured polymer of the novel epoxy resin was observed. The results imply that the novel cycloaliphatic epoxy resin has good potential applications in electronic encapsulation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal properties and flame retardancy of polyglycidyloxypropyl silsesquioxane/layered titanate nanocomposites

Polyglycidyloxypropyl silsesquioxane, which has an excellent heat resistance, was combined with sheet‐like and spherical titanate as nano‐fillers. The burning property of the composites was related to the shape of the dispersed titanate. A burning test was carried out according to the UL‐94 test method. As a result, though the test specimen burned from one end to the other in the spherical titanate filled composite system, a fire extinguishing property was observed in the sheet‐like titanate filled composite system. The extinguishing time of the latter system classified V‐0 in the specification test. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyurethane‐modified epoxy resin: Solventless preparation and properties

A polyurethane‐modified epoxy resin system with potential as an underfill material in electronic packaging and its preparation procedure were studied. The procedure enabled the practical incorporation of an aliphatic polyurethane precursor, synthesized from poly(ethylene glycol) and hexamethylene diisocyanate without a solvent, as a precrosslinking agent into a conventional epoxy resin. With a stoichiometric quantity of the polyurethane precursor added to the epoxy (ca. 5 phr), the polyurethane‐modified epoxy resin, mixed with methylene dianiline, exhibited a 36% reduction in the contact angle with the epoxy–amine surface, a 31% reduction in the cure onset temperature versus the control epoxy system, and a viscosity within the processable range. The resultant amine‐cured thermosets, meanwhile, exhibited enhanced thermal stability, flexural strength, storage modulus, and adhesion strength at the expense of a 5% increase in the coefficient of thermal expansion. Exceeding the stoichiometric quantity of the polyurethane precursor, however, reduced the thermal stability and modulus but further increased the coefficient of thermal expansion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of organic/inorganic epoxy nanocomposites from poly(aminopropyl/phenyl)silsesquioxanes

Organic/inorganic epoxy nanocomposites containing diglycidyl ether of bisphenol A (DGEBA), 4‐methylhexahydrophthalic anhydride (MHHPA) and poly(aminopropyl/phenyl) silsesquioxanes (PAPPS) were prepared and characterized. PAPPS were synthesized via fluoride‐catalyzed cage formation from random‐structured poly(phenyl)silsesquioxane (PPS) and 3‐aminopropyltriethoxysilane (APTES) in tetrahydrofuran (THF) using tetrabutylammonium fluoride (TBAF) catalyst containing substantial water. The PPS/APTES stoichiometric ratios were varied. The FTIR, ¹H, solid‐state 29 Si‐NMR studies show that PAPPS probably consists of cages, partial cages, and some linear structures containing phenyl and aminopropyl functional groups. The amine content was determined by back titration and elemental analysis. In comparison with neat epoxy, incorporation of these materials can improve the resultant thermal stabilities, raise glass transition temperatures (T_gs), and reduce coefficients of thermal expansion (CTEs) of epoxy nanocomposites as confirmed by TG/DTA, DMA and TMA tests, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal and mechanical properties of tetra‐functional mesogenic type epoxy resin cured with aromatic amine

A novel tetra‐functional epoxy monomer with mesogenic groups was synthesized and characterized by ¹H‐NMR and FTIR. The synthesized epoxy monomer was cured with aromatic amine to improve the thermal property of epoxy/amine cured system. The glass transition temperature (T_g) and coefficient of thermal expansion (CTE) of the cured system were investigated by dynamic mechanical analysis and thermal mechanical analysis. The properties of the cured system were compared with the conventional bisphenol‐A type epoxy and mesogenic type epoxy system. The storage modulus of the tetra‐functional mesogenic epoxy cured systems showed the value of 0.96 GPa at 250 °C, and T_g‐less behavior was clearly observed. The cured system also showed a low CTE at temperatures above 150 °C without incorporation of inorganic components. These phenomena were achieved by suppression of the thermal motion of network chains by introduction of both mesogenic groups and branched structure to increase the cross linking density. The temperature dependency of the tensile property and thermal conductivity of the cured system was also investigated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46181.     

硅烷芳炔-硅氧烷芳炔嵌段共聚物的合成与表征

合成了不同链段长度的卤代硅氧烷,并用其与间二乙炔基苯格氏试剂反应,合成了两种硅烷芳炔-硅氧烷芳炔嵌段共聚物（SiO-b-PSA）,并制成碳纤维增强树脂复合材料。利用红外光谱（FT-IR）、核磁共振氢谱（¹H NMR）、凝胶渗透色谱（GPC）、旋转流变、差示扫描量热分析（DSC）、热失重分析（TGA）和悬梁臂冲击实验对共聚物及其复合材料的结构和性能进行表征。研究结果表明所合成的共聚物具有优良的耐热性和韧性,硅烷芳炔-硅氧烷芳炔嵌段共聚物在氮气气氛下的T_d5高于513℃,1000℃残留率高于78.9%,硅烷芳炔-硅氧烷芳炔嵌段共聚物/碳纤维复合材料的冲击强度高达（30.92±0.44） kJ·m^-2。     

笼形八聚(二甲基硅氧基)倍半硅氧烷的合成与表征

以四乙氧基硅烷〔Si(OEt)4〕与五水合四甲基氢氧化铵(Me4NOH.5H2O)为原料水解缩合得到笼形八聚四甲基铵硅酸盐([SiO1.5ONMe4]8),继而与二甲基氯硅烷〔HSi(CH3)2Cl〕反应,一锅法合成了笼形八聚(二甲基硅氧基)倍半硅氧烷(Q8M8H),最佳反应条件为:反应温度25℃,反应时间36 h,n〔Si(OEt)4〕∶n(Me4NOH.5H2O)∶n〔HSi(CH3)2Cl〕=1∶1∶4,产率80%。FTIR和NMR研究证明,所得产物为Q8M8H;SEM、EDS和XRD研究表明,所制备的Q8M8H具有较高的纯度和完整的晶型结构,属于单斜晶系,a=1.18 nm,b=1.52 nm,c=1.51nm,α=γ=90°,β=108°;TG表明,Q8M8H热失重5%时的温度为210℃。     

Fabrication and characterization of hydrophilic poly(ε‐caprolactone)/pluronic P123 electrospun fibers

Poly(ε‐caprolactone) (PCL) has been widely investigated for tissue engineering applications because of its good biocompatibility, biodegradability, and mechanical properties; however hydrophobic nature of PCL has been a colossal obstacle toward achieving scaffolds which offer satisfactory cell attachment and proliferation. To produce highly hydrophilic electrospun fibers, PCL was blended with pluronic P123 (P123) and the resulted electrospun scaffolds physiochemical characteristics such as fiber morphology, thermal behavior, crystalline structure, mechanical properties, and wettability were investigated. Moreover molecular dynamic (MD) simulation was assigned to evaluate the blended and neat PCL/water interactions. Presence of P123 at the surface of electrospun blended fibers was detected using ATR‐FTIR analysis. P123 effectiveness in improving the hydrophilicity of the scaffolds was demonstrated by water contact angel which experienced a sharp decrease from 132° corresponding to the neat PCL to almost 0° for all blended samples. Also a steady increase in water uptake ratio was observed for blended fibers as P123 content increased. The 90/10 blend ratio had the maximum tensile strength, elongation at break and crystallinity percentage. Therefore 90/10 blend ratio of PCL/P123 can balance the mechanical properties and bulk hydrophilicity of the resulted electrospun scaffold and would be a promising candidate for tissue engineering application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43345.     

The toughening effect and mechanism of styrene‐butadiene rubber nanoparticles for novolac resin

In this article, phenolic nanocomposites were prepared using styrene–butadiene rubber (SBR) nanoparticles with an average particle size of about 60 nm as the toughening agent. The mechanical and thermal properties of phenolic nanocomposites and the toughening mechanism were studied thoroughly. The results showed that when adding 2.5 wt % SBR nanoparticles, the notched impact strength of phenolic nanocomposites reached the maximum value and was increased by 52%, without sacrificing the flexural performance. Meanwhile, SBR nanoparticles had no significant effect on the thermal decomposition temperature of phenolic nanocomposites. The glass‐transition temperature (T_g) of phenolic nanocomposites shifted to a lower temperature accompanying with the increasing T_g of loaded SBR, which showed there was a certain compatibility between SBR nanoparticles and phenol‐formaldehyde resin (PF). Furthermore, the analysis of Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that there existed a weak chemical interaction between SBR nanoparticles and the PF matrix. The certain compatibility and weak chemical interaction promoted the formation of a transition layer and improved the interfacial bonding, which might be important reasons for the great enhancement of the toughness for phenolic nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41533.     

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     

Synthesis and characterizations of a latent polyhedral oligomeric silsequioxane‐containing catalyst and its application in polybenzoxazine resin

In this article, a novel latent curing agent, octa(paratoluenesulfonic acid ammomium salt) (OPAAS) polyhedral oligomeric silsequioxane was synthesized and used in modifying the polybenzoxazine/2,2′‐(1,3‐phenylene)‐bis(4,5‐dihydro‐oxazoles) (PBO) (PBZ/PBO) resin. The liberated octa(aminophenyl) silsesquioxane and paratoluenesulfonic acid can catalyze the ring‐opening reaction of benzoxazine (BZ) resin. The initial curing temperature (T_i), peak curing temperature (T_p) and the Enthalpy of the curing temperature had significantly decreased with respect to pristine BZ/PBO resin. When the OPAAS amount was 3 wt %, the peak curing temperature decreased from 233.7 to 218.2°C. Also, PBZ/PBO/OPAAS composites exhibited better storage modulus than pure PBZ/PBO resin. Meanwhile, PBZ/PBO/OPAAS composites are more thermally stable than PBZ/PBO resin. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Transparent epoxy resin material with excellent fire retardancy enabled by a P/N/S containing flame retardant

An epoxy resin (EP) with excellent fire retardancy, good transparency, and satisfactory thermal stability has been obtained by introducing a new N/P/S containing flame retardant (HBD) into EP composites. When the phosphorus content was 0.48 wt%, EP/HBD reached V-0 rating with the limiting oxygen index of 33.5%. The cone calorimeter test (CC) indicated that the incorporation of HBD resulted in 1.5 times increase in ignition time, a 50% decrease in the maximum of heat release rates, 40% reduction of total heat release, and 50.7% decrease in total smoke production compared with EP. Besides, the fire-resistant behavior of EP/8% HBD is much better than the EP materials modified by similar P/N/S flame retardants reported in literature. The fire-retardant mechanism of HBD on EP was also analyzed by Raman, scanning electron microscope, Py-GC/MS, and Fourier transform infrared spectroscopy. The results show that HBD plays an important role in the formation of a dense intumescent carbon layer and gas phase quenching.     

Ethynyl aromatic siliconhybridized resin: Synthesis,characterizations, and thermal properties

A novel silicon‐containing resin (ESA resin) was successfully synthesized by the condensation reaction of lithium arylacetylide with chlorosilane in high yields. The resin was characterized by the techniques of FTIR, ¹H‐NMR, ²⁹Si‐NMR, and gel permeation chromatography. Thermal cure process was monitored by DSC and FTIR methods. This resin could melt at around 100°C and thermally cured at 200–250°C with low exothermal enthalpy. Owing to the high aryl groups containing and the complete crosslinking of ethynyl groups, the cured ESA resin exhibited excellent thermal stability and high char yield. The decomposition temperature $T_{d_5}$ of the cured resin was at 510°C, and the residue yield at 900°C was 82.9% in N₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of novel poly(benzimidazopyrrolone amide)s containing pyridine moieties

A series of new poly(benzimidazopyrrolone amide) (PPA) copolymers were synthesized by a two‐step procedure, which was the solution polycondensation of a novel pyridine‐containing tetraamine with various aromatic dianhydrides at a room temperature and cyclization of the resulting prepolymers at a high temperature, respectively. The resulting prepolymers from the solution polycondensation, that is, poly(amide amino acid)s (PAAAs), had inherent viscosities of 0.82–0.91 dL/g; then, tough and flexible PPA films could be successfully prepared by the casting of the PAAA solutions onto a glass substrate followed by thermal curing with a program temperature procedure up to 350°C. The obtained PPA films exhibited not only excellent thermal properties with onset decomposition temperatures in the range 502–521°C, glass‐transition temperatures in the range 299–337°C, and residual weight retentions at 700°C in air of 29.1–34.8% but also good mechanical properties with tensile strengths of 102.1–115.9 MPa and elongations at break of 6.8–7.4%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biphenyl liquid crystal epoxy containing flexible chain: Synthesis and thermal properties

A biphenyl type liquid crystal epoxy (LCE) monomer 4,4′-di(2,3-epoxyhexyloxy)biphenyl (LCBP4) containing flexible chain was synthesized and the curing behavior was investigated using 4,4′-diaminodiphenylmethane (DDM) as the curing agent. The effect of curing condition on the formation of the liquid crystalline phase was examined. The cured samples show good mechanical properties and thermal stabilities. Moreover, the relationship between thermal conductivity and structure of liquid crystalline domain was also discussed. The samples show high thermal conductivity up to 0.28–0.31 W/(m*K), which is 1.5 times as high as that of conventional epoxy systems. In addition, thermal conductive filler, Al₂O₃, was introduced into LCBP4/DDM to obtain higher thermal conductive composites. When the content of Al₂O₃ was 80 wt%, the thermal conductivity of the composite reached to 1.86 W/(m*K), while that of diglycidyl ether of bisphenol A (Bis-A) epoxy resin/DDM/Al₂O₃ was 1.15 W/(m*K). Compared with Bis-A epoxy resin, the formation of liquid crystal domains in the cured LCE resin enhanced the thermal conductivity synergistically with the presence of Al₂O₃. Furthermore, the introduction of Al₂O₃ also slightly increased the thermal stabilities of the cured LCE.