Preparation and characterization of an epoxy resin modified by a combination of MDI‐based polyurethane and montmorillonite

The present work investigates the modification of epoxy resin by using a combination of nanoclay (montmorillonite—Cloisite 30B) and a liquid polymeric modifier (polyurethane). Polyurethane was obtained from 4,4′‐diphenylmethane diisocyanate and polydiols with different molecular weight: polyethylene glycol (PEG 400) and polyoxypropylene diols with molecular weight 1000 g/mol and 2000 g/mol. The impact strength, the critical stress intensity factor as well as the flexural strength were evaluated as functions of modifiers content. The obtained results showed that hybrid composites exhibit enhanced mechanical properties without significant changes of the glass transition temperature. FTIR analysis showed that chemical reactions took place between the hydroxyl groups of epoxy resin and the isocyanate groups of polyurethane, explaining an improvement of the mechanical properties of epoxy resin. However, XRD results demonstrated the formation of an exfoliated structure for the hybrid compositions with both polyurethane and montmorillonite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of various polyurethanes on the mechanical and structural properties of an epoxy resin

Polyurethanes (PURs) obtained from poly(ethylene glycol)s (PEGs) and polyoxypropylene diols (POPDs) of different molecular weights were used as modifiers of diglycidyl ether of bisphenol A. The impact strength, critical stress intensity factor, stress, and strain during three‐point bending were measured as functions of the PUR type and content. Scanning electron microscopy and infrared spectroscopy were employed for the structure and morphology analysis. The addition of 10 or 15% PUR to the epoxy resin resulted in the most enhanced mechanical properties. However, a modifier loading higher than 15% led to decreases in the impact strength, critical stress intensity factor, and flexural strength. Moreover, shorter flexible segments in PUR obtained from lower molecular weight PEG led to stronger composites, whereas composites containing PUR based on lower molecular weight POPD with long flexible segments exhibited higher toughness and strain at break and lower impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Graft‐interpenetrating polymer networks of epoxy with polyurethanes derived from poly(ethyleneterephthalate) waste

Polyester polyurethanes derived from poly(ethyleneterephthalate) (PET) glycolysates were blended with epoxy to form graft‐interpenetrating networks (IPNs) with improved mechanical properties. Microwave‐assisted glycolytic depolymerization of PET was performed in the presence of polyethylene glycols of different molecular weights (600–1500). The resultant hydroxyl terminated polyester was used for synthesis of polyurethane prepolymer which was subsequently reacted with epoxy resin to generate grafted structures. The epoxy‐polyurethane blend was cured with triethylene tetramine under ambient conditions to result in graft IPNs. Blending resulted in an improvement in the mechanical properties, the extent of which was found to be dependant both on the amount as well as molecular weight of PET‐based polyurethane employed. Maximum improvement was observed in epoxy blends prepared with polyurethane (PU1000) at a loading of 10% w/w which resulted in 61% increase in tensile strength and 212% increase in impact strength. The extent of toughening was quantified by flexural studies under single edge notch bending (SENB) mode. In comparison to the unmodified epoxy, the Mode I fracture toughness (K_IC) and fracture energy (G_IC) increased by ～45% and ～184%, respectively. The underlying toughening mechanisms were identified by fractographic analysis, which generated evidence of rubber cavitation, microcracking, and crack path deflection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40490.     

聚氨酯改性环氧树脂的研究

用聚乙二醇和甲苯-2,4-二异氰酸酯(TD I)为原料合成了端基为羟基的聚氨酯低聚物,并用其改性环氧树脂。研究了聚氨酯含量、不同原料配比、不同分子量的聚乙二醇对环氧树脂的力学性能的影响。结果表明,添加了12%端羟基聚氨酯低聚物的环氧树脂比未改性的环氧树脂的拉伸强度和冲击强度分别提高了126%和192%,对环氧树脂有良好的增韧、增强效果。并用扫描电镜(SEM)观察了冲击断面的形貌。     

Mode I and Mode II delamination resistance and mechanical properties of woven glass/epoxy–PU IPN composites

The effect of polyurethane on the mechanical properties and Mode I and Mode II interlaminar fracture toughness of glass/epoxy composites were studied. Polyurethanes (PU) synthesized using polyols and toluene diisocyanate were employed as modifier for epoxy resin by forming interpenetrating polymer network. The PU/Epoxy IPN was used as matrix material for GFRP. PU modified epoxy composite laminates having varying PU contents were prepared. The effect of PU content on the mechanical properties like interlaminar fracture toughness (Mode I, G_1c and Mode II, G_IIc), tensile strength, flexural strength, and Izod impact strength were studied. The morphological studies were conducted on the fractured surface of the composite specimen by scanning electron microscopy (SEM). Tensile strength, flexural strength, and impact strength of PU‐modified epoxy composite laminates were found to increase inline with interlaminar fracture toughness (G_1c and G_IIc) with increasing PU content to a certain limit and then it was found to decrease with increase in PU content. It was observed that toughening of epoxy with PU increases the Mode I and Mode II delamination toughness up to 17 and 120% higher than that of untoughened composite specimen, respectively. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Thermomechanical properties of arylamine‐based benzoxazine resins alloyed with epoxy resin

Effects of epoxy resin on various arylamine‐based benzoxazine resins, i.e., aniline (BA‐a), m‐toluidine (BA‐mt), and 3,5‐xylidine (BA‐35x), have been investigated. Processing windows of BA‐35x, BA‐mt, and BA‐a were found to be widened with the amount of the epoxy. Gel points of benzoxazine‐epoxy resin mixtures can be predicted by an Arrhenius equation, e.g., gel time of BA‐35x and epoxy mixture at 70:30 mass ratio can be estimated by t_gel = 0.7012 × 10^?7 exp (10.563/T). Glass transition temperature (T_g) of BA‐a and BA‐mt alloyed with epoxy exhibited a synergistic behavior with the maximum T_g value at the benzoxazine‐epoxy composition of 80:20 mass ratio. However, in the BA‐35x and epoxy mixture, the decreasing trend in T_g from 241°C to 223°C with an addition of epoxy was observed. Furthermore, flexural strength and strain‐at‐break of those alloys were found to increase with increasing amount of the epoxy while modulus increased with the polybenzoxazine mass fraction. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Application of a series of novel chain-extended ureas as latent-curing agents and toughening modifiers for epoxy resin

A series of novel chain-extended ureas (U_i) containing poly(ethylene glycol) (PEG) spacers with different molecular weights were synthesized and the reactive mechanism, reactive activity, impact strength, dynamic mechanical behavior, morphology, and storage properties of the epoxy resin/chain-extended urea system were studied. Experimental results revealed that the impact strength of the epoxy resin modified with chain-extended urea containing a PEG flexible spacer with molecular weight of 1000 is 9.5 times higher than that of the epoxy resin/dicyandiamide system. Results also show that the molecular weight of PEG in chain-extended ureas hardly has any influence on the reactive activity of the chain-extended ureas. The storage life of the epoxy resin/U_i system can be delayed to 38 h at 50°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 339–347, 1998     

聚醚对环氧-聚氨酯互穿网络制备的影响

研究了聚丙二醇醚（PPG）、聚四氢呋喃醚及二者的共聚醚分别形成的聚氨酯预聚体与低分子羟基化合物和环氧树脂的反应性,应用聚氨酯对环氧进行了IPN改性,测试了其红外光谱和冲击强度.结果说明：聚四氢呋喃醚型聚氨酯的反应活性太大,不适宜用于环氧树脂的IPN改性 聚丙二醇醚及其与聚四氢呋喃的共聚醚型的聚氨酯反应活性适中,适合作为环氧IPN改性的聚氨酯组分.采用PPG型聚氨酯对环氧进行了IPN改性,改性后的环氧体系冲击强度大大提高.     

Effects of TDI and FA‐703 on physico‐mechanical properties of polyurethane dispersion

A series of water dispersion polyurethanes dispersions (PUDs) were prepared by polyaddition reaction using isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), and triol (trade name FA‐703). Various formulations were designed to investigate the effects of process variables such as TDI and FA‐703 on the physico‐mechanical properties of PUD. IR spectroscopy was used to check the end of polymerization reaction and characterization of polymer. Evolution of the particle size distribution, contact angle, T_g, molecular weight, viscosity, and mechanical properties of the emulsion‐cast films were significantly affected by variable content of TDI and FA‐703. Average particle size of the prepared polyurethane emulsions and contact angle decrease with increase of content of FA‐703 and TDI. Molecular weight, T_g, tensile strength, tear strength, hardness, viscosity and elongation at break increase with increase of content of FA‐703 and TDI. The increase of molecular weight, tensile strength, tear strength and elongation at break properties are interpreted in terms of increasing hard segments, chain flexibility, and phase separation in high content of FA‐703 and TDI‐based polyurethane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

环氧树脂改性高固含量水性聚氨酯乳液的制备

以聚己内酯二醇(PCL)、聚丙二醇(PPG)、六亚甲基二异氰酸酯(HDI)、异佛尔酮二异氰酸酯(IPDI)、环氧树脂E51、二羟甲基丙酸(DMPA)、1,6-己二醇(HDO)和50％乙二胺基乙磺酸钠水溶液(A-95)为主要原料,合成了一系列环氧树脂改性的水性聚氨酯(WPU)乳液.采用FT-IR、DSC及力学性能等测试手...     

Synthesis and characterization of fluorinated poly(etherimide)s toughening for carbon fiber‐reinforced epoxy composites

Novel‐fluorinated poly(etherimide)s (FPEIs) with controlled molecular weights were synthesized and characterized, which were used to toughen epoxy resins (EP/FPEI) and carbon fiber‐reinforced epoxy composites (CF/EP/FPEI). Experimental results indicated that the FPEIs possessed outstanding solubility, thermal, and mechanical properties. The thermally cured EP/FPEI resin showed obviously improved toughness with impact strength of 21.1 kJ/m² and elongation at break of 4.6%, respectively. The EP/FPEI resin also showed outstanding mechanical strength with tensile strength of 91.5 MPa and flexural strength of 141.5 MPa, respectively. The mechanical moduli and thermal property of epoxy resins were not affected by blending with FPEIs. Furthermore, CF/EP/FPEI composite exhibited significantly improved toughness with Mode I interlaminar fracture toughness (G_IC) of 899.4 J/m² and Mode II interlaminar fracture toughness (G_IIC) of 1017.8 J/m², respectively. Flexural properties and interlaminar shear strength of the composite were slightly increased after toughening. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Effect of reactive poly(ethylene glycol) flexible chains on curing kinetics and impact properties of bisphenol‐a glycidyl ether epoxy

Bisphenol‐A glycidyl ether epoxy resin was modified using reactive poly(ethylene glycol) (PEO). Dynamic mechanical analysis showed that introducing PEO chains into the structure of the epoxy resin increased the mobility of the molecular segments of the epoxy network. Impact strength was improved with the addition of PEO at both room (RT) and cryogenic (CT, 77 K) temperature. The curing kinetics of the modified epoxy resin with polyoxypropylene diamines was examined by differential scanning calorimetry (DSC). Curing kinetic parameters were determined from nonisothermal DSC curves. Kinetic analysis suggested that the two‐parameter autocatalytic model suitably describes the kinetics of the curing reaction. Increasing the reactive PEO content decreased the heat flow of curing with little effect on activation energy (E_a), pre‐exponential factor (A), or reaction order (m and n). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006     

Effects of amino‐functionalized carbon nanotubes on the properties of amine‐terminated butadiene–acrylonitrile rubber‐toughened epoxy resins

Amino‐functionalized multiwalled carbon nanotubes (MWCNT‐NH₂s) as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA) toughened with amine‐terminated butadiene–acrylonitrile (ATBN). The curing kinetics, glass‐transition temperature (T_g), thermal stability, mechanical properties, and morphology of DGEBA/ATBN/MWCNT‐NH₂ nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, a universal test machine, and scanning electron microscopy. DSC dynamic kinetic studies showed that the addition of MWCNT‐NH₂s accelerated the curing reaction of the ATBN‐toughened epoxy resin. DSC results revealed that the T_g of the rubber‐toughened epoxy nanocomposites decreased nearly 10°C with 2 wt % MWCNT‐NH₂s. The thermogravimetric results show that the addition of MWCNT‐NH₂s enhanced the thermal stability of the ATBN‐toughened epoxy resin. The tensile strength, flexural strength, and flexural modulus of the DGEBA/ATBN/MWCNT‐NH₂ nanocomposites increased increasing MWCNT‐NH₂ contents, whereas the addition of the MWCNT‐NH₂s slightly decreased the elongation at break of the rubber‐toughened epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40472.     

Effects of Epoxy Resin on Gelcasting Process and Mechanical Properties of Alumina Ceramics

A gelling system based on the polymerization of epoxy resin ethylene glycol diglycidyl ether (EGDGE) and 3,3′‐Diaminodipropylamine (DPTA) was developed for gelcasting alumina ceramics. The gelation process of 50 vol% alumina‐epoxy resin suspensions were investigated in accordance with the change in temperature and epoxy resin concentration. The activation energy E_a of polymerization reaction was 63.76 kJ/mol and no significant gelation was observed at 25°C during the test for 50 vol% Al₂O₃ suspensions with 10 wt% EGDGE. With the increase in EGDGE concentration, Al₂O₃ green bodies exhibited higher relative density, flexural strength, and Weibull modulus, reaching 64.4%, 41.03 MPa, and 12.51, respectively, when EGDGE concentration was 20 wt%. However, for sintered Al₂O₃ bodies, the highest characteristic strength and Weibull modulus were obtained for 15 wt% EGDGE concentration, reaching 367.57 MPa and 14.52, respectively.     

Tetrafunctional aliphatic epoxy I. Synthesis and characterization

A low viscosity tetrafunctional epoxy resin was synthesized by reacting amino-terminated polydimethylsiloxane with epichlorohydrin followed by dehydrohalogenation. The synthesized tetrafunctional aliphatic epoxy resin had an epoxy equivalent weight of 382, M_n of 1492, M_w of 2296, and a viscosity of 4.2 poise at 25°C. The chemical structure of the tetrafunctional aliphatic epoxy resin was studied by gel permeation chromatography (GPC), Fourier transform infrared spectra (FTIR), and ¹H-NMR spectra. Results showed the tetrafunctional aliphatic epoxy-blended aromatic epoxy resin possessed high impact strength and flexural strength. SEM photographs were investigated to study the compatibility of the blended epoxy system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 51–58, 1998     

Thermal stability of polyurethane elastomers before and after UV irradiation

In this work, we investigated the thermal degradation behavior of segmented polyurethane (PUR) elastomers before and after UV irradiation. The thermal degradation of PUR elastomers was studied over the temperature range of 25–600°C in an atmosphere of nitrogen using thermal gravimetric analysis (TGA). Four series of PUR elastomers derived from poly(oxytetramethylene)glycol (PTMO) of 1000 and 2000 molecular weight and poly(caprolactone glycol) (PCL) of 1250 molecular weight, 4,4′‐diphenylmethane diisocyanate (MDI), and 4,4′‐dicyclohexylmethane diisocyanate (H₁₂MDI) and 1,4‐butanediol as an chain extender were synthesized by the prepolymer method. The derivative thermogravimetric (DTG) peaks observed in the experiments indicated that PUR elastomers degraded through two steps. We attributed the first step to degradation of the hard segment. The second degradation step could be ascribed to degradation of the soft segment. We found that the PUR elastomers based on poly(ester polyol) and aromatic diisocyanate exhibit better thermal stability than that of PUR elastomers based on the poly(ether polyol) soft segment in both steps of degradation. The thermal degradation is more prevalent in PUR elastomers based on cycloaliphatic diisocyanate. The higher values of the temperature of initial decomposition (Tⁱ) indicate a higher thermal stability of UV‐exposed elastomers on the beginning of degradation. This may be due to the formation of a crosslinking structure in the presence of UV irradiation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 864–873, 2001     

Toughening of aromatic diamine-cured trifunctional epoxy resins by modification with N-phenylmaleimide–styrene copolymers containing pendant p-hydroxyphenyl groups

N-Phenylmaleimide (PMI)–N-(p-hydroxy)phenylmaleimide (HPMI)–styrene (St) terpolymers (HPMS), containing pendant p-hydroxyphenyl (HP) groups, were prepared and used to improve the toughness of triglycidyl aminocresol epoxy resin cured with p,p′-diaminodiphenyl sulfone. HPMS was effective as a modifier for the toughening of the epoxy resin. When using 15 wt % of HPMS (1.0 mol % HP unit, M_w 129,000), the fracture toughness (K_IC) for the modified resin increased 190% with a medium loss of flexural strength. The toughening of epoxies could be attained because of the cocontinuous phase structure of the modified resins. The decrease in flexural strength was suppressed to some extent by introducing a functional group into the modifier. The toughening mechanism was discussed in terms of the morphological behavior of the modified epoxy resin system. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of chlorinated soy oil based epoxy resin/glass fiber composites

Composites with good toughness properties were prepared from chemically modified soy epoxy resin and glass fiber without additional petroleum based toughening agent. Chlorinated soy epoxy (CSE) resin was prepared from soybean oil. The CSE was characterised by spectral, and titration method. The prepared CSE was blended with commercial epoxy resin in different ratios and cured at 85°C for 3 h, and post cured at 225°C for 2 h using m‐phenylene diamine (MPDA) as curing agent. The cure temperatures of epoxy/CSE/MPDA with different compositions were found to be in the range of (151.2–187.5°C). The composite laminates were fabricated using epoxy /CSE/MPDA‐glass fiber at different compositions. The mechanical properties such as tensile strength (248–299 MPa), tensile modulus (2.4–3.4 GPa), flexural strength (346–379 MPa), flexural modulus (6.3–7.8 GPa) and impact strength (29.7–34.2) were determined. The impact strength increased with the increase in the CSE content. The interlaminor fracture toughness (G_IC) values also increased from 0.6953 KJ/m² for neat epoxy resin to 0.9514 KJ/m² for 15%CSE epoxy‐modified system. Thermogravimetric studies reveal that the thermal stability of the neat epoxy resin was decreased by incorporation of CSE. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers