Mechanical characterization and chemical resistances of cured unsaturated polyester resins modified with vinyl ester resins based on recycled poly(ethylene terephthalate)

Unsaturated polyester resin (UP) was prepared from glycolyzed oligomer of poly(ethylene terephthalate) (PET) waste based on diethylene glycol (DEG). New diacrylate and dimethacrylate vinyl ester resins prepared from glycolysis of PET with tetraethylene glycol were blended with UP to study the mechanical characteristics of the cured UP. The vinyl ester resins were used as crosslinking agents for unsaturated polyester resin diluted with styrene, using free‐radical initiator and accelerator. The mechanical properties of the cured UP resins were evaluated. The compressive properties of the cured UP/styrene resins in the presence of different vinyl ester concentrations were evaluated. Increasing the vinyl ester content led to a pronounced improvement in the compression strength. The chemical resistances of the cured resins were evaluated through hot water, solvents, acid, and alkali resistance measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3175–3182, 2007     

Synthesis of unsaturated polyester resins based on rosin acrylic acid adduct for coating applications

Unsaturated polyester, UP, resins were obtained by reacting the propylene or ethylene glycol, PG or EG, with different acrylopimaric adducts APA, maleic anhydride as a source of double bond, phthalic anhydride and adibic acid as dibasic acids. The molecular weights of UP were determined by end group analysis. The chemical structures of the resulting UP resins were confirmed by ¹H NMR analysis. The curing exotherm of UP, vinyl ester resins (VE) and styrene was evaluated at temperatures from 35 to 55 °C using free radical initiator and accelerator. The curing behaviors of cured UP resins with styrene were evaluated by DSC measurements. The prepared UP curable resins were evaluated in the field of steel coating by measuring their mechanical properties and chemical resistance.     

Compressive Properties and Curing Behaviour of Unsaturated Polyester Resins in the Presence of Vinyl Ester Resins Derived from Recycled Poly(ethylene terephthalate)

Poly(ethylene terephthalate) waste was depolymerised in the presence of tetraethylene glycol and manganese acetate as a catalyst, so as to produce oligomers. An epoxy resin was then prepared by the reaction of these oligomers with epichlorohydrin in presence of NaOH as a catalyst. New diacrylate and dimethacrylate vinylester resins were then synthesized by reaction of the terminal epoxy groups with acrylic and methacrylic acid in the presence of triphenyl phosphite as a catalyst. The chemical structures of the resulting vinyl ester resins were confirmed by ¹HNMR. The vinyl ester resins were used as crosslinking agents for unsaturated polyester resin diluted with styrene, using free radical initiator and accelerator. The curing behaviour of the unsaturated polyester resin, vinyl ester resins and styrene was evaluated at temperatures from 25 to 55 ^○C. The compression properties of the cured resins, having different vinyl ester contents and different cure temperatures, were evaluated. Increasing the cure temperature and the vinyl ester content led to a pronounced improvement in the compression strength and Young’s modulus.     

Curable resins based on recycled poly(ethylene terephthalate) for coating applications

Poly(ethylene terephthalate) waste was depolymerised in the presence of diethylene- or tetraethylene glycol and manganese acetate as a catalyst. An epoxy resin was then prepared by the reaction of these oligomers with epichlorohydrin in presence of NaOH as a catalyst. The produced oligomers were condensed with maleic anhydride and ethylene glycol to produce unsaturated polyester. The chemical structures of the resulting epoxy and unsaturated polyester resins were confirmed by ¹HNMR. The vinyl ester resins were used as cross-linking agents for unsaturated polyester resin diluted with styrene, using free radical initiator and accelerator. The 2-amino ethyl piprazine was used as hardener for epoxy resins. The curing behaviour of the unsaturated polyester resin, vinyl ester resins and styrene was evaluated at different temperatures ranged from 25 to 55 °C to calculate the curing activation energy of the system. The cured epoxy and unsaturated polyester resins were evaluated in coating application of steel.     

Thermal and mechanical behavior of unsaturated polyester [derived from poly(ethylene terephthalate) waste] and montmorillonite‐filled nanocomposites synthesized by in situ polymerization

Postconsumer poly(ethylene terephthalate) waste bottles were glycolyzed as precursors of unsaturated polyester resin (UPR) and their montmorillonite (MMT)‐filled nanocomposites. The glycolysis product (hydroxyl‐terminated oligomers) was converted into UPR with various acid contents. These resins were miscible with styrene and could be cured with peroxide initiators to produce thermosetting unsaturated polyester (UP). Nanocomposites composed of UP matrix and organically modified clay were prepared by in situ polymerization. These were characterized for thermal and dynamic mechanical properties. Transmission electron microscopy was also used to study the morphology at different length scales and showed the nanocomposites to be compromised of a random dispersion of intercalated/exfoliated aggregates throughout the matrix. With an increase in unsaturated acid content (for a fixed content of clay), the value of storage modulus varied from 2737 to 4423 MPa. The glass‐transition temperatures of these nanocomposites ranged from 54 to 78°C, and the crosslink density varied from 3.70 × 10⁵ to 5.72 × 10⁵ mol/m³. The X‐ray diffraction (XRD) of modified MMT exhibited a peak that vanished completely in the polymer nanocomposites. Thus, the XRD results apparently indicated a distortion of the platy layers of nanofiller in the UP nanocomposites. The nanocomposites showed higher modulus values (2737–4423 MPa) compared to the pristine polymer (2693 MPa). From thermogravimetric analysis, all of the nanocomposites were stable up to 200°C and showed a two‐stage degradation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225–250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water‐soluble crystallizable fraction and water‐insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and ¹H‐NMR analysis. Glycolysis product was used for synthesis of PET‐based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea‐formaldehyde and melamine‐formaldehyde resins for synthesis of epoxy ester–amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET‐based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino‐resin‐modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519–2525, 2015. © 2015 Society of Plastics Engineers     

Synthesis and characterization of poly(esteramide‐urethane) from linseed oil as anticorrosive coatings

Ethylene diamine polyesteramide (Ed‐PEA) was synthesized from N, N‐bis (2‐hydroxy ethyl) linseed oil fattyamide and ethylene diamine tetra acetic acid through condensation polymerization. It was further treated with toluylene 2,4‐diisocyanate (TDI) in different weight percentage to obtain urethane‐modified polyesteramide (Ed‐UPEA). The structural elucidation of Ed‐PEA and Ed‐UPEA were carried out by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopic techniques. Thermal studies of these resins were carried by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The coatings of urethane‐modified polyesteramide were prepared on mild steel strips and their anticorrosive behavior of in acid, alkali, water, and xylene were investigated. Thermal stability performance suggests that the system could be safely used upto 200°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Methacrylate/acrylate terminated derivatives of diglycidyl hexahydrophthalate: Synthesis,structural, and thermal characterization

Mono‐ or di(meth)acrylate‐terminated derivatives of diglycidyl hexahydrophthalate (ER) were prepared by reacting 1 : 1 or 1 : 2M ratio of ER and methacrylic acid or acrylic acid. These vinyl ester (VE) resins were characterized by determining epoxy equivalent weight, acid number, and molecular weight by gel permeation chromatography. Structural characterization was done by FTIR and ¹H NMR spectroscopy. In the ¹H NMR spectra of acrylate‐terminated VE resins, three proton resonance signals were observed in the region 5.8–6.4 ppm due to vinyl group while in methacrylate‐terminated VE resins only two proton resonance signals due to vinylidene protons were observed at 5.6–6.1 ppm. The Brookfield viscosity (room temperature (25 ± 2)°C) of these resins diluted with varying amounts of MMA was determined at 20 rpm. Curing behavior was monitored by determination of gel time and differential scanning calorimetry. An exothermic transition was observed in the DSC scans in the temperature range of (81–150)°C. Isothermal curing of MMA‐diluted VE resins containing AIBN as an initiator was done at 60°C for 2 h in N₂ atmosphere, and then heating for another 2 h in static air atmosphere. Thermal stability of isothermally cured resins in N₂ atmosphere was evaluated by thermogravimetric analysis. All cured resins decomposed above 310°C in single step. Thermal stability of the cured resins having acrylate end caps was marginally higher than the resins having methacrylate end groups. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Morphology and fracture properties of modified bisphenol A and novolac type vinyl ester resins

The morphology–toughness relationship of vinyl ester resins was studied as a function of their modification. Bisphenol A based and novolac‐based vinyl ester resins were modified by a star‐shaped polyether polymer with vinyl and hydroxyl functionalities and/or by a polyisocyanate. The polyisocyanate‐containing systems were termed vinyl ester/urethane hybrids. The morphology of the crosslinked resins was studied with dynamic mechanical thermal analysis and atomic force microscopy with ion‐eroded specimens and discussed. The toughness of the crosslinked resins was assessed by the linear elastic fracture mechanics with compact tension specimens. The fracture toughness and energy changed fairly linearly as functions of M_c and M_c^0.5, respectively, where M_c is the mean molecular mass between crosslinks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4012–4022, 2006     

Use of allyl‐functional benzoxazine monomers as replacement for styrene in vinyl ester resins

New vinyl ester systems are prepared using allyl‐functional benzoxazine monomers, 3‐allyl‐6‐methyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine (pC‐ala) or bis(3‐allyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazin‐6‐yl)methane (BF‐ala), as reactive diluents for vinyl ester resins derived from an epoxy resin, diglycidyl ether of bisphenol A, instead of using styrene. Different initiators are used to investigate the copolymerization of allyl function from pC‐ala with vinyl function from vinyl ester resin prepolymer. The temperature dependence of viscosity is studied to demonstrate the retention of processability of the new vinyl ester resins. Dynamic mechanical and thermogravimetric analyses are used to investigate the dynamic mechanical properties and thermal stability of the new resins. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of novel polyurethanes based on aminolysis of poly(ethylene terephthalate) wastes,and evaluation of their thermal and mechanical properties

BACKGROUND: Much research is currently directed towards recycling post‐consumer poly(ethylene terephthalate) (PET) products for both environmental and economic reasons. Aminolysis of PET wastes using different amines, such as allylamine, morpholine, hydrazine and polyamines, leads to different reaction products as diamides of terephthalic acid, which do not possess any potential for further chemical reactions. In the past, the use of ethanolamine has been investigated for the aminolytic degradation of PET waste in the presence of different simple chemicals such as sodium acetate as catalysts. The product obtained, bis(2‐hydroxyethylene) terephthalamide (BHETA), has potential for further reactions to obtain useful products. Nevertheless, there has been no report on using recycled BHETA from PET to synthesize polyurethanes. RESULTS: In this research the product of aminolysis of PET waste, BHETA, was prepared. Then novel polyurethanes were synthesized based on the BHETA prepared, 1,4‐butanediol, ether‐type polyol and various molar ratios of hexamethylene diisocyanate. To evaluate the effect of BHETA, the properties of the polyurethanes without and with BHETA were compared. Fourier transform infrared spectra, thermal transitions, degradation, swelling ratio and chemical resistance of the synthesized polyurethanes were investigated. Also, the polyurethanes were applied as adhesives on various substrates. Comparison of the maximum bond strength of the synthesized polyurethane to that of commercial adhesives shows an about 2.2‐fold increase. CONCLUSION: It is possible to synthesize new polyurethanes with interesting properties using BHETA as an aminolysis product of PET waste. These kinds of materials have potential for many applications, such as adhesives and coatings. Copyright © 2008 Society of Chemical Industry     

Mass transfer study of chlorine dioxide gas through polymeric packaging materials

The mass transfer profile (permeability, diffusion, and solubility coefficients) of chlorine dioxide (ClO₂), a strong oxidizing agent that is used in food and pharmaceutical packaging, was determined through various common polymeric packaging materials. A continuous system for measuring permeation of ClO₂, using an electrochemical detector, was developed. It was observed that biaxially‐oriented poly(propylene), poly(ethylene terephthalate), poly(lactic acid), nylon, and a multilayer structure of ethylene vinyl acetate and ethylene vinyl alcohol were better barriers for gaseous ClO₂, as compared to polyethylene, poly(vinyl chloride), and polystyrene. The activation energies of permeation for ClO₂ through poly(ethylene terephthalate) and poly(lactic acid) were determined to be 51.05 ± 4.35 and 129.03 ± 2.82 kJ/mol, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, , 2009     

Toughening of unsaturated polyester resins with core–shell rubbers

The effects of core–shell rubbers (CSRs) as tougheners on the fracture properties of unsaturated polyester (UP) resins during curing at 110°C are investigated. CSRs were synthesized by two‐stage soapless emulsion polymerizations; the soft core was made from rubbery poly(n‐butyl acrylate), whereas the hard shell was made from methyl methacrylate, ethylene glycol dimethacrylate, and various concentrations of glycidyl methacrylate. Depending on the content of glycidyl methacrylate in the CSR shell and the amount of CSR added to the UP, the fracture properties of the CSR‐toughened UP resins varied. The experimental results are explained by an integrated approach of measurements of the static phase characteristics of a styrene/UP/CSR system, the reaction kinetics, the cured sample morphology, the glass‐transition temperatures, and the fracture toughness with differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and dynamic mechanical analysis. Finally, the toughening mechanism for the CSR‐toughened UP resins is also explored. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of poly(vinyl acetate) and poly(vinyl chloride‐ co‐vinyl acetate) low‐profile additives on properties of cured unsaturated polyester resins. I. Volume shrinkage characteristics and internal pigmentability

Three series of self‐synthesized poly(vinyl acetate)‐based low‐profile additives (LPAs) with different chemical structures and molecular weights, including poly(vinyl acetate), poly(vinyl chloride‐co‐vinyl acetate), and poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride), were studied. Their effects on the volume shrinkage characteristics and internal pigmentability for low‐shrink unsaturated polyester (UP) resins during cure were investigated. The experimental results were examined with an integrated approach involving measurements of the static phase characteristics of the ternary styrene/UP/LPA system, the reaction kinetics, the cured sample morphology, and microvoid formation by using differential scanning calorimetry, scanning electron microscopy, optical microscopy, and image analysis. Based on the Takayanagi mechanical model, factors leading to both good volume shrinkage control and acceptable internal pigmentability for the molded parts were explored. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3336–3346, 2003     

A novel flame retardant UV‐curable vinyl ester resin monomer based on industrial dipentene: Preparation,characterization, and properties

A novel bio‐based and flame‐retardant UV‐curable vinyl ester resin (VER) monomer named Diglycidyl ester of maleinized dipentene modified with dibutyphosphate and methacrylic anhydride (MDDMD) was synthesized from industrial dipentene via Diels‐Alder reaction, glycidylation, epoxy ring‐opening reaction, and esterification. Its chemical structures were characterized by Fourier transform infrared (FTIR) analysis and proton nuclear magnetic resonance (¹H‐NMR). In order to improve its flexibility, we prepared a series of copolymers under UV light radiation by mixing it with certain proportions of poly(ethylene glycol) dimethacrylate‐200 (PEGDMA‐200) which contained flexible groups. Their tensile property, curing degrees (CD), hardness, limiting oxygen index (LOI), dynamic mechanical thermal properties, and thermostability were all investigated. The cured mixed resins have a relatively high tensile strength of 10.05 MPa and curing degrees up to 92.5%. Both hardness (range: 50 to 23 HD) and LOI (range: 22.8% to 24.4%) of cured resins are improved with the increase of MDDMD content. Dynamic mechanical analysis (DMA) shows that their glass transition temperatures rise with the increase of MDDMD content. Thermogravimetric analysis (TGA) shows that the thermal stability of cured resins is enhanced with the increase of PEGDMA‐200 content, as the main thermal initial decomposition temperatures are all above 260 °C and char yield at 800 °C are above 18.10%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44084.     

Preparation,characterization, and improvement of hollow epoxy particle‐toughened vinyl ester composites for high‐end applications

Spherical hollow epoxy particles (HEPs) that can serve as advanced reinforcing fillers for vinyl ester thermosets were prepared using the water‐based emulsion method. The HEP fillers were incorporated into the vinyl ester matrices at different loading amounts, ranging from 0 to 9 wt %, to reinforce and toughen the vinyl ester composite. The optimum mechanical properties of the HEP‐toughened epoxy composite can be achieved by the addition of 5 wt % HEP filler into the vinyl ester matrices. The toughening and strengthening of the epoxy composites involved the interlocking of vinyl ester resins into the pore regions on the HEP fillers. The toughening and interlocking mechanisms of HEP‐toughened vinyl ester composites were also proposed and discussed. The addition of HEP fillers into vinyl ester matrices increased the glass transition temperature (T_g) and thermal stability of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhanced interfacial adhesion of carbon fibers to vinyl ester resin using poly(arylene ether phosphine oxide) coatings as adhesion promoters

Poly(arylene ether phosphine oxide)s (PEPO) were prepared and utilized to coat carbon fibers to enhance the interfacial adhesion with vinyl ester resins. For comparison, poly(arylene ether sulfone) (PES), Udel^® P-1700, and Ultem^® 1000 were also used. The interfacial shear strength (IFSS) of thermoplastic polymer-coated fibers was measured via microbond pull-out tests. The interfacial adhesion between thermoplastics and as-received carbon fibers was also measured in order to investigate the adhesion mechanism. Thermoplastic polymer-coated fibers exhibited a higher IFSS than the as-received fibers with vinyl ester resin, and with thermoplastic polymers. PEPO-coated fibers showed the highest IFSS, followed by Udel^®, PES, and Ultem^®-coated fibers. The high IFSS obtained with PEPO coating could be attributed to the phosphine oxide moiety, which provided a strong interaction with functional groups in the vinyl ester resin and also on carbon fibers. A diffusion study revealed the formation of a clear interphase not only between PEPO and the vinyl ester resin, but also between Udel^® (PES or Ultem^®) and the vinyl ester resin, although the morphology of the two interphases differed greatly.     

The effect of water activity on the sorption and diffusion of water in thermosets based on polyester,vinyl ester,and novolac resins

In this work, the transport properties of water in various thermoset resins typically used for fiber‐reinforced plastic process equipment (vinyl ester, novolac, bisphenol‐A‐epoxy‐based polyester, and urethane‐modified vinyl ester) were systematically studied with a focus on the effects of water activity. Sorption and desorption studies were carried out in aqueous solutions (water activity = 0.78–1) with different salts (NaCl, MgCl₂, Na₂SO₄, and KCl) and one nonionic substance (sucrose) within the temperature interval 65–95°C. It was found that the water concentration in thermoset resins with different chemical structures could be predicted from the water activity, regardless of the actual solute (salt or sucrose) in the aqueous solution. The water quasi‐equilibrium concentration decreased with decreasing water activity, whereas the average diffusion coefficient was considered to be independent of water activity in the studied water activity range. A relationship, based on a power law fit, was established describing the water concentration as a function of the water activity and the concentration of pure water. The relationship was independent of resin chemistry and temperature. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Rheological Behavior of Vinyl Ester Resin

Vinyl ester resins with varied acid values (11, 22, 32, 38, and 48 mg KOH/g solid) were prepared by reacting epoxy-novolac resin with methacrylic acid. The rheological behavior of these synthesized vinyl ester resin (VER) samples containing styrene as reactive diluent was studied using a Haake Rotovisco RV 20 viscometer. The apparent viscosity was found to be inversely proportional to the square root of the acid value in the temperature range of 25–40°C and at shear rates ranging from 100–800 sec^?1. The zero-shear viscosity of these VER samples containing styrene (40% w/w) as reactive diluent decreased linearly with temperature. The activation energies for flow at constant shear stress (25–100 Pa) for a particular sample were found to be constant. The activation energy at constant shear rate decreases with the increase in the shear rate (50–400 sec^?1). The activation energy at constant shear rate and shear stress decreased with the increase in the acid value. The viscosity of vinyl ester resin containing styrene as reactive diluent decreased almost 50 times with the increase in the concentration of reactive diluent from 30% to 100% (w/w of the resin).     

Glass‐transition temperature based on dynamic mechanical thermal analysis techniques as an indicator of the adhesive performance of vinyl ester resin

Vinyl ester resins are being used extensively as matrices in fiber‐reinforced polymer composite materials, but their use as a structural adhesive has been limited. Initial studies investigating the durability of a vinyl ester as a wood adhesive showed unsatisfactory performance in comparison with other adhesives. In this work, the glass‐transition temperatures (T_g's) of a vinyl ester and a E‐glass/vinyl ester composite material, fabricated by the Composites Pressure Resin Infusion System, were determined with dynamic mechanical thermal analysis. The results indicated that the resin cured under ambient conditions had a much lower T_g (～60°C) than the postcured material (～107°C). This suggested undercuring, that is, incomplete crosslinking, of the resin when it was cured at room temperature. E‐glass/vinyl ester samples, however, showed virtually no difference in T_g between room‐temperature‐cured and postcured samples. The exact reasons for this are not currently known but are thought to be both mechanical and chemical in nature. On the basis of the findings presented in this article, it can be concluded that if this vinyl ester resin is to be used as a structural adhesive, postcuring or formulation to ensure a high degree of crosslinking under ambient conditions is necessary. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2221–2229, 2005