Unsaturated Polyester Resins Obtained from Glycolysis Products of Waste PET

Abstract

Waste polyethylene terephthalate (PET) flakes were depolymerized by using ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), and triethylene glycol (TEG) in the presence of zinc acetate as catalyst. All glycolysis products were reacted with maleic anhydride and mixed with styrene monomer to get unsaturated polyester (UP) resins. Molecular weights of all synthesized UP resins were determined by end-group analysis. The curing characteristics such as gel time and maximum curing temperatures, and mechanical properties such as hardness, tensile strength, and elastic module of these resins were investigated. The waste PET resins were compared with the reference resins prepared with the same glycols and the properties of the resins were found to be compatible with the properties of the reference resins.     

Study of the behavior of polyester concretes containing ionomers as curing agents

Polyester concretes have been used in constructions for more than 20 years. This type of polymer concrete can advantageously replace traditional Portland concrete in situations that require fast consolidation of the material. Otherwise, polyester concretes are usually more expensive than Portland concretes. Part of the high cost of the polyester concretes is due to the fact that the aggregates used in the formulation of the concretes need to be dried prior to their incorporation into the polymer matrix. In this work, the use of different curing systems (methacrylic acid and maleic anhydride) was investigated to test the hypothesis that the introduction of acid functionalities into unsaturated polyesters based on isophthalic acid could both restrict the detrimental effect of moisture in the curing process and also improve interfacial interactions even in polyester concretes containing wet aggregates. In this work, as there was no search for ways to reduce cost of polyester concretes and also to contribute to the environmental preservation, unsaturated polyesters were synthesized from PET bottles and tested in the fabrication of concretes by reacting them with a conventional curing agent (styrene). Gel permeation chromatography, infrared spectroscopy, and electron microscopy were used to monitor and analyze the production of unsaturated polyester resins and concretes. Mechanical properties were also evaluated by compression tests. Results showed that methacrylic acid and maleic anhydride, when used as curing agents, led to the production of polyester concretes having higher mechanical properties in both dry and wet states than conventional polyester (based on isophthalic acid) concretes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Physical properties of unsaturated polyester resin from glycolyzed pet fabrics

Physical properties of unsaturated polyester resins (UPE resins) prepared from glycolyzed poly (ethylene terephthalate) (PET) and PET/cotton blended fabrics were investigated. Initially, PET and PET/cotton blended fabrics were chemically recycled by glycolysis. The depolymerizations were carried out in propylene glycol with the presence of zinc acetate as a catalyst. The reaction time was varied at 4, 6, and 8 h. The glycolyzed products were then esterified using maleic anhydride to obtain UPE resins. The prepared resins were cured using styrene monomer, methyl ethyl ketone peroxide, and cobalt octoate as a crosslinking agent, an initiator and an accelerator, respectively. The cured resin products were tested for their mechanical properties and thermal stability. The results indicated that, among the fabric based resins, one prepared from the 8‐h glycolyzed product possessed the highest mechanical properties those are tensile strength, tensile modulus, flexural strength, impact strength, and hardness. The highest thermal stability was also found in the cured resin prepared from the 8‐h glycolyzed product. The mechanical properties of fabric based resins were slightly lower than those of the bottle based resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2536–2541, 2007     

Polymer concrete and polymer mortar using resins based on recycled poly(ethylene terephthalate)

Fundamental properties of polymer concrete (PC) and polymer mortar (PM) made from unsaturated polyester resins based on recycled poly(ethylene terephthalate), PET, are described. Mechanical properties investigated include strength, modulus of elasticity, ductility index, Poisson's ratio, coefficient of thermal expansion, shrinkage, and exotherm. Durability properties include chemical resistance, water absorption, sand-blast resistance, and thermal cycles of thin overlays on portland cement concrete slabs. Resins based on recycled PET offer the possibility of a lower source cost for forming useful PC and PM (PC/PM) based products. The recycling of PET in PC and PM would also help alleviate an environmental problem and save energy.     

SYNTHESIS OF UNSATURATED POLYESTER RESIN—EFFECT OF CHOICE OF REACTANTS AND THEIR RELATIVE PROPORTIONS

Unsaturated polyesters are synthesized in the laboratory by the condensation of saturated and unsaturated anhydrides with glycols. The condensate obtained is mixed with styrene monomer to get an unsaturated polyester resin formulation. The properties of the polyester resin synthesized are affected by the synthesis parameters. In this study, the parameters investigated are the effect of choice of reactants and their relative proportions. Properties such as tensile strength, tensile modulus, elongation-at-break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were tested after curing the resin. Various combinations of (a) maleic anhydride and phthalic anhydride, (b) propylene glycol and ethylene glycol, and (c) propylene glycol and diethylene glycol were used to investigate the effect on the properties of the synthesized resin. The combinations of the anhydrides and glycols that give optimum properties are identified. The results show that most of the properties are maximum at 60% maleic anhydride composition in a mixture of maleic anhydride and phthalic anhydride. Similarly, a better balance of properties is obtained when propylene glycol is mixed with 30% ethylene glycol or 20% diethylene glycol.     

Unsaturated polyester based on poly(ethylene glycol)

Unsaturated polyesters were prepared by one-stage melt condensation of maleic anhydride, phthalic anhydride, propylene glycol, and poly(ethylene glycol)s with different molecular weight, and the properties of their castings from styrenated resins were investigated. Tensile and flexural properties decrease with the increase of molecular weight of poly(ethylene glycol), but impact strength, elongation, and water absorption have an inverse effect. This study improves the understanding of the effect of chain length of poly(ethylene glycol) in unsaturated polyester on the properties of its castings.     

Structure and properties of p-carboxysuccinanilic polyester resins

Polyester resins were prepared by the reaction of p-carboxysuccinanilic acid ethyl ester with ethylene glycol and 1,4-butenediol. Also, unsaturated polyester resins were prepared by the copolymerization of p-carboxysuccinanilic acid ethyl ester and maleic anhydride with ethylene glycol, 1,6-hexanediol, 1,4-butenediol, and 2-butyne-1,4-diol. All the polyester resins and the copolyesters have been characterized and were found to cure with styrene, except those prepared in the absence of maleic anhydride. The properties of the cured products in the form of films were determined. Infrared and nuclear magnetic resonance (NMR) spectroscopy were used for both qualitative and quantitative analyses of the polyester resins and their hydrolyzate products after curing with styrene.     

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.     

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     

Unsaturated ester resins

Vinyl ester resins (VERs) are often described as a cross between unsaturated polyester resins and epoxy resins. VERs offer an upgrade to epoxy resins, and they tend to be selected when chemical and temperature resistance is required. This research was aimed at developing the synthesis of unsaturated ester resins (UERs), which are similar to VERs. UERs were synthesized by the addition of dihydrodicyclopentadienyl hydrogen maleate to the terminal epoxy groups in low‐molecular‐weight bisphenol A/epichlorohydrin epoxy resins. The effect of urethanization of UERs on the properties of the crosslinked polymer was also investigated. As crosslinking monomers, styrene and glycol dimethacrylates were used. The following properties of cured UERs were determined: the heat deflection temperature, alkali resistance, and the mechanical strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2627–2631, 2006     

Preparation and characterization of some new unsaturated polyesters based on 3,6‐bis(methoxymethyl)durene

A series of unsaturated polyester resins based on 3,6‐bis(methoxymethyl)durene with different diacids or anhydrides, namely, phthalic anhydride, maleic anhydride, and succinic acid, and different glycols, namely, 1,2‐propylene glycol, triethylene glycol, 1,4‐cyclohexane diol, and 3,6‐bis(benzyloxymethyl)durene, were prepared. Infrared and nuclear magnetic resonance spectra were used to characterize the unsaturated polyester resins obtained qualitatively and quantitatively. The average‐number molecular weight (M^?_n) was determined by end‐group analysis. These polyesters were found to cure with styrene at room temperature. The thermal behavior of the styrenated polyesters was studied via thermogravimetrical analysis and differential scanning calorimetry (TGA and DSC). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3388–3398, 2001     

Synthesis of Unsaturated Polyester Resin—Effect of Sequence of Addition of Reactants

Abstract

Unsaturated polyesters were synthesized in the laboratory by the condensation of maleic anhydride and phthalic anhydride with propylene glycol. The condensate obtained was mixed with styrene monomer to get an unsaturated polyester resin formulation. The properties of the polyester resin synthesized were found to be affected by the synthesis parameters. In this study, the effect of sequence of addition of reactants on the properties of resin was investigated. Properties such as tensile strength, tensile modulus, elongation at break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were evaluated after curing the resin. Propylene glycol necessary for esterification of both the anhydride fractions was initially reacted with phthalic anhydride. Later, the esterification was completed by reaction with maleic anhydride. This sequence of addition of reactants was found to give the best mechanical properties among all possible methods of reactant addition. Moreover, it was found that this sequence of addition of reactants gives the shortest reaction time.     

Modification of unsaturated polyesters using polyethylene glycol

Abstract

The fracture toughness and impact resistance of rigid unsaturated polyesters can be modified by various physical and chemical methods. In this study, flexible unsaturated polyesters were prepared by condensation polymerisation of maleic anhydride, phthalic anhydride and propylene glycol in the presence of polyethylene glycol. By this method, copolymers of unsaturated polyesters with polyethylene glycols of different molecular weights were prepared. A two stage process was used for the synthesis, which resulted in segmental structures containing alternating rigid cross-linked segments and linear soft segments displaced regularly in the polymer chain. Properties such as tensile strength, tensile modulus, elongation at break, toughness, impact strength, surface hardness, abrasion resistance and water absorption were tested after the resin was cured in appropriate moulds and compared with those of the control resin. Polyethylene glycols of lower molecular weight (～ 200) impart flexibility to the polyester chains and increase fracture toughness and impact resistance of rigid unsaturated polyester without seriously affecting other properties. Glass reinforced specimens prepared using the modified resin also show improved toughness and elongation at break.     

Synthesis,characterization, thermal,and viscoelastic properties of an unsaturated epoxy polyester cured with different hardeners

The chemical modification of the structure of the unsaturated polyester obtained in poly condensation process of 1,2,3,6‐tetrahydrophthalic anhydride, maleic anhydride, and ethylene glycol by well known conventional method of epoxidation with peracetic acid in mild conditions has been presented. The new material containing both epoxy groups and unsaturated double bonds in polyester chain was characterized by FTIR and ¹H NMR spectra. The prepared unsaturated epoxy polyester was suitable material for further chemical modification. Both epoxy groups and unsaturated double bonds can be used as cross‐linking sites. Curing behavior, thermal, and visco‐elastic properties of the unsaturated epoxy polyester cured with different hardeners: 1,2,3,6‐tetrahydrophthalic anhydride (THPA), hexahydrophthalic anhydride (HHPA), and/or with vinyl monomer (styrene) using radical initiator—benzoyl peroxide (BPO) were studied by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), and dynamic mechanical analysis (DMA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of chemical composition and structure of unsaturated polyester resins on the miscibility, cured sample morphology and mechanical properties of styrene/unsaturated polyester/low-profile additive ternary systems: 2. Mechanical properties

The effects of three series of unsaturated polyester (UP) resins with different chemical composition or structure on the mechanical properties of three low-shrink UP resins containing thermoplastic polyurethane, poly(vinyl acetate) and poly(methyl methacrylate) respectively have been investigated by an integrated approach of static phase characteristics–cured sample morphology–reaction conversion–property measurements. The three series of UP resins synthesized include: maleic anhydride (MA)–neopentyl glycol (NPG)–diethylene glycol (DEG) types, with various molar ratios of NPG and DEG; MA–1,2-propylene glycol (PG) types with and without modification by a saturated dibasic aromatic anhydride or acid, such as phthalic anhydride (PA) or isophthalic acid; and MA–PA–PG types modified by a second glycol, such as DEG, 2-methyl-1,3-propanediol or NPG, to partially replace PG. Based on the Takayanagi mechanical models, the effects of glycol ratios, saturated dibasic aromatic acid modification, second glycol modification, C=C unsaturation of UP and molecular weight of UP on the mechanical properties will be discussed.     

Synthesis and characterization of methacrylated star‐shaped poly(lactic acid) employing core molecules with different hydroxyl groups

A set of novel bio‐based star‐shaped thermoset resins was synthesized via ring‐opening polymerization of lactide and employing different multi‐hydroxyl core molecules, including ethylene glycol, glycerol, and erythritol. The branches were end‐functionalized with methacrylic anhydride. The effect of the core molecule on the melt viscosity, the curing behavior of the thermosets and also, the thermomechanical properties of the cured resins were investigated. Resins were characterized by Fourier‐transform infrared spectroscopy, ¹³C‐NMR, and ¹H‐NMR to confirm the chemical structure. Rheological analysis and differential scanning calorimetry analysis were performed to obtain the melt viscosity and the curing behavior of the studied star‐shaped resins. Thermomechanical properties of the cured resins were also measured by dynamic mechanical analysis. The erythritol‐based resin had superior thermomechanical properties compared to the other resins and also, lower melt viscosity compared to the glycerol‐based resin. These are of desired characteristics for a resin, intended to be used as a matrix for the structural composites. Thermomechanical properties of the cured resins were also compared to a commercial unsaturated polyester resin and the experimental results indicated that erythritol‐based resin with 82% bio‐based content has superior thermomechanical properties, compared to the commercial polyester resin. Results of this study indicated that although core molecule with higher number of hydroxyl groups results in resins with better thermomechanical properties, number of hydroxyl groups is not the only governing factor for average molecular weight and melt viscosity of the uncured S‐LA resins. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45341.     

Unsaturated polyester resins from poly(ethylene terephthalate) waste for polymer concrete

Depolymerization of poly(ethylene terephthalate), PET, textile waste was performed with a manganese acetate catalyst. Different ratios of diethylene glycol (DG) to propylene glycol (PG) were used for glycolysis. The weight ratio of PET to the glycol mixture was 1:0.65. The glycolyzed products were analyzed for hydroxyl value and the amount of free glycol. These glycolyzed products were reacted with mixtures of sebacic acid (SE) and maleic anhydride (MA) to prepare a series of unsaturated polyesters having different molecular weights. The molecular weights of the unsaturated polyesters produced were determined by the end group analysis. The obtained polyesters were dissolved in styrene (Sty) monomer and their curing behavior was investigated. Polymer concretes (PC) made with these resins were investigated for their compressive strength. The data revealed that the properties of the PC based on recycled PET are comparable to PC made from virgin materials. We concluded that recycling of PET waste may provide a potentially lower cost source of resin, and its recycling in PC will also help reduce an environmental problem.     

Synthesis and characterization of saturated and unsaturated copolyesters based on bis-1,4-(dicarboxymethoxy) benzene

Saturated copolyester were prepared by copolyesterification of bis-1,4-(dicarboxymethoxy) benzene and phthalic anhydride with diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butane diol, 1,2-propane diol, and 1,6-hexamethylene glycol. Also, unsaturated copolyesters were prepared by copolyesterification of bis-1,4-(dicarboxymethoxy) benzene and maleic anhydride with the same glycols. All the copolyester resins obtained have been characterized and unsaturated copolyesters in the form of films were determined. IR and ¹H-NMR spectroscopy were used for both qualitative and quantitative analysis of the copolyesters resins and their hydrolyzate products, after curing with styrene. © 1992 John Wiley & Sons, Inc.     

Deciphering the structure of itaconate‐based unsaturated polyester resins by high resolution mass spectrometry

Unsaturated polyester (UP) resins are widely used to manufacture composite materials and fulfil a wide panel of specification for industrial or domestic applications at low cost. These resins consist of a highly viscous polyester oligomer and a reactive diluent, which allow their processability and crosslinking. The oligomers are synthesized from diols and saturated or unsaturated diacids. Maleic anhydride is classically used as an unsaturated acid because of its reactivity for esterification and its competitive cost. However, maleic anhydride is petroleum based and classified as skin and respiratory sensitizing by the European Chemicals Agency. Itaconic acid which is recognized as one of the top 12 biobased molecules by the US Department of Energy is a biobased alternative with a reactive unsaturation. In this work, a UP based on propylene glycol, itaconic acid and dimethyl terephthalate was synthesized by polycondensation and characterized by high resolution mass spectroscopy, ¹H, ¹³C 1D and 2D NMR as well as ion mobility spectrometry mass spectrometry. The main structures were linear but cyclic species and a few branched chains due to the intermolecular Ordelt reaction were also detected by NMR and high resolution mass spectroscopy. Molecular modelling has indeed demonstrated that itaconate‐based UPs are more prone to cyclization than fumarate‐based UPs. Moreover, NMR analysis showed a significant consumption of itaconate unsaturation by the Ordelt reaction. Ion mobility spectrometry mass spectrometry allowed an additional structure to be distinguished for the same m/z peaks first attributed to a linear structure only. These results suggest the existence of cyclic species based on an intramolecular Ordelt reaction. © 2020 Society of Chemical Industry