Optimised synthesis and characterisation of high-performance unsaturated polyester resin composite laminates for industrial applications

A series of unsaturated polyester resin (UPRs) based on propylene glycol, diethylene glycol, Phthalic anhydride, maleic anhydride with different composition ratio were prepared by polycondensation reaction. Physico-mechanical properties including viscosity, hardness, acid number, gel and peak time are strongly dependent on the content of maleic anhydride in UPR. As increasing the content of maleic anhydride, physico-mechanical properties increased. The obtained UPR was stable for more than 6 months.

Effects of chemical composition and structure of unsaturated polyester (UP) resins on the miscibility of styrene (ST)/UP/low-profile additive (LPA) ternary systems containing thermoplastic polyurethane (PU), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) as LPAs, at room temperature and cured sample morphology were investigated. Three series of UP resins were synthesized, which included maleic anhydride (MA)–neopentyl glycol (NPG)–diethylene glycol (DEG) types with varied molar ratio of NPG and DEG; MA–propylene glycol (PG) types with and without modification by a saturated dibasic aromatic anhydride or acid, such as phthalic anhydride (PA) and isophthalic acid (IPA); and MA–PA–PG types modified by a second glycol, such as DEG, 2-methyl-1,3-propanediol (MPDiol), and NPG, to partially replace PG. In addition, based on the MA–PA–PG–DEG type of UP, other UPs with varied degree of unsaturation for CC bonds and molecular weight, respectively, were synthesized. The dipole moments, μ, for UP and LPA have been calculated on the basis of group contribution methods. Finally, the miscibility data of ST/UP/LPA ternary systems and the characteristics of cured sample morphology have been explained by the calculated polarity difference per unit volume between UP and LPA.

Effects of chemical composition and structure of unsaturated polyester resins on the miscibility, cured sample morphology and mechanical properties for styrene/unsaturated polyester/low-profile additive ternary systems. 1: Miscibility and cured sample morphology

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 halo and nonhalo polyesters, based on tetrachlorophthalic anhydride, tetrabromophthalic anhydride, and phthalic anhydride with diethylene glycol and maleic anhydride, have been synthesized, using a “2‐step” polyesterification process. These were mixed with 35% styrene monomer and 0.02% hydroquinone. The structural aspects of halo and nonhalo polyesters have been studied by IR and NMR. Further, these polyesters have been characterized for various properties. A comparison of various properties suggests that tensile strength, bond strength, heat resistance, flame retardance, gel time, and oxygen index follow the order as BP‐35 > CP‐35 > NHP‐35, whereas the order for other properties, such as exotherm peak temperature, thermal conductivity, % elongation, and nitroglycerine absorption, is BP‐35 < CP‐35 < NHP‐35. Variation in the properties of cured halo and nonhalo polyesters has been discussed in terms of structural considerations. The nature of P‐t profile of inhibited double‐base (DB) rocket propellants on static evaluation suggests that CP‐35 is a potential inhibitor for DB propellants. © 1993 John Wiley & Sons, Inc.

This study reports the effects of triethyl phosphate (TEP), diphenyl cresyl phosphate (DPK), and the combined amount of aluminum hydroxide (ATH) with TEP at different weight ratios as flame retardant (FR) fillers on the physical, structural, mechanical, and flammable properties of unsaturated polyester resin (UPR). The synthesis of unsaturated polyester chains based on maleic anhydride (MA), phthalic anhydride (PA), propylene glycol (PG), ethylene glycol (EG), and diethylene glycol (DEG) was conducted in a prototype stainless steel reactor at 200 ± 5°C. Unsaturated polyester chains confirmed by nuclear magnetic resonance (1H‐NMR) were diluted with styrene monomer to create ready‐to‐apply UPR. Viscosity tests were carried out on the samples that were prepared by mixing FR fillers with UPR at different loading rates without adding accelerator and initiator. Reactivity tests of the cross‐linking initialized UPR suspensions unveiled that FR fillers prolonged the peak time and lowered the peak exotherm temperature. FR filler‐induced alterations in the chemical structure of the cured samples were then monitored using Fourier transform infrared spectroscopy (FTIR). Flexural, hardness, tensile, impact, and heat distortion temperature (HDT) tests were performed on the solid samples with and without the FR fillers. The limiting oxygen index (LOI) of the samples was also examined, and TEP was eventually found to work better than DPK for the corresponding samples involved. Therefore, the samples produced by blending UPR with TEP as well as with the combined amount of TEP and ATH at different weight ratios were characterized through vertical burning (UL‐94), cone calorimeter, and smoke density tests. As a result, it was revealed that TEP operates very well on the gas phase, despite being incompetent on the condensed phase during combustion, whereas ATH acts on both gas and condensed phases in an equal mean. Furthermore, thermal degradation behavior of the samples with and without the FR fillers and their exhaust gas products were investigated using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared spectroscopy (TG‐FTIR). All the findings considering the presence of FR fillers were then evaluated and discussed in a brief manner to sort out the best combination of the additives for the UPR resin.

A method of preparing oligoestermaleinates containing isocyanuric rings by copolycondensation of 3‐(N‐2‐hydroxy‐3‐chloropropyl)isocyanurate, compound (II), and of 3‐(N‐2‐hydroxy‐3‐phenoxypropyl)isocyanurate, compound (III), with maleic anhydride alone or in mixtures with aliphatic or aromatic monocarbonic and dicarbonic acids has been developed. The copolycondensations were made with maleic anhydride, with maleic and phthalic anhydride, with maleic anhydride and adipinic acid, with maleic anhydride and oleic acid, and with maleic anhydride and stearic acid and were examined systematically. Oligoestermaleinates obtained from compound (III) have a higher temperature of dropping(dropping point) and a considerably higher thermostability than those obtained from compound (II). The oligoestermaleinates obtained from compound (II) with maleic anhydride and stearic or oleic acids are soluble in styrene and aromatic hydrocarbons; those obtained with the other substances are partially soluble in styrene. All those obtained from compound (III) are soluble in styrene. The isocyanuric oligoestermaleinates synthesized are compatible with the commercial oligoestermaleinates, such as those from ethylene glycol, diethylene glycol, and propylene glycol, and with their styrene solutions. The hardened isocyanuric oligoestermaleinates have a considerably greater thermostability than commercial oligomers hardened under the same conditions on an ethylene glycol, diethylene glycol, propylene glycol, or maleic anhydride base. The crosslinked polymers are flame‐resistant.

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.

Three types of unsaturated polyester resins were synthesized from the glycolysis of polyethylene terephthalate (PET) plastic waste, considering environment, cost and properties for their applications. These synthesized unsaturated polyester resins could be used for various construction processes and materials such as no dig pipelining (NDR-1), pultrusion (PLR-1) and polymer concrete (PCR-1). PET was taken from common soft-drink bottles, and ethylene glycol (EG), diethylene glycol (DEG) and MPdiol glycol mixtures were used for the depolymerization at molar ratios. The glycolyzed PET 1st products (oligomers) were reacted with maleic anhydride, phthalic anhydride and dicyclopentadiene (DCPD) (especially for polymer concrete) to form unsaturated polyester resins with mixed styrene. The lab scale (1–5 kg) and pilot plant scale-up tests (200 kg) were experimented to evaluate the processing characteristics, viscosity, acid number and curing behaviors. The main properties such as hardness, flexural strength, tensile strength, heat distortion temperature, elongation, and chemical resistance were determined based on the various uses of the three resins. Furthermore, the applicability and the properties of these developed resins were verified through many real application tests.

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 ortho unsaturated polyester resin (UPR) was successfully synthesized from propylene glycol, and diethylene glycol in the presence of acids such as phthalic anhydride and maleic anhydride using polycondensation reaction, where styrene is used as a cross-linker, which is catalysed by triphenyl phosphate and accelerated by cobalt octate. The Fire-retardant properties were incorporated into UPR using fire-retardant additives such as Aluminium trihydrate and Ammonium polyphosphate resulting in efficient fire-retardant resin. The liquid and casted mechanical properties of UPR resin are studied and The UPR composite was manufactured through the hand layup method, with the Ecorrosion resistant glass fiber reinforcement with different stacking layers. The synthesized resin to the glass fiber ratio was less than other commercial resin to glass-fiber ratios. The final composite properties were found in the acceptable range.

Postconsumer PET bottles including water and soft‐drink bottles were depolymerized by glycolysis in excess glycols, such as ethylene glycol, propylene glycol, and diethylene glycol, in the presence of a zinc acetate catalyst. The obtained glycolyzed products were reacted with maleic anhydride and mixed with a styrene monomer to prepare unsaturated polyester (UPE) resins. These resins were cured using methyl ethyl ketone peroxide (MEKPO) as an initiator and cobalt octoate as an accelerator. The physical and mechanical properties of the cured samples were investigated. It was found that the type of glycol used in glycolysis had a significant effect on the characteristics of the uncured and cured UPE resins. Uncured EG‐based UPE resin was a soft solid at room temperature, whereas uncured PG‐ and DEG‐based resins were viscous liquids. In the case of the cured resins, the EG‐based product exhibited characteristics of a hard and brittle plastic, while the PG‐based product did not. The DEG‐based product exhibited characteristics of hard and brittle plastic after strain‐induced crystallization had occurred. In addition, it was also found that no separation of the type of bottles was needed before glycolysis, since UPE resins prepared from water bottles, soft‐drink bottles, and a mixture of both bottles showed the same characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 788–792, 2003

Abstractβ‐Myrcene, a terpenic monomer, holds potential for developing sustainable polymer‐based materials with enhanced properties. This study examines the synthesis of a myrcene‐based monomer and its incorporation into unsaturated polyesters, focusing on polymerization, curing, and final properties. Unsaturated polyesters were synthesized with varying myrcene‐based monomer content (6, 12, and 24 mol%), phthalic anhydride, maleic anhydride, propylene glycol, ethylene glycol, and diethylene glycol. Polymerization achieved conversion values of 0.92–0.93, resulting in polyesters with molar masses between 1400 and 1700 g mol−1 and dispersity indices of 2.0 to 2.3. Nuclear magnetic resonance (1H NMR) demonstrated short branch formation in myrcene‐modified polyesters and a high maleate‐to‐fumarate isomerization rate (92.66%–95.7%), affecting carbon–carbon double bonds per polyester mole (2.27 to 4.28) and final resin performance. Rheological analysis in a styrene solution (70/30 wt%) indicated shear‐thinning behavior, with viscosities ranging from 0.59 to 3.8 Pa·s, suggesting branching affects chain entanglement. Differential scanning calorimetry (DSC) revealed decreased curing enthalpy with increasing myrcene content, and it was inferred that myrcene's double bonds did not participate in curing. Glass transition temperatures of cured polyesters (70–107 °C) correlate with enthalpy trends. Thermal stability of myrcene‐modified polyesters is similar to the reference polyester, highlighting myrcene's potential as a sustainable monomer for customizable unsaturated polyesters.

Kinetics of melt polymerization of maleic acid phthalic acids with propylene glycol

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.