Synthesis and mechanical properties of unsaturated polyester based nanocomposites

Two classes of nanocomposites were synthesized using an unsaturated polyester resin as the matrix and sodium montmorillonite as well as an organically modified montmorillonite as the reinforcing agents. X‐ray diffraction pattern of the composites showed that the interlayer spacing of the modified montmorillonite expanded from 1.25 nm to 4.5 nm, indicating intercalation. Glass transition values of these composites increased from 72°C, in the unfilled unsaturated polyester, to 86°C in the composite with 10% organically modified montmorillonite. From Scanning Electron Microscopy, it is seen that the degree of intercalation/exfoliation of the modified montmorillonite is higher than in the unmodified one. The mechanical properties also supported these findings, since in general, the tensile modulus, tensile strength, flexural modulus, flexural strength and impact strength of the composites with modified montmorillonite were higher than the corresponding properties of the composites with unmodified montmorillonite. The tensile modulus, tensile strength, flexural modulus and flexural strength values showed a maximum, whereas the impact strength exhibited a minimum at approximately 3–5 wt% modified montmorillonite content. These results imply that the level of exfoliation may also exhibit a maximum with respect to the modified montmorillonite content. The level of improvement in the mechanical properties was substantial. Adding only 3 wt% organically modified clay improved the flexural modulus of unsaturated polyester by 35%. The tensile modulus of unsaturated polyester was also improved by 17% at 5 wt% of organically modified clay loading.     

Thermo mechanical behaviour of unsaturated polyester toughened epoxy–clay hybrid nanocomposites

The intercrosslinked networks of unsaturated polyester (UP) toughened epoxy–clay hybrid nanocomposites have been developed. Epoxy resin (DGEBA) was toughened with 5, 10 and 15% (by wt) of unsaturated polyester using benzoyl peroxide as radical initiator and 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. The chemical reaction of unsaturated polyester with the epoxy resin was carried out thermally in presence of benzoyl peroxide-radical initiator and the resulting product was analyzed by FT-IR spectra. Epoxy and unsaturated polyester toughened epoxy systems were further modified with 1, 3 and 5% (by wt) of organophilic montmorillonite (MMT) clay. Clay filled hybrid UP-epoxy matrices, developed in the form of castings were characterized for their thermal and mechanical properties. Thermal behaviour of the matrices was characterized by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Mechanical properties were studied as per ASTM standards. Data resulted from mechanical and thermal studies indicated that the introduction of unsaturated polyester into epoxy resin improved the thermal stability and impact strength to an appreciable extent. The impact strength of 3% clay filled epoxy system was increased by 19.2% compared to that of unmodified epoxy resin system. However, the introduction of both UP and organophilic MMT clay into epoxy resin enhanced the values of mechanical properties and thermal stability according to their percentage content. The impact strength of 3% clay filled 10% UP toughened epoxy system was increased by 26.3% compared to that of unmodified epoxy system. The intercalated nanocomposites exhibited higher dynamic modulus (from 3,072 to 3,820 MPa) than unmodified epoxy resin. From the X-ray diffraction (XRD) analysis, it was observed that the presence of d ₀₀₁ reflections of the organophilic MMT clay in the cured product indicated the development of intercalated clay structure which in turn confirmed the formation of intercalated nanocomposites. The homogeneous morphologies of the UP toughened epoxy and UP toughened epoxy–clay hybrid systems were ascertained from scanning electron microscope (SEM).     

Reaction kinetics and physical properties of unsaturated polyester modified with methylacyloxylpropyl-POSS

The polyhedral oligomeric silsesquioxanes which contains methylacryloylpropyl group (MAP-POSS) was synthesized and used to modify unsaturated polyester resin (UPR). The cure kinetics was investigated by isothermal DSC technique. The mechanical and electrical properties of fiberglass-reinforced laminate were determined. The result shows that the reaction can be described by a Kamal autocatalytic model which has two reaction rate constants k ₁ and k ₂, and two apparent activation energies E _a1 and E _{a 2} are 98.12 kJ/mol and 74.01 kJ/mol, respectively. UPR and MAP-POSS can co-cure in free radical polymerization. When the MAP-POSS content is 5 wt%, the impact and tensile strength of fiberglass-reinforced laminate enhanced 10% and 6%, respectively, and has better electrical properties than no MAP-POSS. The dielectric constant ε and dielectric loss tanδ are all decrease. The surface resistance ρ _s is 4.7 times higher than pure UPR laminates     

Morphology development and mechanical properties of unsaturated polyester resin containing nanodiamonds

Unsaturated polyester/styrene (UP ) resin was filled with nanodiamonds (NDs ) containing carboxyl and methacrylate functionalities using mechanical mixing. Field emission SEM exhibited a uniform dispersion of tightly bound aggregates of nanosized spherical NDs with good interfacial interaction. Rheological measurements exhibited a step increment in the shear viscosity of a UP /ND suspension at 0.6 wt% ND resembling a percolation state at this loading. Shear viscosity data supported by dynamic mechanical analysis results suggested the development of effective ND particles in which ND aggregates were covered by only polyester macromolecules. Accordingly, the morphology of UP /ND composites approached a quasi‐percolation state at 0.6 wt% in which effective ND particles were connected thoroughly, instead of direct ND ?ND contact, forming a co‐continuous polyester phase covering the ND particles. Based on such morphology, DSC and Fourier transform infrared analysis suggested the development of heterogeneous microgels in cured UP resin containing NDs which in turn governed the overall mechanical properties of the composites. © 2017 Society of Chemical Industry     

Thermal and mechanical properties of functionalized mullite reinforced unsaturated polyester composites

This work studies the development of varying weight percentages (0.5, 1.0, and 1.5 wt%) of surface functionalized mullite reinforced unsaturated polyester (UP) composites and their thermal, dielectric, water absorption, and mechanical properties. The synthesized mullite was functionalized with vinyltriethoxysilane (VTES). The introduction of vinyl groups on the surface of mullite was confirmed by FT‐IR, TGA, and X‐ray diffraction (XRD) analyses. Varying weight percentages (0.5, 1.0 and 1.5 wt%) of vinyl functionalized mullite (VFM) were incorporated into UP resin with a benzoyl peroxide initiator to obtain composites. The resultant data obtained from thermal, mechanical, dielectric, and water absorption studies, indicate that incorporation of VFM, leads to a significant improvement in the thermo mechanical, dielectric, and moisture resistant properties of the UP composites, compared with those of neat UP matrices. The molecular dispersion of VFM fiber in reinforced UP matrix composites was confirmed by SEM analysis. POLYM. COMPOS., 35:1663–1670, 2014. © 2013 Society of Plastics Engineers     

Microgel formation and thermo‐mechanical properties of UV‐curing unsaturated polyester acrylates

The effect of internal and terminal unsaturation on the properties of the acrylated polyester films was investigated. Four types of acrylated polyester resin were prepared using adipic acid, maleic anhydride, neopentyl glycol, trimethylolpropane, and acrylic acid. Terminal and internal double bond content as well as branching was adjusted by the molar quantities of trimethylolpropane and maleic anhydride, respectively. A reactive diluent, trimethylolpropane triacrylate (TMPTA), was also used. A three‐factor, three‐level Box‐Behnken design was used to investigate complex nonlinear relationships. Dynamic mechanical, fracture toughness, and tensile properties were evaluated with respect to the amount of terminal and internal unsaturation, and reactive diluent concentration. It was found that microgel formation extensively affects the final UV‐cured film properties. Small quantities of microgels function as micro‐support units, whereas high extent of microgelation causes phase separation through cluster formation and hence, decreases the mechanical properties. It is essential to control the extent of microgelation and phase separation to optimize product performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Curing of unsaturated polyester resins—effects of comonomer composition. III. Medium-temperature reactions

The effects of comonomer composition on the curing kinetics of unsaturated polyester (UP) resins at 70–90°C were studied by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy over the whole conversion range. One commercial UP resin, UP2660PF2, with cobalt promoter added and with 8.85 unsaturated C?C bonds per polyester molecule, was used. It was found that a marked shoulder in the initial DSC rate profile, rather than that reported after the peak of rate profile for low-temperature and high-temperature reactions, appeared when the molar ratio of styrene to polyester C?C bonds was greater than 1. With the initiator system accelerated by cobalt promoter, the formation rate of microgel particles would be enhanced at the early stage of reaction, as supported by the much higher conversion of polyester C?C bonds than that of styrene by IR spectroscopy. Those relatively greater number of microgel particles tended to facilitate the intramicrogel crosslinking reactions, which would be independently identified from the initial DSC rate profile as a shoulder. Consequently, the reaction mechanism was elucidated by decomposing the reaction rate profile into two individual profiles accounting for the intramicrogel dominated and the intermicrogel dominated crosslinking reactions, respectively. © 1993 John Wiley & Sons, Inc.     

Flame retardancy and mechanical properties of a novel intumescent flame‐retardant unsaturated polyester

A novel macromolecular intumescent flame retardant (MIFR) was synthesized. Unsaturated polyester (UP) filled with MIFR as flame‐retardant additive was prepared. The effects of MIFR on properties such as tensile strength, impact strength, flame‐retardant behavior, thermal stability, and morphology of char were studied. Its flammability and burning behavior were characterized by UL 94 and limiting oxygen index. Twenty‐four percent of MIFR were doped into UP to get 30.5% of limiting oxygen index and UL 94 V‐0, whereas its tensile strength and the impact strength were decreased by only 7.2% and 7.0%, respectively. Activation energy for the decomposition of samples was obtained by using the Kissinger equation. The results for UP containing MIFR, compared with UP, show that the weight loss, thermal stability, and the decomposition activation energy decreased, and the char yield increased, showing that MIFR can catalyze decomposition and carbonization of UP to form an effective charring layer to protect the underlying substrate. J. VINYL ADDIT. TECHNOL., 22:350–355, 2016. © 2014 Society of Plastics Engineers     

Curing studies on modified epoxy and unsaturated polyester resins

Experimental studies were carried out on the curing behavior of unsaturated polyester and epoxy resins. The latter were modified with three different fillers (CaCO₃, CaSiO₃, and glass powder) and their curing behaviors studied. Polyesters exhibited faster cure rates than the epoxy resins. The gel time of the epoxy resins decreased with the addition of fillers. Data indicated that the peak exotherm of these thermosetting resins increased when filled with glass powder. The hardness of the curing mass increased with curing time. The use of gel-hardness number as a quality control parameter has been suggested.     

Curing of unsaturated polyester resins—effects of pressure

The effects of pressure ranging from 0.1 to 6.21 MPa (0–900 psig) on the curing of unsaturated polyester resins at 110°c were investigated by an approach of integrated reaction kinetics-rheology-morphology measurements using a pressure differential scanning calorimeter (DSC), an infrared spectrophotometer (IR), a Haake rheometer, and by using scanning electron microscopy (SEM). Increasing pressure was found to delay the gel effect, and a previously unknown plateau of kinetic-controlled region in the initial portion of the DSC rate profile was observed. The plateau region was mainly attributed to the crosslinking of C ? C double bonds inside the microgel particles, as revealed by the conversions of styrene and polyester C ? C bonds measured by IR, gel conversion data and SEM micrographs. The mechanisms of reaction kinetics both at atmospheric pressure and under pressures have also been elucidated by the progress of buildup of microgel structures.     

Interfacial reactions in carbon—epoxy composites

A series of models for the carbon-epoxy interphase are developed comprising high surface area carbon blacks, crushed carbon fibres and chopped carbon fibres dispersed in epoxy matrices. The carbon surfaces are modified by oxidative or reducing treatments and the effects of the modified carbon surfaces on the epoxy cross-linking processes are examined by differential scanning calorimetry and infrared spectroscopy. Oxidised carbon surfaces retard the cure of anhydride-epoxy systems by adsorption of the tertiary amine catalyst. Oxidised carbon surfaces initially accelerate epoxy-amine reactions but inhibit the later stages of the reaction such that the final level of cure is reduced. These modifications to the chemistry of the interfacial region influence the properties of carbon-epoxy composites.     

Reinforcement of EPDM matrices with carbon and polyester fibers—mechanical and dynamic properties

This paper reports on the study of the mechanical and dynamic properties of composites with an EPDM matrix and short fiber, either polyester or carbon, at three different fiber concentrations. In general, the properties prove to be dependent on fiber concentrations and type, in particular on the final ratio fiber length/diameter. This ratio ranges for carbon fiber over 35–45 and for polyester over 135–175, thus placing the former near the lower limit of acceptability. Evidence is supplied of the existence of adhesion between the matrix and the fiber, in the form of measurements of the swelling and dynamic properties, especially through variation of relative damping and the displacement of the dynamic glass transition temperature towards higher ranges. Composites present a marked property anisotropy.     

Carbon black containing IPNs based on unsaturated polyester/epoxy. I. Dynamic mechanical properties,thermal analysis,and morphology

A series of carbon black containing interpenetrating polymer networks (IPNs) based on unsaturated polyester/epoxy (weight ratios 10/90, 20/80, 30/70) were developed. Scanning electronic microscopy exhibits that the compatibility was decreased and the morphology seemed to become less rigid as the content of unsaturated polyester increased in IPNs. The results also indicate that flame retardants were uniformly distributed in the IPN matrices. It is found that the heat resistance, damping, and mechanical properties were all improved simultaneously by adding the plate‐shaped carbon black flame retardants to the unsaturated polyester/epoxy IPNs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1904–1910, 2002     

The effect of nanoclay and MWNT on fire‐retardency and mechanical properties of unsaturated polyester resins

The influence of nanomaterials such as Multi‐Walled Carbon NanoTubes (MWNT) and organoclay (Cloisite 30B) on the physical and mechanical properties of thermoset matrix such as Unsaturated Polyester (UP) resins is investigated. Although styrene containing UP resins have a wide spread application in industry, lack of information exists regarding the behavior of MWNT/organoclay/polyester ternary nanocomposite systems. The main aim of this research was first to evaluate the effect of nanofiller on the flammability of UP resins and, second, to characterize their mechanical properties such as toughness and their tensile strength. The rheological studies showed shear thinning for samples of UP resins containing MWNT and Cloisite 30B. The cone calorimetry measurement was used to evaluate the flame‐retardency, the gas emission of the nanocomposite and whether or not this system can be designated as a nanocomposite. This was understood in the test by the peak heat release rate being lowered and shifted to shorter times. Furthermore, the tensile and impact properties of samples were evaluated. The obtained results indicated that nanofiller particles caused both increase and decrease in the impact and tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

SiC颗粒增强不饱和聚酯树脂复合材料的力学性能

采用万能试验机和硬度计测试研究了SiC颗粒含量和粒径对不饱和聚酯树脂基复合材料力学性能的影响,通过扫描电子显微镜观察了拉伸试样的端口形貌。结果表明,填充的SiC质量分数为10%时,其不饱和聚酯树脂复合材料拉伸强度达到最大,8000目、1000目SiC填充体系拉伸强度分别为53.2MPa,44.8MPa,较纯树脂体系提高68.1%,41.5%。当SiC质量分数为30%时,SiC填充体系的弹性模量较纯树脂体系提高25.8%以上,硬度提高2.3%以上,SiC颗粒尺寸对复合材料的弹性模量和硬度影响不大。SiC/不饱和聚酯树脂复合材料的断裂属脆性断裂。     

Low profile unsaturated polyester resin–clay nanocomposite properties

Unsaturated polyester (UP)/organically modified clay (OMC) nanocomposites were prepared by multistep simultaneous mixing of UP oligomer chain, styrene (St) monomer, and OMC. X‐ray diffraction, transmission electron microscopy, dynamic mechanical thermal analysis, and scanning electron microscopy data were in support of the formation of a partially intercalated nanocomposite. The glass transition temperatures of the nanocomposites revealed that the crosslinking reaction occurred homogeneously inside and outside of the OMC galleries. Adding 3 wt% OMC improved the flextural and storage modulus of UP by 31.5% and 30.2%, respectively. The Izod impact strength of UP was also improved by 51.7% at 1 wt% of OMC loading. Similar results were obtained for low‐profile UP/St/OMC nanocomposites. Resin shrinkage data measured by inhouse constructed apparatus showed that, at an OMC content of 3 wt%, the UP/St/OMC/low profile additive (LPA) system cannot provide superior volume shrinkage control. But, it is found that the use of nanoscale reinforcement in the UP systems is able to restore flextural and storage moduli loss when using LPAs. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Chemorheology on simultaneous IPN formation of epoxy resin and unsaturated polyester

Study of the simultaneous interpenetrating polymer network (IPN) between diglycidyl ether of bisphenol-A (DGEBA) and unsaturated polyester (UP) was carried out at ambient temperature. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the intermolecular H-bonding and functional group changes. Viscosity changes due to H-bonding and crosslinking were examined with a Brookfield viscometer. Gelation time was measured by a Techne gelation timer. Complexation between Co(II) (the promoter for UP cure) and diamine (the curing agent for DGEBA) was detected with UV-visible spectrometer. Experimental evidence revealed that intermolecular interactions were observed in systems such as DGEBA/UP, DGEBA/diamine, Co(II)/diamine, DGEBA/uncured UP, and UP/uncured DGEBA. All such interactions had measurable effects on the curing behaviors for both networks, as were indicated by the viscosity changes and gelation time. The IPNs thus obtained were further characterized with rheometric dynamic spectroscopy (RDS) and differential scanning calorimetry (DSC). Partial compatibility between UP and DGEBA networks was evidenced from a main damping peak with a shoulder near glass transition temperature (T_g) for lower UP content; while at higher UP content, only a main damping peak near T_g was observed. DSC revealed a broad glass transition for all IPNs. The resultant IPN materials were all transparent. © 1992 John Wiley & Sons, Inc.     

Toughened interpenetrating polymer network materials based on unsaturated polyester and epoxy

Simultaneous interpenetrating polymer networks (IPNs) based on epoxy (diglycidyl ether of bisphenol A) and unsaturated polyester (UP) were prepared by using m‐xylenediamine and benzoyl peroxide as curing agents. A single glass transition temperature for each IPN was observed with differential scanning calorimetry, which suggests good compatibility of epoxy and UP. This compatibility was further confirmed by the single damping peak of the rheometric dynamic spectroscopy. Curing behaviors were studied with dynamic differential scanning calorimetry, and the curing rates were measured with a Brookfield RTV viscometer. It was noted that an interlock between the two growing networks did exist and led to a retarded viscosity increase. However, the hydroxyl end groups in UP catalyzed the curing reaction of epoxy; in some IPNs where the hydroxyl concentration was high enough, such catalytic effect predominated the network interlock effect, leading to fast viscosity increases. In addition, the entanglement of the two interlocked networks played an important role in cracking energy absorption and reflected in a toughness improvement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 585–592, 1999     

The effect of silane-coated slag mineral on the mechanical and dynamic mechanical properties of unsaturated polyester composite materials

Abstract

To determine the potential of a sustainable by-product from iron-making industry ‘Slag’ as reinforcing agent for thermoset polymer composite, particularly unsaturated polyester (UPE). The slag has been coated by reactive and nonreactive silanes. In the first stage, the slag was comminuted and sifted prior to silane coating. The silane-coating agent adsorbed on the surface of the slag was followed by thermogravimetric analysis (TGA) and attenuated total reflectance infrared spectroscopy (ATR-IR). The fabricated composites with various silane-coated slag were inspected with respect to tensile and flexural properties as a function of the coating agent. Scanning electron microscope was carried out on the composite with uncoated and silane-coated samples. The obtained findings indicated that the slag coated with amino and octyltrioxy-based silanes showed a positive impact on the mechanical performance. The improvement was related to the structure of coupling agent used.