Vinyl Ester Resin Composites Research Articles

Investigation of Mechanical Properties of Short Sisal Fiber Reinforced Phenol Formaldehyde and Vinyl Ester Composites

Composite materials are replacing standard Engineering metals and alloys for many applications. Here in this work, Sisal fiber is used as reinforcement. Since it is abundantly available in nature and majority of it is getting wasted without being used as reinforcement in engineering applications. Short Sisal fiber reinforced Phenol Formaldehyde and Vinyl Ester resin composites are prepared with varied fiber lengths (5 mm and 10 mm) and for varied weight fraction (20%, 25% and 30%) of the fibers. The short Sisal fibers are treated with 5% of Sodium Hydroxide (NaOH) solution. In the present work, the effect of the fiber treatment, fiber length and fiber loading on the mechanical properties are investigated. The results show that the Alkali Treated Sisal fiber reinforced composites have better mechanical properties than untreated composites. The 10 mm fiber length reinforced composite shown improved mechanical properties than 5 mm fiber length reinforced composite. Increase in mechanical properties is seen when the fiber content in the composite is increased from 20% to 25% and 25% to 30%. The 30% weight of the Sisal fiber reinforced composite has shown higher values of mechanical properties.

Integrated design of flame retardancy, smoke suppression and structure of carbon fiber reinforced vinyl ester resin composites through intercalation of nanofiber membranes

A novel flame-retardant method based on the intercalation of nanofiber flame-retardant membrane has been studied for composite laminates. Compared to traditional additive flame-retardant method, this method is more efficient, does not affect the composite forming process, and can improve the mechanical properties of composite. Nanofiber flame-retardant membranes (FPm) are prepared from polyether sulfone (PES) and pentaerythritol phosphate ester (PEPA) by electrospinning technique and inserted in the interlayer of carbon fiber reinforced vinyl ester resin (CF/VER) composites. The FPm can improve the flame-retardancy and smoke suppression of the CF/VER composites by promoting the charring of interlayer structure and form a barrier layer. The thickness of the FPm and the flame-retardant performance of the composites are positive correlation. At a FPm’s thickness of 50 μm, the limiting oxygen index (LOI) and UL-94 ratings of the CF/VER composites reached 33.5 % and V-1, respectively. The total heat release (THR) and total smoke release (TSP) are reduced by 26.4 % and 30.4 %, respectively. Due to the interlayer enhancement effect of FPm, the mechanical strength and interlaminar fracture toughness of CF/VER composites are also improved. Especially, when the thickness of FPm is 30 μm, the mode I interlaminar fracture toughness (GIC) of the CF/VER composite increased by 17.4 %. while the flexural strength, interlayer shear strength (ILSS), mode II interlaminar fracture toughness (GIIC) and storage modulus (E’) are all enhanced.

Interfacial engineering of glass fiber‐reinforced vinyl ester resin composites: Using polydopamine‐SiO2 for property enhancement

AbstractTo enhance the flexural properties of glass fiber‐reinforced vinyl ester resin (GF‐VER) composites, this study focused on the influence of the duration of surface treatment on the flexural properties using polydopamine (PDA) and nanosilicon dioxide (nano‐SiO2). The GF‐VER composites were prepared via hot pressing. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were utilized to characterize the microstructural and chemical attributes of the GF and GF‐VER composites. The mechanical properties of the GF‐VER composites were characterized using the flexural strength test. Furthermore, thermogravimetry was employed to investigate the thermal stability of the GF and the content of PDA nanoparticles on the GF. The results demonstrated that upon extending the treatment period, a greater quantity of PDA‐SiO2 nanoparticles adhered to the surface of the GF. The analysis of these results established that the optimal treatment duration is 12 h. This duration facilitated an enhanced adhesion between GF and VER owing to PDA‐SiO2, resulting in an optimal flexural strength of 562.8 MPa and signifying a 8.86% increase compared with the flexural strength of the untreated GF‐VER composites. Overall, the findings indicate that PDA‐SiO2 treatment greatly improves the flexural strength of GF‐VER composites.Highlights The method for modifying the GF surface was simple and mild. Silica nanoparticles were grafted onto GFs using dopamine as a reaction platform. The effect of the duration of PDA‐SiO2 treatment on the flexural strength of GF‐VER composites was examined. SEM revealed an improved GF‐VER interface. The flexural strength of the GF‐VER composites improved by 8.86%.

Phosphorus-containing reactive compounds to prepare fire-resistant vinyl resin for composites: Effects of flame retardant structures on properties and mechanisms

The traditional flame-retardant method for carbon fiber reinforced vinyl ester resin composites is to add a large amount of solid flame retardants, which not only leads to the deterioration of the material's mechanical properties, but also increases the resin viscosity and affects the molding process of composites. In addressing this issue, this work adopts a liquid reactive flame retardant strategy and synthesizes six novel liquid phosphorus-containing reactive compounds as flame retardants. A comparative study is conducted on the effects of the structure of compounds (valence and group of phosphorus and number of reaction groups) on the properties of materials. The results demonstrate significantly improved flame retardancy and toughness, as well as unaffected viscosity and strength of the resin. When the phosphorus content does not exceed 3 wt%, the limiting oxygen index (LOI) of the resin can reach over 30% and UL-94 passes the V-0 rating. The structure of compounds significantly affects their flame retardancy mechanism. Especially, compounds rich in P-O-C structure have more outstanding condensed phase flame retardancy (promoting charring) and are more favorable for improving the LOI; Compounds rich in P-Ph and P-C structures have higher thermal stability and mainly exert gas phase flame retardancy, which is more beneficial for improving the self-extinguishing properties of materials. Furthermore, a synergistic flame retardant effect is observed between carbon fiber and compounds rich in P-Ph.

Vanillin and organosilicon functionalized graphene oxide modified ester resin composite coatings with excellent anti-corrosion properties

Epoxy vinyl ester resin is widely used in the field of corrosion protection because of its excellent corrosion resistance and mechanical properties. However, due to the ease of hydrolysis of the ester group in the ester resin, the barrier ability of the coating is reduced, which will accelerate metal corrosion. The existing literature shows that the use of nano-sheet materials such as graphene oxide (GO) can effectively enhance the barrier properties of the coating. In order to solve the poor compatibility and electrical corrosion phenomenon of GO, in this work, renewable vanillin and silicone with excellent anti-corrosive properties were grafted to GO (APGO) by insertion reaction and D-A reaction. Subsequently, a series of new APGO-based epoxy vinyl ester resin composites with excellent mechanical properties and anti-corrosion properties were prepared by thermal crosslinking polymerization. The results showed that when the additive amount of APGO was 0.1 wt%, the comprehensive performance of the composite was the best: the conductivity (1.9 × 10−13–5.6 × 10−13 S/cm) of the composite was far lower than the critical electrical insulation value (10−9 S/cm), the breaking strength was improved by 38.0 %, the contact angle was increased by 65.7 %, and its anti-corrosion efficiency was up to 99.03 %. After 70 days of immersion in 3.5 wt% salt water, the impedance modulus of the composite at low frequency (Zf = 0.01 Hz) remained 2.23 × 1010 Ω cm2, which was 2 orders of magnitude higher than that of pure epoxy vinyl ester resin (2.43 × 108 Ω cm2). The above results were not only related to the maze effect formed by APGO, but also related to the increased crosslinking density of the system. This work provided a novel strategy for preparing GO-based composites with excellent comprehensive properties.

A Bridge-Linked Phosphorus-Containing Flame Retardant for Endowing Vinyl Ester Resin with Low Fire Hazard

The high flammability of vinyl ester resin (VE) significantly limits its widespread application in the fields of electronics and aerospace. A new phosphorus-based flame retardant 6,6'-(1-phenylethane-1,2 diyl) bis (dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (PBDOO), was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acetophenone. The synthesized PBDOO was further incorporated with VE to form the VE/PBDOO composites, which displayed an improved flame retardancy with higher thermal stability. The structure of PBDOO was investigated using Fourier transformed infrared spectrometry (FTIR) and nuclear magnetic resonances (NMR). The thermal stability and flame retardancy of VE/PBDOO composites were investigated by thermogravimetric analysis (TGA), vertical burn test (UL-94), limiting oxygen index (LOI), and cone calorimetry. The impacts of PBDOO weight percentage (wt%) on the flame-retardant properties of the formed VE/PBDOO composites were also examined. When applying 15 wt% PBDOO, the formed VE composites can meet the UL-94 V-0 rating with a high LOI value of 31.5%. The peak heat release rate (PHRR) and the total heat release (THR) of VE loaded 15 wt% of PBDOO decreased by 76.71% and 40.63%, respectively, compared with that of untreated VE. In addition, the flame-retardant mechanism of PBDOO was proposed by analyzing pyrolysis behavior and residual carbon of VE/PBDOO composites. This work is expected to provide an efficient method to enhance the fire safety of VE.

High-performance biobased vinyl ester resin and its fiberglass-reinforced composite with high glass transition temperature (Tg), excellent flame retardancy and mechanical properties

In this study, a biobased vinyl ester resin monomer with Schiff base is prepared from protocatechualdehyde. The monomer is dissolved into styrene to prepare the biobased resin designated as OBTMAR. The resin is perfused into the fiberglass to prepare a fiber-reinforced composite (GFOBTMAR). The commercial vinyl ester resin (VER901) and its fiberglass-reinforced composite (GFVER901) are prepared as the control. Tg values of OBTMAR and GFOBTMAR are 219 and 222 °C, respectively, which are far higher than those of VER901 (127 °C) and its composites (131 °C). And there is no separation between the resin and fiberglass for GFOBTMAR due to excellent fiberglass wettability. Cone calorimeter test suggests that GFOBTMAR shows the best flame retardancy and lowest smoke release. The related mechanism of flame retardancy is studied in detail. This work presents an effective strategy for developing fiberglass-reinforced vinyl ester resin composites with high Tg, superior flame retardancy and mechanical properties for application.

Experimental Investigation on Hygroscopic Aging of Glass Fiber Reinforced Vinylester Resin Composites.

The hygroscopic behavior of vinylester resin and high strength glass fiber reinforced vinylester resin composites were examined here, including weight change and the resulting degradation of mechanical properties. The prepared resin and composites specimens were immersed in deionized water and artificial seawater with an applied temperature of 70 °C, and then the specimens were weighed at specified time intervals in combination with the observation of surface morphologies using a scanning electron microscope. Identification of variations of functional groups was also carried out using Fourier-transform infrared spectroscopy. Meanwhile, the mechanical properties for resin and the composite specimens were tested periodically. The observations on surficial morphologies and the test on weight change display that the vinylester resin hydrolyzes seriously after immersion in deionized water, and that the embedment of glass fiber effectively inhibits the moisture absorption and hydrolysis for resin matrix in composites. The results from the mechanical properties test reveal that the tensile strength of pure resin decreases by 35.3% after 7 days’ immersion and keeps small fluctuation in the sequent immersion duration. However, the compressive strength of pure resin consistently dwells at 100 ± 2 MPa during immersion. After immersion for 90 days, the tensile strength decreases by 28.5% and 38.4%, the compressive strength reduces by 7.2% and 16.6%, and the in-plane shear strength reduces by 16.6% and 15.2% for the composites immersed into deionized water and artificial seawater, respectively. The main highlights of this paper are that it provides a more comprehensive mechanical properties test in combination with the microscopic characterization on a matrix and its composites to reveal the aging behavior of composites under a hygroscopic environment.

Mechanical properties of Nomex honeycombs filled with tubes of carbon fibre reinforced vinyl ester resin composites

The Nomex honeycomb structures filled with carbon fibre reinforced vinyl ester resin composite tubes (NHFCT) were proposed to improve the energy absorption capacity of Nomex honeycombs. Thereafter, the mechanical properties of the NHFCT structures were explored based on the quasi-static pressure test, finite element simulation, and a theoretical model. The test result showed that the NHFCT structures enable increased SEA while retaining the energy absorption performance of Nomex honeycombs. When applying a certain load on the NHFCT structures, the Nomex honeycombs are folded; the CFRP tubes are torn and expanded, and the embedded cells bulge. The established finite element simulation model was used to simulate the deformation of NHFCT structures and the theoretical model was employed to predict their energy absorption performance. Tests applicable to the practical application revealed that NHFCT structures of a large area present more stable performance and the superimposed NHFCT structures are subjected to step-wise gradient deformation. The CFRP tubes suffer slight indentation on the panel between layers and they are torn in a funnel shape under the effect of the panel stiffness. The research provides reference for improving the mechanical properties of Nomex honeycomb structures and broadening their range of application.

Simultaneous improvements of the fire safety, mechanical properties and water resistance of vinyl ester resin composites by introducing microencapsulated ammonium polyphosphate by polytriazole

Achieving a good balance between mechanical properties and flame retardancy of vinyl ester resin (VER) remains a challenge for traditional inorganic retardants. Herein, a reactive coating shell was constructed on the surface of ammonium polyphosphate (APP) through click chemical reaction. The microencapsulated APP (MAPP) was introduced into and reacted with VER matrix. The coating and the reaction between the filler and the matrix bring a dual effect on comprehensive properties. 10 wt% addition of MAPP not only endow material with better fire safety including a limiting oxygen index of 27.1%, 44% reduction of total heat release, and 38% reduction of total smoke production, but also enhance the flexural and notched Izod impact strength compared with pure VER. The composite exhibits enhanced water resistance, as evidenced by relatively less reduction of flexural strength after immersing in boiling water for 6 h. The dual function enhancement strategy can provide new ideas to prepare composites with balanced flame retardancy, water resistance and mechanical properties.

Improved mechanical and flame resistance properties of vinyl ester resin composites by lithium containing polyhedral oligomeric phenyl silsesquioxane

AbstractThe mechanical and flame retardancy properties of vinyl ester resin (VER) composites containing lithium containing polyhedral oligomeric phenyl silsesquioxane (Li‐Ph‐POSS) are investigated. The bending test suggests that Li‐Ph‐POSS improves the mechanical property of the matrix. Compared with the pure VER, the bending strength and flexural modulus are improved by 42.9% and 18.9% with the addition of 3 wt% Li‐Ph‐POSS, respectively. And cone calorimeter test results indicate that Li‐Ph‐POSS endows the matrix good fire resistance. Three weight percent Li‐Ph‐POSS makes the heat release rate (HRR) decline by 32.4% compared with the pure VER. Besides, 3 wt% Li‐Ph‐POSS performs best on smoke suppression and declines the release of CO due to good char‐forming effect of Li‐Ph‐POSS. The improvement of mechanical property and the slightly improved glass transition temperature (Tg) of VER composites confirmed the excellent compatibility between Li‐Ph‐POSS and the matrix. The flame retardant mechanism is revealed by Thermogravimetric coupled with Fourier transform infrared analysis, scanning electron microscopy, and X‐ray photoelectron spectroscopy analysis in detail. The work provides an optional method to prepare flame retarded VER with excellent mechanical properties.

Thermally exfoliated π–π stacked blistered graphene oxide as efficient flame retardant soft nano-bundles for vinyl ester resin composites

In this article, we synthesized thermally exfoliated blistered graphene oxide (BGO) soft nano bundles from graphene oxide (GO) by a thermal heating method.

Investigations on Mechanical Properties of Basalt Powder filled Vinyl Ester Composites

The current research work deals with the addition of basalt powder on the characteristics of vinyl ester resin composites. The vinyl ester was modified by basalt powder in the amount of 5%, 10% and 15% by weight. The impact of basalt powder on the performance, such as tensile strength and flexural strength was analyzed. The consequence of powder addition on the impact strength of the fabricated materials was also examined. From the results obtained the basalt powder has an encouraging outcome on the strength of the fabricated composites.

Investigation on low-velocity impact and interfacial bonding properties of weft-knitted UHMWPE reinforced composites

In this study, low-velocity impact and interfacial bonding properties of weft-knitted ultra-high-molecular-weight-polyethylene (UHMWPE) filaments reinforced epoxy resin and vinyl ester resin composites were investigated. UHMWPE filament yarns of 600 D were applied to fabricate three weft-knitted structures of plain stitch, interlock air space stitch and swiss double pique. Vacuum-assisted resin infusion (VARI) technology was utilized to combine resin and fabric to form inter-ply hybrid rigid composites. The basic mechanics, impact resistance and puncture performance of the hybrid composites were evaluated and their interfacial bonding was analyzed. It was revealed that composites with interlock air space stitch reinforcement exhibited the highest mechanical properties and puncture resistance. Under the same weft-knitted reinforcement, the tensile and flexural properties of the epoxy matrix composites were better than vinyl ester matrix composites. However, their low-velocity impact resistance was a bit inferior. The interfacial bonding ability between vinyl ester resin and weft knitting structure reinforcement was stronger because of the similar material structure between resin and reinforcement. This process is important for determining the optimum bonding method to achieve extensive application and improve the shelf life of UHMWPE composites.

Mechanical and flame‐retardant properties and thermal decomposition of vinyl ester resin modified by different phenyl silsesquioxanes

The mechanical properties and fire resistance of vinyl ester resin (VER) composites containing cage‐shaped octaphenyl silsesquioxane (OPS), incompletely cage‐shaped phenyl silsesquioxane (PhT7POSS), and ladder‐shaped phenyl silsesquioxane (PPSQ) were investigated. The POSS structure and dispersion have a great influence on the mechanical properties, thermal stability, and decomposition process of VER composites. The bending strength at break and modulus of the VER‐POSS composites were enhanced obviously, especially for VER‐PPSQ composite and VER‐OPS composite, respectively. In addition, PhT7POSS‐based VER composites revealed the lower values of the peak heat release rate, total heat release, and total smoke release in cone calorimetry tests due to the formation of dense carbon/silica protective layers that acted as a barrier to heat and mass transfer. Moreover, the flame‐retardant mechanisms of condensed phase and gas phase were also investigated in detail. These results illustrate VERs modified by OPS, PhT7POSS, and PPSQ are providing an applicable method to fabricate the composites with excellent flame‐retardant and mechanical properties.

Simultaneous effects of silanized coal fly ash and nano/micro glass fiber on fracture toughness and mechanical properties of carbon fiber‐reinforced vinyl ester resin composites

In this study, the simultaneous effects of both silanized coal fly ash (S‐CFA) and nano/micro glass fiber (nGF) on fracture toughness and mechanical properties of vinyl ester (VE) resin filled with carbon fiber‐based composite materials were investigated. The CFA was treated with (3‐trimethoxysilyl) propyl methacrylate to introduce the methacryloxy groups into the surface of CFA, and was confirmed by using FTIR technique. The nGF and S‐CFA with different weight ratios were well mixed with VE resin by using of high‐speed mechanical stirrer, and ultrasonic technique before using as matrices for fabrication of carbon fiber‐based composite materials via sheet molding compound (SMC) method and hot curing processing. Many characteristics of both cured VE resin composites and carbon fiber‐based composite were examined such as mechanical properties, fracture toughness, and morphology. The results showed that by adding of both 0.1 wt% nGF and 1 wt% S‐CFA into VE resin the tensile strength, tensile modulus, flexural strength, KIC, impact strength as well as the Mode I interlaminar fracture toughness (GIC) of VE composites and carbon fiber based composites get optimum values and increased about 61.39%; 39.83%; 36.21%; 103.1%; 81.79%; 48.61%, respectively when compared with pristine materials. POLYM. ENG. SCI., 59:584–591, 2019. © 2018 Society of Plastics Engineers

Study of thermo-kinetic properties of graphite micro-platelet-enriched vinyl ester composites

In this study, graphite-enriched vinyl ester resin (GVER) composites were prepared with 1, 3 and 5% of graphite micro-platelets (GMPs) to investigate thermo-mechanical and thermo-kinetic properties of composites. The thermal degradation behavior of GVER composites has been studied by thermo-gravimetric analysis under non-isothermal conditions in inert nitrogen atmosphere. Different iso-conversional methods such as Kissinger, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Tang method were applied for this study. The apparent activation energy (E a) calculated from Kissinger’s method was found to be increased from 117.2 (neat vinyl ester) to 147.3, 150.5 and 155.8 kJ mol−1 for composites containing 1, 3 and 5% GMPs, respectively. The elastic modulus values were found to be increased 83.8, 107 and 71% for composites containing 1, 3 and 5% GMPs, respectively. The glass transition temperature values were increased 23.8% for 1% GMPs and 21.1% for 3 and 5% GMPs.

Enhancement of interface performance between shape memory alloy fiber and polymer matrix using silane coupling agent KH550 and Al2O3 nanoparticles

The interface performance of nickel‐titanium (Ni‐Ti) shape memory alloy (SMA) fiber reinforced vinyl ester resin composites was investigated in this work. All the SMA fibers were pre‐treated with H2SO4 and NaOH solution. The fiber surfaces were coated with Al2O3 nanoparticles and silane coupling agent KH550. For comparison, two groups of SMA fibers were coated only with the silane coupling agent or the nanoparticles. Furthermore, the effect of the nanoparticle content on the interface performance of the composites was investigated for Al2O3 nanoparticle contents ranging from 1 wt% to 4 wt%. Scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX) were used to study the effect of the surface modifications. The results demonstrate that all the modified methods enhance the interface strength of the SMA/vinyl ester resin, but samples with SMA fibers coated with both the silane coupling agent and 3 wt% Al2O3 nanoparticles have the best interface performance. SEM observations show that the dispersion of nanoparticles increases when the silane coupling agent is added to the composites. POLYM. COMPOS., 39:3040–3047, 2018. © 2017 Society of Plastics Engineers

The effect of alkaline treatment on their properties of Jute fiber mat and its vinyl ester composites

The untreated jute fibre mat has the affinity for the absorption of moisture, resulting in increase in wettability and the thickness of the fiber. The diameter of the weaving thread diameter is around 1.24 -1.25mm. Due to moisture the bonding between the fibers and matrix are poor and hydrophobic matrices weight is more. So it is necessary to reduce the moisture content by giving the alkali treatment solution taken as pre-treated using NaOH solution. At different exposure times 0,1,2,3,4,5,6 and 7hr dried in hot air oven temperature 100°C and kept at 2days room in temperature 30°C.The untreated and treated jute fiber mat were used as reinforcing agent of vinyl ester resin composites by vacuum bag method with a number of 4plies laminate prepared in the ratio of 60:40. The effect of the stacking sequence is in the form of unidirectional long fibers or randomly short fiber. The alkali treatment on the static mechanical properties was evaluated showing that the higher moduli in comparison to the neat resin. The strength properties, only the composite reinforced with unidirectional layers show higher strength than the plain resin. Higher concentration alkali treatment showed increased improvement of fiber mat matrix compatibility. The degree crystallanity and other properties determined by X-ray diffraction, DSC analysis SEM. By conducting all the test shows the better fiber matrix interface adhesion caused due to the fiber surface treatment by alkali.

Wear Performance Forecasting of Chopped Fiber–Reinforced Polymer Composites: A New Approach Using Dimensional Analysis

ABSTRACTSolid particle erosion of polymer matrix composites is a complex process in which wear occurs from the target surface by impingement of rigid sand particles in an air medium. The rate of material removal (RMR), also referred to as the erosion rate, mainly depends on target material parameters and the erosion conditions such as impact angle, impact velocity, and erodent size. A new semi-empirical model for prediction of the erosion rate of polymer matrix composites has been developed using a dimensional analysis technique based on Buckingham's π theorem. The predictive model analytically rests upon parameters related to chopped glass fiber composites, erodent (target material properties), and operating variables that mainly affect the erosion process of chopped glass fiber–vinyl ester resin composites. The forecasting ability of the predictive model has been assessed and verified by experimental investigations for chopped glass fiber–reinforced vinyl ester resin (VGF) composites. Validation of the theoretical erosion rates obtained from the predictive model showed that they were in good agreement with the experimentally determined erosion rates, where the average error range was estimated to be ∼10 to ∼20%.