Resin Viscosity Research Articles

Synthesis and Characterization of Novel Star-Shaped Itaconic Acid Based Thermosetting Resins

A star-shaped thermoset resin was synthesized by direct condensation reaction of itaconic acid and glycerol (star-Ita.Gly). In order to decrease the viscosity of the resin, the carboxyl groups of the oligomers were reacted with ethanol (Tstar-Ita.Gly). Chemical structures of the resins were studied by 1H and 13C NMR and Fourier-transform infrared spectroscopy (FT-IR). The curing process was optimized by studying the residual exotherms during the curing process. Thermomechanical properties of the cured samples were studied by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Thermogravimetric analyses (TGA) were also carried out on both treated and pure resins to study the thermal stability of the cured samples. The viscosity of both resins were measured at different temperatures and different stress levels. Water adsorption tests were also carried out to check the water absorption properties of Tstar-Ita.Gly’s cured samples. The viscosity of the star-Ita.Gly was 154.9 Pa s at room temperature which dropped to 1.8 Pa s upon increasing the temperature to 70 °C. The viscosity of the Tstar-Ita.Gly resin was 0.35 Pa s at room temperature, and 0.04 Pa s at 70 °C. The glass temperature (Tg) of the alcohol-treated resin was 122 °C. Fully biobased content and inexpensive raw materials, biodegradability, very good thermomechanical and comparably very promising rheological properties and processability along with good thermal stability are of advantages of the synthesized resin which make the resin comparable with other thermosetting systems as well as the commercial unsaturated polyester resins.

Digital light processing 3D printing of conductive complex structures

3D printing has gained significant research interest recently for directly manufacturing 3D components and structures for use in a variety of applications. In this paper, a digital light processing (DLP®) based 3D printing technique was explored to manufacture electrically conductive objects of polymer nanocomposites. Here, the ink was made of a mixture of photocurable resin with multi-walled carbon nanotubes (MWCNTs). The concentrations of MWCNT as well as the printing parameters were investigated to yield optimal conductivity and printing quality. We found that 0.3wt% loading of MWCNT in the resin matrix can provide the maximum electrical conductivity of 0.027S/m under the resin viscosity limit that allows high printing quality. With electric conductivity, the printed MWCNT nanocomposites can be used as smart materials and structures with strain sensitivity and shape memory effect. We demonstrate that the printed conductive complex structures as hollow capacitive sensor, electrically activated shape memory composites, stretchable circuits, showing the versatility of DLP® 3D printing for conductive complex structures. In addition, mechanical tests showed that the addition of MWCNT could slightly increase the modulus and ultimate tensile stress while decreasing slightly the ultimate stretch, indicating that the new functionality is not obtained at the price of sacrificing mechanical properties.

Resin Viscosity Influence on Fiber Compaction in Tapered Resin Injection Pultrusion Manufacturing

Viscosity of the liquid resin effects the chemical and mechanical properties of the pultruded composite. In resin injection pultrusion manufacturing the liquid resin is injected into a specially designed tapered injection chamber through the injection slots present on top and bottom of the chamber. The resin is injected at a pressure so as to completely wetout the fiber reinforcements inside the tapered injection chamber. As the resin penetrates through the fibers, the resin also pushes the fibers away from the wall towards the center of chamber causing compaction of the fiber reinforcements. The fibers are squeezed together due to compaction, making resin penetration more difficult; thus higher resin injection pressures are required to efficaciously penetrate through the compacted fibers and achieve complete wetout. The impact of resin viscosity on resin flow, fiber compaction, wetout and on the final product is further discussed. Injection chamber design predominantly effects the resin flow inside the chamber and the minimum injection pressure required to completely wet the fibers. Therefore, a desirable injection chamber design is such that wetout occurs at lower injection pressures and at low internal pressures inside the injection chamber.

Preparation of 3DPSL-1 Type Photosensitive Resin and Study on Its Properties

3DPSL-1(3D printing stereolithography No.1) type photosensitive resin was prepared with 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate (ERL-4221), bisphenol A type epoxy diacrylate (DH-306), tripropylene glycol diacrylate (TPGDA), Diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate(TDE-85), triethylene glycol divinyl ether (DVE-3), benzil dimethyl ketal (Irgacure651) and a mixture of triarylsulfonium hexafluoroantimonate salts (UVI-6976) as raw materials. Some properties of the photosensitive resin were investigated. The viscosity of the photosensitive resin at 30 ℃ was 355mPa.S, the glass transition temperature (Tg) of the UV-cured specimen was 52 ℃, and the weight loss of the UV-cured specimen at 200 ℃ was less than 4%. The photosensitive resin and its UV-cured specimen were also characterized by infrared (IR).

Simulation and experimental validation of the effect of material and processing parameters on the injection stage of compression resin transfer molding

The effects of gap thickness, injection flow rate, overflow percentage, initial fiber content, and resin viscosity on the resin distribution at the end of the injection stage of compression resin transfer molding have been studied. Experimental results have shown that in all the cases, a certain amount of resin penetrates the preform, contrary to the extended hypothesis that the resin flows exclusively through the gap. Furthermore, resin distribution is not homogeneous and the penetration depth varies depending on the distance from the injection point, being deeper near the inlet point. Simulation results based on the quantitative analysis of the amount of resin penetrating into the preform demonstrates that the most influent parameters are the initial fiber content, the gap percentage and the overflow percentage. In fact, the ratio between the permeability of the gap and the preform (r) governs the tendency of the resin to flow through the gap or to penetrate into the preform. Increasing r reduces the amount of resin which penetrates into the preform, but there is an upper asymptotic limit from which no differences are noted. Finally, simulation results have also demonstrated that the preform compression can be neglected during the injection stage, as the pressure into the preform is low. POLYM. COMPOS., 39:4333–4340, 2018. © 2017 Society of Plastics Engineers

Effect of bio-alkyd resin oil content and viscosity on the adhesion of EPDM to polyester fabric

Three types of bio-alkyd resins varies in their oil content and viscosity were added to EPDM rubber mix loaded by three bonding system consisting of Hexamethylenetetramine, Resorcinol and Hydrated silica (HRH). The mixes were charged by certain amount of thermal carbon black. Rubber dough was spread on polyester sheet fabric. The peel strength was used to measure the adhesion strength. The rubber-proofed fabric subjected to UV irradiation at different period of times. The dielectric constant, volume resistivity, thermal stability, water and air permeability of the various rubber coated fabric were examined. The addition of the bio-alkyd resin improved the various mechanical and physical properties of the rubber coated fabric materials. The suggested mechanism of bio-alkyd resin between EPDM and polyester fabric was also studied.

Smoothed particle hydrodynamics simulation of dual-scale flow during resin transfer molding

Smoothed particle hydrodynamics is a Lagrangian meshless particle method, which can be applied to the modelling of complex flow in molding simulation. In the present work, firstly, by comparing the results of smoothed particle hydrodynamics and volume-of-fluid simulation for micro-scale flow within the fiber tow, the feasibility of smoothed particle hydrodynamics to simulate the flow in porous media was demonstrated. Secondly, the dual-scale flow in the dual-scale fiber preform during resin transfer molding was investigated using smoothed particle hydrodynamics simulation. The resin melt was modeled as fluid particles, and the fiber preform was regarded as dual-scale porous media depicted by fixed boundary particles. The smoothed particle hydrodynamics simulation described the evolution of the flow and the formation of the void. The effects of several factors on the size of the void were also studied. The results showed that the void size increased with the increase of vertical inter-tow dimension while decreased with the increasing resin velocity and viscosity.

Investigation of epoxy matrix viscosity in the initial stage of its formation

The present study includes experimental investigations of rheological properties of the epoxy composite matrix based on epoxy resin L and hardener EPH 161. It is shown that the temperature dependences of the oligomer viscosity and the hardener can be satisfactorily described by the Arrhenius equation. Dependence of epoxy resin viscosity on temperature and volume concentration of the hardener at the initial stage of the polymerization process is investigated. It is shown that the experimental results can be generalized with one universal dependence of concentration and temperature.

Influence of MWCNTs addition on mechanical and thermal behaviour of epoxy/kenaf multi-scale nanocomposite

This research was conducted to develop kenaf reinforced epoxy/MWCNTs multi-scale composite using kenaf fibre and MWCNTs as the reinforcement in epoxy as the hosted matrix. The composites were produced by using a combination of hand lay-up and vacuum bagging process. The selection of optimum composition of epoxy-MWCNTs is based on the MWCNTs loading and the resulted mixture viscosity. Lower resin viscosity is required to allow good wetting and interaction between matrix and filler, which will yielded superior final performance of the fabricated composites. Therefore, different loading of MWCNTs (0.0 wt. %, 0.5 wt. %, 1.0 wt. %, 3.0 wt. %, 5.0 wt. %, 7.0 wt. %) were used to investigate the mechanical and thermal properties of the composites. As a result, the epoxy/kenaf/MWCNTs multi-scale composite at 1.0 wt. % of MWCNTs addition had yielded substantial improvement by 15.54 % in tensile strength and 90.54 % in fracture toughness. Besides, the fracture surface morphology of the selected samples were analysed via scanning electron microscopy (SEM) observation to further support the reinforcement characteristic of epoxy/kenaf/MWCNTs multi-scale composite.

A simplified chemorheological model of viscosity evolution for solvent containing resol resin in RTM process

ABSTRACTThe solvent content‐dependent chemorheology of the solvent containing resol resin for resin transfer molding (RTM) was investigated. The curing behavior of the resol resin was studied by in situ Fourier transform infrared spectroscopy together with rheology tests. The chemorheological behavior of resol resins with a series of solvent contents was measured under isothermal conditions. The four parameters of empirical dual‐Arrhenius equation regarding isothermal resin viscosity and reaction rate constant were found to be functions of the solvent content. A simplified chemorheological model involving only three parameters of curing temperature, time, and solvent content was first established to facilely describe the viscosity during precuring process. The simulated viscosity results during isothermal curing process agreed well with the experimental data which shows the simplified chemorheological model can be utilized to describe the viscosity evolution and offer guidance for optimizing the injection process and improving the design flexibility of RTM process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45282.

Impact of the spatial distribution of high content of carbon nanotubes on the electrical conductivity of glass fiber fabrics/epoxy composites fabricated by RTM technique

To incorporate high content of carbon nanotubes (CNTs) into a polymer matrix is greatly desired to obtain highly conductive structural composites, but it is difficult in practice to be realized due to increased resin viscosity along with dispersion difficulty. In this study, we demonstrate the production of carbon nanotubes (CNTs)-integrated glass fiber fabrics (GFF)/epoxy composites by resin transfer molding (RTM), in which the mass fraction of CNTs on GFF varies from 0 to as high as 8 wt%. Three different methods were compared to load CNTs on GFFs, which include one-step in-situ CVD growth, catalyst pre-deposited two-step CVD growth and CNT suspension casting. For each type of CNTs-GFFs, a series of RTM composites with varied CNT contents were prepared. The impact of the CNT spatial distribution on the composite in-plane and through-plane electrical conductivities was compared at different CNT loading levels by subtracting contact resistance between the sample and the electrodes. It was found that the composites reinforced with one-step CVD-grown CNTs/GFFs show the best electrical conductivity among the three types of the composites studied, due to good CNT structure and their alignment on GF surface. A detailed discussion was made on the composite conductive behavior with the different CNTs-GFFs. This study helps to provide insight to the production of high-performance structural composites functionalized with high contents of CNTs at low cost.

EFFECT OF LUTING AGENT VISCOSITY ON BOND STRENGTH AND MARGINAL GAB OF CERAMIC OCCLUSAL VENEER RESTORATIONS

Objectives: The purpose of this study was to evaluate the effect of viscosity of composite resin as luting agent before and after heating on bond strength and marginal gab of two CAD/CAM posterior ceramic occlusal veneers restorations. The effect of heating on the flow of composite resin was determined.Materials and Methods: 20 e. max and vita enamic discs (4x4x2mm) was prepared (Isometric 4000 micro saw Buhler USA) and cemented to grind enamel surface of mounted molars groups (heated and non-heated composite )according to manufacturer instructions and bond strength was measured by testing machine (Model 3345; Instron Industrial Products, Norwood, USA). also 20 extracted human premolars was prepared for occlusal veneers and the constructed e. max and vita enamic CAD/CAM was bonded using flowable composite resin cement before and after heating then marginal gap was measured before and after thermo-mechanical aging .The interface of debonded surfaces was recorded. Internal gap was measured before cementation by a replica technique. Flow of composite resin was measured before and after heating using compressed composite discs (ANSIADA Specification No. 57 -1993). The data was tabulated and analyzed statistically.Results: It was found that heating affected resin flow significantly (p=0.0003 non-heated resin mean value). Effect of heating of composite resin; totally it was found that heated composite resin affected marginal gap significantly (p=0.0284 heated resin mean value). Regardless to ceramic material groups, it was found that heated composite resin affected bond strength significantly (p=0.0141 non-heated resin). Interaction between variables was not done coz the F value of ANOVA test showed non-significant interaction (p=0.2611>0.05)Conclusions: Heating of flowable composite resin as luting before cementation improve the flow characteristics of composite resin, increase the bond strength of occlusal veneers, and reduce the marginal gab.

Formability of CFRTP prepreg considering heat transfer

Carbon-fiber-reinforced thermoplastic (CFRTP) laminate undergoes large deformations and slip between each layer during the prepreg compression forming (PCF) process. Particularly, the formability of CFRTPs varies for each layer as a result of the temperature difference during heat transfer between tool and laminate because of the viscosity of resin. These behaviors affect the final product quality and may create related defects such as wrinkling, and delamination. The objective of this study is to predict the defects by using the finite element method (FEM) considering the heat transfer according to the forming temperature. The bias extension were performed to measure the shrar properties (which are dependent on temperature) at 150°C, 170°C, and 190°C. In addition, the heat transfer coefficient between tool and laminate was measured using the inverse analysis method. The effect of tool temperature on formability of CFRTP prepreg was investigated by FE analysis of the hemispherical punch drawing test. To verify the reliability of the FE analysis, hemispherical punch drawing experiments were performed under the same conditions as those of the FE analysis. The deformed shear angle of CFRTP specimens in the experiment were compared with simulation results. Finally, the temperatures were evaluated to investigate the effects of temperature variation caused by heat transfer.

Applying CFD in Manufacturing of Polymer Composite Reinforced with Shape Memory Alloy via Resin Transfer Molding Process

This paper aims to study the manufacturing process of polymer composite reinforced with shape memory metal alloys by RTM process using ANSYS CFX ® software. The mathematical modeling consists of mass and momentum conservation equations applied to a metal mold with dimensions 0.3 × 0.3 × 0.002 m³ containing ten NiTi alloy wires 0.0005 m diameter. Results of the flow front position of the resin (polyester resin mixed with calcium carbonate particles), pressure, streamlines and resin velocity fields during the process are presented and discussed. We conclude that the addition of calcium carbonate resulted in increased resin viscosity and greater inlet pressure obtained at the entrance of the mold which resulted in short time to full fill the mold and the highest pressures at the NiTi alloy wire surface were obtained in the central region and near the mold entrance.

Effect of Urea-Formaldehyde Resin Adhesive Viscosity on Plywood Adhesion

This work was conducted to investigate on the effect of urea-formaldehyde (UF) resin viscosity on plywood adhesion. The viscosity of UF resin was controlled either by adjusting the condensation reaction during its synthesis to obtain different target viscosities (100, 200 and 300 mPa.s) at two levels of formaldehyde/urea (F/U) mole ratios (1.0 and 1.2) or by adding different amounts (10, 20 and 30%) of wheat flour into the resins for the manufacture of plywood. When the viscosity of UF resin increased by the condensation reaction, the adhesion strength of plywood bonded with UF resin of 1.2 F/U mole ratio consistently increased, while those bonded with the 1.0 F/U mole ratio resin slightly decreased, suggesting a difference in the adhesion in plywood. However, the adhesion strength of plywood decreased as the viscosity increased by adding wheat flour, regardless of F/U mole ratio. The manipulation of UF resin viscosity by adjusting the condensation reaction was much more efficient than by adding wheat flour in improving the adhesion performance of plywood. These results indicated that a way of controlling the viscosity of UF resin adhesives has a great influence to their adhesion in plywood.

Replacement of styrene with acrylated epoxidized soybean oil in an unsaturated polyester resin from propylene glycol and maleic anhydride

ABSTRACTA nonvolatile, vegetable‐oil based chemical, acrylated epoxidized soybean oil (AESO) was investigated as a replacement of volatile and toxic styrene in one of commercial UPE resins styrene‐(PG‐MA) that is a mixture of styrene and a UPE plastic from propylene glycol and maleic anhydride (PG‐MA). Neither AESO nor PG‐MA was capable of forming a strong matrix, respectively, for glass fiber‐reinforced composites. However, a mixture of AESO and PG‐MA resulted in glass fiber‐reinforced AESO‐(PG‐MA) composites that were comparable or even superior to those from styrene‐(PG‐MA) in terms of the flexural and tensile properties. Effects of AESO contents on the mechanical and viscoelastic properties of the glass fiber‐reinforced AESO‐(PG‐MA) composites were investigated. Resin viscosity and resin pot life as a function of temperature were studied. The curing mechanism of the AESO‐(PG‐MA) resins is also discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45056.

Effects of Compounded Curing Agents on Properties and Performance of Urea Formaldehyde Resin

The effects of three compounded curing agents on the properties and performance of the urea-formaldehyde (UF) resin were investigated in this study. The compounded curing agents were prepared by mixing ammonium chloride with hexamethylenetetramine, citric acid, and oxalic acid respectively at a ratio of 1:1, named N-H, N–CA, and N–OA, respectively. The curing process, crystallinity, and physical properties were measured, and the three-ply plywood was fabricated to measure its prepress strength, wet shear strength, and formaldehyde emission. Results showed that the compounded curing agents N–CA and N–OA enhanced the initial viscosity, crosslinking density and thermal stability of UF resin. Additionally, the prepress strength of the plywood bonded by UF resin with N–CA and N–OA increased by 82 and 111% respectively compared to the UF resin with NH4Cl, and the wet shear strength increased by 14 and 16%, the formaldehyde emission decreased by 19 and 42% respectively. However, owing to the short pot-life of these curing agent limited their storage time, the curing agents N–CA and N–OA should be applied to fabricate plywood in winter for obtaining a better bond strength and a lower formaldehyde emission. While the UF resin with N–HT showed a suitable pot-life, so it could be applied to fabricate plywood in summer for long time storage and avoiding procuring problem.

Improvement in skin–core adhesion of multiwalled carbon nanotubes modified carbon fiber prepreg/Nomex honeycomb sandwich composites

An experimental investigation on the sandwich composites composed of the carbon fiber face sheets and Nomex honeycomb core has been carried out in this study. Multiwalled carbon nanotubes were added into the matrix of prepreg for converting the traditional pure resin adhesive fillet to composites. Resin viscosity was measured to evaluate the effect of the additive amount of multiwalled carbon nanotubes on the rheological properties. The size of adhesive fillet was obtained from the optical microscopy to assess the forming quality. Climbing drum peel test and edgewise compression test were employed for the mechanical assessment. The results showed that the addition of multiwalled carbon nanotubes reinforcement to epoxy resin in the prepreg was very effective in improving the skin–core adhesion. The peel load and peel energy release rate as well as the edgewise compressive strength and edgewise compressive modulus of the sandwich composites varied with different magnitudes due to the additive amount of multiwalled carbon nanotubes. Reinforcing mechanism of the adhesive fillet with multiwalled carbon nanotubes reinforcement was discussed on the basis of the fractographic observations by scanning electron microscopy.

Dissolvable thermoplastic interleaves for carbon nanotube localization in carbon/epoxy laminates with integrated damage sensing capabilities

A nano-engineered hierarchical composite with localized toughening and integrated damage sensing capabilities is described. Thermoplastic phenoxy interleaves which dissolve in epoxy resin upon heating and subsequently phase separate upon curing were employed as carrier films for localized deposition of carbon nanotubes in carbon fibre–reinforced plastics, avoiding filtration of carbon nanotubes during liquid resin infusion. Interlaminar fracture toughness was improved compared to reference epoxy-based laminates, while the introduced carbon nanotube network was utilized for in situ damage sensing purposes. Using this technology based on dissolvable thermoplastic carrier films, nanofillers can be easily introduced into fibre-reinforced composites at desired regions while simultaneously avoiding typical nanofiller drawbacks such as filtering or increased resin viscosity.

Dynamics of particle chain formation in a liquid polymer under ac electric field: modeling and experiments

Polymer/ceramic composite materials are of great interest for their many potential applications because of their ability to combine at least two properties of the constitutive elements: particles and matrix. In most cases, such enhanced properties are required only in one direction. Orthotropic materials can be elaborated by applying an ac electric field to form particle chain structures in the direction of the electric field due to the dielectrophoretic interactions affecting the particles. However, there is still a lack in the understanding of the impact of the structures on the properties of the material. The aim of this study is to propose a predictive model for the evolution of the permittivity during the chain formation, by including micro- and macroscopic phenomena. The chaining model is based on dipole–dipole interactions and the dielectric permittivity is computed through a finite element method. In parallel, an experimental study is performed with online permittivity measurements of composites during chaining. The developed model is able to predict the experimental results from 1 vol% while taking into account parameters such as the resin viscosity and permittivity and the transient evolution of the applied electric field. The formation of particle chains inside a material has applications in many domains such as electrorheological fluids, anisotropic composites, self-recovery materials etc. Such a developed model is a valuable tool for the tailoring of materials.