Carboxyl-terminated Butadiene Acrylonitrile Copolymer Research Articles

Study of mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites

Abstract This article aimed to compare various mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites. Graphene nanoplatelets (GnPs) and halloysite nanotubes (HNTs) were used as fillers at different concentrations. The studied fillers were dispersed in the epoxy resin matrices. Elastic–plastic mechanical behavior modulation was observed utilizing the fillers’ nanoparticles and carboxyl-terminated butadiene–acrylonitrile copolymer rubber-modified epoxy resin. The hypothesis of the possible preceding inter-particle gliding of the individual GnPs in the complex resin nanocomposite matrix during mechanical testings was also confirmed. Increased ductility (elongation at break increased from 0.33 mm [neat matrix] to 0.46 mm [1 wt% GnPs] [39% increase]) and plasticity of the GnP nanocomposite samples were observed. In contrast, the decreasing mechanical stiffness as reflected in the decreased Young’s modulus of elasticity (from 3.4 to 2.7 GPa [20% decrease]) was found for the epoxy/HNT nanocomposites. The obtained dynamic stiffness of the investigated nanocomposites confirmed the complexity of the mechanical response of the studied material systems as a combination of the ductile and brittle phenomena.

Study on the synthetic mechanism of monodispersed polystyrene-nickel composite microspheres and its application in facile synthesis of epoxy resin-based anisotropic conductive adhesives

Monodispersed polystyrene-nickel (PS-Ni) composite microspheres were used to enhance the conductivity of epoxy-based anisotropic conductive adhesive (ACA) for the first time. Specifically designed PS-Ni composite microspheres were used as conductive elements to construct anisotropic conductive arrays. The surface microstructure and morphology of the prepared PS-Ni composite microspheres were tuned by controlling the implementation method of electroless plating and concentration of Ni precursor. The structural composition, thermal properties, and electrical properties of PS-Ni composite microspheres were analyzed. In addition, diglycidyl ether of bisphenol-A (DGEBA) epoxy resin and low molecular weight polyamide resin were used as the matrix resin and curing agent, respectively. The optimal process parameters were employed and predicted based on the curing kinetics. A simple strategy was developed for the preparation of anisotropic conductive binders (viz. PS-Ni/EP-ACAs) via physical doping by addition of terminal carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer and additives. PS-Ni/EP-ACAs exhibited satisfactory anisotropic electrical properties in fabricated components due to submicron structures composed of PS-Ni composite microspheres with excellent integrated properties in the anisotropic conducting array. Therefore, the theoretical concept and fabrication mean proposed in this study showed great potential and practical application in large-scale ACAs preparation.

Comparative Study on the Impact Wedge-Peel Performance of Epoxy-Based Structural Adhesives Modified with Different Toughening Agents.

Epoxy adhesives are widely used in various industries because of their high heat and chemical resistance, high cohesion, and minimal shrinkage. Recently, epoxy adhesives have been applied in the automotive industry as structural adhesives for lightweight vehicles. However, the brittleness of the epoxy is an obstacle for this application, since the automotive industry requires epoxy-based structural adhesives to have a high level of high-speed impact resistance. Hence, we used phenol-terminated polyurethane (PTPU) as a toughening agent for epoxy adhesives and compared the results with those that were obtained with carboxyl-terminated butadiene acrylonitrile copolymer (CTBN). The high-energy impact resistance of the epoxy adhesives was measured by the impact wedge-peel (IWP) test, and the shear strength was measured by the single lap joint test. As a result, the 20 wt % PTPU-modified epoxy adhesive showed remarkably higher total absorbed energy (25.8 J) during the IWP test and shear strength (32.3 MPa) as compared with the control epoxy adhesive (4.1 J and 20.6 MPa, respectively). In particular, the total absorbed energy of the PTPU-modified epoxy adhesive was much larger than that of the CTBN-modified epoxy adhesive (5.8 J). When more than 10 wt % PTPU was added, the modified epoxy adhesives showed stable crack growth and effectively transferred external stress to the substrate. These results were explained by changes in the glass transition temperature, crosslinking density, and morphology due to the toughening agents.

Investigation of the dynamic mechanical properties of epoxy resins modified with elastomers

Abstract The mechanical and modal properties of epoxy resin reinforced with different content of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) rubber were investigated in this paper with an analytical-experimental identification method. Mechanical tensile tests were conducted for concentrations between 0 and 25wt% of CTBN rubber. The dynamic responses of the epoxy/CTBN rubber composites were measured by vibrating cantilever beam specimens with an impact force through a modal hammer, while the vibratory response was detected through an acceleration transducer. The analytical-experimental transfer function method is utilized for the deduction and therefore comparison of the elasticity modulus of the epoxy/rubber composites. The procedure for the identification of analytical-experimental transfer functions was carried out using a genetic algorithm (GA) by minimizing the difference between the measured response from tests and the calculated response, which is a function of the modal parameters. Both tensile and modal tests have shown, while it was evident from the results that the CTBN composites could absorb greater amounts of strain energy. The modal test results indicate that CTBN rubber particles can improve the damping capacity of the epoxy-based composites. However, it was observed that the stiffness of the epoxy/CTBN rubber composites was dramatically reduced.

A Review on the Matrix Toughness of Thermoplastic Materials

Composite material has attracted increasingly remarked interest over the last few decades and set it apart in its own class due to its distinct properties. This paper is a review on the matrix toughness of thermoplastic polymer composites. Toughness of thermoplastics has been actively studied since the 1980s.the main advantage in using thermoplastics to toughen resins is that their incorporation need not result in important decreases in desirable properties such as modules and yield strengths. However, the predominant criteria for achieving optimum toughness enhancement in the thermoplastic toughening of epoxy resins are still not all that clear from the literature. Epoxy and polyester resins are commonly modified by introducing carboxyl-terminated butadiene-acrylonitrile copolymers (ctbn). A tough elastomeric phase, for example, a silicone rubber with good thermal resistance in a polyimide resin, produced a tough matrix material. It summarizes what the authors believe are the important requirements for good thermoplastic toughening.

The Effect of Pre-Crosslinked CTBN on the Mechanical Properties and Morphology of Epoxy Resin

A novel kind of rubber toughened epoxy was prepared by in situ pre-crosslinking carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) in the epoxy matrix. The in situ pre-crosslinking of CTBN was initiated by BPO, followed by the curing reaction of epoxy to form the final pre-crosslinked CTBN/epoxy composites. Mechanical properties of epoxy are further improved by the incorporation of pre-crosslinked CTBN compared with its traditional CTBN/epoxy counterparts due to the improved interfacial strength between rubber and epoxy. SEM shows that the size of phase separated rubber particles of pre-crosslinked CTBN/epoxy decreases significantly.

A new method to prepare rubber toughened epoxy with high modulus and high impact strength

Although epoxy resins can be substantially toughened by addition of a reactive liquid rubber, the improvement in toughness is inevitably accompanied by a significant loss in elastic modulus and yield strength. This paper presents a novel route for preparing the liquid rubber/epoxy composites with high yield strength, Young׳s modulus and impact strength. By this new method, the epoxy composites with different grades of carboxyl terminated butadiene acrylonitrile copolymer (CTBN) and cured by different curing agents were prepared, and their mechanical properties were characterized. It is found that no matter what grades of CTBN, also regardless of curing agents, the composites prepared by the new method always exhibit much higher impact strength, yield strength and Young׳s modulus than the corresponding traditional composites, proving the new method to be somewhat universal. Especially, some CTBN/epoxy composites exhibit even higher yield strength and Young׳s modulus than that of pure epoxy.

Toughening of dicyandiamide-cured DGEBA-based epoxy resins by CTBN liquid rubber

Toughening of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin with liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer has been investigated. For this purpose six blend samples were prepared by mixing DGEBA with different concentrations of CTBN from 0 to 25 phr with an increment of 5 phr. The samples were cured with dicyandiamide curing agent accelerated by Monuron. The reactions between oxirane groups of DGEBA and carboxyl groups of CTBN were followed by Fourier-transform infrared (FTIR) spectroscopy. Tensile, impact, fracture toughness and dynamic mechanical analysis of neat as well as the modified epoxies have been studied to observe the effect of CTBN modification. The tensile strength of the blend systems increased by 26 % when 5 phr CTBN was added, and it remained almost unchanged up to 15 phr of CTBN. The elongation-at-break and Izod notched impact strength increased significantly, whereas tensile modulus decreased gradually upon the addition of CTBN. The maximum toughness of the prepared samples was achieved at optimum concentration of 15 phr of CTBN, whereas the fracture toughness (KIC) remained stable for all blend compositions of more than 10 phr of CTBN. The glass transition temperature (Tg) of the epoxy resin significantly increased (11.3 °C) upon the inclusion of 25 phr of CTBN. Fractured surfaces of tensile test samples have been studied by scanning electron microscopic analysis. This latter test showed a two-phase morphology where the rubber particles were distributed in the epoxy resin with a tendency towards co-continuous phase upon the inclusion of 25 phr of CTBN.

Effect of hybridization of liquid rubber and nanosilica particles on the morphology, mechanical properties, and fracture toughness of epoxy composites

A liquid carboxyl-terminated butadiene–acrylonitrile copolymer (CTBN) and SiO2 particles in nanosize were used to modify epoxy, and binary CTBN/epoxy composites and ternary CTBN/SiO2/epoxy composites were prepared using piperidine as curing agent. The morphologies of the composites were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), and it is indicated that the size of CTBN particles increases with CTBN content in the binary composites, however, the CTBN particle size decreases with the content of nanosilica in the ternary composites. The effects of CTBN and nanosilica particles on the mechanical and fracture toughness of the composites were also investigated, it is shown that the tensile mechanical properties of the binary CTBN-modified epoxy composites can be further improved by addition of nanosilica particles, moreover, obvious improvement in fracture toughness of epoxy can be achieved by hybridization of liquid CTBN rubber and nanosilica particles. The morphologies of the fractured surface of the composites in compact tension tests were explored attentively by field emission SEM (FE-SEM), it is found that different zones (pre-crack, stable crack propagation, and fast crack zones) on the fractured surface can be obviously discriminated, and the toughening mechanism is mainly related to the stable crack propagation zone. The cavitation of the rubber particles and subsequent void growth by matrix shear deformation are the main toughening mechanisms in both binary and ternary composites.

Damage detection of rubber toughened nanocomposites in the fracture process zone using carbon nanotubes

A detailed experimental study is conducted using multi-walled carbon nanotubes (MWCNTs) as a sensory network to understand damage initiation and growth within the process zone of epoxy particulate composites under opening mode fracture loading. Thermoset epoxy resin composites are toughened with three weight fractions of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) rubber (10phr, 20phr and 30phr). Single-edge notch tension (SENT) geometry and far-field tensile loading conditions are used for this study. A modified four-point probe methodology coupled with a high-resolution data acquisition system is employed to capture the electrical response within the process zone of fracture test specimens. For each composite, the damage initiation and growth associated with linear and non-linear deformation is analyzed and discussed with respect to the change in crack tip opening displacement (CTOD). Although the electrical response did not differ qualitatively with the addition of both 10phr and 20phr rubber to epoxy, addition of 30phr of rubber showed a significantly different response both qualitatively and quantitatively. This is the result of several mechanisms such as disentanglement and stretching of epoxy matrix molecules, micro-crack blunting, debonding of rubber particles, void growth and propagation.

1H NMR and 13C NMR Investigation of Microstructures of Carboxyl-Terminated Butadiene Acrylonitrile Rubbers

Two carboxyl-terminated butadiene acrylonitrile (CTBN) copolymers, named Lan-1 and Lan-2, were synthesized by solution radical polymerization. They had similar physical properties with the commercial sample Hycar1300×13, but had higher viscosity. The results of 1H NMR and 13C NMR revealed that Hycar1300×13 had more branched chains and more acrylonitrile-1,4 butadiene bonded units, but had lower acrylonitrile–acrylonitrile and acrylonitrile-1,2 butadiene bonded units, compared with Lan-1 and Lan-2. This improved the flexibility of the molecular chains of Hycar1300×13, and correspondingly decreased its viscosity.

Effects of Rubber Addition to an Epoxy Resin and Its Fiber Glass-Reinforced Composite

Epoxy resins are considered as one of the most important class of thermosetting polymers and find extensive use in various fields. However, these materials are characterized by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins. In this work, samples of epoxy resin diglycidyl ether of bisphenol-A and fiber glass-reinforced composite of this polymer with and without liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer were prepared to assess the effect of CTBN rubber on the properties of polymeric and composite laminate specimens. The addition of CTBN into the polymeric specimens led to a decrease in the glass transition temperature, fracture stress (from 70.39 to 56.34 MPa), and tensile elasticity modulus (from about 3.51 to 2.65 GPa), accompanied by an increase in elongation (from 2.47 to 5.64%). However, the degradation temperature of the polymeric system was not modified. Infrared analysis evidenced the occurrence of chemical reaction between the two components, and scanning electron microscopy results suggested rubber particles deformation as the prevailing toughening mechanism. The rubber addition in the composite specimens, promoted an increase simultaneous in fracture stress and in elongation at fracture. The elasticity tensile modulus has not changed. This probably results from the increased deformation capacity of the matrix, which prevents its premature cracking, and better adhesion between fibers and matrix observed in the CTBN-modified composite laminates. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers

Effect of CTBN on Properties of Oxide Graphene/Epoxy Resin Composites

The effect of liquid carboxyl terminated butadiene acrylonitrile copolymer (CTBN) on the properties of oxide graphene (OG) /epoxy resin (EP) composite has been studied. The results show that oscillations process can greatly increase the tensile strength, shear strength and hardness of the composites, for the compatibility between the EP and the OG can be greatly improved after oscillations. Infra-red analysis shows that CTBN reacts with EP to form ester group. The tensile strength of the EP decrease, and the elongation at break increase, as more and more CTBN added. The tensile strength of the OG/EP composite is 14.37 MPa, while that of CTBN/OG/EP (15/0.001/100) composite is 4.84 MPa.

The Effect of CTBN Concentrations on the Kinetic Parameters of Decomposition of Blends of Epoxy Resins Modified with Carboxyl-Terminated Liquid Copolymer

Diglycidyl ether of bisphenol—A (DGEBA)—based epoxy resin was blended in the ratio of 3:1 (weight basis) with cycloaliphatic epoxy (CAE) resin. The prepared blend sample was further blended with different weight percentages of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) ranging between 0 and 25 wt% with an interval of 5 wt% and cured with stiochiometric amounts of 4, 4’- diamino diphenyl sulphone (DDS) cure agent. Structural changes during blending were studied by Fourier-transform infra-red (FTIR) spectroscopic analysis. The kinetic parameters, viz., order of decomposition reaction (n), activation energy (E), pre-exponential factor (Z) and rate decomposition constant (k), for the decomposition of the samples were calculated by applying Coats-Redfern equation over thermogravimetric (TG) data. The degradation of each sample followed second-order degradation kinetics, which was calculated by Coats-Redfern equation using best-fit analysis. This was further confirmed by linear regression analysis. The validity of data was checked by t-test statistical analysis. Further, the blend sample had higher initial degradation temperature and activation energy than its respective pure epoxy resin indicating that the CTBN acted as thermal stabilizer for epoxy resin which improved the thermal stability.

Modification of dicyanate ester resin by liquid carboxyl-terminated butadiene acrylonitrile copolymer

Bisphenol A dicyanate ester (BADCy) was modified with liquid carboxyl-terminated butadiene acrylonitrile (LCTBN). The cured BADCy resin was formed through the cyclotrimerization of cyanate functional groups into triazine rings, and there was the chemical reaction between BADCy and LCTBN. Mechanical performance indicated that the introduction of LCTBN into BADCy resin improved the impact strength with maintenance in flexural strength. Scanning electron microscopy (SEM) showed that the pure resin had a smooth glassy fracture surface, whereas cured blends containing LCTBN showed rougher fracture surfaces, and exhibited enhanced impact resistance. The TEM observation showed that the two phases in the cured resins exhibit a good interaction adhesion. Thermograms of BADCy modified with LCTBN showed the little reduction of heat deflection temperature, and a reduction in thermal stability temperature by 30 K. Dynamic mechanical analysis (DMA) showed that the pure BADCy had higher storage modulus ( E′) values than that of the BADCy modified with LCTBN, whereas the loss modulus ( E″) was lower, and that the glass transition temperature (Tg) of modified BADCy was 229 °C and lower than that (249 °C) of pure BADCy resin.

Studies on blends of cycloaliphatic epoxy resin with varying concentrations of carboxyl terminated butadiene acrylonitrile copolymer I: Thermal and morphological properties

Differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) of the blends of cycloaliphatic epoxy (CAE) resin toughened with liquid elastomer such as carboxyl terminated butadiene acrylonitrile copolymer (CTBN) have been carried out. Exothermal heat of reaction due to cross linking of the resin in the presence of diamino diphenyl sulphone (DDS, an amine hardener) showed a decreasing trend with increasing rubber concentration. Enhancement of thermal stability as well as lower mass loss of the epoxy-rubber blends with increasing rubber concentration have been observed in thermogravimetric analysis (TGA). Dynamic mechanical properties reflected a monotonic decrease in the storage modulus (E′) with increasing rubber concentration. The loss modulus (E″) and the loss tangent (tan δ) values, however, showed an increasing trend with rise of temperature up to a maximum (peak) followed by a gradual fall in both cases.

Studies on cardanol-based epoxidized novolac resin and its blends

Cardanol-based novolac-type phenolic resin was synthesized with a mole ratio 1.0:0.5 of cardanol-to-formaldehyde using a dicarboxylic acid catalyst such as succinic acid. The cardanol-based novolac-type phenolic resin may further be modified by epoxidation with epichlorohydrin excess at 393 K in a basic medium to duplicate the performance of such phenolic-type novolacs. Carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) has been studied by various researches with diglycidyl ether of bisphenol-A (DEGBA) epoxy resin and epoxidized phenolic novolac resins. The epoxidized novolac resin was blended with different weight ratios of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) and cured with a stoichiometric amount of polyamine curing agent. The formation of various products during the synthesis of cardanol-based novolac resin, epoxodized novolac resin and blending of epoxidized novolac resin with CTBN has been studied by Fourier-transform infrared (FTIR) spectroscopic analysis. Further, the products were confirmed by a proton nuclear magnetic resonance (1H-NMR) spectroscopic analysis. The number average molecular weight was determined by a gel permeation chromatography (GPC) analysis. The blend sample, having 15 wt % CTBN concentration showed minimum cure time and most thermally stable systems.

Effect of carboxyl‐terminated butadiene acrylonitrile copolymer concentration on mechanical and morphological features of binary blends of nonglycidyl‐type epoxy resins

AbstractBlend samples were prepared by physical blending of nonglycidyl‐type epoxy resin with varying weight ratios of carboxyl‐terminated butadiene acrylonitrile (CTBN) copolymer ranging between 0 and 25 wt%. The blend samples were cured with stoichiometric quantity of diamine. A comparative study of prepared blend samples by Fourier transform infrared (FTIR) spectroscopy showed the modification as a result of chemical reactions between cycloaliphatic epoxy, CTBN, and 4,4′‐diamino diphenyl sulfone. The impact strength of the blend systems increased up to 15 wt% addition of CTBN in the blend and decreased thereafter. The toughness and elongation at break increased, whereas tensile strength decreased up to 20 wt% loading of CTBN in the blends. Two‐phase morphology appeared with the incorporation of CTBN in the cycloaliphatic epoxy resin matrix. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:258–271, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20106

Effect of carboxyl-terminated poly(butadiene- co-acrylonitrile) (CTBN) concentration on thermal and mechanical properties of binary blends of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin

Six blend samples were prepared by physical mixing of epoxy resin with varying concentrations of liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer having 27% acrylonitrile content. The blend samples were cured with aromatic amine. A comparative study of Fourier-transform infrared (FTIR) spectra showed the modification as a result of chemical reactions between epoxide group, curing agent and CTBN. The tensile strength of cured blend samples decreased slightly from 11 to 46% where as the elongation-at-break showed an increasing trend with increasing rubber content, i.e., up to 25 phr, in the blend samples. Appreciable improvements in impact strength were also observed in the prepared blend systems. The glass transition temperature ( T g) of the epoxy resin matrix was slightly reduced on the addition of CTBN. The cured resin showed a two-phase morphology where the spherical rubber domains were dispersed in the epoxy matrix.

Modification of epoxy resin: a comparison of different types of elastomer

Composites were prepared using epoxy resin (ER), carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) and hydroxyl-terminated polybutadiene (HTPB), in different proportions. A chemical link between the HTPB and the epoxy resin was promoted employing tolylene diisocyanate (TDI). The reactions between elastomers and epoxy resin were followed by FTIR. The mechanical properties of the composites were evaluated and the microstructure was investigated through scanning electronic microscopy (SEM). The results showed that the impact resistance of CTBN-modified ER was superior to that of the pure epoxy resin. For the composites with HTPB, the impact resistance increased with elastomer concentration up to three parts per hundred parts of resin (phr). Higher concentrations of HTPB resulted in larger particles and gave lower impact values.