Reactive Liquid Rubber Research Articles

Mode II fracture characterization of toughened epoxy resin composites

Epoxy resin used commonly as a matrix for polymer composite materials has good handling properties, but is too brittle. That is why various modifiers are used to increase the flexibility of products based on epoxy resin. This leads to two issues: how to efficiently increase the toughness of the resin without impacting significantly other properties, as well as how to measure the toughness in composite materials. The work aimed to show how the addition of a reactive rubber modifier will affect the fracture toughness of the obtained laminates during the longitudinal shear test (Mode II fracture). In total, three epoxy-glass laminates with different matrices were made and subjected to the End-Notched Flexure test according to ASTM D7905/D7905M standard: (1) the basic matrix of Epidian 6 resin, (2) Epidian 6 modified with the addition of 10% of Albipox 1000 reactive liquid rubber and (3) Epidian 6 modified with the addition of 10% of Hypro 1300X16 ATBN reactive liquid rubber. Based on the obtained results, it can be seen that the modulus of elasticity for the modified laminates was decreased compared to the laminate of pure epoxy resin (by ~ 25%). However, the addition of reactive rubbers increased the fracture toughness of the modified epoxy-glass laminates in the Mode II longitudinal shear test (GIIc) by ~ 40–60%. Thus the benefits of modification outweigh the drawbacks if fracture toughness is an important designing consideration in a given application. The applicability of ENF method is successfully tested, but potential drawbacks are indicated—careful control of specimen thickness is necessary.

Effect Of Liquid Rubbers On The Thermal And Adhesion Properties Of The Tire Skim Compound

Polymeric textile cords, steel cords and steel cables are mainly reinforcing materials that are used in tire production. Polymeric textile cords such as Polyester (PEs), Nylon, Aramid and Rayon are commonly treated with bi-functional resorcinol formaldehyde latex (RFL) to obtain desired adhesion to rubber matrix. PEs cords are known as their poor adhesion to both RFL and rubber compounds due to limited reactivity on the surface and poor reaction extent between methylol and hydroxyl groups of RFL. Increasing carboxyl content on PEs surface or in the rubber compound is one of the best strategies to overcome this adhesion problem. Liquid rubbers, which can co-vulcanize with solid rubbers, are also strong alternatives of process oils with their excellent plasticizing effect without deterioration in mechanical properties of the resulting material. Co-vulcanization also improves the stability of this additive and prevents possible bleeding and migration during service life of the tire. In this study, carboxylated grafted liquid isoprene rubber has been incorporated to rubber compound to improve adhesion in PEs-RFL-Rubber ternary system. Rheological and dynamic-mechanical properties of reactive liquid rubber containing tire rubber compounds have been evaluated extensively, as well as H-adhesion behaviour of PEs cord-rubber composite matrix.

Effects of core–shell and reactive liquid rubbers incorporation on practical adhesion and fracture energy of epoxy adhesives

Effects of core–shell and reactive liquid rubbers incorporation on practical adhesion and fracture energy of epoxy adhesives

Stretchable Polymer Gate Dielectric with Segmented Elastomeric Network for Organic Soft Electronics

Stretchable electronics has emerged as a key technology for human-friendly soft electronic applications. However, the difficulty of preparing stretchable gate dielectrics is a major impediment to the realization of stretchable electronic devices. Here, we present a stretchable polymer gate dielectric for use in stretchable organic thin-film transistors (OTFTs). Our strategy is to form a segmented elastomeric network inside an end-functionalized reactive liquid rubber with a high dielectric constant by using an organosilane cross-linking agent. The developed dielectric layer consists of hard segments of self-organized nanocrystals and soft rubber segments. The nanocrystals distributed in the rubber matrix resist the growth of electrical treeing inside the film and thus significantly increase the dielectric strength and reduce the leakage current density (∼10–8 A cm–2 at 2.0 MV cm–1). The superior insulating properties are maintained well during tensile stretching with moderate strains ε ≤ 30%. Furthermore, fully stretchable OTFTs based on the developed gate dielectric were demonstrated to stably operate without electrical breakdown under stretching of ε ≤ 34%. These results prove that our method is a promising approach to the development of stretchable polymer gate dielectrics.

Study on the adhesive properties of reactive liquid rubber toughened epoxy-clay hybrid nanocomposites

Abstract The present work investigates the adhesive properties and morphology of diglycidyl ether of bisphenol A nanocomposites modified with reactive butadiene acrylonitrile copolymers having different amine equivalent weight. Tensile adhesive strength and shear adhesive strength of epoxy resin were significantly increased due to reactive rubbers and nanoparticles (ZW1) incorporation to the epoxy matrix. Hybrid composites based on 1 wt% ZW1 and 10 wt% ATBN-16, 1 wt% ZW1 and 15 wt% ATBN-21 exhibited maximum adhesive strength in comparison with neat epoxy resin as well as epoxy nanocomposite containing 1% ZW1. Tensile adhesive strength of hybrid composites containing 1% ZW1 and 10% ATBN-16 as well as 1% ZW1 and 15% ATBN-21 was maximally enhanced. The fracture surfaces of epoxy hybrid composites showed significant plastic yielding together with delaminated and stratified structures, explaining thus the increase of the adhesive strength of tested composites. This finding was confirmed by FTIR spectra in terms of chemical reactions occurrence between the reactive rubbers and epoxy matrix.

Microstructures of unsaturated polyester resins modified with reactive liquid rubbers

The work presents an analysis of the microstructure of polyester resin castings modified with two reactive liquid rubbers, which were dissolved in the resin and precipitated during curing. Samples of castings were imaged with an optical and a scanning electron microscope. The volume fraction of precipitated particles is 3–10 times greater than the introduced volume of rubber. The particles contain not only rubber, but also (co)polymerization products of styrene and/or polyester and show good adhesion to the polyester resin matrix. The size of the particles is dependent on the type and amount of rubber used.

Preparation and characterization of reactive liquid rubbers toughened epoxy-clay hybrid nanocomposites

Abstract The present work investigates the effect of organomodified nanoclay (ZW1) and butadiene-acrylonitrile copolymer terminated with different amine groups (amine-terminated butadiene-acrylonitrile, ATBN) on the properties and morphology of epoxy resin. The morphologies of the nanocomposites were analyzed by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The nanocomposites structure was confirmed by Fourier transform infrared (FTIR) spectroscopy, XRD and TEM. The properties evaluation showed that the polymeric modifier and nanoclays strongly influence the fracture toughness and flexural properties of the nanocomposites. Hybrid epoxy composites containing 1% ZW1 and ATBN rubbers showed improved fracture toughness and flexural properties in comparison with unmodified epoxy resin. FTIR spectra showed an increase in the hydroxyl peak height peak height of 3360 cm-1 due to reactive rubber incorporation. SEM micrographs of hybrid epoxy resin nanocomposites showed significant plastic yielding of the polymer matrix with stratified structures and more cavitations, explaining thus the enhancement of fracture toughness and flexural strength of the nanocomposites.

Carbon fiber-reinforced composites using an epoxy resin matrix modified with reactive liquid rubber and silica nanoparticles

Abstract Carbon fiber-reinforced composites are gaining importance and are about to play a very prominent role in automotive applications. In structural applications mainly epoxy resins are used as matrix materials. The properties of epoxy resins and laminates made thereof can be improved by tougheners like reactive liquid rubbers. Further improvements can be achieved by adding surface-modified silica nanoparticles, with 20 nm in size and a very narrow particle size distribution. In this study carbon fiber-reinforced laminates made from epoxy resins modified with reactive liquid rubber and silica nanoparticles have been prepared and investigated. A very fast amine cure of 15 min has been chosen to match industrial needs. Mechanical properties for bulk resins and laminates are compared and the mechanisms responsible for the property improvements are discussed. Structure property relationships between the neat resin fracture toughness and the interlaminar G Ic and G IIc of the reactive liquid rubber and silica nanoparticles modified resins were established. Tough laminates could be prepared. However, CAI performance of the hybrid laminates was slightly inferior as compared to the rubber-toughened laminates, most probably due to agglomerates of nanoparticles found in the cured resin systems. The reason for the nanoparticle aggregation was detected and their influence on laminate performance discussed.

Improved fracture toughness in carbon fibre epoxy composite through novel pre-preg coating method using Epoxy Terminated Butadiene Nitrile rubber

A novel pre-preg coating method was used to improve the interlaminar fracture toughness in carbon fibre epoxy composite laminates, using reactive liquid rubber. The Epoxy Terminated Butadiene Nitrile (ETBN) liquid rubber incorporated between pre-pregs using automatic draw bar coating technique. Experimental test results reveal that by adding ETBN in small quantities in the range of 15.55–22.66g/m2, inter laminar critical energy release rates (GIC and GIIC) can be improved up to 140% in mode-I loadings and 32% in mode-II loadings respectively. It was confirmed that the effect of ETBN rubber concentration in carbon epoxy pre-preg system on interlaminar fracture toughness under mode-I and mode-II loadings, was discussed by on the bases of fractographic observations and mechanism considerations using SEM.

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.

Development and characterization of flexible epoxy foam with reactive liquid rubber and starch

Flexible foams are prepared using carboxyl-terminated butadiene-acrylonitrile rubber (CTBN), diglycidyl ether of bisphenol A epoxy resin and a chemical blowing agent. Central composite design experiments are conducted to investigate the influences of three independent variables, i.e., the ratio of CTBN to epoxy resin, the amounts of curing agent (dicyandiamide) and blowing agent (azodicarbonamide), on the foam performances. After that, epoxy foams are also characterized for mechanical properties to explore the effects of the aforesaid ratio, accelerator type, starch and foaming methods. SEM analysis is used to evaluate the changes in cell characterizations.

Fiber-reinforced composites based on epoxy resins modified with elastomers and surface-modified silica nanoparticles

The properties of fiber-reinforced composites made using epoxy resin formulations can be improved using modified epoxy resins. As epoxies are inherently brittle, they are toughened with reactive liquid rubbers or core–shell elastomers. Surface-modified silica nanoparticles, 20 nm in diameter and with a very narrow particle size distribution, are available as concentrates in epoxy resins in industrial quantities for the past 10 years. Some of the drawbacks of toughening like lower modulus or a loss in strength can be compensated when using nanosilica together with these tougheners. Apparently, there exists a synergy as toughness and fatigue performance are increased significantly. Some of these improvements in bulk resin properties can be found for fiber-reinforced composites as well. In this article, the literature published in the last decade is studied with a focus on mechanical properties. Results are compared, and the mechanisms responsible for the property improvements are discussed. A relationship between the improvements of the fracture energy of the cured bulk epoxy resins and the fracture energy of the fiber-reinforced composites could be established.

Effect of resin modification on the impact strength of glass-polyester composites

Summary — Fiber-reinforced plastics (FRP) are nowadays used commonly for constructions subjected to impacts of different energies and velocities, therefore the problem of their impact resistance is very important. One of the methods to improve impact properties of the composites is resin modification with elastomeric phase. In this study the effect of resins addition on properties of composites of unsaturated polyester (UP) resins with glass fibers was investigated. At the first stage, the properties of Polimal 109-32K UP resin modified by the addition of reactive liquid rubbers were tested. The wettability of glass fibers by resin compositions was also tested. Composites were then prepared with the addition of 2 and 6 phr of epoxy or vinyl terminated butadiene-acrylonitrile rubbers (ETBN or VTBN, respectively), as well as 5 and 15 wt. % of Polimal 150 elastic UP resin. These composites were subjected to mechanical tests. Impact properties were tested using Charpy method, as well as by a ballistic impact using a gas gun. After the ballistic impact, damage extent and residual strength as well as water leakage through the composites were evaluated. The damage was also investigated under a microscope. The damage extent was confirmed to be linearly dependent on the impact energy. The addition of rubber was found to decrease the damage extent and increase post-impact residual strength, as well as decrease water leakage rate.

Mechanical, thermal and electrical properties of epoxy modified with a reactive hydroxyl-terminated polystyrene-butadiene liquid rubber

This study investigated the modification of epoxy resin with a hydroxyl-terminated polystyrene-butadiene liquid rubber copolymer. The Fourier transform infrared analysis evidenced the occurrence of a chemical reaction between the oxirane ring of epoxy resin and the hydroxyl functional group of hydroxyl-terminated polystyrene-butadiene using benzyldimethylamine as a catalyst. The mechanical results indicated that the 10 phr hydroxyl-terminated polystyrene-butadiene-modified epoxy resin exhibited the maximum impact strength of 16.5 J/m2, which is about 91.8% higher than that for the neat epoxy; the best mechanical performance in terms of tensile and flexural properties was achieved at 10 phr hydroxyl-terminated polystyrene-butadiene content; higher concentration of hydroxyl-terminated polystyrene-butadiene resulted in the cured networks lower impact and strength values. The investigation on the microstructure of hydroxyl-terminated polystyrene-butadiene–modified epoxy resin showed a two-phase morphology where the hydroxyl-terminated polystyrene-butadiene domains were uniformly dispersed in epoxy resin matrix. The addition of hydroxyl-terminated polystyrene-butadiene into epoxy resin reduced the thermal stability, whereas, it obviously improved the volume, surface resistivity; and the dielectric breakdown strength of 20 phr hydroxyl-terminated polystyrene-butadiene–modified epoxy resin was 36 kV/mm compared to 31.2 kV/mm of the neat epoxy resin.

Mechanical and dielectric properties of epoxy resin modified using reactive liquid rubber (HTPB)

AbstractIn the present study, hydroxyl‐terminated polybutadiene (HTPB) liquid rubber was employed to modify epoxy resin using 2,4,6‐tri (dimethylaminomethyl) phenol as a catalyst, and methyl hexahydrophthalic anhydride as a curing agent. The reactions between HTPB and epoxy were monitored by Fourier transform infrared (FTIR); the mechanical and dielectric properties of HTPB modified epoxies were evaluated and the morphology was investigated through scanning electronic microscopy (SEM). The FTIR analysis evidenced the occurrence of a chemical reaction between the two components. The mechanical results indicated that the impact strength of HTPB‐modified epoxy was superior to that of the pure epoxy. As the HTPB content increased up to 10 phr the best mechanical performances in terms of tensile and flexural properties were achieved when compared to the unmodified epoxy. Higher concentration of HTPB resulted in larger particles and gave lower mechanical strength values. The incorporation of HTPB into epoxy decreased the dielectric constant and dissipation factor over a wide frequency range from 1 to 106 Hz, and improved the electrical resistivity. SEM micrographs showed that the modified epoxy exhibited a two‐phase morphology where the spherical rubber domains were dispersed in the epoxy matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Enhancing Fracture Toughness of Glass/Epoxy Composites for Wind Blades Using Silica Nanoparticles and Rubber Particles

The research aims to investigate the interlaminar fracture toughness of glass fiber/epoxy composites, which consist of the silica nanoparticles and the rubber particles. Two kinds of rubber particles, one is the reactive liquid rubber (CTBN) and the other is the core-shell rubber (CSR), were employed to modify the fracture toughness of epoxy resin. In general, the disadvantage of adding rubber particles into polymeric resin is the dramatic reduction of stiffness although the toughness could be modified accordingly. In order to enhance the fracture toughness of the fiber composites without sacrificing their stiffness, the silica nanoparticles in conjunction with the rubber particles were introduced concurrently into the epoxy matrix to form a hybrid nanocomposite. Experimental results obtained from tensile tests on bulk epoxy confirm the presumption that the reduction of the epoxy stiffness because of the presence of rubber particles can be effectively compensated by the silica nanoparticles. Furthermore, the fracture tests conducted on the DCB specimens revealed that the inclusion of silica nanoparticles together with the CSR particle can appreciably increase the fracture toughness of the glass/epoxy composites up to 82%. On the other hand, when the epoxy matrices were modified with CTBN rubber particles and silica nanoparticles, the improvement of the interlaminar fracture toughness was around 48%.

Rubber-toughened epoxy loaded with carbon nanotubes: structure–property relationships

The paper reports on the preparation, structure and properties of ternary thermosetting blends, based on DGEBA epoxy, cured with 3,3′-DDS and modified by the addition of CTBN reactive liquid rubber and/or 0.3 wt% of commercial multi-walled carbon nanotubes. The toughening effect of the phase-separated rubber particles is enhanced by the presence of the nanotubes, through a change in the morphology. In the absence of the rubber, the nanotubes alone produce a minimal effect upon the thermo-mechanical characteristics of the resin. However, the electrical conductivity of the cured resin samples is found to increase by five orders of magnitude, up to 3.6 × 10−3 S/m in the ternary blend.

Ultra-tough and fatigue resistant

Constantly growing demands are placed on adhesives in the aircraft, automotive, shipbuilding and wind turbine industries. At the same time, it is important that the costs of these adhesives do not rise. One solution to this problem could be structural adhesives which combine surface-modified SiO2 nanoparticles with reactive liquid rubbers to produce a highly specialised property profile.

Enhancing Fracture Toughness of Glass/Epoxy Composites by Using Rubber Particles Together with Silica Nanoparticles

The research aims to investigate the interlaminar fracture toughness of glass fiber/epoxy composites, which consist of the silica nanoparticles and the rubber particles. Two kinds of rubber particles, one is the reactive liquid rubber (CTBN) and the other is the core-shell rubber (CSR), were employed to modify the fracture toughness of epoxy resin. In general, the disadvantage of adding rubber particles into polymeric resin is the dramatic reduction of stiffness although the toughness could be modified accordingly. In order to enhance the fracture toughness of the fiber composites without sacrificing their stiffness, the silica nanoparticles in conjunction with the rubber particles were introduced into the epoxy matrix to form a hybrid nanocomposite. Experimental results obtained from tensile tests on bulk epoxy confirm the presumption that the reduction of the epoxy stiffness because of the presence of rubber particles can be effectively compensated by the silica nanoparticles. Furthermore, the fracture tests conducted on the double cantilever beam specimens revealed that the inclusion of silica nanoparticles together with the CSR particle can appreciably increase the fracture toughness of the glass/epoxy composites up to 82%. On the other hand, when the epoxy matrices were modified with CTBN rubber particles and silica nanoparticles, the improvement of the interlaminar fracture toughness was around 48%. It is noted that the role of the silica nanoparticles on the fracture toughness of fiber composites with rubber-modified epoxy matrix is different. For the CSR-modified epoxy matrix, the contribution of silica nanoparticle on the fracture toughness is destructive. In contrast, for the CTBN-modified epoxy matrix, the silica nanoparticles can synchronously improve the fracture toughness of composites.

Dynamic mechanical properties of epoxy/novolac system modified with reactive liquid rubber and carbon filler

This paper reports on the work carried out to evaluate the frequency dependent viscoelastic properties of epoxy/novolac compositons modified with a liquid reactive rubber and carbon filler. For epoxy systems modified with elastomer, three typical transitions were observed: the α-relaxation deeply related to the glass transition of epoxy, the β-transition of epoxy, and the glass transition of rubber appeared near to the β-relaxation of epoxy resin. Considering an Arrhenius equation, the activation energies of β-relaxation were estimated. In the region of glass transition and rubbery state the temperature dependence of the shift factor (αT) was determined through Williams-Landel-Ferry (WLF) equation.