Carbon fibre/epoxy composite joints were assembled with Poly-etherether-ketone (PEEK) and Poly-ethylenimine (PEI) films using a co-curing process to prepare single-lap joint specimens. The joints were tested under quasi-static loading conditions at 22 °C and 130 °C and a fatigue loading condition. The experimental results demonstrated better or comparable structure integrity of the composite joints co-cured by PEEK and PEI films than the reference joints bonded by aerospace FM300 adhesives. In particular, the PEEK co-cured joints exhibited extraordinary mechanical performance at 130 °C and excellent fatigue resistance. For instance, the lap-shear strength at 130 °C and the fatigue life of the composite joints co-cured by 200μm PEEK films was 2.1 times and 2.7 times higher than that of the aerospace adhesive joints, respectively. Overall, the results of this work proved that advanced thermoplastic films are promising alternatives to epoxy adhesives for the co-cure joining of thermoset composites with significantly enhanced structural integrity and thermal stability.

Organic–inorganic nanohybrids-based polymer nanocomposites are made up of two different components, and these hybrids attained great attention over last decades due to their diversified framework and fascinating features. These nanohybrids possess synergistic characteristics of both organic and inorganic substances. Different synthetic routes are used to synthesize these materials with enhanced morphology, tunable features, and fine nanostructures. This chapter focuses on various synthetic routes for fabrication of organic–inorganic-based nanopolymeric composites. Synthetic strategies and protocols of different routes have been described in details. We have also discussed the advantages and limitations of all synthetic methods in details.

Rapid industrial development, vehicles, domestic activities and mishandling of garbage are the main sources of pollutants, which are destroying the atmosphere. There is a need to continuously monitor these pollutants for the safety of the environment and human beings. Conventional instruments for monitoring of toxic gases are expensive, bigger in size and time-consuming. Hybrid materials containing organic and inorganic components are considered potential candidates for diverse applications, including gas sensing. Gas sensors convert the information regarding the analyte into signals. Various polymeric/inorganic nanohybrids have been used for the sensing of toxic gases. Composites of different polymeric materials like polyaniline (PANI), poly (4-styrene sulfonate) (PSS), poly (3,4-ethylene dioxythiophene) (PEDOT), etc. with various metal/metal oxide nanoparticles have been reported as sensing materials for gas sensors because of their unique redox features, conductivity and facile operation at room temperature. Polymeric nanohybrids showed better performance because of the larger surface area of nanohybrids and the synergistic effect between polymeric and inorganic materials. This review article focuses on the recent developments of emerging polymeric/inorganic nanohybrids for sensing various toxic gases including ammonia, hydrogen, nitrogen dioxide, carbon oxides and liquefied petroleum gas. Advantages, disadvantages, operating conditions and prospects of hybrid composites have also been discussed.

A large fraction of population is suffering from waterborne diseases due to the contaminated drinking water. Both anthropogenic and natural sources are responsible for water contamination. Revolution in industrial and agriculture sectors along with a huge increase in human population has brought more amount of wastes like heavy metals, pesticides and antibiotics. These toxins are very harmful for human health, therefore, it is necessary to sense their presence in environment. Conventional strategies face various problems in detection and quantification of these pollutants such as expensive equipment and requirement of high maintenance with limited portability. Recently, nanostructured devices have been developed to detect environmental pollutants. Polymeric nanocomposites have been found robust, cost effective, highly efficient and accurate for sensing various environmental pollutants and this is due to their porous framework, multi-functionalities, redox properties, great conductivity, catalytic features, facile operation at room temperature and large surface area. Synergistic effects between polymeric matrix and nanomaterials are responsible for improved sensing features and environmental adaptability. This review focuses on the recent advancement in polymeric nanocomposites for sensing heavy metals, pesticides and antibiotics. The advantages, disadvantages, operating conditions and future perspectives of polymeric nanocomposites for sensing toxic pollutants have also been discussed.

Exploring routes for the effective use of recycled carbon fibres (rCFs) is critical to close the loop in the life cycle of carbon fibres. This work demonstrated a potential of using rCFs for interlayer toughening of carbon fibre/epoxy composites. Nonwoven mats based on rCFs and commingled rCFs/Polyphenylene-sulfid (PPS) fibres were used to interlay a laminate, aiming to improve the mode-I and mode-II fracture toughness. The experimental results proved significant enhancements in the interlaminar fracture properties upon interleaving, with the rCF/PPS mats exhibiting a more prominent toughening effectiveness than the rCF mats. For example, the maximum increase in mode-I and mode-II fracture initiation energies of the laminates was 51% and 66%, respectively upon interleaving the rCF mats, and 220% and 105%, respectively by adding the rCFs/PPS mats. The fractography analysis proved that the main toughening mechanisms were fibre debonding and pulling-out for the rCF mats and fibre bridging for the commingled rCFs/PPS mats. The differences in the toughening mechanisms resulted in opposite effects of the interlayer/epoxy adhesion to the fracture toughness, i.e. an improved interlayer/epoxy adhesion increased the toughening effectiveness of the rCF mats, but negatively affected the toughening performance of the rCF/PPS mats.

Epoxies are inherently brittle materials and to overcome this brittleness, a second microphase (i.e., thermoplastic) is typically added. This modification of epoxy resin using thermoplastics results in reaction-induced phase separating morphologies in the micrometer range. In this study, the influence of the curing history, beyond phase separation, on the interphase formation and final morphology of PEI and the high Tg epoxy system is investigated. Several cure cycles were examined, each with a first dwell temperature ranging from 120 to 180 °C for a given time up to the onset of phase separation (OPS) or up to the 80% degree of cure (80% DOC) and then with a second dwell at 200 °C for 20 min to complete the cure cycle. Hot-stage microscopy experiments were carried out at several first dwell temperatures before final conversion at the second dwell. The morphologies and resulting droplet size distribution at the interphase, after the final cure, were analyzed through scanning electron microscopy. Results showed that the diffusion distance was significantly higher in the case of OPS as compared to the 80% DOC case, particularly at lower first dwell temperatures. This behavior was attributed to the fact that, in the case of OPS, polymeric chains were still in a mobile state and diffused further during the second dwell curing stage, while at 80% DOC, polymeric chains were completely bound but still diffuse due to non-stoichiometric curing. This restricted mobility of polymeric chains after phase separation (80% DOC) resulted in a larger number of smaller droplets as compared to the OPS case.

Acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) are considered a well-known class of engineering thermoplastics due to their efficient use in automotive, 3D printing, and elec-tronics. However, improvement in toughness, processability, and thermal stability is achieved by mixing together ABS and PC. The present study focuses on the understanding of surface mechanical characterization of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) blends using nano-indentation. Polymer blends sheets with three different proportions of ABS/PC (75:25, 50:50, and 25:75) were fabricated via melt-processing and thermal press. Fourier transform infrared (FTIR) spectroscopy was performed to analyze the intermolecular interactions between the blends’ compo-nents. To understand the surface mechanical properties of ABS and PC blends, a sufficient number of nano-indentation tests were performed at a constant loading rate to a maximum load of 100 mN. Creeping effects were observed at the end of loading and start of unloading section. Elastic modulus, indentation hardness, and creep values were measured as a function of penetration displacement in the quasi-continuous stiffness mode (QCSM) indentation. Load-displacement curves indicated an increase in the displacement with the increase in ABS contents while a decreasing trend was observed in the hardness and elastic modulus values as the ABS content was increased. We believe this study would provide an effective pathway for developing new polymer blends with enhanced mechanical performance.

Background: Polymeric gels, an important class of soft matter systems, are widely used for commercial applications particularly in food products (i.e., saturated fat replacement). The efficiency of the product for a particular application can be directly linked to its rheological signature. However, the rheological imprint of these structured systems is significantly dependent on the interactions between their individual components. Therefore, the rational understanding of interacting components, their structural arrangements and the resultant characteristics of a hybrid system is vital, in order to speed-up our progress in recognizing the suitable combination of gelling agents and also to tune the technological and functional properties of final product. Scope and approach: The main aim of this narrative review article is to look at the synergistic interactions (i.e., interpenetrating polymer structures) between different components of the hybrid systems (i.e., multi-component organogels or bigels), in order to unveil the resultant rheological characteristics for different commercial applications including food systems. However, multi-component hydrogel systems have not been discussed in this review. Key findings and conclusions: The existence of synergistic interactions between different gelators in multi-component organogels (i.e., higher values of hardness and moduli (G^'and G'^') of multi-component organogel than the corresponding mono-component system) is clearly evident from the literature. This synergy also helps in optimizing the rheological signature of final system by exploiting the concept of formulation engineering. However, this exciting concept of synergistic enhancement in properties has not yet been explored in the field of bigels. The incorporation of colloidal particles in the gelled system resulted in increased stability and higher moduli values, as compared to the gels without particles. This exciting approach can also be quite useful for designing food products by exploiting the useful properties of gelators and (nano)particles, in a single system.

Epoxy resins are widely used for different commercial applications, particularly in the aerospace industry as matrix carbon fibre reinforced polymers composite. This is due to their excellent properties, i.e., ease of processing, low cost, superior mechanical, thermal and electrical properties. However, a pure epoxy system possesses some inherent shortcomings, such as brittleness and low elongation after cure, limiting performance of the composite. Several approaches to toughen epoxy systems have been explored, of which formation of the interpenetrating polymer network (IPN) has gained increasing attention. This methodology usually results in better mechanical properties (e.g., fracture toughness) of the modified epoxy system. Ideally, IPNs result in a synergistic combination of desirable properties of two different polymers, i.e., improved toughness comes from the toughener while thermosets are responsible for high service temperature. Three main parameters influence the mechanical response of IPN toughened systems: (i) the chemical structure of the constituents, (ii) the toughener content and finally and (iii) the type and scale of the resulting morphology. Various synthesis routes exist for the creation of IPN giving different means of control of the IPN structure and also offering different processing routes for making composites. The aim of this review is to provide an overview of the current state-of-the-art on toughening of epoxy matrix system through formation of IPN structure, either by using thermoplastics or thermosets. Moreover, the potential of IPN based epoxy systems is explored for the formation of composites particularly for aerospace applications.

Nano-indentation, a depth sensing technique, is a useful and exciting tool to investigate the surface mechanical properties of a wide range of materials, particularly polymers. Knowledge of the influence of experimental conditions employed during nano-indentation on the resultant nano-mechanical response is very important for the successful design of engineering components with appropriate surface properties. In this work, nano-indentation experiments were carried out by selecting various values of frequency, amplitude, contact depth, strain rate, holding time, and peak load. The results showed a significant effect of amplitude, frequency, and strain rate on the hardness and modulus of the considered polymer, ultrahigh molecular weight polyethylene (UHMWPE). Load-displacement curves showed a shift towards the lower indentation depths along with an increase in peak load by increasing the indentation amplitude or strain rate. The results also revealed the strong dependence of hardness and modulus on the holding time. The experimental data of creep depth as a function of holding time was successfully fitted with a logarithmic creep model (R² ≥ 0.98). In order to remove the creeping effect and the nose problem, recommended holding times were proposed for the investigated polymer as a function of different applied loads.

Nanostructured (hybrid) membranes combining properties of inorganic and polymeric materials is an integral part of the field of separation technology. Mixed matrix membranes were prepared from oppositely charged inorganic (INPs) and polymeric (PNPs) nanoparticles using spin coating method. Four different types of PNPs were prepared. Poly(2-dimethylaminoethyl methacrylate)-b-(methyl methacrylate)) and poly((methacrylic acid)-b-(methyl methacrylate)) diblock copolymers were prepared via RAFT dispersion polymerization in ethanol at 70 °C. Quaternized poly(2-(dimethylamino) ethyl methacrylate)-b-poly (benzyl methacrylate) and poly(potassium 3-sulfopropyl methacrylate)-b-poly (benzyl methacrylate) block copolymers were prepared using aqueous RAFT emulsion polymerization method at 70 °C. The inorganic iron oxide nanoparticles (INPs) were either coated with [3-(2-Aminoethylamino)propyl] trimethoxysilane (TPED) via Dimercaptosuccinic acid (DMSA) using stab exchange. Transmission electron microscopy (TEM) and Dynamic light scattering (DLS) analysis were performed to examine the size and morphology of the prepared polymeric and inorganic nanoparticles. Scanning electron microscope (SEM) and Atomic Force Microscope (AFM) images were obtained to analyze the topography and thin film formation on the nylon support. Detailed filtration experiments were carried out to evaluate the effect of pH on the performance of the membrane.

Oil/water emulsions are usually stabilized either by interfacial modification using nanoparticles and surfactants (stated as pickering emulsion or bijels) or by bulk stabilization with the help of low‐molecular‐weight or polymeric gelators (known as bigels) in response to some external stimuli (e.g., pH, temperature). Both these approaches result in different systems that are quite useful for different applications, including catalysis, pharmaceutical and agrochemicals. However, these systems also possess some inherent drawbacks that need to be addressed, like difficulty in fabrication and ensuring the permanent binding of nanoparticles at the oil/water interface, in case of nanoparticles stabilized emulsions (i.e., interfacial stabilization). Similarly, the long‐term stability of the oil/water systems produced by using (hydro/organo) gelators (i.e., bulk stabilization) is a major concern. Here, we show that the oil/water system with improved mechanical and structural properties can be prepared with the synergistic effect of interfacial and bulk stabilization. We achieve this by using nanoparticles to stabilize the oil/water interface and polymeric gelators to stabilize the bulk phases (oil and water). Furthermore, the proposed strategy is extremely adaptable, as the properties of the resultant system can be finely tuned by manipulating different parameters such as nanoparticles content and their surface functionalization, solvent type and its volume fraction, and type and amount of polymeric gelators.