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Many common elastomeric products, including nitrile gloves, are manufactured by coagulant dipping. This process involves the destabilization and gelation of a latex dispersion by an ionic coagulant. Despite widespread application, the physical chemistry governing coagulant dipping is poorly understood. It is unclear which properties of an electrolyte determine its efficacy as a coagulant and which phenomena control the growth of the gel. Here, a novel experimental protocol is developed to directly observe coagulant gelation by light microscopy. Gel growth is imaged and quantified for a variety of coagulants and compared to macroscopic dipping experiments mimicking the industrial process. When the coagulant is abundant, gels grow with a t1/2 time dependence, suggesting that this phenomenon is diffusion-dominated. When there is a finite amount of coagulant, gels grow to a limiting thickness. Both these situations are modeled as one-dimensional diffusion problems, reproducing the qualitative features of the experiments including which electrolytes cause rapid growth of thick gels. We propose that the gel thickness is limited by the amount of coagulant available, and the growth is, therefore, unbounded when the coagulant is abundant. The rate of the gel growth is controlled by a combination of a diffusion coefficient and the ratio of the critical coagulation concentration to the amount of coagulant present, which in many situations is set by the coagulant solubility. Other phenomena, including diffusiophoresis, may make a more minor contribution to the rate of gel growth. [ABSTRACT FROM AUTHOR]

In this work, we designed a novel nanocomposite proton-exchange membrane (PEM) based on sulfonated poly(ether ether ketone) (SPEEK) and tantalum disulfide functionalized with terminal sulfonate groups (S-TaS2). The PEMs are prepared through a solution-casting method and exploited in direct methanol fuel cells (DMFCs). Two-dimensional S-TaS2 nanoflakes were prepared as a functional additive to produce the novel nanocomposite membrane for DMFCs due to their potential as a fuel barrier and an excellent proton conductor. To optimize the degree of sulfonation (DS) of SPEEK and the weight percentage (wt%) of S-TaS2 nanoflakes in PEMs, we used the central composite design of the response surface method. The optimum PEM was obtained for SPEEK DS of 1.9% and a weight fraction (wt%) of S-TaS2 nanoflakes of 70.2%. The optimized membrane shows a water uptake of 45.72%, a membrane swelling of 9.64%, a proton conductivity of 96.24 mS cm−1, a methanol permeability of 2.66 × 10−7 cm2 s−1, and a selectivity of 36.18 × 104 S s cm−3. Moreover, SPEEK/S-TaS2 membranes show superior thermal and chemical stabilities compared to those of pristine SPEEK. The DMFC fabricated with the SPEEK/S-TaS2 membrane has reached the maximum power densities of 64.55 mW cm−2 and 161.18 mW cm−2 at 30 °C and 80 °C, respectively, which are ∼78% higher than the values obtained with the pristine SPEEK membrane. Our results demonstrate that SPEEK/S-TaS2 membranes have a great potential for DMFC applications. [ABSTRACT FROM AUTHOR]

The materials commonly used to fabricate thermoelectric devices are tellurium, lead, and germanium. These materials ensure the best thermoelectric performance, but exhibit drawbacks in terms of availability, sustainability, cost, and manufacturing complexity. Moreover, they do not guarantee a safe and cheap implementation in wearable thermoelectric applications. Here, p‐Type and n‐type flexible thermoelectric textiles are produced with sustainable and low‐cost materials through green and scalable processes. Cotton is functionalized with inks made with biopolyester and carbon nanomaterials. Depending on the nanofiller, i.e., graphene nanoplatelets, carbon nanotubes, or carbon nanofibers, positive or negative Seebeck coefficient values are obtained, resulting in a remarkable electrical conductivity value of 55 S cm−1 using carbon nanotubes. The best bending and washing stability are registered for the carbon nanofiber‐based biocomposites, which increase their electrical resistance by 5 times after repeated bending cycles and only by 30% after washing. Finally, in‐plane flexible thermoelectric generators coupling the best p‐ and n‐type materials are fabricated and analysed, resulting in an output voltage of ≈1.65 mV and a maximum output power of ≈1.0 nW by connecting only 2 p/n thermocouples at a temperature difference of 70 °C. [ABSTRACT FROM AUTHOR]

Starch, as a natural, renewable, and biodegradable polysaccharide, is widely used in the food and pharmaceutical industries. However, the extreme water‐sensitivity and poor tensile strength of starch materials have limited its practical application as an engineering material. Here, the authors blended starch with PVA to improve its film formability, and then, added Na‐MMT and SNCs to the blend in order to enhance the mechanical properties. Nanofillers are used in pure and hybrid form to study the synergistic effect of these two types of nanofillers. SNCs, obtained by acidic hydrolysis of potato starch granules, have a z‐average particle size of ≈230 nm and crystallinity of 57%. Nanocomposite films, prepared via the solution casting method, are characterized by X‐ray diffraction (XRD) and tensile testing methods. XRD patterns confirmed the exfoliation dispersion of Na‐MMT in the polymer blend matrix. Additionally, the results of the tensile tests and thermogravimetric analysis (TGA) indicated that the presence of nanofillers in separate and hybrid forms in the matrix led to the improvement of the mechanical and thermal properties of nanocomposites. Finally, the findings revealed the synergistic effect of nanofillers of SNCs and Na‐MMT for improving the mechanical and thermal properties of starch/PVA blend, particularly in 3 wt% of the total filler content in 50:50 (w/w). At a specific composition of 3wt%, a hybrid reinforcement system comprising sodium montmorillonite and starch nanocrystals (50/50) is shown to synergistically improves the mechanical properties and thermal stability of starch/poly (vinyl alcohol) blend films prepared via solution casting method. [ABSTRACT FROM AUTHOR]