Ionic polymer-metal composites (IPMC) are typical electromechanical transducing materials suitable for use as soft actuators, bioinspired artificial muscles and sensors. However, IPMC produced with platinum films has the great disadvantage of the large number of cracks and wrinkles, which reduce the performance of the electrode. Polyaniline (PANI) is a promising conductive polymer that can address this issue, especially when it is electropolymerized on the platinum surface. An IPMC/PANI actuator was developed by potentiostatic electropolymerization of PANI at 0.9 V in 0.1 M and 0.3 M aniline solution. The characterization revealed that PANI is preferentially electropolymerized in the platinum film cracks and improve the electronic conduction mechanisms, which is not reported so far. The maximum tip displacement of the IPMC/PANI under 5 V was 8.3 mm, while for the IPMC was equal 5.2 mm. These results provide a simple and effective method to repair IPMCs and enhance their electromechanical performances.

Ionomeric Polymer-Metal Composites (IPMCs) are sandwich-like materials based in a polymeric membrane covered on both sides by metallic electrodes. Its operation mechanism consists of hydrated ions migration in response to an external electrical field generated between the electrodes, leading to a spatially nonuniform mass accumulation which causes the device to bend. Its performance as an actuator depends mainly on the environment's relative humidity and electrical stimuli. Consequently, IPMCs present variations in the electromechanical properties exhibiting nonlinearities and time-varying behaviors, limiting the major applications. For this reason, this paper investigated a PI controller performance to overcome these drawbacks and effectively control a Nafion-based IPMC-Li+ exposed to different relative humidities and electrical stimulis. The PI control system uses a camera with a machine vision application as a feedback sensor. Support instrumentation was developed to control the relative humidity, apply an electrical stimulus, and measure the electromechanical response. The pattern recognition algorithm implemented in the controller is efficient, with accuracy above 95%, making the feedback sensor reliable. Therefore, the PI controller was effective, stable, and capable of controlling and characterizing IPMC devices when relative humidity was above 60% at a low-frequency displacement and avoided the undesired back-relaxation phenomenon.

Abstract Ionomeric Polymer-Metal Composites (IPMC) are smart materials whose electromechanical behavior depends on the electrical stimulus intensity, membrane hydration level, and ionic migration. This paper investigates the effects of the voltage, relative humidity, and counterion type (Li+ and K+) on a Nafion-based IPMC performance. Instrumentation capable of applying an electrical stimulus and measuring the electromechanical response was developed. The ionic conductivity was obtained using Electrochemical Impedance Spectroscopy. Complementary SEM analyses were performed before and after actuation cycles. The IPMC performance improved when the electrical stimulus was 5.00 V, RH = 90%, and Li+ was used. The IPMC-Li sample is an excellent candidate to be used as an actuator since it exhibited fast actuation movement, considerable displacement, and no evident back-relaxation. However, its mechanical performance decreased over time because of a progressive increase in platinum electrode crack density and dehydration. The video analysis technique is an efficient, effective, and low-cost technique.

The ionomeric electroactive polymers-metal composites (IPMC) are materials that realize bending movements in response to an electrical stimulus and can be applied to the artificial muscles development. This paper investigated the influence of the hydration level on the electromechanical behavior of Nafion based IPMC. An experimental apparatus composed by a system to measure the bending force and to control the electrical stimulus and the relative humidity around the sample was developed. The main results indicated that samples with higher hydration level produce larger bending forces, but they show a more expressive back relaxation with lower time constant. A discussion about the results considering some models described in the literature conclude the paper.

One of the greatest problems of the modern society is the recycling of vulcanized elastomers, like tires and industrial rejects. This work studies one of the techniques of devulcanization of natural rubber (NR), the devulcanization by microwaves, as well as the influence of the amount of carbon black on this process through devulcanization of the NR with controlled composition on it. The samples were analyzed by Soxhlet extraction and some important correlations could be made based on its results and also by the final temperature of the samples just after the time of exposure to microwaves. The results highlighted that the increase of the temperature is responsible for the occurrence of devulcanization, which is dependent on both the amount of carbon black present in the rubber and the time of exposure to microwaves. These factors can influence its degree of devulcanization, since they are important for the absorption of energy by the material.

AbstractThe main objective of this work is to study the influence of clay addition on dynamically revulcanized blends of Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). GTR was previously devulcanized in a system comprised of a conventional microwave oven adapted with a motorized stirring, with a fixed microwave power and at various exposure times. The influence of clay addition on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties, with morphology being also analyzed. The results depict that the clay can modify the rheological behavior of the GTR phase, in addition to the thermal and mechanical properties of some blends.

<title>Abstract</title><p>The main objective of this work is the study of the influence of microwaves devulcanization of the elastomeric phase on dynamically revulcanized blends based on Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). The devulcanization of the GTR was performed in a system comprised of a conventional microwave oven adapted with a motorized stirring at a constant microwaves power and at various exposure times. The influence of the devulcanization process on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties. The morphology was also studied.</p>

AFM has been recognized as one of the most powerful tools for the analysis of surface morphologies because it creates three-dimensional images at angstrom and nano scale. This technique has been exhaustively used in the analyses of dispersion of nanometric components in nanocomposites and in polymer blends, because of the easiness of sample preparation and lower equipment maintenance costs compared to electron microscopy. In this review, contributions using AFM are described, with emphasis on the dispersion of nanofillers in polymeric matrices. It is aimed to show the importance of technical analysis for nanocomposites and polymer blends based on elastomers.