5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications

Natural fibers today are a popular choice for applications in composite manufacturing. Based on the sustainability benefits, biofibers such as plant fibers are replacing synthetic fibers in composites. These fibers are used to manufacture several biocomposites. The chemical composition and properties of each of the fibers changes, which demands the detailed comparison of these fibers. The reinforcement potential of natural fibers and their properties have been described in numerous papers. Today, high performance biocomposites are produced from several years of research. Plant fibers, particularly bast and leaf, find applications in automotive industries. While most of the other fibers are explored in lab scales they have not yet found large-scale commercial applications. It is necessary to also consider other fibers such as ones made from seed (coir) and animals (chicken feather) as they are secondary or made from waste products. Few plant fibers such as bast fibers are often reviewed briefly but other p...

A Review of Natural Fibers Used in Biocomposites: Plant, Animal and Regenerated Cellulose Fibers

A review on new bio-based constituents for natural fiber-polymer composites

Manipulation and navigation of micro and nanoswimmers in different fluid environments can be achieved by chemicals, external fields, or even motile cells Many researchers have selected magnetic fields as the active external actuation source based on the advantageous features of this actuation strategy such as remote and spatiotemporal control, fuel-free, high degree of reconfigurability, programmability, recyclability, and versatility This review introduces fundamental concepts and advantages of magnetic micro/nanorobots (termed here as "MagRobots") as well as basic knowledge of magnetic fields and magnetic materials, setups for magnetic manipulation, magnetic field configurations, and symmetry-breaking strategies for effective movement These concepts are discussed to describe the interactions between micro/nanorobots and magnetic fields Actuation mechanisms of flagella-inspired MagRobots (ie, corkscrew-like motion and traveling-wave locomotion/ciliary stroke motion) and surface walkers (ie, surface-assisted motion), applications of magnetic fields in other propulsion approaches, and magnetic stimulation of micro/nanorobots beyond motion are provided followed by fabrication techniques for (quasi-)spherical, helical, flexible, wire-like, and biohybrid MagRobots Applications of MagRobots in targeted drug/gene delivery, cell manipulation, minimally invasive surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery, pollution removal for environmental remediation, and (bio)sensing are also reviewed Finally, current challenges and future perspectives for the development of magnetically powered miniaturized motors are discussed

Magnetically Driven Micro and Nanorobots

Cracks, microcracks and fracture in polymer structures: Formation, detection, autonomic repair

The transient response of elastomeric polymers is dependent on polymer composition, temperature and the loading history. In particular, hysteresis, dissipation and creep are significant in the choice of material for elastomer membrane wave energy converters. Natural rubber is a good candidate when looking for material for a wave energy harvester since it has an excellent stretchability, is almost resistant to the environment in which the harvester will be used and has good fatigue properties. The mechanical behaviour of the natural rubber used in this work has been deeply characterised: the material resulted to have a very little hysteretical behaviour (that is a very low energy dissipation during stretching) but also to show a strain-dependency, stress softening, and relaxation at constant stretch. Low dissipation represents the best case scenario for energy harvesting; in reality reinforcement of the material is required which adds to the dissipative behaviour. Afterwards, an extended finite strain viscoelastic constitutive model is proposed that is calibrated analytically to the experimental data to identify the relevant material parameters resulting in non-linear viscosity functions in the evolution equations of the constitutive model. The model was able to capture the minimal dissipation behaviour with good degrees of accuracy. Results are shown for a flexible membrane wave energy converter under creep and cyclic loading. A parametric study is made comparing the experimentally characterised polymer with different amounts of viscous dissipation. The response of the wave energy converter shows that even minimal amounts of dissipation manifests itself into changes in the pressure–volume function and reduction in energy capture through hysteresis. The new material model shows, for the first time, that the control of internal pressure in wave energy membranes must take into account transient material effects. 

On the influence of time-dependent behaviour of elastomeric wave energy harvesting membranes using experimental and numerical modelling techniques

Mechanical characterization of carbon black filled NR/BR compounds from small strains up to fracture

The viscoelastic nature of polymers influences the material’s behaviour not only during its deformation up to strains beyond yielding, but also during and after its unloading. In the present work the recovery of the strain after the removal of the applied stress was studied as a function of time and temperature on rubber toughened polymethylmethacrylates (RTPMMAs). Constant strain rate tests under uniaxial tensile loading were performed at room temperature on three RTPMMAs, differing in dispersed phase content. Identical samples were deformed up to the same strain level and then unloaded. The residual strain was measured as a function of time at different constant temperatures. By applying a time–temperature equivalence, a residual strain versus time master curve was obtained and the relevant shift factors were determined. Isothermal strain recovery on samples deformed up to the same strain was also measured at different temperatures, in the range between room temperature and the material’s glass transition temperature. The residual strain after a given time was plotted as a function of temperature, obtaining an isochronous strain-recovery curve. Using the appropriate shift factors, an isothermal strain-recovery curve was then determined. The latter and the strain-recovery master curve are similar in the range of time over which recovery takes place, although an effect of the applied strain level on the curves’ shape was observed. The effects of the applied strain level and of the rubber particles content on the strain-recovery kinetics were evaluated.

Strain-Recovery Kinetics in Rubber Toughened Polymethylmethacrylate

Tecnologie dei materiali polimerici e dei materiali compositi

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Claudia Marano

Papers

On the influence of time-dependent behaviour of elastomeric wave energy harvesting membranes using experimental and numerical modelling techniques

Mechanical characterization of carbon black filled NR/BR compounds from small strains up to fracture

Strain-Recovery Kinetics in Rubber Toughened Polymethylmethacrylate

Tecnologie dei materiali polimerici e dei materiali compositi

Constitutive Models for Rubber XII