Igor Krupa

Elastomeric photo-actuators and their investigation by confocal laser scanning microscopy

The photo-actuation behavior of nanocomposites based on ethylene–vinylacetate copolymer (EVA) and styrene–isoprene–styrene (SIS) block copolymer filled with well-dispersed and modified multiwalled carbon nanotubes (MWCNTs) is discussed in this paper. The nanocomposites were prepared by casting from solution. To improve the dispersion of the MWCNTs in EVA, the MWCNT surface was modified with a non-covalent surfactant, cholesteryl 1-pyrenecarboxylate (PyChol). To prepare SIS nanocomposites, the MWCNT surface was covalently modified with polystyrene chains. The good dispersion of the filler was confirmed by transmission electron microscopy (TEM). Special, custom-made punch/die molds were used to create a Braille element (BE)-like shape, which under shear forces induces a uniaxial orientation of the MWCNTs within the matrix. The uniaxial orientation of MWCNTs is an essential precondition to ensure the photo-actuating behavior of MWCNTs in polymeric matrices. The orientation of the MWCNTs within the matrices was examined by scanning electron microscopy (SEM). Nanocomposite BEs were illuminated from the bottom by a red light-emitting diode (LED), and the photo-actuation was investigated by confocal laser scanning microscopy (CLSM). When the BEs were exposed to light, a temporary increase in the height of the element was detected. This process was observed to be reversible: after switching off the light, the BEs returned to their original shape and height.

Polyolefin in Packaging and Food Industry

The commonly used food packaging polymers are polyolefins, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), isotactic polypropylene (PP), and some polyethylene-based copolymers.

Polyolefins in Automotive Industry

Polyolefins in automobiles have experienced a great deal of interest in the last twenty years, and their applications have been increasing with a tendency of further growth compared with other materials used in automobiles. The major advantages of polyolefin materials are their functionality, cost-effective manufacturing methods, and comparatively lower fuel consumption. In automobiles, the polymeric materials can be used in the internal and external areas, in the engine section, and in the bodywork. Polyolefin can be shaped easily, their surface can be smooth, and they are chemically resistant, lighter than metals and glass, and are also good insulators. All these good properties make the polyolefin popular in the field of automotive industry.

Chapter 1 - Overview: Clay Preparation, Properties, Modification

This chapter was made possible by NPRP award [8-878-1-172] from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.

Polyolefin Adhesion Modifications

Polyolefins exhibit excellent properties and the knowledge of their adhesion that are very important for many applications such as those in packaging, building, automobile, aeronautic, aerospace, electronics, and sport industries. Poor surface adhesion represents a serious problem in situations where other laminates, films, or metallic layers are imparted onto polyolefins. Adhesion represents the contact between two solids, for instance, in coatings, polymer blends, paints, multilayered sandwiches, adhesive joints, or composites materials.

In situ electron microscopy of Braille microsystems: photo-actuation of ethylene vinyl acetate/carbon nanotube composites

The development of new types of tactile displays based on the actuation of composite materials can aid the visually impaired. Micro/nano systems based on ethylene vinyl acetate (EVA) polymeric matrices enriched with multiwalled carbon nanotubes (MWCNT) can produce ensembles capable of light-induced actuation. In this report, we investigate two types of commercial EVA copolymers matrices containing 28 and 50 wt% vinyl-acetate (VA). Non-covalent modification of carbon nanotubes was achieved through a compatibilization technique that appends the pyrenenyl and cholesteryl groups on the carbon nanotubes (CNTs) surface. EVA/MWCNT nanocomposites were prepared by casting from a solution. These composites were shaped into Braille elements using molds. The deformation of the Braille element (BE) under light-emitting diode (LED) illumination was observed for the first time by in situ scanning electron microscopy (SEM). The superior actuation performance promoted by the EVA/MWCNT nanocomposites indicates that these materials will be useful in the future as light-driven micro/nano system actuators.

Elastomeric Actuators Based on Ethylene-Vinyl Acetate and Carbon Nanotubes

The development of new types of visual-aid tablet for visually impaired people requires the development of cheap, but still very effective photoactuating materials. This requirement can be satisfied by the use of new kind of elastomers filled by nanofillers, such as carbon nanotubes. Nanocomposites based on commercial ethylene vinyl-acetate (EVA) copolymer and multiwalled carbon nanotubes (MWCNT) were prepared by casting from solution. The non-covalent surface modification of MWCNT was carried out by special, newly synthesized compatibilizer cholesteryl 1-pyrenecarboxylate (PyChol). In order to mimic Braille character, special home-built silicone punch and die moulds were used. The Braille element based on EVA/MWCNT-PyChol composite displays reversible, multiple changes of dimension in the direction of the irradiation during/upon illumination by red and blue light-emitted diode (LED). Transmission electron microscopy (TEM) showed a good dispersion of the MWCNT-PyChol within the matrix. The Braille element behaviour under illumination was analysed by atomic force microscopy (AFM) and by nanoindentor. Nanoindentor, even if the purpose of its original use is different, can be effectively applied for the determination of the actuation stroke, the sample dimensional changes in the direction of irradiation.