Development of thermoplastic composites based on recycled polypropylene and waste printed circuit boards.

In the last several years, the electronic waste, especially printed circuit boards have significantly increased over the world, generating one of the highest rates of solid waste. The recycling process of the printed circuit boards implies mainly the recovery of metals and glass fibers, while the reuse of the polymeric support has remained largely in the phase of research. In this paper, the non-metallic part of printed circuit boards was used as filler (up to 30%), but also to improve the fire resistance of thermoplastic composites based on recycled polypropylene and diene block-copolymers. The synergy between the elastic effect of elastomers and the reinforcing effect of the waste powder into the thermoplastic matrix was studied by mechanical and dynamo-mechanical analysis, X-ray diffraction, optical microscopy, micro-calorimetry and thermo-gravimetrical analysis. Improved mechanical properties, especially impact strength was observed. The compatibization of components considering the interactions between the ethylene-butylene blocks from the hydrogenated and maleinized styrene-butadiene block-copolymer and recycled polypropylene, respectively between the MA groups and the functionalities of the waste powder, evidenced by FTIR, was highlighted by changes in the X-ray pattern and an increased fire resistance and thermal stability.

Nanomaterials Used in Conservation and Restoration of Cultural Heritage: An Up-to-Date Overview.

In the last few years, the preservation of cultural heritage has become an important issue globally, due to the fact that artifacts and monuments are continually threatened by degradation. It is thus very important to find adequate consolidators that are capable of saving and maintaining the natural aspect of these objects. This study aims to provide an updated survey of the main nanomaterials used for the conservation and restoration of cultural heritage. In the last few years, besides the classic nanomaterials used in this field, such as metal nanoparticles (copper and silver) and metal oxides (zinc and aluminum), hydroxyapatite and carbonated derivatives, tubular nanomaterials (such as carbon nanotubes) have been used as a potential consolidate material of cultural heritage. Tubular nanomaterials have attracted attention for use in different fields due to their structures, as well as their ability to present multiple walls. These nanotubes have the necessary properties in preserving cultural heritage, such as superior mechanical and elastic strength (even higher than steel), high hydrophobicity (with a contact angle up to 140°), optical properties (high photodegradation protection), large specific surface area (from 50 to 1315 m2/g, depending on the number of walls) for absorption of other nanomaterials and relatively good biocompatibility.

Methods of synthesis, properties and biomedical applications of polyhydroxyalkanoates: a review.

This study aims to provide an overview of the main polyhydroxyalkanoates (PHAs) used in medical applications. In this review, it has been demonstrated that the properties of PHAs can be controlled both by varying the concentration of units in the copolymer and the substrate for PHA production. Another way of controlling the mechanical properties of PHAs is varying the 3HV content, such as the case of P(3HB-co-3HV). A higher 3HV content in the structure of this polyester will lead to a lower cristallinity and, therefore, to greater flexibility, strength and elongation at break. PHAs are biocompatible, completely biodegradable, and non-toxic. Considering the state of the art technologies and their ideal properties, PHAs (especially the short-chain-length PHA polymers) can be tailored for specific medical applications, such as surgical suture, scaffolds, grafts and heart valves or drug delivery systems. Nowaday, random copolyesters of 3HB and 4HB (P(3HB-co-4HB)) are used for the development of biodegradable implants loaded with antibiotics for therapeutic treatment of chronic osteomyelitis. It is also believed that these biodegradable materials can be efficient alternatives for reducing the pollution produced by the medical waste consisting of replacing plastic handles, packs, syringes or tubes that are trashed into the homes, clinics and hospitals around the world.