Effect of Nanodiamonds on Structure and Durability of Polyethylene Oxide-Based Nanocomposites

Polymer-based nanocomposites containing nanodiamonds (NDs) are attractive multifunctional materials with a growing range of applications. In this work, in the frame of developing completely biocompatible systems, nanocomposites based on polyethylene oxide (PEO) and different amount of NDs have been formulated through melt mixing and fully characterized. In particular, the reinforcement effect of NDs in PEO has been probed through tensile tests, and the rheological response of PEO-based nanocomposites as a function of the nanoparticles amount has been investigated and discussed. The obtained results show that the presence of well-distributed NDs strengthens the mechanical performance of the nanocomposites and brings about an increase of the PEO crystallinity, suggesting a strong adhesion between NDs and polymer matrix. Furthermore, as a result of NDs adding, alterations of the rheological behaviour of neat PEO can be noticed, as NDs are able to significantly influence the long-range dynamics of PEO chains. Besides, accelerated aging tests demonstrate that NDs show a remarkable protective ability against PEO photodegradation, due to their ability to attenuate efficiently UV radiation. The latter opens up new avenues for the use of NDs as multifunctional nanofillers for polymer-based nanocomposites with enhanced photooxidative resistance

Natural Compounds as Sustainable Additives for Biopolymers

In the last few decades, the interest towards natural compounds, coming from a natural source and biodegradable, for biopolymers is always increasing because of a public request for the formulation of safe, eco-friendly, and sustainable materials. The main classes of natural compounds for biopolymers are: (i) naturally occurring fillers (nFil), such as nano-/micro- sized layered alumino-silicate: halloysite, bentonite, montmorillonite, hydroxyapatite, calcium carbonate, etc.; (ii) naturally occurring fibers (nFib), such as wood and vegetable fibers; (iii) naturally occurring antioxidant molecules (nAO), such as phenols, polyphenols, vitamins, and carotenoids. However, in this short review, the advantages and drawbacks, considering naturally occurring compounds as safe, eco-friendly, and sustainable additives for biopolymers, have been focused and discussed briefly, even taking into account the requests and needs of different application fields

Effect of Nanodiamonds on Structure and Durability of Polyethylene Oxide-Based Nanocomposites

Polymer-based nanocomposites containing nanodiamonds (NDs) are attractive multifunctional materials with a growing range of applications. In this work, in the frame of developing completely biocompatible systems, nanocomposites based on polyethylene oxide (PEO) and different amount of NDs have been formulated through melt mixing and fully characterized. In particular, the reinforcement effect of NDs in PEO has been probed through tensile tests, and the rheological response of PEO-based nanocomposites as a function of the nanoparticles amount has been investigated and discussed. The obtained results show that the presence of well-distributed NDs strengthens the mechanical performance of the nanocomposites and brings about an increase of the PEO crystallinity, suggesting a strong adhesion between NDs and polymer matrix. Furthermore, as a result of NDs adding, alterations of the rheological behaviour of neat PEO can be noticed, as NDs are able to significantly influence the long-range dynamics of PEO chains. Besides, accelerated aging tests demonstrate that NDs show a remarkable protective ability against PEO photodegradation, due to their ability to attenuate efficiently UV radiation. The latter opens up new avenues for the use of NDs as multifunctional nanofillers for polymer-based nanocomposites with enhanced photooxidative resistance

Novel strategic approach for the thermo- and photo-oxidative stabilization of polyolefin/clay nanocomposites

Polyolefin/clay nanocomposites were prepared by melt mixing and their oxidative stability was studied under long-term thermo- and photo-oxidative test conditions in the absence and presence of a modified organo montmorillonite clay (OM-MMt) containing a chemically-bound hindered phenol antioxidant function, (AO)OM-Mt. It was found that nanocomposites based on both polyethylene (PE) and polyethylene-grafted-maleic anhydride (PEgMA) containing the (AO)OM-Mt gave a higher oxidative stability, along with better clay dispersion, compared to analogous PE or PEgMA-based nanocomposites containing an added (free) conventional antioxidant with a similar hindered phenol function (using the commercial hindered phenol Irganox® 1076). These findings can be explained in terms of the ability of the organo-modifier containing the in-built antioxidant function to act locally at the interface between the clay silicate layers and the polymer macromolecules thus contributing to the improved stability of the polymer observed both during long-term thermal- and photo-oxidative treatments

Using organoclay to promote morphology refinement and co-continuity in high-density polyethylene/polyamide 6 blends - Effect of filler content and polymer matrix composition

We investigate the gradual changes of the microstructure of two blends of high-density polyethylene (HOPE) and polyamide 6 (PA6) at opposite composition filled with increasing amounts of an organo-modified clay. The filler locates preferentially inside the polyamide phase, bringing about radical alterations in the micron-scale arrangement of the polymer phases. When the host polyamide represents the major constituent, a sudden reduction of the average sizes of the polyethylene droplets was observed upon addition of even low amounts of organoclay. A morphology refinement was also noticed at low filler contents when the particles distributes inside the minor phase. In this case, however, keep increasing the organoclay content eventually results in a high degree of PA6 phase continuity. Rheological analyses reveal that the filler loading at which the polyamide assembles in a continuous network corresponds to the critical threshold for its rheological transition from a liquid- to a gel-like behaviour, which is indicative of the structuring of the filler inside the host PA6. On the basis of this finding, a schematic mechanism is proposed in which the role of the filler in driving the space arrangement of the polymer phases is discussed. Finally, we show that the synergism between the reinforcing action of the filler and its ability to affect the blend microstructure can be exploited in order to enhance relevant technological properties of the materials, such as their high temperature structural integrit

A Fractional-Order Model of Biopolyester Containing Naturally Occurring Compounds for Soil Stabilization

Currently, the use of polymers and biopolymers as soil-stabilizer additives for control of the soil degradation, deterioration, and desertification and for improving the arid and semiarid soils has been expanded significantly in the agricultural sector. This research was conducted to determine the effect of naturally occurring compounds, such as quercetin (Q) and sodium montmorillonite (NaMMt) at different weight ratios, in biopolyester, such as polylactic acid (PLA), aiming to formulate ecosustainable materials to control the soil degradation and to protect the environment. As known, the use of sophisticated analytical tools to describe the material rheology and melting properties is nowadays very popular among physicists and material scientists. Certainly, several experimental tests conducted on polymeric- and biopolymeric-based materials, such as rubbers, foams, and hydro/aero gels, show that the relaxation time spectra are a continuous function, and as a consequence, multiple relaxation times are involved in the rheological description of the materials, yielding the need for nonconventional relaxation functions. Indeed, in this work, the considered fractional-order model could be considered a powerful tool to describe and to predict the melting properties of the complex polymer-based systems containing different additives

Carbon nanotubes-based nanohybrids for multifunctional nanocomposites

In the present work, nano-hybrids based on carbon nanotubes (CNTs) bearing immobilized, either through covalent linkage and physical absorption, commercial anti-oxidant molecules have been formulated and used as nanofillers in Ultra High Molecular Weight Polyethylene (UHMWPE), aiming at preparing multifunctional nanocomposites. The effective immobilization of the anti-oxidant molecules has been probed by spectroscopic and thermogravimetric analyses. The study of the morphology and the rheological behaviour of the nanocomposites show that the immobilization of anti-oxidant molecules onto the CNTs surface is beneficial for the state of the polymer/nanoparticles interfacial region. Additionally, the study of the nanocomposites thermo-oxidative behaviour reveals that the nano-hybrids are able to exert a remarkable anti-oxidant action which is related to the strong interactions established between the anti-oxidant molecules and the CNTs, resulting in the formation of structural defects onto the CNTs surface and in the consequent amplification of the intrinsic CNTs radical scavenging activity

Sonication-induced modification of carbon nanotubes: Effect on the rheological and thermo-oxidative behaviour of polymer-based nanocomposites

The aim of this work is the investigation of the effect of ultrasound treatment on the structural characteristics of carbon nanotubes (CNTs) and the consequent influence that the shortening induced by sonication exerts on the morphology, rheological behaviour and thermo-oxidative resistance of ultra-high molecular weight polyethylene (UHMWPE)-based nanocomposites. First, CNTs have been subjected to sonication for different time intervals and the performed spectroscopic and morphological analyses reveal that a dramatic decrease of the CNT's original length occurs with increased sonication time. The reduction of the initial length of CNTs strongly affects the nanocomposite rheological behaviour, which progressively changes from solid-like to liquid-like as the CNT sonication time increases. The study of the thermo-oxidative behaviour of the investigated nanocomposites reveals that the CNT sonication has a detrimental effect on the thermo-oxidative stability of nanocomposites, especially for long exposure times. The worsening of the thermo-oxidative resistance of sonicated CNT-containing nanocomposites could be attributed to the lower thermal conductivity of low-aspect-ratio CNTs, which causes the increase of the local temperature at the polymer/nanofillers interphase, with the consequent acceleration of the degradative phenomena

MODIFICAZIONI COVALENTI DI NANOTUBI DI ALLOSITE PER APPLICAZIONE NEL DRUG DELIVERY

Nell'ampio scenario dei nanomateriali, i sistemi nanotubolari godono di un consolidato e crescente interesse sia nell'ambito scientifico che industriale. Fra la miriade di sistemi tubolari, recentemente i nanotubi allosite (HNT) hanno attirato l’attenzione della comunità scientifica.1 Grazie alla presenza di una cavità vuota, gli HNT trovano, principalmente, applicazione come nanocontainer per il rilascio controllato di composti chimici, in particolare, farmaci. L’introduzione di modificazioni covalenti su entrambe le superfici permette di modulare le proprietà dell’allosite, aumentando così i suoi campi di applicazione. In questa comunicazione verranno presentati recenti risultati ottenuti mediante la funzionalizzazione covalente della superficie esterna degli HNT con particolari molecole target e la relativa introduzione, nella cavità, di molecole con importanti proprietà biologiche per applicazioni nel campo del drug delivery