For the last decades, nanocomposites materials have been widely studied in the scientific literature as they provide substantial properties enhancements, even at low nanoparticles content. Their performance depends on a number of parameters but the nanoparticles dispersion and distribution state remains the key challenge in order to obtain the full nanocomposites’ potential in terms of, e.g., flame retardance, mechanical, barrier and thermal properties, etc., that would allow extending their use in the industry. While the amount of existing research and indeed review papers regarding the formulation of nanocomposites is already significant, after listing the most common applications, this review focuses more in-depth on the properties and materials of relevance in three target sectors: packaging, solar energy and automotive. In terms of advances in the processing of nanocomposites, this review discusses various enhancement technologies such as the use of ultrasounds for in-process nanoparticles dispersion. In the case of nanocoatings, it describes the different conventionally used processes as well as nanoparticles deposition by electro-hydrodynamic processing. All in all, this review gives the basics both in terms of composition and of processing aspects to reach optimal properties for using nanocomposites in the selected applications. As an outlook, up-to-date nanosafety issues are discussed.

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Review on the Processing and Properties of Polymer Nanocomposites and Nanocoatings and Their Applications in the Packaging, Automotive and Solar Energy Fields.

During the resorbable-polymer-boom of the 1970s and 1980s, polycaprolactone (PCL) was used in the biomaterials field and a number of drug-delivery devices. Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption pathways; consequently, PCL was almost forgotten for most of two decades. Recently, a resurgence of interest has propelled PCL back into the biomaterials-arena. The superior rheological and viscoelastic properties over many of its aliphatic polyester counterparts renders PCL easy to manufacture and manipulate into a large range of implants and devices. Coupled with relatively inexpensive production routes and FDA approval, this provides a promising platform for the production of longer-term degradable implants which may be manipulated physically, chemically and biologically to possess tailorable degradation kinetics to suit a specific anatomical site. This review will discuss the application of PCL as a biomaterial over the last two decades focusing on the advantages which have propagated its return into the spotlight with a particular focus on medical devices, drug delivery and tissue engineering.

The return of a forgotten polymer : Polycaprolactone in the 21st century

Can nanoparticles really enhance thermal stability of polymers? Part I: An overview on thermal decomposition of addition polymers

Living tissues, such as muscle, autonomously grow and remodel themselves to adapt to their surrounding mechanical environment through metabolic processes. By contrast, typical synthetic materials cannot grow and reconstruct their structures once formed. We propose a strategy for developing “self-growing” polymeric materials that respond to repetitive mechanical stress through an effective mechanochemical transduction. Robust double-network hydrogels provided with a sustained monomer supply undergo self-growth, and the materials are substantially strengthened under repetitive loading through a structural destruction-reconstruction process. This strategy also endows the hydrogels with tailored functions at desired positions by mechanical stamping. This work may pave the way for the development of self-growing gel materials for applications such as soft robots and intelligent devices.

Mechanoresponsive self-growing hydrogels inspired by muscle training

Statistical models in engineering , Statistical models in engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Statistical Models in Engineering

The objective of this work is to evaluate the capability of an advanced constitutive model, namely the Three Network Model (TNM) of simulating the mechanical response of HDPE liners undergoing buckling collapse. In order to determine the input parameters for the model, a series of tensile and compressive uniaxial tests were conducted. Simulations were performed using Finite element modeling (FEM) analysis with the ABAQUS 6.10 package. The complex strain rate, temperature and pressure dependent mechanical response of HDPE was analyzed by modeling the dynamic event as an increasing volume of fluid entering the gap cavity between liner and host pipe, and a mathematical relationship between fluid flow rate and collapse pressure was proposed.

Constitutive modeling and Computational Simulations of the external pressure induced buckling collapse of High Density Polyethylene (HDPE) liners

Threshold toughness of polymers in the ductile to brittle transition region by different approaches

Fracture and mechanical characterization of bone composite composed of polymethylmethacrylate and hydroxyapatite (HA) at different contents was carried out. Hydroxyapatite is added in order to improve cement biocompatibility, but it is expected that it also affects mechanical properties. Specimens were either stored in air at 37°C for 120 h or in physiological solution (PhS-37), in order to establish the influence of storage conditions upon mechanical behavior. One set of specimens was also postcured at 120°C for 4 h to take into account the influence of free monomer. Fracture experiments revealed some non-linearity in load–displacement records and differences in trends between initiation and propagation values of the fracture surface energies. The trends in the data shows that HA acts as a rigid filler enhancing fracture resistance, flexural modules and yield stress, up to a certain content. Beyond the latter limit, properties suffer a deterioration because the addition of HA also affects the cement porosity. Absorbed water acts as plasticizer leading to a decrease in mechanical properties. The highest propagation strain energies were exhibited by materials aged in PhS-37. ©1999 Kluwer Academic Publishers

Fracture evaluation of acrylic bone cements modified with hydroxyapatite: influence of the storage conditions.

Batch and continuous reactors for the production of novolacs

Starting from the mathematical structure and kinematic framework of the Arruda-Boyce viscoplastic model, a great variety of ideas can be tested to develop advanced constitutive models for polymers, biomaterials and soft tissues. Moreover, the primitive Arruda-Boyce constitutive model has been the cornerstone for the development of quite sophisticated models to reproduce large-strain mechanical behavior of polymers and soft biological tissues.
However, it is noteworthy that it is still impossible to find a scientific article (or book) providing a detailed description of explicit or implicit integration schemes for this constitutive model. In fact, it is quite difficult to find numerical implementations of any unified viscoplastic model. For that reason, the authors present in this article two simple integration algorithms for the Arruda-Boyce viscoplastic model, one them explicit and the other one implicit.
The development of this algorithms required a thorough bibliographical review, searching and collecting the most convenient numerical strategies, revision of standard numerical practices (and eventually their avoidance) and of course the inclusion of the own ideas of the authors. The final result is a meticulous combination of elements which were carefully assembled into two numerical material routines, which up to the present date, have worked satisfactorily with all the finite element analyses carried out by the authors.

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Patricia Maria Frontini

Papers

Constitutive modeling and Computational Simulations of the external pressure induced buckling collapse of High Density Polyethylene (HDPE) liners

Threshold toughness of polymers in the ductile to brittle transition region by different approaches

Fracture evaluation of acrylic bone cements modified with hydroxyapatite: influence of the storage conditions.

Batch and continuous reactors for the production of novolacs

Accurate, Efficient and Robust Explicit and Implicit Integration Schemes for the Arruda-Boyce Viscoplastic Model