Search results for " DEGRADATION"
showing 10 items of 510 documents
Long-term ISO 23936-2 sweet oil ageing of HNBR
2021
Abstract A hydrogenated nitrile butadiene rubber (HNBR) compound is subjected to ageing in a simulated oil and gas environment in accordance with ISO 23936-2 standard at two elevated temperatures (130 °C and 150 °C) for a period of up to 9 months. Shore D hardness, thermal expansion, dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, compression and compression set (CS) measurements are made before and after the chemical exposure. The hardness, modulus at short times, degree of relaxation and CS increases while the coefficient of thermal expansion in HNBR tends to decrease with ageing time and temperature. Temperature is shown to impose a greater effect on th…
Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechani…
2012
[EN] This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PLA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PLA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystalli…
Effect of processing temperature and mixing time on the properties of PP/GnP nanocomposites
2020
Abstract During processing of molten polymers the thermal and mechanical stress acting on the melt in presence of oxygen can induce degradation with a modification of the chemical structure of the polymers. This picture can become even more relevant if the melt is a multiphasic polymer system. In this last case, the effects of the degradation depend also on the presence of a second phase and on the interactions between the two phases. In this work, the effect of the processing conditions, temperature and time, have been considered in order to investigate the thermo-mechanical and thermo-oxidative degradation of nanocomposites made by polypropylene and different contents of graphene nanoplat…
Degradation and Recycling of Films Based on Biodegradable Polymers: A Short Review
2019
The environmental performance of biodegradable materials has attracted attention from the academic and the industrial research over the recent years. Currently, degradation behavior and possible recyclability features, as well as actual recycling paths of such systems, are crucial to give them both durability and eco-sustainability. This paper presents a review of the degradation behaviour of biodegradable polymers and related composites, with particular concern for multi-layer films. The processing of biodegradable polymeric films and the manufacturing and properties of multilayer films based on biodegradable polymers will be discussed. The results and data collected show that: poly-lactic…
Degradation of polymer blends: A brief review
2017
Abstract The usefulness of any material, including polymer blends, depends on its degradability and durability. The blend composition can significantly affect the degradative behavior of a polymer blend and can differ from the degradation routes of the pure components since the interactions among different species in the blends during degradation, and among the degradation products, can occur. These reactions can lead either to an acceleration of the degradation rate or to a stabilizing effect in comparison with the pure components. Thus, the additive rule cannot be often applied in case of degradation of polymer blends and, therefore, it is difficult to predict the degradative behavior of …
Dielectric Spectroscopy of Recycled Polylactide
2014
The effects of multiple mechanical recycling on amorphous polylactide (PLA) were simulated by means of five successive injection-grinding cycles. The influence of the induced thermo-mechanical degradation on the dielectric properties of PLA was analysed. The relaxation spectra were studied in terms of the complex dielectric permittivity (ε0 and ε00) and the dielectric loss tangent, tg(d) in the frequency range from 102 to 107 Hz over the temperature interval from 0 C to 140 C. It was possible to distinguish two relaxations zones, one at low temperatures and high frequencies (b relaxation) and another at higher temperatures and lower frequencies (a relaxation). The individual relaxations wer…
Salt spray fog ageing of hybrid composite/metal rivet joints for automotive applications
2017
Abstract The present experimental investigation aims to investigate the effect of salt-fog exposition on the mechanical behaviour of composite/metal riveted joints. To this aim, two kinds of joint were exposed to salt-fog environmental conditions according to ASTM B117 standard, for fifteen weeks. In particular, two composite laminates (i.e. glass fibre and carbon fibre/epoxy composites) were used as composite substrate joined with the metal substrate (i.e. aluminium alloy Al 6060). Single-lap shear tests were carried out in order to evaluate the evolution of the mechanical performances and the damage mechanisms of the riveted joints during the ageing exposition. The results evidence that t…
Aging resistance of bio-epoxy jute-basalt hybrid composites as novel multilayer structures for cladding
2017
Abstract Aging resistance of jute reinforced laminates is compared with two jute/basalt hybrid laminates prepared with different stacking sequences (i.e., sandwich and intercalated configuration). To this aim, composites are exposed to cyclic conditions comprising hygrothermal stress and UV radiation to promote an accelerated aging, for a period of 84 days. Specimens of each laminate are tested after 14, 28, 56 and 84 days, respectively. Quasi-static flexural tests, Charpy impact tests and dynamic mechanical tests are performed according to international ASTM and ISO standards. Furthermore, scanning electron microscopy and differential scanning calorimetry are used to evaluate the morpholog…
Polylactide-based self-reinforced composites biodegradation: Individual and combined influence of temperature, water and compost
2018
[EN] Self-reinforced polymer composites (SRCs) are proposed as a suitable alternative for composite development, based in the combination of a polymeric matrix and a polymeric fibre made of the same polymer. SRCs based in polylactide (PLA) could be fully biodegradable and their valorisation routes could presumably be assimilated to those for neat PEA. In this sense, the aim of this study was to develop new self-reinforced PLA-based composites and ascertain their biodegradability. For this purpose, PLA-based SRCs were obtained through a thermo-compression procedure and their biodegradability corroborated under standard conditions (ISO 20200). Moreover, a deep study of the effect of the diffe…
Grafting of Maleic Anhydride onto Isotactic Polypropylene in the Presence of Supercritical Carbon Dioxide as a Solvent and Swelling Fluid
2004
Grafting of maleic anhydride (MA) onto isotactic polypropylene (iPP) was carried out by thermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO2) as a solvent and swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO2 is higher than 1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and with a proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to the polymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy and polymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA a…