Thermo-oxidative stabilization of poly(lactic acid) with antioxidant intercalated layered double hydroxides
Two antioxidant modified layered double hydroxides (AO-LDHs) were successfully prepared by the intercalation of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (IrganoxCOOH) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) in the layered structure of LDH. It was found that by anchoring the phenolic moieties to the LDH layers the antioxidant power is retained in the case of Trolox, and even amplified in the case of IrganoxCOOH. A small amount of the two AO-LDHs was incorporated into poly(lactic acid), PLA, by solution mixing and melt extrusion. The thermo-oxidative stability of the composites was compared with that of the neat PLA and PLA containing free AOs. SEC analy…
Novel organo-modifier for thermally-stable polymer-layered silicate nanocomposites
A new novel approach for the stabilisation of polymer-clay nanocomposites has been investigated based on reacting chemically an antioxidant function, a hindered phenol moiety, with an organic modifier based on a quaternary ammonium salt. The chemically linked antioxidant-containing organic modifier (AO-OM) was then introduced into natural montmorillonite (MMt) through a cation-exchange reaction resulting in antioxidant-containing organo-modified clay (AO-OM-MMt). The new antioxidant-containing modified clay, along with other organo-modified clays having a similar organo-modifier but without the reacted antioxidant, were characterised by spectroscopic, thermogravimetric and x-ray diffraction…
Photo-stabilization of biopolymers-based nanocomposites with UV-modified layered silicates
Abstract Eco-friendly in-situ stabilised biopolymer nanocomposites based on polyamide 11 (PA11) and polylactic acid (PLA) were prepared by melt mixing in the presence of a modified organo-montmorillonite clay containing a chemically-bound hindered amine UV-stabilising function, [(UV)OM-MMt]. Characterisation of the newly synthesised organo-modifier containing the reactive hindered amine (HAS) UV-stabilising function [(UV)OM] has confirmed a successful synthesis. The (UV)OM was then introduced into NaMMt through ion exchange reaction to prepare the UV stabiliser-bound organo-modified-MMt, [(UV)OM-MMt]. The in-situ stabilised PA11- and PLA- nanocomposites (PA11-(UV)OM-MMt and PLA-(UV)OM-MMt) …
Thermo-oxidative stabilization of poly(lactic acid)-based nanocomposites through the incorporation of clay with in-built antioxidant activity
In this work, an innovative approach to overcome the issue of the poor thermo-oxidative stability of polymer/clay nanocomposites is proposed. Specifically, biodegradable poly(lactic acid) (PLA)-based nanocomposites, containing organo-modified clay with in-built antioxidant activity, were prepared. Through a two-step chemical protocol, a hindered phenol antioxidant was chemically linked to the ammonium quaternary salt which was then intercalated between the clay platelets [(AO)OM-Mt]. The nanocomposites were characterized and their thermo-oxidative stability during melt processing and under long-term thermal test conditions was investigated. PLA nanocomposites containing the (AO)OM-Mt showed…
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 …
Effect of extrusion and photoxidation on polyethylene/clay nanocomposites
Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) …