Radical Grafting Of Maleic Anhydride Research Articles

Peroxide free radical grafting of maleic anhydride onto polyethylene under high melt temperature: A comprehensive approach

“Flash Reactive Extrusion” under very high temperatures (T=200–420°C) allowed to graft maleic anhydride onto polyethylene (PE) without the use of conventional free radical initiators such as peroxides. Herein, the use of unusual temperatures induced the formation of radicals through degradation/chain scission of the PE backbone and the latter radicals were able to react with maleic anhydride (MA) and yielding a MA grafting degree close to 1.4 wt% at 390°C. Moreover, the MA grafting mechanistic scheme was deeply discussed with the help of 1H NMR and 13C NMR analysis and it was pointed out that β-scissions reactions are favoured in comparison with the cross-linking ones at very high temperatures for the thermal initiation step with a MA grafting mainly onto the PE side chain.

Physical and barrier properties of chemically modified pectin with polycaprolactone through an environmentally friendly process

The paper reports the preparation of a novel material composed of pectin chemically modified with polycaprolactone (PCL). PCL was firstly functionalized through radical grafting of maleic anhydride and glycidyl methacrylate in the molten state and then used as grafting agent onto pectins from apple, using a solvent free process. The obtained material was submitted to melt process on laboratory scale and films obtained. Structural, thermal, mechanical, and barrier properties to water vapor were evaluated and compared with pure pectin and modified PCL’s films. The used strategy allowed to overcome the processability problems of a natural polymer, like pectin, that undergoes degradation with the temperature and is not processable without additives and plasticizers. The proposed green process represents a good opportunity to manufacture waste materials from fruits to obtain flexible and fully biodegradable polymers for food packaging applications, as interesting alternative to not biodegradable traditional thermoplastics.

Organically Modified Montmorillonite as Nanoreactor to Improve the Grafting Degree of Maleic Anhydride onto Polypropylene

The application of an organically modified montmorillonite nanoreactor in the reactive extrusion process of the free radical grafting of maleic anhydride onto polypropylene (PP) can increase the MAH grafting degree on the PP. The mechanism of grafting was studied by using transmission electron microscopy and high temperature gel permeation chromatography. It was found that both the strong interactions between MAH and MMT surface and the encapsulation effect of active species confined in o-MMT improved the grafting degree.

Acyloxyimide derivatives as efficient promoters of polyolefin C–H functionalization: application in the melt grafting of maleic anhydride onto polyethylene

Acyloxyimides as a new H-abstracting agent have been developed for the radical grafting of maleic anhydride (MA) onto polyethylene in the melt state.

Effect of nitroxyl-based radicals on the melt radical grafting of maleic anhydride onto polyethylene in presence of a peroxide

The effect of a nitroxyl-based radical scavenger (tretramethyl piperidino radicals, TEMPO or indolynoxyl radicals, DPAIO) on the course of the melt radical grafting of maleic anhydride (MA) onto polyethylene has been explored. The reaction was conducted at 160°C in a mini-extruder with 2,5-dimethyl-2,5-di(tertiobutylperoxy)hexane (Luperox 101-C16H34O4; L101) as hydrogen abstractor. Optimal experimental conditions were defined by varying both L101 concentration and L101/nitroxide molar ratio. The degree of grafting of MA was determined by infra-red spectroscopy and was as high as 0.26wt.% and 0.34wt.% in presence of TEMPO and DPAIO respectively.

Development of Innovative Biopolymers and Related Composites for Bone Tissue Regeneration: Study of Their Interaction with Human Osteoprogenitor Cells

In the framework of a project aiming to improve the properties of poly(ε-caprolactone) (PCL)-based devices, we prepared novel composites and tested their in vitro biocompatibility and osteogenic capacity on human mesenchymal stromal cells (MSC) from bone marrow. We prepared two functionalized derivatives, PCL-g-MAGMA and PCL-g-DMAEA, by insertion of anhydride groups by radical grafting of maleic anhydride (MA) and glycidyl-methacrylate (GMA) molecules, and by insertion of N-(dimethylamino)ethylacrylate (DMAEA) of tertiary amines groups, respectively. In addition, in order to improve the osteoconductive properties of the materials, we also prepared the corresponding composites containing the mineral component of bone, namely hydroxyapatite (HA). Mesenchymal stromal cells (MSC) derived from bone marrow were prepared, plated onto a number of discs obtained from these functionalized derivatives and tested in terms of adhesion and vitality (by MTT test and SEM observation), and the expression of alkaline phosphatase, the early marker of osteoblastic phenotype. The biological in vitro assessment of the functionalized materials, PCL-g-MAGMA and PCL-g-DMAEA, appeared promising only in part, in particular the cells exhibited very poor adhesion to PCL-g-MAGMA. On the contrary, the related composites, PCL-g-MAGMA-HA and PCL-g-DMAEA-HA clearly showed that the addition of HA greatly ameliorated the cell-material interaction. In particular, a surprisingly increased response characterized PCL-g-MAGMA-HA, either in terms of adhesion and vitality or in terms of alkaline phosphatase activity. Altogether these studies showed that the addition of HA nanowhiskers resulted for all basic materials, in particular PCL-g-MAGMA, in improved cell adhesion and performance.

Compatibilizing Effects of Maleated Poly(lactic acid) (PLA) on Properties of PLA/Soy Protein Composites

Poly(lactic acid) (PLA)/soy protein concentrate (SPC) composites were prepared using a twin-screw extruder. Extra amounts of water and glycerol were added to SPC prior to compounding with PLA to ensure that SPC behaved like a thermoplastic during subsequent mixing. Free radical grafting of maleic anhydride (MA) onto PLA was performed by reactive extrusion, and PLA-g-MA was used as a compatibilizer in the composites. The effects of compatibilizer concentration and degree of functionality on the tensile, morphological, and thermal properties of PLA/SPC composites were studied. The tensile strength of the composites containing 4 phr compatibilizer increased by 19% compared to that of the uncompatibilized one. Also, the presence of compatibilizer resulted in finer domain sizes of SPC and a lower damping peak, both of which suggested that good interfacial adhesion between the two phases was achieved. Differential scanning calorimetry analysis indicated that SPC induced and accelerated cold crystallization of PLA.

Polypropylene ionic thermoplastic elastomers: Synthesis and properties

Polypropylene ionic thermoplastic elastomers have been prepared by melt radical grafting of maleic anhydride onto polypropylene in the presence of N-bromosuccinimide followed by neutralization of the resulting elastomeric grafted polypropylene using sodium salts. Sodium hydroxide and sodium acetate were compared in aqueous solution, as anhydrous or hydrated powders. The neutralization reaction was followed by Fourier transform infrared spectroscopy, allowing the development of a method to determine the effective neutralization degree. Important physical changes were recorded upon neutralization. Especially thermal stability, shear storage modulus and complex viscosity in the flow region were largely increased as a function of the neutralization degree.

Poly(trifluoroethylene) Adsorption and Heterogeneous Photochlorination Reactions

Heterogeneous (gas-solid) photochlorination reactions of poly(trifluoroethylene) (PF 3E) films were studied as a function of reaction time and light intensity. The rate of chlorination was found to be faster in high-intensity light when compared to the reaction in ambient light. PF 3E irreversibly adsorbed to oxidized silicon and covalently attached amine monolayers supported on silicon, producing hydrophobic thin films in the thickness range of 8-40 A. Adsorption conditions such as polymer concentration and solvent composition were investigated. Radical grafting of maleic anhydride to the polymer backbone resulted in increased adsorption on oxidized silicon.

Mathematical Modeling of the Grafting of Maleic Anhydride onto Polypropylene

AbstractSummary: A kinetic model for the free radical grafting of maleic anhydride (MAH) onto polypropylene (PP) was developed. The model is able to predict the effect of MAH and initiator concentrations on the grafting degree as well as the changes in the polymer molecular weight distribution during the grafting process. Simulation results are validated by comparison with data from different sources, showing that the model is able to represent reasonably the main trends of the experimentally measured variables both in batch (internal mixer, static film) and in continuous processing (twin‐screw extruder), under different conditions. Model predictions are also compared well with a Monte Carlo simulation previously presented in the literature for the same process.

Modelling of the kinetics of the supercritical CO 2 assisted grafting of maleic anhydride onto isotactic polypropylene in the solid state

This work aimed at comparing and modelling the kinetics of the free radical grafting of maleic anhydride onto polypropylene (PP) in the solid state with and without supercritical CO 2 (scCO 2). The kinetics of the decomposition of dicumyl peroxide (DCP) in scCO 2 and in N 2 was first studied. The one in scCO 2 could be described by k d = 1.32 × 10 14 × exp ( - 139.3 kJ mol - 1 / RT ) . Without scCO 2 the overall grafting reaction rate was controlled, at least partly, by diffusion whereas with scCO 2 it was controlled mainly by the grafting reaction itself. Based on the experimental results, the following general kinetic model for the free radical grafting in scCO 2 was developed: R g = 3.35 × 10 12 × exp ( - 114.5 kJ mol - 1 / RT ) [I] 0.99 [M] 0.97 ( mol L - 1 s - 1 ) .

Neodymium oxide co-catalyzed melt free radical grafting of maleic anhydride onto co-polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd2O3), CO-catalyzed melt grafting of maleic anhydride (MAH) onto co-polypropylene (co-PP) in the presence of dicumyl peroxide (DCP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 as a coagent leads to an enhancement in both MFR and the grafting degree of MAH, along with a simultaneous decrease in the gel content. When the Nd2O3 concentration is 6.0 mmol%, the increment of the grafting degree of MAH maximally is up to about 20% compared with the related system without adding Nd2O3, and the gel content decreases simultaneously to a very low level of about 3%. Attenuated total reflection FTIR (ATR-FTIR) indicates that the gel in the graft copolymers mainly arise from the cross-linking reaction between ethylene units of co-PP. A reasonable reaction mechanism has been put forward on the basis of our experimental results and other mechanisms reported in the literature. We also tentatively explain above results by means of synergistic effect between DCP and Nd2O3, which causes a higher concentration of the macroradical, in particular the tertiary macroradical.

Concept of nano-reactor for the control of the selectivity of the free radical grafting of maleic anhydride onto polypropylene in the melt

The aim of this work was to apply the concept of nano-reactors to the reactive extrusion process of the free radical grafting of maleic anhydride onto polypropylene (PP), an important process in the polymer industry. Pre-confinement of dicumyl peroxide in the lamellar structures of organically modified montmorillonite allowed slowing down the release of primary radicals and consequently to significantly improve the selectivity of the grafting of maleic anhydride onto PP and decrease the selectivity of PP chain scission. To the authors’ knowledge, this is the first time that a non-chemical method is found to solving the inherent problem facing this complicated process: increasing the grafting degree is always concomitant to increasing PP chain scission.

Nano-reactors for controlling the selectivity of the free radical grafting of maleic anhydride onto polypropylene in the melt

This paper reports on a successful application of the concept of nanoreactors to effectively controlling the selectivity of the free radical grafting of maleic anhydride (MAH) onto polypropylene (PP) in the melt, an industrially relevant process. More specifically, a free radical initiator of type ROOR was first confined into (or encapsulated by) the galleries of an organically modified montmorillonite (o-MMT) whose interdistance was 2.4 nm. Primary free radicals (RO center dot) formed inside the o-MMT galleries had to diffuse out before they could react with the PP backbone. The controlled release of the primary free radicals significantly increased the grafting degree of MAH onto PP and greatly reduced the level of the chain scission of the latter. Those results were better understood by electron spin resonance studies on model systems and by Monte Carlo simulations.

Microwave Assisted Radical Grafting of Maleic Anhydride onto Polyethylene in Solution

The reaction of maleic anhydride (MAH) grafted onto low density polyethylene (LDPE) in nylene solvents in the presence of benzoyl peroxide (BPO) as an initiator by microwave irradiation has been investigated. The influence of reaction conditions such as initiator content, monomer content and irradiation time have been examined. In the weight composition of xylene/LDPE/MAH/BPO=10/1/1/0.07, the grafting degree reaches 56.5 mmol MAH/100 g PE within only 8 min of microwave irradiation. The grafting reaction time of microwave irradiation shortens over 40 times than in the conventional grafting reaction.

Morphology development of in situ compatibilized semicrystalline polymer blends in a co‐rotating twin‐screw extruder

AbstractThis paper concerns the morphology development of in situ compatibilized semicrystalline polymer blends in a co‐rotating, intermeshing twin‐screw extruder, using polypropylene (PP) and polyamide 6 (PA‐6) blends as model systems. The morphology of in situ compatibilized blends develops much faster that of mechanical ones. The size of the dispersed phase (PA‐6) undergoes a 104 fold reduction from a few millimeters to sub‐micron during its phase transition from solid pellets to a viscoelastic fluid. The final morphology is reached as soon as the phase transition is completed, which usually requires only a small fraction of the screw length in a co‐rotating twin screw extruder. Screw profiles and processing conditions (screw speed, throughput and barrel temperature) control the PA‐6's melting location and/or rate, but do not have significant impact on the ultimate morphology and mechanical properties of in situ compatibilized blends. The finding that morphology of PP/PA‐6 reactive blend develops rapidly makes it possible to produce compatibilized PP/PA‐6 blends by the so‐called one‐step reactive extrusion. It integrates the traditionally separated free radical grafting of maleic anhydride onto PP and the compatibilization of PP/PA‐6 into a single extrusion step.