EVOH Copolymer Research Articles

TGA coupled with FTIR gas analysis to quantify the vinyl alcohol unit content in ethylene-vinyl alcohol copolymer

Thermo-gravimetric analysis coupled to time/temperature-resolved FTIR spectroscopy of evolved gases was used to measure the vinyl alcohol units content in EVOH copolymer. Pure homopolymers were used as references. The quantitative analysis here proposed is based on the calculation of integral profiles relative to FTIR signals of water molecules evolved during the thermal degradation (pyrolysis) of vinyl alcohol units.

Antioxidant Packaging Films Based on Ethylene Vinyl Alcohol Copolymer (EVOH) and Caffeic Acid.

The main objective of this research activity was to design and realize active films with tunable food functional properties. In detail, caffeic acid (CA), a polyphenol with high antioxidant effect, was used as active ingredient in poly (vinyl alcohol-co-ethylene) (EVOH) films at 5 wt.% and 15 wt.% and successfully realized by means of the solvent casting process. Optical, morphological, thermal and mechanical studies were considered to define the effect of the presence of the CA component on the structural properties of the matrix. In addition, moisture content and antioxidant activity were evaluated, to have clear information on the CA effect in terms of functional characteristics of realized food packaging systems. Results from tensile tests showed increased values for strength and deformation at break in EVOH_CA based films. Results from colorimetric and transparency analysis underlined that the presence of caffeic acid in EVOH copolymer induces some alterations, whereas the addition of the active ingredient determined a positive radical scavenging activity of the formulations, confirming the possibility of practically using these polymeric systems in the food packaging sector.

Outcome of Endovascular Treatment of Cerebral Arteriovenous Malformations with Ethylene Vinyl Alcohol Coploymer

Abstract Background Cerebral AVMs are very rare lesions, and this rarity contributes to the difficulty of treating them. There is no consensus concerning the method of treatment to be chosen among neurosurgery, radiosurgery or embolization. Onyx embolization could serve as a curative option with accepted morbidity and mortality. The introduction of Onyx and of catheters with detachable tips has no doubt increased the rate of endovascular occlusion, and decreased the risks associated with treatment in our experience. Objective The aim of the study was to assess the outcome of the use of Onyx in the treatment of intracranial AVMs as curative embolization or before neuro- or radiosurgery Patients and Methods This analytical prospective study was conducted on 25 patients who were diagnosed with cerebral arteriovenous malformations and underwent endovascular embolization with EVOH copolymer with curative intent during the study period. Interventional procedures were done in the neuro – endovascular unit, neurosurgery department Ain Shams University Hospitals and associate neuroendovascular unit in El Matarya Teaching Hospital in the period between September 2014 and April 2017. Results Actually comparing these results especially concerning the cure rate along with other studies was somewhat confusing and problematic owing to the diversity in results between studies across the last 15 years. Conclusion For the cases that are not fulfilling these criteria, embolization should be offered as preparing step for other modality of treatment. In our experience, for curative embolization, the AVM should be small sized (< 3 cm), supplied by one vascular territory, with feeders that can tolerate reflux up to 2–3 cm, with clear proximal parts of the draining veins, and not located in deep structures.

Active Role of ZnO Nanorods in Thermomechanical and Barrier Performance of Poly(vinyl alcohol-co-ethylene) Formulations for Flexible Packaging.

Poly(vinyl alcohol-co-ethylene) (EVOH) films containing zinc oxide nanorods (ZnO Nrods) at 0.1, 0.5, and 1 wt%, were realized by solvent casting. The effect of ZnO Nrods content on morphological, thermal, optical, mechanical, and oxygen permeability properties were analyzed. In addition, moisture content and accelerated-aging test studies were performed, with the intention to determine the influence of zinc oxide nanofillers on the functional characteristics of realized packaging systems. Tensile properties showed increased values for strength and deformation-at-break in EVOH-based formulations reinforced with 0.1 and 0.5 wt% of zinc oxide nanorods. Results from the colorimetric and transparency investigations underlined that the presence of ZnO Nrods in EVOH copolymer did not induce evident alterations. In addition, after the accelerated-aging test, the colorimetric test confirmed the possibility for these materials to be used in the packaging sector. This behavior was induced by the presence of zinc oxide nanofillers that act as a UV block that made them useful as an efficient absorber of UV radiation.

Outcome of Endovascular Treatment of Cerebral Arteriovenous Malformations with Ethylene Vinyl Alcohol Coploymer

Background: Cerebral AVMs are very rare lesions, and this rarity contributes to the difficulty of treating them. There is no consensus concerning the method of treatment to be chosen among neurosurgery, radiosurgery or embolization. Onyx embolization could serve as a curative option with accepted morbidity and mortality. The introduction of Onyx and of catheters with detachable tips has no doubt increased the rate of endovascular occlusion, and decreased the risks associated with treatment in our experience. Objective: The aim of the study was to assess the outcome of the use of Onyx in the treatment of intracranial AVMs as curative embolization or before neuro- or radiosurgery Patients and Methods: This analytical prospective study was conducted on 25 patients who were diagnosed with cerebral arteriovenous malformations and underwent endovascular embolization with EVOH copolymer with curative intent during the study period. Interventional procedures were done in the neuro –endovascular unit, neurosurgery department Ain Shams University Hospitals and associate neuroendovascular unit in El Matarya Teaching Hospital in the period between September 2014 and April 2017. Results: Actually comparing these results especially concerning the cure rate along with other studies was somewhat confusing and problematic owing to the diversity in results between studies across the last 15 years. Conclusion: For the cases that are not fulfilling these criteria, embolization should be offered as preparing step for other modality of treatment. In our experience, for curative embolization, the AVM should be small sized (< 3 cm), supplied by one vascular territory, with feeders that can tolerate reflux up to 2–3 cm, with clear proximal parts of the draining veins, and not located in deep structures.

Development of PLA‐PHB‐based biodegradable active packaging and its application to salmon

In this study, poly (lactic acid)‐poly (hydroxybutyrate) (PLA‐PHB) based films containing bioactive elements were developed and characterized. Seven formulations containing different contents of plasticizers (mono‐caprylin glycerate (GMC) or glycerol monolaurate (GML)) were initially developed. After basic mechanical property tests, the PLA‐PHB‐based films with 0.5% GMC or GML were selected as 2 formulations for further study. In the subsequent experiments, 5% cinnamaldehyde was added into each of the 2 formulations selected and EVOH copolymer (widely used nonbiodegradable packaging as control here) respectively. More mechanical and active properties were investigated. The results showed that PLA‐PHB‐based films possessed some better mechanical properties than those of EVOH‐based film, and better active properties when applied to high lipid food simulant. In a preservative test, changes in total bacterial counts, thiobarbituric acid, and total volatile basic nitrogen were carried out on salmon dices packed with films and stored at 4 ± 1°C. It was only 4.65 CFU/g on day 17 for the salmon packed with PLA‐PHB‐based film with GML as plasticizer; meanwhile, the total bacterial counts of salmon dices sealed in other 2 films reached 6.65 and 6.35 CFU/g respectively on day 15. This study showed that it could be feasible to use biodegradable active packing as an alternative to replace nonbiodegradable packaging for chilled salmon.

Effect of gallic acid and umbelliferone on thermal, mechanical, antioxidant and antimicrobial properties of poly (vinyl alcohol-co-ethylene) films

Poly(vinyl alcohol-co-ethylene) (EVOH) films containing two different active ingredients (AIs), gallic acid (GA) and umbelliferone (UMB) at 5 wt % and 15 wt %, were successfully produced by solvent casting and extrusion. The effects of process techniques, AIs presence, typology and content on optical, morphological, thermal and mechanical properties of EVOH based films have been investigated. In addition, moisture content, migration and radical scavenging activity, antimicrobial and antifungal studies were performed, with the aim of evaluating the effect of AIs on structural and functional properties of realized food packaging systems. Results from colorimetric and transparency investigation underlined that the presence of AIs in EVOH copolymer induced important alterations, whereas migration to food simulant data restricted the use of produced films to the contact with fatty foods. On the other hand, the use of AIs clearly induced positive antioxidant response, inhibitions of bacterial and antifungal growth, confirming the possibility of practically using these materials in the food packaging sector.

Packaging material type affects the quality characteristics of Aloe- probiotic lassi during storage

Abstract The efficacy of different packaging materials with varying oxygen barrier properties on the shelf-life of Aloe vera supplemented probiotic lassi (APL) was investigated. APL was packaged in different packaging materials viz. glass bottle, EVOH co-polymer, PET bottle and LDPE pouches (~200 ml capacity). APL packaged in LDPE was treated as control. APL samples were stored under refrigeration conditions (5 ± 1 °C) for 30 days during which changes in probiotic count, sensorial and physico-chemical properties were evaluated. Results showed that oxygen permeation rates of packaging materials influenced the shelf-life of APL. APL packaged in high barrier materials viz. EVOH and glass bottle showed improved probiotic viability and sensory quality followed by higher viscosity. Rate of post-acidification and pH drop were also higher in APL samples packaged in EVOH and glass bottles. APL samples stored in EVOH co-polymer and glass bottles were acceptable up to 25 days without any undesirable changes in quality attributes and the probiotic survivability was above 106 cfu/ml.

Influence of zeolite nanoparticles on photostability of ethylene vinyl alcohol copolymer (EVOH)

New ethylene vinyl alcohol copolymer EVOH nanocomposites based on zeolite particles were processed by solution or melt-mixing to synthesise potential encapsulants for flexible organic solar cells (OSC). The photochemical behaviour of pristine EVOH copolymer and the influence of zeolite particles with different size and increasing nanoparticle loading were studied to evaluate the photostability of such packaging materials. Photooxidation of pristine EVOH films (with two different ethylene unit contents (27% or 44%) was performed under accelerated artificial conditions that allow for the proposal of a comprehensive mechanism of EVOH oxidation. The photochemical behaviour of EVOH/zeolite nanocomposites with different morphology and size of particles was compared, revealing a higher oxidation of the polymer in the presence of zeolite particles, which can be mainly attributed to iron impurities.

Abstract No. 462 - Lymphatic intervention for various kinds of lymphorrhea

tion has been shown to be effective in the treatment of recurrent chylous effusions. Many embolic agents have been described in the successful occlusion of the thoracic duct. In this study, we evaluate the role and efficacy of using EVOH copolymer (Onyx) in the treatment of traumatic chylous pleural effusions. Background: A retrospective review was performed of consecutive patients with post-operative chylous pleural effusions treated with thoracic duct embolization using EVOH copolymer at a single institution from 2012-2014. Demographic data, surgical history, procedure details, and toxicities were systematically reviewed. Clinical Findings/Procedure Details: 4 patients (M1⁄42) were identified that met inclusion criteria. Median age at treatment was 67. Median follow was 125 days (range 24-246). Two patients had undergone robotic assisted surgery and 2 had undergone open thoracotomy. 3 patients had thoracic duct ligation performed at the time of their initial surgery. Median time from surgery to embolization was 7 days (range 3-15). Daily chest tube drainage range was 150 -2000 ml. All patients underwent bilateral ultrasound guided inguinal nodal lymphangiogram. The thoracic duct was then accessed using a 21 or 22 gauge Chiba needle. A thoracic duct leak was identified in 3 patients. Coils were placed initially in the central duct prior to embolization of the leak limit potential systemic flow. Onyx 34 (ev3 Neurovascular, Irvine, California) was used in 4 patients with additional Onyx 18 in 1 patient for embolization. Volume used was 1-2 ml in all patients. All patients had resolution of the chylous effusion within 1 day of embolization. The subjects were discharged from the hospital between 4-7 days post-procedure. 30 days post-procedure complications included an abdominal wall hematoma in 1 patient who was subsequently started on anticoagulation. No patients developed recurrent chyle leaks during the follow up period. Conclusion and/or Teaching Points: EVOH copolymer is a safe and effective agent for percutaneous thoracic duct embolization. This is the largest reported series to date demonstrating the efficacy of this embolic agent in treating chylous effusions in the post-traumatic setting.

PP-g-IA의 제조 및 이를 이용한 PP/EVOH 블렌드의 상용화 효과

본 연구에서는 폴리프로필렌 (PP)과 에틸렌 비닐알코올 공중합체 (EVOH)의 블렌드에 있어 발생하는 상분리 현상을 방지하고자 PP에 itaconic acid (IA)가 그라프트 된 PP-g-IA 를 상용화제로 이용하였다. PP-g-IA 상용화제는 PP base에 IA의 투입량을 1, 2, 5, 10 wt.% 로 달리하면서 투입하여 제조하였으며, FT-IR과 <TEX>$^1H$</TEX> NMR 분석을 통하여 성공적으로 PP에 IA가 그래프트 되었음을 확인하였다. 이 중 그래프트율이 1% 로 가장 높게 나타난 PP-g-IA 상용화제를 PP/EVOH 블렌드 연구에 적용하였다. 신규 상용화제가 적용된 PP/EVOH 블렌드는 SEM을 이용하여 모폴로지를 관찰하였고, DSC 와 UTM를 이용하여 열적 기계적 특성을 분석하였다. 분석 결과, PP-g-IA 상용화제는 PP/EVOH 블렌드의 계면접착력을 향상시키는 것으로 나타나 상용화제로써의 유효성이 확인되었다. In this study, we used polypropylene grafted with itaconic acid (PP-g-IA) as a compatibilizer to prevent phase separation phenomenon which occurs upon blending polypropylene (PP) and ethylene-vinyl alcohol copolymer (EVOH). A compatibilizer was prepared using graft copolymerization of itaconic acid (IA) onto PP where input ratio of IA was 1, 2, 5, and 10 wt.%. To confirm the structure of PP-g-IA and the graft ratio of IA onto PP, we used <TEX>$^1H$</TEX> NMR and FT-IR. We tested the compatibilizer which has highest graft ratio of 1% in immiscible PP/EVOH blends. The morphologies of PP/PP-g-IA/EVOH blends were analyzed by SEM. Thermal and mechanical properties of the blends were analyzed by DSC and UTM. PP-g-IA enhanced the interfacial adhesion of PP and EVOH copolymer.

Synthesis and characterization of poly(ethylene-vinyl alcohol)-g-poly(butyl acrylate) copolymers

AbstractEthylene-vinyl alcohol (EVOH) copolymers with different vinyl alcohol (VOH) mole % have been grafted by the carboxyl terminated poly(butyl acrylate) (PBA) prepolymers by the grafting-onto method. The carboxyl terminated PBA were synthesised by solution radical polymerization using 4,4 azobis(cyanovaleric acid) (ACVA) as initiator and thioglycolic acid (TGA) as matched chain transfer agent and then converting carboxyl groups into acid chloride terminated prepolymer by reacting with oxalyl chloride. The acid chloride terminated prepolymers were reacted with EVOH copolymer backbone to synthesize graft copolymers. The graft copolymers were characterized by the Size Exclusion Chromatography (SEC), Fourier Transfer Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Results from these analyses confirmed the grafting of PBA side chain on to EVOH backbone. Differential Scanning Calorimetery (DSC), Dynamic Mechanical Thermal Analysis (DMTA) and x-ray diffraction studies of graft copolymers showed that the morphology of crystalline EVOH polymers has been disrupted due to grafting of amorphous PBA chains.

Glycopolymers resultant from ethylene–vinyl alcohol copolymers: Degradation and rheological behavior in bulk

The physical properties of glycopolymers based on d-(+)-glucosamine, d-(+)-galactosamine and d-(+)-mannosamine derivatives and obtained from two ethylene–vinyl alcohol, EVOH, copolymers with different vinyl alcohol compositions have been analyzed. The thermal degradation of these glycopolymers is almost independent of the type and amount of saccharide incorporated but slightly dependent on the initial EVOH copolymer composition. The glycopolymers derivate from the EVOH copolymer with lower ethylene content present two relaxation processes, while those derivatives from the EVOH copolymer with lower vinyl alcohol composition essentially show three relaxations processes. In both sets of glycopolymers, the relaxation process associated with the cooperative motions that take place at the glass transition is located at analogous temperatures to those previously determined by differential scanning calorimetry, both results being rather consistent.

Deformation and fracture behavior of polypropylene–ethylene vinyl alcohol blends compatibilized with ionomer Zn2+

AbstractThis work investigated the deformation and fracture behavior of polypropylene–ethylene vinyl alcohol (PP/EVOH) blends compatibilized with ionomer Zn2+. Uniaxial tensile tests and quasistatic fracture experiments were performed for neat PP and for 10 and 20 wt % EVOH blends with different ionomer contents. The addition of EVOH copolymer to PP led to an increase in the Young's modulus whereas the yield strength was decreased with the EVOH content as a consequence of the higher stiffness of EVOH and the poor interfacial adhesion between PP and EVOH, respectively. Furthermore, the incorporation of EVOH into PP promoted stable crack growth. Neat PP displayed nonlinear load‐displacement behavior with some amount of slow crack growth preceding unstable brittle fracture, whereas most PP/EVOH blends exhibited “pseudostable” fracture characterized by slow crack growth that could not be externally controlled. All blends exhibited lower resistance to crack initiation than PP but the fracture propagation resistance was significantly improved. For 10 wt % EVOH blends, the resistance to crack initiation was roughly constant with the ionomer content up to 5%, then it increased with the further addition of compatibilizer. Conversely, for 20 wt % EVOH blends, the resistance to crack initiation appeared to be independent of the ionomer content. The better resistance to crack initiation exhibited by the 10 wt % EVOH blends could be attributed to a higher level of compatibilization in these blends. By contrast, 20 wt % EVOH blends with ≤2% ionomer content showed completely stable crack growth. In addition, J–R curves and valid plane strain fracture toughness values for these blends could also be determined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1271–1279, 2005

Poly(ethylene-&lt;I&gt;co&lt;/I&gt;-vinyl alcohol) Functionalized Single-Walled Carbon Nanotubes and Related Nanocomposites

Single-walled carbon nanotubes (SWNTs) were functionalized by poly(ethylene-co-vinyl alcohol) (EVOH) copolymer under carbodiimide-activated esterification reaction conditions. Similar to the parent EVOH copolymer, the EVOH-functionalized carbon nanotubes are soluble in highly polar solvent systems such as DMSO and hot ethanol-water mixtures. The soluble EVOH-SWNT sample was characterized by various techniques, including optical absorption, Raman, NMR, electron microscopy, and thermogravimetric analysis. The common solubility of EVOH and EVOH-SWNT allowed their intimate mixing in solution, and thus the fabrication of nanocomposites in which the SWNTs are homogeneously dispersed in the polymer matrix.

Effects of solvent exposure on the adhesion of grafted PE to EVOH copolymer

Multilayer polymers are gaining popularity in many industrial applications, where the combination of various advantages of the individual materials may be exploited (e.g. mechanical strength and chemical resistance). Such materials rely heavily on the quality of interfacial adhesion and this in turn may alter with solvent exposure. Here, we study the ageing of a multilayer high density polyethylene, grafted polyethylene (PEg), ethylene/vinyl alcohol copolymer (EVOH) assembly in organic solvents, and its effect on the T-peel resistance of the EVOH/PEg interface (interphase). Apolar solvents absorb essentially in the polyethylenic materials leading to reduced peel strength due to modification of polymer bulk properties, rather than to changes in intrinsic adhesion strength. Ethanol diffuses readily into the EVOH leading to an intrinsic drop in energy of adhesion. In the cases studied, reduction of interfacial, peel strength was found to be largely reversible on drying the polymer assembly.

Morphological Alterations Induced by Temperature and Humidity in Ethylene−Vinyl Alcohol Copolymers

The morphologies of a number of high barrier ethylene−vinyl alcohol food packaging films with different ethylene contents have been evaluated by simultaneous WAXS/SAXS, FT-IR, DSC, and Raman spectroscopy. This rather descriptive pioneering study was aimed at the understanding of the morphological changes that occur in these polymers as a result of temperature, humidity, and combination of temperature and humidity treatments. From the results, the temperature effect was, as expected, found to improve polymer crystalline morphology, leading to a higher, denser, and more stable crystallinity. Lower ethylene content copolymers underwent partial solid−solid phase transition toward a more thermodynamically stable monoclinic morphology upon sufficient annealing. On the other hand, moisture sorption was found to result in melting of ill-defined crystals, particularly for the lowest ethylene content copolymers. This water sorption-induced crystal melting process has not been reported before and was seen to be largely suppressed by enhancing crystal stability. Combined temperature and humidity effects, as those for instance generated in retorting autoclaves, were found to dramatically deteriorate the polymer crystallinity, irrespective of initial crystal robustness. By making use of simultaneous time-resolved WAXS/SAXS experiments during in-situ retorting of a water-saturated EVOH copolymer with 32 mol % of ethylene, it was found that heated moisture weakened very readily the polymer crystalline morphology, which melted around 80 °C below its actual melting point.

Synthesis and characterization of new functional polymers by polymer-analog reactions on EVOH copolymer

Polymers carrying different organic functional groups (carboxylic acids, tertiary amines, nitides) wre successfully synthesized from poly[(ethylene)-co-(vinyl alcohol)] (EVOH) in two steps The first step involves acylation of hydroxyl functions of EVOH by phthalic anhydride. Under specific experimental conditions, the substitution may become nearly quantitative. In a second step, alkylation of the so-obtained carboxylic salts in realized in situ using methyliodide, 2-chloroethylpiperidine or chlonoacetonitrile, for examples. Degree of substitution (DS) are easily determined by titration of carboxylic functional groups after, respectively, the first and the second steps. Final functional polymers were characterized by IR spectroscopy and 1 H and 13 C Nuclear Magnetic Resonance. Their thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. Experimental protocols have been established for the transformation of EVOH into polymers bearing new groups such as carboxylic acids, tertiary amines or nitriles through a one pot procedure from EVOH.

Synthesis and characterization of new functional polymers by polymer-analog reactions on EVOH copolymer

Polymers carrying different organic functional groups (carboxylic acids, tertiary amines, nitriles) were successfully synthesized from poly[(ethylene)-co-(vinyl alcohol)] (EVOH) in two steps. The first step involves acylation of hydroxyl functions of EVOH by phthalic anhydride. Under specific experimental conditions, the substitution may become nearly quantitative. In a second step, alkylation of the so-obtained carboxylic salts is realized in situ using methyliodide, 2-chloroethyl piperidine or chloroacetonitrile, for example. Degrees of substitution (DS) are easily determined by titration of carboxylic functional groups after, respectively, the first and the second steps. Final functional polymers were characterized by IR spectroscopy and 1H and 13C Nuclear Magnetic Resonance. Their thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. Experimental protocols have been established for the transformation of EVOH into polymers bearing new groups such as carboxylic acids, tertiary amines or nitriles through a one-pot procedure from EVOH.