Presentation on theme: "A POLYMERIC CRYSTALLINE PHASE AS ETHYLENE ABSORPTION AGENT Alexandra Romina Albunia, Gaetano Guerra, Tiziana Minucci, Vincenzo Venditto Dipartimento di."— Presentation transcript:
A POLYMERIC CRYSTALLINE PHASE AS ETHYLENE ABSORPTION AGENT Alexandra Romina Albunia, Gaetano Guerra, Tiziana Minucci, Vincenzo Venditto Dipartimento di Chimica, Università di Salerno, Via Ponte don Melillo, Fisciano, 84084 - ITALY VI Convegno Nazionale sulla Scienza e Tecnologia dei Materiali Perugia, Aula Magna dell'Universita' degli Studi 12 - 15 Giugno 2007
It is able to absorb rapidly and selectively molecules already at low concentration. Syndiotactic Polystyrene: termoplastic molecular sieve – CH – CH 2 – CH – CH 2 – T m = 270°C Fast crystallization (X c =30 – 60%) Complex polymorphic behavior (5 crystalline forms) The nanoporous s-PS form presents a permanent cavity of 120-160 Å 3 per 4 monomer units.
S-PS fibrils presenting the nanoporous phase diameters of the fibrils 40-70 nm sPS/toluene 2/98 g/g =0.865 g/ml sPS =0.023 g/ml; P= 98% Solvent removal from s-PS gel by supercritical CO 2 Aerogel Gel Syndiotactic Polystyrene: aerogels Daniel, Alfano, Venditto, Cardea, Reverchon, Mensitieri, Guerra Adv. Mater. 2005, 17, 1515
Syndiotactic Polystyrene: some applications molecular sensors Quartz crystal microbalance (QCM) Mensitieri, Venditto, Guerra Sensors and Actuators B, 2003, 92, 255 Fiber optic sensor Giordano, Cusano, Mensitieri, Guerra Sensors and Actuators B, 2005, 109, 177 air and water purification Venditto, Del Mauro, Mensitieri, Milano, Musto, Rizzo, Guerra Chem. Mater. 2006, 18, 2205 gas storage Annunziata, Albunia, Venditto, Mensitieri, Guerra Macromol. 2006, 39, 9166
The simplest unsaturated hydrocarbon regulates a multitude of plant processes, from seed germination to organ senescence. Of particular economic importance is its role as an inducer of fruit ripening. CH 3 – S – CH 2 – CH 2 –CH – COO – NH 3 + CH 3 – S + – CH 2 – CH 2 –CH – COO – adenine-ribose NH 3 + CH 2 NH 3 + C CH 2 COO – ½ O 2 ACC oxidase HCN + CO 2 H 2 C CH 2 1-amminocyclopropane- 1-carboxylic acid (ACC) L-methionine Ethylene
produceResponse to ethyleneResponse to CO 2 apple ‘Golden Delicious’ Ripening /decay >15% off flavor (fermentation) browning, lesions kiwi >10 ppb softening >7% breakdown of the flesh broccoli 2 ppm reduce shelf-life of 50% >10% sulfur containing volatiles carrot 0.5 ppm bitterness >5% spoilage lettuceRusset spotting >2% brown stain The enemies of fresh produce Ethylene, CO 2 Senescence Water loss Shrivel A water loss of 2% of product weight can become noticeable.
produce Ethylene production ( L/kg h) Respiration rate (CO 2, mL /kg h) apple ‘Golden Delicious’ 20 – 15015 – 30 plum0.1-2008.2 kiwi0.1 – 10015 – 20 broccoli< 0.1140 – 160 carrot> 0.150 – 120 lettuce< 0.125 – 30 Postharvest Technology Research and Information Center Department of Pomology University of California One Shields Ave., Davis, CA 95616-8683 Release of ethylene and CO 2
Ethylene and CO 2 uptake in crystalline polymeric phase Dichroic guest peaks guest included in the crystalline phase Dichroism measurements allow to determine the orientation of the guest molecule in the cavity. With respect to the chain axis, the ethylene molecular plane forms an angle of 41° while the CO 2 long axis forms an angle of 69°. ethylene CO 2
Film samples thickness: 80 m Ethylene uptake and desorption Amorphous phase: D 10 -13 m 2 /sec D 10 -14 m 2 /sec
Diffusivity control by crystalline phase orientation:
Conclusions form s-PS samples show: CO 2 and ethylene absorption in the crystalline phase high weight uptake ( 4 times larger than for commercial films containing 25% of high surface silica) orientation control of diffusivity no water uptake This cheap, robust and easy-to-process polymeric material is suitable for (also repeated use) food packaging requiring ethylene and CO 2 removal.
Freshness preserving agents KMnO4 coated zeolite pellets Ethylene absorbers: Letto catalitico at T close to 250° C. “…facendo passare in circuito chiuso l'atmosfera ricca di CO 2 prelevata dalla cella attraverso un particolare supporto di "carbone attivo". Esso, grazie alla specifica dimensione dei suoi "micropori" ed alla enorme superficie di reazione, possiede la capacità di trattenere selettivamente le molecole di CO 2.” CO 2 absorbers: www.4theegg.comwww.4theegg.com www.isolcell.itwww.isolcell.it
Traditionally used packaging films like LDPE (low density polyethylene) and OPP (oriented polypropylene) are impregnated with additives to become permeable enough for highly respiring products like fresh-cut produces. Common additives: natural clays, ceramics, zeolites, metal oxides, silica, carbon.* Freshness preserving agents Active & intelligent packaging Modified Atmosphere Packaging system (MAP). www.grofitpl.com www.peakfreshusa.com * DiSTAM – Università degli studi di Milano
Activation energy of ethylene diffusion Ethylene desorption from unoriented δ-form s-PS films, at different temperatures in the range -5,+70°C. E a kcal/mol 10
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