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Bao b phn hy sinh hc (Phn 1: Tng quan)

Th Su, 22/07/2011, 12:18 CH | Lt xem: 580

Mc d c nhng khuyn co v vn nn nhim do bao b nha mng li v c cc

loi bao b giy thay th, nhng con ngi khng th ph nhn s tin li ca bao b nhav tip tc s dng bt chp li cnh bo "Mt thi gian n chng ta s i li trn ccng rc bao b".

Cc loi bao b bng nha nh PE, PP, PVC, PS gi chung l polyolefin. Vic s dngcc loi nha c bit l nha olefin tng ng k trong nhng thp nin gn y v chi phthp tnh cht c l tt. nhng vn mi trng cng l thch thc khi y mnh s dngloi nha ny bi v cc loi nha olefin khng d dng phn hy trong mi trng tnhin qu trnh phn hy c th tnh bng n v th k. Polyolefin phn hy c to ranhm p ng hai yu cu: hng ha phc v i sng v khi phn hy nha n snphm cui cng phi khng c hi vi mi trng.

Vn mi trng lin quan n vic qu l thuc vo bao b polyolefin khin cngng cc nc trn th gii lo ngi, Hin nay vn x l cc loi rc thi bng nha chyu l t, trn v ti ch. Tuy nhin 3 phng php ny iu mang n ri ro cao nh khit polyolefin s sinh ra lng bi v CO2 ln, trn s gy cho t bc mu, ti ch nhiuln th cc loi bao b s khng cn tnh c l tt nh ban u.

Hin nay cc nh khoa hc tm v quan tm ch to cc loi bao b polyolefin phn hysinh hc (gim cp sinh hc - Oxo-biodegradation) .

Nha phn hy sinh hc hay Oxo-biodegradation c m t qua hai giai on phn hy.

+ Giai on u l phn ng ca oxi trong ko khi vi polymer, cc mch polymer b ctnh (to thnh olygomer) l kt qu ca qu trnh oxi ha, giai on ny khng c mt cacc vi sinh vt lm nhim v oxihoa(abiotic oxidation), vic s dng oxi s bin cc mchpolymer hnh thnh cc nhm chc nh l cacbonyl, acid cacboxilic, ester, anhdehid,ru. T mt polymer k nc xut hin cc nhm chc a nc to iu kin cho vicphn hy cc polymer d dng hn.

+ Giai on hai l phn hy sinh hc bi s oxi ha ca cc vi sinh vt nh vi khun,nm chng s phn hy cc mch olygomer cn li thnh CO2 v nc.

Trong giai on u l giai on quan trng nht v n quyt nh ton b qu trnh, tronggiai on u ca qu trnh phn huy sinh hc s gim cp c th din ra nhanh hn khi cmt ca tia UV (photodegradation) hoc nhit (Thermal degradation).

Giai on u hay cn gi l giai on gim cp quang ha (Photodegradation) lin quann cc khuynh hng t nhin cho hu ht cc loi polymer chng phi tri qua mt qutrnh phn ng t t vi oxi khng kh vi s tr gip ca anh sng, thng thng cc tcnhn nhy sng c s dng lm nhanh hn so vi xu hng t nhin(mt vi thp

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nin). C ch ca gim cp quang ha lin quan n s hp thu nh sng UV v sau tora cc gc t do. Mt qu trnh oxi ha t ng din ra s phn hy tn cng cc loipolymer. Ngi ta tin tng rng lun lun khi c s hin din ca cc nhm cacbonylhoc hidroperoxide trong qu trnh ch to hoc gia cng s lm cho polyolefin khng bn,da t im ny c th iu khin qu trnh phn hy.

Hnh trn minh ha c ch v mt s sn phm hnh thnh khi phn hy quang ha PE.Nhm hydroperoxide group (CHOOH) l sn phm u tin ca qu trnh oxi ha vu khng bn di tc dng ca nhit hoc nh sng. V sau n s cho cc loi sn

phm polymer c cha cc nhm a nc c th tan trong nc, cc nhm ny lm chopolyolefin d phn hy hn.

Cc nhm ceton c th c ng ly theo hai c ch Norrish I hoc Norrish II.

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Ngoi ra cn c qu trnh gim cp nhit (Thermal degradation), c ch gim cp nhittng t nh gim cp quang ha, tuy nhin vn tc ca gim cp nhit ph thuc trc tipvo nhit .

NGUYN CAO THCH

I HC KHOA HC T NHIN

SEMINAR polymer phn hy sinh hc

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