Abstract:
This research aims to develop physicochemical properties of low density
polyethylene (PE) by additional titanium dioxide powder (TiO2). The various amounts of
titanium dioxide were investigated to optimize a suitable value for prolonging a ripen
period of mango for transportation of export. The titanium dioxide can effect on the
elimination of ethylene and oxygen existing in PE package. The experiment was
designated to 4 parts i.e. i) film preparation, ii) elimination of oxygen by photocatalytic
reaction of TiO2 modified PE films, iii) elimination of ethylene by photocatalytic reaction
of TiO2 modified PE films and iv) prolonging a ripen period of Num-Dogmai mango. The
three methods of preparation gave the best preparation of TiO2 dip-coating film since
TiO2 contents were comfortably tunable at 0.03 and 0.06 mg/cm2
, while as compounding
and mixing methods gave poor distribution of TiO2 powder approximately at 5.8±1.9 wt%
and 7.4±4.7 wt%, respectively and it was unexpected for modelation according to mixing
limitation of twin screw extruder. The TiO2 modified PE films prepared from
compounding and mixing routes gave higher amount of oxygen absorption in comparison
with pure PE films. The ability of oxygen absorption increased, the more amount of
TiO2 added. No photocatalytic result was clearly found for both films possibly because
of miserable exposure of TiO2 powder and oxygen. The TiO2 dip-coated films apparently
gave photocatalytic results. The photocatalytic activities increased arising from higher
intensity of UV irradiation from 37 to 44 W/cm2
. The ethylene elimination was the
highest at 12.1 ppm/mmol.hr for dip-coated films consisting of TiO2 0.06 mg/cm2
under
UV irradiation at 37 W/cm2
. The ethylene elimination decreased under UV irradiation
> 44 W/cm2
since photocatalytic decompositions of polyethylene films can
coincidently occur at higher UV intensity and gave a trace of propane. The TiO2 dipcoated
package at 0.03 mg/cm2
can prolong the ripen period of Num-Dogmai mango for
2-days lasting longer under UV irradiation at 37 W/cm2
and 24 °C. The mango will be
rotten after 10-days packing.