• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.611-616
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• 2011

In the study, annealing temperature was optimized by comparing with avrami crystallization rate and constant (k) using non-oriented PLA film as a base film. Crystallization rate constant of PLA film was 1.64, 1.68, and 1.26 at $120^{\circ}C$, $130^{\circ}C$, and $140^{\circ}C$, respectively. Annealing temperature was mainly affected on the surface properties such as rougnness (Ra) and kinetic friction coefficient (${\mu}_k$). Roughness of PLA film was 0.006 ${\mu}m$ at $80^{\circ}C$ and increased to 0.009 ${\mu}m$ 0.015 ${\mu}m$, 0.027 ${\mu}m$, and 0.029 ${\mu}m$ at $110^{\circ}C$, $120^{\circ}C$, $130^{\circ}C$ and $140^{\circ}C$, respectively. Kinetic friction coefficient decreased 0.45 to 0.43, 0.33, 0.31, 0.27 as annealing temperature was at $80^{\circ}C$, $110^{\circ}C$, $120^{\circ}C$, $130^{\circ}C$, and $140^{\circ}C$, respectivly. In addition, rate constant (k) was 0.58, 0.46, and 0.39 with adding 1 wt%, 3 wt%, and 5 wt% talc, respectively.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.251-258
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• 2015

In the study, PLLA with 12,000 g/mol ($M_n$) and 14,000 g/mol ($M_w$) was synthesized from L-lactide, and used to synthesize PLLA-Br intermediate. PLLA-block-PMMA with 84,000 g/mol ($M_n$) and 126,000 g/mol ($M_w$) was finally synthesized from PLLA-Br intermediate. The glass transition temperature ($T_g$) and initial pyrolysis temperature of PLLA-block-PMMA are $95.5^{\circ}C$ and $289^{\circ}C$, respectively. The PLA film of $50{\pm}3{\mu}m$ thickness was prepared by blending PLA with 9 phr PLLA-block-PMMA followed by stretching biaxially at 3 times under $95^{\circ}C$, and annealing at $120^{\circ}C$ for 2 min. The light transmittance at 550 nm and tensile strength of the film are 88.5% and 44.5 MPa, respectively. To enhance the tensile strength of PLA film, it was required to keep the film more than 2 min at $120^{\circ}C$ during the annealing step after a biaxially orientation.

• Journal of Biosystems Engineering
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• v.41 no.2
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• pp.98-107
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• 2016

Purpose: The aim of this study was to find an appropriate polymer film, which could reduce the water condensation for pallet-size modified atmosphere packaging (MAP). Methods: Five different types of films were selected from several commercialized films. Prior to the real food storage test, plastic boxes with wetted plastic balls were used to simulate the high humidity conditions of real food storage. The initial MAP condition was 5% oxygen and 95% nitrogen, and the $O_2$ concentration, the relative humidity and water condensation inside the films were checked on a daily basis. The MAP test for tomatoes was conducted by using the most appropriate film from the five films examined in this study. Results: Every film except Mosspack(R) indicated a similar variation in the $O_2$ concentration over the course of time. The relative humidity near the surfaces of all the films except nylon-6 approached saturation conditions over time. For three kinds of films, namely, low-density polyethylene (LDPE) film, anti-fogging oriented polypropylene (AFOPP) film, and Mosspack(R), the inner surfaces of the films were fully covered with dew after a storage period of a day. Conversely, an area of 4.5% was covered with dew in the case of the poly lactic acid (PLA) film, and there was no dew inside the nylon-6 film. The pallet-size MAP test for tomatoes was conducted by using the nylon-6 film and there was no water condensation inside the nylon-6 film over three weeks of storage. Conclusions: During the pallet scale MAP, water condensation could cause severe fungal infection and wetting of the corrugated box. Hence, it was important to minimize water condensation. This study showed that the MAP films with high WVTR such as nylon-6 and PLA could reduce the water condensation inside the pallet scale MAP.