• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.4
• /
• pp.261-283
• /
• 2023

This study aimed to review the performance stability of PET (Polyethylene terephthalate) fiber reinforcing materials among the synthetic fiber types for which the application of performance reinforcing materials to fiber-reinforced concrete is being reviewed by examining short-term and long-term performance changes. To this end, the residual performance was analyzed after exposing the PET fiber to an acid/alkali environment, and the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture by age were analyzed, and the surface of the PET fiber collected from the concrete specimen was examined using a scanning microscope (SEM). The changes in were analyzed. As a result of the acid/alkali environment exposure test of PET fiber, the strength retention rate was 83.4~96.4% in acidic environment and 42.4~97.9% in alkaline environment. It was confirmed that the strength retention rate of the fiber itself significantly decreased when exposed to high-temperature strong alkali conditions, and the strength retention rate increased in the finished yarn coated with epoxy. In the test results of the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture, no reduction in flexural strength was found, and the equivalent flexural strength result also did not show any degradation in performance as a fiber reinforcement. Even in the SEM analysis results, no surface damage or cross-sectional change of the PET reinforcing fibers was observed. These results mean that no damage or cross-section reduction of PET reinforcing fibers occurs in cement concrete environments even when fiber-reinforced concrete is exposed to high temperatures in the early stage or depending on age, and the strength of PET fibers decreases in cement concrete environments. The impact is judged to be of no concern. As the flexural strength and equivalent flexural strength according to age were also stably expressed, it could be seen that performance degradation due to hydrolysis, which is a concern due to the use of PET fiber reinforcing materials, did not occur, and it was confirmed that stable residual strength retention characteristics were exhibited.

• Science of Emotion and Sensibility
• /
• v.15 no.2
• /
• pp.177-182
• /
• 2012

Automotive sub-mat carpet for convenience and comfort of floor administration is additional supplemented floor mat. Sub Mat Backing of the current vehicle's materials reclaimed rubber, PVC, etc. are used, but secondary rubber and PVC Backing have bad sound absorption. Also rubber is heavy too. Contact surfaces between PET staple fiber, PET non-woven, PVC backing and car's floor carpet was measured the coefficient of friction for each sub-mat's non-slip evaluation. A surface of PET non-woven sub-mat has the highest coefficient of friction. Each of sample was observed by optical microscope the contact surfaces before and after. Contact surfaces of PET staple fiber sub-mat was changed increasingly to non-woven. This fact is shown that the sub-mat would be tangled between its contact surface and top of the floor carpet. It is expected to be highly non-slip. In case of PET non-woven sub-mat had not different for contact surfaces between before and after. And PVC backing was shown lower non-slip than other samples. The result of optical microscope and coefficient of friction is seems to be related.

• Korean Journal of Food Science and Technology
• /
• v.44 no.5
• /
• pp.559-567
• /
• 2012

The storage quality of ready-to-eat Campbell table grapes which were packaged under modified atmospheres was investigated in order to examine the effect of high $O_2$ and $CO_2$ on the fruit. Fresh table grapes with 10-15 berries were packed into polypropylene (PP) trays and were top-sealed with polythylene terephthalate/PP film. The initial gas compositions inside the packages were air, 20% $O_2$/10% $CO_2$/70% $N_2$, and 40% $O_2$/60% $N_2$. Sealed packages with low density polyethylene film bags and perforated PP trays were also used as a further treatment and control, respectively. The quality attributes were assessed during storage at $5^{\circ}C$ for 28 days. Fruit packaged in high $CO_2$ concentration showed the lowest viable cell counts of inherent microorganisms among all samples, although they suffered from severe off-flavors. High levels of $O_2$ significantly lowered flesh weight loss and maintained the flavor of grape. In an overall sensory aspect, the high $O_2$ and $CO_2$ packages exhibited greater scores than the air and control at the end of the storage period. Other quality attributes showed no significant differences among treatments. Results suggest that packaging with an appropriate combination of high $O_2$ and $CO_2$ can be used as an effective processing treatment for improvement of the storability of ready-to-eat table grapes.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.6
• /
• pp.30-39
• /
• 2016

An experimental study was performed to investigate flexural performance and bond characteristics of RC beams strengthened using ductile polyethylene terephthalate(PET) with low elastic modulus. Bond tests were planned and completed following CSA S806. Test variables were fiber type and fiber amount. Also, total of 8 RC beams was tested. Major test variables of the beam tests included section ductility(${\mu}=3.4$, 7.0), fiber type(CF, GF, PET) and amount of fiber strengthening. Moment-curvature analyses of the beam sections were also performed. In bond tests, the bond stress distribution as well as the maximum bond stress increased with increasing amount of PET. In case of 10 layers of PET, the effective bond length was 60 mm with the maximum and the average bond stress of 2.33 and 2.10 MPa, respectively. RC beam test results revealed that the moment capacity of the RC beams strengthened using PET 10 and 20 layers increased over the control beam with little reduction in ductility by fiber strengthening. All beams strengthened using PET resulted in ductile flexural failure without any sign of fiber debonding or fiber rupture. It was important to include the mechanical properties of adhesive in the moment-curvature analysis of PET-strengthened beam sections.

• Korean Journal of Food Science and Technology
• /
• v.47 no.1
• /
• pp.63-69
• /
• 2015

The aim of this study was to investigate the deformation of packaging materials used for ready-to-eat (RTE) foods after the retort process and microwave heating. From the multilayer films consisting of polyethylene terephthalate (PET), polyamide (PA), and cast polypropylene (CPP) in a stand-up pouch form used for RTE foods, some deformation of the CPP layer, which was in direct contact with the food, was observed after the retort process and microwave heating. The damage was more severely caused by microwave heating than by the retort process. This may be attributed to diverse factors including the non-uniform heating in a microwave oven, the sorption of oil into the packaging film, and the different characteristics of food components such as viscosity, salt and water content. The development of heat-resistant packaging materials and systems suitable for microwave heating of RTE foods is required for the safety of consumers.

• Journal of the Korea Concrete Institute
• /
• v.16 no.6 s.84
• /
• pp.767-776
• /
• 2004

Polymer concrete shows excellent mechanical properties and chemical resistance compared with conventional normal cement concrete. The polymer concrete is drawing a strong interest as high-performance materials in the construction industry. Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. Also the recycling of PET in polymer concrete would help solve some of the solid waste problems posed by plastics and save energy. The purposed of this paper is to propose the model for the stress-strain relation of recycled-PET polymer concrete at monotonic uniaxial compression and is to investigate for the stress-strain behavior characteristics of recycled-PET polymer concrete with different variables(strength, resin contents, curing conditions, addition of silane and ages). The maximum stress and strain of recycled-PET polymer concrete was found to increase with an increase in resin content, however, it decreased beyond a particular level of resin content. A ascending and descending branch of stress-strain curve represented more sharply at high temperature curing more than normal temperature curing. Addition of silane increases compressive strength and postpeak ductility. In addition, results show that the proposed model accurately predicts the stress-strain relation of recycled-PET polymer concrete

• Archives of Plastic Surgery
• /
• v.37 no.5
• /
• pp.509-518
• /
• 2010

Purpose: Major drawbacks of conventional bone marrow stromal cells (BSCs) transplantation method are mainly caused by direct transplanted cell to host cell interactions. We hypothesized that separation of the transplanted cells by a microporous membrane might inhibit most of the potential adverse effects and induce superior effect. The purpose of the study is to determine the optimal condition of the microporous membrane. Methods: First, BSCs were placed in polyethylene terephthalate (PET) transwell inserts with 3, 8, or $12{\mu}m$ pore size, and cultured in 24 well culture plates. After 5 days, bottoms of the plates were observed for presence of attached BSCs in monolayer and cell numbers were evaluated. Second, BSCs were placed PET, polycarbonate (PCT), and mixed cellulose esters (MCE) transwell inserts with 3 and $8{\mu}m$ pore size, and cultured in 24 well culture plates. After 3 days, the supernatants of the media left in culture plate were analyzed for collagen, vascular endothelial growth factor (VEGF), platelet derived growth factor BB (PDGF-BB), and basic fibroblast growth factor (bFGF). Third, BSCs were placed in 15% and 70% of the PET membrane with $3{\mu}m$ pore size. All the experimental conditions and methods were same as the second study. Results: The optimal pore sizes to prevent BSC leakage were $3{\mu}m$ and $8{\mu}m$. The amounts of type I collagen and three growth factors tested did not show significant differences among PET, PCT, and MCE groups. However, the collagen, VEGF, and bFGF levels were much higher in the high (70%) density group than in the low (15%) density group. Conclusion: This study revealed that the optimal pore size of membrane to prevent direct BSC to recipient cell contact is in between $3{\mu}m$ and $8{\mu}m$. Membrane materials and pore sizes do not influence the collagen and growth factor passage through the membrane. The most striking factor for collagen and growth factor transport is pore density of the membrane.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.1
• /
• pp.78-84
• /
• 2009

In this paper, ZnO:Al thin film was deposited on polyethylene terephthalate(PET) substrate by capacitively coupled r. f. magnetron sputtering method from a ZnO target mixed with 2wt[%] Al2O3 to investigate the possible application of ZnO:Al film as a transparent conducting electrode for film typed DSCs. The effect of substrate bias on the electrical properties and film structure were studied. The results showed that a positive bias applied to the substrate during sputtering contributed to an improvement of electrical properties of the film by attracting electrons in the plasma to bombard the growing films. These bombardments provided additional energy to the growing ZnO:Al film on the substrate, resulting in significant variations in film structure and electrical properties. Electrical resistivity of the film decreases significantly as the positive bias increases up to +30[V] However, as the positive bias increases over +30[V], the resistivity decreases. The transmittance varies little as the substrate bias is increased from 0 to +60[V], and as r. f. powers increases from 160[W] to 240[W]. The film with electrical resistivity as low as $1.8{\times}10^{-3}[{\Omega}-cm]$ and optical transmittance of about 87.8[%] were obtained for 1,012[nm] thick film deposited with a substrate bias of +30[V].

• Journal of Mushroom
• /
• v.12 no.4
• /
• pp.287-292
• /
• 2014

This study investigated the packaging status and sensory quality of fresh-cut mushroom products from retail markets. Fifty one fresh-cut mushroom products were surveyed / purchased from discount stores in four cities in January (winter), March (spring), August (summer), and October (autumn) 2009. Collected fresh-cut mushrooms include single variety products like whole oyster mushroom and winter mushroom, diced or sliced oak mushroom, sliced king oyster mushroom, and ready-to-cook mixed mushroom products. Most fresh-cut mushrooms were packed in trays made of aluminum, polystyrene (PS), polyethylene terephthalate (PET), nylon materials covered with PVC (polyvinyl chloride) wrap or solid PP (polypropylene) and PS. Eighty nine percent of the covers were labeled with manufacture and expiration date. Collected samples showed severe browning (10%) and off-flavor (4%). The percentage of products with a rating of 'good' or better in overall quality was 90%. Moreover, Survey showed seasonal differences in sensory qualities. All of the collected fresh-cut mushrooms in autumn and winter had high marketability. However, Mushroom products collected in spring and summer had lower quality, hence requires treatment to prevent browning and off-flavor.

• Journal of Food Hygiene and Safety
• /
• v.22 no.4
• /
• pp.279-287
• /
• 2007

Quality attributes of fresh-cut chicory (Clchorium intybus L.var. foliosum) treated with hydrocooling and packing type were investigated in terms of weight loss, respiration, vitamin C content, microbial load and sensory properties during storage at $4^{\circ}C\;and\;10^{\circ}C$. Fresh chicory was trimmed and washed 3 times with cold water $(1^{\circ}C,\;5^{\circ}C)$ and tap water $(10^{\circ}C)$ for 30 sec and then packaged in polypropylene (PP) film bag and polyethylene terephthalate (PETE) tray, and stored for 9 days at $4^{\circ}C\;and\;10^{\circ}C$. Weight loss was decreased by washing and packing generally. Respiration rate was increased slowly in the storage at $4^{\circ}C$. Vitamin C content of chicory packaged within PETE tray were decreased gradually during storage at $4^{\circ}C$. Hydrocooling and packing within PETE tray treatments resulted in approximately 1-2 log CFU/g reduction of microbial load.