• Title/Summary/Keyword: Chemical deterioration

Search Result 473, Processing Time 0.036 seconds

A Study on the Relationship of Change of Mechanical Properties and Carbonyl Index Induced through Short-wavelength Ultraviolet Radiation (254 nm) for High Density Polyethylene (단파장 자외선(254 nm)에 노출된 고밀도 폴리에틸렌 수지의 카르보닐 지수(CI)와 기계적 물성 변화의 관계에 관한 연구)

  • Kim, Chang-Hwan;Shin, Jin-Yong
    • Applied Chemistry for Engineering
    • /
    • v.24 no.2
    • /
    • pp.138-143
    • /
    • 2013
  • This paper studied the possibility to predict a mechanical property variation from changes in created carbonyl bands by irradiating the surface of high-density polyethylene with short-wavelength ultraviolet radiation of 254 nm to induce a fast chemical degradation. The meaning of this study lies in checking whether a mechanical property change with the same chemical property as the induced optical deterioration is caused by using a UVC lamp with high photon energy instead of optical deterioration via xenon arc light source and outdoor exposure test via natural sunlight requiring a long time. The mechanical strength of high-density polyethylene checked by a tensile test and a creep destruction test showed a similar tendency with CI changes. In particular, the yield strength and elongation had a close relationship with the exposure time to ultraviolet radiation. Accordingly, this paper presented a method to grasp the mechanical property change outdoors requiring a long time more fast through the relationship between the mechanical property change and the carbonyl index using a UVC lamp causing the fast surface degradation.

Climate Change Impact on Korean Stone Heritage: Research Trends and Prospect (국내 석조유산의 기후변화 영향: 연구동향과 미래전망)

  • Kim, Jiyoung
    • Journal of Conservation Science
    • /
    • v.32 no.3
    • /
    • pp.437-448
    • /
    • 2016
  • Studies on vulnerability of cultural heritage and adaptation strategy to worldwide climate change have been actively carried out in advanced countries since the late 20th century, and this established a valid research methodology and piled up climate and deterioration dataset in the field of climate change. Meanwhile, we still have tasks to acquire related scientific data despite referencing political researches in Korea. Applying Korean future climate to impact analysis, deterioration of Korean stone heritage is likely prospected to change into complexity in terms of physical, chemical and biological weathering that may bring impacts on conservation business and administrative field of cultural heritage. Further studies will ensure detailed implication of climate change impact on Korean stone heritage by means of down-scaling analysis of areas to local scale and dataset frequency to an hour. It is important to sort out capability and vulnerability of the stone heritage to future environment, and to make an adaption and prevention strategies.

Flavour Chemistry of Chicken Meat: A Review

  • Jayasena, Dinesh D.;Ahn, Dong Uk;Nam, Ki Chang;Jo, Cheorun
    • Asian-Australasian Journal of Animal Sciences
    • /
    • v.26 no.5
    • /
    • pp.732-742
    • /
    • 2013
  • Flavour comprises mainly of taste and aroma and is involved in consumers' meat-buying behavior and preferences. Chicken meat flavour is supposed to be affected by a number of ante- and post-mortem factors, including breed, diet, post-mortem ageing, method of cooking, etc. Additionally, chicken meat is more susceptible to quality deterioration mainly due to lipid oxidation with resulting off-flavours. Therefore, the intent of this paper is to highlight the mechanisms and chemical compounds responsible for chicken meat flavour and off-flavour development to help producers in producing the most flavourful and consistent product possible. Chicken meat flavour is thermally derived and the Maillard reaction, thermal degradation of lipids, and interaction between these 2 reactions are mainly responsible for the generation of flavour and aroma compounds. The reaction of cysteine and sugar can lead to characteristic meat flavour specially for chicken and pork. Volatile compounds including 2-methyl-3-furanthiol, 2-furfurylthiol, methionol, 2,4,5-trimethyl-thiazole, nonanol, 2-trans-nonenal, and other compounds have been identified as important for the flavour of chicken. However 2-methyl-3-furanthiol is considered as the most vital chemical compound for chicken flavour development. In addition, a large number of heterocyclic compounds are formed when higher temperature and low moisture conditions are used during certain cooking methods of chicken meat such as roasting, grilling, frying or pressure cooking compared to boiled chicken meat. Major volatile compounds responsible for fried chicken are 3,5-dimethyl-1,2,4-trithiolanes, 2,4,6-trimethylperhydro-1,3,5-dithiazines, 3,5-diisobutyl-1,2,4-trithiolane, 3-methyl-5-butyl-1,2,4-trithiolane, 3-methyl-5-pentyl-1,2,4-trithiolane, 2,4-decadienal and trans-4,5-epoxy-trans-2-decenal. Alkylpyrazines were reported in the flavours of fried chicken and roasted chicken but not in chicken broth. The main reason for flavour deterioration and formation of undesirable "warmed over flavour" in chicken meat products are supposed to be the lack of ${\alpha}$-tocopherol in chicken meat.

Prevention of Fungal Contamination during Cheese Ripening - Current Situation and Future Prospects (치즈 숙성 중의 곰팡이 오염 방제 - 현황과 전망)

  • Jung, Hoo Kil;Choi, Ha Nuel;Oh, Hyun Hee;Huh, Chang Ki;Yang, Hee Sun;Oh, Jeon Hui;Park, Jong Hyuk;Choi, Hee Young;Kim, Kyoung Hee;Lee, Seung Gu
    • Journal of Dairy Science and Biotechnology
    • /
    • v.30 no.2
    • /
    • pp.75-81
    • /
    • 2012
  • Molds cause severe cheese deterioration, even though some white and blue molds are used for the manufacture of Camembert and Blue cheese, respectively. The species of Geotrichum, Moniliella, Aspergillus, Penicillium, Mucor, Fusarium, Phoma, and Cladosporium are the main fungi that affect contamination during cheese ripening. Once deteriorated by fungal spoilage, cheese becomes toxic and inedible. Fungal deterioration of cheese decreases the nutritional value, flavor profiles, physicochemical and organoleptic properties, and increases toxicity and infectious disease. Fungal contamination during cheese ripening is highly damaging to cheese production in Korean farmstead milk processing companies. Therefore, these companies hesitate to develop natural and ripened cheese varieties. This article discusses the recent and ongoing developments in the removal techniques of fungal contamination during cheese ripening. There are 2 categories of antifungal agents: chemical and natural. Major chemical agents are preservatives (propionic acid, sodium propionate, and calcium propionate) and ethanol. Among the natural agents, grapefruit seed extract, phytoncide, essential oils, and garlic have been investigated as natural antifungal agents. Additionally, some studies have shown that antibiotics such as natamycin and Delvocid$^{(R)}$, have antifungal activities for cheese contaminated with fungi. Microbial resources such as probiotic lactic acid bacteria, Propionibacterium, lactic acid bacteria from Kimchi, and bacteriocin are well known as antifungal agents. In addition, ozonization treatment has been reported to inhibit the growth activity of cheese-contaminating fungi.

  • PDF

Assessment of the potential of algae phycobiliprotein nanoliposome for extending the shelf life of common carp burgers during refrigerated storage

  • Haghdoost, Amir;Golestan, Leila;Hasani, Maryam;Noghabi, Mostafa Shahidi;Shahidi, Seyed Ahmad
    • Fisheries and Aquatic Sciences
    • /
    • v.25 no.5
    • /
    • pp.276-286
    • /
    • 2022
  • This study is focused on the effect of phycobiliprotein extraction of Gracilaria on the quality of common carp burgers, and the application of nanoliposomes containing pigment in the improvement of its antimicrobial and antioxidant activity of burgers during refrigerated storage in 18 days. Burgers were incorporated with phycobiliprotein and liposomal phycobiliprotein (2.5% and 5% w/w), and their chemical and microbial changes in terms of pH, peroxide value (PV), thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N), total viable counts (TVC), psychrotrophic bacterial counts (PTC), and sensory characteristics were evaluated. Results presented a nanoliposome size of about 515.5 nm with capable encapsulation efficiency (83.98%). Our results showed non-encapsulated phycobiliprotein could delay the deterioration of common carp burgers, as a reduction in PV, TBA, and TVB-N, TVC, and PTC values in burgers treated with free and nano encapsulated phycobiliprotein. Moreover, the potential of phycobiliprotein was improved when it was encapsulated into chitosan coated liposomes. Burgers treated with 5% nanoliposomes displayed the lowest amount of lipid oxidation and microbial deterioration in comparison to others during storage. According to chemical, microbial and sensory evaluation, the shelf life of common carp burgers was increased in samples treated with encapsulated phycobiliprotein at 2.5% and 5%, as compared to the control (p ≤ 0.05).

A Study for Degradation Mechanism of Plastic Materials (플라스틱 소재의 탈변색 열화 메커니즘 분석)

  • Youn, Hyung-Joon;Jung, Won-Wook;Byun, Doo-Jin;Choi, Gi-Dae
    • Journal of Applied Reliability
    • /
    • v.7 no.4
    • /
    • pp.173-181
    • /
    • 2007
  • Out door exposure to daylight and weather climate conditions can cause adverse effect on the properties of automotive plastic materials. The effects of sunlight exposure, especially ultra violet (UV) radiation, can break down the chemical bonds in a polymeric material. This degradation process is called photo-degradation and ultimately leads to color changes, cracking, chalking, the loss of physical properties and deterioration of other properties. To explore the effect of sunlight exposure on the automotive materials, this study investigated photo-oxidation degree and surface property change of molding parts by analytical methods. For the further study, accelerated weathering test methods are proposed, which can correlate with out door weathering, to predict long term performance of automotive plastic materials.

  • PDF

Coating Durability of Metal Bipolar plate for Low Temperature PEMFC (저온 PEMFC용 금속분리판 코팅의 내구 특성 연구)

  • Kang, Sungjin;Jeon, Yootaek
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2010.11a
    • /
    • pp.82.2-82.2
    • /
    • 2010
  • The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

  • PDF

Thermodynamical and Experimental Analyses of Chemical Vapor Deposition of ATO from SnCl4-SbCl5-H2O Gas Mixture ($SnCl_4-SbCl_5-H_2O$ 기체혼합물로부터 ATO(Antimony Tin Oxide) 박막의 화학증착에 관한 열역학 및 실험분석)

  • 김광호;강용관;이수원
    • Journal of the Korean Ceramic Society
    • /
    • v.29 no.12
    • /
    • pp.990-996
    • /
    • 1992
  • Chemical vapor deposition of ATO from SnCl4-SbCl5-H2O gas mixture was investigated with thermodynamic and experimental analyses. Electrical conductivity of the ATO film was much improved under deposition conditions of low input-gas ratio, Psbcl5/Psbcl4. This increase of the conductivity was attributed to donor electrons produced mainly by the pentavalent Sb ions in SnO2 lattice. However high input-gas ratio conditions produced an ATO film consisting of a mixture of SnO2 and very fine Sb2O5 phase. It was found that the deterioration of electrical conductivity and optical transmission of the film was caused by the deposition of fine Sb2O5 phase in the SnO2 matrix.

  • PDF

Optimum Machining Condition Determination for Pedicle Screw using Experimental Design Method (실험계획법에 의한 척추경 나사의 최적 절삭조건 결정)

  • Jang, Sung-Min;Cho, Myeong-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.3 no.2
    • /
    • pp.3-9
    • /
    • 2004
  • The main objectives of this paper are to determine optimum cutting conditions using experimental design method to manufacture pedicle screws. Generally, titanium alloys are known as difficult-to cut materials. In the machining of titanium alloy, high cutting temperature and strong chemical affinity between the tool and the work material are generated because of Its low thermal conductivity and chemical reactivity. Such phenomenon cause increase of tool wear and deterioration of surface quality. Thus, in this paper, required experimental investigations are performed to evaluate the machinability of titanium materials With tungsten carbide tools Required simulation and experiments are performed, and the results are investigated.

  • PDF

An Experimental Study on the Effect of Mineral Admixtures for the Durability of Shotcrete (혼화재 종류가 숏크리트 내구성에 미치는 영향에 관한 연구)

  • Paik, Shin-Won;Chung, Dok-Chu
    • Journal of the Korean Society of Safety
    • /
    • v.19 no.2
    • /
    • pp.98-103
    • /
    • 2004
  • Shotcrete needs the enough durability without deterioration for life time. But shotcrete is being deteriorated according to aging like concrete by internal causes whithin itself and by external causes which can be physical, chemical, or mechanical. Durable shotcrete can be made by incresing the cement content, adding chemical and mineral admixtures and so on. So, in this study, chloride ion penetration test, freeze and thaw test, neutralization test were conducted to examine the durability characteristice of shotcrete with mineral admixtures such as silica fume, blast-furnace slag and fly ash. These results indicate that shotcrete with silica fume is durable. Therefore, the present study provides a firm base to make high performance shtcrete.