Characterization of the UV Oxidation of Raw Natural Rubber Thin Film Using Image and FT-IR Analysis

( Ik Sik Kim ),( Bok Won Lee ),( Kyung Suk Sohn ),( Joohoe Yoon ),( Jung Hun Lee ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.1

Characterization of the UV oxidation for raw natural rubber (NR) was investigated in controlled conditions through image and FT-IR analysis. The UV oxidation was performed on a thin film of natural rubber coated on a KBr window at 254 nm and room temperature to exclude the thermal oxidation. Before or after exposure to UV light, image of the NR thin film was observed at a right or tilted angle. FT-IR absorption spectra were measured in transmission mode with the UV irradiation time. The UV oxidation of NR was examined by the changes of absorption peaks at 3425, 1717, 1084, 1477, 1377, and 833 cm(-1) which were assigned to hydroxyl group (-OH), carbonyl group (-C=O), carbon-oxygen bond (-C-O), methylene group (-CH2-), methyl group (-CH3), and cis-methine group (cis-CCH3=CH-), respectively. During the initial exposure period, the results indicated that the appearance of carbonyl group was directly related to the reduction of cis-methine group containing carbon-carbon double bond (-C=C-). Most of aldehydes or ketones from carbon-carbon double bonds were formed very fast by chain scission. A lot of long wide cracks with one orientation at regular intervals which resulted in consecutive chain scission were observed by image analysis. During all exposure periods, on the other hand, it was considered that the continuous increment of hydroxyl and carbonyl group was closely related to the decrement of methylene and methyl group in the allylic position. Therefore, two possible mechanisms for the UV oxidation of NR were suggested.

회분식 미분반응기를 이용한 PE계 플라스틱의 열분해특성 연구

김상훈(Kim, Sang-Hoon),장현태(Jang, Hyun-Tae),차왕석(Cha, Wang-Seog) 한국산학기술학회 2007 한국산학기술학회논문지 Vol.8 No.3

HDPE와 LDPE에 대한 열분해실험을 반응기 크기가 40 ㎤인 스테인레스 스틸 반응기에서 수행하였으며 이때 반응온도는 410-460℃이었다. 열분해생성물인 액상생성물과 기상생성물을 분리하여 채취하였고 각 생성물의 분자량분포는 HPLC-GPC와 GC분석을 통해 얻었다. 미분반응기에서 열분해온도와 시간이 증가할수록 액상생성물의 수율과 분자량 분포는 전체적으로 감소하는 경향을 보였다. 열분해반응에서 말단절단의 속도계수인 활성화에너지 값은 HDPE, 63.0㎉/mole, LDPE, 45.7㎉/mole 이었다. Pyrolysis experiments of HDPE and LDPE were carried out in the stainless steel reactor of internal volume of 40 ㎤, Pyrolysis reactions were performed at temperature 410~460℃ and the pyrolysis products were collected separately as liquid and gas products. The molecular weight distributions(MWDs) and composition of each product were determined by HPLC-GPC and GC analysis. It was represented that the yield and the molecular weight of liquid product were decreased with the increase of reaction temperature and time. The chain-end scission rate parameters, respectively, were determined to be 63.0㎉/mole of HDPE, 45.7㎉/mole of LDPE by the Arrhenius plot.

Degradation behavior of poly (l-lactide-co-glycolide) films through gamma-ray irradiation

Jo, S.Y.,Park, J.S.,Gwon, H.J.,Shin, Y.M.,Khil, M.S.,Nho, Y.C.,Lim, Y.M. Pergamon 2012 Radiation physics and chemistry Vol.81 No.7

Gamma-ray irradiation is a very useful tool to improve the physicochemical properties of various biodegradable polymers without the use of a heating and crosslinking agent. The purpose of this study was to investigate the degradation behavior of poly (l-lactide-co-glycolide) (PLGA) depending on the applied gamma-ray irradiation doses. PLGA films prepared through a solvent casting method were irradiated with gamma radiation at various irradiation doses. The irradiation was performed using 60Co gamma-ray doses of 25-500kGy at a dose rate of 10kGy/h. The degradation of irradiated films was observed through the main chain scission. Exposure to gamma radiation dropped the average molecular weight (M<SUB>n</SUB> and M<SUB>w</SUB>), and weakened the mechanical strength. Thermograms of irradiated film show various changes of thermal properties in accordance with gamma-ray irradiation doses. Gamma-ray irradiation changes the morphology of the surface, and improves the wettability. In conclusion, gamma-ray irradiation will be a useful tool to control the rate of hydrolytic degradation of these PLGA films.

Prediction of the Number- and Weight-Average Degree of Polymerization of Polymers Subjected to Random Chain Scission Degradation

Jin San Yoon(윤진산) 한국고분자학회 2016 폴리머 Vol.40 No.1

분자 사슬의 무작위 절단 매카니즘으로 분해되는 고분자의 수평균(μn) 및 중량평균 중합도(μw)를 예측할 수 있는 새로운 이론식을 유도하였다. 이전의 이론식들은 고분자의 분해 과정에서 생성되는 단량체를 포함하는 저분자량 물질이 제거되지 않고 고분자 시료 내에 모두 잔존한다고 가정한 상태에서 유도되었으나, 본 이론식은 중합도가(m-1) 보다 낮은 단량체 및 올리고머가 고분자 시료로부터 모두 제거되는 것을 고려하여 유도되었다. 이전의 이론식들은 1/μn이 분해 시간에 따라 직선적으로 증가하며 분자량 분포 지수 (Q=μw/μn)가 2로 수렴한다고 예측하였으나 본 이론식에 의하면, m 값이 커짐에 따라 1/μn과 시간 사이의 관계가 직선으로부터 현저히 벗어나며 Q의 점근값이 2 보다 크게 낮아지는 것으로 예측되었다. New theoretical model equations were derived to predict the number- (μn) and weight-average degree of polymerization (μw) of polymers subjected to random chain scission degradation. Unlike previous theoretical equations, which were set up assuming that low molecular weight products, even including monomeric substances remain unremoved in the polymer residue throughout degradation, the new model considered the concomitant removal of oligomers with a degree of polymerization ≤ m-1. The previous models (corresponding to m=1) predicted that 1/μn increases linearly with increasing degradation time and that the polydispersity (Q=μw/μn) approaches asymptotically to 2. In contrast, as the value of m increases, the deviation from the linear relationship between 1/μn and time becomes increasingly significant, and the asymptotic value of Q becomes much less than 2.

Characterization on the Ozone Oxidation of Raw Natural Rubber Thin Film using Image and FT-IR Analysis

( Ik-sik Kim ),( Dooyoul Lee ),( Kyung-suk Sohn ),( Jung-hun Lee ),( Joongwoo Bae ) 한국고무학회 2019 엘라스토머 및 콤포지트 Vol.54 No.2

The characterization of the ozone oxidation for raw natural rubber (NR) was investigated under controlled conditions through image and fourier transform infrared (FT-IR) analysis. The ozone oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 40oC under low humidity conditions to completely exclude thermal, moisture, or light oxidation. The ozone concentration was set at 40 parts per hundred million (pphm). Before or after exposure to ozone, the image of the thin film for raw NR was observed at a right or tilted angle. FT-IR absorption spectra were measured in the transmission mode according to ozone exposure time. The ozone oxidation of NR was determined by the changes in the absorption peaks at 1736, 1715, 1697, and 833 cm^-1, which were assigned to an aldehyde group (-CHO), a ketone group (-COR), an inter-hydrogen bond between carbonyl group (-C=O) from an aldehyde or a ketone and an amide group (-CONH-) of protein, and a cis-methine group (cis-CCH₃=CH-), respectively. During ozone exposure period, the results indicated that the formation of the carbonyl group of aldehyde or ketone was directly related to the decrement of the double bond of cis-1,4-polyisoprene. Only carbonyl compounds such as aldehydes or ketones seemed to be formed through chain scission by ozone. Long thin cracks with one orientation at regular intervals, which resulted in consecutive chain scission, were observed by image analysis. Therefore, one possible two-step mechanism for the formation of aldehyde and ketone was suggested.

Study of UV aging on the performance characteristics of vegetable oil and palm oil derived isocyanate based polyurethane

Sonalee Das,Priyanka Pandey,Smita Mohanty,Sanjay Kumar Nayak 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.2

The impact of UV aging on the characteristic properties of synthesized polyurethane (PUs) from castor oil and transesterified castor oil with palm oil based isocyanate and 1,4 butanediol was investigated at different exposure time of 0, 250, 500, 750 and 1,000 h, respectively. The aging properties of the PU films were analyzed through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Tensile tests. The PU films derived from castor oil showed noticeable changes in chemical structure after 250 h of UV exposure owing to chain scission of the urethane group. A considerable decrease in the thermal and tensile properties of the developed PU films was observed due to the plasticization phenomenon. SEM micrographs revealed morphological changes through the appearance of cracks and blisters composed of primary amines on the surface of exposed PU films. However, PUs derived from transesterified castor oil with a higher hydroxyl value exhibited improved UV resistance characteristics due to higher crosslinking and degrade only after 750 h of exposure. Thus, the synthesized green PUs based on transesterified castor oil with palm oil based isocyanate compositions can be candidate materials for developing UV resistant coating material.

Characterization on the Thermal Oxidation of Raw Natural Rubber Thin Film using Image and FT-IR Analysis

Kim, Ik-Sik,Cho, Hwanjeong,Sohn, Kyung-Suk,Choi, Hwa-Soon,Kim, Sung-Uk,Kim, Sinkon The Rubber Society of Korea 2020 ELASTOMERS AND COMPOSITES Vol.55 No.1

In this study, the thermal oxidation of raw natural rubber (NR) was investigated under controlled conditions by optical image and fourier transform infrared (FT-IR) analysis. The thermal oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 80℃ under low humidity conditions to completely exclude moisture and restrict light oxidation. Images of the thin film of raw NR were obtained before and after thermal oxidation. FT-IR absorption spectra were measured in the transmission mode at different thermal exposure times. The thermal oxidation of NR was examined by the changes in the absorption peaks at 3449, 1736, 1447, 1377, 1242, 1072, and 833 cm^-1, which corresponded to a hydroxyl group (-OH), a carbonyl group (-C=O) from an aldehyde and a ketone, a methylene group (-CH₂-), a methyl group (-CH₃), a carbon-oxygen single bond (-C-O) from an epoxide, a carbon-oxygen bond (-C-O) from an ether, an alcohol, a peroxide, or a cyclic peroxide, and a cis-methine group (cis-CCH₃=CH-), respectively. In the initial stage of thermal oxidation, two different types of free radicals were produced quickly and randomly by the homolytic cleavage of a double bond and allylic hydrogen abstraction. Aldehydes and ketones were formed from chain scissions of the double bonds and alcohols were produced from allylic hydrogen abstraction at the methylene or methyl groups. Two reactions seemed to proceed competitively with each other. At a later stage, oxidative crosslinks seemed to dominate through the combination of free radicals such as an allyl radical (CH=CHCH₂·), alkoxy radical (RO·), and peroxy radical (ROO·) and the reaction of a hydroperoxide (-ROOH) with a double bond. The image obtained after thermal oxidation showed hardening without cracks. Based on these observations, a plausible two-step mechanism was suggested for chain hardening caused by the thermal oxidation.

Characterization on the Thermal Oxidation of Raw Natural Rubber Thin Film using Image and FT-IR Analysis

( Ik-sik Kim ),( Hwanjeong Cho ),( Kyung-suk Sohn ),( Hwa-soon Choi ),( Sung-uk Kim ),( Sinkon Kim ) 한국고무학회 2020 엘라스토머 및 콤포지트 Vol.55 No.1

In this study, the thermal oxidation of raw natural rubber (NR) was investigated under controlled conditions by optical image and fourier transform infrared (FT-IR) analysis. The thermal oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 80℃ under low humidity conditions to completely exclude moisture and restrict light oxidation. Images of the thin film of raw NR were obtained before and after thermal oxidation. FT-IR absorption spectra were measured in the transmission mode at different thermal exposure times. The thermal oxi­dation of NR was examined by the changes in the absorption peaks at 3449, 1736, 1447, 1377, 1242, 1072, and 833 cm^-1, which corresponded to a hydroxyl group (-OH), a carbonyl group (-C=O) from an aldehyde and a ketone, a methylene group (-CH₂-), a methyl group (-CH₃), a carbon-oxygen single bond (-C-O) from an epoxide, a carbon-oxygen bond (-C-O) from an ether, an alcohol, a peroxide, or a cyclic peroxide, and a cis-methine group (cis-CCH₃=CH-), respectively. In the initial stage of thermal oxidation, two different types of free radicals were produced quickly and randomly by the homolytic cleav­age of a double bond and allylic hydrogen abstraction. Aldehydes and ketones were formed from chain scissions of the dou­ble bonds and alcohols were produced from allylic hydrogen abstraction at the methylene or methyl groups. Two reactions seemed to proceed competitively with each other. At a later stage, oxidative crosslinks seemed to dominate through the com­bination of free radicals such as an allyl radical (CH=CHCH₂·), alkoxy radical (RO·), and peroxy radical (ROO·) and the reaction of a hydroperoxide (-ROOH) with a double bond. The image obtained after thermal oxidation showed hardening without cracks. Based on these observations, a plausible two-step mechanism was suggested for chain hardening caused by the thermal oxidation.

고선량의 감마선과 전자선이 조사된 cotton linter 종이의 물리적 특성 변화 비교

황유진,정명준,박해준 한국펄프·종이공학회 2022 펄프.종이기술 Vol.54 No.6

The effects of gamma ray and electron beam irradiation on paper disinfection were eval- uated. The paper was irradiated with 10-100 kGy gamma rays and electron beams which were higher than the recommended dose for paper disinfection. After irradiation, the mechanical properties and color of the paper and the cellulose chain scission rate were evaluated. In the case of paper strength, it decreased after 25 kGy irradiation, whereas the discoloration of paper appeared after 10 kGy irradiation. It cannot confirm the effect on paper only with changes in mechanical strength and color in the recommended range of 0.5-10 kGy for actual paper disinfection treatment. On the other hand, even with 10 kGy irradiation, the degree of polymerization of cellulose paper was reduced by ~50%. Cotton linter paper with a degree of polymerization of about 2,000 was predicted to decrease by about 7% after being irradiated with a 1 kGy gamma ray and electron beam. To evaluate the irradiation effect on paper, it is therefore more reasonable to evaluate the degree of polymerization rather than the strength and color of the paper. .

Nuclear Magnetic Resonance Study of O-ring Polymer Exposed to High-Pressure Hydrogen

Chang Hoon Lee,Jae-Kap Jung,Sang Koo Jeon,Kwon Sang Ryu,Un Bong Baek 한국자기학회 2017 Journal of Magnetics Vol.22 No.3

Magic angle spinning (MAS) nuclear magnetic resonance (NMR) for <SUP>19</SUP>F and 1H nuclei was used how exposure to high-pressure (70 MPa) H₂ gas affected an O-ring material. <SUP>19</SUP>F MAS NMR revealed that poly(vinylidenefluoride-co-hexafluoroprophylene) in VDF/HFP = 76.1/23.9 mol % (FKM type 1) was involved in the O-ring material. This copolymer may undergo main-chain scission and termination to -CF₂H end groups during depressurization of high-pressure H₂. Evidence for formation of additional -CF₂H end group includes a small increase in the <SUP>19</SUP>F MAS NMR signal at -96 ppm, and a corresponding ¹H MAS NMR signal at 7.1 ppm in comparison with those in the material that had not been exposed to high-pressure H₂. Neither the <SUP>19</SUP>F nor the ¹H MAS NMR showed chemical shift after exposure to H₂; this absence of response means that exposure to H₂ did not affect the structure of the polymer.