• Journal of the Korean Wood Science and Technology
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• 제34권2호
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• pp.37-45
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• 2006

The viscoelastic properties of blends of melamine-formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) for engineered flooring used on the Korean traditional ONDOL house floor heating system were investigated by dynamic mechanical thermal analysis (DMTA). Because MF resin is a thermosetting adhesive, the effect of MF rein was shown across all thermal behaviors. The addition of PVAc reduced the curing temperature. The DMTA thermogram of MF resin showed that the storage modulus (E') increased as the temperature was further increased as a result of the cross-linking induced by the curing reaction of the resin. The storage modulus (E') of MF resin increased both as a function of increasing temperature and with increasing heating rate. From isothermal DMTA results, peak $T_{tan{\delta}}$ values, maximum value of loss modulus (E") and the rigidities (${\Delta}E$) of MF/PVAc blends at room temperature as a function of open time, peak $T_{tan{\delta}}$ and maximum loss modulus (E") values were found to increase with blend MF content. Moreover, the rigidities of the 70:30 and 50:50 MF/PVAc blends were higher than those of the other blends, especially of 100% PVAc or MF. We concluded that blends the MF/PVAc blend ratios correlate during the adhesion process.

• Macromolecular Research
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• 제17권10호
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• pp.785-790
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• 2009

In this paper, the relaxation behavior of the regenerated silk fibroin (SF) films was investigated using dielectric thermal analysis (DETA), and compared with the dynamic mechanical behavior obtained from dynamic mechanical thermal analysis (DMTA), in order to gain a better understanding of the characteristics of dielectric behavior of SF film and identify the differences between the two analyses. Compared to DMTA, DETA exhibited a higher sensitivity on the molecular relaxation behaviors at low temperature ranges that showed a high $\gamma$-relaxation peak intensity without noise. However, it was not effective to examine the relaxation behaviors at high temperatures such as $\alpha-$ and ${\alpha}_c$-relaxations that showed a shoulder peak shape. On the contrary, DMTA provided more information regarding the relaxation behaviors at high temperatures, by exhibiting the changes in width, intensity and temperature shift of the $\alpha$-relaxation peak according to various crystallinities. Conclusively, DETA and DMTA can be utilized in a complementary manner to study the relaxation behavior of SF over a wide temperature range, due to the different sensitivity of each technique at different temperatures.

• 분석과학
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• 제5권3호
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• pp.309-317
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• 1992

졸-겔법에 의해 무기-유기 복합체를 합성하였으며, 복합체의 결합특성을 알아보기 위하여 DMTA(Dynamic Mechanical Thermal Analyzer)를 이용하여 유리전이 온돈(Tg)를 측정하였다. HCl 과 물의 양이 증가될수록 Tg는 고운으로 진행됨으로부터 복합화가 더 잘 일어남을 알 수 있었다. 그러나 반응시간에 따른 Tg의 변화는 관찰되지 않았다.

• Journal of the Korean Wood Science and Technology
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• 제33권4호통권132호
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• pp.15-22
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• 2005

현악기용 도료가 현악기의 음향성능에 미치는 영향을 조사하기 위해 음향분석장치(FFT)와 점탄성 분석장치(DMTA, dynamic mechanic thermal analyzer)를 이용하여 목재악기용 도료의 음향적 성능을 평가하였다. 목재악기용으로 사용된 도료는 악기용 우레탄계 상도도료, 오일 스테인계 도료, 천연바니쉬, 캐슈 도료 및 자외선 경화형 에폭시 도료를 사용하였다. 형성된 도막의 음향적인 특성은 FFT 분석기에서 측정된 공명주파수와 댐핑값(damping factor)과 DMTA에서 측정된 tan ${\delta}$를 통하여 유추하였다. FFT에서 측정된 공명주파수와 댐핑값으로부터 도막이 가지는 음향특성에 대해 분석하였다. 측정된 도막의 점탄성적인 특성과 음향적 특성을 검토한 결과 악기용으로서의 적정도료를 결정하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.128-130
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• 2003

As toughness-investigation to improve brittleness of existing epoxy resin, elastic-factor of elastic epoxy using TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis) and FESEM (Field Emission Scanning Electron Microsope) for structure-images analysis were investigated. A range of measurement temperature of the TMA, DMTA was changed from -20[$^{\circ}C$] to 200[$^{\circ}C$]. When modifier was ratio of 0[phr], 20[phr], 35[phr], glass transition temperature (Tg) of elastic epoxy was measured through thermal analysis devices. Also, it was investigated thermal expansion coefficient ($\alpha$), modulus and loss factor through DMTA. In addition, it was analyzed structure through FSSEM and made sure elastic-factor of elastic epoxy visually. As thermal analysis results, 20[phr] was superior than 30[phr] thermally and mechanically. Specially, thermal expansion coefficient, modulus, damping properties were excellent. By structure-images analysis through FESEM, we found elastic-factor of elastic epoxy that is not existing epoxy, and proved high impact.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권4호
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• pp.192-199
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• 2004

Elastic-factor of elastic epoxy were investigated by TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis), TGA (Thermogravimetric Analysis) and FESEM (Field Emission Scanning Electron Microscope) for structure-images analysis as toughness-investigation to improve brittleness of existing epoxy resin. A range of measurement temperature of the TMA and DMTA was changed from -20($^{\circ}C$) to $200^{\circ}(C)$, and TGA was changed from $0^{\circ}(C)$ to $600^{\circ}(C)$. Glass transition temperature (Tg) of elastic epoxy was measured through thermal analysis devices with the content of 0(phr), 20(phr) and 35(phr). Also, thermal expansion coefficient (a), high temperature, modulus and loss factor were investigated through TMA, TGA, and DMTA. In addition, the structure of specimens was analyzed through FESEM, and then elastic-factor of elastic epoxy was visually showed by FESEM. As thermal analysis results, 20(phr) was more excellent than 30(phr) thermally and mechanically. Specially, thermal expansion coefficient, high temperature, modulus, and damping properties were excellent. By structure-images analysis through FESEM, we found elastic-factor of elastic epoxy that is not existing epoxy, and proved high impact.

• 폴리머
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• 제24권3호
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• pp.358-365
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• 2000

Miscibility itnd thermal behavior of blends of synthetic biodegradable aliphatic polyester (Bionolle) with poly(epichlorohydrin) (PECH) were investigated by a differential scanning calorimetry (DSC), a dynamic mechanical thermal analyzer (DMTA) and a rotational rheometer. Observed both single glass transition temperatures from the DSC in agreement with the Fox equation and single T$_{g}$ changes as a function of composition from the DMTA indicate that these blend mixtures are miscible. In addition, the miscibility of this blend system was also observed from the single curve of the Cole-Cole Plot of log G′($\omega$) vs. log C"($\omega$) from the dynamic test using a rotational rheometer. This was further verified from the cryogenically fractured surface of BDP/PECH blends by scanning electron microscopy.

• 한국가스학회지
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• 제2권4호
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• pp.18-24
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• 1998

작용기가 2.9인 4,4'-diphenylmethane diisocyanate (MDI)와 polyester polyol 그리고 사슬 연장제로서 1,4-butane diol로부터 제조한 polyurethane을 시차 주사 열분석기(DSC) 동적 기계적 열분석기(DMTA), 그리고 퓨리에 변환 적외선 분광기(FT-IR)를 이용하여 물성을 연구하였다. 본 연구에서 제조한 polyurethane은 MDI의 높은 작용기로 인한 가교 때문에 균일한 망상구조를 가지고 있음을 알 수 있었다. 또한 하드 세그먼트 함량이 증가할수록 $T_g$는 증가함을 관찰할 수 있었다. 이러한 DSC 결과는 DMTA에서도 재확인할 수 있었다. 한편 polyurethane의 열처리 효과(annealing effect)를 관찰하기 위해 다양한 열처리 조건에 따라 polyurethane의 열분석을 하였다. 그 결과 열처리 온도가 증가될수록 폴리우레탄의 $T_g$가 증가됨을 관찰할 수 있었다. 반면에 열처리 시간에는 크게 의존하지 않음을 관찰할 수 있었다. 이러한 $T_g$의 증가는 팽윤(swelling) 실험으로부터 열처리에 따라 가교 밀도가 증가하며 이러한 가교 밀도의 증가가 polyurethane의 $T_g$를 상승시키는 원인임을 확인 할 수 있었다. 반면에 FT-IR 연구로부터 열처리에 의한 polyurethane의 수소결합 정도의 변화는 관찰할 수 없었다.

• 대한화학회지
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• 제38권7호
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• pp.480-484
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• 1994

자외선 경화코팅 필름-기질 계면에서의 견딤성에 대하여 조사하였다. 특히, UV 경화 우레탄 아크릴레이트계 배합물에서 모노머 및 올리고머의 코팅필름 주름현상에 미치는 영향은 조사하였다. 실험결과, 주름현상은 DMTA이 손실모듈러스 피크가 넓고 shouldr가 있을수록 덜 나타났다. 특히, 변성된 방향족 우레탄 아크릴레이트를 지방족계에 첨가하므로서 hard하면서도 flexible한 코팅필름을 얻을 수 있음을 알 수 있었다. 따라서 주름현상 방지효과는 높은 손실모듈러스값 때문인 것으로 나타났다. SEM 및 instron 실험결과도 위의 결론을 입증하고 있음을 알 수 있었다.

• Smart Structures and Systems
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• 제24권3호
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• pp.361-377
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• 2019

The stiffness of shape memory alloy (SMA) spring while in actuation is represented by an empirical model that is derived from the logistic differential equation. This model correlates the stiffness to the alloy temperature and the functionality of SMA spring as active variable stiffness actuator (VSA) is analyzed based on factors that are the input conditions (activation current, duty cycle and excitation frequency) and operating conditions (pre-stress and mechanical connection). The model parameters are estimated by adopting the nonlinear least square method, henceforth, the model is validated experimentally. The average correlation factor of 0.95 between the model response and experimental results validates the proposed model. In furtherance, the justification is augmented from the comparison with existing stiffness models (logistic curve model and polynomial model). The important distinction from several observations regarding the comparison of the model prediction with the experimental states that it is more superior, flexible and adaptable than the existing. The nature of stiffness variation in the SMA spring is assessed also from the Dynamic Mechanical Thermal Analysis (DMTA), which as well proves the proposal. This model advances the ability to use SMA integrated mechanism for enhanced variable stiffness actuation. The investigation proves that the stiffness of SMA spring may be altered under controlled conditions.