• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• 한국융합학회논문지
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• 제12권6호
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• pp.33-38
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• 2021

경량의 의료방사선 차폐시트를 제작하기 위해 새로운 차폐소재를 검토하였다. 가정에서 음식물 쓰레기로 버려지는 계란 껍데기 분말을 고분자 물질과 혼합하여 차폐재료의 가능성을 검증하고자 하였다. 기존의 경량 소재는 친환경의 조건을 만족하지만 주 재료 정제과정의 비용으로 인해 차폐시트 제작의 경제성에 어려움이 있다. 본 연구는 가정용 폐기물인 계란 껍데기를 이용하여 이러한 문제점을 해결하고자 한다. 고분자 물질인 HDPE를 이용하여 3 mm 두께의 차폐시트를 제작하였으며, 차폐시트 단면 내의 입자 분포상태도 분석하였다. 입자의 모양은 대체로 거칠게 구성되어 입자 간 공극이 있었으며, 단위 면적당 무게는 평균 1.5 g/cm² 로 나타났다. 차폐성능은 저에너지 영역에서는 20%대, 고에너지 영역에서는 10%대의 차폐성능을 보여 저선량 의료방사선 차폐시트의 재료로 가능성을 보여주었다.

• Advances in nano research
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• 제15권4호
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• pp.315-328
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• 2023

The main goal of the present study was to assess the effects of eggshell powder (ESP) and halloysite nanotubes (HNTs) on the mechanical properties of abaca fiber (AF)-reinforced natural composites. For this purpose, a limited number of indentation tests were first performed on the AF/polypropylene (PP) composites for different HNT and ESP loadings (0 wt.% ~ 6 wt.%), load amplitudes (150, 200, and 250 N), and two types of indenters (Vickers or conical). The Young's modulus, hardness and plasticity index of each specimen were calculated using the indentation test results and Oliver-Pharr method. The accuracy of the experimental results was confirmed by comparing the values of the Young's modulus obtained from the indentation test with the results of the conventional tensile test. Then, a feed-forward shallow artificial neural network (ANN) with high efficiency was trained based on the obtained experimental data. The trained ANN could properly predict the variations of the mentioned mechanical properties of AF/PP composites incorporated with different HNT and ESP loadings. Furthermore, the trained ANN demonstrated that HNTs increase the elastic modulus and hardness of the composite, while the incorporation of ESP reduces these properties. For instance, the Young's modulus of composites incorporated with 3 wt.% of ESP decreased by 30.7% compared with the pure composite, while increasing the weight fraction of ESP up to 6% decreased the Young's modulus by 34.8%. Moreover, the trained ANN indicated that HNTs have a more significant effect on reducing the plasticity index than ESP.

• 한국식품영양과학회지
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• 제38권9호
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• pp.1195-1201
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• 2009

양송이분말을 혼합한 사료로 사육한 산란계(Hy-Line brown) 계란의 품질특성을 조사하였다. 실험군은 대조군(Control), 양송이분말 0.3% 혼합식이군(M-0.3) 및 양송이 분말 0.6% 혼합식이군(M-0.6)으로 구분하여 군당 100마리씩으로 12주간 사육하였다. 그 결과 난각의 두께는 유의차가없었다. 난중과 농후난백의 높이로 산출한 Haugh unit는 양송이분말 식이군이 대조군에 비해 18.3$\sim$27.6%가 높았다. M-0.3 및 M-0.6군은 대조군에 비하여 난백과 난황의 $L^*$값과 $b^*$값은 낮은 반면 $a^*$값은 높았으며 난황의 총인지질 함량은 4.5$\sim$13.9%가 높았다. 또한 실험식이군에서는 대조군에 비하여 난황의 총콜레스테롤 함량은 29.4$\sim$31.9%가, 중성지질 함량은 51.9$\sim$52.4%가, LDL-cholesterol 함량은 49.1$\sim$53.5%가 각각 낮았으나 HDL-cholesterol 함량은 86.1$\sim$87.0%가 높았다. 각 실험군 간의 지방산조성은 뚜렷한 차이가 없었으며, 관능검사 결과 양송이분말 급여군의 계란은 비린내가 적었다. 이상의 실험결과, 양송이분말은 난황의 콜레스테롤 함량을 낮추는 반면 인지질의 함량을 높임과 동시에 계란의 비린내를 감소시키는 효과가 있어 기능성 사료로서의 활용이 기대된다.