Dependence of mechanical performances of polymer/carbon nanotubes nanocomposites on percolation threshold

Nikfar, Nafiseh,Zare, Yasser,Rhee, Kyong Yop Elsevier 2018 PHYSICA B-CONDENSED MATTER - Vol.533 No.-

<P><B>Abstract</B></P> <P>In this study, several models for the tensile modulus and strength of polymer/carbon nanotubes (CNT) nanocomposites (PCNT) are expressed as a function of percolation threshold. The roles of the CNT aspect ratio α and percolation threshold <SUB> φ p </SUB> in the mechanical properties of PCNT are plotted according to the original and developed models. Furthermore, the effects of <SUB> φ p </SUB> and various interfacial/interphase parameters on the PCNT tensile strength are presented through contour plots. The tensile modulus and strength of PCNT show a threshold at low <SUB> φ p </SUB> values, indicating the important effect of the percolation behavior on the mechanical properties. Poor mechanical performances are seen at high <SUB> φ p </SUB> values and different ranges of interfacial/interphase parameters. However, the lowest <SUB> φ p </SUB> values and the highest ranges of interfacial/interphase parameters result in the most desirable PCNT strength.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The percolation threshold in polymer/CNT nanocomposites is correlated to CNT aspect ratio. </LI> <LI> The models for mechanical properties are expressed as a function of percolation threshold. </LI> <LI> The effects of percolation and interfacial/interphase parameters are investigated. </LI> <LI> The mechanical properties of PCNT show a threshold at low levels of percolation fraction. </LI> <LI> The important roles of CNT network and interfacial/interphase properties are presented. </LI> </UL> </P>

A new methodology based on micromechanics model to predict the tensile modulus and network formation in polymer/CNT nanocomposites

Wang, Entong,Tehrani, Mehran Soltani,Zare, Yasser,Rhee, Kyong Yop Elsevier 2018 Colloids and surfaces. A, Physicochemical and engi Vol.550 No.-

<P><B>Abstract</B></P> <P>This work suggests a new methodology based on a micromechanics model to predict the tensile modulus and network formation in polymer/CNT nanocomposites above percolation threshold of nanoparticles. A network parameter (NP) depending on the percolation threshold and network properties is introduced. The predictions of the model are evaluated by experimental data of samples from literature. The influences of effective parameters on the modulus and NP are estimated using 3D and contour plots. The predictions of the suggested model agree with experimental results above percolation threshold. The model also overpredicts the modulus in the samples not containing a nanoparticle network. The suggested model presents the logical correlations of modulus to effective parameters such as CNT volume fraction, percolation threshold, CNT aspect ratio and CNT modulus. In addition, NP directly and inversely depends on CNT aspect ratio and percolation threshold, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study suggests a model for tensile modulus and network formation in nanocomposites. </LI> <LI> A network parameter (NP) depending on the network properties is introduced. </LI> <LI> The predictions acceptably agree with the experimental results above percolation threshold. </LI> <LI> The model overpredicts the modulus in the samples not including the filler network. </LI> <LI> The “NP” directly handles the tensile modulus of nanocomposites. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

카본블랙 충진 Polyethylene Matrix Composites의 유전 특성

신순기,Shin, Soon-Gi 한국재료학회 2011 한국재료학회지 Vol.21 No.4

It is known that the relative dielectric constant of insulating polyethylene matrix composites with conducting materials (such as carbon black and metal powder) increases as the conducting material content increases below the percolation threshold. Below the percolation threshold, dielectric properties show an ohmic behavior and their value is almost the same as that of the matrix. The change is very small, but its origin is not clear. In this paper, the dielectric properties of carbon black-filled polyethylene matrix composites are studied based on the effect medium approximation theory. Although there is a significant amount of literature on the calculation based on the theory of changing the parameters, an overall discussion taking into account the theory is required in order to explain the dielectric properties of the composites. Changes of dielectric properties and the temperature dependence of dielectric properties of the composites made of carbon particle and polyethylene below the percolation threshold for the volume fraction of carbon black have been discussed based on the theory. Above the percolation threshold, the composites are satisfied with the universal law of conductivity, whereas below the percolation threshold, they give the critical exponent of s = 1 for dielectric constant. The rate at which the percentages of both the dielectric constant and the dielectric loss factor for temperature increases with more volume fraction below the percolation threshold.

The Electrical Property of Polymer Matrix Composites Added Carbon Powder

Shin, Soon-Gi Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.12

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

New way to characterize the percolation threshold of polyethylene and carbon nanotube polymer composites using Fourier transform (FT) rheology

Ahirwal, Deepak,Palza, Humberto,Schlatter, Guy,Wilhelm, Manfred 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.3

In this article, a new way to characterize the percolation threshold of polymer nanocomposites made of polyethylene (PE) with single and multi walled carbon nanotubes (SWCNTs and MWCNTs) is presented. Small and large oscillatory shear (SAOS and LAOS) experiments were performed to characterize the degree of dispersion and percolation threshold. The analysis of the stress response in the LAOS regime as a function of the applied deformation amplitude and frequency was performed using Fourier Transform (FT)-Rheology. The zero strain intrinsic nonlinear parameter, $Q_0({\omega})$, was calculated by extrapolation of $I_{3/1}({\gamma}_0,{\omega})$ and was, used to quantify the nonlinearity measured by FT-Rheology. Interestingly, a drop in $Q_0$ as a function of the CNT weight fraction at a fixed frequency was found that was below the percolation threshold. This was followed by, a steep rise in $Q_0$ above the percolation threshold. Therefore, the new method based on this observation that is proposed and described with this article has the potential to lead to a better understanding of structure-property relationships in polymer nanocomposites.

New way to characterize the percolation threshold of polyethylene and carbon nanotube polymer composites using Fourier transform (FT) rheology

Deepak Ahirwal,Humberto Palza,Guy Schlatter,Manfred Wilhelm 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.3

In this article, a new way to characterize the percolation threshold of polymer nanocomposites made ofpolyethylene (PE) with single and multi walled carbon nanotubes (SWCNTs and MWCNTs) is presented. Small and large oscillatory shear (SAOS and LAOS) experiments were performed to characterize the degreeof dispersion and percolation threshold. The analysis of the stress response in the LAOS regime as a functionof the applied deformation amplitude and frequency was performed using Fourier Transform (FT)-Rheology. The zero strain intrinsic nonlinear parameter, Q0(ω), was calculated by extrapolation of I3/1(γ0, ω) andwas, used to quantify the nonlinearity measured by FT-Rheology. Interestingly, a drop in Q0 as a functionof the CNT weight fraction at a fixed frequency was found that was below the percolation threshold. Thiswas followed by, a steep rise in Q0 above the percolation threshold. Therefore, the new method based onthis observation that is proposed and described with this article has the potential to lead to a better understandingof structure-property relationships in polymer nanocomposites.

전도성 니켈분말-에폭시수지 복합체의 전기적 특성

오대희,임덕점,이정은,박영희,오승민 한국유화학회 2014 한국응용과학기술학회지 Vol.31 No.2

The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the epoxy resins filled with nickel. The sample was prepared using vehicle such as epoxy resin replenished with nickel powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 4.666~13.074 when using nickel powder. Weight loss of the conductive composites took place at 350℃~470℃.

논문 : 카본블랙 충진 PMC의 Percolation Threshold와 도전율 임계지수에 관한 연구

신순기 ( Soon Gi Shin ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.9

In this paper, the percolation behavior, the critical exponent of conductivity, and the electrical conduction mechanism of polyethylene matrix composites are discussed based on studying the whole change of the resistivity and dielectric constant for carbon black loading. There are two transitions of resistivity for carbon black loading. Below the first transition, resistivity shows an ohmic behavior, and its value is almost the same as that of polyethylene. Between the first and second transitions, the change in resistivity is very sharp, leading to a large critical exponent of conductivity, and a non-ohmic electric field dependence of current has been observed. This electric field dependence has been discussed with a tunneling conduction. Beyond the second transition, the electric field dependence of current shows an ohmic behavior and a gentle change in resistivity has been observed for carbon black loading. The critical exponent of conductivity estimated by using the second transition is satisfied with the universal law of conductivity. The dielectric constant has been observed beyond the first transition and diverges around the second transition. It was concluded that the percolation threshold should be the second transition of resistivity for the polyethylene matrix composites loaded carbon black.

전도성 아연/에폭시 수지 복합체의 전기적 특성

박재경(Jae Kyung Park),이정은(Jung Eun Lee),최태운(Tae Un Choi),홍기헌(Ki Heon Hong),오승민(Seung Min Oh),오대희(Dae Hee Oh) 한국고분자학회 2015 폴리머 Vol.39 No.6

에폭시 수지에 아연 분말을 분산시켜 전도성 복합재료를 제조하여 충전제의 함량별 체적 전기저항과 미세경도, 미세구조, 열적 성질 등을 조사하였다. 아연/에폭시 수지 복합체의 체적 전기저항은 8.8×10⁶~4.4×10³Ω·㎝의 범위를 나타내었다. 아연함량이 70 wt%인 lower 관투전이 영역에서 upper 관투전이 영역인 78 wt%까지 체적 전기저항 값이 급격하게 감소하였다. 이는 분말 함량 70 wt% 이상에서부터 전자가 잘 이동할 수 있는 통로가 만들어진 것으로 보인다. 분말 함량이 78 wt% 이상에서는 매트릭스 내의 분말 함량만 늘어날 뿐 체적저항의 감소에는 영향을 주지 않는 것으로 나타났다. 아연/에폭시 수지 복합체의 초미세 경도(DHT) 값은 4.566~6.604로 나타났다. 이것은 매트릭스 내 분말의 함량이 증가할수록 복합체의 DHT 값은 증가하는 것으로 나타났다. 이는 고분자 매트릭스 내에 분말간의 보강효과에 의해 경도가 증가한 것으로 보인다. 전기전도도는 니켈/에폭시 수지 복합체보다 아연/에폭시 수지 복합체가 높았다. 복합체의 경도는 보고된 니켈/에폭시 수지 복합체와 아연/에폭시 수지 복합체는 비슷한 경도를 가진 것으로 나타났다. 아연/에폭시 수지 복합체의 열적 안정성은 400~470 ℃ 사이에서 매트릭스로 사용되어진 에폭시 수지의 분해로 무게 손실이 발생된 것으로 니켈과 아연 복합체 모두 비슷한 온도에서 열분해가 시작되는 것으로 보아서 아연금속 분말의 영향보다 에폭시 매트릭스의 영향을 많이 받는 것으로 사료되어진다. The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the resins filled with zinc. The sample was prepared using vehicle such as epoxy resin replenished with zinc powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 8.8×10⁶~4.4×10³ Ω·㎝ when using zinc powder. Weight loss of the conductive composites took place at 400~470 ℃.

Prediction of tensile modulus in polymer nanocomposites containing carbon nanotubes (CNT) above percolation threshold by modification of conventional model

Yasser Zare,이경엽 한국물리학회 2017 Current Applied Physics Vol.17 No.6

In this paper, a simple model is developed to predict the tensile modulus of polymer/carbon nanotubes (CNT) nanocomposites (PCNT) above percolation threshold. Since the conventional models such as Ouali and Lyngaae-Jorgensen (L-J) cannot predict the accurate results, a developed model is presented which calculates proper modulus as a function of aspect ratio (a) and volume fraction of CNT at percolation threshold ðfpÞ. The developed model can present accurate data, which agree with the experimental results at all filler concentrations. The high ranges of “a” and low values of “fp” achieve a desirable modulus. However, a high “fp” causes the poor modulus at different “a” demonstrating that the role of “a” is highlighted at slight “fp”. It is also possible to calculate the “a” and “fp” parameters by applying the developed model to the experimental data of modulus.