Investigation of the piezoresistivity of CNT/PLA nanocomposite with an improved solvent-casting process
Topic(s) : Material science
Co-authors :
Zhenghao ZHANG (UNITED KINGDOM), Vito TAGARIELLI , Qianqian LIAbstract :
Carbon nanotubes (CNTs) have been extensively researched over the past two decades
because their unique tubular structures provide them with excellent mechanical and electrical properties. [1, 2] The addition of CNTs can transfer polymers from insulators to conductive polymer nanocomposites (CPCs) by constructing conductive networks inside the matrix via direct contact between CNTs and the quantum tunnelling effect. [3] The conductive networks can be affected by external stimuli such as chemical vapours [4] and strain fields [5], demonstrating a promising future for CPCs in applications like sensors, smart textiles [6] and more. Poly(lactic acid) or Polylactide (PLA) is one of the most prevalent thermoplastic polymers and was chosen as the matrix of CPC for this project owing to its good mechanical properties, diversity of processing methods and biocompatibility. [7] CNT
distribution status in the matrix has a significant impact on the performance of CPC. While the solution-mixing method can achieve good CNT dispersion at low concentrations [8], it often requires toxic organic solvents during the dissolution process and is time-consuming [9]. Although much work has been done in studying the piezoresistivity of CPNCs, little research has explored their piezoresistive response under complex strain fields. This project aims to find an improved method to fabricate CNT/PLA nanocomposites based on solution-casting and study their piezoresistivity under various loading conditions.
In this project, CNT/PLA nanocomposite plates were manufactured via a solvent-casting and hot-pressing process. Dried PLA pellets (PLA 4043D, NatureWorks) were first dissolved in a low-toxic organic solvent, acetone, at an elevated temperature. Multi-walled CNTs
(MWCNTs, NC7000, NanoCyl®) were mixed with acetone and ultrasonicated for 30
minutes. This mixture was then added to PLA/acetone solution and ultrasonicated again.
Next, the entire mixtures underwent solvent evaporation, casting, vacuum degassing, and hot-pressing processes to become CNT/PLA nanocomposites for further measurements. The tensile strength and elastic modulus of PLA could be improved by 18.3% and 20.7% by
adding only 0.5 wt% MWCNTs. The percolation threshold and critical component of the
nanocomposite were calculated as 0.48wt% and 1.61 according to the traditional percolation
theory. Figure 1 shows that the nanocomposite could achieve a good electrical conductivity
of 0.32 S/m at 1wt% concentration. Other characterisations such as DSC, TGA, SEM and
more were also conducted. The piezoresistive responses of nanocomposites under different
strain fields were measured and analysed (one example is presented in Figure 2). The
MWCNTs dispersion and the composites' microstructure were also studied to check the
microstructure-property-dispersion relationship.
because their unique tubular structures provide them with excellent mechanical and electrical properties. [1, 2] The addition of CNTs can transfer polymers from insulators to conductive polymer nanocomposites (CPCs) by constructing conductive networks inside the matrix via direct contact between CNTs and the quantum tunnelling effect. [3] The conductive networks can be affected by external stimuli such as chemical vapours [4] and strain fields [5], demonstrating a promising future for CPCs in applications like sensors, smart textiles [6] and more. Poly(lactic acid) or Polylactide (PLA) is one of the most prevalent thermoplastic polymers and was chosen as the matrix of CPC for this project owing to its good mechanical properties, diversity of processing methods and biocompatibility. [7] CNT
distribution status in the matrix has a significant impact on the performance of CPC. While the solution-mixing method can achieve good CNT dispersion at low concentrations [8], it often requires toxic organic solvents during the dissolution process and is time-consuming [9]. Although much work has been done in studying the piezoresistivity of CPNCs, little research has explored their piezoresistive response under complex strain fields. This project aims to find an improved method to fabricate CNT/PLA nanocomposites based on solution-casting and study their piezoresistivity under various loading conditions.
In this project, CNT/PLA nanocomposite plates were manufactured via a solvent-casting and hot-pressing process. Dried PLA pellets (PLA 4043D, NatureWorks) were first dissolved in a low-toxic organic solvent, acetone, at an elevated temperature. Multi-walled CNTs
(MWCNTs, NC7000, NanoCyl®) were mixed with acetone and ultrasonicated for 30
minutes. This mixture was then added to PLA/acetone solution and ultrasonicated again.
Next, the entire mixtures underwent solvent evaporation, casting, vacuum degassing, and hot-pressing processes to become CNT/PLA nanocomposites for further measurements. The tensile strength and elastic modulus of PLA could be improved by 18.3% and 20.7% by
adding only 0.5 wt% MWCNTs. The percolation threshold and critical component of the
nanocomposite were calculated as 0.48wt% and 1.61 according to the traditional percolation
theory. Figure 1 shows that the nanocomposite could achieve a good electrical conductivity
of 0.32 S/m at 1wt% concentration. Other characterisations such as DSC, TGA, SEM and
more were also conducted. The piezoresistive responses of nanocomposites under different
strain fields were measured and analysed (one example is presented in Figure 2). The
MWCNTs dispersion and the composites' microstructure were also studied to check the
microstructure-property-dispersion relationship.