Conductive polymer composites obtained from recycled poly(carbonate) and rubber blends for heating and sensing applications

Waste to Value-Added Product: Developing Electrically Conductive Nanocomposites Using a Non-Recyclable Plastic Waste Containing Vulcanized Rubber

This study intends to show the potential application of a non-recyclable plastic waste towards the development of electrically conductive nanocomposites. Herein, the conductive nanofiller and binding matrix are carbon nanotubes (CNT) and polystyrene (PS), respectively, and the waste material is a plastic foam consisting of mainly vulcanized nitrile butadiene rubber and polyvinyl chloride (PVC). Two nanocomposite systems, i.e., PS/Waste/CNT and PS/CNT, with different compositions were melt-blended in a mixer and characterized for electrical properties. Higher electrical conduction and improved electromagnetic interference shielding performance in PS/Waste/CNT system indicated better conductive network of CNTs. For instance, at 1.0 wt.% CNT loading, the PS/Waste/CNT nanocomposites with the plastic waste content of 30 and 50 wt.% conducted electricity 3 and 4 orders of magnitude higher than the PS/CNT nanocomposite, respectively. More importantly, incorporation of the plastic waste (50 wt.%) reduced the electrical percolation threshold by 30% in comparison with the PS/CNT nanocomposite. The enhanced network of CNTs in PS/Waste/CNT samples was attributed to double percolation morphology, evidenced by optical images and rheological tests, caused by the excluded volume effect of the plastic waste. Indeed, due to its high content of vulcanized rubber, the plastic waste did not melt during the blending process. As a result, CNTs concentrated in the PS phase, forming a denser interconnected network in PS/Waste/CNT samples.

Preparation and vapor-sensitive properties of hydroxyl-terminated polybutadiene polyurethane conductive polymer nanocomposites based on polyaniline-coated multiwalled carbon nanotubes

Polyaniline-coated multi-walled carbon nanotube (MWCNT) conductive polymer precursors (MWCNTs@PANI) were prepared by an in situ microemulsion oxidation polymerization of aniline in the case of MWCNTs, and then hydroxyl-terminated polybutadiene polyurethane conductive polymer nanocomposites based on MWCNTs@PANI (MWCNTs@PANI/HTPB PUs) were prepared through an in situ stepwise polymerization of HTPB and diisocyanates. The chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR), Raman, x-ray diffraction, x-ray photoelectron spectroscopy and thermogravimetric analysis. The morphologies and dispersion behavior were examined by scanning electron microscopy, transmission electron microscopy and UV-vis transmittance. The MWCNTs@PANI/HTPB PUs nanocomposites were fabricated into film sensors for detection of volatile organic compound vapors, and displayed an evident response to trichloromethane vapor (CHCl₃). The effect of MWCNTs on the conductivity and the responsivity to trichloromethane of conductive polymer nanocomposite films were studied, finding that the conductive composite films have fast and strong response, good repeatability and recoverability, and long-term stability. Consequently, they can be potentially applied for supervision and detection of interior and outdoor environmental gases or vapors.

Sensing skin for strain monitoring made of PC-CNT conductive polymer nanocomposite sprayed layer by layer

Sensing skins about 1.5 μm thick made of 40 nanolayers of conductive polymer nanocomposites (CPC) were sprayed layer by layer (sLbL) directly on a PET woven textile to demonstrate their versatility to monitor the deformation of a flexible, rigid and rough substrate such as a commercial boat sail. CPC sensing skins were developed by structuring a 3D carbon nanotubes network into three kinds of amorphous thermoplastic matrices (PMMA, aPS, PC). Adjustable parameters such as the thickness (number of sprayed layers) and the initial resistance of CPC transducers (CNT content relatively to percolation threshold) enabled to tailor both sensitivity and stability of the piezo-resistive responses, so that it was possible to monitor the strain evolution in the elastic domain and damage accumulation over this limit. Polymer matrices were selected after calculation of their χ Flory-Huggins parameters to evaluate their interactions with the PET substrate and solvent of dispersion, and after the comparison of their stress/strain characteristics, particularly their elastic limit. PC-1%CNT was found to be the best candidate satisfying both chemical and physical criteria. Finally, the exponential evolution of the piezo-resistive response of CPC sensing skins on a wide range of deformation (until breakage at ε = 27%), was well fitted with a model based on quantum tunnelling conduction inducing an exponential evolution of resistance with variations of CNT/CNT junction gap from 0.5 to 0.625 nm.

Thermo- and chemo-electrical behavior of carbon nanotube filled co-continuous conductive polymer nanocomposites (CPC) to develop amperometric sensors

The conductive polymer nanocomposite (CPC) of multiwall carbon nanotubes (MWNT) filled Polycaprolactone (PCL) was formulated by melt mixing method. PCL based conductive phase served as disperse phase, blended with polypropylene (PP) and polyamide 12 (PA12) respectively. The thermo- and chemo-electrical properties of mono- and bi-component CPC have been investigated independently. Results show that PP/PCL-CNT CPC is a good temperature sensor whereas no significant response was observed while exposing to toluene vapor. In contrast, PA12/PCL-CNT exhibits good vapor sensing capability instead of temperature sensor. It is assumed that PP phase prevents the diffusion of vapor molecules within PCL conductive phase. The vapor sensing results indicated that PP external matrix provides the CPC with higher barrier effects than PA12.

Conductive bio-Polymer nano-Composites (CPC): chitosan-carbon nanotube transducers assembled via spray layer-by-layer for volatile organic compound sensing

The chemo-electrical properties of chitosan-carbon nanotubes (Chit-CNT) Conductive bio-Polymer nano-Composites (CPC) transducers processed by spray layer-by-layer (LbL) technique have been investigated. Results show that unlike most synthetic polymer matrices, chitosan provides the transducer with high sensitivity towards not only polar vapours like water and methanol but also to a lesser extent toluene. Quantitative responses are obtained, well fitted with the Langmuir-Henry-Clustering (LHC) model allowing to link electrical signal to vapour content. Chit-CNT transducers selectivity was also correlated with an exponential law to the inverse of Flory-Huggins interaction parameter chi(12). These properties make Chit-CNT a good transducer to be implemented in an e-nose. Additionally, the observation by atomic force microscopy (AFM) of Chit-CNT morphology suggests a chemical nano-switching mechanism promoting tunnelling conduction and originating macroscopic vapour sensing.

Fabrication and characterization of poly(lactic acid)/acetyl tributyl citrate/carbon black as conductive polymer composites

By using acetyl tributyl citrate (ATBC) as the plasticizer of poly(lactic acid) (PLA) and carbon black (CB) as conductive filler, electrically conductive polymer composites (CPC) with different CB and ATBC contents were prepared. FTIR revealed that the interaction existed between PLA/ATBC matrix and CB filler and ATBC could improve this interaction. The rheology showed that ATBC could obviously decrease the shear viscosity and improve the fluidity of the composites but just the reverse for CB. With the increasing of CB contents, the enforcement effect, storage modulus, and glass-transition temperature increased but the elongation at break decreased. PLA/ATBC/CB composites exhibited the low electrical percolation thresholds of 0.516, 1.20, 2.46, and 2.74 vol % CB at 30, 20, 10, and 0 wt % ATBC. The conductivity of the composite containing 3.98 vol % CB and 30 wt % ATBC reached 1.60 S/cm. Scanning electron microscopy revealed that the addition of ATBC facilitated the dispersion of the CB in the PLA matrix. Water vapor permeability (WVP) showed that, at the same CB contents, the more ATBC contents there were, the less the values of WVP were.