The effect of MWCNT on dynamic mechanical properties and crystallinity of in situ polymerized polyamide 12 nanocomposite

Effect of Novel Compound Redox Initiators on Polymerization Mechanism and Mechanical Properties of Acrylic Resin

Aiming at the problems of long reaction time and the risk of explosion polymerization of acrylate resin, a small amount of ferrocene (Fc) is added to the existing dibenzoyl peroxide (BPO)/N,N-dimethylaniline (DMA) initiators, and the compound redox initiators (BPO/DMA/ (Fc)) are proposed for acrylate resin polymerization at room temperature. The effect of the content of Fc in the resin on the reaction efficiency and the molding quality of products is researched, and the initiation mechanism of the compound redox initiators is analyzed. It is found that with the addition of Fc, the reaction time of the resin can be shortened by 68% at maximum, the heat release temperature of the resin can be reduced by 40% at maximum, the molecular weight of the reaction products can be increased by 74% at maximum, the tensile and bending properties of the resin castings are increased by 23% and 35% at maximum, respectively, and the bending strength and bending modulus are increased by 57% and 27% at maximum, respectively. The compound redox initiators proposed in this paper can improve the molding efficiency and quality of the product, lay a foundation for the application of acrylic resin in the field of pultrusion molding, perfusion molding, and other in situ molding of thermoplastic composites.

Poly(Butylene Succinate) Hybrid Multi-Walled Carbon Nanotube/Iron Oxide Nanocomposites: Electromagnetic Shielding and Thermal Properties

To address the ever-increasing electromagnetic interference (EMI) pollution, a hybrid filler approach for novel composites was chosen, with a focus on EMI absorbance. Carbon nanofiller loading was limited to 0.6 vol.% in order to create a sustainable and affordable solution. Multiwall carbon nanotubes (MWCNT) and iron oxide (Fe₃O₄) nanoparticles were mixed in nine ratios from 0.1 to 0.6 vol.% and 8.0 to 12.0 vol.%, respectively. With the addition of surfactant, excellent particle dispersion was achieved (examined with SEM micrographs) in a bio-based and biodegradable poly(butylene succinate) (PBS) matrix. Hybrid design synergy was assessed for EMI shielding using dielectric spectroscopy in the microwave region and transmittance in the terahertz range. The shielding effectiveness (20-52 dB) was dominated by very high absorption at 30 GHz, while in the 0.1 to 1.0 THz range, transmittance was reduced by up to 6 orders of magnitude. Frequency-independent AC electrical conductivity (from 10^-2 to 10⁷ Hz) was reached upon adding 0.6 vol.% MWCNT and 10 vol.% Fe₃O₄, with a value of around 3.1 × 10^-2 S/m. Electrical and thermal conductivity were mainly affected by the content of MWCNT filler. The thermal conductivity scaled with the filler content and reached the highest value of 0.309 W/(mK) at 25 °C with the loading of 0.6 vol.% MWCNT and 12 vol.% Fe₃O₄. The surface resistivity showed an incremental decrease with an increase in MWCNT loading and was almost unaffected by an increase in iron oxide loading. Thermal conductivity was almost independent of temperature in the measured range of 25 to 45 °C. The nanocomposites serve as biodegradable alternatives to commodity plastic-based materials and are promising in the field of electromagnetic applications, especially for EMI shielding.

Quantifying Mechanical Abrasion of MWCNT Nanocomposites Used in 3D Printing: Influence of CNT Content on Abrasion Products and Rate of Microplastic Production

Manufactured nanomaterials (MNMs) are incorporated as "nanofillers" into consumer products to enhance properties of interest. Multiwalled carbon nanotubes (MWCNTs) are known for their unique properties and have many applications in polymers. However, the release of MWCNTs during the nanoenabled product life cycle is concerning. During the use phase, mechanical stresses can produce fragmented materials containing MNMs. The degree of MNM release, the resulting exposure to these materials, and the potential impacts of their release are active research topics. In this study, we describe methodological improvements to study the abrasion of plastics containing MNMs (nanocomposites) and report on characteristics of abrasion products produced and rates of microplastic production. The abrasion device developed for this work allows for the measurement of power inputs to determine scaled release rates. Abrasion rates for plastics used in 3D printing were found to be 0.27 g/m²/s for the PETG polymer and 0.3 g/m²/s for the 2% MWCNT-PETG nanocomposite. Embedded and protuberant MWCNTs appeared to impact the particle size, shape, hydrophobicity, and surface charge of the microplastics, while the inclusion of MWCNTs had a small effect on microplastic production. Measurements of power input to the abrasion process provided a basis for estimating microplastic production rates for these nanocomposites.

Different Approaches to Oxygen Functionalization of Multi-Walled Carbon Nanotubes and Their Effect on Mechanical and Thermal Properties of Polyamide 12 Based Composites

In this work the preparation of polyamide 12 (PA12) based composites reinforced with pristine and surface-modified carbon nanotubes is reported. A qualitative and quantitative evaluation of multi-walled carbon nanotube functionalization with oxygen containing reactive groups achieved by different procedures of chemical treatment is presented. Simple strong oxidative acid treatment as well as chlorination with subsequent chloroacetic acid treatment were applied. Carbon nanotubes (CNTs) were also subjected to chlorine and ammonia in gaseous atmosphere with small differences in after-ammonia treatment. Commercial COOH-functionalized carbon nanotubes were compared with nanotubes that were laboratory modified. The effect of CNT functionalization was evaluated basing on the improvement of mechanical and thermal properties of polyamide 12 composites prepared by in situ polymerization. It was found that high concentration of oxygen-containing functional groups on nanotube surface is not sufficient to improve the composite performance if the structure of carbon nanotubes is defective. Indeed, the best effects were achieved for composites containing nanotubes modified under mild conditions, seemingly due to a compromise between morphology and surface chemical structure.