Shirley Nóbrega Cavalcanti

The growing demand for lightweight, flexible, and efficient materials for electromagnetic interference (EMI) shielding has driven the development of conductive polymer composites (CPCs) as sustainable and reliable alternatives. These materials are essential for protecting communication systems, electronic components, and ensuring the efficient operation of expanding 5G networks. This study presents the development and characterization of PLA/MWCNT and TPU/MWCNT composites, fabricated by melt mixing and compression molding with different loadings of multi‐walled carbon nanotubes (MWCNTs). Rheological analyses indicated that the dispersion of MWCNTs begins at around 3%, with a more pronounced effect in PLA. In particular, PLA/MWCNT composites with 12% filler, where the nanotubes are effectively dispersed, exhibited electrical conductivity on the order of 10 ⁻³ S/cm. On the other hand, although TPU/MWCNT composites also showed an increase in conductivity with the addition of MWCNT, they did not reach the same order of magnitude (10 ⁻³ S/cm), even at 12% filler content. This result may be associated with a less efficient dispersion of MWCNT within the TPU matrix. Electromagnetic shielding effectiveness (EMI SE) increased with MWCNT content, exceeding 60 dB in PLA and reaching up to 50 dB in TPU. Anechoic chamber tests with a 3D‐printed PLA/MWCNT (12%) box confirmed attenuations above 40 dB at 5.9 GHz and between 10 and 15 dB at 3.5 GHz, SEM analyses confirmed the rheological and electrical results, indicating a more homogeneous dispersion of nanotubes in the PLA/MWCNT composites than in the TPU/MWCNT ones. The results highlight PLA/MWCNT as a promising material for EMI shielding in electronics, 5G networks, and aerospace applications.

This work presents the development and characterization of multiresponsive shape memory polymer composites based on thermoplastic polyurethane (TPU), poly( ϵ -caprolactone) (PCL), and Fe ₃ O ₄ particles, targeting applications in 4D printing. The TPU/PCL blend provides mechanical strength, flexibility, and a pronounced shape memory effect, while Fe ₃ O ₄ enables remote activation under near-infrared (NIR) light and microwave radiation. Composites containing 15, 20, 25, and 30 phr of Fe ₃ O ₄ , derived from the TPU/PCL (50/50) blend, were compared to the unloaded blend. The shape memory behavior assessed via dynamic mechanical thermal analysis (DMTA) revealed excellent shape fixity (∼100%) and recovery (∼80%), with a slight decrease in recovery ratio (from 83% to 79%) as Fe ₃ O ₄ content increased. Under NIR and microwave stimuli, recovery efficiency improved with higher Fe ₃ O ₄ loading, reducing total recovery time (60–46 s) and activation time (22–11 s), with saturation above 25 phr. Self-healing properties were also evaluated, showing nearly complete repair in 120 s under NIR and microwave stimulation, while conventional oven heating required longer times (180 s) and was less effective. Additionally, adhesion tests demonstrated that after bonding, the samples retained 50% of their original tensile strength, and failure occurred outside the bonded region, indicating strong interfacial adhesion. Overall, the composites exhibited excellent multistimuli shape memory behaviour, rapid remote actuation, and strong self-healing, highlighting their potential for advanced smart materials and 4D-printed functional structures.

Fruit wastes from the agro‐industry may be used in the preparation of polymer/natural fiber composites. In the current scenario, there is a growing need for sustainable materials that can reduce environmental impact while maintaining or enhancing material properties. One promising approach is the incorporation of natural fibers derived from fruit waste into polymers, which aligns with the global push toward eco‐friendly and circular economy solutions. This work was aimed at the development of filaments of acrylonitrile–butadiene–styrene (ABS)/natural fiber composites for 3D and 4D printing. The fibers used were banana (BAN) peel, orange (ORG) peel, cinnamon (CIN), and neem (NEEM) leaf fibers. The rheological, mechanical, and shape memory properties of the ABS/BAN and ABS/ORG composites were compared with those of the ABS/CIN and ABS/NEEM composites. A slight decrease in viscosity was observed with the addition of the natural fibers to ABS. The ABS/ORG composites showed the highest mechanical properties and good adhesion between the printed layers. The particulate eco‐friendly natural fibers can also be used as pigments, where different types of colors can be obtained. The ABS/natural fiber composites can be processed at the same processing conditions as ABS. The incorporation of natural fibers significantly increased the shape memory result. The use of ABS/natural fiber composites proved to be feasible for preparing the filaments and 3D/4D printing of objects.Highlights: The properties of 3D/4D‐printed ABS/natural fiber composites were investigated. Banana and orange peel, cinnamon, and neem leaf fibers were used. Filaments of ABS/natural fiber composites were successfully obtained. The addition of the fibers to ABS decreased the viscosity and increased shape memory. Among the composites, ABS/orange peel showed the highest mechanical properties.

In this study, the effect of the polymer matrix structure on the rheological and electrical percolation threshold of polymer/carbon black (CB) conductive polymer composites (CPCs) was investigated. Poly(lactic acid) (PLA) and high‐density polyethylene (HDPE) were used as polymer matrices. Through rheological analyses, an increase in complex viscosity was observed with increasing CB concentration, accompanied by a reduction in the Newtonian plateau. Additionally, an increase in the solid‐like behavior was observed, suggesting the formation of a percolated network. The rheological percolation threshold was found to be 5.13% CB mass fraction for the PLA/CB composite and 10.72% for the HDPE/CB composite. Electrical conductivity results were fitted to the sigmoidal Boltzmann model, and its derivative was used to identify the electrical percolation threshold. For PLA/CB, this threshold was reached at 5.39% CB mass fraction, while for HDPE/CB, it occurred at 5.75%. Morphology analysis by scanning electron microscopy and atomic force microscopy indicated that the polymer matrix structure affected the distribution/dispersion of the CB particles within the polymer matrix.Highlights: The effect of polymer matrix structure on polymer/CB CPCs was investigated. The crystallinity of the polymer matrix affected the percolation threshold. PLA/CB showed higher conductivity than HDPE/CB CPCs.

In this work, conductive polymeric composites (CPCs) of renewable source high-density polyethylene (HDPE) (BioPe) with various carbon black (CB) concentrations were developed. To corroborate the electrical conductivity prediction techniques, an artificial neural network (ANN) was modeled and trained to predict electrical conductivity using processing parameters, filler information, and polymeric matrix. Thus, the obtained neural network and the proposed methodology could serve as experimental support for the development of new materials based on parametric variation and consequent prediction of electrical conductivity. Therefore, the use of artificial neural networks from processing data and filler concentration proved to be an efficient technique for predicting the electrical conductivity of CPCs using conductive carbon black as conductive filler.

In this work, polylactic acid (PLA)/copolymer blends were prepared by melt blending. Ethylene‐glycidyl methacrylate (E‐GMA) and ethylene‐butyl acrylate‐maleic anhydride (EBA‐MAH) functional block copolymers were used. A ternary blend of PLA/E‐GMA/EBA‐MAH was also studied. FTIR analyses evidenced the occurrence of reactive compatibilization of E‐GMA and EBA‐MAH with PLA in the binary blends due to the reactivity of the GMA and MAH functional groups with the terminal hydroxyl and carboxyl groups of PLA. Rheological measurements evidenced the occurrence of cross‐link reactions between E‐GMA and EBA‐MAH copolymers in the ternary blend. Three distinct morphologies were observed in the blends: PLA/E‐GMA exhibited a sea‐island structure, PLA/EBA‐MAH exhibited a co‐continuous structure, and PLA/E‐GMA/EBA‐MAH exhibited a semi‐interpenetrating polymer network (SIPN) structure. The shape memory effect (SME) of PLA and PLA/copolymers blends was evaluated by three different methods: fold‐deploy, tension, and torsion. Fold‐deploy tests were conducted in a water bath, whereas the tension and torsion tests were conducted using a rheometer. All methods proved to be effective; however, some precautions must be taken to choose the most suitable test for a given purpose, which is thoroughly discussed in this work. The SME of PLA was enhanced through the incorporation of the copolymers. Blending PLA with E‐GMA, EBA‐MAH, and E‐GMA/EBA‐MAH copolymers increased its shape recovery from 32% to 84%, 79.2%, and 80%, respectively, while its shape fixity remained around 100%.

In this work, conductive polymer composites (CPCs) of bio‐based polyethylene (BioPe) containing different concentrations of carbon black (CB) were developed. By using oscillatory rheology analysis, a Newtonian plateau was observed in BioPe, and all BioPe/CB composites had a behavior of a pseudo‐solid and that composites with volume fractions ranging from 0.24 to 0.56 presented higher viscosity, storage, and loss modulus. This suggests the formation of a percolated network and by using the power‐law models, it was observed that the electrical percolation threshold was higher than the rheological percolation threshold. The electrical conductivity was measured using the four‐point probe method and a sigmoid model was used to predict the CPCs' electrical conductivity percolation threshold. The results indicated that the four‐point probe method presented satisfactory results according to the calculated standard deviations and voltage–current characteristics for each round of measurements considering the same ranging as used in rheology analysis. The analytical model used showed a coefficient of determination (R²) higher than 95%, allowing the prediction of the electrical conductivity of the CPC and the percolation threshold as a function of the volumetric fraction of the CB.

This work aims to evaluate the electrical conductivity and the rheological and mechanical properties of copolymer/carbon black (CB) conductive polymer composites (CPCs). The copolymers, containing ethylene groups in their structure, used as matrix were polyethylene grafted with maleic anhydride (PE g MA), ethylene‐methyl acrylate–glycidyl methacrylate (EMA‐GMA), and ethylene‐vinyl acetate (EVA). For comparison purposes, bio‐based polyethylene (BioPE)/CB composites were also studied. The electrical conductivity results showed that the electrical percolation threshold of BioPE/CB composite was 0.36 volume fraction of CB, whereas the rheological percolation threshold was 0.25 volume fraction of CB. The most conductive CPC was BioPE/CB. Among the copolymer/CB CPCs, PE g MA/CB showed the highest conductivity, which can be attributed to the fact that the PE g MA copolymer had higher crystallinity. It also has a higher amount of ethylene groups in its structure. Torque rheometry analysis indicated that EMA‐GMA copolymer may have reacted with CB. Rheological measurements under oscillatory shear flow indicated the formation of a percolated network in BioPE/CB and copolymer/CB composites. Morphology analysis by scanning electron microscopy (SEM) indicated the formation of a percolated network structure in BioPE/CB composite and finely dispersed CB particles within the PE g MA copolymer. Wetting of CB particles/agglomerates by the copolymer matrix was observed in EVA/CB and EMA‐GMA/CB composites. Conductive CB acted as reinforcing filler as it increased the elastic modulus and tensile strength of BioPE and the copolymers.

This work aimed to evaluate the effect of high‐density polyethylene (HDPE) content and of shear rate on the die swell and flow instability of linear low‐density polyethylene (LLDPE)/HDPE blends. The results showed that the die swell of the LLDPE/HDPE blends increased with the increase in the shear rate. At high shear rates, the increase in the HDPE content led to an increase in the die swell of LLDPE/HDPE blends. The surface morphology analysis of the extrudates by optical and scanning electron microscopy revealed the presence of sharkskin and stick–slip flow instabilities in LLDPE and LLDPE/HDPE blends at the shear rates investigated. These instabilities were attenuated with the addition of HDPE and almost disappeared in the LLDPE/HDPE blend containing 50 wt% of HDPE.

Summary: The aim of this work was to evaluate the effect of clay content and of an impact modifier on the properties of Poly(lactic acid) – PLA/clay biocomposites without and with EG terpolymer. The biocomposites were prepared by extrusion followed by injection molding and characterized by X‐Ray Diffraction (XRD) mechanical properties and Scanning Electron Microscopy (SEM). XRD results indicated a poor dispersion of the clay in the PLA/clay biocomposites regardless of the clay type and content. In the presence of EG terpolymer a better dispersion of the clay was obtained for the PLA/EG/OVT biocomposite. EG terpolymer proved to be a good impact modifier for PLA and the biocomposites, being the PLA/EG/OVT biocomposite the one that presented better impact strength. From the morphology analysis by SEM, plastic deformation on the fracture surface of the PLA/EG/OVT biocomposite was observed.