Thermoplastic Materials Research Articles

Analysis of the mechanical properties of the single layered braid reinforced thermoplastic pipe (BRTP) for oil & gas industries

Reinforced thermoplastic pipes (RTPs) are instantly being broadly scrutinized as a feasible surrogate for metallic pipes due to their superior corrosion resistance, low weight, and low maintenance worth, they have three primary layers inner, outer, and reinforcement. Process parameters for manufacturing reinforced layers are critically essential to enhancing the mechanical performance of RTPs. However, limited comparative research on the impact of braiding parameters on RTP’s mechanical characteristics appears to be publicly available. Therefore, this study examines how these variables affect the mechanical characteristics of braid RTP. This new class of braid RTP is constructed of an HDPE liner pipe, over-wrapped with a single braid layer of resin glass fiber. L9 Taguchi orthogonal array design for experiments was used to create specimens. Furthermore, specimens were subjected to tensile and compression to assess their mechanical properties. Epoxy and ±75 were the most promising parameters in achieving the highest number of tensile and compression properties among choices of thermoplastic polymer matrices and braid angles, respectively. ANOVA suggested that both parameters are significant and significantly impact the mechanical properties of the prototype braid RTP. Also, A1B3 is considered the best combination for producing braid RTP with higher mechanical performance; no notable interaction among factors was found.

Damage evolution model and failure mechanism of continuous carbon fiber-reinforced thermoplastic resin matrix composite materials

As a new composite material with high strength, toughness, and heat resistance, the continuous fiber-reinforced polyaryl ether sulfone ketone (PPESK) thermoplastic resin matrix composite (CFRP) has a wide temperature range, which is attributed to the complex temperature sensitivity of the matrix. The failure evolution characteristics under different conditions are not clear yet, which significantly limits its development and application to high-precision equipment. In this work, in order to deeply explore the full three-dimensional (3D) multi-scale multi-physics damage evolution mechanism of the CFRP over a wide temperature range, macroscale cross-temperature stretching/bending experiments, computer tomography (CT) scanning, and microscale scanning electron microscopy (SEM) are performed to effectively capture the overall damage morphology and local fiber/matrix damage failure characteristics of the material. The results show that the reinforcement with continuous fibers increases the tensile strength of the CFRP by 14–45 times and its bending strength by 2–6 times compared to those of the PPESK matrix in the cross-temperature domain. Moreover, the main failure mechanism of the CFRP in the cross-temperature domain is matrix crushing and fiber fracture at room temperature and fiber fretting slip and matrix viscous flow at high temperatures. This further explains the deformation mechanism of the CFRP, which can maintain its stability at high temperatures (low elongation at break: 1%–1.2%). The unique trans-temperature regional energy evolution and continuous fiber reinforcement of the material matrix resin PPESK lay the synergic stability of the high temperature performance and damage morphology of the CFRP. In particular, a cell model is constructed to further reveal the damage evolution characteristics of the matrix, fiber, and interface of the CFRP at the micro-scale. Combined with the failure mode theory and the performance degradation mechanism of composite materials, the temperature influence factor is introduced to formulate a multi-scale full 3D temperature-dependent damage evolution constitutive model of the CFRP over a wide temperature range. The constitutive model of the CFRP is incorporated in finite element software, and the simulation results are compared with the experimental ones for validation. The results show that the model developed in this work can effectively characterize the complex mechanical damage morphology and progressive failure characteristics of the CFRP over a wide temperature range.

Temperature-dependent cutting physics in orthogonal cutting of carbon fibre reinforced thermoplastic (CFRTP) composite

The global commitment towards reducing carbon emissions drives the implementation of sustainable carbon-fibre-reinforced-thermoplastic composites (CFRTPs). However, the machining of CFRTPs presents challenges due to the material’s ductile–brittle composition and sensitivity to machining-induced high temperatures. For the first time, we conducted temperature-controlled orthogonal cutting of CFRTP (using CF/PEKK as a demonstrator) to unveil its temperature-dependent cutting physics. Three representative cutting temperatures, 23 ℃ (ambient temperature),100 ℃ (<PEKK’s glass transition temperature (Tg)) and 200 ℃ (>Tg) and four typical fibre cutting orientations (0°, 45°, 90°, and 135°) have been investigated. The evolution of chip microstructural morphology and surface/subsurface damage have been analysed by advanced microscopy to reveal temperature-dependent material removal mechanisms. The experimental results were elucidated through a novel microscale finite-element-analysis (FEA) model considering thermal softening of the matrix and interface. Results show the transition of the cutting physics with increasing temperature is associated to the degradation of the thermoplastic matrix stiffness/ultimate strength and interface bonding strength and fracture toughness, especially when > Tg.

Desiccant Dehumidification System Developed Using Additive Manufacturing and Biodegradable Materials

Traditional dehumidification equipment is based on vapour compression units. However, they depend mainly on electrical energy and use polluting gases. An alternative to this equipment is desiccant dehumidification systems, which is based on adsorbent materials. These desiccant systems are an efficient way of removing moisture from the air in buildings with high latent loads. This work presents a new way to manufacture fixed-bed desiccant elements that can remove moisture from an air flow. The desiccant element is obtained by material extrusion-based additive manufacturing (fused filament fabrication or FFF). This technology is cost-effective and provides a precision and finish suitable for the intended use. The filament used is Pine, consisting of an easy printable thermoplastic matrix (polylactic acid, PLA, 80 wt%) and a filler based on pine wood powder (20 wt%). This composite material reached a water absorption capacity of 11.5 %. The experimental results of the desiccant air unit demonstrated high dehumidification capacity, up to 39 mg/s, for a regeneration air temperature of 50 °C. The volumetric adsorption rate was also high, up to 30 g/s·m3, for low pressure drop values, below 522 Pa. The proposed method allows the customised, on-demand and just-in-time manufacturing of air dehumidification systems based on the use of biodegradable desiccant materials of organic origin. Such solutions contribute to the circular economy promoted by The United Nations in the Sustainable Development Goals.

Tribological Behaviour and Surface Roughness Quality of 3D Printed ABS Material

Additive manufacturing or 3D printing is one of the newer methods of manufacturing. The basic difference to other types of production is that the material is added in the form of layers. There are many types of technologies in 3D printing, but the most common is fused deposition modeling. This technology uses different types of thermoplastic materials to build an object. This paper will present the tribological characteristics and surface roughness measurement of samples printed on a low-cost 3D printer using thermoplastic materials ABS.

Investigation on the mold‐less curing process of 3D printing continuous carbon fiber reinforced thermoset composites based on thermoplastic shells constraint

AbstractTo overcome the dependence of continuous carbon fiber reinforced thermoset composites (CCFRTCs) on molds during the curing, a thermoset continuous fiber prepreg filament and thermoplastic filament alternate printing method was proposed. CCFRTCs with thin thermoplastic shells were prepared based on the method, and the confinement of thermoplastic shells enabled the mold‐less curing of CCFRTCs. The influence of key curing process parameters on the flexural properties of the specimens was systematically investigated. The experimental results showed that the flexural properties of the prepared composites were correlated positively with the vacuum degree and showed a tendency of first increasing and then decreasing with the increasement of impregnation time and curing temperature. Through x‐ray computed tomography (CT) and scanning electron microscope (SEM) analysis, the effect of key curing process parameters on the flexural properties of the CCFRTCs was clarified. Under the guidance of suitable curing process parameters, the flexural strength and modulus of the composite reached 482.89 MPa and 35.11 GPa, which were significantly better than most existing 3D printed continuous carbon fiber reinforced polymer composites. Finally, complex components were prepared to verify the feasibility and versatility of the technique.Highlights A CCFRTCs mold‐less curing method was proposed. The effect of key parameters on the properties of CCFRTCs was clarified. Both the advantages of thermoset and thermoplastic materials were obtained. Complex components with low porosity were prepared.

Investigation of the effect of electron beam irradiation on tensile, thermal and gas barrier properties of graphene nanoplatelet loaded thermoplastic nanocomposite films

Packaging materials based on lightweight and flexible thermoplastic/graphene composite films are gaining popularity in both the academic and industrial sectors. In this research work, graphene nanoplatelet (GNP) of 1–5 wt% was integrated into linear low density polyethylene (LLDPE) by employing melt compounding technique at 160 °C to produce flexible composite films. The LLDPE/GNP nanocomposite films were irradiated with doses up to 50 kGy using a 2.5 MeV electron beam accelerator in air at ambient temperature. The uniform distribution of GNP in the thermoplastic matrix obtained from FESEM analysis improved the samples' mechanical characteristics. As the GNP concentration in the LLDPE matrix increases, both the thermal stability and impermeability qualities (oxygen and water vapor) get significantly improved. Electron beam irradiation of film samples further enhances the physico-mechanical, thermal and gas barrier properties compared to non-irradiated composite films and neat LLDPE film. The tighter connections between graphene and LLDPE chains as well as the development of cross-linked networks by E-beam irradiation are responsible for the improved performance properties. Therefore, GNP incorporation as well as electron beam irradiation of thermoplastic nanocomposite films could be a viable alternative for producing high-performance and high-barrier flexible LLDPE/GNP composite films for packaging applications.

Charcot-Marie-Tooth Hastalığında Bilateral Pençe-Elin Düzeltilmesi İçin Ortez : Olgu Sunumu

Charcot-Marie-Tooth (CMT) is a common inherited peripheral nerve disorder. Although lower extremity deformities are more common in patients with CMT, claw-hand deformities and monkey hand deformities are also frequently seen. If these deformities are not corrected, they impair the biomechanics of the hand. Orthoses made of thermoplastic material are often used to correct these deformities. In this case, the results of the lumbrical bar orthosis applied to the bilateral claw-hand deformity in a patient with CMT are presented. Before and after orthosis use, dexterity was evaluated with the Purdue Pegboard test, hand grip strength was evaluated with a manual hand dynamometer, and pinch strength was evaluated with a pinchmeter. As a result of the evaluations, it was seen that the lumbrical bar orthosis corrected the claw-hand deformity, but did not cause improvements in hand grip strength, pinch strength and dexterity.

In Situ, Real-Time Temperature Mapping and Thermal FE Simulations of Large-Format 3D Printed PETG/CF Vertical Wall.

This work focuses on simulating the thermal history of a vertical wall consisting of a thermoplastic composite material, poly(ethylene terephthalate) glycol (PETG) with short carbon fiber reinforcement, manufactured using a Big Area Additive Manufacturing (BAAM) system. The incremental deposition process used in additive manufacturing, which corresponds to the repeated deposition of hot material onto cooler material, contributes to the presence of residual stresses and part warping. The prediction of these mechanisms is dependent on thermal history of the part, and the major motivation of this work was to improve the accuracy of finite element (FE) models used to quantify the thermal history of large-format additively manufactured parts. Thermocouples were placed throughout the part at varying heights to measure temperature as a function of time. The FE model developed found a thermal contact conductance between the printed part and the bed of 10 W/m2K and convection coefficient values that linearly varied from 3 to 15 W/m2K through the wall height when making a temperature comparison with the output from the thermocouples. It is also demonstrated that the FE model with a constant convection coefficient under-predicts model temperature at the beginning of the manufacturing process when compared against the model with a variable convection coefficient. The impact of this difference was seen in the stress values, which were larger for the model with a constant convection coefficient. Finally, a correlation equation was derived which allows the findings to be generalized to other vertical structures manufactured on the BAAM. In summary, this work offers valuable insights on material characterization, real-time thermocouple placement, and FE modeling of large-format additively manufactured parts.

Synthesis, Recycling and High‐Throughput Reprocessing of Phase‐Separated Vitrimer‐Thermoplastic Blends

AbstractPhase‐separated polymer blends including a transesterification vitrimer and polypropylene are synthesized from widely available precursors through reactive processing. It is shown that proper formulation during the process including a viscosity modifier of the vitrimer precursors and a reactive interface compatibilizer yields well‐dispersed vitrimer phases with fractions up to 75 wt.% in the polypropylene phase. These vitrimer blends can be easily reprocessed by multiple shredding‐injection cycles and processed in high‐shear conditions through capillary rheometry. Rheological analyses reveal that a percolating dynamic network is formed across the vitrimer domains. It breaks apart during high shear reprocessing of the material and dynamically reforms after thermal annealing of the blends. It therefore ideally combines the mechanical and high‐throughput (re)processing properties of the thermoplastic matrix minor phase with the chemical, thermomechanical, and dynamic properties of the vitrimer major phase. This work illustrates the decoupling of processing at high shear rates enabled by the polypropylene processing aid from the kinetics of dynamic exchanges of the vitrimer phase and thermomechanical properties at the service temperature of the blends.

Deformation kinetics of single-fiber polypropylene composites: Adhesion improvement at the expense of toughness

Despite the maturity of the technology, processing of fiber-reinforced thermoplastic materials remains challenging, and difficulties in processability often result in material formulations with high modulus and strength, yet rather poor ductility compared to the pure polymer matrix. To gain fundamental insight into the deformation mechanisms present in such materials, the complexity of the system is step-wise increased; first, the effect of the most commonly applied adhesion enhancement, the addition of MAH-g-PP compatibilizer, on the bulk properties is assessed. The small-strain tensile properties, i.e., modulus and yield stress, appear to be only marginally affected by the addition of such compatibilization agent, however, the strain-at-break is strongly reduced, even before the addition of the fiber reinforcement. Subsequently, using in-situ X-ray characterization methods upon tensile deformation, the time evolution of crystal structure and lamellar morphology is determined, and at first glance the compatibilizer addition appears to better preserve the crystalline structure. The onset of local failure (cavitation) is quantified at the interface of a single glass fiber. By increasing the adhesive interaction between fiber and matrix the stress concentration at the interface is increased, leading to an acceleration in void formation followed by unstable growth, which in turn strongly embrittles the composite. By the addition of various selective nucleating agents, it is demonstrated that the role of local phase composition and morphology on the deformation kinetics and subsequent failure mechanisms is much more pronounced than the increased adhesion between fiber and matrix by compatibilization or sizing effects. These findings may specify a new route towards tougher fiber-reinforced composites with reduced complexity in the material formulation.

Modeling, testing, and optimization of novel lattice structures for enhanced mechanical performance

Cellular materials have drawn increasing interest in numerous applications due to their promising specific stiffness, strength and energy absorption capacity. In this work, a variety of rather novel lattice topologies pertinent to additive manufacturing are derived and examined. A number of these are derived by free-domain and constrained domain topology optimization procedures, while others are inspired by the triply periodic minimum surface (TPMS) sheet-based topologies. The topology optimization module utilized a single objective function of minimizing strain energy under linear elastic conditions. A total of fifteen different lattice topologies are investigated numerically, including both novel and conventional topologies (e.g. strut-based lattices) and their effective elastic properties are determined with respect to relative density through finite element analysis (FEA). Based on the preliminary FEA results, a number of these topologies are selected of which tessellated lattice structures are fabricated through laser powder bed fusion (LPBF) additive manufacturing technique out of Nylon thermoplastic material. The tessellated lattice structures are experimentally tested in compression and their mechanical performance, including uniaxial modulus, yield strength, and energy absorption capacity (EAC), is assessed. FEA simulations have been conducted using an elastic-plastic constitutive model for the Nylon base material. Both the experimental and numerical results reveal that the mechanical performance of the novel tube-based TPMS lattice P-100 and the combined loading (CL) topology derived through free-domain topology optimization surpasses all other topologies. P-100 uses a primitive TPMS with equal-length tubular connections in each direction, where the tubular length percentage compared to the primitive lattice size is 100%, while CL lattice topology is a free domain topology optimized under compressive loads on the centers of faces, edges, and vertices toward the center. The innovative lattice topologies proposed in the current study, particularly the P-100 and CL topologies, can become crucial in applications where it is necessary to improve the energy absorption capacity, such as sandwich panel cores, supports, and infills for 3D printed components.

High-Efficiency Mono-Cyclopentadienyl Titanium and Rare-Earth Metal Catalysts for the Production of Syndiotactic Polystyrene.

Syndiotactic polystyrene (SPS) refers to a type of thermoplastic material with phenyl substituents that are alternately chirally attached on both sides of an aliphatic macromolecular main chain. Owing to its excellent physical and mechanical properties, as well as its chemical stability, high transparency, and electrical insulation characteristics, SPS is used in a wide variety of technical fields. SPS is commonly produced via the stereoselective transition metal-catalyzed coordination polymerization method mediated by stereospecific catalysts, which consists of anionic mono-cyclopentadienyl derivative η5-coordinated single active metal centers (referred to as "mono-Cp'-M"), with active center metals involving Group 4 transition metals (with an emphasis on titanium) and rare-earth (RE) metals of the periodic table. In this context, the use of mono-cyclopentadienyl titanocene (mono-Cp'Ti) catalysts and mono-cyclopentadienyl rare-earth metal (mono-Cp'RE) metallocene catalysts for the syndiospecific polymerization of styrene is discussed. The effects of the mono-cyclopentadienyl ligand structure, cationic active metal types, and cocatalysts on the activity and syndiospecificity of mono-Cp' metallocene catalysts are briefly surveyed.

Thermoplastic Electromagnetic Shielding Materials from the Integral Recycling of Waste from Electronic Equipment.

The European Green Deal's goals are anticipated to be fulfilled in large part thanks to the New Circular Economy Action Plan. It is believed that recycling materials will have a significant positive impact on the environment, particularly in terms of reducing greenhouse gas emissions and the impacts this will have on preventing climate change. Due to the complexity of the issue and its significant practical ramifications, the activity of Waste Electrical and Electronic Equipment (WEEE) collection networks is a subject of interest for researchers and managers, in accordance with the principles that recent laws have addressed in a large number of industrialized countries. The goal of this paper is to characterize and obtain composite materials using an injection process with a matrix of LDPE, PP, and HDPE, with up to a 10% addition of nonmetallic powders from PCBs and electronic parts from an integrated process of WEEE recycling. The composites present relevant thermal, electrical, and mechanical properties. Such composite materials, due to their relevant dielectric properties, may be further tested for applications in electromagnetic shielding at frequencies above 1 kHz, or for electromagnetic interference/electromagnetic compatibility (EMI/EMC and ESD) applications at lower frequencies due to their superior dielectric loss factor values, associated with relevant behaviors around exploitation temperatures, mainly for the electric, electronic, or automotive industries.

Zein as a Basis of Recyclable Injection Moulded Materials: Effect of Formulation and Processing Conditions.

The growing concern about reducing carbon footprint has led to the progressive replacement of traditional polymeric materials by natural-based biodegradable materials. However, materials from natural sources (i.e., plants) typically possess poorer mechanical properties when compared to conventional plastics. To counterbalance this, they need to be adequately formulated and processed to eventually meet the standards for certain applications. Zein is the major storage protein from corn and can be obtained as a by-product from the corn-oil industry. It is an excellent candidate for producing green materials due to its stability, biodegradability, renewability, and suitable mechanical and technical-functional properties. In the present work, zein was blended with a plasticizer (i.e., glycerol) at three different zein/glycerol ratios (75/25, 70/30, and 65/25) and then injection moulded at three different processing temperatures (120, 150, and 190 °C). The properties of both blends and bioplastics were evaluated using dynamic mechanical analysis (DMA), tensile tests, and water absorption capacity (WUC). The properties-structure interrelation was assessed through a scanning electron microscope. Generally, a higher zein content and processing temperature led to a certain reinforcement of the samples. Moreover, all bioplastics displayed a thermoplastic behaviour finally melting at temperatures around 80 °C. The lack of massive crosslinking enabled this melting, which finally could be used to confirm the ability of zein based materials to be recycled, while maintaining their properties. The recyclability of thermoplastic zein materials widens the scope of their application, especially considering its biodegradability.

Structural, magnetic, and electrical properties of a SrFe12O19/PLA composite

Polymer matrix nanocomposites are extensively explored due to their usefulness and relevant physicochemical properties. Once these properties are present instantaneously, reacting at relative stimuli, multifunctional applications are succeeded. In the current work, we have investigated the structural, magnetic, and electrical properties of a system formed from the SrFe12O19 hexaferrite (SrM) and polylactic acid (PLA). The SrM particles were obtained by solid reaction method and embedded in a PLA thermoplastic polymeric matrix to form the SrM/PLA composite. The structural, magnetic, and electrical properties were investigated from the experimental measurements obtained by X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), and impedance spectroscopy (IS), respectively. The Match-3 Software was used to determine the present phases in each sample. The results suggest the coexistence of both phases independently (SrM and PLA). In addition, the lattice parameters experience minimal variation for the individual phases of the compound. It was noticed that the magnetic properties are modulated as a function of the SrM hexaferrite phase concentrations and the magnetic interactions' nature. Finally, the electrical properties (impedance complex, real and imaginary permittivity) showed wide variability with changes in the phase content. For all samples, the characteristic values of s(300) between 0.9926 ± 0.0002 and 0.9737 ± 0.0003 indicated the electron hopping mechanism.

Development of Biodegradable Thermosetting Plastic Using Dialdehyde Pineapple Stem Starch.

Starch extracted from pineapple stem waste underwent an environmentally friendly modification process characterized by low-energy consumption. This process resulted in the creation of dialdehyde pineapple stem starch featuring varying aldehyde contents ranging from 10% to 90%. Leveraging these dialdehyde starches, thermosetting plastics were meticulously developed by incorporating glycerol as a plasticizer. Concurrently, unmodified pineapple stem starch was employed as a control to produce thermoplastic material under identical conditions. The objective of streamlining the processing steps was pursued by adopting a direct hot compression molding technique. This enabled the transformation of starch powders into plastic sheets without the need for water-based gelatinization. Consequently, the dialdehyde starch-based thermosetting plastics exhibited exceptional mechanical properties, boasting a modulus within the range of 1862 MPa to 2000 MPa and a strength of 15 MPa to 42 MPa. Notably, their stretchability remained relatively modest, spanning from 0.8% to 2.4%. Comparatively, these properties significantly outperformed the thermoplastic counterpart derived from unmodified starch. Tailoring the mechanical performance of the thermosetting plastics was achieved by manipulating the glycerol content, ranging from 30% to 50%. Phase morphologies of the thermoset starch unveiled a uniformly distributed microstructure without any observable starch particles. This stood in contrast to the heterogeneous structure exhibited by the thermoplastic derived from unmodified starch. X-ray diffraction patterns indicated the absence of a crystalline structure within the thermosets, likely attributed to the establishment of a crosslinked structure. The resultant network formation in the thermosets directly correlated with enhanced water resistance. Remarkably, the thermosetting starch originating from pineapple stem starch demonstrated continued biodegradability following a soil burial test, albeit at a notably slower rate when compared to its thermoplastic counterpart. These findings hold the potential to pave the way for the utilization of starch-based products, thereby replacing non-biodegradable petroleum-based materials and contributing to the creation of more enduring and sustainable commodities.

Processing of membranes and 3D scaffolds based on n-TiO2 colloidally dispersed on a thermoplastic matrix for photocatalytic pollutant removal

One of the most promising technologies for water treatment today is photocatalytic membrane reactors (PMRs). Manufacturing efficient membranes is still challenging as many factors are involved, like the porosity, specific surface area, nature and size of particles. In this work, a colloidal method to self-support commercial nanoparticles (n-TiO2) in a polymeric matrix of polylactic acid (PLA) is proposed allowing the fabrication of 2D and 3D structures with high inorganic content that can be adapted to the PMR configurations. Using a commercial filament of PLA loaded with up to 15 vol% of n-TiO2 as starting point, photocatalytic membranes have been manufactured by FFF. In addition, following a similar process, tapes with n-TiO2 particles up to 15 vol% have been processed by tape casting. Thermal characterisation (DTA) and dynamic rheometry evaluated the commercial filament for printing to determine the conditions used during the thermal extrusion and printing processes. FTIR and XRD technologies were used to determine the chemical interactions of PLA matrices with TiO2 nanoparticles. Porosity was measured by Archimedes's method for the filaments, by mercury intrusion for the membranes and by optical microscopy for the scaffolds. Finally, the microstructure of the 2D and 3D pieces was evaluated by scanning microscopy. 2D tape cast membranes were compared with individual filaments and 3D printed scaffolds in linear and gyroidal geometries. The catalytic activity results indicate that tape cast membranes show much higher kinetic constants than the individual filaments and the linear and gyroidal scaffolds. Regarding the two different printed scaffolds, in contrast to the kinetic values, gyroidal geometries achieve an average degradation time (t50) of 6.1 h, which is a lower value than those observed for linear scaffold geometries. Methyl orange degradation tests after 24 h exposure under UV light showed degradation rates of 98% for membranes, 90% for commercial filaments, 80% for gyroidal scaffolds and 60% for linear patterns. Therefore, these results are promising as a solution for fabricating easily extractable self-supported membranes for water treatment in PMRs.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse.

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Enhanced Interfacial Properties of Carbon Fiber/Maleic Anhydride-Grafted Polypropylene Composites via Two-Step Surface Treatment: Electrochemical Oxidation and Silane Treatment.

The interfacial adhesion between carbon fibers (CFs) and a thermoplastic matrix is an important aspect that should be improved in manufacturing CF-reinforced thermoplastics with high strength and rigidity. In this study, the effects of a two-step surface treatment comprising electrochemical oxidation and silane treatment of the CF surface on the mechanical properties of CF/maleic anhydride-grafted polypropylene (MAPP) composites were confirmed. The surface characteristics of the treated CFs were analyzed via scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The tensile testing of a single CF and interfacial adhesion of the samples before and after the surface treatment were analyzed using a single-fiber testing machine and a universal testing machine. After the silane treatment, the roughness of the CF surface increased due to the formation of a siloxane network. In addition, the interfacial shear strength increased by ∼450% compared to that of the untreated CFs due to the covalent bond between the -NH2 end group of siloxane and MAPP. This two-step surface treatment, which can be performed continuously, is considered an effective method for improving the mechanical interface strength between the CF and polymer matrix.