Single polymer laminate composites by compression molding of knitted textiles and microparticles of polyamide 6: Preparation and structure-properties relationship

Knitted reinforced single polymer laminate composites based on polyamide 6 (KSPCsPA6) were produced bycompression molding of polyamide 6 microparticlesMPs()PA6powder-coating annealed PA6 Rib or Jersey knittedtextile structures. TheMPsPA6were synthesized by solution/precipitation activated anionic ring-opening poly-merization ofε-caprolactam. The tensile properties ofKSPCsPA6were studied in relation to the knitted re-inforcement architecture,fiber volume fraction, ply orientation and stacking orders. The tensile stiffness andstrength of the newly preparedKSPCsPA6withfiber content of 15% showed significant improvements as com-pared to the neat anionic PA6 matrix and to commercial hydrolytic PA6 (HPA6). The mechanical behavior of theKSPCsPA6was correlated with the geometry parameters of the knitted reinforcements, the polymorph content ofthe samples and their crystallinity indexes determined by differential scanning calorimetry and wide-angle X-raydiffraction. The fracture behavior of KSPCsPA6was investigated by electron microscopy complemented by si-mulation studies.All authors gratefully acknowledge the support of the project TSSiPRO-NORTE-01-0145-FEDER-000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund. This work was partially financed by FEDER funds through the Competitiy Factors Operational Program - COMPETE and by national funds through FCT – Foundation for Science and Technology within the project POCI-01-0145-FEDER-007136. SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. NVD thanks for the financial support of FCT through the strategic projects LA25/2013-2014 and UID/CTM/50025/2013. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant

Microstructural-mechanical properties relationship in single polymer laminate composites based on polyamide 6

This paper studies theflexural and the impact properties of polyamide 6-based knitted reinforced single polymercomposites (KSPCs) prepared by compression molding of powder-coated textile structures. To prepare matrixcomponent, polyamide 6 microparticles (MPs) were synthesized by activated anionic ring-opening poly-merization ofε-caprolactam in solution and then used for powder-coating of the knitted structures. The influenceof the reinforcements' architecture, plies orientation, stacking order andfiber content on thefinal mechanicalproperties of KSPCs were investigated. Rib1 × 1 and Jersey knitted structures were selected as reinforcementsand treated by a stretching-annealing procedure to modify their mechanical properties. The anisotropic tensileand compression properties imparted by the knitted structures were found to be the major factors determiningthe impact andflexural behavior of KSPCs. Moreover, reinforcement's crossover points, the plies orientation andthe presence of a transcrystalline layer at the matrix-reinforcement interface were identified as relevant para-meters. The fracture mechanism of KSPCs was linked to the morphology and crystalline structure of the resultingcomposites and investigated by simulation andfinite element analysis of knitted reinforcemenents.This work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project POCI-01-0145-FEDER 007136. SDT thanks FCT for his Ph.D. Grant SFRH/BD/94759/2013. NVD thanks for the financial support of FCT in the frames of the stra tegic project UID/CTM/50025/2013. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. All authors gratefully acknowledge the support of the project TSSiPRO-NORTE-01-0145-FEDER-000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Comparative structural and mechanical studies on polyamide 6 knitted-reinforced single polymer composites prepared by different reactive processing techniques

Single polymer laminate composites based on anionic polyamide 6 (PA6) matrix-reinforced by PA6 knitted textile structures (KSPC) were produced by nylon reactive injection molding and powder coating/compression molding (PCCM) processing techniques. The effect of the reinforcement’s structure and the fiber volume fraction on the mechanical properties of the knitted-reinforced PA6 composites resulting from the two methods were investigated and compared. The morphology and the crystalline structure of KSPC materials were studied to identify the main factors determining the tensile properties. The results showed that the PCCM method produced laminate composites with higher Young’s modulus and mechanical strength in tension. Microscopy, differential scanning calorimetry and X-ray diffraction experiments were carried out to correlate the morphology and crystalline structure of the composites and their precursors with the different tensile behavior of KSPC prepared using the two techniques. The microscopy and X-ray scattering studies suggested the formation of a transcrystalline layer at the matrix/reinforcement interface. POLYM. COMPOS., 40:E886–E897, 2019. © 2018 Society of Plastics EngineersThis work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project POCI‐01‐0145‐FEDER‐007136. SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. NVD thanks for the financial support of FCT in the frames of the strategic project UID/CTM/50025/2013. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. All authors gratefully acknowledge the support of the project TSSiPRO‐NORTE‐01‐0145‐FEDER‐000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Structure–properties relationship in single polymer composites based on polyamide 6 prepared by in-mold anionic polymerization

Single polymer composites (SPCs) based on polyamide 6 (PA6) were prepared by in-mold activated anionic ring-opening polymerization (AAROP) of capro- lactam in the presence of PA6 textile fibers. The influence of the reinforcing fibers content, their surface treatment, as well as of the temperature of AAROP upon the morphol- ogy, crystalline structure, and mechanical properties of the resulting SPCs was followed. The presence of oriented transcrystalline layer (TCL) on the surface of the rein- forcing fibers was demonstrated by means of microscopy methods. Its orientation and polymorph structure were determined by synchrotron wide-angle X-ray scattering. Studies on the mechanical behavior in tension of the SPCs showed a well-expressed growth of the stress at break (70–80 %) and deformation at break (up to 150–190 %) in composites with 15–20 wt% of reinforcements. The best mechanical properties were found in SPCs whose rein- forcing fibers were solvent-pretreated prior to AAROP in order to remove the original finish. In these samples a stronger adhesion at the fiber/matrix interface was proved by scanning electron microscopy of cryofractured samples. This effect was related to a thinner TCL in which the α-to-γ polymorph transition is impeded.Strategic Project LA 25-2011-2012 financed by Fundação para a Ciência e a Tecnologia (FCT) - PortugalHASYLAB at DESY (Grant Number II-07- 011EC)FCT post-doctoral award SFRH/BPD/45252/2008, co-financed by QREN-POPH program of EU

Semi-automatic laboratory equipment for reactive injection molding

Traditional melt processing techniques limit in shape and thickness the parts of fiber-reinforced thermoplastic composites. Producing of thermoplastic hybrid composites through melt intercalation often results in heterogeneous products due to micron-scale agglomerations with a negative effect on the mechanical properties. The in-situ polymerization processes to form the matrix in polymer composites have proved to be a good approach toward the resolution of these issues. In the present work we report on the design and con-struction of a prototype semi-automatic laboratory equipment for reactive injection molding and its application for the preparation of various types of polyamide-6 based composites via in-situ activated anionic polymerization of ε-caprolactam.Fundação para a Ciência e Tecnologia grant SFRH/BPD/45252/2008 co-funded by FS

Tunable electromagnetic interference shielding properties of binary thermoplastic composites prepared by reactive microencapsulation

The Supporting Information is available free of charge at: https://pubs.acs.org/doi/10.1021/acsapm.2c00084Thermoplastic composites integrating carbon nanotubes (CNT) and micron-sized metal particles dispersed in polymer matrices can address emerging multifunctional needs, e.g., good electrical conductivity and electromagnetic interference (EMI) shielding combined with easy processing and affordable costs. Herein, an approach based on reactive microencapsulation is reported to prepare polyamide 6 (PA6)-based composites comprising binary loads of CNT and Al, Cu, or Fe particles. The microencapsulation is performed by activated anionic polymerization of ε-caprolactam in solution, in the presence of the metal/CNT loads. The resulting hybrid microparticles are compression-molded into plates containing effective metal/CNT loads in the range of 12–17 wt %. Among the materials synthesized, the one containing Al/CNT binary load (3:7 wt %) displays the highest EMI shielding effectiveness (SE) of 43.5 dB at 12 GHz, with a 2 mm thickness and an electrical conductivity σdc of 6.61 × 10–3 S/cm. A synergetic effect is observed in all of the metal/CNT PA6 samples in terms of both σdc and SE increase. Evidently, the presence of metal particles well dispersed in the conductive CNT network contributes to the mobility of the carriers and thus to the effective attenuation of the electromagnetic waves. Therefore, the binary composites of this study can be efficient thermoplastic EMI shielding materials.The authors gratefully acknowledge the technical support of Hugo Mostardinha from the Instituto de Telecomunicações Aveiro during the EMI shielding measurements and the financial support of Fundação para a Ciência e Tecnologia (FCT), Project UID/CTM/50025/2019. F.M.O. thanks FCT for the Ph.D. grant PD/BD/114372/2016 (AdvaMTech Ph.D. Program in Advanced Materials and Processing). The assistance of Prof. Nuno Carvalho from the University of Aveiro, Portugal, in the EMI shielding experiments is also gratefully acknowledged

Micromechanical finite element parametric study of polyamide 6 based single polymer composites reinforced by woven textile structures

This study presents a finite element-based micromechanical analysis of woven single polymer composites (WSPC), prepared by compression molding from polyamide 6 (PA6) woven fabrics powder-coated with PA6 microparticles. Initially, the PA6 microparticles (MP) were synthesized by solution/precipitation activated anionic ring-opening polymerization of ε-caprolactam. After the powder coating, the MP fraction upon each textile ply was transformed into the continuous PA6 matrix by hot pressing at a temperature lower than the melting of the PA6 textile reinforcements. Plain and satin PA6 woven fabrics were selected as reinforcements that were stretched and annealed prior to molding so as to enhance their mechanical performance. The tensile and Izod impact properties of WSPC were characterized in relation to the reinforcement architecture, fiber content and ply orientation. Finite element analysis was used for a parametric study of woven reinforcements and to correlate the deformation and stress distribution of the structures with the tensile failure of the composites. Moreover, to assess the interfacial matrix-reinforcements bonding state, a study of the surfaces fracture, obtained by SEM topography, using image processing was performed.This work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project POCI-01-0145-FEDER007136. SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. NVD thanks for the financial support of FCT through the strategic project UID/CTM/50025/2013. ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. All authors acknowledge the support of the project TSSiPRO-NORTE-01-0145-FEDER-000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Mechano-morphological studies of polyamide 6 based single polymer laminate composites prepared by different reactive processing techniques

Single polymer laminate composites based on polyamide 6 (PA6) were prepared by two methods: (i) reactive injection molding and (ii) powder coating/compression molding, both carried out in the presence of PA6 woven textile plies. The effect of the textile volume fraction Vf on the tensile properties of all composites was investigated. The laminates obtained by powder coating/compression molding displayed best mechanical performance, whereby in the composites with Vf = 15%, the improvement of the elastic modulus reached 98% in respect to commercial hydrolytic PA6 reference, or 50–86% as compared to neat anionic PA6 samples. Polarizing light microscopy with image processing was used for morphological characterization. A transcrystalline layer at the fiber-matrix interface was detected in all laminates with thicknesses between 0.5 and 3.0 μm, depending on the preparation technique applied. The thermal stability was studied in the temperature range of 30°C-550 °C. The laminates obtained by reactive injection molding displayed the lowest initial decomposition temperature due to the presence of oligomers. Selected laminate composites were reprocessed by grinding and injection molding. The recycled composites obtained by powder coating displayed a 38% increase of the elastic modulus in respect to commercial hydrolytic PA6 thus confirming the sustainability and recyclability of PA6-based single polymer composites.This work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project .POCI-01-0145-FEDER 007136 SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. ZZD and NVD thank the National Funds through FCT-Portuguese Foundation for Science and Technology, project reference UID/CTM/50025/2019. All authors gratefully acknowledge the support of the project TSSiPRO NORTE-01-0145-FEDER-000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Synchrotron X-ray studies on polyamide composites prepared by reactive injection molding

Semicrystalline polyamide 6 (PA6) and composites on its basis are among the most frequently used polymer materials for highly demanding applications. The performance of these composites depends on the crystalline structure of the PA6 matrix in which two crystalline forms most frequently coexist: α- and γ-polymorphs. This work reports on the crystalline structure of a variety of composite materials produced by in-mold reactive polymerization of caprolactam in specially designed semi-automatic equipment for reactive processing of nylons (NYRIM), carried out in the presence of particulate mineral reinforcements (natural or-ganically treated aluminum silicates and synthetic titanosilicates), PA6 oriented monofilaments and textile structures of glass fibers. The morphology and the crystalline structure of all composites were studied by syn-chrotron X-ray diffraction. Transcrystalline PA6 layer was observed in all fibrous PA6 laminates whose struc-ture fine crystalline structure was accessed.Fundação para a Ciência e Tecnologia; German Synchrotorn Radiation Source - DESY, Hambur