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

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

The influence of the character peculiarities of the personality of the teacher on behavior in a conflict situation

In order to avoid confl in an educational organization, it is necessary to be able to identify correctly the personal characteristics of employees, to understand how different characterological features of the individual affect behavior, including in conflict situations and, taking into account the knowledge gained, to choose leadership styles, communication, to develop the foundations of corporate ethics. The concept of conflict, conflict situation, pre-conflict situation and accentuations of character has been considered in the article, the main functions and causes of the conflict have been revealed. The results of an empirical study of the teaching staff of an educational organization on the influence of the characterological features of the teacher’s personality on the strategy of behavior in a conflict situation have been adduced. The interrelation of character accentuations and choice of strategy of behavior in a conflict situation has been revealed

Domain diversity and polarization switching in amino acid β-glycine

Piezoelectric materials based on lead zirconate titanate are widely used in sensors and actuators. However, their application is limited because of high processing temperature, brittleness, lack of conformal deposition and, more importantly, intrinsic incompatibility with biological environments. Recent studies on bioorganic piezoelectrics have demonstrated their potential in these applications, essentially due to using the same building blocks as those used by nature. In this work, we used piezoresponse force microscopy (PFM) to study the domain structures and polarization reversal in the smallest amino acid glycine, which recently attracted a lot of attention due to its strong shear piezoelectric activity. In this uniaxial ferroelectric, a diverse domain structure that includes both 180° and charged domain walls was observed, as well as domain wall kinks related to peculiar growth and crystallographic structure of this material. Local polarization switching was studied by applying a bias voltage to the PFM tip, and the possibility to control the resulting domain structure was demonstrated. This study has shown that the as-grown domain structure and changes in the electric field in glycine are qualitatively similar to those found in the uniaxial inorganic ferroelectrics. © 2019 by the authors

β-glycine piezoelectric and ferroelectric properties behavior at elevated temperatures

The research was carried out using equipment of Ural Center for Shared Use "Modern Nanotechnologies" Ural Federal University. The reported study was funded by RFBR according to the research project № 18-32-00390

Linear magnetoresistance in compensated graphene bilayer

We report a nonsaturating linear magnetoresistance in charge-compensated bilayer graphene in a temperature range from 1.5 to 150 K. The observed linear magnetoresistance disappears away from charge neutrality ruling out the traditional explanation of the effect in terms of the classical random resistor network model. We show that experimental results qualitatively agree with a phenomenological two-fluid model taking into account electron-hole recombination and finite-size sample geometry

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

Polymorphic phase transitions and ferroelectric properties in β-glycine single crystals and micro islands

The research was carried out using equipment of Ural Center for Shared Use "Modern Nanotechnologies" Ural Federal University with the financial support by the Government of the Russian Federation (Resolution 211, Contract 02.A03.21.0006). The reported study was funded by RFBR according to the research project № 18-32-00390