Agnieszka Leszczyńska

Physical characteristics of nanoparticles emitted during drilling of silica based polyamide 6 nanocomposites

During the past decade, polymer nanocomposites have emerged as a novel and rapidly developing class of materials and attracted considerable investment in research and development worldwide. However, there is currently a lack of information available in the literature on the emission rates of particles from these material. In this study, real-time characterization of the size distribution and number concentration of sub-micrometer-sized particles (5.6-512 nm) emitted from polyamide 6 nanocomposites during mechanical drilling was made. For the first time, four different silica based filler of commonly use were assessed. Further, the respective emission rates were determined based on the particle population and the time. The measurements showed that the particle emission rates ranged from 1.16E+07 (min?1) to 1.03E+09 (min?1) and that the peak diameters varied from 29.6 to 75.1 nm. Airborne particles in the nanometer range (11.1-46.8 nm), in the ultrafine range (51.3-101.1 nm) and in the accumulation mode range (111.9-521 nm) accounted for 34.1% to 76.6%, 8.3% to 47% and 4.1% to 24.2% of the total emission rates, respectively, depending on the type of filler. Additionally, deposited particles were sampled and characterized, to explore any possible correlation between deposited and airborne particles. The result clearly showed that with increasing airborne particle concentration the deposit particle concentration decreased and vice verse.

Bio-polyamides based on renewable raw materials

Structural characterization of a series of novel bio-polyamides based on renewable raw materials—PA 4.10, PA 6.10, PA 10.10, and PA 10.12—was performed by Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction (WAXD). Infrared spectra and the WAXD patterns indicate the coexistence of different crystalline forms, α- and γ-triclinic and β-pseudohexagonal. Thermal properties in the glass transition (Tg) and melting region were then investigated using temperature-modulated DSC (TOPEM® DSC). The melting point (Tm) was found to increase with increasing amide/methylene ratio in the polymer backbone, which is consistent with the increase in linear density of hydrogen bonds. Studies on the molecular dynamics by dynamic mechanical analysis show three distinct regions associated with the γ- and the β-relaxation and the dynamic glass transition. TOPEM® DSC data reveal that at low frequency/long timescales, the materials with significantly different amide/methylene ratios have similar segmental dynamics.

Structure-Property Relationships in Polyoxymethylene/Thermoplastic Polyurethane Elastomer Blends

A series of blends of polyoxymethylene (POM) / thermoplastic ester-based polyurethane elastomer (TPU) has been obtained by using a double screw extruder (L/D = 25) in the temperature range of 175-190°C. Differential scanning calorimetry (DSC) was applied to investigate the influence of TPU on the melting and crystallisation of POM; it was found that there is a decrease of the enthalpy of melting with an increase of TPU amount in the blend (up to 10 wt %); enthalpy of fusion also decreases. X-ray diffraction patterns confirm that the crystalline structure of POM remains unaffected after blending with multiphased TPU. Morphology of the blends, investigated by scanning electron microscopy (SEM), showed that TPU is distributed rather uniformly in POM and forms cylindrical-shaped domains of ca. 10 μm length. Homogeneous distribution may be the consequence of existence of specific interactions in form of hydrogen bonding between ether oxygen (POM) and hydrogen from urethane group (TPU) as evidenced by FTIR measurements. Modified morphology contributes to the better mechanical properties; elongation at break increases with an increase of the TPU content in the blend (for TPU content > 10%).

On Nanoparticles Release from Polymer Nanocomposites for Applications in Lightweight Automotive Components

Nano and micro reinforced glass fibre-polymer composites have been manufactured to investigate different effect such as filler type, filler size and matrix materials on the particle emission during low velocity impact test. Nano and micro- silica, as well as nanoclay reinforced crash cones were prepared with a two step extrusion process and final injection moulding of the structures. The addition of secondary filler into the glass-fibre reinforced polymer composites had significant influence on the mechanical behaviour of the material as well as on the particle emission. In general, nano and ultrafine airborne particles were emitted from all investigated materials. However, composite filled with nanoclay emitted higher amounts of particles than those filled with nano and microsilica. One reason for the increase of particle emission of the nanoclay filled composites was the change of the failure behaviour of the matrix. However, similar results of particle emission were obtained for both nano and microsilica fillers, which in general did not vary significantly from the results obtained from traditionally reinforced glass fibres polymer composites.

Thermal Stability and Degradation of Polymer Nanocomposites

Polymer nanocomposites are a growing field of research that aims at developing new nanostructured materials with enhanced properties. Structure–property relationships are sought as certain phenomena at nanoscale still need to be explained. Thermal stability and degradation behavior of polymer nanocomposites are of paramount importance due to fundamental reasons and for future practical applications. Hence, this chapter presents discussion on the thermal stability and degradation of polymer nanocomposites with special attention paid to the influence of different types of nanofillers on the thermal stability of polymer nanocomposites. Novel approaches in stabilization of polymer nanocomposites using synergistic effects between nanofillers and classical stabilizers are also presented.

The Mechanical and Thermal Properties of Polyoxymethylene (POM)/Organically Modified Montmorillonite (OMMT) Engineering Nanocomposites Modified with Thermoplastic Polyurethane (TPU) Compatibilizer

In this work the effect of macromolecular polyurethane compatibilizer on the structure, mechanical and thermal properties of polyoxymethylene/organically modified montmorillonite (POM/OMMT) nanocomposites was investigated. The thermal stability of obtained systems was significantly enhanced by compatibilizer both in oxidative and inert atmosphere. The thermoanalytical methods (TG-FTIR and TG-MS) were used for identification of gaseous products of degradation. The results showed less intensive evolution of formaldehyde and formic acid during the thermal degradation of POM/TPU/OMMT nanocomposites. Both formaldehyde and formic acid had an autocatalytic effect on degradation of neat POM and POM/MMT nanocomposites, especially in the initial stage of the process. However, in the presence of TPU the monomer formed in depolymerization reaction was captured most probably by urethane linkage in a formylation process. The decreased concentration of catalytic agent is considered as a cause of the reduced rate of mass loss of POM/TPU/OMMT nanocomposites. Interestingly, during thermooxidative degradation the temperature of maximum rate of mass loss was shifted towards higher temperature more than it could be anticipated from the TGA results obtained for neat POM, POM/TPU blend and POM/OMMT nanocomposite material with corresponding contents of nanofiller and compatibilizer. It is likely that the mechanism of thermal stabilization may be also related to the physical barrier effect of layered silicate towards oxygen diffusion. Both chemical and physical mechanisms of stabilization are referred to the structure and interfacial area developed in nanocomposite materials and thus can be influenced by addition of a compatibilizer. The obtained POM/TPU/OMMT nanocomposites revealed higher impact strength as compared to POM/OMMT materials due to the presence of elastomeric domains facilitating the dissipation of impact energy.

Optimization and Scaling up of the Fabrication Process of Polymer Nanocomposites: Polyamide-6/Montmorillonite Case Study

Although polyamide (PA) nanocomposites reinforced with montmorillonite (MMT) are processed for more than two decades, the primary technological problem related to optimization of processing conditions to fully exploit properties of these nanomaterials has still to be addressed. The processing of polymer nanocomposites by melt intercalation consists, in principle, of the following stages: preparation and drying of raw materials, preparation of a premix masterbatch, dosing the premix masterbatch into a feeding zone, heating and melting the polyamide-based matrix, an extrusion of a fluid composition followed by a set of auxiliary operations. The process of obtaining polyamide nanocomposites with the desired properties depends on numerous processing parameters that, when varied, affect the quality of manufactured products. Therefore, in this chapter techniques for obtaining polyamide-6/montmorillonite nanocomposites (PA6/MMT NCs), are presented along with discussion of the optimization process for the preparation of PA nanocomposites. Important technological problems arising during the processing are discussed in this chapter, as well as present issues which need to be addressed in scaling up the production from laboratory to industrial scale.

The effect of matrix and reinforcement material selection on the tensile properties of hybrid composites.

This work was funded by the European Commission (FP7 Project- CP-FP; Project Reference: 228536-2). The authors also gratefully acknowledge the EPSRC for providing testing equipment, as well as Grado Zero Espace SRL and Laviosa Chimica Mineraria SPA for the preparation of the materials.

Comparison of the rheological properties of polyamide-6 and its nanocomposites with montmorillonite obtained by melt intercalation

Comparison of the rheological properties of polyamide-6 and its nanocomposites with montmorillonite obtained by melt intercalation

The influence of The mold temperature on the properties of polyamide composites

Each varying parameter which can contribute to the quality of received applications plays an important role in the processing of polymer materials. The influence of mold temperature on the molded parts’ properties and density was investigated during the optimization of injection molding process parameters of polyamide-6 (PA-6) as well as polyamide-6/montmorillonite (PA-6/MMT) composites. The hardness and Izod notched impact strength were determined for the obtained PA-6-based materials.