Thermal properties of glass fiber reinforced polyamide 6 composites throughout the direct long‐fiber reinforced thermoplastic process

The direct long‐fiber reinforced thermoplastic (D‐LFT) process offers a streamlined material processing technique and decreases the degradation of the material. To ensure product consistency and process optimization, it is imperative to understand how the process sequence affects degradation and thermal properties of the material during the D‐LFT process. This study investigates variation in molecular weight and thermal properties of the glass fiber reinforced polyamide 6 (PA6) composites throughout the D‐LFT process. Viscosity number (VN) measurements, thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC) analyses were performed on samples taken from different locations along the D‐LFT process. It was found that VN, which is a measure of molecular weight of the PA6 base resin, decreased throughout the processes. In contrast, TGA results suggested that apparent activation energy for decomposition increased during consecutive process stages. Non‐isothermal DSC results showed that there were no significant changes to the degree of crystallization; however, isothermal DSC results indicated that later stages of the process showed a decrease in crystallization half‐time, and the largest changes were observed in areas after the two extrusion portions of the process. POLYM. ENG. SCI., 58:46–54, 2018. © 2017 Society of Plastics Engineers     

Usefulness of myeloperoxidase as a biomarker for the ranking of pulmonary toxicity of nanomaterials

Background

In order to examine whether myeloperoxidase (MPO) can be a useful marker for evaluating the pulmonary toxicity of nanomaterials, we analyzed MPO protein in bronchoalveolar lavage fluid (BALF) samples obtained from previous examinations of a rat model. In those examinations we performed intratracheal instillation exposures (dose: 0.2–1.0 mg) and inhalation exposures (exposure concentration: 0.32–10.4 mg/m³) using 9 and 4 nanomaterials with different toxicities, respectively. Based on those previous studies, we set Nickel oxide nanoparticles (NiO), cerium dioxide nanoparticles (CeO₂), multi wall carbon nanotubes with short or long length (MWCNT (S) and MWCNT (L)), and single wall carbon nanotube (SWCNT) as chemicals with high toxicity; and titanium dioxide nanoparticles (TiO₂ (P90) and TiO₂ (Rutile)), zinc oxide nanoparticles (ZnO), and toner with external additives including nanoparticles as chemicals with low toxicity. We measured the concentration of MPO in BALF samples from rats from 3 days to 6 months following a single intratracheal instillation, and from 3 days to 3 months after the end of inhalation exposure.

Results

Intratracheal instillation of high toxicity NiO, CeO_2, MWCNT (S), MWCNT (L), and SWCNT persistently increased the concentration of MPO, and inhalation of NiO and CeO₂ increased the MPO in BALF. By contrast, intratracheal instillation of low toxicity TiO₂ (P90), TiO₂ (Rutile), ZnO, and toner increased the concentration of MPO in BALF only transiently, and inhalation of TiO₂ (Rutile) and ZnO induced almost no increase of the MPO. The concentration of MPO correlated with the number of total cells and neutrophils, the concentration of chemokines for neutrophils (cytokine-induced neutrophil chemoattractant (CINC)-1 and heme oxygenase (HO)-1), and the activity of released lactate dehydrogenase (LDH) in BALF. The results from the receiver operating characteristics (ROC) for the toxicity of chemicals by the concentration of MPO proteins in the intratracheal instillation and inhalation exposures showed that the largest areas under the curves (AUC) s in both examinations occurred at 1 month after exposure.

Conclusion

These data suggest that MPO can be a useful biomarker for the ranking of the pulmonary toxicity of nanomaterials, especially at 1 month after exposure, in both intratracheal instillation and inhalation exposure.

     

New materials in automotive tribology

The rapid, world‐wide spread of automobiles has necessitated the development of improved technologies for environmental protection, resource utilization and customer satisfaction. As the designs of automotive components have changed, emphasis has shifted to tribological approaches. New tribo‐materials are needed for automotive components that must run at higher temperatures and higher [pressure] x.[velocity] conditions. This paper outlines current issues related to tribo‐materials in passenger cars. This revised version was published online in June 2006 with corrections to the Cover Date.     

Studies on the friction and transfer of semicrystalline polymers

The friction and transfer of various semi-crystalline polymers were studied in several experiments. The cylindrical surfaces of polymers were slid over glass plates at low speed and under constant load. The kinetic friction of PTFE in repeated traverses did not vary with the number of traverses and the transfer of PTFE occurred successively on previously transferred PTFE films. The film transferred at each traverse was extremely thin (< 50 Å). The friction of PTFE decreased with increased humidity in the environment and appeared to be independent of crystalline transitions. Other polymers exhibited higher friction than PTFE and their transfer was generally as small lumps or short streaks. HDPE displayed a very low friction, although the friction of ultrahigh molecular weight polyethylene (UHDPE) was somewhat higher than that of HDPE. With HDPE and UHDPE, as well as with PTFE, long films stretched from one side of the abrasion grooves produced on the polymer frictional surfaces to the other side, like a bridge. The static friction of the three different polymers was very sensitive to the direction of prerubbing on the frictional surfaces and the static friction in sliding parallel to the pre-rubbing direction was much smaller than that perpendicular to it. The roles of the molecular profile and of the banded or spherulitic structure of the polymers in the polymer transfer mechanism are discussed on the basis of the experimental results obtained.     

Optical 3D profilometer for in-process measurement of microsurface based on phase retrieval technique

We have proposed an optical method that can be applied to in-process or in situ measurement of the microsurface profile. The present method is based on optically performed spectral analysis and the phase retrieval technique. Spectral information of a surface profile is obtained by measuring the Fraunhofer diffraction intensity. The phase retrieval technique is used to reconstruct the surface profile from the measured spectrum. We have developed an instrument on the basis of the general principles of the present method, and measured the surface of a reference standard having rectangular pockets 44 nm deep at intervals of 10 μm. The measured surface profile was in good agreement with the nominal dimensions of the specimen as well as the surface profile obtained by atomic force microscopy (AFM).     

Toner Display Based on Movement of Tribo-electrically Charged Particles

The mechanism of toner display based on an electrical movement of black and white charged particles has been investigated. Two kinds of particles of black and white charged in the different electric polarity are enclosed in two ITO transparent electrodes using an insulating spacer. The particle movement is controlled by the external electric field applied between two transparent electrodes. The black toner is adhered on the electrode by an electrostatic force across the CTL to display a black image. The toners can be put back to the counter electrode by applying a reverse electric field, and a white image is formed. The black and white solid images are displayed by the switch of polarity of applied voltage in toner display cell. The polarity of charge and the value of charge to mass ratio of two particles were measured by observation of the particle separation on the surface-type electrodes and using q/m meter, respectively.     

Viscoelastic-plastic behaviour with mean strain changes in polypropylene

The stress-strain curves and stress-relaxation curves of polypropylene are obtained by using a closed-loop, electrohydraulic, servo-controlled testing machine. Effects of mean strain changes on deformation behaviour are examined in a tension-compression mode under strain control at room temperature (18–23 °C). The hysteresis loops of three mean strains show a steady-state response from the stress-strain curves at a strain rate of 1 × 10^–3 s^–1 at a strain width of 5%, at a number of cycles of N=50 and at three mean strains (_m=0, + 1.0 and + 2.0%). The drop of stress at the mean strain of _m= -1.0% is larger in magnitude than that at _m=+1.0%; this is caused by the higher stress level at _m=- 1.0% as compared with the stress level at _m=+1.0%. From the results of stress amplitude and the stress drop behaviour, the magnitude of stress drop is hardly affected by the mean strain.     

Data-dependent dissimilarity measure: an effective alternative to geometric distance measures

Nearest neighbor search is a core process in many data mining algorithms. Finding reliable closest matches of a test instance is still a challenging task as the effectiveness of many general-purpose distance measures such as \(\ell _p\)-norm decreases as the number of dimensions increases. Their performances vary significantly in different data distributions. This is mainly because they compute the distance between two instances solely based on their geometric positions in the feature space, and data distribution has no influence on the distance measure. This paper presents a simple data-dependent general-purpose dissimilarity measure called ‘\(m_p\)-dissimilarity’. Rather than relying on geometric distance, it measures the dissimilarity between two instances as a probability mass in a region that encloses the two instances in every dimension. It deems two instances in a sparse region to be more similar than two instances of equal inter-point geometric distance in a dense region. Our empirical results in k-NN classification and content-based multimedia information retrieval tasks show that the proposed \(m_p\)-dissimilarity measure produces better task-specific performance than existing widely used general-purpose distance measures such as \(\ell _p\)-norm and cosine distance across a wide range of moderate- to high-dimensional data sets with continuous only, discrete only, and mixed attributes.     

Wafer-level vacuum package of two-dimensional micro-scanner

Microsystem Technologies - We present wafer-level vacuum package of two-dimensional (2-D) micro-scanner based on glass-silicon anodic bonding. To form the sacrificial gap for evacuating air in the...