Polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties

ABSTRACT The usage of natural fibers on the composites development has grown rapidly in the recent years due to the fibers plentiful availability, renewable source, low density and biodegradability. However, there are some drawbacks, for instance, the fiber dispersion on a polyolefin matrix. In this work, the influence of processing speed on the mechanical and dynamic mechanical properties of polystyrene (PS) filled with cellulose fiber composites was investigated. The composites were processed on a twin-screw co-rotating extruder, using screw speeds of 200 rpm, 400 rpm and 600 rpm. The dynamic mechanical properties and the mechanical properties were investigated as a function of fiber content. The composites processed on a screw speed of 400 rpm had presented an increase on flexural and impact strength, compared to the composites processed at 200 rpm. The flexural and storage modulus had increased when increasing the fiber content, as well as increasing the processing speed. The greater fiber dispersion obtained at a screw speed of 400 rpm hinders the agglomeration arrangement and distributes the fibers more equally on the matrix. The increase on processing speed probably generates a fiber size reduction, increasing the fiber superficial area and generating a greater contact with the matrix as well. Therefore, the efforts transference of matrix to fibers is improved, originating an increase on the evaluated properties

Performance of short noil hemp fibre polypropylene composites

In this study, short noil hemp fibre composite with varying fibre content were fabricated using intermixer and injection moulding machines. The maleic anhydride grafted polypropylene (MAPP) and maleic anhydride grafted Poly (ethylene octane) (MAPOE) were used as coupling agents for modifying the matrices. Tensile, dynamic mechanical and microstructural characterizations were performed by tensile strength testing, scanning electron microscope (SEM) and X-ray microtomography. The composites revealed better temperature resistance at higher fibre content. However, the increase in storage modulus and tensile strength was negligible in composites reinforced with more than 40 wt.% hemp fibres; due to the agglomeration of the fibres. The results also indicated that the tensile strength of the noil hemp fibre reinforced composites without a coupling agent was below the tensile strength of pure polypropylene. However, the addition of coupling agents improved the tensile strength of the noil hemp fibre reinforced polypropylene composites by increasing the reinforcing effects of the fibres due to the enhanced fibre/matrix interfacial adhesion. This was also confirmed by dynamic mechanical analysis. X-ray microtomography study concluded that coupling agent addition can also reduce the fibre breakage due to the better fibre dispersion in the polypropylene

Unfolding the neutron spectrum of a NE213 scintillator using artificial neural networks

Artificial neural networks technology has been applied to unfold the neutron spectra from the pulse height distribution measured with NE213 liquid scintillator. Here, both the single and multi-layer perceptron neural network models have been implemented to unfold the neutron spectrum from an Am-Be neutron source. The activation function and the connectivity of the neurons have been investigated and the results have been analyzed in terms of the network's performance. The simulation results show that the neural network that utilizes the Satlins transfer function has the best performance. In addition, omitting the bias connection of the neurons improve the performance of the network. Also, the SCINFUL code is used for generating the response functions in the training phase of the process. Finally, the results of the neural network simulation have been compared with those of the FORIST unfolding code for both Am-Be and Cf neutron sources. The results of neural network are in good agreement with FORIST code. Crow

3D X-ray microtomography study on fibre breakage in noil hemp fibre reinforced polypropylene composites

X-ray microtomography, image processing and Weibull statistical methods were used to characterize the length and width distributions of noil hemp fibres before and after composite fabrication. X-ray microtomography provided direct observations and accurate measurements of length and width of noil hemp fibres within the hemp–polypropylene composite matrix. The effects of the weight content of the noil hemp fibre and the addition of compatibilizer on the fibre breakage and tensile strength of the composites were studied. The results indicated that the tensile strength of the noil hemp fibre reinforced composites without the coupling agent was lower than that of pure polypropylene. Fibre–fibre interaction mechanism indicated that high hemp content caused more fibre breakage. The addition of maleic anhydride grafted polypropylene (MAPP) coupling agent improved the tensile strength of the composites by the enhanced fibre/matrix interfacial adhesion. The addition of MAPP also reduced the fibre breakage due to the better dispersion of fibres

T-Helper Cytokine Patterns and Related Antibodies in Patients with Gestational Diabetes Mellitus

Background: Diabetes mellitus (DM) is a group of metabolic disorders such as DM I, DM II, secondary causes of DM and gestational diabetes mellitus characterized by hyperglycemic phonotype. The etiology of gestational diabetes mellitus is unknown. Recent studies address the chronic activity of immune system against infections (not autoimmunity) as an important cause of gestational diabetes mellitus. This study aimed to compare T-helper cells 1 and 2 cytokines and associated antibodies in patients with gestational diabetes mellitus and normal pregnant women. Methods: This cross-sectional study was performed on 45 female patients with GDM and 45 healthy pregnant women in Bandar Abbas, Iran, from 2008- 2009. The exclusion criteria were presence of any infectious diseases or autoimmune disorders such as SLE or RA. Present and past medical histories were taken from the participants thorough physical examination. Blood samples (10 mL) were drawn and sent to laboratory for measuring serum IgE, IgG1, IgG2, IgG3, IgG4, interleukin-10 (IL-10), interleukin-12 (IL-12), transforming growth factor-beta (TGF1), and interferon-gamma (IFN) measurements. T-test and Kolmogorov-Smirnov test were used for data analysis. Results: The mean age of the patients with GDM and healthy pregnant women was 32.5 and 27.9 yrs, respectively. T-helper 1 and 2 associated antibodies and cytokines had no significant differences between the case and control groups. Conclusion: The changes in T-helper 1 and 2 associated antibodies and cytokines are not associated with gestational diabetes mellitus and could not be considered as a predictor for gestational diabetes mellitus

T-helper cytokine patterns and related antibodies in patients with gestational diabetes mellitus

Background: Diabetes mellitus (DM) is a group of metabolic disorders such as DM I, DM II, secondary causes of DM and gestational diabetes mellitus characterized by hyperglycemic phonotype. The etiology of gestational diabetes mellitus is unknown. Recent studies address the chronic activity of immune system against infections (not autoimmunity) as an important cause of gestational diabetes mellitus. This study aimed to compare T-helper cells 1 and 2 cytokines and associated antibodies in patients with gestational diabetes mellitus and normal pregnant women. Methods: This cross-sectional study was performed on 45 female patients with GDM and 45 healthy pregnant women in Bandar Abbas, Iran, from 2008- 2009. The exclusion criteria were presence of any infectious diseases or autoimmune disorders such as SLE or RA. Present and past medical histories were taken from the participants thorough physical examination. Blood samples (10 mL) were drawn and sent to laboratory for measuring serum IgE, IgG1, IgG2, IgG3, IgG4, interleukin-10 (IL-10), interleukin-12 (IL-12), transforming growth factor-beta (TGF1), and interferon-gamma (IFN) measurements. T-test and Kolmogorov-Smirnov test were used for data analysis. Results: The mean age of the patients with GDM and healthy pregnant women was 32.5 and 27.9 yrs, respectively. T-helper 1 and 2 associated antibodies and cytokines had no significant differences between the case and control groups. Conclusion: The changes in T-helper 1 and 2 associated antibodies and cytokines are not associated with gestational diabetes mellitus and could not be considered as a predictor for gestational diabetes mellitus

Design and Optimization of the Thermo-Mechanical Behavior in Glass Reinforced Polyamide 6 For Automotive Application

In this work a rational approach, such as Design of Experiments, has been used to design E-glass and S2-glass reinforced polyamide 6 composites. The models, derived by the multivariate analysis of the experimental tests, allowed deriving response surfaces in which the effect of reinforce’s composi- tion, content and shape on the thermo-mechanical have been related to com- posite’s behavior during cycling loads and high temperatures. These composites find application in the developing of a sensor used in the automotive engine compartment where thermal and vibration effects must be taken in account to avoid premature failure. Thirty experiments were planned by Design of Exper- iments and analyzed through Analysis Of Variance to correlate reinforce’s properties to coefficient of thermal expansion, Young Modulus and damping over temperature/frequency variation. Statically reliable models were calculated to obtain a numerical estimation of the overall quadratic and cubic interactions among reinforce’s properties, explaining how matrix/reinforce interaction affects composite’s properties. Nevertheless, the employment of S2-glass led to restrained coefficient of thermal expansion of the composites, reinforce’s content of E-glass fibers over 30wt% is in a better agreement with the composite’s overall requirements for this tailored application, due to restrained mechanical damping

Vibration damping characteristics of short hemp fibre thermoplastic composites

In this project, free vibration testing and dynamic mechanical analysis methods were used to study the damping properties of noil hemp fibre-reinforced polypropylene composites with varying fibre contents (0 to 60 wt%) and compatibilizers (maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyethylene octane) under applied frequencies of 1 to 200 Hz. The storage modulus of the composites was increased by the increase in hemp fibre content. However, the maximum damping ratio was obtained from the composite with 30 wt% noil hemp fibre. The addition of coupling agents reduced the damping capacity of all composites. However, 30 wt% noil hemp fibre-reinforced polypropylene coupled with 2.5 wt% anhydride-grafted poly ethylene octane revealed the highest damping ratio among coupled composites. Damping properties of the composites were relatively constant over the frequency range, except at frequencies which the material–instrument system began to resonate and peaks were observed in the curves