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The present paper considers the use of the results of the evaluations carried out by applying the `Six Sigma` statistical method to improve the vulcanization times of elastomeric composites on the external manufacturing cycle of several size types of car tires. This statistical approach aims to verify the distribution of the measured values of the external vulcanization times between the normal specification limits to optimize them and improve the performance, efficiency, and quality of the automotive tire vulcanization processes. Through the analysis carried out, the operations that caused delays and defects were identified, a program of corrective measures was carried out and after its execution, the fulfillment of the purpose was verified, namely the optimization of external vulcanization times and reducing the number of faulty tires. The new measured values of the vulcanization times were within the normal limits of the imposed specifications (LSS = 2.5). This situation corresponds to achieving a maximum level of performance and represents the successful completion of the quality improvement project.

Melt processing poly(L-lactide) (PLLA) with a nucleating agent has been thought to be one of the most effective route to enhance PLLA`s crystallization and heat resistance. In the current work, a newly-developed organic nucleating agent named N, N`-bis(2-picolinyl) 1, 4-naphthalenedicarboxylic acid dihydrazide (NCAPH) was synthesized to investigate its effects on PLLA’s crystallization and melting behaviors. It is proved that NCAPH as an organic crystallization nucleating agent could provide large number of crystallization nucleation sites to improve PLLA’s crystallization, as observed from DSC and POM measurements. The result from melt-crystallization processes further showed that the final melting temperature and cooling rate were two important factors for affecting PLLA’s melt-crystallization behaviors in cooling, and the theoretical calculation result of frontier orbital energy indicated there existed probable intermolecular interaction between N-H of NCAPH and C=O of PLLA, which was proposed as nucleation mechanism of NCAPH for promoting PLLA’s crystallization. The melting behaviors of PLLA/NCAPH after non-isothermal crystallization or isothermal crystallization further confirmed the positive effects of NCAPH and NCAPH’s loading for the crystallization of PLLA, meantime, the melting behaviors depended on the heating rate, crystallization temperature, crystallization time, etc.

This study evaluated surface durability use of manufacture 3D printed gears. Polymer gears were 3D printed using PLA, Tough-PLA, and TPU materials, Through different combinations of materials,three gears of the same size were manufactured: the PLA gear, the PLA plus TUP gear and the Tought PLA plus TPU gear. The surface wear test of the 3d-printed gears were on a self-designed test bench. The differences in mechanical performance between the polymer filaments were attributed to differences in crystallinity and the uniqueness of the fused deposition modeling (FDM) process, but by combining two materials with different features, it is possible to change the mechanical properties of 3D printed gears.In this study , from the changes of torque data during the whole experiment also showed the difference of transmission efficiency of three different gears.Scanning electron microscopy (SEM) revealed the different surface wear of three different gears under the same test conditions. During the gear surface wear test, a thermal camera was used to recorded the surface temperature changes of the gears, and SEM was used to analyze the wear of the gear surface. The test results showed Tough-PLA Plus TPU gear showed the best wear performance among the three different 3D printing gears tested.

This study aimed to investigate the water sorption levels of 3 different condensable bulk fill composites, two flowable bulk fill composites, two microhybrid composites, one nanofilled composite, and one nanohybrid composite material polymerized with the same beam device on the 14th and 30th days.We evaluated nine different composite materials. The materials were prepared as cylindrical blocks (n=7) with a diameter of 7 mm and a thickness of 2 mm and polymerized. Each sample was kept in distilled water for specified times and measured by the ISO 4049 method.We used The Kruskal-Wallis test to compare more than two independent groups where numerical variables had no normal distribution. The Dwass-Steel-Critchlow-Fligner test evaluated differences between the groups if the non-parametric tests were applied. We used The Wilcoxon test to compare the numerical variables without normal distribution (water sorption values in the 14th and 30th-day measurements for each cement material).For water sorption, there was no statistically significant difference between the water sorption values of the resin composite materials on the 14th and 30th days. No statistically significant difference was found in comparing water sorption values between the 14th and 30th measurements for each resin composite material. There is a need for more extended studies by keeping the conditions constant for the evaluated composites and for bulk fill composites to be evaluated with 4mm samples.

The flexural response of externally strengthened RC beams with GFRP and HFRP (hybrid FRP) sheets under monotonic and cyclic loading conditions are investigated. Fourteen beams in two series (Series1and 2) were cast for this study. Each series consisted of seven beams. A total number of 14 beams were cast, out of which 2 beams considered as control specimen. The 12 beams were externally strengthened with GFRP sheets (4 beams) and HFRP sheets (8 beams). Series 1 and Series 2 beams were tested for two-point static and cyclic loads. The experimental for ultimate strength, deformation, stiffness, ductility, energy absorption and modes of failures are conversed for all the tested beams. The peak load for the RC beams tested specimens under static loads were computed using ACI 440.2R-08 guidelines. An optimum increase of 171.43 % in ultimate load carrying capacity was found for the beam strengthened with HFRP sheets than the control beam. Also, the predicted ultimate loads exhibited the good convergence with the test results.

In this research some composite materials built in sandwich type style are studied. The lower and upper layers, that reinforce the samples, are made from poplar strips. The core is made from crushed corn cob and the adhesion of all parts (layers and core) is made by using hybrid resins based on a combination from dammar resin and the synthetic acrylic one (with its hardener). The static and dynamic mechanical behaviour by testing the samples to tensile and bending were studied. Two types of hybrid resins were used: one abbreviated as type B with the percentage of 60% dammar and 40% acrylic resin with hardener and one abbreviated as type C with the percentage of 65% dammar and 35% acrylic resin with hardener. A general conclusion from this study it was: the mechanical properties decrase with the dammar percentage increase. This fact can be explained by the decreased mechanical properties of the natural dammar resin compared to the synthetic acylic on

The structure of polyurethane and the physico-chemical properties of its components are considered. The most promising modifiers have been selected: TiO2, CaCO3. The features of the preparation of the studied polyurethane mixture, its composition, manufacturing technology and equipment are described in detail. The geometric properties, manufacturing processes and testing methods of samples are presented. The graphical dependencies of the influence of the parameters of sample preparation on their mechanical properties such as hardness, tensile stress at break, Jung`s modulus are given. The rational parameters of the technology for the production of samples modified with fillers to give them stable mechanical properties have been set. The maximum proportions of these fillers in polyurethane rubber are limited to 30-35%. It is proved that the addition of TiО2 and CaCО3 to the composition of polyurethane rubbers gives them special properties that allow them to expand the range of their industrial usage.

In this paper, the authors propose to carry out a case study, on a visual part made of thermoplastic material from the automotive industry. Using the most up-to-date CAE systems, we will try to highlight the main appearance problems in long parts, namely the appearance of weld lines at the meeting of the flow fronts. The part will be processed using sequential, as well as non-sequential injection systems, respectively, in order to highlight the difference between the two, respectively to compare these two tests with the results of rheological simulation (CAE).

Bromelain, a natural substance sourced from pineapples, was found effective in various colds, in preventing heart attack and respectively in excess weight. On the other hand, it is well-known that pineapples juice increases the gastric acidity and respectively the people with hemophilia, internal bleeding must also be very careful in consuming this fruit. The objectives of this study were to obtain and to characterize a drug delivery system used for the transmembrane transfer of bromelain. The samples based on polyurethane matrices with and respectively without bromelain were synthesized and characterized by measurements of pH, encapsulation efficacy, cumulative drug release in a degradative media and in simulated gastric acid, electron microscopy and by modern techniques such as Zetasizer, cytotoxicity assay, and various non-invasive skin irritation assessment. The results indicate the obtaining of polyurethane matrices with mean sizes between 322-342 nm and neutral pH, that have a medium stability against the clusters formation tendency and a medium drug release rate. The non-irritative potential and the results on their cytotoxicity are important evidences that can be used for the further clinical trials of the polyurethane carriers.

Lignin fiber/epoxy resin compositeused for energy absorbing was prepared by atmospheric stirring method. Quasi-static compressive mechanics tests were implemented by using the electronic universal mechanics tester (WDW-100KN) under ambient conditions to analyze the compressing behavior of the matrix material and composite at the strain rate of 10-2s-1 .Scanning electron microscope (SEM) was used to observe the microstructure of the composite after quasi-static compression damage. The results showed that when the ratio of epoxy resin and curing agent was 3:1, the internal structure of the matrix material was more uniform with smoother cross-section, which represented better mechanical properties. It was found that the addition of lignin fiber changed the compression characteristics of the matrix material, resulting in a strengthening stage appeared. At the same time, when the lignin fiber content was 2% or 3%, the composite could absorb more impact energy and delay crack generation, which met the performance requirement of energy absorbing materials.