Comparison of the efficiency of the most effective heterogeneous nucleating agents for Poly(lactic acid)

We selected the thirteen most effective nucleating agents for Poly(lactic acid) (PLA) from the literature, and synthesized and compounded them with two different PLA grades: 3001D (1.4% D-lactide content) and 3100HP (0.5% D-lactide content, considered PLLA). We determined the crystallinity and crystallization of PLA with different nucleating agents in identical conditions (same nucleating agent content, same cooling rate) with the help of differential scanning calorimetry. We compared the efficiency of each nucleating agent and found that for both PLA grades, Zinc PhenylPhosphonate was the most effective. However, even when nucleated PLA was injection molded into a cold mold (25 °C), it still could not fully crystallize during cooling and the heat deflection temperature did not increase significantly. The maximum achieved crystallinity, in this case, was between 32.4 and 35.7%. On the contrary, when a 90 °C “hot mold” and in-mold crystallization together were applied, the specimens achieved full crystallization during the injection molding cycle (crystallinity was between 44.5 and 50.0%), and the heat deflection temperature increased to an average of 88.8 °C. We also examined the mechanical properties of the nucleated PLA and found that the usage of nucleating agents together with a hot mold improved tensile strength, tensile modulus, and Charpy impact strength but decreased elongation at break.

Comparison of Properties with Relevance for the Automotive Sector in Mechanically Recycled and Virgin Polypropylene

Polypropylene (PP) has a high recycling potential. However, the properties of mechanically recycled PP (R-PP) have not been fully compared to those of virgin PP (V-PP). Therefore, in this study, properties of R-PP and V-PP were compared using data from recyclers, virgin plastic suppliers, and the literature. The properties of recyclates could not be directly correlated either with the properties of the virgin polymers from which the recyclates were made or the recycling parameters. It was found that the MFR of R-PP was higher; MFR R-PP had a median value (m) of 11 g/10 min while MFR V-PP had a median value of 6.3 g/10 min (at 230 °C and with 2.16 kg). In terms of mechanical properties, in many cases R-PP exhibited stiffer and more brittle behavior, with a slightly higher Young’s modulus (ER-PP = 1400 and EV-PP = 1200 MPa), a reduced elongation at break (ɛbR-PP = 4 l.-% and ɛbV-PP = 83 l.-%), and notched charpy impact strength (NCISR-PP = 4.8 and NCISV-PP = 7.5 kJ/m2). However, the values for every property had a broad distribution. In addition to existing information from the literature, our research sheds fresh light on the variation of the characteristics of recycled polypropylenes presently on the market.

Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support

One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds.

Improving Mechanical Properties of PLA/Starch Blends Using Masterbatch Containing Vegetable Oil Based Active Ingredients

The aim of this research was to increase the compatibility between PLA and starch with vegetable oil-based additives. Based on tensile results, it can be stated, that Charpy impact strength could be improved for 70/30 and 60/40 blends in both unconditioned and conditioned cases, regardless of vegetable oil, while no advantageous change in impact strength was obtained with PLA-g-MA. Considering sample with the highest starch concentration (50%), the flexural modulus was improved by using sunflower oil-based additive, Charpy impact strength and elongation at break was increased using rapeseed oil-based additive in both conditioned and unconditioned cases. SEM images confirmed the improvement of compatibility between components.

Polymer Composites Based on Polycarbonate (PC) Applied to Additive Manufacturing Using Melted and Extruded Manufacturing (MEM) Technology

As part of the present work, polymer composites used in 3D printing technology, especially in Melted and Extruded Manufacturing (MEM) technology, were obtained. The influence of modified fillers such as alumina modified silica, quaternary ammonium bentonite, lignin/silicon dioxide hybrid filler and unmodified multiwalled carbon nanotubes on the properties of polycarbonate (PC) composites was investigated. In the first part of the work, the polymer and its composites containing 0.5–3 wt.% filler were used to obtain a filament using the proprietary technological line. The moldings for testing functional properties were obtained with the use of 3D printing and injection molding techniques. In the next part of the work, the rheological properties—mass flow rate (MFR) and mechanical properties—Rockwell hardness, Charpy impact strength and static tensile strength with Young’s modulus were examined. The structure of the obtained composites was also described and determined using scanning electron microscopy (SEM). The porosity, roughness and dimensional stability of samples obtained by 3D printing were also determined. On the other hand, the physicochemical properties were presented on the basis of the research results using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray scattering analysis (WAXS) and Fourier Transform infrared spectroscopy (FT-IR). Additionally, the electrical conductivity of the obtained composites was investigated. On the basis of the obtained results, it was found that both the amount and the type of filler significantly affected the functional properties of the composites tested in the study.

Hybrid Cellulose–Basalt Polypropylene Composites with Enhanced Compatibility: The Role of Coupling Agent

This study deals with the development and optimization of hybrid composites integrating microcrystalline cellulose and short basalt fibers in a polypropylene (PP) matrix to maximize the mechanical properties of resulting composites. To this aim, the effects of two different coupling agents, endowed with maleic anhydride (MA-g(grafted)-PP) and acrylic acid (AA-g-PP) functionalities, on the composite properties were investigated as a function of their amount. Tensile, flexural, impact and heat deflection temperature tests highlighted the lower reactivity and effectiveness of AA-g-PP, regardless of reinforcement type. Hybrid formulations with basalt/cellulose (15/15) and with 5 wt. % of MA-g-PP displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, and notched Charpy impact strength, of 45% and 284%, 97% and 263%, and 13%, in comparison with neat PP, respectively. At the same time, the thermo-mechanical stability was enhanced by 65% compared to neat PP. The results of this study, if compared with the ones available in the literature, reveal the ability of such a combination of reinforcements to provide materials suitable for automotive applications with environmental benefits.

Thermal Aging of Menzolit BMC 3100

This paper deals with the influence of thermal aging on physical properties of a composite material, Menzolit BMC 3100. First, we present a number of analysis, FTIR (infrared spectroscopy), DSC (differential scanning calorimetry), TMA (thermomechanical analysis), TGA (thermogravimetric analysis), and HDT (heat deflection temperature), to understand the material performance under heat, and then, we carry out a test of toughness and strength using Charpy impact strength and Brinell hardness. Finally, we present optical surface analysis of the material under investigation by carrying out aging analysis at increments from room temperature up to 300°C. It was observed that above 200°C, the material begins to degrade at the surface, especially its organic component, polyester resin. This type of degradation has a negative impact on a variety of its physical properties. Exposure to temperatures above 200°C reduces the material’s hardness, toughness, and shape stability, likewise, material degradation was found to increase with higher thermal loads almost linearly for all the observed properties.

Mechanical and Tribological Properties of A7050 Hybrid Composite Reinforced with Nano Al2O3/Micro ZrO2 Particles by Stir Casting Method

The composite plays an important role in the new generation of engineering material with better tribological and mechanical properties. In this paper, the hybrid composites of A7050/Al2O3/ZrO2 with different wt. % of reinforcement materials (0.5, 1, 1.5wt. % ZrO2, and 1wt. % Al2O3 constant for all composites) were fabricated by stir casting method. From the results, it was observed that the good texture in microstructure without defect with an addition of constant 1wt% Al2O3 and varying 0.5, 1and 1.5 wt% ZrO2. The Hardness of hybrid composites is increased by 27% with addition of 1wt % of Al2O3 and 1.5 wt% ZrO2 compare to base alloy. Charpy impact strength decreased with the addition of Al2O3 and ZrO2 ceramic particle in all the composites. From the dry wear studies, the composite with 1wt% Al2O3 and 1wt% ZrO2 was observed with minimum wear loss and low coefficient of friction.

Effect of Ethylene Vinyl Axetate (EVA) on the Mechanical Properties of Low-Density Polyethylene/EVA Blends

The extensive range of fillers used nowadays indicated the major significance of filler in the plastic industry. Although their original purpose was to lower the cost of the molding compounds; prime importance is now attached to selective modification of the properties of a specific plastic. In this study, the examples of LDPE/EVA blends, were put into 0, 3, 6, 9, 12 and 15 wt.% of EVA. The tensile strength, bending strength and impact strength of samples were determined according to ASTM D638, ISO 178 and ISO 179. Results showed that when increasing ratio of EVA in LDPE/ EVA blends, tensile strength decreased from 10.9 MPa to 8.6 MPa. Bending strength decreased linearly from 9.63 MPa to 5.46 MPa. Charpy impact strength decreased from 47.5 kJ/m2 to 6.3 kJ/m2. On the contrary, elongation in 100% LDPE is 78.3%; with the appearance of EVA, elongation of the LDPE/ EVA blends increased upto 109.1%. In addition, SEM micrographs indicated that, it was more crystal-clear when the EVA content is less; in the highest EVA content with 15%, it can be seen that the specimen after pressing is slightly opaque and darker than the orthers. From that showed the addition of EVA to the polymer leads the tensile strength, bending strength were not affect much, impact strength decreased but elongation experienced an increase.