Jacek Andrzejewski

Effect of heterogeneous nucleation on isotactic polypropylene-polyoxymethylene blends properties and miscibility

This paper presents a study of the effect of heterogeneous nucleation on isotactic polypropylene-polyoxymethylene (iPP-POM) blends properties and miscibility. Polyoxymethylene have been blended with polypropylene matrix in three different amounts: 25, 50, and 75 wt% with and without sorbitol based nucleating agent. Thermal and mechanical properties of blends have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanic thermal analysis (DMTA), static tensile test as well as rheological analysis. The structure of the blends was investigated using Scanning Electron Microscopy (SEM) and polarized optical microscopy (PM). Rheological analysis confirmed that the iPP-POM blends are partially miscible in a molten state.

Development and Characterization of the Injection-Molded Polymer Composites Made from Bicomponent Fibers

The results of this study are related to the implementation of the concept of self-reinforced composites. The input materials in preparation process were the bicomponent fibers. The studies were carried out on three types of fibers, HDPE/PP, cPP/PP, LPET/PET. In each case, the matrix material was a low melting polymer, and the core was made of a higher melting point polymer. The research was conducted for the materials shaped by an injection-molding technique. The analyses confirmed the two-component structure. Properties of the resulting composites confirmed the applicability of bicomponent fibers in the preparation of self-reinforced composites. GRAPHICAL ABSTRACT

Microwave Enhanced Foaming of Carbon Black Filled Polypropylene

Microwave heating has a number of advantages in comparison to the conventional method due to the ability to heat a part of composite material directly through specific interaction of electromagnetic radiation with selected types of materials. Most thermoplastics are relatively transparent for microwave irradiation and they do not absorb microwaves to a sufficient extent to be heated. Enhanced microwave heating can result from the use of fillers such as carbon black. Different types of carbon black were used to increase the susceptibility of polypropylene (PP) for microwave processing. Measurements were carried out on PP filled with carbon black of different grades. Relative temperature rises and heat efficiency versus the content of carbon black in PP were analyzed. The temperature changes of different mass samples of these materials under microwave irradiation with various power were also investigated. Moreover, polypropylene composites with additive of chemical blowing agents were blown under microwave irradiation and the influence of foaming conditions on cell structure and selected properties of porous products were estimated.

Application of waste bulk moulded composite (BMC) as a filler for isotactic polypropylene composites.

Graphical abstract

The influence of processing conditions on the mechanical properties and structure of poly(ethylene terephthalate) self-reinforced composites

The self-reinforced composites based on poly(ethylene terephthalate) (PET) are relatively new materials, competitive to composites based on polymers from the group of polyolefins. The use of PET as a base material should be another step forward for this technology, taking into account the properties, price, and the recycling possibility of proposed composites. In this research work, the main subject was to assess the impact of processing conditions on the final properties of the PET self-reinforced composites (srPET). The examined samples were prepared by hot-compaction technique under variable thermal conditions. The input material was composed of PET resin and low-melting copolymer (LPET). The high tenacity PET fibers were used as reinforcement for PET copolymer matrix. Initially both materials were in the form of continuous fiber; they were woven into a hybrid yarn wherein the proportion of PET and LPET fibers was 50/50. The properties of this hybrid yarn were investigated by differential scanning calorimetry (DSC) analysis, where the hot-compaction process conditions were simulated. Composite samples were investigated using the dynamic mechanical analysis (DMA) and static tension tests. The structure of the composite was observed using the optical microscope. The obtained mechanical properties of such a composite are not comparable to commercially made composite sheets, in which overall properties are mostly higher.

Thermal Properties of Polymer-Metal Composites

The objectives in this paper are to investigate the effects of the filler content and size on the effective thermal conductivity of the PE/Al; PE/Cu, PE/Fe and PE/bronze composites. The polymer matrix of the polymer/metal composites was two types of polyethylenes: LDPE and HDPE (from Basell Orlen). The following polymer/metal composites obtained by extrusion process containing: 10% by weight of Al, Cu, Fe and bronze powder in LDPE matrix and composites containing 5, 10, 15 and 20% by weight of Al flakes in HDPE polymer were prepared and tested. Adding in the extrusion process 10% by weight of bronze powder into the polyethylene, increased more than five times the thermal diffusivity of produced composite. Use as a filler 20% wt. of aluminum flake increases it by more than twice. The study showed the ability to produce polyethylene matrix composites with the addition of metal powder fillers (Al, Cu, Fe, and bronze). Analyzing the measuring results of thermal diffusivity coefficient by Angstrom method, it can be concluded that with the appropriate filler content, the particles are located close enough to each other to form a continuous conductive path, then the thermal diffusivity of the composite increases significantly.Copyright

Improving the Impact Strength and Heat Resistance of 3D Printed Models: Structure, Property, and Processing Correlationships during Fused Deposition Modeling (FDM) of Poly(Lactic Acid)

A fused deposition modeling method was used in this research to investigate the possibility of improving the mechanical properties of poly(lactic acid) by changing the thermal conditions of the printing process. Sample models were prepared while varying a wide range of printing parameters, including bed temperature, melt temperature, and raster angle. Certain samples were also thermally treated by annealing. The prepared materials were subjected to a detailed thermomechanical analysis (differential scanning calorimetry, dynamic mechanical analysis, heat deflection temperature (HDT)), which allowed the formulation of several conclusions. For all prepared samples, the key changes in mechanical properties are related to the content of the poly(lactic acid) crystalline phase, which led to superior properties in annealed samples. The results also indicate the highly beneficial effect of increased bed temperature, where the best results were obtained for the samples printed at 105 °C. Compared to the reference samples printed at a bed temperature of 60 °C, these samples showed the impact strength increased by 80% (from 35 to 63 J/m), HDT increased by 20 °C (from 55 to 75 °C), and also a significant increase in strength and modulus. Scanning electron microscopy observations confirmed the increased level of diffusion between the individual layers of the printed filament.