The Influence of Mixing Methods of Epoxy Composition Ingredients on Selected Mechanical Properties of Modified Epoxy Construction Materials

The proper process of preparing an adhesive composition has a significant impact on the degree of dispersion of the composition ingredients in the matrix, as well as on the degree of aeration of the resulting composition, which in turn directly affects the strength and functional properties of the obtained adhesive compositions. The paper presents the results of tensile strength tests and SEM microphotographs of the adhesive composition of Epidian 57 epoxy resin with Z-1 curing agent, which was modified using three fillers NanoBent ZR2 montmorillonite, CaCO₃ calcium carbonate and CWZ-22 active carbon. For comparison purposes, samples made of unmodified composition were also tested. The compositions were prepared with the use of six mixing methods, with variable parameters such as type of mixer arm, deaeration and epoxy resin temperature. Then, three mixing speeds were applied: 460, 1170 and 2500 rpm. The analyses of the obtained results showed that the most effective tensile results were obtained in the case of mixing with the use of a dispersing disc mixer with preliminary heating of the epoxy resin to 50 °C and deaeration of the composition during mixing. The highest tensile strength of adhesive compositions was obtained at the highest mixing speed; however, the best repeatability of the results was observed at 1170 rpm mixing speed. Based on a comparison test of average values, it was observed that, in case of modified compositions, the values of average tensile strength obtained at mixing speeds at 1170 and 2500 rpm do not differ significantly with the assumed level of significance α = 0.05.

The Impact of the Acidic Environment on the Mechanical Properties of Epoxy Compounds in Different Conditions

The aim of this work was to determine the impact of the acidic environment on the mechanical properties of two epoxy compounds in different conditions. The samples were made from the epoxy compounds composed of the epoxy resin (based on Bisphenol A), triethylenetetramine curing agent (unmodified compound), and calcium carbonate (CaCO₃) (modified compound). The epoxy compound samples were seasoned for the following period of time (i.e., one week, one month, and three months). The environment was tap water and the acidic environment had three different concentrations of acetic acid (3%, 6%, and 9%). Strength tests of the epoxy compound samples were carried out in accordance with the ISO 604 standard. In the case of the modified composition, it is noted that the samples immersed in tap water were characterized by a higher strength than in acidic environments. A similar tendency was observed for unmodified compositions, although the differences were smaller than for the modified compositions. It was also noticed that the increase in the pH of the acidic solution in many analyzed cases contributed to the decrease in mechanical properties, although the immersion time in the acidic solution is important.

Aging Effects of Aqueous Environment on Mechanical Properties of Calcium Carbonate-Modified Epoxy Resin

The purpose of this study was to assess the effects of different aqueous environments (i.e., demineralised, distilled and spring water) on the mechanical properties of a cold-cured bisphenolic epoxy resin modified with the addition of calcium carbonate filler, typically employed as structural adhesive. The parameters selected for the analysis have been; the kind of curing agent employed to cure the epoxy resin at ambient temperature (i.e., Mannich base and triethylenetetramine); the load of calcium carbonate added to liquid epoxy (i.e., from 1 to 3 g per 100 g of resin) and; the duration of the exposure to the different aging conditions (i.e., from 1 to 10 months). Cylindrical specimens of calcium carbonate-modified epoxy systems were tested in compression mode, before and after each of the aging regimes. The effect of the selected curing agents is very small, and they are both suitable for a cure at ambient temperature, on the unfilled epoxy on compressive maximum strength and strain at break; the choice of the hardener affects instead the compressive modulus. The CaCO3 amount was demonstrated to have a significant effect on the mechanical characteristics of un-aged epoxy systems, leading to growth in compressive modulus and maximum strength with reductions in strain at break. Generally speaking, the aging time noticeably affects the compressive properties of calcium carbonate-modified epoxies while almost negligible is the kind of water employed in each exposure regime. Notwithstanding the adverse effects of an aqueous environment on compressive mechanical properties of CaCO₃-filled epoxies, these systems keep compressive modulus and maximum strength greater than, and close to, respectively, the same characteristics measured on unaged unfilled control epoxies, demonstrating the positive effect of the addition of this kind of filler to epoxy-based structural adhesives, especially with the addition of 2 and 3 g of CaCO₃ per 100 g resin. The results obtained in this study demonstrated that it is possible to contrast the detrimental effects observed in cold-cured epoxy-based structural adhesives due to their aging in water upon the addition of limited amounts (particularly at 2 and 3 g per 100 g resin) of a cheap CaCO₃ filler.

Superiority of Cellulose Non-Solvent Chemical Modification over Solvent-Involving Treatment: Application in Polymer Composite (part II)

The following article debates on the properties of cellulose-filled ethylene-norbornene copolymer (EN) composites. Natural fibers employed in this study have been modified via two different approaches: solvent-involving (S) and newly developed non-solvent (NS). The second type of the treatment is fully eco-friendly and was carried out in the planetary mill without incorporation of any additional, waste-generating substances. Composite samples have been investigated with the use of spectroscopic methods (FT-IR), differential scanning calorimetry (DSC), static mechanical analysis, and surface-free energy measurements. It has been proved that the possible filler-polymer matrix interaction changes may occur due to the performed modifications. The highest reinforcement was evidenced for the composite sample filled with cellulose treated via a NS approach—TS = (34 ± 2) MPa, Eb = (380 ± 20)%. Additionally, a surface free energy polar part exhibited a significant increase for the same type of modification. Consequently, this could indicate easier wetting of the material which may contribute to the degradation process enhancement. Successfully developed cellulose-filled ethylene-norbornene copolymer composite compromises the rules of green chemistry and sustainable development by taking an advantage of renewable natural resources. This bio-inspired material may become an eco-friendly alternative for commonly used polymer blends.

Thermal Behavior of Green Cellulose-Filled Thermoplastic Elastomer Polymer Blends

A recently developed cellulose hybrid chemical treatment consists of two steps: solvent exchange (with ethanol or hexane) and chemical grafting of maleic anhydride (MA) on the surface of fibers. It induces a significant decrease in cellulose moisture content and causes some changes in the thermal resistance of analyzed blend samples, as well as surface properties. The thermal characteristics of ethylene-norbornene copolymer (TOPAS) blends filled with hybrid chemically modified cellulose fibers (UFC100) have been widely described on the basis of differential scanning calorimetry and thermogravimetric analysis. Higher thermal stability is observed for the materials filled with the fibers which were dried before any of the treatments carried out. Dried cellulose filled samples start to degrade at approximately 330 °C while undried UFC100 specimens begin to degrade around 320 °C. Interestingly, the most elevated thermal resistance was detected for samples filled with cellulose altered only with solvents (both ethanol and hexane). In order to support the supposed thermal resistance trends of prepared blend materials, apparent activation energies assigned to cellulose degradation (E_A1) and polymer matrix decomposition (E_A2) have been calculated and presented in the article. It may be evidenced that apparent activation energies assigned to the first decomposition step are higher in case of the systems filled with UFC100 dried prior to the modification process. Moreover, the results have been enriched using surface free energy analysis of the polymer blends. The surface free energy polar part (Ep) raises considering samples filled with not dried UFC100. On the other hand, when cellulose fibers are dried prior to the modification process, then the blend sample’s dispersive part of surface free energy is increased with respect to that containing unmodified fiber. As polymer blend Ep exhibits higher values reflecting enhanced material degradation potential, the cellulose fibers employment leads to more eco-friendly production and responsible waste management. This is in accordance with the rules of sustainable development.

Mechanical, Thermal and Rheological Properties of Polyethylene-Based Composites Filled with Micrometric Aluminum Powder

Investigations related to polymer/metal composites are often limited to the analysis of the electrical and thermal conductivity of the materials. The presented study aims to analyze the impact of aluminum (Al) filler content (from 1 to 20 wt%) on the rarely investigated properties of composites based on the high-density polyethylene (HDPE) matrix. The crystalline structure, rheological (melt flow index and oscillatory rheometry), thermal (differential scanning calorimetry), as well as static (tensile tests, hardness, rebound resilience) and dynamic (dynamical mechanical analysis) mechanical properties of composites were investigated. The incorporation of 1 and 2 wt% of aluminum filler resulted in small enhancements of mechanical properties, while loadings of 5 and 10 wt% provided materials with a similar performance to neat HDPE. Such results were supported by the lack of disturbances in the rheological behavior of composites. The presented results indicate that a significant content of aluminum filler may be introduced into the HDPE matrix without additional pre-treatment and does not cause the deterioration of composites’ performance, which should be considered beneficial when engineering PE/metal composites.

Seasoning Polymethyl Methacrylate (PMMA) Bone Cements with Incorrect Mix Ratio

Cemented joint prostheses are widely used in orthopaedic surgery; however, implants/bone bonds are known to be susceptible to aseptic loosening, particularly in the case of long-term performance. The exact mechanism of this failure is under constant examination. One of the critical factors to the final mechanical functionality of bone cement can be an incorrect mix ratio of a two-component material (powdered polymer and liquid monomer). It can result in the deterioration of the final mechanical strength properties. The paper presents the results from an experimental study on the effects of the deviation from the correct mix ratio on the moisture uptake and the compression strength of cement depending on the seasoning time in Ringer's solution. The results were subjected to statistical analysis and a mathematical model was developed.

The Impact of the Seasoning Conditions on Mechanical Properties of Modified and Unmodified Epoxy Adhesive Compounds

The aim of this study was to analyse the impact of the adhesive samples seasoning conditions (temperature and time) on selected mechanical properties of four epoxy adhesive compounds (two unmodified and two modified ones). The samples were made of Epidian 53 epoxy resin mixed with the two different amine curing agents in appropriate stoichiometric proportions. A filler in the form of calcium carbonate (CaCO₃) powder was used as a modifier. The adhesive compound samples were cured for seven days. Six seasoning variants were used. Four of them were related with the seasoning time at ambient temperature of 24 ± 2 °C for: one month, two months, five months and eight months, respectively. Two other variants were related with seasoning at negative temperature (−10 ± 2 °C) for one month. The last variant (F) also included seasoning at ambient temperature (24 ± 2 °C) for five months right after seasoning in negative temperature. Cured and cylinder-shaped adhesive compound samples were subjected to compressive strength tests (according to the ISO 604 standard). The strength tests were performed using a Zwick/Roell Z150 testing machine. Based on the tests, it was observed that both temperature and time of seasoning influenced the adhesive’s mechanical properties. In the perspective of eight months, these changes were relatively minor for the samples seasoned at ambient temperature. The adhesive samples prepared for the tests were especially sensitive to negative temperature.