Effect of Hybrid Filler, Carbon Black-Lignocellulose, on Fire Hazard Reduction, including PAHs and PCDDs/Fs of Natural Rubber Composites.

The smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of lignocellulose filler, we noticeably reduced the fire hazard caused by elastomeric composites. The lignocellulose filler reduced the parameters associated with the flammability of the tested composites, decreased the smoke emission, and limited the toxicity of gaseous decomposition products expressed as a toximetric indicator and the sum of PAHs and PCDDs/Fs. The natural filler also reduced emission of gases that constitute the basis for determination of the value of the toximetric indicator WLC50SM. The flammability and optical density of the smoke were determined in accordance with the applicable European standards, with the use of a cone calorimeter and a chamber for smoke optical density tests. PCDD/F and PAH were determined using the GCMS-MS technique. The toximetric indicator was determined using the FB-FTIR method (fluidised bed reactor and the infrared spectrum analysis).

Antioxidant and Anti-Aging Activity of Freeze-Dried Alcohol-Water Extracts from Common Nettle (Urtica dioica L.) and Peppermint (Mentha piperita L.) in Elastomer Vulcanizates.

The research article aimed to examine the antioxidant nature of freeze-dried extracts from Urtica dioica L. and Mentha piperita L. and to present a deep characterization of their influence on the properties of natural rubber-based vulcanizates before and after simulated aging processes. Natural extracts were prepared in three solvent systems at selected volume ratios: water (100), methanol-water (50/50), ethanol-water (50/50), which were further lyophilized and used as additive to natural rubber mixtures. Freeze-dried materials were investigated by UV-VIS diffuse reflectance spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), thermal stability by thermogravimetric analysis (TGA). Antioxidant activity and total phenolic content (TPC) were also examined. Prepared samples were subjected to accelerated simulated degradation processes by using ultraviolet and thermo-oxidative aging. Vulcanizates resistance to degradation effects was determined by the study of cross-linking density (equilibrium swelling method), mechanical properties (tensile strength, elongation at break) and color change in comparison with the results of the reference samples. The research showed that analyzed extracts are characterized by a high content of polyphenols and antioxidant activity, thus have a protective influence on elastomer vulcanizates against damaging effects of aging processes, which consequently extends the lifetime of materials.

Potential Application of Peppermint (Mentha piperita L.), German Chamomile (Matricaria chamomilla L.) and Yarrow (Achillea millefolium L.) as Active Fillers in Natural Rubber Biocomposites.

In this study, peppermint (Mentha piperita L.), German chamomile (Matricaria chamomilla L.) and yarrow (Achillea millefolium L.) were applied as natural fibrous fillers to create biocomposites containing substances of plant origin. The purpose of the work was to investigate the activity and effectiveness of selected plants as a material for the modification of natural rubber composites. This research was the first approach to examine the usefulness of peppermint, German chamomile and yarrow in the field of polymer technology. Dried and ground plant particles were subjected to Fourier transmission infrared spectroscopy (FTIR) and UV-Vis spectroscopy, thermogravimetric analysis (TGA), goniometric measurements (contact angle) and scanning electron microscopy (SEM). The characterization of natural rubber composites filled with bio-additives was performed including rheometric measurements, FTIR, TGA, cross-linking density, mechanical properties and colour change after simulated aging processes. Composites filled with natural fillers showed improved barrier properties and mechanical strength. Moreover, an increase in the cross-linking density of the materials before and after the simulated aging processes, compared to the reference sample, was observed.

Modified Nanoclays/Straw Fillers as Functional Additives of Natural Rubber Biocomposites.

Increasingly, raw materials of natural origin are used as fillers in polymer composites. Such biocomposites have satisfactory properties. To ensure above-average functional properties, modifications of biofillers with other materials are also used. The presented research work aimed to produce and characterize elastomeric materials with a straw-based filler and four different types of montmorillonite. The main research goal was to obtain improved functional parameters of vulcanizates based on natural rubber. A series of composites filled with straw and certain types of modified and unmodified nano-clays in various ratios and amounts were prepared. Then, they were subjected to a series of tests to assess the impact of the hybrids used on the final product. It has been shown that the addition of optimal amounts of biofillers can, inter alia, increase the tensile strength of the composite, improve damping properties, extend the burning time of the material and affect the course of vulcanization or cross-linking density.

Common Nettle (Urtica dioica L.) as an Active Filler of Natural Rubber Biocomposites.

Common nettle (Urtíca Dióica L.), as a natural fibrous filler, may be part of the global trend of producing biocomposites with the addition of substances of plant origin. The aim of the work was to investigate and explain the effectiveness of common nettle as a source of active functional compounds for the modification of elastomer composites based on natural rubber. The conducted studies constitute a scientific novelty in the field of polymer technology, as there is no research on the physico-chemical characteristics of nettle bio-components and vulcanizates filled with them. Separation and mechanical modification of seeds, leaves, branches and roots of dried nettle were carried out. Characterization of the ground plant particles was performed using goniometric measurements (contact angle), Fourier transmission infrared spectroscopy (FTIR), themogravimetric analysis (TGA) and scanning electron microscopy (SEM). The obtained natural rubber composites with different bio-filler content were also tested in terms of rheological, static and dynamic mechanical properties, cross-linking density, color change and resistance to simulated aging processes. Composites with the addition of a filler obtained from nettle roots and stems showed the highest mechanical strength. For the sample containing leaves and branches, an increase in resistance to simulated ultraviolet and thermo-oxidative aging processes was observed. This phenomenon can be attributed to the activity of ingredients with high antioxidant potential contained in the plant.

Natural Rubber Biocomposites Filled with Phyto-Ashes Rich in Biogenic Silica Obtained from Wheat Straw and Field Horsetail.

The rich structural hierarchy of plants permits the obtainment of porous structures which can be expected to show improved performances in fields such as pharmaceuticals and cosmetics, catalysis, drug delivery, adsorption, separation or sensors in various chemical reactions. On the other hand, porous materials can be an active additive to polymer composites. The aim of the study was to obtain natural rubber (NR) biocomposites with the addition of phyto-ashes reach in biogenic silica from plant biomass. For the production of bioadditives, a two-stage method of high-temperature heat treatment was used, preceded by acid hydrolysis of plant tissues in the form of horsetail and wheat straw. Hydrolysis was performed with hydrochloric and citric acid. The efficiency of the processes and their influence on the elemental composition, surface morphology, thermal stability and particle size of the fillers were determined. Modified bioadditives were introduced into the elastomer matrix and their processing properties, as well as the vulcanization characteristics, were examined. Static mechanical properties (tensile strength, elongation at break, stress at 100%, 200% and 300% elongation), dynamic-mechanical analysis and the influence of additives on the cross-link density of the composites were determined. Structural analysis was performed using scanning electron microscopy. It was found that the field horsetail and cereal straw are plants rich in many valuable chemical compounds, especially silica. The specific and appropriate treatment of these plants can lead to bioadditives that significantly affect the properties of rubber materials.

Straw/Nano-Additive Hybrids as Functional Fillers for Natural Rubber Biocomposites.

Currently, up to 215 million metric tons of harvestable straw are available in Europe, 50% of the crops come from wheat, 25% from barley and 25% from maize. More than half of the production remains undeveloped. The overproduction of straw in the world means that the current methods of its management are insufficient. The article describes the production method and characterization of natural rubber biocomposites containing cereal straw powder modified with functional nano-additives in the form of carbon black, silica and halloysite nanotubes. The use of cereal straw in the elastomer matrix should contribute to obtaining a product with good mechanical properties while ensuring a low cost of the composite. In turn, the application of the mechanical modification process will allow the combination of specific properties of raw materials to obtain new, advanced elastomeric materials. As part of the work, hybrid fillers based on mechanically modified cereal straw were produced. The impact of hybrid fillers on mechanical, rheometric and damping properties was assessed. The flammability and susceptibility of the obtained biocomposites to aging processes were determined. The use of hybrid fillers based on mechanically modified straw allowed us to obtain a higher cross-linking density of vulcanizates (even up to 40% compared to the reference sample), and thus higher values of the rheometric moment during the vulcanization process of rubber mixtures (from approx. 10% (10 phr of filler) up to 50% (30 phr of filler) in relation to the unfilled system) and higher hardness of vulcanizates (by about 30-70%). The curing time of the blends was slightly longer, but the obtained composites were characterized by significantly higher tensile strength. The use of fillers in the elastomer matrix increased the modulus at 100, 200 and 300% and the elongation at break. Moreover, greater resistance of vulcanizates to the combustion process was confirmed.

Anti-Oxidative Activity of Alcohol-Water Extracts from Field Horsetail (Equisteum arvense) in Elastomer Vulcanizates Subjected to Accelerated Aging Processes.

The article aimed to highlight the antioxidant potential of natural extracts obtained from Equisteum arvense in elastomer vulcanizatec made of natural rubber. Horsetail extracts were prepared using four solvent systems at different volume ratios: methanol-water (50/50 and 70/30) and ethanol-water (50/50 and 70/30), which were then lyophilized and added to the polymer matrix. A deep characterization of the obtained bio-additives was performed. The obtained vulcanizates were subjected to various aging processes: thermo-oxidative, ultraviolet and solar. Then, the resistance and susceptibility of vulcanizates to selected processes of accelerated, simulated degradation were determined based on the changes in the spatial structure (network nodes), material strength and physical properties (color). The research showed the presence of polyphenols in the extracts of horsetail, which resulted in their high anti-oxidative activity. Moreover, the extracts were able to absorb UV radiation. As a consequence, they were active additives that protected rubber vulcanizates against the damaging effects of the aging processes, securing their functional properties. Samples containing natural extracts were characterized by better stability of: mechanical strength parameters, the increase in cross-linking density and color changes after simulating aging processes in comparison with the control sample.

Properties of Chemically Modified (Selected Silanes) Lignocellulosic Filler and Its Application in Natural Rubber Biocomposites.

This article concerns the functional properties of elastomeric composites reinforced with modified lignocellulosic material obtained from cereal straw. The aim of the research was to acquire new knowledge on the effectiveness of cereal straw modification methods in multifunctional properties, while reducing the flammability of newly designed elastomeric materials made of natural rubber. The article deals with investigating and explaining dependencies that affect the performance and processing properties of polymer biocomposites containing modified cereal straw. Three different silanes were used to modify the lignocellulosic filler: n-Propyltriethoxysilane, Vinyltriethoxysilane, and 3,3'-Tetrathiobis(propyl-triethoxysilane). The influence of the conducted modifications on the morphology and structure of straw particles was investigated using a scanning electron microscope, contact angle measurements, and thermogravimetric analysis technique. The increase in hydrophobicity and thermal stability of natural fibers was confirmed. In turn, the impact of silanization on the properties of filled composites was determined on the basis of rheometric characteristics and cross-linking density, static mechanical properties, tear resistance, thermal stability, and flammability tests. Noteworthy was the improvement of the mechanical strength of biocomposites and their resistance to burning. Correlations affecting the structure, morphology, dispersion, and properties of produced composites can facilitate the indication of a further research path in the field of development of new elastomeric biomaterials.

Horsetail (Equisetum Arvense) as a Functional Filler for Natural Rubber Biocomposites.

Over the past decades, increased scientific and research activity has been observed in the development of new, innovative materials for various end uses. This is mainly due to the growing ecological, environmental, and material awareness of many industries and societies. Equisteum arvense-horsetail is a plant that has demonstrated its properties in pharmacological and clinical aspects as well as in vitro and in vivo biological activity. This article presents a new method of using horsetail as a natural, lignocellulosic filler for a natural rubber matrix. In-depth characteristics of the applied bio-additive were prepared based on several research techniques and methods such as ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-RAY spectroscopy, thermogravimetric analysis, and flame atomic absorption spectroscopy. Elastomer composites were prepared as a function of horsetail content. Then, an analysis of their main functional properties was performed, including mechanical properties and susceptibility to accelerated aging processes such as thermo-oxidative, ultraviolet radiation, and weathering. The research emphasizes the significant value of horsetail in its new role-as an active filler of elastomer biocomposites. The obtained results confirmed that horsetail is lignocellulosic material thermally stable up to 180 °C. Horsetail is an active filler to natural rubber, positively affecting mechanical strength. Due to the presence of flavonoids and phenolic acids in horsetail, it can be used as a polymer anti-aging agent.

Thermoplastic Elastomeric Composites Filled with Lignocellulose Bioadditives. Part 1: Morphology, Processing, Thermal and Rheological Properties.

Thermoplastic elastomer blends based on natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) with different weight ratios (30, 40, 50, 60 and 70 parts per hundred rubber (phr) of NR) and 10, 20 and 30 phr of straw were prepared and characterized. Current environmental problems were the motivation to produce this type of system, namely: the need to replace plastics at least partly with natural materials; increasing the amount of renewable raw materials and managing excess straw production. When using this bioadditive in traditional materials, the high processing temperature can be problematic, leading to the degradation of straw fibers. The solution can be polymer mixtures that are prepared at significantly lower temperatures. Scanning electron microscope (SEM) imaging was used to investigate the particle size of fibers and phase morphology of composites. Moreover, determination of the thermal properties of the filler and composites showed that the processing temperature used in the production of NR/EVA blends reduces the risk of degradation of the natural filler. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the filled composites. Finally, rheological tests of materials allow the determination of optimal processing parameters and properties of materials in dynamic conditions. The proposed blends exhibit elastic properties, and due to the lack of chemical cross-linking they can be processed and recycled like thermoplastics. In addition, they offset the disadvantages and combine the advantages of natural rubber and ethylene-vinyl acetate copolymer in the form of thermoplastic elastomeric biocomposites.

Thermoplastic Elastomeric Composites Filled with Lignocellulose Bioadditives, Part 2: Flammability, Thermo-Oxidative Aging Resistance, Mechanical and Barrier Properties.

The work covers the characteristics of the functional properties of composites bordering thermoplastics and elastomers. The research is a continuation of considerations on blends in the form of a mixture of natural rubber (NR) with an ethylene-vinyl acetate copolymer (EVA) and the addition of a lignocellulose biofiller (wheat straw). After describing the processing and rheology as well as examining the thermal properties and morphology of composites (Part 1), the second part focuses on the characteristics of their performance. The effect of both different ratios of mixed polymers and the amount of filler on tensile strength and elongation at break, resistance to thermo-oxidative aging, hardness, tear resistance, barrier and damping properties, as well as flammability were investigated. The increased EVA content has shown a positive effect on tensile strength, elongation at break, resistance to thermo-oxidative aging, hardness, relative damping, tear strength, barrier and burning delay. On the other hand, a larger amount of natural rubber provides high flexibility and promotes the creation of a reinforcing structure by the filler used. Moreover, a significant impact of the addition of cereal straw on the barrier, damping, strength and flammability properties of composites was also noted. The great advantage of the prepared compositions in relation to commercial plastics is their environmental friendliness, primarily by replacing some petroleum derivatives of plastics with natural rubber and straw fibers.

Natural Rubber Composites Filled with Crop Residues as an Alternative to Vulcanizates with Common Fillers.

This present study is focused on exploring the possibility of using agricultural waste in the form of cereal straw as an active filler of biocomposites. The effect of lignocellulosic filler addition on the multifunctional properties of natural rubber composites was investigated. The results were compared with the properties of vulcanizates containing commonly used reinforcements in elastomer technology (carbon black, silica, chalk, talc). Rubber mixtures filled with straw showed the highest torque increase during rheometric measurements, which indirectly indicated a high degree of crosslinking and hardness of composites. It was found that the effect of straw addition on vulcanization time of elastomer blends was comparable with the results obtained for other conventional fillers. Moreover, the results confirmed that novel composites based on natural rubber filled with crop residues were attractive materials owing to their capacity for the formation of "structure" in combination with a good impact on reinforcement. Vulcanizates with the addition of straw showed the best barrier properties and resistance to thermo-oxidative aging from all tested samples. Furthermore, straw-based composites demonstrated that cereal straw waste could be used as an alternative, biodegradable and eco-friendly reinforcement of natural rubber composites.

Thermoplastic Elastomer Biocomposites Filled with Cereal Straw Fibers Obtained with Different Processing Methods-Preparation and Properties.

This work is focused on thermoplastic elastomers composites (TPEs) reinforced with straw. Crop waste with different particle size was used as a filler of ethylene-octene rubber (EOR). Application of cheap and renewable natural fiber like straw into a TPE medium is not fully recognized and explored. The effect of fiber orientation induced by two processing techniques on the different mechanical properties of composites was investigated. Microscopic images were used to present the tested straw fractions and observe the arrangement and dispersion of fibers in the polymer matrix. It was found that the usage of an injection molding process allowed for the forming of a more homogenous dispersion of short fiber particles in the elastomer matrix. An oriented straw filler and polymer chains resulted in the improved mechanical strength of the whole system as evidenced by the obtained values of tensile strength almost two times higher for injected composites. In addition, all composites showed very good resistance to thermo-oxidative aging, where the aging factor oscillated within the limits of one, regardless of the processing method and the amount of bioadditive used. On the other hand, vulcanized composites were characterized by greater tear resistance, for which Fmit values increased by up to 600% compared to the reference sample.