Processing and structure-property relationships of natural rubber/wheat bran biocomposites

In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer compositesPostprint (author's final draft

Compatibility of Sustainable Mater-Bi/poly(ε-caprolactone)/cellulose Biocomposites as a Function of Filler Modification

Despite their popularity and multiplicity of applications, wood–polymer composites (WPCs) still have to overcome particular issues related to their processing and properties. The main aspect is the compatibility with plant-based materials which affects the overall performance of the material. It can be enhanced by strengthening the interfacial adhesion resulting from physical and/or chemical interactions between the matrix and filler, which requires introducing a compatibilizer or a proper modification of one or both phases. Herein, the impact of cellulose filler modifications with varying contents (1–10 wt%) of hexamethylene diisocyanate (HDI) on the compatibility of Mater-Bi/poly(ε-caprolactone) (PCL)-based biocomposites was evaluated. An analysis of surface wettability revealed that the filler modification reduced the hydrophilicity gap between phases, suggesting compatibility enhancement. It was later confirmed via microscopic observation (scanning electron microscopy (SEM) and atomic force microscopy (AFM)), which pointed to the finer dispersion of modified particles and enhanced quality of the interface. The rheological analysis confirmed increased system homogeneity by the reduction in complex viscosity. In contrast, thermogravimetric analysis (TGA) indicated the efficient modification of filler and the presence of the chemical interactions at the interface by the shift of thermal decomposition onset and the changes in the degradation course.This work was supported by the National Science Centre (NCN, Poland) in the frame of SONATINA 2 project 2018/28/C/ST8/00187—Structure and properties of lignocellulosic fillers modified in situ during reactive extrusion. The study was partially co-funded under project with grants for education allocated by the Ministry of Science and Higher Education in Poland executed under the subject of No 0613/SBAD/4820

Reclaimed rubber/poly(e-caprolactone) blends: structure, mechanical, and thermal properties

The amount of elastomeric waste, especially from tires is constantly increasing on a globalscale. The recycling of these residua should be considered a priority. Compounding the waste rubberswith other polymers can be an excellent alternative to reuse waste materials. This procedure requiressolving the issue of the lack of compatibility between the waste rubber particles and other polymers.Simultaneously, there is a claim for introducing biodegradable plastics materials to reduce theirenvironmental impact. In this work, reclaimed rubber/poly(e-caprolactone) (RR/PCL) blends areproposed to enhance the recycling and upcycling possibilities of waste rubbers. The results showthat the addition of PCL to the RR allows obtaining blends with improved mechanical properties,good thermal stability, and enhanced interfacial compatibility between the used components. Structureand properties of the proposed RR/PCL have been studied by means of static and dynamic mechanicaltesting, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC),and thermogravimetric analysis (TGA)-FTIR analysisPostprint (published version

POM/EVA Blends with Future Utility in Fused Deposition Modeling

Polyoxymethylene (POM) is one of the most popular thermoplastic polymers used in the industry. Therefore, the interest in its potential applications in rapid prototyping is understandable. Nevertheless, its low dimensional stability causes the warping of 3D prints, limiting its applications. This research aimed to evaluate the effects of POM modification with ethylene-vinyl acetate (EVA) (2.5, 5.0, and 7.5 wt.%) on its processing (by melt flow index), structure (by X-ray microcomputed tomography), and properties (by static tensile tests, surface resistance, contact angle measurements, differential scanning calorimetry, and thermogravimetric analysis), as well as very rarely analyzed emissions of volatile organic compounds (VOCs) (by headspace analysis). Performed modifications decreased stiffness and strength of the material, simultaneously enhancing its ductility, which simultaneously increased the toughness even by more than 50% for 7.5 wt.% EVA loading. Such an effect was related to an improved linear flow rate resulting in a lack of defects inside the samples. The decrease of the melting temperature and the slight increase of thermal stability after the addition of EVA broadened the processing window for 3D printing. The 3D printing trials on two different printers showed that the addition of EVA copolymer increased the possibility of a successful print without defects, giving space for further development

Clays as Inhibitors of Polyurethane Foams’ Flammability

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings

Special Issue: Structure, Properties and Applications of Polymeric Foams

The Special Issue “Structure, Properties and Applications of Polymeric Foams” aimed to gather the numerous reports associated with the different aspects of polymeric foams [...

Towards Understanding the Health Aspects of the Processing of Lignocellulosic Fillers

Health and safety issues should be addressed during the development and investigation of industrial processes. In order to develop a sustainable process and fully evaluate its benefits and drawbacks for its optimization, it is crucial to determine its impact on the surrounding environment. This study aimed to assess the emission of volatile organic compounds during the modification of lignocellulosic fillers with passive dosimetry. Two types of processes were investigated: diisocyanate treatment of commercial lignocellulosic fillers in a batch mixer and thermo-mechanical treatment of brewers’ spent grain using a twin-screw extruder. The presence of multiple terpenes and terpenoids was detected during the processing of fillers. The main compounds detected during modification were camphene, 3-carene, limonene, α-pinene, and cymenes. These compounds can cause irritation and allergic reactions, according to the Globally Harmonized System of Classification and Labelling of Chemicals, as well as NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response. Some of them are also characterized by relatively low values of flash points, even below 40 °C. Therefore, their emissions during the modification of cellulose materials should be carefully monitored, and proper precautions need to be taken

Renewable, Degradable, and Recyclable Polymer Composites

The substantial plastic pollution reaching almost every area of our planet and every aspect of human lives is pushing the polymer sector towards a circular economy, which would significantly limit its environmental impact [...

Recycling and Processing of Waste Materials

Just a few days ago, the world population, as expected, surpassed 8 billion [...