Effect of degree of silanization of luffa on the properties of luffa-epoxy composites

Influence of Silanization Treatment of Sponge Gourd (Luffa cylindrica) Fibers on the Reinforcement of Polyester Composites: A Brief Report

Natural lignocellulosic fibers (NLFs) have been extensively investigated and applied as reinforcements for polymers composites owing to improved properties associated with their cost-effectiveness and their sustainable characteristics as compared to synthetic fibers. However, an intrinsic difficulty of the hydrophilic NFL adhesion to a hydrophobic polymer matrix is still a major limitation, which might be overcome via fiber surface treatments. Among the less-known NLFs, sponge gourd (Lufta cylindrica) is a promising reinforcement for polymer composites owing to its natural network of intertwined fibers. The present work investigated for the first time the influence of a chemical treatment using silane as a coupling agent for 30 wt.% sponge gourd incorporated into a polyester matrix composite. The novel composite performance was compared with that of an untreated fiber composite via X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Charpy impact tests, and thermogravimetric analyses (TGA). The XRD results revealed that the silanization increased the crystallinity index by 37%, which attests to the effective fiber–matrix interaction stretching of the C-H bond, as observed in its FTIR band. The silanization also increased the mean impact resistance by 10%. Although the temperatures associated with the beginning of the thermal degradation by the TGA were not affected, both the silane-treated fibers and composite displayed less thermal degradation compared with the untreated fibers. The scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) results disclosed an improved sponge gourd fiber morphology after the silanization, which caused greater adherence to the polyester matrix. These results revealed a promising novel composite compared with other NLF polymer composites in engineering applications.

The Effect of Ash Silanization on the Selected Properties of Rigid Polyurethane Foam/Coal Fly Ash Composites

According to the assumptions of the European Union, by 2050 it is planned to achieve climate neutrality. For this purpose, a document called the “European Green Deal” was established, which is a set of policies of the European Commission. One of the assumptions is a circular economy that takes into account the use of waste in subsequent production cycles. In order to meet the latest trends in environmentally friendly materials and use of waste in the production of building materials, composites of rigid polyurethane foam with 10 wt.% of waste were produced. Fly ash from coal combustion after modification was used as a filler. Three types of modifications were used: silanization, sieving, and both processes together. The silanization process was carried out for 1 and 2% silane ([3-(2-aminoethylamino)propyl]trimethoxysilane) concentration in relation to the fly ash mass. The sieving was aimed at reaching a fraction with a particle diameter below 75 µm. Six composites with modified fillers were compared and one material containing unchanged fly ash was used as a reference. A comparative analysis was carried out on the basis of surface analysis, thermal stability and physical properties. It turned out that the polyurethane materials modified fly ash silanized with 1% and 2% silane solution proved the best results in performed tests. On the other hand, the polyurethane foam containing sieved ash was characterized by the lowest flammability and the lowest emission of smoke and CO. The use of modified fly ash in technology of polyurethane foams can be a good method of its disposal and can increase the applicability of the composites.

Effect of Calcination Temperature on the Phase Composition, Morphology, and Thermal Properties of ZrO2 and Al2O3 Modified with APTES (3-aminopropyltriethoxysilane)

This paper describes the effect of calcination temperature on the phase composition, chemical composition, and morphology of ZrO₂ and Al₂O₃ powders modified with 3-aminopropyltriethoxysilane (APTES). Both ceramic powders were modified by etching in piranha solution, neutralization in ammonia water, reaction with APTES, ultrasonication, and finally calcination at 250, 350, or 450 °C. The obtained modified powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, particle size distribution (PSD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and thermogravimetric analysis (TGA).

Effectiveness of Silanization and Plasma Treatment in the Improvement of Selected Flax Fibers' Properties

The study investigated the effectiveness of the combination of chemical and physical methods of natural fibers’ modification. The long flax fibers were subjected to various types of modification. These were silanization, plasma modification and a combination of these methods. For the silanization process, two types of silanes were used: amino- and vinylsilane. The application of structurally different compounds allowed us to acquire knowledge about the effect of the modifier structure on its properties. Various properties of flax fibers were investigated, comparing the results before and after different modification processes. The flammability of prepared samples were tested by pyrolysis combustion flow calorimeter (PCFC). In the effect of the natural fibers’ modifications, flammability was reduced even by 30%. The thermal stability of modified fibers increased. The FTIR tests of the gases released during thermal degradation of the tested fibers allowed us to determine the important compounds and prove a lower degree of flax-fiber decomposition after modification. Flax fibers were also tested to evaluate their physical properties (linear mass, average diameter, aspect ratio and hygroscopicity). Changes in surface morphology were observed by scanning electron microscope (SEM). The properties of natural fibers improved significantly, thus contributing to an increase in their suitability for the use in composites.

Recent Developments in Luffa Natural Fiber Composites: Review

Natural fiber composites (NFCs) are an evolving area in polymer sciences. Fibers extracted from natural sources hold a wide set of advantages such as negligible cost, significant mechanical characteristics, low density, high strength-to-weight ratio, environmental friendliness, recyclability, etc. Luffa cylindrica, also termed luffa gourd or luffa sponge, is a natural fiber that has a solid potential to replace synthetic fibers in composite materials in diverse applications like vibration isolation, sound absorption, packaging, etc. Recently, many researches have involved luffa fibers as a reinforcement in the development of NFC, aiming to investigate their performance in selected matrices as well as the behavior of the end NFC. This paper presents a review on recent developments in luffa natural fiber composites. Physical, morphological, mechanical, thermal, electrical, and acoustic properties of luffa NFCs are investigated, categorized, and compared, taking into consideration selected matrices as well as the size, volume fraction, and treatments of fibers. Although luffa natural fiber composites have revealed promising properties, the addition of these natural fibers increases water absorption. Moreover, chemical treatments with different agents such as sodium hydroxide (NaOH) and benzoyl can remarkably enhance the surface area of luffa fibers, remove undesirable impurities, and reduce water uptake, thereby improving their overall characteristics. Hybridization of luffa NFC with other natural or synthetic fibers, e.g., glass, carbon, ceramic, flax, jute, etc., can enhance the properties of the end composite material. However, luffa fibers have exhibited a profuse compatibility with epoxy matrix.