Opuntia spp. Fibre Characterisation to Obtain Sustainable Materials in the Composites Field

Some studies have evaluated the use of Opuntia as reinforcement for polymeric matrices, obtaining good results in energy absorption tests and increasing the tensile elastic modulus. However, no studies focusing on the previous characterisation of the fibres and their treatment to improve compatibility with polymeric matrices have been found. This work analyses the chemical composition of Opuntia maxima (OM) and Opuntia dillenii (OD) cladodes and fibre, studying how different treatments influence it. AOAC 2000 methods were used to determine non-structural components and the Van Soest method was used to estimate structural components. Surface characteristics of the samples were also evaluated by Fourier Transform Infrared Spectroscopy (FTIR). Opuntia fibre presented higher cellulose (50–66%) and lignin (6–14%) content and lower hemicellulose (8–13%) content than Opuntia cladodes (9–14% cellulose, 20–50% hemicellulose, 1–4% lignin). Despite the variability of lignocellulosic materials, OD cladodes treated with water and acetic acid achieved an increase in the structural components. Alkaline fibre treatment removed pectin and hemicellulose from the fibre surface, slightly increasing the cellulose content. Future research should evaluate whether the treated Opuntia fibre can improve the mechanical properties of reinforced polymer.

Epoxy Nanocomposites Reinforced with Functionalized Carbon Nanotubes

In this article, amino functionalized multiwalled carbon nanotubes (MWCNTs) were prepared by chemical modification of the surface of a MWCNTs using γ-aminopropyltriethoxysilane (APTES) and dispersed into the epoxy composition. The modifying agent (APTES) was directly deposited on the MWCNTs surfaces. For the functionalization of MWCNTs, was used not the APTES concentrate, as it had been described in previous works, but its freshly prepared aqueous solution. Properties of APTES-treated MWCNTs were characterized by transmission electron microscope (TEM), Raman spectroscopy and FT-IR. The results showed that the functionalization and chemical compatibility of APTES-treated MWCNTs with epoxy composition provides their best dispersion in the epoxy composition, had important influence on curing behavior, structure and physicochemical properties of the epoxy composites plasticized with trichloroethyl phosphate. The results showed that the functionalization and chemical compatibility of APTES-treated MWCNTs with epoxy composition provides increased of physicomechanical properties of epoxy composites: bending stress increases by 194% and bending modulus increases by 137%, the tensile strength increases by 108% and the tensile elastic modulus increases by 52%, impact strength increases by 300%, in comparison with plasticized epoxy composite that does not contain MWCNTs.

Comparative Study on the Test Method for Tensile Elastic Modulus of Rock Materials

Rock material has different mechanical behaviors under compressive and tensile loading. Correspondingly, there are two types of elastic modulus: compressive elastic modulus Ec and tensile elastic modulus Et, respectively. To distinguish which indirect test methodology, including three-points bending test and Brazilian disc test, is more suitable to measure the tensile elastic modulus Et of rock materials, a series of uniaxial compressive test (UCT), direct tensile test (DTT), three-points bending test, and Brazilian disc test are performed for three typical types of rock: marble, granite, and sandstone. Comparative investigation on the reliability of measurement results of tensile elastic modulus Et is systematically conducted. Finally, it is found that Brazilian disc test could be a suitable method to measure tensile elastic modulus of rock materials, due to the excellent agreement with that measured by DTT and the simplicity of sample preparation, as well as test operation.

Compatibilising additives for enhancing the interaction at the phase interface in thermoplastic vulcanisates based on rubbers of different polarity and polypropylene*

The possibilities of increasing the interaction between the components of previously developed thermoplastic vulcanisates based on polypropylene and a combination of isoprene and nitrile butadiene rubbers were studied. The morphology of the composites was recorded by means of optical microscopy using an analytical complex based on a Leica DM-2500 optical microscope, a Leica DFC-420C digital high-resolution colour camera with a Peltier cooling system, and a specialised computer desk. The parameters of crystallisation of polypropylene were measured by differential scanning calorimetry using a DSC 204F1 Phoenix instrument (Netzsch). The physicomechanical properties of the vulcanisates were also determined. Maleinised polypropylene, a copolymer of ethylene with vinyl acetate, and their mixtures were used as compatibilising additives. Maleinised polypropylene was introduced together with polypropylene in a quantity of 1–10 parts; no changes in properties were observed with increase in the dosage above 4 parts, so this dosage was used. The copolymer of ethylene with vinyl acetate (1–10 parts) was introduced into the rubber phase at the stage of rubber mix preparation specially to improve the compatibility of polypropylene and nitrile butadiene rubber. The introduction of maleinised polypropylene leads to an increase in the workability and in the level of elastic strength properties, in particular the tensile elastic modulus and hardness. A considerable increase in the uniformity of distribution of components throughout the volume, a finer dispersion of the rubbers in the polypropylene matrix, and a reduction in the number of pores in the material were shown, and also an increase in the degree of polypropylene crystallinity measured under experimental conditions. The most positive effect is observed with the combined introduction of the copolymer of ethylene with vinyl acetate and the maleinised polypropylene: the nominal stress under elongation increases by 34%, and the elongation at break by 15%. The combined introduction of the compatibilising additives improves the compatibility of the components of the system, the phase boundaries become more diffuse, there is a reduction in the optical density of rubber-rich zones, and these zones are penetrated by polypropylene fibrils.

Effect of Printing Temperature on Mechanical Properties and Surface Quality of Photosensitive Resin Rapid Prototyping Parts

The rapid prototypes of different printing temperature by Objet30 Stratasys Pro printer were found a certain difference in performance in the process of using the process.In order to studied the effect of printing temperature on the rapid prototyping of photosensitive resin, tensile and bending tests were carried out on the rapid prototyping parts at 12°C, 18°C, 21°C, 23°C, 25°C, 30°C,respectively,and the rigidity and surface roughness of rapid prototyping parts were measured.Research shows：the tensile strength increases with the increase of printing temperature , tensile elastic modulus fluctuates with the printing temperature , they all increases rapidly after 25°C;The bending strength increases proportional with the increase of printing temperature, and the bending modulus increases first and then tends to decrease with the increase of printing temperature;The hardness value increases slowly with the increase of printing temperature, and increases obviously after 20°C,the hardness value in the middle of the prototype parts is bigger than the edge parts；The surface roughness with increasing printing temperature, although it is floating up and down, but have little effect.

Finite Element Calculation for the Tensile Elastic Modulus of Honeycomb Materials with Different Pore Shape

The square and hexagonal honeycomb materials were studied by finite element simulation of tensile test in order to calculate the elastic modulus in tension under different porosity and to analyze tensile properties affected by the pore shape of honeycomb materials. Research results show that the tensile elastic modulus of the square honeycomb is larger than the hexagonal honeycomb. The reason is that the square structure has a larger stiffness than hexagonal structure. Also, the equivalent elastic moduli of calculated values are higher than the theoretical values, because the finite element model is based on solid elements while the theoretical model is based on the Euler beam.