جستجوی مقالات مرتبط با کلیدواژه « thermal properties » در نشریات گروه « جنگلداری »

Generally speaking, PVAc (polyvinyl acetate) adhesive has weak strength properties with capability of using in wooden products such as wood adhesive. The carbon nanomaterial (CNF) is one of the most influential substances on the strength properties of polymer materials. Thus, the mechanical and thermal properties of polyvinyl acetate glue reinforced with carbon nanofibers were investigated in both modified and virgin cases and three levels of zero, 0.4 and 1.5% by weight of glue. Modified carbon nanofibres were used to improve the dispersion of polymeric matrix by surface chemical modification method. The results of the FTIR spectroscopy test were confirmed oxidation and presence of new functional groups on the surface of modified carbon nanofibers. Mentioned nanocomposites made by solvent molding method and evaluated the tensile properties, thermal behavior (TGA) and microstructure. Transmission electron microscope (TEM) images indicated better dispersion of modified nanoparticles in 0.4% than higher values in the glue matrix. Also analysis data of the tensile test data showed improvement of mechanical behavior of nanocomposites (elasticity modulus, tensile strength, and fracture energy) due to the presence of modified nanoparticles. Improvement of these properties with modified carbon nanofibers was 2.4, 1.6 and 1.8 times, respectively, compared to pure polyvinyl acetate. In addition, two stages of reduction mass relative observed than the pure adhesive in thermal stability of both nanocomposite series. Generally speaking, the best tensile strength observed in nanocomposite specimens containing 0.4% w/w with modified carbon nanofibers.

Wood plastic composite that briefly (WPC) called are a new class of composite materials that in recent years have been the attention of many researchers and a major part of the industry. For improve some properties of wood plastic composite, various nanoparticles was used that one of them is clay that due to the high specific surface and mineral source, improves properties of nanocomposite. Therefore this study with aim to investigation the effect of nanoclay and polypropylene oxide coupling agent (OPP) on Phragmites australis flour/waste polypropylene was done.
For this purpose first polypropylene was oxidized in molding phase and in the presence of atmospheric oxygen and alcohol. Then Phragmites australis flour and polypropylene with were mixed weight ratio of 50% in internal mixer. Nanoclay to 3 levels 0, 2 and 4% and coupling agent to 2 levels 0 and 3% were used. Test boards were made using a hot press. Physical properties such as long-term water absorption and thickness swelling, humidity coefficient diffusion and thickness swelling rate, thermal properties such as thermal analysis (TGA) and morphological properties such as X-ray diffraction (XRD), the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were done. To ensure the oxidation of polypropylene as well as infrared spectroscopy (FTIR) were used.
The results showed that the long-term water absorption and thickness swelling, humidity coefficient diffusion and thickness swelling rate were decreased with increasing of nanoclay and coupling agent (OPP),. Thermal properties of nanocomposite improved with increasing of nanoclay and coupling agent. The result of field emission scanning electron microscopy (SEM) showed that by addition of coupling agent, the interface between two phase's lignocellulosic fiber and polymeric matrix improvement. The result of X-ray diffraction (XRD) showed that with increasing of nanoclay to 2%, the distance between the silicate layers of clay increased but by addition 4T nanoclay, the distance between the silicate layers slightly decreased and type in nanocomposite structure is intercalation. The transmission electron microscopy (TEM) as well as approved this. The result of infrared spectroscopy (FTIR) indicates the oxidation of polypropylene in the presence of oxygen.
As a general conclusion can be said that the use of nanoclay and compatibility oxidized polypropylene (OPP), improved properties of Phragmites australis flour/polypropylene nanocomposite. Therefore, the use of 2% nanoclay (for cost-effectiveness) with 3% OPP for the manufacture of composites with desirable features is recommended. K

In this research, the effect of nanoclay on physiochemical, thermal and structural properties of urea formaldehyde resin (UF) was investigated. The prepared GLUF resin was mixed mechanically with the 0.5, 1 and 1.5% nanoclay for 5 min at room temperature. The physicochemical properties of the prepared resins were measured according to standard methods. Also, the thermal and structural changes in UF resin containing nanoclay were measured by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectrometry (FTIR) and X-ray Diffractometry (XRD). The physicochemical test results indicated that by addition of nanoclay the viscosity, solid content and density values were increased while the free formaldehyde and gelataion time of resin were decreased. FTIR analysis indicated that the addition of nanoclay decreased the methylene linkages in UF resin. Moreover, the new peak was appeared at 850 and 1140 cm-1 bands in nanoclay filled UF resin dealing that a chemical interaction between nanoclay and UF resin was accrued. According to DSC analysis nanoclay accelerates the curing temperature of resin while the onest and temperature peaks dramatically decreased. XRD analysis showed that nanoclay completely exfoliated in UF resin.

In this study, the effect of filler content and compatibilizer on thermal properties of wood flour - high density polyethylene (HDPE) composites was investigated. To meet this objective, HDPE and wood flour (50, 60 and 70 wt %) with coupling agent (0, 2 and 4 wt %) were compounded in an internal mixer, and samples were fabricated by injection molding. Thermal properties and fractional crystallinity of samples were studied by thermogravimetric analysis (TGA) and differential scanning calorimetriy (DSC). The lower weight loss at higher temperature was found for composites containing higher amount of wood flour; Also, the thermal properties of composite samples increased with the increasing of wood flour up to loading fraction of 60%, but decreased using higher (70) wood flour loading fraction. The positive effect of filler on thermal properties is related to wood flour acted as nucleating agent, and decrease the thermal properties at higher filler content levels is probably due to the stop the growth of crystals and the formation of amorphous. Besides, the adding of compatibilizer to the composites boosted the thermal stability and fractional crystallinity of samples. The scanning electron microscopy (SEM) micrographs demonstrate a better adhesion between the HDPE and wood flour due to the presence of the coupling agent.

Polylactic acid based Biodegradable nanocomposites reinforced with acetylated nanocellulose were fabricated with solution casting procedure. The nanocomposites were prepared by adding 1، 3 and 5% nanofiber loadings. The microstructure، physical، mechanical and thermal properties of the prepared nanocomposites were investigated. Scanning electronic microscope (SEM) analysis of the composites confirmed the uniform distribution of nanoparticles within the matrix at low percentages. According to water vapor barrier test results، acetylated fibers did not improve the permeability of the prepared composites. Tensile strength (elongation) of nanocomposites had improved significantly by reinforcing with nanofibers due to the good dispersion of nanofibers at 1 and 3 percent، while the increase of nanofiber led to an aggregation and a brittle film with increased modulus of elasticity. Reinforcing effect of nanocellulose caused an increase in glass transition and melting temperature of the composites. However، the thermal behavior of nanocomposite and pure PLA films showed a very similar pattern.

In the present study, chemical-physical properties of nanofibers isolated from whole kenaf stem and kenaf bast fibers were characterized by Transmission Electron Microscope (TEM), Fourier Transform Infrared (FTIR), Thermogravimetric Analysis (TGA), and X-ray Diffraction (XRD) analysis. The isolation was done using chemo-mechanical processing where the chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes. The mechanical techniques involved refining, cryo-crushing and high-pressure homogenization. Microscopy study showed that the diameter range of isolated nanofibers from kenaf stem was finer than kenaf bast nanofibers, while their length was similar and in the micrometer range. Fourier transform infrared spectroscopy (FTIR) study demonstrated that the functional groups for both nanofibers were almost the same and no significant differences were observed. The results from thermo-gravimetric analysis showed a better thermal stability for kenaf bast nanofibers compared to the kenaf stem nanofibers. X-ray analysis revealed that the crystallinity of the studied nanofibers was increased after the chemo mechanical isolation process. In addition, the crystallinity was 81% and 63% for kenaf bast and kenaf stem nanofibers, respectively.

The main objective of this work was to study the effects of nanoclay (NC)، microcrystalline cellulose (MCC)، and coupling agent (MAPP) on the mechanical and thermal properties. The results showed that mechanical properties of the composites made with MCC were significantly superior to those of unfilled. Addition of MAPP could enhance the mechanical and thermal properties of the blends، due to the improvement of interface bond between the filler and matrix. The significant improvements in tensile properties of the blends composites made with MAPP and NC were further supported by SEM micrographs. The thermo gravimetric analysis indicated that the addition of 5 wt. % MAPP and 3 wt. % NC remarkably increased the thermal stability of the blends compared to the pure PP. It is to be noted that MCC could not improve the thermal stability.