Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.     

Preparation and wave-absorbing properties of rhombic cross-sectional FeSiAlp/PP magnetic fibers

ABSTRACT

Adjusting fibers shape can further optimize absorbing properties of the FeSiAl_p/PP fibers composites. 80 wt% FeSiAl_p/PP rhombic cross-sectional fibers were successfully prepared by liquid phase blending and extrusion drawing. The strength of the fibers is about 6 ~ 8 MPa. The effective absorption bandwidth (EAB, RL < ?10 dB) of the resin matrix composites modified by rhombic cross-sectional fibers is 3.9 GHz and the optimal RL reaches ?18.43 dB at 4.5 GHz. Compared with the resin matrix composites modified by circular cross-sectional fibers, the EAB increases by 1.8 GHz and there is a second absorption peak, which has better broadband absorption characteristics.     

On the Role of Both Polypropylene Fibers and Silica Nanoparticles on the Viscoelastic Behavior of Silicone Rubber Nanocomposites

In the present study, silica nanoparticles and polypropylene fibers were added to silicone rubber matrix and their effect was investigated on the viscoelastic behavior of silicone rubber composites by dynamic mechanical analysis and compression set test. Bonding of the reinforcements with silicone rubber matrix was studied by Fourier transform infrared spectroscopy (FTIR). The results proved that the role of silica particles on the elastic modulus of silicone rubber was more effective than that of polypropylene at room temperature because of higher stiffness and also partial interaction of polypropylene with matrix.     

Effects of Defibration Conditions on Mechanical and Physical Properties of Wood Fiber/High-Density Polyethylene Composites

Defibration conditions influence wood fiber characteristics and thereby properties of fiber-based materials. In this study, the effects of several defibration conditions on mechanical and physical properties of fiber-based wood-plastic composites (WPCs) are illustrated. Various WPCs were tested containing different thermo-mechanical pulps (TMPs) or groundwood pulp (GWP), whereby material composition (50 wt% wood fibers, 47 wt% polymer, 3 wt% coupling agent) and the production process (internal mixer, injection molder) were kept consistent. The data from the experiment revealed that differing defibration conditions led to statistically significant differences in the tested flexural, tensile, and impact properties as well as in the water absorption of WPC. Overall, the GWP and the TMP which was produced under the mildest defibration conditions performed best in fiber-based WPCs. Therefore, grinders and refiners may be equally suitable to produce pulp for WPC usage. As a side-effect within this study, the reinforcing effect of fiber application on flexural and tensile properties was on an extraordinarily high level.     

Effect of fiber reinforcement on deformability properties of cemented sand

In this study, a series of unconfined compression tests have been performed to determine the effect of polyvinyl alcohol (PVA) fiber inclusion on deformation characteristics of cemented sand. The cement contents were 2, 4, and 6% by weight of the dry sand and samples were cured for 7 days. PVA fibers with a length of 12 mm and a diameter of 0.1 mm were added to sand-cement mixtures at a weight ratio of 0.0%, 0.3%, 0.6% and 1% (dry wt.). The compression stress-axial strain, secant modulus of elasticity (E₅₀), tangent modulus of elasticity (E_tan), failure mode, energy absorption capacity (EA), energy base index, strain base index, deformability index and axial strain at peak strength of the samples were described. Tests results show that addition of cement to sand increased stiffness and unconfined compression strength (UCS), and leading to a brittle behavior. Moreover, addition of PVA fibers to cemented sand increased the UCS and axial strain at peak strength and increased softening stress after the maximum strength. In addition, the fiber inclusion increases the energy absorption capacity and decreases the secant modulus of elasticity.     

Effect of Sodium Bicarbonate on the Mechanical and Degradation Properties of Short Jute Fiber Reinforced Polypropylene Composite by Extrusion Technique

Short jute fibers and the pellets of polypropylene (PP) were compounded to make composites with the help of an extruder followed by compression molding. The mechanical properties of the composites increased with the increase of fiber content up to 20%, then decreased while the jute content varied from 5 to 30 wt%. Composites with varying percentages (5 to 20%) of sodium bi-carbonate at constant (20%) jute content were made by same process. The mechanical properties, soil degradation tests, and the water uptake capacity of the composites were investigated properly. Also, the density of the composite was reduced up to 21.54%.     

Microcellular Crosslinked Silicone Rubber Foams: Influence of Nucleation Agent (Polyhedral Oligomeric Silsesquioxane) on the Rheological,Vulcanizing, Cell Morphological Properties

A series of microcellular silicone rubber/silica/polyhedral oligomeric silsesquioxane (POSS) foams were prepared by supercritical carbon dioxide. The effect of POSS particles on the rheological behavior, vulcanizing, and cellular morphology of the composites was investigated. The results showed that the POSS grafted carboxylic acid group can improve the matrix strength of silicone rubber. POSS grafted carboxylic acid group act as inhibiting agent in the vulcanizing process. POSS particles play an important role in the microcellular structure formation. When the POSS content was 2.0?wt%, the cell size and cell density can reach to 3.77?µm and 7.99?×?10⁹ cell/cm³, respectively.     

Mechanical Properties of Poly(Butylene Succinate) Reinforced with Continuously Steam-Exploded Cotton Stalk Bast

Poly(butylene succinate) (PBS) was reinforced by cotton stalk bast fibers (CSBF), which had been pretreated by the continuous steam explosion method. The influence of water content in CSBF during the explosion and fiber content on the mechanical properties of CSBF/PBS biocomposites was investigated. The results showed that the incorporation of CSBF decreased the tensile and impact strength, while significantly enhanced the flexural strength, flexural modulus and tensile modulus. The mechanical properties of biocomposites reinforced by exploded fibers were much better than that of the biocomposites reinforced by non-exploded fibers. Biocomposites reinforced by fibers with 40 and 50 wt% water contents during the explosion had the best mechanical properties. The morphology of CSBF and biocomposites was evaluated by SEM, which demonstrated that fibers with 40 and 50 wt% water contents had better separation and rougher microsurfaces, indicating a better adhesion between PBS matrix and fibers.     

Synthesis of Mineral Nanofiller using Solution Spray Method and its Influence on Mechanical and Thermal Properties of EPDM Nanocomposites

Calcium carbonate (CaCO₃) nanoparticles were synthesized by solution spray of CaCl₂ and NH₄HCO₃ with sodium lauryl sulfate (SLS) as a stabilizing agent. Synthesized nano-CaCO₃ of 20 nm and commercial CaCO₃ (40 mircron) were reinforced in EPDM rubber composites of by varying 2–10 wt% of loading. The rubber nanocomposites were prepared on two roll mill and molded on compression molding machine and were subjected to characterizations like mechanical and thermal. The results were then compared with fly ash (10–60 wt%) filled EPDM rubber composites. It was found that with increase in wt% of nano-CaCO₃ loadings the mechanical and thermal properties of EPDM rubber nanocomposites increases drastically. Improvements in properties were due to uniform dispersion of nano-CaCO₃ into the rubber chain. It means that nano-CaCO₃ gets exfoliated within the rubber chains uniformly. It is also due to fine size of nano-CaCO₃ (20 nm) with uniform transfer of heat during vulcanization, which keeps the rubber chains intact on cross-linking. Results of commercial CaCO₃ and fly ash filled EPDM composites were found to be very inferior over nano-CaCO₃ filled EPDM rubber nanocomposites even though the amount of loading nanofiller was less (2–10 wt% of loading) compared to fly ash of 75 micron (10–60 wt%).     

Hollow Fiber Ultrafiltration Membranes from Poly(Vinyl Chloride): Preparation,Morphologies, and Properties

Hollow fiber poly(vinyl chloride) membranes were prepared by using the dry/wet spinning method. Cross-section, internal, and external surfaces of the hollow fibers structure were studied by SEM. The pore size and pore size distribution of the hollow fibers were measured by a PMI capillary flow porometer. UF experiments of pure water and aqueous solution of PVP K-90 were carried out. The effect of the PVC concentration on the hollow fibers mechanical properties was also investigated. It was found that the PVC fibers cross-sectional structure was affected by the polymer concentration in the dope solution. In particular, reduction of macrovoids size was observed when increasing PVC concentration from 15 to 19 wt%. The pore size distribution of the PVC hollow fibers was controlled by adjusting the PVC concentration. Indeed, an increase of PVC concentration up to 19 wt% leads to fibers with sharp pore size distribution (the 99% of pores is about 0.15 µm).The pure water permeation flux decreased from 162 to 128 (l/m² · h · bar), while the solute separation performance increased from 82 to 97.5%, when increasing the PVC concentration. The elongation at break, the tensile strength, and the Young's modulus of the PVC hollow fibers were improved with PVC concentration in dope solution.     

Surface Porosity of Lignin/PP Blend Carbon Fibers

Abstract

The surface porosities of carbon fibers derived from the polymer blend fibers of hardwood kraft lignin, HKL and polypropylene, PP, were discussed using thermal analyses, FTIR, and nitrogen adsorption. HKL/PP carbon fibers were prepared by two‐step thermal processing, thermostabilization, and carbonization. During the thermostabilization process, pores are created by oxidative degradation of the PP component. After thermostabilization some crystalline and highly oxidized PP components remained in the blend fiber. These residual PP components were subsequently pyrolyzed during carbonization, and effectively created a porous structure in the resulting carbon fibers. N₂ adsorption tests of the porous carbon fibers revealed the same type of adsorption/desorption isotherms as for activated carbon fiber. The internal surface area of the HKL/PP = 62.5/37.5 carbon fibers was calculated to be 499 m² g^?1. This value was lower than that for commercial activated carbon, 745 m² g^?1. However, these porous lignin‐based carbon fibers were not activated carbon fibers, which could be relatively easily done through steam activation. Thus, the HKL/PP blend carbon fibers appear to be promising precursors for activated carbon fibers.     

Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

One prominent method of modifying the properties of dielectric elastomers (DEs) is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR) has relatively low viscosity, which is favorable for loading inorganic fillers. In the present study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV) were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability and dynamic viscosity. Filled silicone elastomers with high loadings of nano-sized titanium dioxide (TiO₂) particles were also studied. The best overall performing formulation had 35 wt.% TiO₂ nanoparticles in the POWERSIL® XLR LSR, where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz, breakdown strength of 160 V µm^?1, tear strength of 5.3 MPa, elongation at break of 190%, a Young’s modulus of 0.85 MPa and a 10% strain response (simple tension) in a 50 V μm^?1 electric field was obtained.     

Investigation on kinetics of carbon dioxide absorption in aqueous solutions of monoethanolamine + 1, 3-diaminopropane

ABSTRACT

Environmental concerns from global warming and climate change demand carbon dioxide separation from post-combustion gases. Important parameters are involved in choosing the suitable solvent for carbon dioxide separation, including the reaction rate of carbon dioxide and the solvent. In this paper, the kinetics of carbon dioxide (CO₂) absorption in aqueous solutions of Monoethanolamine (MEA) + 1,3-Diaminopropane (DAP), a diamine containing two primary amino group, was developed. The measurements were performed in a stirred cell with a horizontal gas-liquid interface in the temperature range of 313.15–333.15 K and aqueous solutions of 10 wt% MEA + 5 wt% DAP and 12.5 wt% MEA + 2.5 wt% DAP. Experiments were conducted in an isothermal batch reactor with a horizontal gas-liquid interface under pseudo-first-order conditions, enabling the determination of the overall kinetic rate constant from the pressure drop method. Second-order reaction rate constants of CO₂ absorption in amine solutions were estimated using the calculated initial absorption rate. It was found that the rate constants in MEA+ DAP solutions were greater than in MEA solutions which means that DAP increases the reaction rate.     

The influence of compatibilizers on nitrile-butadiene rubber and polypropylene (NBR/PP) blends

Four kinds of compatibilizers—chlorinated polyethylene (normal CPE), highly chlorinated CPE, maleic anhydride grafted with polypropylene (MP), and chlorinated polypropylene (CPP)—were used to study the influence of compatibilizing agents on the properties of nitrile-butadiene rubber and polypropylene (NBR/PP) blends, a kind of thermoplastic elastomer (TPE). The results show that the most proper amount of normal CPE, highly chlorinated CPE, MP, and CPP are 9, 8, 7, and 6 wt%, respectively, in the NBR/PP blends. The CPP was the best compatibilizer for NBR/PP blends among the four. NBR/PP blends obtained excellent properties of thermoplastic materials and can be molded with the general processing technologies for thermoplastics, such as injection, extrusion, blow molding, and the like. The mechanical properties are similar to that of Geolast, produced by Monsanto Company, and exceed the Chinese national criterion (GB7527-87). The tensile strength was 13.8 MPa; the elongation at break was 290%; and the compression set was 32%. After the blends were immersed in oil for 70 h, the tensile strength was 10.4 MPa, and the degree of oil absorption was 12%. The compatibility of the blends was consistent with the morphology from transmission electron microscopy (TEM).     

The Influence of Dry-Milled Wood Flour on The Physical Properties of Wood Flour/Polypropylene Composites

In this study, we evaluated the influence of wood flour (particle size: <90 μm) on the physical properties of wood flour/polypropylene (PP) composites. Wood flour was obtained by dry ball-milling of forest-thinning material at a rotary speed of 250 rpm for 1, 2, 4, and 8 h. The milled wood flour was filtered using a 90 μm sieve. The water content of the wood flour was adjusted to 5, 10, or 20 wt%. Composite properties, including mechanical properties, water absorption, and thermal expansion, were evaluated at wood flour loadings of 40 wt%. When wood flour with 5 wt% water content was milled for 2 and 4 h, the resulting wood flour was granular rather than fibrous; flocculation of the fine particles was observed for milling times exceeding 4 h. This morphological change in the wood flour reduced its influence on the physical properties of the composites, although some positive influences were observed on the molding properties of the composite, such as an increase in compound fluidity. Milled wood flour with 10 wt% or 20 wt% water content was fibrous. Scanning electron microscopy observation of milled wood flour with 10 wt% water content revealed partial surface fibrillation at widths of tens to hundreds of nanometers. The addition of wood flour with nanoscale surface fibrils to PP composites positively influenced the properties of the composite, resulting in a decrease in the linear coefficient of thermal expansion in the flow direction.     

Enhanced wave-absorbing performances of silicone rubber composites by incorporating C-SnO2-MWCNT absorbent with ternary heterostructure

SnO₂ and amorphous carbon were simultaneously introduced onto the surface of multi-walled carbon nanotube (MWCNT) by a simple and green hydrothermal process followed by heat treatment, finally to obtain the C-SnO₂-MWCNT absorbent with ternary heterostructure. Subsequently, the C-SnO₂-MWCNT/silicone rubber wave-absorbing composites were prepared. XRD, Raman, XPS, SEM, TEM and TGA indicated the C-SnO₂-MWCNT absorbent with ternary heterostructure was fabricated successfully. When the mass fraction of C-SnO₂-MWCNT was 30 wt% and the thickness was 2.65 mm, the minimum reflection loss (RL_min) and effective absorption bandwidth (EAB) of the C-SnO₂-MWCNT/silicone rubber wave-absorbing composites could reach −53.5 dB and 3.16 GHz, respectively. Excellent wave-absorbing performance was due to the synergistic effect of multiple interface & dipole polarization and conduction loss. Furthermore, the corresponding heat resistance index (T_HRI) of the C-SnO₂-MWCNT/silicone rubber wave-absorbing composites with 30 wt% C-SnO₂-MWCNT reached 209.9 °C, higher than that of neat silicone rubber (187.4 °C).     

Effect of ATH content on electrical and aging properties of EVA and silicone rubber blends for high voltage insulator compound

The effect of trihydrated alumina (Al₂O₃, 3H₂O) (ATH) filler in ethylene‐vinyl acetate copolymer (EVA) and silicone rubber blends was investigated by performing a series of laboratory experiments to simulate different natural aging conditions. Samples with varying ATH content in a 50‐50 blend of EVA and polydimethylsiloxane (PDMS) (silicone rubber, MQ) were tested to investigate the tracking resistance, resistance to UV radiation, corona, heat, and water immersion. Changes in surface resistivity, volume resistivity, and hydrophobic characteristics were evaluated for different compounds having ATH content. These exercises were mainly carried out to optimize the filler level. In immersed condition the water absorption increases with ATH content. The recovery of hydrophobicity, after aging by heat, is appreciable at higher ATH levels, than at lower ATH levels. The tracking and erosion resistance decrease as ATH content increases. When compounds containing different ATH content were subjected to corona treatment, the samples with higher ATH levels exhibited better results. All samples changed their color to a darker shade and there was an increase in the hydrophobicity, when subjected to UV radiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3505–3516, 2007     

Effect of hafnium oxide on continuous aluminum oxide-mullite-hafnium oxide composite ceramic fibers

The Al₂O₃-mullite-HfO₂ (AMH) ceramic fiber with a 20 wt% of HfO₂ has demonstrated good tensile strength and good high-temperature stability due to the tiny diameter and small grains even at high temperatures. To investigate the effect of HfO₂ on crystal behavior and high-temperature performance, continuous AMH ceramic fibers with different HfO₂ contents (0 wt%, 10 wt%, and 50 wt%) were prepared by melt-spinning of polymer precursors. The effect of HfO₂ on the crystal form transition process, mechanical properties, and high-temperature resistance of AMH fibers was studied by in-situ XRD and STEM. The AMH fibers with 50 wt% HfO₂ had the highest strength retention rate of 78.33% after heat treatment at 1200 °C for 0.5 h. After 0.5 h of heat treatment at 1500 °C, the grain size of the AMH fibers with 50 wt% HfO₂ was still less than 200 nm.     

超细二氧化硅纤维/橡胶复合材料的结构与性能研究

通过静电纺丝技术制备了直径为300~500 nm的超细二氧化硅纤维,制备的纤维进一步研磨和超声处理得到二氧化硅短纤维,然后将其填充到胎面胶中,分析了不同取向的二氧化硅纤维对胎面胶物理机械性能与动态力学性能的影响。结果表明：二氧化硅纤维在胎面胶基体中有着良好的分散,可以明显提高复合材料的100%定伸模量。在动态性能上,当纤维取向方向与分子链方向一致时,其60~80oC损耗因子最小。当纤维取向方向与分子链方向垂直时,0~-20oC损耗因子最大。因此该二氧化硅纤维作为一种新型增强填料在胎面胶上有着良好的应用前景。     

Microcellular silicone rubber foams: The influence of reinforcing agent on cellular morphology and nucleation

A series of microcellular silicone rubber foams were prepared by supercritical carbon dioxide (scCO₂). The effect of reinforcing agent (silica) on the rheological behavior, cellular morphology and nucleation of silicone rubber composites was investigated. The results show that the silica not only acts as reinforcing agent but also plays an important role in the cellular nucleation. When the content of silica increases from 40 phr to 70 phr, the range of the calculated surface tension of silicon rubber composites/scCO₂ (γ_mix) and radius of the critical nucleus (r*) are 158.95～1,092.74 nN/m and 14.45–99.34 nm, respectively. Meanwhile, aggregated silica has good heterogeneous nucleation as the diameter of aggregated silica particles is approximate to twice r*. The smallest cell diameter and the highest cell density of the silicone rubber foam can reach to 708 nm and 1.02 × 10¹¹ cells/cm³, which indicate that the silicone rubber nanofoams can be obtained by means of the supercritical foaming technology. POLYM. ENG. SCI., 59:5–14, 2019. © 2018 Society of Plastics Engineers