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1.
The aim of this paper is to demonstrate for the first time the technological potential of novel, totally bio-based, binder-free vegetable fiber-composites based on the reed-like plant Typha sp. Binder-free vegetable fiberboards based on Cattails were prepared and their mechanical (flexural modulus of elasticity, flexural strength and water absorption) and surface textural properties were determined. The influence of press time and panel density on the properties was investigated. In contrast to currently known natural fiber composites based on hemp, flax, kenaf or the like annual plants which all require up to 30 wt% of suitable bonding resins, the typha based composites were prepared completely without the addition of any extraneous glue and showed good mechanical performance that clearly exceeded the performance of other natural fiber composites containing low percentages of phenolic binder (15%). Of special interest were the superior surface properties of the typha based panels. Despite the coarse nature of the raw fiber material and the rough texture of the typha based fiber mats, binder-free typha panels showed excellent surface smoothness which makes this novel composite material highly interesting for light-weight applications with high surface quality standards, for example, as powder-coated elements for the automotive and furniture industries.  相似文献   

2.
Natural fiber reinforced polypropylene (PP) biocomposites were fabricated by blending long-and-discontinuous (LD) natural fibers (NF) with LD PP fibers. Firstly, random fiber mats were prepared by mixing NFs and PP fibers using a carding process. Then, heat and pressure were applied to the mats, such that the PP fibers dispersed in the mats melted and flowed out, resulting in the formation of consolidated sheets upon subsequent cooling. The effect of the fiber volume fraction on the mechanical properties of the bio-composites was scrutinized by carrying out tensile and flexural tests and observing the interface between the fiber and matrix. It was observed that the natural LD fiber content needs to be maintained at less than the nominal fiber fraction of 40 % by weight for the composites fabricated using the current method, which is quite low compared to that of continuous or short fiber reinforced composites. The limited fiber fraction can be explained by the void content in the biocomposites, which may be caused by the non-uniform packing or the deficiency of the matrix PP fibers.  相似文献   

3.
Polyethylene terephthalate (PET)/biomedical polyurethane (BPU) composite nanofibers with modulated mechanical properties are electrospun by varying the weight ratios of PET and BPU polymers in the mixture. The effect of BPU content on the morphology, porosity, thermal properties, and crystalline structures are systematically investigated. It is shown that uniform PET/BPU nanofibers can be formed through optimization. When the content of BPU is low (0?C7 %), better elongation of the nanofibrous mats is obtained with the increase of BPU content, whereas further increasing the BPU polymer (up to 15 %) results in a decreased breaking elongation as well as the mechanical strength of composites. The formed nanofibrous mats may find potential applications in tissue engineering and vascular graft.  相似文献   

4.
In this work, PA-6 core and PMMA shell composite nanofiber mats together with pure PMMA and PA-6 nanofibrous membranes were obtained through electrospinning. Two kinds of transparent composites were fabricated by hot pressing multilayers of the composite nanofiber mats and of the interlaced pure PA-6 with PMMA nanofibrous membranes, respectively, under the same processing condition and with the same amount of PA-6 nanofiber content. Tensile properties and visible light transmittances of the two transparent composites were characterized. It has been found that both the tensile behavior and the visible light transmittance of the composites obtained from the composite nanofiber mats were better than the counterparts from the interlaced pure PA-6 and PMMA nanofibrous membranes. With a minor loss of less than 10 % in the transparency, a maximal increase of around 20 % in the tensile modulus and tensile strength has been recognized for a transparent composite from the composite nanofibers. Although less efficient, the tensile strengths of the composites from the interlaced nanofibrous membranes were all higher than that of a transparent panel processed from the pure PMMA nanofibers.  相似文献   

5.
Eleven laboratory‐scale trials were undertaken in different years where ryegrass (Lolium perenne L.) or lucerne (Medicago sativa L.) were ensiled with different concentrations of tannin extracts (quebracho, Schinopsis balansae Engl., mimosa, Acacia mearnsii DE WILD.), and the effects on protein degradation were assessed. The dry‐matter (DM) content in grass silages ranged between 186 and 469 g/kg and in lucerne silages between 187 and 503 g/kg. Tannin extract, either quebracho or mimosa, was applied at 0–30 g/kg forage DM. Commercial additives such as Lactobacillus plantarum, formic acid or hexamine + NaNO2 were applied in two of the grass trials and in six of the lucerne trials. Eight of the trials incorporated a maximum ensiling duration of 90 or 180 days in addition to replicates which were opened and evaluated at earlier stages. All trials included silages which were assessed after at least 49 days of anaerobic storage. The crude protein (CP) fraction A (non‐protein nitrogen, NPN) as proportion of total CP, served as the main indicator for proteolysis. In ryegrass, in general, the level of proteolysis was lower than in lucerne. A correlation of DM content in silages and degree of proteolysis was only evident for ryegrass. In both forages, the degradation of true protein slowed considerably after 24 days of ensiling. True protein was conserved most with the highest level of tannin extract addition. However, in lucerne, the combination of formate with lactobacilli was equally effective up to 330 g DM/kg, and deamination was further inhibited by formic acid compared to tannin extracts.  相似文献   

6.
Twenty first century has witnessed remarkable achievements in green technology in material science through the development of biocomposites. Oil palm fiber (OPF) extracted from the empty fruit bunches is proven as a good raw material for biocomposites. The cellulose content of OPF is in the range of 43%–65% and lignin content is in the range of 13%–25%. A compilation of the morphology, chemical constituents and properties of OPF as reported by various researchers are collected and presented in this paper. The suitability of OPF in various polymeric matrices such as natural rubber, polypropylene, polyvinyl chloride, phenol formaldehyde, polyurethane, epoxy, polyester, etc. to form biocomposites as reported by various researchers in the recent past is compiled. The properties of these composites viz., physical, mechanical, water sorption, thermal, degradation, electrical properties, etc. are summerised. Oil palm fiber loading in some polymeric matrices improved the strength of the resulting composites whereas less strength was observed in some cases. The composites became more hydrophilic upon addition of OPF. However treatments on fiber surface improved the composite properties. Alkali treatment on OPF is preferred for improving the fiber–matrix adhesion compared to other treatments. The effect of various treatments on the properties of OPF and that of resulting composites reported by various researchers is compiled in this paper. The thermal stability, dielectric constant, electrical conductivity, etc. of the composites improved upon incorporation of OPF. The strength properties reduced upon weathering/degradation. Sisal fiber was reported as a good combination with OPF in hybrid composites.  相似文献   

7.
Partially acetylated softwood kraft lignin (ASKL) is used as filler in synthetic polymers such as LDPE, PP, PS and PET. ASKL/synthetic polymer composites are prepared by melt-blending and compression molding with ASKL content up to 50.0 wt%. The chemical and physical properties of ASKL/synthetic polymer composites are also investigated. TGA results show that ASKL is more thermally stable than SKL up to 200 °C. FTIR spectra demonstrate a formation of free volume by crystallization of LDPE in ASKL/LDPE composite. DSC results show that the glass transition temperature of ASKL decreased by acetylation, and ASKL/synthetic polymer composites (50/50 w/w) have a single glass transition. The AFM images of ASKL/synthetic polymer composites show no significant phase separation. Young’s moduli of ASKL/synthetic polymer composites increased with ASKL content in some extents. Tensile strength and breaking strain of ASKL/PET composite are almost retained in spite of the addition of ASKL as a result of a contraction in free volume or densification.  相似文献   

8.
There have been many interests in using natural fibers as substitutes for glass fibers to prepare fiber reinforced composites. Flax fibers, due to their specific strength, have been a hot issue in this field. The focus of this research work is to manufacture flax fiber reinforced low melting point PET composites directly from nonwoven mats. No consolidation methods are applied to the carded nonwoven mats before the hot-press molding. The effects of operating parameters like carding method, molding temperature, molding time, etc. on the mechanical properties of composites have been investigated. Results show it is a facile and cost-saving method to produce composites specifically in the application areas like automobile interior ornament and decoration materials, etc.  相似文献   

9.
In recent years, composites based on glass fiber reinforced polymer have been widely used in order to meet increasing durability and safety regulations, particularly in the power cable, automotive and plane industry. In this paper, mechanical and electrical properties of high density polyethylene (HDPE) and HDPE containing glass fiber polymer composites were investigated and compared at different temperatures. Composite materials were prepared with the hot pressing method. Tensile strength, % elongation and the modulus of elasticity (or Young’s modulus) were determined for each sample at different temperatures. In addition to this, at different temperatures τ σ and τ E have mechanical and electrical lifetime respectively, corresponding to mechanical tension (σ) and electrical strength (E), and this was investigated for each sample. As compared to the mechanical and electrical properties of neat HDPE, HDPE/0.5 % glass fiber composites have been found to have better mechanical and electrical durability.  相似文献   

10.
This paper presents the results of a current research of the tensile properties: ultimate strength and stiffness modulus in composites using natural reinforcements. Hemp short fibres and pine sawdust were randomly distributed in polypropylene matrices to produce composite plates with 5 mm thickness by injection moulding technique. The specimens were cut from these plates with bone dog shape or plane bars, and tested in tensile and four points bending, respectively. Stiffness modulus and ultimate stresses were obtained for different weight fraction content of reinforcement and discussed taking in account the failure modes. Four series of pine sawdust reinforced specimens were immersed in water in periods up to 20 days. Periodically, the specimens were removed from the water recipient and immediately tested. The damage effect of water immersion time was discussed based in the tensile results and in the water absorption curves.  相似文献   

11.
The aim of this work is to demonstrate the performances of cornstarch–quebracho tannin-based resins designed as adhesive in the plywood production. In this way, the cornstarch and quebracho tannin was introduced in the classic adhesive formulation in order to supply a part of phenol–formaldehyde (PF). The physical properties (rheological characterization, thermogravimetric analysis and solid phase 13C NMR analysis) of the formulated resins were measured. In order to evaluate the mechanical performances of optimal cornstarch–quebracho tannin-based resins, plywood panels were produced and mechanical properties were investigated. These mechanical properties included tensile strength, wood failure and 3-point bending strength. The performance of these panels is comparable to those of plywood panels commercial PF made.The results showed that plywood panels bonded with cornstarch–quebracho tannin–PF resins (15:5:80, w/w/w) exhibited better mechanical properties than plywood panels commercial PF made. The introduction of small proportions of cornstarch and quebracho tannin in PF resins contributes to the improvement of the boiling water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with cornstarch–quebracho tannin–PF were lower to those obtained from panels bonded with control PF. Solid state CPMAS NMR spectra indicates that no reaction at all between PF resins and cornstarch and quebracho tannin. Even when reaction does evidently not occur, the addition of cornstarch and quebracho tannin improves markedly the water resistance of PF resins.  相似文献   

12.
Maleated graft polyolefins as cross-linking agents (CAs) are widely used to improve properties of wood thermoplastic composites made by melt extrusion process. In this study, novel CAs, free isocyanate group (NCO)-terminated urethane pre-polymers (UPs) were synthesized and used in manufacturing wheat straw (WS)/recycled polyethylene (PE) composites. The composites using polymeric diphenylmethane diisocyanate (pMDI) as a CA were also made in comparison. The relationship between composite properties and the level of CA and its content as well as the composite density and hot pressing time were investigated based on wood based board processes. The results show that the internal bonding (IB) strength, the IB after soaked in boiling water for 2 h (2hWIB), the modulus of rupture (MOR), the modulus of elasticity (MOE) and the 24 h thickness of swell after absorption of water (24hTS) of the composites are significantly improved with increased CA contents and composite densities. The optimal hot pressing time is 1.1 min/mm at 180°C. The cross-linking function is attributed to the reaction between free NCOs of CA molecules with hydroxyls of WS and the moisture in the raw materials, as well as the interaction between weak polar chain segments in the CA molecules to the non-polar PE. It is highly feasible to manufacture high quality composite using WS and recycled PE as raw materials when cross-linked with just 2.5% of UPs.  相似文献   

13.
In this work, the effect of organosolv lignin on properties of polypropylene (PP)/chitosan composites was investigated. Mechanical and thermal properties of the composites were analyzed by means of ASTM D 638-91, ASTM D 256, thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Tensile strength and elongation at break of the PP composites decreased upon the presence of chitosan filler, but Young’s modulus improved. Impact strength was found to increase with the maximum value at 30 php of filler loading. At a similar loading, treated PP/chitosan composites were found to have higher tensile strength, elongation at break, Young’s modulus as well as impact strength than untreated composites. Furthermore, the presence of organosolv lignin imparted a plasticizing effect. Thermal properties of the treated PP/chitosan composites were better as compared with the untreated PP/chitosan composites; although the chemical treatment did not alter the thermal degradation mechanism. In addition, the obtained results were comparable to results from previous studies. This finding implied that the organosolv lignin could be a potential reagent to replace its synthetic counterpart.  相似文献   

14.
The Acacia mangium tree contains 10% bark (v/v), of which about 20% are extractives. Extraction of this bark using a combination of water and sulfite medium can produce between 15% and 25% tannin materials (dry weight). In this work, several extraction conditions such as bark size, plantation site, extraction time and extraction medium were studied. The results showed that by using either hot water or a sulfite medium, a reasonable amount of tannin yield can be obtained. Bark size of less than 1-mm mesh size gave relatively high tannin yield irrespectively of the extraction medium used. Using a 600:100:2:0.5 (w/w) ratio of water:bark:sodium sulfite:sodium carbonate, and reacted at 75 °C for 3 h improved the tannin yield by at least 30%. The extracts were reasonably reactive towards formaldehyde as shown by their high Stiasny number; water extract, 60–70% and aqueous sulfite–carbonate extracts, 85–90%. The gluing results showed that the shear strength of the plywood can meet the requirements of the European Standards EN 314-1 and EN 314-2:1993. Incorporation of low molecular weight PF resin (10 parts) and PF (10 parts) improved the shear strength from 0.96 MPa to 1.43 MPa after a 72 h boiling test. This study showed that A. mangium tannin blended with commercial plywood phenol–formaldehyde resin, low molecular weight PF and paraformaldehyde as a cross-linker can be used to bond Kedondong (Canarium spp.) wood veneers suitable for both interior and exterior grade plywood.  相似文献   

15.
Mechanical properties of rice straw fiber-reinforced polymer composites   总被引：1，自引：0，他引：1  
Rice straw fibers have been used as reinforcing fillers in different polymers, tow composites were prepared by using polyvinyl alcohol and polystyrene polymers with different ratio of polymers. The pressed samples were subjected to various electron beam irradiation dose. The results indicated that, flexural strength, impact strength and modulus of elasticity increase with increasing the polymer ratio in the mix composition. It was found that the water absorption and thickness swelling percentages of rice straw fiber polystyrene composites decrease with increasing the polystyrene content in the same composition, while its values for rice straw polyvinyl alcohol composites improve. These are attributed to hydrophobic and hydrophilic characteristics of the tow composites. The improvement of physico-mechanical properties of both composites with the increase of electron beam irradiation dose are probably attributed to randomly initiated chain reactions, which started by the reactive centers created by electron beam. These observations were confirmed by IR spectrometer and SEM studies.  相似文献   

16.
Tannin based rigid foams are structures in which flavonoids are randomly cross-linked with furanic units throughout covalent bonds. The use of these aromatic substrates from natural materials to trap some heavy metal ions dissolved in water solutions is described. Interesting results have been achieved using different mimosa bark tannin (Acacia mearnsii formerly mollissima, De Wildt) and pine bark tannin (Pinus radiata) mixed foams. Capability to catch Pb2+ and Cu2+ ions at different concentrations has been verified throughout ICP-OES analysis of the foams. A reliable proportionality has been found between initial concentration and percentage of metal ions adsorbed. These foams were able to adsorb up to 12.5% of Cu(II) and 20.1% of Pb(II) with respect to the concentration of these ions in solution.  相似文献   

17.
The ligno-cellulose natural fabric from the polyalthia cerasoides tree was analyzed by FTIR, chemical, X-ray and thermo gravimetric methods. The morphology of the fibers was studied by scanning electron and polarized optical microscopic methods. The tensile properties were also studied. The effect of alkali treatment on the properties of the fabric was studied. The FTIR and chemical analyses indicated lowering of hemi-cellulose and lignin content on alkali treatment of the fabric. The tensile properties were found to increase on alkali treatment. The x-ray diffraction revealed an increase in crystallinity of the fabric on alkali treatment. The thermal stability of the fabric was also found to increase on alkali treatment. The properties of this fabric were compared with those of two natural fabrics reported in the literature. This uniaxial fabric has sufficient tensile modulus and can be used as reinforcement in the development of green composites.  相似文献   

18.
This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical properties (ash, lignin and cellulose contents). A laboratory experiment was designed with five fiber filler treatments, namely control (oak wood fiber as the filler - OWF), cotton burr and sticks (CBS), CBS with 2% (by weight) second cut linters (CBL), CBS with 30% (by weight) guayule whole plant (CGP), and CBS with 30% (by weight) guayule bagasse (CGB). The composite samples were manufactured with 50% of fiber filler, 40% of virgin high-density polyethylene (HDPE), and 10% other additives by weight. The samples were extruded to approximately 32 × 7 mm cross-sectional profiles, and tested for physico-mechanical properties. The CBS and CBL had considerably lower bulk density than the other fibers. Cotton linters had the highest α-cellulose (66.6%), and lowest hemicellulose (15.8%) and lignin (10.5%) of all fibers tested. Guayule whole plant had the lowest α-cellulose and highest ash content. Both CBS and guayule bagasse contained α-cellulose comparable to OWF, but slightly lower hemicellulose. Evaluation of composite samples made from the five fiber treatments indicated that fibers from cotton gin byproducts and guayule byproducts reduced the specific gravity of the composites significantly. However, the CBS and CBL samples exhibited high water absorption and thickness swelling, but the addition of guayule bagasse reduced both properties to similar levels as the wood fiber. The CGP exhibited significantly lower coefficient of thermal expansion. Composite samples with the five different fiber fillers showed similar hardness and nail holding capacity, yet oak fibers imparted superior strength and modulus under flexure and compression with the exception of the compressive modulus of CGB composites. In general, both cotton ginning and guayule processing byproducts hold great potential as fiber fillers in thermoplastic composites.  相似文献   

19.
A series of flexible and tough polyimide (PI) microfibrous mats (PI-1~PI-4) have been prepared via the one-step electrospinning procedure with the organo-soluble PI resins as the starting materials. For this purpose, four PI resins were first synthesized by the chemical imidization reaction from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and four aromatic diamines containing rigid-rod moieties in their molecular skeletons, respectively. The PI resins derived from 6FDA and aromatic diamines, including PI-1 from 2-(4-aminophenyl)-5-aminobenzimidazole (APBI), PI-2 from 2-(4-aminophenyl)-5-aminobenzoxazole (APBO), PI-3 from 4,4′-diaminobenzanilide (DABA), and PI-4 from 2-chloro-4,4-diaminobenzanilide (Cl-DABA) exhibited good solubility in polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Flexible and tough microfibrous mats were successfully prepared by a one-step electrospinning procedure from the PI/DMAc solution (solid content: 15–20 wt%; absolute viscosity: 8000–10000 mPa·s). The derived PI mats exhibited good whiteness according to the CIE Lab measurements with W (whiteness) values as high as 94.31, L (lightness) values higher than 94.00, b* (yellowness) values as low as 2.98 and yellow indices (YI) as low as 4.87. In addition, the prepared PI mats exhibited excellent thermal and dimensional stability with the glass transition temperatures (Tg) higher than 345 °C and linear coefficients of thermal expansion (CTE) as low as 27.8×10-6 /K.  相似文献   

20.
Natural fibers are largely divided into two categories depending on their origin: plant based and animal based. Plant based natural jute fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated by compression molding. Bending strength (BS), bending modulus (BM), tensile strength (TS), Young’s modulus (YM), and impact strength (IS) of the composites were found 44.2 MPa, 2200 MPa, 41.3 MPa, 750 MPa and 12 kJ/m2, respectively. Animal based natural B. mori silk fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated in the same way and the mechanical properties were compared over the silk based composites. TS, YM, BS, BM, IS of silk fiber reinforced polypropylene composites were found 55.6 MPa, 760 MPa, 57.1 MPa, 3320 MPa and 17 kJ/m2 respectively. Degradation of composites in soil was measured upto twelve weeks. It was found that plant based jute fiber/PP composite losses its strength more than animal based silk fiber/PP composite for the same period of time. The comparative study makes it clear that mechanical properties of silk/PP composites are greater than those values of jute/PP composites. But jute/PP composites are more degradable than silk/PP composites i.e., silk/PP composites retain their strength for a longer period than jute/PP composites.  相似文献   

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