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1.
Pyrolyzed oil shale (POS) obtained from the pyrolysis of bituminous rock was used as filler in poly(ethylene‐co‐vinyl acetate) (EVA). The effects of the VA content of EVA and the particle size of POS on the mechanical properties were investigated. The composites were prepared in a rotor mixer at 180°C with a concentration of POS of up to 30 wt %. The stress–strain plots of the compression‐molded composites are similar to the EVA (18% VA content) behavior for low concentrations (1–5 wt %) of POS with a particle size lower than 270 mesh. It was observed that decreasing the POS particle size and increasing the VA content of EVA produced better compatibility between the polymer and filler. The mechanical properties, differential scanning calorimetry, and dynamic mechanical analysis also demonstrated the compatibility between EVA and POS under the increase of the VA content in the EVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1544–1555, 2002; DOI 10.1002/app.10494  相似文献   

2.
This investigation focuses on the preparation of bio‐based composites from recycled poly (ethylene terephthalate) (PET) and sisal fibers (3 cm, 15 wt %), via thermopressing process. Plasticizers derived from renewable raw materials are used, namely, glycerol, tributyl citrate (TBC) and castor oil (CO), to decrease the melting point of the recycled PET (Tm ∼ 265°C), which is sufficiently high to initiate the thermal decomposition of the lignocellulosic fiber. All used materials are characterized by thermogravimetric analysis and differential scanning calorimetry, and the composites are also characterized via dynamic mechanical thermal analysis. The storage modulus (30°C) and the tan δ peak values of CT [PET/sisal/TBC] indicate that TBC also acts as a compatibilizing agent at the interface fiber/PET, as well as a plasticizer. To compare different processing methods, rheometry/thermopressing and compression molding are used to prepare the recycled PET/sisal/glycerol/CO composites. These two different methods of processing show no significant influence on the thermal properties of these composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40386.  相似文献   

3.
In this study, tri-layered composites were prepared by reinforcing poly-lactic acid (PLA) nano-hydroxyapatite (n-HA) (1 and 5 wt%) and 20 mol% continuous phosphate glass fibers (PGF). Initially, the effect of addition of 1 and 5% n-HA on the structural, thermal, mechanical, and thermo-mechanical properties of 100% PLA was investigated. With 5 wt% n-HA addition the tensile modulus (TM), flexural modulus (FM), tensile strength (TS), and flexural strength (FS) of 100% PLA was improve by 14.9, 47.4, 6, and 32.9%, respectively. Whereas, the un-notched impact strength of the nanocomposites suffer 2% deterioration. However, T g decreased by 0.3°C and T c increased by 10°C as 5 wt% n-HA was added to 100% PLA. Afterwards, the 5% n-HA/PLA composite were reinforced with 20 mol% continuous PGF and the TM, FM, TS, and FS of the tri-layered composites were 162.6, 412.5, 28.4, and 157.4% higher as compared to 100%PLA. Furthermore, the storage modulus of the 1% n-HA-filled composites was 500 MPa lower than 100%PLA, while 5 wt% n-HA-filled composites showed similar storage modulus as 100% PLA. 5 wt% n-HA-filled composite showed the highest peak of loss modulus which may be attribute to the chain segment of PLA matrix after the incorporation of HA. Thus, n-HA and PGF reinforcement resulted in improved mechanical properties of the composites and have great potential as biodegradable bone fixation device with enhanced load-bearing ability.  相似文献   

4.
《Polymer Composites》2017,38(7):1462-1473
Poly(ethylene‐co‐vinyl alcohol)/carbon black (EVOH/CB) composites were prepared by a solvent‐casting saponification (‐D) and precipitation saponification (‐P) methods with a poly(ethylene‐co‐vinyl acetate)/CB (EVA/CB) toluene suspension. The effects of the CB content and saponification time on the morphology, electrical resistivity, thermal, and mechanical properties of EVA/CB composites were examined. The volume resistivity (ρ v) of the EVA/CB‐D and EVA/CB‐P samples decreased significantly with increasing CB content and the percolation threshold of such composites was determined about 10 wt%. At 10 wt% of CB content, the ρ v of EVA/CB‐D composite decreased significantly with the saponification time, whereas ρ v of EVA/CB‐P composites did not change. As the saponification time increased, EVA/CB25wt% composites form cavity structure which CB is usually located in oval cavities larger than the particles themselves. This oval cavity structure almost resembles extruded high‐density polyethylene (HDPE)/CB composites. The morphology and PTC behavior of prepared composites were compared with those of HDPE/CB and the mechanism of PTC and NTC effects was discussed. POLYM. COMPOS., 38:1462–1473, 2017. © 2015 Society of Plastics Engineers  相似文献   

5.
The conductive blend consisting of ethylene‐vinyl acetate (EVA) and a polyaniline/p‐toluene sulfonic acid (PAn/TSA) complex were prepared by a thermal doping process using a Brabender plasticorder at 150°C. The conductivity, dielectric constant, dissipation factor, mechanical behavior, and structural aspects of these blends were investigated. A higher percentage of the PAn/TSA complex in the EVA matrix resulted in an increase in the electrical properties and a decrease in the mechanical properties like the tensile strength and percentage of elongation. These results were compared with the microcrystalline parameters of the blend obtained from X‐ray profile analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1730–1735, 2002  相似文献   

6.
The transport behavior of O2 and N2 were studied for series of physical blends of PVC with EVA having different vinyl acetate (VAc) contents in the EVA (45 and 65 wt-%) and using different milling temperatures (160° and 185°C). The polymer blends were further characterized by dynamic mechanical measurements, density measurements, and x-ray diffraction. At higher VAc content in EVA and with higher milling temperature, the rate of permeation (P) and the rate of diffusion (D) decrease, and the activation energy of D (from Arrhenius plots) increases. Furthermore, the experimental density values of PVC/EVA-45 blends agree well with calculated values, assuming volume additivity of the two components, while those of PVC/EVA-65 blends are higher than the calculated densities. These results are interpreted as due to denser packing of polymer molecules and increased PVC-EVA interaction at higher VAc content and with higher milling temperature, indicating better compatibility between the blend components. The x-ray diffraction data give no evidence of crystallinity. Sharp increases in P and D values at about 7.5% EVA (by weight) are found for PVC/EVA-45 blends (in agreement with our previous work) but not for PVC/EVA-65 blends. This is interpreted as due to a phase inversion at increasing EVA content in the former blends but not in the latter blends. The dynamic mechanical measurements show that the PVC/EVA-65 blends milled at 160°C behave largely as semicompatible systems with maximum interaction between the two polymers at compositions of about 50/50 by weight.  相似文献   

7.
In this study, 65 wt% aligned untreated long hemp fibre/epoxy (AUL) and aligned alkali treated long hemp fibre/epoxy (AAL) composites cured at 70°C using compression moulding were subjected to accelerated weathering using an accelerated weathering chamber with UV-irradiation and water spray at 50°C for four different time periods (250, 500, 750 and 1000 h). After accelerated weathering, tensile strength (TS), flexural strength, Young's modulus (YM), flexural modulus and fracture toughness (K Ic) were found to decrease and impact energy (IE) was found to increase for both AUL and AAL composites. AUL composite had greater overall reduction in mechanical properties than that for AAL composite upon exposure to accelerated weathering environment. FTIR, TGA and WAXRD analyses of the accelerated weathered composites support the results of the deterioration of mechanical properties upon exposure to accelerated weathering environment.  相似文献   

8.
Composites of poly(3‐hydroxybutyrate), P(3HB), and starch were prepared by solution casting technique. To improve adhesion of starch to P(3HB), stearic acid was added as a compatibilizer and glycerol as a plasticizer. The water resistance, mechanical, and biodegradable properties of the P(3HB)/starch composites were studied. Diffusion and penetration coefficients of water increased with increasing starch content in the composites. The results showed that the elastic modulus and strain at rupture of the P(3HB)/starch composites were enhanced by increasing starch content upto 10 wt % and the tensile strength increased from 21.2 to 93.9 MPa. The presence of starch content higher than 10 wt % had an adverse effect on the mechanical properties of the investigated composites. The biodegradation rate using Actinomycetes increased proportionally to the starch content in the composite and accelerated in a culture medium of pH ≈ 7.0 at 30°C. Enzymatic degradation experiments showed that lipase produced by Streptomyces albidoflavus didnot degrade P(3HB)/starch composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

9.
Many biopolymers and synthetic polymers composites were developed by different researchers for environmental protection and for cost reduction. One of these composites is polycaprolactone (PCL) and vital wheat gluten or wheat flour composites were prepared and compatibilized with polymeric diphenylmethane diisocyanate (pMDI) by blending and compression‐molding. PCL/pMDI blend exhibited glass transition (Tg) at ?67°C (0.20 J/g/°C) and vital gluten at 63°C (0.45 J/g/°C), whereas no Tg was recorded for wheat flour. Although Tg was unmistakable for either PCL or gluten, all composite exhibited one Tg, which is strong indication of interaction between PCL and the fillers. Several samples amongst the blended or compression‐molded composites exhibited no Tg signifying another confirmation of interaction. The ΔH of the endothermic (melting) and the exothermic (crystallization) for PCL was decreased as the percentage of gluten or flour increased, whereas the overall ΔH was higher for all composites compared to the theoretical value. The presence of pMDI appeared to strengthen the mechanical properties of the composites by mostly interacting with the filler (gluten or flour) and not as much with PCL. The FTIR analysis ruled out covalent interaction between PCL, pMDI, or the fillers but suggested the occurrence of physical interactions. Based on the data presented here and the data published earlier, the presence of pMDI did not change the nature of interaction between PCL and gluten, but it improved the mechanical properties of the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

10.
The synthesis of a series of graphite fiber-polyacrylamide composites was performed electrochemically in dilute sulfuric acid (0.125M)-acrylamide (2M) solution, 1 : 1 sulfuric acid (0.25M) : acetone-acrylamide (2M) solution, and 1 : 1 sulfuric acid (0.25M) : 2-propanol-acrylamide (2M) solution, respectively, using graphite fiber bundles as the working electrode. The graphite fiber-polyacrylamide composites, synthesized in a 1 : 1 2-propanol : sulfuric acid-acrylamide solution, were more easily characterized than those synthesized from the sulfuric acid-acrylamide solution that contained no alcohol. Composites that were synthesized in a dilute sulfuric acid solution were, however, more readily crosslinked. (Fourier transform infrared spectroscopy, FTIR, confirmed the formation of inter-chain and intrachain imide functional groups after the resin was cured at ≈ 200°C.) Polymer weight gain analysis, coupled with surface morphology studies using scanning electron microscopy, showed that the thickness of the coatings, and hence the volume fraction of the resin in the composites, varied linearly with the time of electropolymerization. Scanning electron microscopy revealed an open and folded chain surface structure, which permitted unrestricted permeation of the monomer onto the electrode surface. Differential scanning calorimetry of the electropolymerized resins confirmed a glass transition temperature of between 180 and 207°C. © 1994 John Wiley & Sons, Inc.  相似文献   

11.
The mechanical properties, flame retardancy, hot‐air ageing, and hot‐oil ageing resistance of ethylene‐vinyl acetate rubber (EVM)/hydrogenated nitrile‐butadiene rubber (HNBR)/magnesium hydroxide (MH) composites were studied. With increasing HNBR fraction, elongation at break and tear strength of the EVM/HNBR/MH composites increased, whereas the limited oxygen index and Shore A hardness decreased slightly. Hot‐air ageing resistance and hot‐oil ageing resistance of the composites became better with increasing HNBR fraction. Thermal gravimetric analysis results demonstrated that the presence of MH and low HNBR fraction could improve the thermal stability of the composites. Differential scanning calorimeter revealed that the glass transition temperature (Tg) of the composites shifted toward low temperatures with increasing HNBR fraction, which was also confirmed by dynamic mechanical thermal analysis. Atomic force microscope images showed MH has a small particle size and good dispersion in the composites with high HNBR fraction. The flame retardancy, extremely good hot‐oil ageing, and hot‐air ageing resistance combined with good mechanical properties performance in a wide temperature range (?30°C to 150°C) make the EVM/HNBR/MH composites ideal for cables application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

12.
《国际聚合物材料杂志》2012,61(3-4):117-132
Abstract

The dynamic mechanical properties of ethylene vinyl acetate (EVA) rubber filled with different loadings of carbon black and at different degrees of crosslinking were studied over a wide range of temperatures (-150° to +200°C). The loss tangent (tan δ) versus temperature plots indicated presence of different transitions. The α-transition (or the glass-rubber transition) corresponding to the maximum in tan δ value, occurred at ?17°C, which is the principal glass-transition temperature (abbreviated as T g) of EVA rubber. The γ-transition occurred in the temperature region of ?125° to ?135°C, while the β-transition appeared as a shoulder in the temperature region of ?65° to ?75°C. Besides, there was also a high tempeature transition around +62°C which is known as liquid to liquid transition (T 1.1). Incorporation of carbon black filler did not cause any shift of T g, while the tan δ peak values at T g decreased sequentially with increase in filler loading. The γ- and β-relaxations were found to be insensitive to filler loading. The T 1.1 transition, however, was found to be suppressed by incorporation of carbon black filler particularly at high loading. Extent of crosslinking did not influence the T g But, the T 1.1 transition, which was prominent with the lightly crosslinked system was found to be suppressed at high level of crosslinking. Strain dependent dynamic mechanical properties under isothermal conditions showed that the secondary structure breakdown of carbon black filler under the effect of strain amplitude is influenced by the degree of crosslinking of EVA rubber.  相似文献   

13.
To identify effects of glass bead (GB) content on the dynamic mechanical properties of filled low‐density‐polyethylene (LDPE) composites, the storage modulus, loss modulus, glass transition temperature, and mechanical damping of these composites were measured using a Du Pont dynamical mechanical analysis instrument in temperature range from ?150 to 100°C. It was found that the storage modulus increased nonlinearly with an increase of the GB volume fraction. On the basis of Eshelby's method and Mori's work, an equation describing the relationship between the relative storage modulus (ER) and filler volume fraction for polymeric composites was proposed, and the ER of LDPE/GB composites were estimated by means of this equation at temperatures of ?25, 0, and 25°C, and the calculations were compared with the experimental data, good agreement was showed between the predictions and the measured data. Furthermore, this equation was verified by the experimental from Al(OH)3 filled EPDM composites at glassy state reported in a reference. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

14.
Ethylene–propylene–diene rubber (EPDM)/samarium borate (SmBO3)/ethylene‐vinyl acetate (EVA) copolymer and EPDM/antimony‐doped tin oxide (ATO)/EVA composites are aged at 150°C for different intervals. Surface modification is used to improve filler to matrix interphase. The main aim is to investigate the effect of filler type and vinyl acetate (VA) content in EVA on stability of EPDM composites. It is found that acidic ATO particles can lower pH level of EPDM composites and then promote the degradation of acetic acid during aging. Moreover, when VA content exceeds 14 wt %, the instable VA content causes more acetic acids escape during aging. With the increasing of aging time, EPDM/SmBO3 control and EPDM/SmBO3/EVA composites tend to become darker while EPDM/ATO and EPDM/ATO/EVA composites would become yellow. And the color change is correlated well with the variation of carbonyl index. The chemical crosslink points prevent crystals in EVA from melting at aging temperature (150°C), and the variation of crosslink density influences the crystallinity during aging. The tendency of tensile strength is well consistent with that of swelling ratios, and electric properties are correlated with increased polar groups and crystallinity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

15.
The flame retardancy and mechanical properties of ethylene vinyl acetate (EVA) polymer nanocomposite based on magnesium hydroxide (MH) nanoparticles with lamellar‐shape morphological structures and synergistic agent microcapsulated red phosphorus (MRP) have been studied by limiting oxygen index (LOI), cone calorimeter test (CCT), UL‐94 test, tensile strength (TS), and elongation at break (EB). Results showed that LOI values of lamellar‐like nanosized MH (50 × 350 nm2) samples were 1–7 vol. % higher than those of the common micrometer grade MH (1–2 μm) in all additive levels. When 1–3 phr MRP substituted for nanosized MH filler, LOI value increased greatly from original 37 to 55, and met the V‐0 rating in the UL‐94 test. The values of TS for MH nanoparticles composites increased from 10.4 to 17.0 MPa as additive loading levels increased from 80 to 150 phr, respectively, while the corresponding values for common micrometer MH composites decreased steadily from 9.7 to 7.1 MPa. Thermogravimetric analysis (TGA) and dynamic Fourier‐transform infrared spectroscopy (FTIR) results revealed two‐step flame‐retardant mechanism. First, MH particles decompose endothermically with the release of 30.1% hydration water in the 320–370°C temperature range. Second, MRP promote the formation of compact charred layers slowly in the condensed phase in the 450–550°C temperature range. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

16.
The compatibility of low‐density polyethylene and poly(ethylene‐co‐vinyl acetate) containing 18 wt % vinyl acetate units (EVA‐18) was studied. For this purpose, a series of different blends containing 25, 50, or 75 wt % EVA‐18 were prepared by melt mixing with a single‐screw extruder. For each composition, three different sets of blends were prepared, which corresponded to the three different temperatures used in the metering section and the die of the extruder (140, 160, and 180°C), at a screw rotation speed of 42 rpm. Blends that contained 25 wt % EVA‐18 were also prepared through mixing at 140, 160, or 180°C but at a screw speed of 69 rpm. A study of the blends by differential scanning calorimetry showed that all the prepared blends were heterogeneous, except that containing 75 wt % EVA‐18 and prepared at 180°C. However, because of the high interfacial adhesion, a fine dispersion of the minor component in the polymer matrix was observed for all the studied blends with scanning electron microscopy. The tensile strengths and elongations at break of the blends lay between the corresponding values of the two polymers. The absence of any minimum in the mechanical properties was strong evidence that the two polymers were compatible over the whole range of composition. The thermal shrinkage of the blends at various temperatures depended mainly on the temperature and EVA‐18 content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 841–852, 2003  相似文献   

17.
A series of ethylene vinyl acetate‐polyaniline (98/02, 95/05, 93/07, … … 50/50) (EVA‐PAni) blends were prepared by the emulsion polymerization technique and made into sheets by the compression molding at 150°C. These sheets were characterized by electrical, physico‐mechanical, thermal, X‐ray and morphological studies. All electrical properties of EVA‐(PAni)TSA blends increased with an increase in PAni content. The conductivity, dielectric constant and tan δ values increased from 1.34 × 10?14 to 2.89 × 10?2 S/cm, from 2.113 to 19.845, from 0.094 to 4.789. Tensile strength increased with an increase in PAni content up to 7% and drastically decreased above 15%, while the percentage elongation at break decreased with an increase in PAni content. TGA studies revealed that the thermal stability of PAni improved after blending with EVA. EVA‐PAni blends were found stable up to 110°C. X‐ray diffractograms of EVA‐PAni blend showed an intense peak at 26° (2θ), reflecting the influence of EVA crystallinity. Scanning electron micrographs confirmed the two‐phase morphology of the system.  相似文献   

18.
Alkyne functional phenolic resin was cured by azide functional epoxy resins making use of alkyne‐azide click reaction. For this, propargylated novolac (PN) was reacted with bisphenol A bisazide (BABA) and azido hydroxy propyloxy novolac (AHPN) leading to triazole‐linked phenolic‐epoxy networks. The click cure reaction was initiated at 40–65°C in presence of Cu2I2. Glass transition temperature (Tg) of the cured networks varied from 70°C to 75°C in the case of BABA‐PN and 75°C to 80°C in the case of AHPN‐PN. DSC and rheological studies revealed a single stage curing pattern for both the systems. The cured BABA‐PN and AHPN‐PN blends showed mass loss above 300°C because of decomposition of the triazole rings and the novolac backbone. Silica fiber‐reinforced syntactic foam composites derived from these resins possessed comparable mechanical properties and superior impact resistance vis‐a‐vis their phenolic resin analogues. The mechanical properties could be tuned by regulating the reactant stoichiometry. These low temperature addition curable resins are suited for light weight polymer composite for related applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41254.  相似文献   

19.
Novolak‐type phenol‐formaldehyde (PF) resins with solution form were prepared by reacting phenol‐liquefied Cryptomeria japonica (Japanese cedar) wood with formalin in the presence of methanol. Wood powders of Albizzia falcate (Malacca albizzia) impregnated with these resins were air dried followed by an oven‐dried at 60°C. DSC analysis showed the PF resin existing in wood powders could be melted, and could be cured if hexamine was mixed and heated at high temperature. Compression‐molded plates made with PF resin impregnated woods had a high degree of curing reaction. However, compression‐molded plates hot‐pressed at 180°C for 8 min or 200°C for 5 min had better internal bonding strength and dimensional stability than others. Premixing hexamine with PF resin and impregnating into wood powders simultaneously could enhance the reactivity of PF resin, but it was not useful for improving the properties of compression‐molded plates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

20.
The objective of this research was to investigate thermal stability and dynamic mechanical behavior of Exfoliated graphite nanoplatelets (xGnP™)‐Linear Low‐Density Poly Ethylene (LLDPE) nanocomposites with different xGnP loading content. The xGnP‐LLDPE nanocomposites were fabricated by solution and melt mixing in various screw rotating systems such as co‐, counter‐, and modified‐corotating. The storage modulus (E′) of the composites at the starting point of −50°C increased as xGnP contents increased. E′ of the nanocomposite with only 7 wt% of xGnP was 2.5 times higher than that of the control LLDPE. Thermal expansion and the coefficient of thermal expansion of xGnP‐loaded composites were much lower than those of the control LLDPE in the range of 45–80°C (299.8 × 10−6/°C) and 85–100°C (365.3 × 10−6/°C). Thermal stability of the composites was also affected by xGnP dispersion in LLDPE matrix. The xGnP‐LLDPE nanocomposites by counter‐rotating screw system showed higher thermal stability than ones by co‐rotating and modified‐co‐rotating system at 5 wt% and 12 wt% of xGnP. xGnP had a great effect on high thermal stability of xGnP‐LLDPE composites to be applied as tube and film for electrical materials. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers  相似文献   

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