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1.
In this study, we focused on the fabrication of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/sericin composites via a simple solution‐blending method. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, UV spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and measurements of the conductivity, tensile strength, and antibacterial activity against Staphylococcus aureus. The results of FTIR and UV spectroscopy implied the occurrence of hydrogen bonding between sericin and the PVA/PVP blend. The structure and morphology, studied by XRD and SEM, revealed that the sericin particles were well dispersed and arranged in an orderly fashion in the blend. The glass‐transition temperature (Tg) of the composite was higher than that of the pure blend, and the Tg value shifted toward higher temperatures when the volume fraction of sericin increased. TGA indicated that sericin retarded the thermal degradation; this depended on the filler concentration. The mechanical and electrical properties, such as the tensile strength, alternating‐current electrical conductivity, dielectric constant, and dielectric loss of the composites, were higher than those of the pure blend, and these properties were enhanced when the concentration of sericin was increased up to 10 wt % filler content, whereas the elongation at break of the composite decreased with the addition of sericin particles. The antibacterial properties of the composite showed that sericin had a significant inhibitory effect against S. aureus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43535.  相似文献   

2.
A hydrophobically modified polyacrylamide (PAM) was synthesized by the copolymerization of acrylamide (Am) and N‐hexadecylacrylamide (hAm) through solution copolymerization in a polar organic solvent. Polymer synthesis was performed in three nonaqueous media, including dimethyl sulfoxide (DMSO), a mixture of DMSO and an anionic surfactant such as sodium dodecyl sulfate, and a mixture of DMSO and an acidic surfactant such as dodecyl benzene sulfonic acid. The obtained copolymer, poly(acrylamide‐co‐N‐hexadecylacrylamide) [poly(Am‐co‐hAm)], was characterized by 1H‐NMR. The physical properties of poly(Am‐co‐hAm)s synthesized in different media were compared with those of PAM and with each other by viscosity measurement, X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. We investigated the ways in which the polymerization medium affected the hydrophobic distribution within the resulting copolymer structure. This aspect, in turn, should have altered the solution properties and the microstructure of the copolymer. For this purpose, we studied the viscometric behavior in diluted solutions, the thermal behavior and thermal stability of the copolymers, and finally, the crystalline structure of the copolymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39939.  相似文献   

3.
Small particle diameter thermally expandable microspheres (TEMs) were obtained for potential utilization in wood, with special attention on their particle diameters and expansion properties. The revolving speed of homogenization (RS) of 800 ~ 3000 r min−1 was applied in suspension polymerization under atmospheric pressure to prepare TEMs, with n-hexane as core material and the copolymer of acrylonitrile, methyl acrylate, and vinyl acetate as shell. (a) The effect of the RS on the particle diameters of TEMs presented a negative correlation at low RS and remained stable at high RS, (b) When the RS was 1900 ~ 2100 r min−1, the optimized TEMs with average particle diameters of 3.82 ~ 4.06 μm were prepared, possessing expansion ratios of 3.4 ~ 4.3 and an expansion temperature of 112°C, (c)The optimized TEMs had core-shell structure and high encapsulated content of alkane, and (d) The TEMs with small particle diameters could be impregnated into wood and expand successfully in wood cell lumens.  相似文献   

4.
Di‐hexadecanol maleic/Triallyl isocyanurate cross‐linked copolymers as a novel solid–solid phase change materials were successfully synthesized through bulk polymerization. TAIC is the skeleton and DM is a functional side chain that stores and releases heat during its phase transition process. Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, polarizing optical microscopy, differential scanning calorimetry, and thermogravimetry were employed to study the composition, chemical structure, crystalline properties, phase transition behaviors, and the thermal stability of the cross‐linked copolymers, respectively. The test results indicate that DM/TAIC cross‐linked copolymers have good thermal reliability and heat storage durability after 500 thermal cycles. The phase change temperatures of DM/TAIC cross‐linked copolymers were approximately 28.24–37.02°C, and it has high latent heat storage capacity of more than 83 J/g. At the same time, DM/TAIC cross‐linked copolymers have good thermal stability, and they can be processed or used in high temperature environments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44065.  相似文献   

5.
Eco-friendly poly(vinyl alcohol) (PVA), PVA/boric acid, PVA/halloysite nanotubes (HNTs), and PVA/amino-functionalized HNTs (APTES-HNTs) films were fabricated by a solution casting technique. The samples were characterized by fourier transform infrared, X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and energy-dispersive spectroscopy. The characterization results proved the chemical and physical interactions between the PVA and different additives. The viscoelastic behavior of the films was evaluated by DMA and creep analysis. The storage modulus, loss factor, and both αα and ββ transitions affected by APTES-HNTs as a potential filler to form effective cross-links. APTES-HNTs existence enhanced creep-recovery beyond expectations. Tensile and impact strength were measured to understand samples' mechanical stability. PVA/APTES-HNTs and PVA/boric acid showed more yield behavior after the elastic limit. Furthermore, the subsequent rupture and impact strength were increased significantly compared with neat PVA and PVA/HNTs. The viscoelastic and mechanical behaviors were linked to each other by the area under Tanδ curve and the work of rupture and impact strength, which their linear correlation coefficient is statistically significant at 95% confidence limits. It seems that the presence of APTES-HNTs provides new cross-links, which altered (improved) the physico-mechanical properties of PVA, offering a bionanocomposite suitable for further applications. From the literature, possible explanations are provided for these observations.  相似文献   

6.
In this study, an amide functionalized bis-benzoxazine (AI-al) has been synthesized using allylamine, ortho-amide functional bis-phenol and paraformaldehyde as raw materials via Mannich condensation. This newly obtained benzoxazine has been used to react with polydimethylsiloxane (PDMS) through hydrosilylation to form poly(benzoxazine-co-amide-co-siloxane) (AI-al-PDMS) featuring siloxane, amide and benzoxazine as repeating units. The chemical structures of both oxazine ring-containing monomer and copolymer are confirmed by NMR and FT-IR spectroscopies. Besides, the thermally activated polymerization behaviors of AI-al and AI-al-PDMS are investigated by DSC, and the subsequent conversion of benzoxazole formation is studied by in situ FT-IR. Moreover, dynamic mechanical analysis and thermogravimetric analysis are used to determine the thermal properties of the cross-linked polymers. The resulting cross-linked poly(benzoxazole-co-siloxane) derived from AI-al-PDMS shows excellent thermal stability (no Tg can be observed before 400°C; Td5 of 393°C) and low dielectric constants (2.52–2.13 in the frequency range of 1 Hz to 1 MHz), evidencing its great potential applications in electronic packing, aerospace, and other high-performance fields.  相似文献   

7.
The thermal properties of n‐hexadecane (HD) encapsulated in crosslinked capsule particles containing a water and/or air domain were studied from the viewpoint of heat‐storage applications. The capsule particles were prepared by the microsuspension polymerization of divinylbenzene at 70°C with the self‐assembling of phase‐separated polymer method that we developed. In the differential scanning calorimetric thermograms, pure HD had a single solidification temperature (Ts) peak at 15°C, whereas the encapsulated HD containing a water domain had two peaks at 6 and 1°C. That is, the encapsulated HD containing the water domain required a longer time and lower temperature to complete the solidification than pure HD, which was negative for heat‐storage applications. However, once the particles were dried and the water domain was replaced with air, the problem with the partially lowered Ts improved. The air domain was also found in the encapsulated HD core after solidification because of the shrinkage of HD. The presence of the air domain did not affect the thermal stability of the encapsulated HD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

8.
Microcapsules loaded with sodium phosphate dodecahydrate (DSP) were prepared according to the solvent evaporation method. The microencapsulated phase‐change materials (MEPCMs) possessed methyl methacrylate crosslinked with ethyl acrylate generated poly(methyl methacrylate) (PMMA) as the coating polymer. The influences of the polymerization time, polymerization temperature, and organic solvent types on the performances of the MEPCMs were studied in this report. The results indicate that the polymerization time and temperature had barely any effect on the size but a significant effect on the surface morphology of the microphase‐change materials. The solubility of the shell material varied in different organic solvents, and this to different phase‐transition enthalpies. In addition, DSP could be encapsulated well by PMMA, and the as‐prepared MEPCMs were equipped with a good morphology and a small particle size. When toluene and acetone were used as organic solvents, the MEPCMs had an interesting energy storage capacity of 142.9 J/g at 51.51°C, and this made them suitable for different applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1516–1523, 2013  相似文献   

9.
The high polymerization temperature of acrylic bone cements used in hip replacement implantation may cause thermal necrosis of surrounding tissues. In order to reduce the polymerization temperature, acrylic bone cement has been modified with a biocompatible polymeric phase‐change material (PCM) based on poly(ethylene glycol) (PEG) of different molecular weights and stabilized with potato starch. Structural and morphological studies were performed, and the thermal and mechanical properties were investigated. The incorporation of PEG‐based PCM led to a decrease in the polymerization temperature of bone cement from 70 °C for unmodified cement to 58 °C for modified cement. Modified cement materials were stable in incubation tests, although acoustic analysis data revealed a decrease in propagation speed after incubation, which indicates formation of material defects (pores, cracks, voids, etc.) due to water activity. However, in the regeneration process, these defects can be filled by freshly grown bone tissue leading to better incorporation of bone cement replacements into tissue. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43898.  相似文献   

10.
In this article, boric acid‐modified poly(aryl ether sulfone) (PES‐B) membranes were prepared by solution blending, solution casting, evaporation, and programmed temperature curing method for the first time. The chemical modification of poly(aryl ether sulfone) was accomplished by the curing of poly(aryl ether sulfone) with pendent phenyl hydroxide (PES‐OH) under the function of boric acid. The reaction mechanisms and the effects of boric acid content were thoroughly investigated. Processing conditions and structures of PES‐B were determined by FT‐IR spectra. It has been found that the B(OH)3/PES composite membranes were completely cured after treatment at 300°C for 4 h. When boric acid content was over 4.7%, PES‐B membranes presented phase separation and full cross‐linking structures. DSC measurements demonstrated that the addition of boric acid had influenced the glass transition temperature of PES‐B, which provided the proof of the appearance of cross‐linking network structure. TGA results confirmed that the thermal stability of the prepared PES‐B composites was improved. Furthermore, the cross‐linked composite membranes exhibited excellent mechanical property and solvent resistance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40860.  相似文献   

11.
The focus of this study was mainly on the use of scrap poly(ethylene terephthalate) (PET) in poly(butylene terephthalate)‐rich blend systems. A good combination of tensile and impact properties was observed in the newly formed blend system with scrap PET. The morphology depicted controlled and well‐dispersed phases. The thorough mixing of the constituents was observed in the thermal study. For this innovative blend system, an attempt to correlate the mechanical, thermal, structural, morphological properties and the chemistry of the blend system seemed to be technoeconomical. This study contributed to the recycling of waste material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

12.
Poly(l ‐lactide) (PLLA) is a bioabsorbable polymer with high stiffness and strength compared to the other commercially available bioabsorbable polymers. The properties of PLLA can be improved by straining, causing deformation‐mediated molecular orientation. PLLA tubes were biaxially strained above their Tg for improvement of their strength, in a two‐step process (sequential straining). Mechanical properties and crystal morphology were investigated as a function of processing strain rate and temperature. DSC revealed that a low processing strain rate allows molecular chain relaxation in the direction of strain and the crystallization is suppressed. Faster strain rates on the other hand suppress chain relaxation, and results in crystalline tubes. The mechanical properties are influenced by both processing strain rate and temperature. Low strain rates allow chain relaxation resulting in the lowest strength and stiffness, whereas a larger stiffness and strength is achieved by increasing strain rate and temperature. Isotropic mechanical properties are only observed at high processing strain rates. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45192.  相似文献   

13.
Radiation‐induced graft copolymerization of alpha methyl styrene (AMS)‐butyl acrylate (BA) mixture onto poly(etheretherketone) (PEEK) was carried out to develop films of varying copolymer compositions. The characterization of films was carried out with fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The presence of AMS and BA units within the film matrix was confirmed by FTIR. The intensity of the characteristic peaks for AMS and BA increased with the increasing grafted component in the films. The crystallinity of the films as observed from DSC and XRD decreased with the increasing graft levels. On the other hand, the melting temperature of the base polymer was almost unaffected by irradiation and the grafting process. The glass transition temperature (Tg) of the grafted film increased as compared to the virgin PEEK. Ungrafted film showed a stable thermogram up to ~500°C. However, the grafting introduced a new decomposition range in the copolymer, due to the presence of the AMS/BA. AFM images showed the formation of domains on the grafted PEEK film surface. The SEM also showed domain formation of the grafted component within the PEEK matrix. However, the fracture analysis did not show any prominent phase separation. Mechanical characterization of films in terms of tensile strength, elongation, and modulus was also carried out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

14.
A series of new segmented semifluorinated polyaryl ethers (PAEs) containing a biphenyl segmented by semifluorinated oligoethylene (SFE) units were prepared by nucleophilic addition of a commercial oligo(ethylene glycol)s to 4,4′‐bis(4‐trifluorovinyloxy)biphenyl. These new thermoplastics were characterized by 1H and F19 nuclear magnetic resonance (NMR) and attenuated total reflectance Fourier transform infrared (ATR‐FTIR). Gel permeation chromatography (GPC) analysis displayed number average molecular weights (Mns) from 9000 to 13,000. Thermal properties of the polymers were studied by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC chromatograms displayed glass transition temperatures (Tgs) from 11 to 1°C. The onsets of degradations were observed by TGA analysis between 313 to 333°C in air and 326 to 363°C in nitrogen, respectively. A second onset of degradation was observed from 452 to 470°C for all polymers. In addition, crystalline morphologies were studied by tapping mode atomic force microscopy (TM‐AFM) and showed needle‐like crystallites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41798.  相似文献   

15.
Microcapsules containing paraffin and diethyl ethylphosphonate (DEEP) flame retardant with uncrosslinked and crosslinked poly (methacrylic acid‐co‐ethyl methacrylate) (P(MAA‐co‐EMA)) shell were fabricated by suspension‐like polymerization. The surface morphologies of the microencapsulated phase change materials (microPCMs) were studied by scanning electron microscopy. The thermal properties and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The flame retarding performances of the microcapsule‐treated foams were calculated by using an oxygen index instrument. The DSC results showed that the crosslinking of the polymer shell led to an increase in the melting enthalpies of the microcapsule by more than 15%. The crosslinked P(MAA‐co‐EMA) microcapsules with DEEP and without DEEP have melting enthalpies of 67.2 and 102.9 J/g, respectively. The TGA results indicated that the thermal resistant temperature of the crosslinked microcapsules with DEEP was up to 171°C, which was higher than that of its uncrosslinked counterpart by ~20°C. The incorporation of DEEP into the microPCM increased the limiting oxygen index value of the microcapsule‐treated foams by over 5%. Thermal images showed that both microcapsule‐treated foams with and without DEEP possessed favorably temperature‐regulated properties. As a result, the microPCMs with paraffin and DEEP as core and P(MAA‐co‐EMA) as shell have good thermal energy storage and thermal regulation potentials, such as thermal‐regulated foams heat insulation materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41880.  相似文献   

16.
The series of poly(trimethylene terephthalate)-block-PCLT (PTT-block-PCLT) copolymers with different contents of PTT as rigid, and poly(caprolactone) (PCL) as flexible segments have been synthesized from dimethyl terephthalate (DMT), 1,3-bio-propanediol, and PCL diol) in a two-step process involving transesterification and polycondensation in the melt. The weight amount of flexible PCLT segments varied from 0 (homopolymer PTT), 25, 35 to 45%. The molecular structure of the synthesized copolymers was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses. According to Hoy's method, one confirmed that PTT and PCL are likely miscible, as the difference of the solubility parameters of PTT and PCL block pairs, equals to 3.15 MPa1/2. Moreover, the phase structure and mutual miscibility for the series of PTT-block-PCLT copolymers was characterized by differential scanning calorimetry, dynamic mechanical thermal analysis, and wide-angle X-ray scattering measurements. In copolymers with 35 and 45 wt % of flexible segments, the crystalline phase is formed during annealing above glass-transition temperature of copolymer. These copolymers during cooling at the standard rate do not crystallize. It was also found that incorporation of PCLT flexible segments, due to the macrophase separated structure, cause the decrease of the melting point and glass-transition temperature, along with the tensile modulus and tensile strength of PTT-block-PCLT copolymers, and at the same time cause an increase in the value of the elongation at break. As a result of copolymerization of PTT with PCLT, one obtained multiblock copolymers with a heterophase structure. By changing the PTT/PCLT ratio, one obtained copolymers that differ in hardness and tensile strength. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47341.  相似文献   

17.
The influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l ‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l ‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41105.  相似文献   

18.
In this work, Phthalonitrile containing benzoxazine (BA-ph) and Bisphenol A based cyanate ester (CE) were chosen as the matrix resin. Various amount of nano-SiO2 was incorporated into BA-ph/CE and their glass fiber-reinforced composite laminates were fabricated. Curing reaction and processability of BA-ph/CE/SiO2 blends were studied by differential scanning calorimetry and dynamic rheological analysis. Results showed that BA-ph and CE exhibited good processability and curing reaction of BA-ph/CE was not obviously affected by SiO2. Scanning electron microscope images of the composites showed that SiO2 particles were well dispersed in BA-ph/CE matrix. Moreover, SiO2 could act as physical crosslinking points and diluent in matrix as well as between the glass fibers to improve the mechanical properties of composite laminates. As the results of dynamic mechanical analysis and thermogravimetry analysis, composite laminates possessed satisfactory Tg and good thermal stability. With incorporation SiO2 particles into matrix resin, dielectric constant and dielectric loss of BA-ph/CE/SiO2/GF composites were increased and showed frequency dependence.  相似文献   

19.
The environmental sustainability, mechanical durability, and thermal stability of the poly(ethylene terephthalate) (PET)-based nanocomposite films compared with pure PET were evaluated. The samples were obtained by incorporating 2 wt% of TiO2, SiO2, ZnO nanoparticles (NPs), and an equal mixture of NPs in polymer by melt-mixing in a twin-screw extruder. The mechanical properties and hardness of samples were determined by the tensile and the atomic force microscopy-based nanoindentation tests. The melting, crystallization, and glass transition temperatures of samples were studied by dynamic mechanical thermal analysis and differential scanning calorimetry. The effects of compatibility, dispersity, and hydrophobicity of NPs on the surface morphology, crystallinity, and thermomechanical properties of nanocomposites were studied. The interaction of SiO2 NPs with PET chains had a promising effect on the surface morphology, high elastic modulus, dispersibility, crystallinity, and thermostability of the sample. The mixing of ZnO and TiO2 NPs improved the UV-blocking effects, and photostability, while the SiO2 and TiO2 NPs maintained the thermal properties of the film against UV radiation. The resulting film could be a good candidate as a greenhouse covering material due to its suitable photosynthetically active radiation transmittance.  相似文献   

20.
Polylactide (PLA) is an attractive candidate for replacing petrochemical polymers because it is biodegradable. In this study, a specific PLA 2002D was melt‐mixed with a new plasticizer: glycerol monostearate (GMS). The PLA/GMS blends with different ratios were analyzed by dynamic mechanical analysis and differential scanning calorimetry. Although a slightly phase separation can be seen in DSC curves, the SEM micrographs of the impact fracture surfaces of PLA/GMS blends had a relatively good separation and this phenomenon was in good agreement with their higher impact strength. The result showed that the adding of GMS has enhanced the flexibility of PLA/GMS blends as compared to neat PLA. The relationship between complex viscosity and angular frequency of the PLA/GMS blends exhibits that the melt viscosity substantially lower than that of neat PLA. For example, at 10 rad/s, the melt viscosity of PLA/GMS (85/15) was reduced by about 7.2% compared to that of neat PLA. The impact strength was changed from 4.7 KJ/m2 for neat PLA to 48.2 KJ/m2 for 70/30 PLA/GMS blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

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