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1.
Surface topographical modifications of a soft magnetoactive elastomer (MAE) in response to variable applied magnetic field are investigated. The analysis is performed in situ and is based on optical microscopy, spread optical reflection and optical profilometry measurements. Optical profilometry analysis shows that the responsivity of magnetic field‐induced surface roughness with respect to external magnetic field is in the range of 1 µm/T. A significant hysteresis of surface modifications takes place for increasing and decreasing fields. Investigations of shape of sessile water droplets deposited on the MAE surface reveal that field‐induced topographical modifications affect the contact angle of water at the surface. This effect is reversible and the responsivity to magnetic field is in the range of 20°/T. Despite the increased surface roughness, the apparent contact angle decreases with increasing field, which is attributed to the field‐induced protrusion of hydrophilic microparticles from the surface layer. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46221.  相似文献   

2.
Poly(N‐isopropylacrylamide) (PNIPAAm) has been a well‐known stimuli–responsive material and has been used in multiple novel applications. One of the key attributes to make the hydrogel more attractive is to control the response time and temperature. This work focused on comparing the physical properties, such as response time, transition temperature, heat of fusion, and mechanical strength, of macroporous and microporous PNIPAAm hydrogels, respectively. It was found that the macroporous hydrogels synthesized from a low‐temperature polymerization with addition of tetramethyl orthosilicate exhibited a faster response time and superior mechanical strength. Furthermore, to modulate the transition temperature, both the macroporous and microporous hydrogels were subjected to different qualities of media by introducing a cosolvent (methanol) or an anionic surfactant (sodium dodecyl sulfate). Interestingly, addition of a cosolvent demonstrated a more pronounced effect on the macroporous hydrogel, whereas the surfactant resulted in a more pronounced effect on the microporous hydrogel. Such results revealed that based on their porosity; there were appreciable differences when the PNIPAAm hydrogels interacted with media molecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42776.  相似文献   

3.
The present study focuses on the mechanical properties of hydrophilically or hydrophobically modified poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels, and all discussions on their improved mechanical strengths are based on the conformational effects of hydrophobic side chains attached to the comonomers and the structural differences between the crosslinkers. Three different types of monoalkyl itaconates, bearing octyl (Oc), cetyl (Ce), and cyclohexyl (CH) groups as comonomers, were used to prepare the copolymeric PNIPAAm hydrogels crosslinked with N,N′‐methylenebisacrylamide (BIS) and tetraallylammonium bromide (TAB) as neutral tetrafunctional and ionic octafunctional crosslinkers, respectively. The most striking result is the compressive E modulus of TAB‐crosslinked PNIPAAm hydrogel containing 10 mol % of mOcI. It reaches nearly 1.0 MPa and is independent of the temperature and pH of the swelling/shrinking medium. The result was discussed in terms of the inter/intramolecular interactions between hydrophobic octyl groups adopting a rod‐like conformation in the case of 25 °C/distilled deionized water (DDW) and 37 °C/DDW combinations. Further, it was observed that the electrostatic repulsive forces between the carboxylate groups on mOcI units could be suppressed even at 37 °C and pH 9 due to the rod‐like conformations of C8H17 groups. Its micrographs under bright‐field and polarized light supported the presence of an ordered anisotropic phase and multiple associations of extended, hydrophobic side chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45039.  相似文献   

4.
A series of thermal insulation, acoustic absorption isocyanate‐based lightweight polyimide (PI) foams with 4,4′‐diaminodiphenyl ether (ODA) units were prepared from polyaryl polymethylene isocyanate (PAPI) and the esterification solution derived from pyromellitic dianhydride (PMDA) and ODA. The structures and properties of the PI foams prepared with different molar ratio of ODA/PMDA were investigated in detail. The results show that the ODA units have great influence on the foam properties. With the increase of the ODA units, the density decreases firstly and then increases. When the molar ratio of ODA/PMDA is 3/10, the foam reaches the minimum density (13.7 kg/m3). Moreover, with increasing the ODA units, the acoustic absorption properties increase firstly and then decrease owing to the variation of the average cell diameter of the PI foams. All PI foams show excellent thermal stability, and the 5% and 10% weight loss temperature are in the range of 250–270 °C and 295–310 °C, respectively. In addition, the PI foams present low thermal conductivity and thermal diffusivity. Furthermore, the mechanical property was also evaluated and the compressive strength of the PI foams is in the range of 33.0–45.7 kPa. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46029.  相似文献   

5.
The study of gel‐network structure is not as extensive as the study of the application of hydrogels. However, the distribution of the inner structure is crucial for designing hydrogels with tunable mechanical properties to meet certain kinds of demands. In this study, a series of hydrophobic association hydrogels (HA‐gels) were synthesized by free‐radical micellar copolymerization in a sodium dodecyl sulfate (SDS) surfactant solution. The hydrophobic monomer was palmityl alcohol poly(oxyethylene acrylate) (AEO–AC), which is an ecofriendly alternative to the traditional octyl phenol poly(oxyethylene acrylate). Interestingly, we found that the molar ratio [or ratio point (R)] of SDS to AEO–AC played a key role in tuning the mechanical properties. All series HA‐gels denominated a similar down–up–down tendency with increasing R, and the best R is 3. This result was consistent with the microscopic network structure number of the hydrophobic monomer (NH = 21–24), and this indicated that each hydrophobic monomer associated three SDS monomers in its internal networks. The resulting AEO–AC–acrylamide gels exhibited the best mechanical strength (yield maximum broken stress = 218 kPa) and the maximum effective crosslink density. Moreover, the relationship between the network structure and the mechanical properties of the HA‐gels was investigated with various Rs. Two different interaction effects of distribution between SDS and AEO–AC are discussed in detail. The HA‐gels exhibited self‐healing properties and maintained their shape in water over 160 days. The results indicate that changing R is an effective method for tuning the mechanical properties of HA‐gels as a type of prospective biomedical material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45196.  相似文献   

6.
The gloss properties of the polycarbonate (PC)/poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) (MABS) blend with styrene‐acrylonitrile‐co‐glycidyl methacrylate (SAN‐co‐GMA) as a compatibilizing agent were investigated. For the PC/poly(MABS)/SAN‐co‐GMA (65/15/20, wt %) blend surface, the reduction of gloss level was observed most significantly when the GMA content was 0.1 wt %, compared with the blends with 0.05 wt % GMA or without GMA content. The gloss level of the PC/poly(MABS)/SAN‐co‐GMA (0.1 wt % GMA) blend surface was observed to be 35, which showed 65% lower than the PC/poly(MABS)/SAN‐co‐GMA blend without GMA content. The gloss reduction was most probably caused by the insoluble fractions of the PC/poly(MABS)/SAN‐co‐GMA blend that were formed by the reaction between the carboxylic acid group in poly(MABS) and epoxy group in SAN‐co‐GMA. The results of optical and transmission electron microscope analysis, spectroscopy study, and rheological properties supported the formation of insoluble structure of the PC/poly(MABS)/SAN‐co‐GMA blend when the GMA content was 0.1 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46450.  相似文献   

7.
A thermosetting styrene‐based shape memory polymer (SMP) filled with nanoscale (30 nm) carbon black are prepared to reinforce the thermomechanical performances and realize the high‐efficient electronic actuation at macro scale due to the carbon–carbon network morphology at nano/micro scale. The elastic modulus of this thermosetting SMP composite is significant strengthened and can maintain at 1–2.5 GPa at around the room temperature, which is suitable for used as a structural material. The electronic resistivity decreases sharply at a quite low percolation threshold range (2–5%), and maintains at a relatively low and stable level of electronic resistivity. Furthermore, the electronic resistivity also exhibits relative stability in terms of the resistivity–temperature–time relationship and the evolution of resistivity upon heating–cooling cycles. This shape memory styrene‐based composite is suitable to be used as an electroactive functional material in realistic engineering. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45978.  相似文献   

8.
Three difunctional benzoxazines were synthesized from cresol isomers (o‐, m‐, and p‐methylphenols), 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane, and formaldehyde. The ring‐opening polymerization temperature decreases in the order of ortho‐, para‐, and meta‐positions of methyl group for the benzoxazine monomers, whereas the glass transition temperature increases in the order of ortho‐, para‐, and meta‐positions of methyl group for the resultant polybenzoxazines. In addition, the polybenzoxazines exhibit one‐way dual‐shape‐memory behavior in response to changes in temperature, and the shape‐memory effects are evaluated by tensile and bending tests with a temperature program based on glass transition temperature. The o‐ and p‐cresol‐based polybenzoxazines exhibit higher shape‐memory performance than their m‐cresol‐based analogue/counterpart. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45443.  相似文献   

9.
To overcome serious rigidity depression of rubber‐toughened plastics and fabricate a rigidity‐toughness balanced thermoplastic, a combination of styrene‐[ethylene‐(ethylene‐propylene)]‐styrene block copolymer (SEEPS) and ethylene‐propylene rubber (EPR) was used to toughen polypropylene. The dynamic mechanical properties, crystallization and melting behavior, and mechanical properties of polypropylene (PP)/EPR/SEEPS blends were studied in detail. The results show that the combination of SEEPS and EPR can achieve the tremendous improvement of low‐temperature toughness without significant strength and rigidity loss. Dynamic mechanical properties and phase morphology results demonstrate that there is a good interfacial strength and increased loss of compound rubber phase comprised of EPR component and EP domain of SEEPS. Compared with PP/EPR binary blends, although neither glass transition temperature (Tg) of the rubber phase nor Tg of PP matrix in PP/EPR/SEEPS blends decreases, the brittle‐tough transition temperature (Tbd) of PP/EPR/SEEPS blends decreases, indicating that the increased interfacial interaction between PP matrix and compound rubber phase is also an effective approach to decrease Tbd of the blends so as to improve low‐temperature toughness. The balance between rigidity and toughness of PP/EPR/SEEPS blends is ascribed to the synergistic effect of EPR and SEEPS on toughening PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45714.  相似文献   

10.
Parts produced by extrusion‐based additive manufacturing experience the disadvantage of consisting of many weld‐lines, which consequently downgrade their mechanical properties. This work aims at maximizing the strength of printed parts by considering and improving the intra‐ and inter‐layer cohesion between adjacent strands. Therefore, printed poly(lactic acid) specimens were characterized by means of a particular tensile test setup, and the inter‐layer cohesion of printed specimens was evaluated by means of the double cantilever beam test. A detailed parametric statistical evaluation, which included printing temperatures, layer thicknesses, and layer‐designs, was complemented by the material's viscosity data and the analysis of the specimens' fracture surfaces and cross‐sections. An optimal layer‐design was found to be a key parameter in the optimization of strength with regard to different loading directions. Additionally, the maximization of the cohesion leads to a tremendous improvement in the mechanical performance of the printed parts, resulting in strengths of roughly 90% of those of compression‐molded parts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45401.  相似文献   

11.
High‐vinyl polybutadiene rubber (HVBR) and solution‐polymerized styrene–butadiene rubber (SSBR) can meet the requirements of high‐performance tires due to their excellent wet skid resistance and lower rolling resistance. In this paper, the effects of the vinyl and phenyl groups and their contents on the vulcanization behavior, mechanical strength, fatigue resistance, heat resistance, and wear resistance of HVBR and SSBR were investigated, and the dynamic viscoelasticities of HVBR and SSBR vulcanizates with or without carbon black were explored by dynamic mechanical analysis (DMA). The experimental results showed that the vinyl groups contributed more to the wear resistance and fatigue resistance of vulcanizates than the phenyl groups, but the phenyl groups contributed more to the mechanical strength of the vulcanizates than the vinyl groups. The DMA results showed that the vinyl and phenyl groups could significantly improve the road‐gripping capability and wet skid resistance of HVBR and SSBR vulcanizates, but carbon black could slightly weaken the effect of vinyl and phenyl groups on the wet skid resistance of vulcanizates, and the effect of carbon black on vinyl groups was more significant. Despite the presence of carbon black, the phenyl groups contributed more heat buildup to the vulcanizates than the vinyl groups. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45975.  相似文献   

12.
Recycled polyol and benzimidazole were both grafted onto polyurethane (PU) to enhance the surface hydrophilicity and antifungal activity, respectively. The two grafted groups affected the viscosity, crosslink density, soft segment glass transition, breaking stress, flexibility at freezing temperature, shape recovery at ?10 °C, surface hydrophilicity, and antifungal activity. The glass transition temperature increased from ?67.5 °C for plain PU up to ?60.8 °C after the grafting of polyol. The breaking stress and shape recovery of the grafted PU increased up to 425% and 200%, respectively, relative to plain PU because of the chemical linking by the grafted polyol. The hydrophilicity of PU, evaluated by the water contact angle and water swelling ratio, increased with increasing polyol content. A PU sample demonstrated excellent low‐temperature flexibility in comparison to plain PU and control sample. Finally, the PUs modified with grafted polyol and benzimidazole completely suppressed fungal growth. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46600.  相似文献   

13.
Bromo‐substituted polyaniline (Br‐PANI) is prepared by a novel strategy in which PANI is used as raw material, potassium bromate and potassium bromide as brominate regents. The obtained Br‐PANI is characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, elemental analysis, FTIR, UV–vis spectra, and TGA. The results clearly indicate that Br has successfully attached to the benzene ring of PANI by chemical bond. The behavior of Br‐PANI toward bacteria is characterized by plate counting, minimal inhibitory concentration, and minimal bactericidal concentration methods. The experimental results indicate that both doped and dedoped Br‐PANIs have long‐term antibacterial activities as compared to doped/dedoped PANI. What's more, the antibacterial abilities increase with increasing the Br/N molar ratio of the Br‐PANI. Thus Br‐PANI should be a kind of efficient and environmentally friendly antibacterial agent. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45657.  相似文献   

14.
Animal models suggest that the chemokine ligand 2/CC‐chemokine receptor 2 (CCL2/CCR2) axis plays an important role in the development of inflammatory diseases. However, CCR2 antagonists have failed in clinical trials because of a lack of efficacy. We previously described a new approach for the design of CCR2 antagonists by the use of structure–kinetics relationships (SKRs). Herein we report new findings on the structure–affinity relationships (SARs) and SKRs of the reference compound MK‐0483, its diastereomers, and its structural analogues as CCR2 antagonists. The SARs of the 4‐arylpiperidine group suggest that lipophilic hydrogen‐bond‐accepting substituents at the 3‐position are favorable. However, the SKRs suggest that a lipophilic group with a certain size is desired [e.g., 3‐Br: Ki=2.8 nM , residence time (tres)=243 min; 3‐iPr: Ki=3.6 nM , tres=266 min]. Alternatively, additional substituents and further optimization of the molecule, while keeping a carboxylic acid at the 3‐position, can also prolong tres; this was most prominently observed in MK‐0483 (Ki=1.2 nM , tres=724 min) and a close analogue (Ki=7.8 nM ) with a short residence time.  相似文献   

15.
Random copolymer hydrogels of N‐isopropylacrylamide and N‐ethylacrylamide (NEAM) were prepared using different monomer compositions in 1:1 methanol–water mixtures. The samples were characterized by cononsolvency study in methanol‐water mixtures at various temperatures, swelling properties measurements, scanning electron microscopy. With changing ratio of the monomers in the reaction mixture, the thermal, morphological and swelling properties, varied significantly. The change in the properties with monomer composition variation are interpreted based on the different thermoresponsive characteristics and interactions of gels of N‐isopropylacrylamide and NEAM (homo‐ and copolymer gels) in water and different methanol‐water mixtures, their variable compositions in the synthesis mixtures, and their morphologies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45176.  相似文献   

16.
Triazole crosslinked polymers were prepared by reacting glycidyl azide polymer (GAP) with the propargyl ‐ terminated poly(tetramethylene oxide) (PTMP) at different molar ratios of azide versus alkyne. Based on the optimum mechanical properties of the GAP/PTMP ‐ 2.5, a series of GAP/PTMP nanocomposites reinforced by either multi ‐ walled carbon nanotubes (MWCNTs) or carboxy ‐ functionalized multiwalled carbon nanotubes (MWCNTs ‐ COOH) were prepared with different mass ratios. The glass transition temperatures (Tg, PTMP) assigned to PTMP of the GAP/PTMP composites almost kept at a constant range when the molar ratio of azide versus alkyne was from 1.0 to 2.5. When the loading MWCNTs was 1.0 wt %, the tensile strength and elongation at break achieved a maximum of 1.77 MPa and 36.3%, respectively. The nanocomposites with nearly similar Tg, PTMP indicated no phase separation in the crosslinked polymers. The results revealed that the improved properties of GAP ‐ based materials could be achieved by changing the molar ratio of azide versus alkyne and the nanofillers content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45359.  相似文献   

17.
Though over 30 years old, 3D printing has seen an explosion of interest in recent years as technology has become sufficiently advanced and affordable, enabling widespread usage, and investigation of the technique as a method of manufacture. However, the materials commonly used for printing applications frequently suffer from poor mechanical properties and are only suitable for prototyping and non‐load‐bearing objects. We report a stable, tough resin formulation which incorporates spiroacetal molecules into the polymer backbone and displays widely varying and tunable mechanical properties. We characterize the system via (photo‐)DSC, rheology, and tensile testing; further, we detail a comprehensive heat treatment investigation to optimize material performance and elucidate the structure–property relationships present in the printed and non‐printed semi‐crystalline photopolymer. Annealing the material at 40 °C for 120 hours produced a tough thiol‐ene with a homogenous crystal structure. Printed samples exhibited comparable morphology their cast analogues, but suffered from reduced tensile properties as a result of interlayer adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46259.  相似文献   

18.
Epoxidized natural rubber (ENR)–silica hybrids without any other additives were prepared by an open‐mill mixing method at room temperature. The curing characteristics, crosslinking density, mechanical properties, and dynamical mechanical properties were investigated. The results indicate that the ENR–silica hybrid materials could be cured with silica as a crosslinking and reinforcing agent. Attenuated total reflection–Fourier transform infrared spectroscopy and solid‐state 13C‐NMR spectroscopy exposed the characteristics of the interfacial interaction in the hybrids and confirmed the existence of chemical bonds and hydrogen bonds between the epoxy group and Si? OH. Scanning electron microscopy illustrated a good dispersion of silica in the ENR matrix. Meanwhile, the modulus at 100% elongation of the hybrid reached 9.64 MPa when 100‐phr silica was loaded; a similar trend was observed for the hardness. Finally, our findings might extend the concept of rubber curing and open a new space for making an environmentally friendly rubber composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44605.  相似文献   

19.
Flexible poly(dimethylsiloxane) (PDMS) or rigid bisphenol A (BPA) with diglycidyl ether end groups was linked to polyurethane (PU), which was composed of 4,4′‐methylenebis(phenyl isocyanate) as a hard segment and poly(tetramethylene ether)glycol as a soft segment. A control PDMS (CPDMS) series was prepared with an additional deprotonation step by NaH. The spectroscopic, thermal, tensile, shape memory, and low‐temperature flexibility properties were compared with those of plain PU to investigate the effects of linking the flexible PDMS or the rigid BPA on PU. The soft segment melting peaks were not affected by the PDMS content for the PDMS series but disappeared as the BPA content increased in the BPA series. The soft segment crystallization of PU was completely disrupted as the linked BPA content increased in the differential scanning calorimetry results and disappeared in the dynamic mechanical analysis results. The glass transition temperature (Tg) of the BPA series increased with increasing BPA content, whereas that of the PDMS series remained the same. The tensile strength of the PDMS series sharply increased with increasing PDMS content. The shape retention of the BPA series at ?25 °C sharply decreased as the BPA content increased. Finally, the BPA series linked with rigid aromatic BPA demonstrated excellent low‐temperature flexibilities compared with the PDMS series and plain PU. Compared with PUs linked with PDMS, PUs linked with rigid BPA demonstrated a significant change in the cross‐link density, thermal properties, shape retention, and low‐temperature flexibility. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43284.  相似文献   

20.
Triple‐shape‐memory polymers are capable of memorizing two temporary shapes and sequentially recovering from the first temporary shape to the second temporary shape and eventually to the permanent shape upon exposure to a stimulus. In this study, unique three‐component, multilayered films with an ATBTA configuration [where A is polyurethane (PU), B is ethylene vinyl acetate (EVA), and T is poly(vinyl acetate) (PVAc)] were produced as a triple‐shape‐memory material via a forced‐assembly multilayer film coextrusion process from PU, EVA, and PVAc. The two well‐separated thermal transitions of the PU–EVA–PVAc film, the melting temperature of EVA and the glass‐transition temperature of PVAc, allow for the fixing of the two temporary shapes. The cyclic thermomechanical testing results confirm that the 257‐layered PU–EVA–PVAc films possessed outstanding triple‐shape‐memory performance in terms of the shape fixity and shape‐recovery ratios. This approach allowed greater design flexibility and simultaneous adjustment of the mechanical and shape‐memory properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44405.  相似文献   

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