Thermally and light-triggered reconfigurable shape memory polydopamine/epoxy composite with self-healing and recyclable ability

Shape memory epoxy with self-healing ability has received much more academia and industry attention. In this work, 4-aminophenyl disulfide containing disulfide bonds was used to replace the traditional epoxy resin-curing agent, and the waterborne epoxy resin (sWEP) was composited with the polydopamine (PDA) nanoparticles with photothermal conversion effect through the melt mixing and hot-press molding. As revealed, the addition of 1 wt% PDA increases the tensile strength of sWEP from 36.1 to 50.3 MPa. Specifically, the shape memory properties of the PDA/sWEP composite as manifested by a ca. 97.4% shape memory fixing ratio and ca. 67.8% shape memory recovery ratio. Moreover, the PDA/sWEP composite had the temperature-dependent thermosetting and thermoplastic conversion capabilities, which can be programmed to a new permanent shape via a photothermal-induced plasticity process.     

Thermal and shape memory properties of cyanate/polybutadiene epoxy/polysebacic polyanhydride copolymer

A novel thermal‐induced shape memory polymer was synthesized by copolymerization of a new kind of epoxy resin‐polybutadiene epoxy (PBEP), bisphenol A‐type cyanate ester (BACE), and polysebacic polyanhydride (PSPA) with different mass ratios. Fourier transform infrared spectroscopy (FTIR), bending test, dynamic mechanical analysis (DMA), and shape memory property were investigated systematically. It was found that the PSPA significantly enhanced the bending strength and flexural modulus. The DMA results showed that the glass transition temperature reduced with increasing content of PSPA. Furthermore, the shape memory tests proved that the copolymer possessed excellent shape memory properties. The shape recovery time decreased with increasing content of PSPA and temperature. The shape memory rate increased as the PSPA content increased. The shape recovery ratio decreased with increasing cycle times. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42045.     

Study on the thermal-induced shape memory effect of pyridine containing supramolecular polyurethane

In this paper, a series of pyridine containing supramolecular polyurethanes (PUPys) were synthesized from BINA, HDI and BDO. Then the structure, morphology and thermal-induced shape memory effect (SMEs) of PUPys were investigated systematically. Results show that strong hydrogen bonding is formed in the urethane group as well as in the pyridine ring; and phase separation consisting of soft phase and hard phase occurs in the PUPy. In addition, it is found that the lower limit of BINA content for PUPys exhibiting good SMEs is 30 wt%. PUPys with higher BINA content show higher shape fixity, higher shape recovery and better strain stability. Moreover, the shape recovery force increases with the decreasing of BINA content. Finally, the temperature-dependent FT-IR spectra support that the hydrogen bonding in the pyridine ring serves as the molecular switch; while the hydrogen bonding in the urethane groups acts as the physical netpoints for the utilization of PUPys as SMMs.     

热致感应型形状记忆高分子材料与纤维

介绍了热致感应型形状记忆高分子材料的机理、制备方法及其应用,重点介绍了热致感应型形状 记忆纤维的混纺和后整理生产技术及国内外研究发展状况。指出今后应大力开发热致感应形状记忆纤维的 直接纺丝生产技术,提高纤维的形变回复力及尺寸稳定性,纤维的应用前景看好。     

Dynamic mechanical properties of sandwich‐structured epoxy beam composites containing poly(ethyleneterephthalate)/poly(ethyleneglycol) copolymer with shape memory effect

To make smart vibration‐controlling composite laminate, a few poly(ethylene terephthalate) (PET) and poly(ethylene glycol) (PEG) copolymers with shape memory ability were prepared. After selecting the best composition of PET–PEG copolymer in mechanical properties, a crosslinking agent such as glycerine, sorbitol, or maleic anhydride (MA) was included for crosslinked copolymer, followed by analysis of its effect on mechanical, shape memory, and damping properties. The highest shape recovery was observed for copolymer with 2.5 mol % of glycerine, and the best damping effect indicating vibration control ability was from copolymer with 2.5 mol % of sorbitol. With the optimum copolymers in hand, sandwich‐structured epoxy beam composites fabricated from an epoxy beam laminate and crosslinked PET–PEG copolymer showed that impact strength increased from 1.9 to 3.7 times depending on the type of copolymer, and damping effect also increased as much as 23 times for the best case compared to epoxy laminate beam alone. The resultant sandwich‐structured epoxy beam composite can be utilized as structural composite material with vibration control ability, and its glass transition temperature can be controlled by adjustment of PET, PEG, or crosslinking agent composition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3141–3149, 2003     

Effect of molecular weight on shape memory behavior in polyurethane films

Understanding the relationship between the number‐average molecular weight (M_n) and the shape memory behavior of polymers is crucial for a complete picture of their thermomechanical properties, and hence for the development of smart materials, and, in particular, in textile technology. We report here on the study of shape memory properties as a function of M_n of polymers. Shape memory polyurethanes (SMPUs) of different M_n were synthesized, with various catalyst contents or molar ratio(r = NCO/OH) in the composition. In particular, two types of SMPU, namely T_m and T_g types according to their switch temperature type, were synthesized to compare the influence of M_n on their shape memory behavior. X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, and shape memory behavior results for the SMPUs are presented. The results indicate that the melting temperature (T_m), the glass transition temperature (T_g), the crystallinity, and the crystallizability of the soft segment in SMPUs are influenced significantly by M_n, before reaching a critical limit around 200 000 g mol^?1. Characterization of the shape memory effect in PU films suggests that the T_m‐type films generally show higher shape fixities than the T_g‐type films. In addition, this shape fixity decreases with increasing M_n in the T_g‐type SMPU, but the shape recovery increases with M_n in both types of SMPU. The shape recovery temperature, in contrast, decreases with M_n as suggested by the result of their thermal strain recovery. It is concluded that a higher molecular weight (M_n > 200 000 g mol^?1) is a prerequisite for SMPUs to exhibit higher shape recovery at a particular temperature. Copyright © 2007 Society of Chemical Industry     

热固性环氧树脂形状记忆效应研究

将新型的高分子固化剂与环氧树脂(EP)进行共混,经适度交联固化后制备出一种具有较低玻璃化转变温度(Tg)的无定型EP体系,并对该EP固化体系的力学性能、形状记忆特性和动态力学性能等进行了研究。结果表明:适度交联固化的EP体系具有良好的形状记忆特性,固化剂用量是影响该形状记忆体系综合性能的主要因素;其最大形变恢复率均为100%,形变恢复速率基本上随固化剂用量增加而增大,最大形变恢复速率为0.023 s-1;形变固定率随固化剂用量增加而减小,当w(固化剂)=37.5%或54.5%时,形变固定率为100%或96%。     

Shape memory effect and mechanical properties of cyanate ester-polybutadiene epoxy copolymer

A type of thermal-induced shape memory polymer was fabricated using a new epoxy resin-polybutadiene epoxy (PBEP) and bisphenol A-type cyanate ester in different mass ratios. Mechanical performance, thermal properties, and shape memory behaviors were investigated systematically. This polymer system presented good shape memory properties. The deformation recovery speed increased with the increase in the amount of PBEP. The maximum deformation recovery speed was 0.0128 s^?1, and the minimum value was 0.0073 s^?1. The deformation recovery rate was almost 100 %.     

Masonry composite material made of limestone powder and fly ash

Large amounts of fly ash (FA) and limestone powder (LP) wastes are accumulating in countries all over the world. Most of these wastes are abandoned and cause certain serious environmental problems and health hazards. In this study, LP waste and class-C FA were used to produce a composite material without the addition of portland cement. LP was mixed with the FA at levels of 10, 20 and 30% by volume in the samples. LP and FA were mixed, wetted and compressed under high pressure in a steel mould. The compressive and flexural strengths were measured, and ultrasonic pulse velocity tests were performed on samples at ages of 7, 28 and 90 days. Density, water absorption and thermal conductivity values were also determined for the samples aged for 28 days. Preliminary results obtained from the tests indicate that masonry composites can be produced using LP, FA and water.     

Fourier transform infrared study of supramolecular polyurethane networks containing pyridine moieties for shape memory materials

Non‐covalent interactions are increasingly used in the molecular self‐assembly of well‐defined structures. In this study, a series of pyridine‐containing polyurethanes (PUPys) were synthesized with diisocyanates and pyridine derivatives. Fourier transform infrared spectroscopy was employed to identify the vibration frequencies and investigate the relationship of shape memory effect (SME) and hydrogen‐bonded supramolecular structure of the PUPys. The results show that a large fraction of strong hydrogen bonds are formed in the urethane group as well as in the pyridine ring. Moreover, the hydrogen bonding in the pyridine ring not only shows a response to a temperature stimulus in the PUPys, but is also responsive to moisture in N,N‐bis(2‐hydroxylethyl)isonicotinamine (BINA)/hexamethylene diisocyanate (HDI)‐based PUPys; the hydrogen bonds in the urethane group have a higher dissociation temperature and show little response to moisture absorption. Accordingly, the PUPys are expected to show thermally induced and moisture‐induced SMEs. Finally, the shape recovery process of films in the shape of flowers induced by temperature and moisture supports the idea that the PUPys could be used as thermally induced shape memory polymers (SMPs), and the BINA/HDI‐based PUPys could be used as moisture‐sensitive SMPs. Copyright © 2009 Society of Chemical Industry     

Blocking of soft segments with different chain lengths and its impact on the shape memory property of polyurethane copolymer

The arrangements, whether block or random type, of the soft segments of polyurethane block copolymers prepared with MDI and two kinds of poly(tetramethylene glycol) (PTMG; MW of 1000 or 2000) in various ratios were compared for possible effects on the physical properties of the copolymers. A long soft segment, PTMG‐2000, was superior in all mechanical properties (strain, stress, and modulus) because a long chain length could provide more motional freedom than a short one (PTMG‐1000) could and therefore was helpful in forming strong interchain attractions among hard segments. Inclusion of more PTMG‐2000 led to a lower T_g and a peak shift in infrared spectra. The arrangement of two soft segments in a block‐type copolymer, a key finding in this study, was controlled by separately synthesizing two prepolymers, each with a different chain length, and connecting two prepolymers in a second step. Random‐type copolymers prepared for purposes of comparison were allowed to react with two PTMGs in one step. Two types of copolymers were compared, and the reason for the differences in the shape memory property are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1435–1441, 2007     

碳纤维/环氧树脂复合材料的改性及改性机理

介绍了碳纤维/环氧树脂复合材料中碳纤维的增强机理.综述了纳米材料、聚合物对碳纤维/环氧树脂复合材料的改性进展,并总结了相应的改性机理.探索新型柔和的碳纤维表面处理技术以及对碳纤维表面接枝将是碳纤维/环氧树脂复合材料改性的发展方向.     

Electroactive shape memory performance of polyurethane composite having homogeneously dispersed and covalently crosslinked carbon nanotubes

The electroactive shape memory of carbon nanotube-filled polyurethane composites, prepared by conventional blending, in situ and cross-linking polymerization, is studied in terms of the dispersion of the tubes. The covalently bonded tubes are homogeneously dispersed within the polyurethane by introducing carboxyl groups on the sidewall of the tubes and selecting a cross-linking polymerization method. The resultant composites, which have 92% shape retention and 95% shape recovery, are expected to be used as preferential materials in various actuators.     

Shape memory effect and properties memory effect of polyurethane

The relationship between shape and properties memory effect, especially viscoelastic properties of polyurethane under study is the main aim of this research work. Tensile tests have been performed in order to introduce 100% of deformation in the polyurethane samples. Under this deformation, stress–relaxation experiments have been performed in order to eliminate the residual stresses. This deformation of the samples has been fixed by cooling. Recovery tests, then, were carried out at different isothermal temperatures that varied from 30°C to 60°C. Viscoelastic behavior has been studied by a biparabolic model and by using the Cole–Cole method. It was shown that this model describes the behavior of the polymer at the different states of shape memory tests. The constants of this model then have been determined. This study leads to a better understanding of the mechanism of shape memory effect. The comparison between the virgin polymer and the polymer after a recovery test by DMTA (dynamic mechanical thermal analysis) and by Cole–Cole method has illustrated that the polymer does not obtain its initial properties even when it was totally regained its initial shape. These results have been confirmed by three successive shape memory tests on the same sample and by comparing the mechanical characteristics of different cycles because “shape memory effect” and “properties memory effect” do not follow the same mechanisms. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚氨酯-环氧树脂复合乳液的合成与性能研究

以六亚甲基二异氰酸酯(HDI)、聚醚二元醇(Diol-1000)、二羟甲基丙酸(DMPA)、乙二胺(EDA)和环氧树脂(E-20)等为主要原料制备了聚氨酯-环氧树脂复合乳液。研究了聚醚二元醇含量、羧基含量对复合乳液的稳定性及涂膜柔韧性和耐水性等的影响,用电化学阻抗技术研究了涂层的耐腐蚀性能。     

High-efficiency shape memory copolymers of polycaprolactone/thermoplastic polyurethane fabricated via in situ ring-opening polymerization

Shape memory blends of polycaprolactone/thermoplastic polyurethane (PCL/TPU) were prepared by in situ ring-opening polymerization (ROP) of ε-caprolactone (CL) and thermoplastic polyurethane (TPU). Fourier infrared spectrometer and ¹H-NMR were used to characterize the chemical structure of PCL/TPU copolymers. The results show that TPU has been involved in the ROP of CL, leading to the formation of copolymers with homogeneous morphologies. Besides, pure PCL and all the blends exhibit an excellent shape fixation ratio of 100%, due to their high crystallinity. When a small amount of TPU is introduced, the crystallinity of PCL decreases, and as a result, the shape recovery ratio of the copolymer is enhanced compared with pure PCL. However, with the increased loading of TPU, the content of PCL as the reversible phase decreases and the storage modulus of the PCL/TPU blend declines, so the driving force for the blends to return from the temporary shape to the initial shape becomes smaller, leading to a decrease in the shape recovery ratio. Notably, when the amount of TPU is only 5%, the shape recovery ratio of the blend could reach 83.3%, which is 26% higher than that of pure PCL, and meanwhile, the tensile strength of the blend decreases slightly. This study provides a new strategy for the design of shape-memory materials with high shape-memory properties.     

Lateral flexible linking of polyurethane copolymer and the effect on shape recovery and tensile mechanical properties

Shape memory polyurethane (SMPU), flexibly crosslinked via a polyethyleneglycol (PEG) spacer attached to its side through an allophanate group, was tested for shape memory and compared with a linear SMPU. The new SMPU was composed of 4,4′‐methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG‐2000), and 1,4‐butanediol (BD), and included polyethyleneglycol (PEG‐200) as a spacer. A second MDI, linked to the carbamate group of the first MDI, served as the connecting point for the PEG‐200. Two types of SMPU, differing according to their soft segment (PTMG‐2000) and linker (PEG‐200) contents, were compared in mechanical and shape memory properties. In the best case, a 780% increase in maximum stress was attained without any sacrifice in strain for the new material compared with the linear polymer. In particular, the stress–strain curve showed that the PEG‐crosslinked SMPU had superior tensile mechanical properties. Its shape recovery was as high as 99%, which is the best value we have measured for an SMPU. After four cyclic tests, shape recovery remained greater than 95%. Shape retention of the best SMPU remained above 93% even after four cyclic tests. Here, results demonstrating the extraordinary shape memory properties of these types of SMPU, together with differential scanning calorimetry (DSC) and infrared spectroscopy data, are analyzed and discussed. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

碳纤维增强环氧树脂基复合材料的性能研究

研究了WBS-3环氧树脂固化体系的反应特性,分析了该固化体系浇铸体的性能;并以碳纤维(T-700S)为增强材料,采用手糊成型螺栓加压工艺制备了WBS-3/T-700S复合材料,研究了复合材料的常温力学性能、高温力学性能、水煮后力学性能和动态力学性能,并对弯曲断面进行分析。研究结果表明,WBS-3树脂基体黏度低、适用期长且韧性好,适合于手糊成型、缠绕成型等低成本制造工艺;由此制得的WBS-3/T-700S复合材料具有优良的力学性能和耐高温性能,其弯曲强度为1434MPa,拉伸强度为1972MPa,剪切强度为76.1MPa,玻璃化温度(Tg)超过210℃;该WBS-3/T-700S复合材料具有很好的界面粘接性(树脂对纤维的浸润性良好)、较低的空隙率且纤维分布均匀。     

Effect of cationic group content on shape memory effect in segmented polyurethane cationomer

To illustrate the importance of cationic groups within hard segments on shape memory effect in segmented polyurethane (PU) cationomers, the shape memory polyurethane (SMPU) cationomers composed of poly(ε‐caprolactone) (PCL), 4,4′‐diphenylmethane diisocyanate (MDI), 1,4‐butanediol (BDO), and N‐methyldiethanolamine (NMDA) or N,N‐bis(2‐hydroxyethyl)isonicotinamide (BIN) were synthesized. The comparison of shape memory effect between NMDA series and BIN series was made. The relations between the structure and shape memory effect of the two series of cationomers with various ionic group contents were investigated. It is observed that the stress at 100% elongation is reduced for these two series of PU cationomers with increasing ionic group content. Especially for NMDA series, the stress reduction is more significant. The fixity ratio and recovery ratio of the NMDA series can be improved simultaneously by the insertion of cationic groups within hard segments, but not for the BIN series. Characterizations with DSC and DMA suggest that the crystallibility of soft segment in SMPU cationomers was enhanced by incorporation of ionic groups into hard segments, leading to a relative high degree of soft segment crystallization; compared with the corresponding nonionomers, incorporation of charged ionic groups within hard segments can enhance the cohesion force among hard segments particularly at high ionic group content. This methodology offers good control of the shape memory characteristic in thin films and is believed to be beneficial to the shape memory textile industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 545–556, 2007