Multiple shape memory effects of trans‐1,4‐polyisoprene and low‐density polyethylene blends

A novel series of shape memory blends of trans‐1,4‐polyisoprene (TPI) and low‐density polyethylene (LDPE) were prepared using a simple physical blending method. The mechanical, thermal and shape memory properties of the blends were studied and schemes proposed to explain their dual and triple shape memory behaviors. It was found that the microstructures played an important role in the shape memory process. In TPI/LDPE blends, both the TPI crosslinking network and LDPE crystalline regions could work as fixed domains, while crystalline regions of LDPE or TPI could act as reversible domains. The shape memory behaviors were determined by the components of the fixed and reversible domains. When the blend ratio of TPI/LDPE was 50/50, the blends showed excellent dual and triple shape memory properties with both high shape fixity ratio and shape recovery ratio. © 2017 Society of Chemical Industry     

Crosslinked polyurethanes with shape memory properties

A series of shape memory polyurethanes (SMPUs) was prepared from polycaprolactone diol (PCL) 4000, 1,4‐butanediol (BDO), dimethylol propionic acid (DMPA), triethylamine, and 4, 4′‐diphenylmethane diisocyanate (MDI), to which excess MDI or glycerin were added to obtain crosslinked shape memory polyurethanes. Their mechanical, thermomechanical, thermal and shape memory properties were investigated by using differential scanning calorimetry (DSC), Fourier‐transform (FT‐IR) spectroscopy, dynamic mechanical analysis (DMA) and tensile testing. The results showed that crosslinked SMPUs have better thermal and thermomechanical properties than those prepared from linear polyurethanes and display good shape memory effects. Copyright © 2005 Society of Chemical Industry     

Synthesis of poly(cyclooctene) by ring‐opening metathesis polymerization: Characterization and shape memory properties

Cis‐cyclooctene was polymerized via ring‐opening metathesis polymerization using a well‐defined ruthenium catalyst (Grubbs' type) under varying reaction conditions. Control over molecular weight was achieved by the inclusion of a chain transfer agent and its influence on the behavior of the obtained polymers was evaluated. The resulting polymers were characterized by means of differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. Taking into account their thermal behavior, samples of appropriate molecular weight were subjected to a suitable treatment by chemical crosslinking to obtain a material showing thermally induced shape memory effect. The material recovers its original shape after several cycles of deformation into different shapes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Triple‐shape‐memory polymer films created by forced‐assembly multilayer coextrusion

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.     

Supramolecular semicrystalline polyolefin elastomer blends with triple‐shape memory effects

Supramolecular polyolefin elastomer blends possessing triple‐shape memory effects were prepared by melt blending of two semicrystalline maleated elastomers (maleated ethylene‐propylene‐diene rubber (mEPDM) and maleated polyethylene‐octene elastomer (mPOE)) in the presence of a small amount of 3‐amino‐1,2,4‐triazole (ATA). The amino group of ATA reacted with the maleic anhydride groups of both elastomers during melt blending to form supramolecular hydrogen‐bonded networks. Dynamic mechanical analysis of the blends showed drops in the storage modulus at two different transition temperatures (T_trans) belonging to the crystalline melting temperatures of each phase as well as a plateau above these two T_trans. This is an essential property for triple‐shape memory behavior. Dual‐shape memory properties of the blends were determined using one‐step programming under three different temperature ranges. When an individual crystalline phase is used for the fixing process, the switching temperature (T_sw) relates to the melting temperature of a particular phase during the recovery process. However, if both crystalline phases are used simultaneously for the fixing process, then the T_sw relates to the higher melting temperature. Cyclic two‐step programming revealed that two different shapes can be fixed, one by EPDM crystallization and the other by POE crystallization, and both programmed shapes can be recovered upon heating above a specific T_sw. © 2016 Society of Chemical Industry     

Blends of sulfonated polysulfone/polysulfone/4,4′‐diaminodiphenyl methane‐based benzoxazine: multiphase structures and properties

To overcome the brittleness of polybenzoxazine and decrease its high curing temperature, sulfonated polysulfone/polysulfone/benzoxazine ternary blends were prepared, and their curing behaviors, phase structures and properties were probed. Sulfonated polysulfone (SPSU) was synthesized firstly, and then SPSU was applied to modify 4,4′‐diaminodiphenyl methane based benzoxazine (BZ‐m) along with polysulfone. The results obtained from differential scanning calorimetry showed that the addition of SPSU efficiently decreased the curing temperature of BZ‐m, and furthermore affected the phase structures of SPSU/PSU/PBZ‐m blends. The phase structures of the corresponding blends were confirmed by scanning electron microscopy and dynamic mechanical analysis to probe the relationship between the microstructures and mechanical properties. According to the results, the blends presented complicated phase structures and exhibited good comprehensive mechanical properties. Moreover, all the blends displayed good thermal stability and the blends with SPSU‐PBZ‐m core ? shell particles and a phase inversion structure exhibited the highest comprehensive mechanical properties. We believe these blends can meet the requirement of applications relating to high strength and good toughness matrix for fiber reinforced composites. © 2014 Society of Chemical Industry     

Multiple shape memory behaviors of natural Eucommia ulmoides rubber and polybutene‐1 composites

We fabricated a series of novel shape memory composites using natural Eucommia ulmoides rubber (EUR) and polybutene‐1 (PB‐1) as basic materials for the first time. The shape memory composites were prepared via simple physical blending and chemical crosslinking methods with co‐continuous architecture and multiple shape memory behaviors. These composites and their preparation methods might be widely used in the field of heat shrinkable tubes. We studied the mechanical, thermal and shape memory properties of the composites, and proposed schemes to explain their dual and triple shape memory effects. In the EUR/PB‐1 composites, both the crosslinking network of the composites and crystalline regions of PB‐1 could function as the fixed domain, and the crystalline zones of EUR and PB‐1 could act as the reversible domain individually or jointly. The composites exhibited excellent dual shape memory properties with blending ratios of 90/10 and 80/20, and good triple shape memory properties with blending ratios of 70/30 and 60/40. © 2018 Society of Chemical Industry     

Shape‐memory polyurethanes minimally crosslinked with hydroxyl‐terminated AB2‐type hyperbranched polyurethanes

A series of shape‐memory polyurethanes based on poly(ϵ‐caprolactone) diol were prepared with novel hydroxyl‐terminated hyperbranched polyurethanes as crosslinkers and were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, wide‐angle X‐ray diffraction, dynamic mechanical analysis, tensile testing, and shape‐memory testing. The molecular weight of the soluble polymers ranged from 5.1 × 10⁴ to 29.0 × 10⁴ g/mol. The differential scanning calorimetry and wide‐angle X‐ray diffraction data indicated that when the crystallinities of the crosslinked polymers were compared to that of linear polyurethane, this parameter was improved when the crosslinker was in low quantity. The storage modulus ratios obtained from the dynamic mechanical analyses data of the crosslinked polymers were also high compared to that of the linear polyurethane. As a result, crosslinked polymers showed better shape‐memory properties compared to the linear polyurethanes. Also, the that incorporation of the hyperbranched polymer as a crosslinker into the polyurethane chain improved the thermal and mechanical properties of the polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Processability,property, and morphology of biodegradable blends of poly(propylene carbonate) and poly(ethylene‐co‐vinyl alcohol)

Biodegradable blends of poly(propylene carbonate) (PPC) and poly(ethylene‐co‐vinyl alcohol) (EVOH) were melt compounded in a batch mixer followed by compression molding. The processability, mechanical properties, thermal behavior, and morphologies of the blends were investigated with torque rheometer, Fourier transform infrared spectroscopy, tensile tests, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Torque rheometry indicated good interfacial miscibility between PPC and EVOH phases, and then fourier transform infrared spectroscopy spectra demonstrated that a certain extent of hydrogen‐bonding interactions between PPC and EVOH matrix in the blends. A study of the mechanical properties and thermal behavior showed that the EVOH incorporation can significantly enhance the tensile strength, thermal stability, and crystallinity of the blends. Moreover, dynamic mechanical analysis and differential scanning calorimetry both revealed that PPC and EVOH were compatible to some extent. Further, scanning electron microscopic examination also revealed the good interfacial adhesion between EVOH and PPC phases. POLYM. ENG. SCI., 47:174–180, 2007. © 2007 Society of Plastics Engineers     

Preparation and Properties of Biodegradable Shape Memory Polylactic Acid/Poly(ε-caprolactone) Blends under Volume Elongational Deformation

In this work, a novel eccentric rotor mixer (ERM), which can generate circulating volume elongational deformation, is employed to prepare biodegradable polylactic acid (PLA)/poly(ε-caprolactone) (PCL) thermo-responsive shape-memory blends without a compatibilizer. The results of scanning electron microscopy (SEM) show that the ERM has more efficient dispersion and compatibilization for blends than conventional Banbury mixers, which is beneficial for shape-memory performance. The results of Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) also confirm the consequences. Then, morphological and mechanical properties and shape memory behaviors of the blends are investigated in detail. Co-continuous morphology is found on EF-PLA50. The blends exhibit remarkable shape-memory performance. The bending shape fixing ratio and recovery ratio of the blends are more than 94% and are still more than 90% after five shape memory cycles. With the increase of PLA content, the shape fixing ratio of blends decreases, while the shape recovery ratio increases and the shape recovery time becomes shorter. All the blends show good mechanical properties.     

Mechanical and shape‐memory behavior of shape‐memory polymer composites with hybrid fillers

Shape‐memory polymer (SMP) materials have several drawbacks such as low strength, low stiffness and natural insulating tendencies, which seriously limit their development and applications. Much effort has been made to improve their mechanical properties by adding particle or fiber fillers to reinforce the polymer matrix. However, this often leads to the mechanical properties being enhanced slightly, but the shape‐memory effect of reinforced SMP composites being drastically reduced. The experimental results reported here suggested that the mechanical resistive loading and thermal conductivity of a composite (with hybrid filler content of 7.0 wt%) were improved by 160 and 200%, respectively, in comparison with those of pure bulk SMP. Also, the glass transition temperature of the composite was enhanced to 57.28 °C from the 46.38 °C of a composite filled with 5.5 wt% hybrid filler, as determined from differential scanning calorimetry measurements. Finally, the temperature distribution and recovery behavior of specimens were recorded with infrared video in a recovery test, where a 28 V direct current circuit was applied. The effectiveness of carbon black and short carbon fibers being incorporated into a SMP with shape recovery activated by electricity has been demonstrated. These hybrid fillers were explored to improve the mechanical and conductive properties of bulk SMP. Copyright © 2010 Society of Chemical Industry     

Study on mechanical,thermal and shape memory properties of polycarbonate/thermoplastic polyurethane blends

The objective of the study is preparation of shape memory blend of polycarbonate (PC) and thermoplastic polyurethane (TPU). Polycarbonate is blended with three types of TPUs and subsequently mechanical, thermal, morphological, and shape memory properties of the PC/TPU blends are studied. When TPU content in the blend is higher than 40% (by weight), the glass transition temperature related to PC is not shown in the differential scanning calorimetry thermogram, indicating loss of PC properties. The 60/40 optimized blend of PC/TPUs exhibits maximum increment of about 1100% in elongation and 43% decrement in tensile strength. The shape recovery of the optimized blend obtained by addition of 40% (by weight) of TPUs in PC polymer is found to be 65% and shape fixity is 97%. These results suggest that the blend of PC/TPU may be utilized for various applications where shape memory property is required including strategic applications.     

Synthesis of shape memory polyurethane/clay nanocomposites and analysis of shape memory,thermal, and mechanical properties

In this study, shape memory polyurethane/clay nanocomposites were synthesized by using two‐step in situ polymerization. The effects of nanoparticle content on mechanical, thermal, and shape memory properties were studied. Soft and hard segments of polyurethanes were based on polycaprolactone (PCL) diol and 4,4′‐diphenylmethane diisocyanate/1,4‐butanediol molar ratio with 70/30, respectively. The differential scanning calorimetry, tensile test, dynamic mechanical thermal analysis, parallel plate rheometer, and X‐ray diffraction were used to evaluate the properties of the nanocomposites. To evaluate shape memory properties, a tensile device equipped with a thermal chamber was used. Glass transition temperature of soft segments has been increased by nanoclay loading. Addition of nanoclay to polyurethane matrix caused to disrupt ordering in hard domains, decrease in elongation and tensile strength. The results show that crystallinity of soft segments and dispersion of nanoparticles affect on the mechanical properties and shape memory behavior of nanocomposites, distinctly. Nanocomposite containing 1 wt% shows the best shape memory properties. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

A new method to improve the stability,tensile strength,and heat resistant properties of shape‐memory epoxy resins: Two‐stages curing

In this article, we design a new thermal curing method: two‐stage curing. The purpose of using this approach is to maintain the excellent shape‐memory property of epoxy resin system after first stage curing, and the material can be folded in small size to storage or transportation and recovery its original shape commodiously by heating temperature. Then, after second stage curing, the stability, glass transition temperature(T_g), and tensile strength of material can be improved effectively. For this aim, a series of mixtures have been prepared. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), tensile test, scanning electron microscope (SEM), dynamic mechanical analysis (DMA), and fold‐deploy shape‐memory test have been used to characterize the feasibility of two‐stage curing process, curing degree, tensile strength, morphology, thermodynamic properties, and shape‐memory performance of these polymers. DSC results show that two independent curing stages can be achieved successfully. Tensile tests and DMA results suggest that tensile strength and heat resistance have been improved after the second curing stage. SEM results reveal that the addition of latent curing agent do not change the fracture mechanism. Furthermore, the fold‐deploy shape‐memory tests prove that the composites after first stage curing possess eximious shape‐memory property. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39882.     

Low‐density polyethylene/plasticized tapioca starch blends with the low‐density polyethylene functionalized with maleate ester: Mechanical and thermal properties

In this study, the mechanical and thermal properties of low‐density polyethylene (LDPE)/thermoplastic tapioca starch blends were determined with LDPE‐g‐dibutyl maleate as the compatibilizer. Mechanical testing for the evaluation of the impact strength and tensile properties was carried our as per standard ASTM methods. Thermogravimetric analysis and differential scanning calorimetry were also used to assess the thermal degradation of the blends. Scanning electron micrographs were used to analyze fracture and blend morphologies. The results show significant improvement in the mechanical properties due to the addition of the compatibilizer, which effectively linked the two immiscible blend components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1109–1120, 2006     

Study of miscibility,crystallization, mechanical properties,and thermal stability of blends of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)

Natural amorphous polymer poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3HB4HB) containing 41 mol % of 4HB was blended with poly(3‐hydroxybutyrate) (PHB) with an aim to improve the properties of PHB. The influence of P3HB4HB contents on thermal and mechanical properties of the blends was evaluated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, stress–strain measurement and thermo gravimetric analyzer. Miscibility of PHB/P3HB4HB blends was mainly decided by the contents of P3HB4HB. When P3HB4HB exceeded 50 wt %, the two polymer phases separated and showed immiscibility. The addition of P3HB4HB did not alter the crystallinity of PHB, yet it diluted the PHB crystalline phase as revealed by DSC studies. DSC and FTIR results showed that the overall crystallinity of the blends decreased remarkably with increasing of P3HB4HB contents. Decreased glass transition temperature and crystallinity imparted desired flexibility for the blends. The ductility of the blends increased progressively with increasing of P3HB4HB content. Thus, the PHB mechanical properties can be modulated by changing the blend composition. P3HB4HB did not significantly improve the thermal stability of PHB, yet it is possible to melt process PHB without much molecular weights loss via blending it with suitable amounts of P3HB4HB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electromagnetic activation of a shape memory copolymer matrix incorporating ferromagnetic nanoparticles

Modified magnetite (Fe₃O₄) was easily mixed in a matrix of a polynorbornene‐based copolymer to realize a nanocomposite of organic polymer and inorganic metal oxide nanoparticles. The crystalline structure and the diameter of the modified Fe₃O₄ were evaluated with X‐ray diffraction and atomic force microscopy, revealing the crystalline Fe₃O₄ nanoparticles in the nanometer size range with an average diameter of 55 nm, a value close to that indicated by dynamic light scattering (68 nm). The transition temperature of the composite of 51 °C was determined using differential scanning calorimetry and the thermal stability and dynamic mechanical properties of the easily formed composite were investigated using thermogravimetry and dynamic mechanical analysis. The shape memory effect was evaluated in terms of shape recovery rate and speed, while thermally and electromagnetically triggered shape memory properties were documented. The recovery time triggered by Fe₃O₄ is 186 s. Copyright © 2011 Society of Chemical Industry     

杜仲胶/聚乳酸形状记忆热塑性硫化胶的制备及性能

将生物基高分子材料杜仲胶（EUG）和聚乳酸（PLA）通过动态硫化技术制备了具有形状记忆性能的热塑性硫化胶（EUG/PLA TPV）。通过扫描电子显微镜、差示扫描量热、动态力学和力学性能测试及热机械循环分析等手段分别考察了EUG/PLA TPV的微观形貌、相容性、热性能、动态力学和力学性能及形状记忆性能。结果表明,增容剂腰果酚有效改善了EUG相与PLA相之间的相容性,从而提高了EUG/PLA TPV的力学性能。当橡塑质量比为5/5时,拉伸强度为10.5 MPa,扯断伸长率达到286%,是纯PLA的约48倍。EUG/PLA TPV具备特殊的双连续相结构,可以赋予其良好的形状记忆性能,形状固定率最高达到93%左右,形状回复率最高达到98%左右。     

Design,synthesis and characterization of novel biodegradable shape memory polymers based on poly(D,L‐lactic acid) diol,hexamethylene diisocyanate and piperazine

A novel series of biodegradable shape memory polyurethane ureas (SMPUUs) were designed and synthesized based on poly(D ,L ‐lactic acid) diol, hexamethylene diisocyanate and piperazine. Their structure, degree of crosslinking, thermal properties, shape memory behaviors and mechanical properties were characterized using Fourier transform infrared and ¹H NMR spectroscopy, weight analysis, differential scanning calorimetry and tensile testing. The results reveal that successfully introducing the piperazine into the backbone of the SMPUUs gives them excellent shape memory behaviors and good mechanical properties. This, in combination with the ideal shape recovery temperature, which can be designed near human body temperature, could make these biodegradable polyurethanes of great interest as potential biomaterials for medical implantations. On increasing the percentage of hard content of the SMPUUs from 9.00 to 12.12 wt%, the shape fixation rate increases from 95.3 to 98.2%, but the shape recovery ratio decreases from 98.6 to 93.2%; also, both the tensile modulus and tensile strength increase, but elongation at break decreases. To profile the advantages of our SMPUUs, a polyurethane based on poly(D ,L ‐lactic acid) diol, hexamethylene diisocyanate and 1,4‐butanediamine was chosen as control. Copyright © 2011 Society of Chemical Industry     

Triple one-way and two-way shape memory poly(ethylene-co-vinyl acetate)/poly(ε-caprolactone) immiscible blends

Triple one-way and two-way shape memory polymers (1W-SMPs and 2W-SMPs) are highly desirable for many practical applications due to the multiple shape transformation. In this work, the blend with co-continuous structure is fabricated based on poly(ethylene-co-vinyl acetate) (EVA) and poly(ε-caprolactone) (PCL), which shows excellent triple one-way and two-way shape memory properties. It is found that the blends have two independent crystallization peaks and two independent melting peaks. With the increase of dicumyl peroxide (DCP) content, the crystallization temperature, melting temperature, and crystallinity of both EVA and PCL in the blends gradually decreases. The blends show great dual and triple one-way shape memory property, and the phenomena of elongation induced by oriented crystallization and contraction induced by melting are clearly seen. Moreover, the blends exhibit remarkable and recyclable triple two-way shape memory performance, with an average shape recovery magnitude of 97.3% and an average actuation magnitude of 50.6%. In terms of the excellent triple one-way and two-way shape memory performance, the EVA/PCL blends may have potential applications in the fields of soft robotics, actuators, and cranes. The new preparation method of triple 2W-SMPs can be used to fabricate other triple 2W-SMPs with commercial polymers.