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.     

Synthesis and characterization of novel low‐dielectric cyanate esters. II

A novel cyanate ester, 2,6‐dimethyl phenol dipentene cyanate ester (DPCY), was successfully synthesized from cyanogen bromide with 2,6‐dimethyl phenol dipentene novolac, which was synthesized from dipentene and 2,6‐dimethyl phenol. For the purpose of increasing the mobility of residual DPCY during the final stage of curing and achieving a complete reaction of cyanate groups, a small quantity of a monofunctional cyanate ester, 4‐tert‐butyl phenol cyanate ester, was added to DPCY to form a cyanate ester copolymer. The thermal properties of the cured cyanate ester resins were studied by dynamic mechanical analysis, dielectric analysis, and thermogravimetric analysis. These data were compared with those of the commercial bisphenol A cyanate ester system. The cured modified cyanate ester exhibited a dielectric constant of 2.59–2.50, a dissipation factor of 0.0055–0.0089, and moisture absorption of 0.91–1.17%; these values were all lower than those of the as‐cured bisphenol A dicyanate system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 369–379, 2005     

Thermomechanical properties and shape memory effect of epoxidized natural rubber crosslinked by 3‐amino‐1,2,4‐triazole

A thermally induced shape memory polymer based on epoxidized natural rubber (ENR) was produced by curing the ENR with 3‐amino‐1,2,4‐triazole as a crosslinker in the presence of bisphenol‐A as a catalyst. Dynamic mechanical and tensile analysis was conducted to examine the variation of glass transition temperature, stiffness, and extensibility of the vulcanizates with the amount of curatives. Shape memory properties of the ENR vulcanizates were characterized by shape retention and shape recovery. It was revealed that the glass transition temperature of the ENR vulcanizates could be tuned well above room temperature by increasing the amount of curing agents. Also, ENR vulcanizates with T_g higher than ambient temperature showed good shape memory effects under 100% elongation, and the response temperatures of the recovery were well matched with T_g of the samples. Copyright © 2006 Society of Chemical Industry     

Influence of cyanate content on the morphology and properties of epoxy resins with phenolphthalein poly(ether ketone)

Phenolphthalein poly(ether ketone) (PEK‐C) was blended with the diglycidyl ether of bisphenol A epoxy resin and bisphenol A dicyanate ester. The effect of cyanate content on cure behaviors, thermal and mechanical properties of PEK‐C/epoxy/cyanate mixtures was investigated. As results, the increase of cyanate content slightly hindered the cure reaction of the mixtures. Fourier transform infrared results indicated that the curing reaction of the cured mixtures was complete. When the cyanate ester content increased, the flexural properties and T_g values were enhanced, and the initial thermal decomposition temperature was reduced. A significant improvement in fracture toughness was obtained when the cyanate group in the mixtures was excessive. The fracture toughness can be well explained by SEM observations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(ether urethane) flexible cyanate ester resins: Synthesis,characterization, and performance in commercial epoxy and polyurethane applications

A poly(ether urethane)‐based cyanate ester resin (PEUCER) with a biphenyl polyether backbone obtained from polymeric 4,4′‐diphenylmethanediisocyanate, bisphenol A, polyether polyols of three different molecular weights, and cyanogen bromide was synthesized to obtain a polymer with better functional and physical properties, such as adhesion, flexibility, and thermal stability. The synthesis of the poly(ether urethane)‐based 4,4′‐(oxybiphenyl propane) cyanate ester involved three steps: the formation of the poly(ether urethane) NCO‐terminated prepolymer, the formation of the OH‐terminated poly (ether urethane) prepolymer (PEU–PP), and the esterification reaction of cyanate to produce PEUCER. PEUCER was cyclotrimerized to yield a triazine‐ring‐containing polymer, which possessed better adhesion at high temperatures and better impact resistance. PEU–PP and PEUCER were characterized with wet chemical analysis, spectral methods, and thermal methods. PEUCER showed better performance with respect to thermal and adhesion properties with a single‐part polyurethane lamination adhesive and also showed better performance as a toughening agent in a two‐part epoxy laminate system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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 %.     

Short glass fiber reinforced radiation crosslinked shape memory SBS/LLDPE blends

The poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) and linear low density polyethylene(LLDPE) were blended and irradiated by γ‐rays to prepare shape memory polymer(SMP). Various amounts of short glass fiber (SGF) were filled into SMP to form a novel shape memory SGF/SBS/LLDPE composite. The effect of SGF on the shape memory SGF/SBS/LLDPE composite was studied in terms of mechanical, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and shape memory effects. It is found that the SGF act as reinforcing fillers and significantly augment the glassy and rubbery stated moduli, tensile strength and shape memory properties. When SGF content is <2.0 wt %, full recovery can be observed after only several minutes at different temperatures and shape recovery speed reduces as the SGF content increases. The shape recovery time decreases as the temperature of the shape memory test increases and the shape recovery rate decreases with increment of cycle times. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40691.     

Curing behavior and thermal mechanical properties of cyanate ester blends

Cyanate esters are a class of important thermally resistant polymers. To tailor their processability and thermomechanical properties, a series of cyanate ester blends based on a trifunctional novolac cyanate ester (HF‐5), a difunctional bisphenol E cyanate ester (HF‐9), and a reactive catalyst [2,2′‐diallyl bisphenol A (DBA)] were formulated. The effect of the blend composition on the rheology and curing behavior of these cyanate ester blends and the corresponding thermal and mechanical properties of the cured cyanate ester blends was studied. The results showed that HF‐5 contributed to good mechanical property retention at high temperatures because of its trifunctionality, whereas HF‐9 imparted processability by reducing the viscosity and extending the pot life of the formulated cyanate ester blends at the processing temperature. On the basis of the results, an optimal cyanate ester blend suitable for resin transfer molding was determined: the HF‐5/HF‐9/DBA weight ratio of 80 : 15 : 5 exhibited good processability and thermomechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4284–4290, 2006     

Synthesis and properties of shape memory graphene oxide/polyurethane chemical hybrids

Graphene oxide modified chemically with allyl isocyanate (iGO) was incorporated in various amounts into acrylate‐terminated polyurethane (PU) via UV curing. The effects of this incorporation on the morphological, mechanical, dynamic mechanical, thermal and shape memory properties of the resulting hybrids were examined. The iGO nanoparticles incorporated into the PU chains acted as both multifunctional crosslinks and reinforcing fillers, and the effects were most pronounced at low iGO contents (0.5 and 1.0 wt%). Consequently, the glassy and rubbery state moduli, yield strength, glass transition temperature, shape fixity and shape recovery ratios were increased on adding up to 1 wt% iGO. At higher iGO loadings, the values of most of these properties decreased due to aggregation and the auto‐inhibition of allyl compounds. © 2013 Society of Chemical Industry     

Polyethylenimine‐Based Shape Memory Polyurethane with Low Transition Temperature and Excellent Memory Performance

Flexible shape memory polyurethanes (SMPUs) are the favorable candidates as a coating or substrate for wearable smart textiles, electronics, and biomedical applications. However, conventional SMPUs (e.g., 1,4 butanediol (BDO)‐based) are not suitable in these applications due to high rigidity, poor mechanical properties, low shape recovery, and high transition temperature. Herein, a polyethylenimine (PEI)‐based SMPU with low transition temperature and tailored properties are reported. The synthesized SMPU are characterized, and their properties are compared with BDO‐SMPUs. The chemical structure of PEI is explored to improve thermal and mechanical properties and to assess their effect on shape memory behavior. The bulky nature of PEI plays a critical role in lowering transition temperature and introduces flexibility in the structure at room temperature. A drop in Young's modulus is found from 13.6 MPa in BDO‐SMPU to 6.2 MPa in PEI‐SMPU. Simultaneously, tensile strength is increased from 3.77 MPa in BDO‐SMPU to 11.85 MPa in PEI‐SMPU. Owing to the improved mechanical properties in PEI‐SMPU, 100% shape recovery is observed, which displays a reproducible trend in ten repetitive cycles due to the presence of reversible physical crosslinks. Therefore, it is envisioned that this can serve as a potential shape memory material in smart wearable technologies.     

PPO–PC block‐copolymers used as compatibilizers in PS/PC blends

Block‐copolymers containing poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and polycarbonate of bisphenol A (PC) segments were employed as compatibilizers in polystyrene (PS)/PC blends. Block‐copolymers were prepared starting from oligomeric diols‐terminated PPO and PC. The poly(phenylene ethers) was obtained by oxidative coupling of 2,6‐dimethyl‐phenol in presence of tetramethyl bisphenol A. The copolymers were obtained with a chain extension reaction between the starting oligomers using bischloroformate of bisphenol A or phosgene as coupling agent. PS/PC blends, cast from chloroform solutions or mixed by melt, were studied by differential scanning calorimeter (DSC), dynamic‐mechanical thermal analysis (DMTA), and optical microscopy (OP). The thermal and morphological analyses showed a clear compatibilization effect between PS and PC, if PPO–PC copolymer is added when blending is performed in the melt; in addition, also mechanical properties are increased when compared with blends without PPO–PC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4654–4660, 2006     

Mechanical and morphological properties of organic–inorganic,hybrid, clay‐filled,and cyanate ester/siloxane toughened epoxy nanocomposites

Organic–inorganic hybrids involving cyanate ester and hydroxyl‐terminated polydimethylsiloxane (HTPDMS) modified diglycidyl ether of bisphenol A (DGEBA; epoxy resin) filled with organomodified clay [montmorillonite (MMT)] nanocomposites were prepared via in situ polymerization and compared with unfilled‐clay macrocomposites. The epoxy‐organomodified MMT clay nanocomposites were prepared by the homogeneous dispersion of various percentages (1–5%), and the resulting homogeneous epoxy/clay hybrids were modified with 10% HTPDMS and γ‐aminopropyltriethoxysilane as a coupling agent in the presence of a tin catalyst. The siliconized epoxy/clay prepolymer was further modified separately with 10% of three different types of cyanate esters, namely, 4,4′‐dicyanato‐2,2′‐diphenylpropane, 1,1′‐bis(3‐methyl‐4‐cyanatophenyl) cyclohexane, and 1,3‐dicyanato benzene, and cured with diaminodiphenylmethane as a curing agent. The reactions during the curing process between the epoxy, siloxane, and cyanate were confirmed by Fourier transform infrared analysis. The results of dynamic mechanical analysis showed that the glass‐transition temperatures of the clay‐filled hybrid epoxy systems were lower than that of neat epoxy. The data obtained from mechanical studies implied that there was a significant improvement in the strength and modulus by the nanoscale reinforcement of organomodified MMT clay with the matrix resin. The morphologies of the siloxane‐containing, hybrid epoxy/clay systems showed heterogeneous character due to the partial incompatibility of HTPDMS. The exfoliation of the organoclay was ascertained from X‐ray diffraction patterns. The increase in the percentage of organomodified MMT clay up to 5 wt % led to a significant improvement in the mechanical properties and an insignificant decrease in the glass‐transition temperature versus the unfilled‐clay systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Improved mechanical properties of shape‐memory polyurethane block copolymers through the control of the soft‐segment arrangement

High‐performance shape‐memory polyurethane block copolymers, prepared with two types of poly(tetramethylene glycol) (PTMG) used as soft segments, were investigated for their mechanical properties. Copolymers with a random or block soft‐segment arrangement had higher stresses at break and elongations at break than those with only one kind of PTMG. Random copolymers with fewer interchain interactions showed higher elongation than block copolymers. All the copolymers had shape‐recovery ratios higher than 80%. In dynamic mechanical testing, the glass‐transition behavior clearly depended on the soft‐segment arrangement: random copolymers had only one glass‐transition peak, whereas block copolymers showed two separate glass‐transition peaks. Overall, the control of the soft‐segment arrangement plays a vital role in the development of high‐performance shape‐memory polyurethane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2410–2415, 2004     

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.     

Synthesis and properties of waterborne poly(urethane urea)s containing polydimethylsiloxane

To obtain flexible waterborne poly(urethane urea) (WBPU) coatings with functionalities such as shape recovery and water resistance, we synthesized a series of WBPUs by a prepolymer mixing process from hexamethylene diisocyanate, polyol, 2,2‐bis(hydroxymethyl) propionic acid, ethylenediamine, and triethylamine with polyol blends [hydroxyl‐terminated polydimethylsiloxane (PDMS) with a number‐average molecular weight of ≈ 550 and poly(tetramethylene oxide) glycol (PTMG) with a number‐average molecular weight of 650] of different molar ratios. The effects of the PDMS content in PDMS/PTMG on the dynamic thermal and mechanical properties, hardness, tensile properties, water resistance (water absorption, contact angle, and surface energy), and shape‐memory properties of WBPU films were investigated. As the molar percentage of PDMS in WBPUs increased, the storage modulus, tensile strength and modulus, elongation at break, hardness, and shape‐retention rate (30–15%) decreased; however, the water resistance and shape‐recovery rate (80–90%) increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dynamic mechanical and shape memory properties of polybenzoxazines based on aminopropyl‐terminated siloxanes

Four siloxane‐containing benzoxazine monomers and telechelic benzoxazine oligomers were synthesized from 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane, α,ω‐bis(3‐aminopropyl)polydimethylsiloxane, phenol, o‐allylphenol, and formaldehyde. The length of the siloxane segment affects the polymerization reaction of the benzoxazine monomers and telechelic benzoxazine oligomers. The dynamic mechanical properties of the corresponding polybenzoxazines depend primarily on the structure of phenol and the length of the siloxane segment. The polybenzoxazines exhibit one‐way dual‐shape memory behavior in response to changes in temperature. The thermally induced shape memory effects of the polybenzoxazines were characterized by bending and tensile stress–strain tests with a temperature program based on their glass transition temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44121.     

Synthesis and characterization of high temperature cyanate-based shape memory polymers with functional polybutadiene/acrylonitrile

New thermosetting shape memory cyanate polymers (SMCPs) modified with polybutadiene/acrylonitrile (PBAN) were synthesized and compared with polyethylene glycol (PEG)-modified SMCPs for integration into the family of high temperature shape memory polymers with controllable glass transition temperatures (T_g) used in the aerospace industry. The materials were characterized in terms of microstructure, thermal properties, mechanical properties and shape memory properties by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and tensile tests. Differing from the SMCP with PEG, the new cyanate-based shape memory polymer with PBAN (T_g ∼255.1.0 °C) had better shape memory properties and higher thermal stability (relatively high initial degradation temperature and high char residue value at 800 °C). Both of the SMCPs with PBAN and PEG displayed exceedingly high glass transition temperatures over 241.3 °C and higher toughness than unmodified polycyanurate. These qualities render them desirable candidates as matrices in polymer composites, particularly for space applications.     

Bio-based shape memory epoxy resin synthesized from rosin acid

A bio-based shape memory epoxy resin (DGEAPA) was synthesized from rosin to achieve the sustainability of shape memory epoxy resin, and its chemical structure was determined by FTIR and ¹H NMR. For comparison, a petroleum-based epoxy, diglycidyl ester of terephthalic acid (DGT) having one benzene ring, was also synthesized. The properties, including thermal and mechanical properties, as well as shape memory properties of the epoxy resins cured with poly(propylene glycol)-bis (2-aminopropyl ether) (D230), were studied by differential scanning calorimeter, dynamic mechanical analysis, thermogravimetric analysis, tensile test, and U-type shape memory test. The effect of the stoichiometric ratio n_DGEAPA/n_DGT on the properties was studied as well. The thermal and mechanical properties, including thermal stability, glass transition temperature, tensile strength, and modulus of the cured epoxy systems, were found to be increased with DGEAPA incremental content, and the cured neat rosin-based epoxy system exhibited the highest properties. Both the cured rosin-based epoxy and the cured DGEAPA showed significant shape memory performance. Meanwhile, the rosin ring structure made the cured rosin-based epoxy systems display excellent shape recovery fixity, while small lower shape recovery and shape recovery rate relative to the cured neat DGT system. Therefore, the rosin-based epoxy resin has a great potential in the shape memory material applications.     

High glass transition temperature shape-memory materials: Hydroxyl-terminated polydimethylsiloxane-modified cyanate ester

Hydroxyl-terminated polydimethylsiloxane (HTPDMS) and hydrogenated bisphenol A-type epoxy resin (AL-3040) were coreacted with a silane coupling agent (KH-550) to form an AL-3040 epoxy resin–HTPDMS block copolymer. Then, the copolymer was used as a compatibilizer to modify cyanate ester with different mass ratios. Subsequently, the blend was cured to form HTPDMS-modified shape-memory cyanate ester. The soft Si─O─Si segments of HTPDMS act as a flexible unit that can be grafted with the crosslinked triazine structures of cyanate ester. It was excellent for the toughening modification of cyanate ester. With increasing mass ratio of compatibilizer and cyanate ester, the tensile strength and glass transition temperature (T _g) of HTPDMS-modified cyanate ester were decreased, whereas impact strength and elongation at break were increased. The shape-memory tests exhibited that HTPDMS-modified cyanate ester systems have excellent shape-memory properties with a shape recovery rate of >96% and shape fixity rate of >97% and a recovery time of less than 110 s. Furthermore, Thermo-Gravimetric Analyzer (TGA) tests showed that HTPDMS-modified cyanate ester exhibited good thermal stability; the temperature of 10% mass loss was high at 365 °C. The char yield was increased with increasing contents of compatibilizer at 800°C. Therefore, HTPDMS modified cyanate ester exhibited much better heat resistance at high temperature. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48641.     

High temperature shape memory polyimide ionomer

In this work, a high temperature shape memory polymer based on polyimide (PI) ionomer is prepared by introducing ionic crosslinked interaction. The ionic crosslinked points are introduced to polymer networks through the reaction between polyamic acid and calcium hydroxide before thermal imidization. The crosslinked reaction, microtopography, mechanical, thermal, and shape memory properties of PI ionomers are systematically investigated. The results show the introduction of ionic crosslinked interaction could enhance the glass transition temperature, mechanical, and shape recovery performance of ODA‐ODPA, a PI. The prepared ionomers exhibit good high temperature shape memory properties around 270 °C. The shape fixation and shape recovery ratio are over 99% and 90%, respectively. This method provided a new sight of preparing high temperature shape memory polymer, which could be used in severe conditions, like aerospace industry field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43630.