Thermoset Films Research Articles

Modified rice husk as component in recyclable and biodegradable epoxy thermosets

Rice husk (RH), an abundant agricultural residue, was successfully chemically modified and used as a component in reprocessable and biodegradable epoxy thermosets. First, RH was subjected to alkaline treatment to increase the cellulose content followed by succinylation and curing with trimethylolpropane triglycidyl ether to form the thermoset films. The chemical structure of the different intermediates and thermosets was confirmed by Fourier transform infrared spectroscopy. The developed thermoset films had good solvent resistance against common organic solvents and good thermal stability as measured by thermogravimetry with peak temperatures of 347–387 ℃, char residues of 16–20% and limiting oxygen index values of 24–26%, respectively. The films could be thermally reprocessed by hot-pressing with excellent recovery of the mechanical properties (92–96% recovery of tensile stress). Furthermore, 80–84% biodegradation during 150 days under mesophilic home composting conditions was demonstrated by cumulative CO2 evolution. These results indicate promising potential for the developed RHs thermosets as replacements for petroleum-based plastics in e.g. packaging and agricultural applications.

(Invited) A Multifunctional Polynorbonene Binder System Enabling Next-Generation Lithium-Ion Batteries

Polynobornene (PNBE), a material commonly used in your shoes or for the tires of supercars, can also be highly influential to the development of next-generation batteries (Kim et al., 2022). When designing the batteries of tomorrow, we are interested in polymeric materials with precisely defined dynamic mechanical properties, increased ionic or conductivity, specific chemical interactions and moonshots like stable and healable interfaces (Lopez et al., 2019). PNBE provides high chemical and thermal stability, low shrinkage, and strong adhesion properties that lead to enhanced electrode stability and electrical conductivity(Le et al., 2020). Possessing a highly flexible nature allows PNBE to conform to the shape of an electrode – making PNBE an ideal multifunctional binder.Consider some persisting problems associated with batteries, for example Si electrodes typically fail due to cracks in the Si particles creating new surfaces for electrolyte decomposition/solid electrolyte interphase formation, and due to the Si becoming electrically disconnected from the rest of the electrode and ultimately terminating cycling (Ryu et al., 2004) . PNBE can address both aforementioned pain points, low shrinkage and flexibility can help mitigate the impact of cracking that occurs within an electrode over time by maintaining the structural integrity, and strong adhesion properties promote effective binding of the active material and the rest of the electrode. With increasing concerns about cobalt, there has been a move to replace oxides with phosphates. Substituting a substantial fraction of Mn, for Fe in LiFePO4 leads to a material with an energy density approaching that of the oxides, while substantially lessening environmental concerns. Unfortunately, Mn dissolution causes a poor cycle lifetime.In an effort to reduce Mn dissolution, a mixture of PNBE and PVDF was used as a binder system. The PNBE was designed to have ether-type comb-branch functionalities that aid in Mn trapping, while the PVDF had suitable viscosity and mechanical properties. Figure 1 shows cycle lifetime results conducted at 45°C on a 2Ah LMFP-Graphite cell containing a 4%PVDF/1%PNBE binder system. The results show very good lifetime, with the capacity retention nearly 90% after 1,000 cycles. Given the difficulty with cycling of LMFP due to Mn dissolution, these results show good promise for this approach.This talk will highlight the opportunities and challenges of custom and enabling PNBE binder systems for LMFP, and other battery systems. References Kim, N.-Y., Moon, J., Ryou, M.-H., Kim, S.-H., Kim, J.-H., Kim, J.-M., Bang, J., & Lee, S.-Y. (2022). Amphiphilic Bottlebrush Polymeric Binders for High-Mass-Loading Cathodes in Lithium-Ion Batteries. Advanced Energy Materials, 12(1), 2102109. https://doi.org/https://doi.org/10.1002/aenm.202102109Le, D., Samart, C., Lee, J.-T., Nomura, K., Kongparakul, S., & Kiatkamjornwong, S. (2020). Norbornene-Functionalized Plant Oils for Biobased Thermoset Films and Binders of Silicon-Graphite Composite Electrodes. ACS Omega, 5(46), 29678–29687. https://doi.org/10.1021/acsomega.0c02645Lopez, J., Mackanic, D. G., Cui, Y., & Bao, Z. (2019). Designing polymers for advanced battery chemistries. Nature Reviews Materials, 4(5), 312–330. https://doi.org/10.1038/s41578-019-0103-6Ryu, J. H., Kim, J. W., Sung, Y.-E., & Oh, S. M. (2004). Failure Modes of Silicon Powder Negative Electrode in Lithium Secondary Batteries. Electrochemical and Solid-State Letters, 7(10), A306. https://doi.org/10.1149/1.1792242 Figure 1

Ductile, High-Lignin-Content Thermoset Films and Coatings.

In the context of transitioning toward a more sustainable use of natural resources, the application of lignin to substitute commonly utilized petroleum-based plastics can play a key role. Although lignin is highly available at low cost and presents interesting properties, such as antioxidant and UV barrier activities, its application is limited by its low reactivity, which is a consequence of harsh conditions normally used to extract lignin from biomass. In this work, the use of glyoxylic acid lignin (GA lignin), rich in carboxylic acid groups and hence highly reactive toward epoxy cross-linkers, is presented. GA lignin, which is directly extracted from biomass via a one-step aldehyde-assisted fractionation process, allowed the preparation of thermoset films and coatings via a simple reaction with sustainable poly(ethylene glycol) diglycidyl ether and glycerol diglycidyl ether cross-linkers. This allows one to prepare freestanding films containing up to 70 wt % lignin with tunable mechanical properties and covalently surface-attached coatings containing up to 90 wt % lignin with high solvent resistance. Both films and coatings display antioxidant properties and combine excellent UV barrier activity with high visible transparency, which is attractive for applications in sustainable food packaging.

Printable and recyclable carbon nanotube electronics with degradable soybean oil-based polycationic substrate as gate dielectrics

The global concern of electronic waste (e-waste) relevant to the negative impact on the environment and ecological systems have been attracted extensive attention to the imminent solution to the development of sustainable electronic devices. To deal with that, we propose renewable soybean oil to produce thermoset films, serving them as flexible green substrates for the ion-gated transistor (IGT). The effective adjustment of dielectric property and flexibility by controlling the amount of ionic moieties source gifted the thermoset with an excellent sensitivity of 8.75 × 10−3 kPa−1 while the detection limitations up to 20 kPa. Furthermore, the all-carbon-component IGT based on soybean substrate also realized with the best electrical performance of Ion/width of 0.52 μA/mm, and >250 of an on/off ratio and 2.6 μA of on-current at a low voltage operation of VDS = −0.5 V. The soybean oil-based substrate showed fast decomposition in a mildly basic solution, with the graphene electrode recapture efficiency being higher than 95% for the remaking of new transistors. The excellent working performance in both manners of the touch sensor and the field effect transistor accompanied by the highly green fabrication technology clues the high potential in the next-generation electronics that require a significant level of sustainability.

Ultrastrong, Hydrostable, and Degradable Straws Derived from Microplastic-Free Thermoset Films for Sustainable Development.

Single-use plastics such as straws have caused intricate environmental challenges since they are not readily assimilated into nature at the end of life. Paper straws, on the contrary, become soggy and collapse in drinks resulting in an obnoxious user experience. Here, all-natural, biocompatible, degradable straws and thermoset films are engineered by integrating economical natural resources-lignin and citric acid-into edible starch and poly(vinyl alcohol), making them the casting slurry. The slurries were cast on a glass substrate, partially dried, and rolled on a Teflon rod to fabricate the straws. The straws are perfectly adhered at the edges by the strong hydrogen bonds from the crosslinker-citric acid-during drying, thus eliminating the need for adhesives and binders. Further, curing the straws and films in a vacuum oven at 180 °C results in enhanced hydrostability and endows the films with excellent tensile strength, toughness, and ultraviolet radiation shielding. The functionality of the straws and films surpassed paper and plastic straws, making them quintessential candidates for all-natural sustainable development.

Biobased dual-cure thiol-ene benzoxazine resins for high-performance polymer dielectrics

In the present study, two magnolol based main chain benzoxazine polymers (MCBPs) are designed, synthesized and formulated into thiol-ene resins to develop high-performance polymer dielectrics. Initially, the thiol-ene thermoset films, Mag-M-4SH-80 and Mag-E-4SH-80, are obtained respectively using click chemistry. Being post cured via progressive temperature stage, Mag-M/E-4SH-80 performs complete ring opening polymerization and forms dual-cure polybenzoxazine (PBZ) products with excellent thermal and mechanical performances such as a high Tg of 236 °C and a flexure modulus of 2.5 GPa. Moreover, the thiol component of the resin introduces numerous dipoles to the resultant polymer networks, resulting in promising dielectric performances of the resin at both room temperature and elevated temperature. For instance, the Mag-M-4SH-80 film demonstrates a superior energy density (Ue) of 7.0 J/cm3@25 °C, which is among the top reported dielectric thermosets having same efficiency, and Mag-M-4SH-150 film reveals a Ue of 1.1 J/cm3@150 °C, significantly higher than the reported values of a great number of commercial heat resistant polymers. Herein, our findings not only expand the library of high-performance thiol-ene benzoxazine resins but also present their potentials as flexible dielectrics for energy storage for the first time, thus advance the functionality and capability of benzoxazine based materials in modern electronics.

Photocurable extended vanillin-based resin for mechanically and chemically recyclable, self-healable and digital light processing 3D printable thermosets

A vanillin-based photocurable resin was designed for circularity by incorporation of imine functionalities through a Schiff-base reaction between the aldehyde function of vanillin and amino group of ethylene diamine. Sufficient flexibility was provided by a short aliphatic segment introduced by reaction of vanillin with ethylene carbonate, while photocurability was obtained by subsequent methacrylation. The cured thermoset had good solvent resistance, relatively high glass transition temperature (∼75 °C) and good thermal stability with an onset of degradation above 300 °C. Due to the crosslinked structure and imine linkages, the thermoset expressed malleability, self-healing and thermal reprocessability. Furthermore, it could be chemically recycled by immersing in ethylene diamine, which activated transimination. The obtained oligomeric product with amine-terminal groups could be utilized for production of new thermoset films. Tensile testing illustrated similar elastic modulus for mechanically and chemically recycled thermosets, while a slight increase was observed for the self-healed samples, ascribable to a completion of the curing during the post-processing. At the same time elongation and stress at break slightly decreased. Finally, the suitability of the resin for the production of 3D objects by means of digital light processing (DLP) 3D printing was demonstrated.

Acid catalyzedepoxy–methylolphenolthermosets: Astructure–propertystudy

AbstractWe have explored the structure–property relationships of a series epoxy–methylolphenol based thermoset films. Ortho‐, meta‐, and para‐isomers of methylolphenol, that is, ortho‐methylolphenol, meta‐methylolphenol and para‐methylolphenol, respectively, were reacted with the diglycidyl ether of bisphenol A (DGEBA) in the presence of an acid catalyst (CYCAT® XK 406 N). Thermogravimetric analyses showed that irrespective of the methylolphenol structure used, all crosslinked films exhibit 5% weight loss at 343–360°C under nitrogen. The glass transition temperature (Tg) decreases in the order of ortho‐ (Tg = 117°C) > para‐(Tg = 102°C) > meta‐methylolphenol (Tg = 82°C) as measured by differential scanning calorimetry. Uniaxial tensile testing of thin films shows good stress–strain behavior, with ultimate tensile strength values of 75 MPa and 6% strain‐at‐break. Homo‐crosslinking of methylolphenol moieties can occur under the reaction conditions used but in the presence of DGEBA, the methylolphenols prefer to undergo epoxy ring‐opening reactions. This was confirmed by the uniform networks that were formed, that is, no block‐formation was observed. The results of this study confirm that simple methylolphenol hardeners can be used to prepare crosslinked epoxy‐based films with excellent thermomechanical properties.

All‐aromatic ester‐based thermosets: The effect of crosslinking in the nematic or isotropic state

AbstractWe'll report on two series all‐aromatic main‐chain reactive oligomers that can be crosslinked in either the nematic phase or in the isotropic phase. This series is unique in that both model systems have an identical backbone geometry, comprised of hydroquinone with or without a phenyl substituent and phenyl substituted terephthalic acid. Crosslinking the oligomers (Mn of 1–9 kg/mol) via maleimide end‐groups in the nematic or isotropic phase yields networks with similar crosslink densities (Mc) and similar thermal properties. Crosslinked films exhibit high decomposition temperatures (>395°C) and amorphous thermoset films exhibit Tg's in the 141–190°C range whereas nematic thermoset films give Tg's that range from 143 to 176°C, as measured by DMTA. However, the phase type appears to have a major effect on the stress–strain behavior of the films. All films prepared by crosslinking un‐aligned nematic oligomers show poor stress–strain behavior (σ = 20–63 MPa, ε = 0.5%–5.4%), whereas crosslinking the amorphous oligomers results in films with excellent stress–strain properties (σ = 94–97 MPa, ε = 7.1%–13.3%). The superior toughness of the cured amorphous films can be attributed to the larger free volume induced by steric crowding of the phenyl substituents in the polymer repeat unit.

Simultaneously improving the ductility and strength of aromatic thermoset films

Aromatic thermoset materials have shown great potential applications in various fields owing to their excellent mechanical strengths. However, their poor ductility is still hinders their large-scale applications. In this study, a new class of aromatic thermosets consisting of two types of crosslinks was successfully developed by incorporating the special group imidazole into a type of crosslinked thermoset. One crosslink is constituted of reversible multiple noncovalent interactions containing “face-face” π–π stacking, “point-point” hydrogen bonds, and ion-pair electrostatic interactions, whereas the other is composed of permanent covalent bonds. Most importantly, the synergetic interplay among these reversible multiple noncovalent interactions enables them to evade the restrictions from the aromatic polymer skeletons to proceed with their dynamic dissociating-rebuilding processes, which can timely and effectively dissipate the internal stress. Finally, owing to the coefficient of these two types of crosslinks, a significantly enhanced ductility was successfully obtained on these aromatic thermosets and their tensile strengths were also improved. Such thermosets having simultaneously enhanced strengths and ductility are predicted to be eventually used in a wide range of applications.

HYDRAULIC FRACTURING DESIGN IMPROVEMENTS BY PROPPANT FLOWBACK MITIGATION METHOD APPLICATION DURING HYDROCARBON PRODUCTION

Proppant flowback after hydraulic fracturing treatment is quite a serious challenge that causes damage to both downhole and surface equipment, leading to unwanted workovers and production suspension, or other negative outcomes. Some special methods including preventive as well as corrective measures already exist in the industry to overcome the proppant flowback problems. However, there is no clear guidance on how to choose the method for certain conditions, particularly during the hydraulic fracturing design stages. Therefore, the authors conducted a comprehensive review of fourteen preventive technologies to systematize them and to propose an initial decision-making approach. The following methods were considered in this paper: Resin Coated Proppants (RCP), RCP with Activator, RCP with Nanoparticles, Proppant with Liquid Resin Systems (LRS), Proppant with Surface Modification Agents (SMA), Proppant with Proppant Consolidation Aid (PCA), Cylindrical Proppant, Microfibers, Thermoset Resin Fibers, Thermoset Film Strips, Deformable Isometric Particles (DIP), Expandable Proppants, Polymer Surface Modified Proppants, and In-situ Formulated Proppants. The review reveals physical, chemical, and technological properties of each method to select criteria for effective screening. So, the reader could find the appropriate proppant flowback mitigation method corresponding to a particular reservoir and the well conditions during the initial hydraulic fracturing design stages.

Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and Tg values of binarily cured epoxy resins

Diglycidyl ethers of N,N'-bis(5-hydroxy-1-naphthyl)pyromellitimide (BNIDE) and polyethylene glycol (PEGDE) were binarily cured by N,N'-bis(5-amino-1-naphthyl)pyromellitimide (BNIDA) curing agent. Three homogenized mixtures of BNIDE and PEGDE resins with different mole ratios (75/25, 50/50 and 25/75) were isothermally reacted with the stoichiometric amounts of the curing agent. For comparison purposes, each diglycidyl ether was also cured separately with the same condition. The exothermic phase transitions associated with the curing processes were specified in the dynamic differential scanning calorimetry (DSC) traces of BNIDEBNIDA, BNIDE:PEGDEBNIDA, and PEGDEBNIDA mixtures. The completion of the curing processes was confirmed using Fourier transform-infra red (FT-IR) spectra and DSC traces of the isothermally cured resins. Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and Tg value of binarily cured epoxy resins was investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Both thermal stability and Tg value of the imide-epoxy thermoset films significantly increases with BNIDE resin. Instead, when PEGDE resin was cured by BNIDA, the prepared films showed more flexibility and pliability. These important characteristics were appropriately balanced by employing three binary mixtures of BNIDE and PEGDE resins.

Chemically recyclable glycerol-biobased polyether thermosets

Glycerol is a chemical byproduct of biodiesel synthesis that has become an important raw material for use in the food, personal care and pharmaceutical industries. However, even with these applications, there is an imbalance between the growing production of glycerol and the demand for it. In this work we propose the use of glycerol and diglycerol as raw materials for the synthesis of fully recyclable aliphatic polyether thermosets. Fully biobased polyether thermosets are prepared by the acid-catalyzed bulk self-condensation of glycerol and diglycerol with different ratios of 1,6-hexanediol at 170 °C using an acid-base non-eutectic mixture organocatalyst (NEMO). The thermosets are characterized using solid-state 13C NMR, FTIR, DMA and DSC. The mechanical properties of the thermosets can be varied by adjusting the glycerol to diol ratio, leading to rigid or flexible thermoset films with varying Young’s modulus and elongation at break. Finally, we also demonstrate that the glycerol and diglycerol based thermosets can be depolymerized back to the initial monomers by hydrolysis under acidic conditions and subsequently repolymerized to obtain chemically recyclable biobased thermosets.

Norbornene-Functionalized Plant Oils for Biobased Thermoset Films and Binders of Silicon-Graphite Composite Electrodes.

We herein report the functionalization of plant oil with norbornene (NB) and subsequent polymerization to prepare biobased thermoset films and biobased binders for silicon/mesocarbon microbead (MCMB) composite electrodes for use in lithium-ion batteries. A series of NB-functionalized plant oils were prepared as biobased thermoset films via ring-opening metathesis polymerization (ROMP) in the presence of a second-generation Grubbs catalyst with tunable thermomechanical properties. Increasing the catalyst loading and cross-linking agent increased cross-link density, storage modulus (E′), and glass transition temperature (Tg), while the numbers of unreacted or oligomeric components in the films were reduced. High number of NB rings per triglyceride in the plant oil encouraged monomer incorporation to form a polymer network, therefore accounting for the high Tg and E′ values. Furthermore, the NB-functionalized plant oil and 2,5-norbornadiene (NBD) were copolymerized as bioderived binders for silicone/MCMB composite electrodes of lithium-ion batteries via ROMP during electrode preparation. Cell performance investigation showed that the silicone/MCMB composite electrode bearing the NBD-cross-linked NB-functionalized plant oil binder exhibited a higher C-rate and cycle-life performance than that using a conventional poly(vinylidene fluoride) (PVDF) binder. Finally, the electrode based on the bioderived binder exhibited a high specific charge capacity of 620 mA h g–1 at 0.5 C.

Anchored quaternary ammonium salts adsorbed on polyurethane film surfaces

A flexible, thermoset and transparent polyurethane (PUR) film with high glass transition temperature, has been deployed as a substrate for anchoring anti-bacterial molecular layers. These layers are formed by adsorbing, from an aqueous solution, a silyl anchoring quaternary ammonium salt (AQAS) with a long alkyl chain (C18) onto the PUR film surface, followed by thermal curing at 160 °C. The presence of AQAS adsorbed on the PUR film surface is confirmed by the appearance of a distinctive N1 s level XPS peak at 402 eV, attributed to quaternary nitrogen (N+). The carbonyl groups on the PUR surface appear to be the main surface binding sites for the adsorbed AQAS molecules. This interpretation is validated by the relative decrease in the intensities observed for the ν (CO) at 1700 cm−1 in the infrared spectra, and decreases in the intensity of the C1 s binding energy peak for CO at 289 eV in the XPS spectra of the PUR following AQAS adsorption. Leaching studies suggest a chemisorbed first layer and several leachable higher layers of oligomeric forms of AQAS. A PUR surface incorporating a blended polydimethylsiloxane additive exhibits similar adsorptive capacity to pristine PUR. However exposing the PUR films to oxygen plasma treatment prior to AQAS adsorption leads to a higher coverage of the adsorbate on the PUR surface. The anchoring quaternary ammonium salt (AQAS) in this current work has established potencies against a wide range of critical organisms. Antibacterial assays adapted from the JIS 2801 wet fomite method confirm the potency (3-log reduction) of these PUR-AQAS films against Staphylococcus aureus and Escherichia coli.

Degradable Thermoset Fibers from Carbohydrate-Derived Diols via Thiol–Ene Photopolymerization

Carbohydrate-derived monomers were synthesized, and thiol–ene photopolymerization was employed to produce thermoset films and fibers from the biobased dienes isosorbide 10-undecenoate (IU) and glucarodilactone 10-undecenoate (GDLU) and multifunctional thiols. The resulting materials, comprising up to 94% biorenewable content, were flexible and cross-linked and had mechanical and thermal properties that varied with IU and GDLU content (e.g., rubbery plateau storage moduli = 6.1 to 10.5 MPa at 40 °C above the glass transition temperature; glass transition temperatures = −9.9 to 27 °C by differential scanning calorimetry; degradation temperatures = 238 to 347 °C by thermogravimetric analysis). By combining electrospinning with in-situ UV irradiation and carefully controlling the monomer mixture viscoelasticity and orifice-to-collector flight time, we produced uniformly cured fibers directly from the monomer feed when the ene monomers contained either 100% GDLU or 50% GDLU/50% IU. The resulting GDLU-containin...

Moduli development of epoxy adhesives during cure

Quantifying the modulus development during cure of adhesives and prepregs is complex due to the resin's behavior. First, each phase and transition need a careful selection of frequency, strain, and thermal cycles. Second, between the gel point and the degree of cure at which resins are typically demolded, the material has a high compliance, causing excessive noise in data. Third, samples are made using multiple layers, which can cause delamination. Lastly, the data analysis and finding of trends is difficult because most tests are performed at discrete cure values.A testing protocol to detect the moduli changes in one experiment is presented. Adhesive DA 409 was analyzed using the kinetic, viscosity, gel point, and shrinkage information to delimit and select the parameters for the moduli tests. The frequency and strain of each property were selected based on dynamic strain and frequency sweeps. First, the gel point was measured using three methods; the cross-over of storage and loss moduli, the point where the complex viscosity reached industry accepted values, and the intersection of the dissipation factor at multiple frequencies. The gel point was found between 56 and 63% cure. Second, the viscosity was measured in a parallel plate rheometer, under isothermal and non-isothermal cycles, and fitted using the Castro-Macosko model. Third, the linear shrinkage was measured in a DMA in compression using zero strain to eliminate displacement due to compression loads. The total shrinkage was 4.34%, with most of the shrinkage occurring in the liquid viscoelastic region. A linear relationship between shrinkage and cure was observed.Lastly, the modulus was measured in a DMA in a three-point bending test. With this new protocol, the modulus was measured from the gel point up to the fully cured state by sandwiching a partially cured beam between two fully cured plates. The high compliance and noise were mitigated with this sandwich sample. An effective modulus of the three plates was obtained. The modulus of the partially cured beam was extracted using the elastic sandwich beam theory. This method shows potential in the testing of thermoset composites and films.

Soybean Oil-Based Thermoset Films and Fibers with High Biobased Carbon Content via Thiol–Ene Photopolymerization

While a number of vegetable oil derivatives have been integrated with petroleum-based materials to prepare thermosetting polymers, existing examples usually incorporate low total biorenewable content into the final product. With the goal of generating thermosets with high biorenewable content, two different soybean oil derivatives with multifunctional thiol and acrylate groups were photocured via thiol–acrylate photopolymerization. For this purpose, l-cysteine, a nonhazardous amino acid, was coupled with epoxidized soybean oil to synthesize a mercaptanized soybean oil derivative containing multiple thiol groups. After being mixed with acrylate counterparts suitable for performing thiol–ene photopolymerizations, these monomer mixtures were processed into thermoset films (via monomer mixture film casting followed by photopolymerization) and fibers (via simultaneous electrospinning of the monomer mixture and photopolymerization in flight). The resulting materials possessed high biobased carbon content (BCC; ...

High-Temperature Shape Memory Behavior of Semicrystalline Polyamide Thermosets.

We have explored semicrystalline poly(decamethylene terephthalamide) (PA 10T) based thermosets as single-component high-temperature (>200 °C) shape memory polymers (SMPs). The PA 10T thermosets were prepared from reactive thermoplastic precursors. Reactive phenylethynyl (PE) functionalities were either attached at the chain termini or placed as side groups along the polymer main chain. The shape fixation and recovery performance of the thermoset films were investigated using a rheometer in torsion mode. By controlling the Mn of the reactive oligomers, or the PE concentration of the PE side-group functionalized copolyamides, we were able to design dual-shape memory PA 10T thermosets with a broad recovery temperature range of 227–285 °C. The thermosets based on the 1000 g mol–1 reactive PE precursor and the copolyamide with 15 mol % PE side groups show the highest fixation rate (99%) and recovery rate (≥90%). High temperature triple-shape memory behavior can be achieved as well when we use the melt transition (Tm ≥ 200 °C) and the glass transition (Tg = ∼125 °C) as the two switches. The recovery rate of the two recovery steps are highly dependent on the crystallinity of the thermosets and vary within a wide range of 74%–139% and 40–82% for the two steps, respectively. Reversible shape memory events could also be demonstrated when we perform a forward and backward deformation in a triple shape memory cycle. We also studied the angular recovery velocity as a function of temperature, which provides a thermokinematic picture of the shape recovery process and helps to program for desired shape memory behavior.

Synthesis and properties of semi-crystalline poly(decamethylene terephthalamide) thermosets from reactive side-group copolyamides

We have prepared semi-crystalline polyamide (PA) thermosets using reactive side-group functionalized copolyamides as precursors. Reactive meta- and para-based phenylethynyl diacid chlorides (IPE and TPE) were synthesized and incorporated in poly(decamethylene terephthalamide) (PA 10T) using a low temperature solution polymerization method. The phenylethynyl-based comonomers disrupt crystallization of the final copolyamides and lower the onset of melting. Copolyamides containing 5, 10 and 15 mol% of the reactive comonomer could be cured at 350 °C into freestanding PA thermoset films. All thermoset films are stable up to 400 °C, as confirmed by DMTA, which is the result of network formation. The thermosets exhibit both a crystalline phase and a crosslinked amorphous phase. Depending on the concentration of the side-groups, the degree of crystallinity of the final thermosets can be controlled and suppressed by 52–76% compared to the PA 10T reference polymer. Most notable is the fact that the IPE-15 thermoset film exhibits outstanding stress–strain behavior, i.e. elongation at break (∼17%) and toughness (766 MJ·m−3).