Polyurethane polystyrene based smart interpenetrating network with quick shape recovery through thermal actuation

Nano/microsized organic fillers play an important role in developing new types of polyurethane (PU) composites. In this study, microsized hollow poly(styrene-alt-maleic anhydride) (PSMA) microsphere was grafted with polytetramethylene glycol (PTMG) or 4-butanediol (BDO) and subsequently incorporated into a PU matrix to fabricate composites. For comparison, composites containing pristine hollow PSMA microsphere and neat PU were also prepared. The mechanical properties, damping properties, thermal stability, crystalline structure and water uptake of the composites and neat PU were investigated. The results show that the incorporation of surface-grafted hollow PSMA microspheres could effectively improve the mechanical and damping properties of PU, increasing tensile strength to 18.7 MPa, raising the tanδ peak to 1.05 and broadening the effective damping range (tanδ > 0.3) to 39.1–40.4 °C. Both PU composites and neat PU exhibited three-step decomposition regions. In the first decomposition region, the thermal stability of PU composites was improved slightly except that it was filled with BDO-graft-PSMA microspheres. But in the second and third decomposition regions, all PU composites showed lower thermal stability than neat PU. The introduction of hollow PSMA microspheres also reduced the crystallinity of the PU matrix, which is attributed to the large diameter of the microspheres disrupting crystalline order.

In the present study, polyurethane (PU) was prepared using a pre‐polymer (two‐shot) process with a novel phloroglucinol chain extender. PU nanocomposite was prepared by incorporating acid‐FMWCNTs in pristine‐PU. Polystyrene (PS) was functionalized with the nitro group through our previously reported method. The ternary blend composites (PU/PS‐NO2/FMWNTs) were prepared using acid functionalized multiwall carbon nanotubes (FMWCNTs) for enhanced properties and selectivity. Nitro‐functionalized‐PS/PU composite properties were compared with pristine‐PU and its blend composite. The structure of the pre‐designed PU polymer and its composites were confirmed by the FTIR and the degree of crystallinity and amorphous state was determined with XRD analysis. Excellent thermal stabilities were confirmed through a TGA thermogram with an increase in the loading amount of FMWCNTs. Excellent tensile strength 59.2 ± 2.6 MPa with 0.1 g loading amount of FMWCNTs with enhanced flexibilities was achieved. The significant change in surface morphologies and porosity suggested enhanced interaction (physical and chain entanglement) of FMWCNTs and nitrated‐PS with PU chain as the loading amount of filler increased. The resulted porous spongy cluster (as seen in SEM images) provides efficient shape recovery strain with excellent flexibility to the composite material without compromising repeatability. Almost 100% shape recovery was observed for all samples with repeated recoveries. The recovery time of PU nanocomposite observed is shorter than neat polyurethane and PU/PS‐NO2 blends because of their better conductive nature but causes brittleness, which can easily initiate a crack in the sample compared to a blended sample.

Ultrasonic vibration (UV)-induced shape memory polyurethane (PU) and composite containing 1 phr (part per hundred) graphene nanoplatelets (GNPs) were prepared through ex situ polymerization by using microcompounder. Atomic force microscopy and field emission scanning electron microscopy were used for the characterization of surface morphology, surface roughness, and graphene nanoplatelets dispersion in the polyurethane matrix. The thermomechanical properties (storage modulus, loss modulus, energy dissipation factor, and glass transition temperature) were determined by using the dynamic mechanical analyzer. The thermomechanical properties, shape memory stretch and recovery strength, shape fixity, tensile strength, and UV-induced shape recovery are enhancing for a composite having 1 GPU (1 phr GNPs in PU matrix). Shape memory and mechanical properties were improved for composite sample as compared to pure polyurethane. 1 GPU composite sample shows ultrasonic vibration-induced shape recovery, whereas pure polyurethane sample has no shape recovery. The UV-induced shape recovery strongly depends on the dispersion of GNPs and frequency of ultrasonic vibration. For composite sample (1 GPU), embedded GNPs in the PU matrix may absorb the UV frequency and converted into heat energy (lattice vibration of GNPs and heat is transfer through conduction) which is responsible for shape recovery. With increase in the frequency of UV, the shape recovery also increases for the composite. Glass transition temperature (Tg) was influenced with the addition of GNPs into neat polyurethane matrix. UV-induced shape recovery test was carried out in an ultrasonic vibration transducer with variable frequency (0–40 kHz).

In this study, three types of amine-functionalized graphene oxide (f-GO) have been synthesized and their polyurethane (PU) composites have been fabricated. Mechanical properties and the anticorrosion performance of as-prepared composites were thoroughly investigated. The amine groups (two aliphatic groups and one aromatic group) on GO influenced the dispersion of the fillers and the properties of the composites. Among the f-GO series, GO functionalized with 2-naphthyl amine (2NA-GO) indicated higher mechanical properties and corrosion resistance than other PU composites. Specifically, the incorporation of 0.5 wt % of 2NA-GO in the PU matrix showed a 2.2 times higher tensile modulus than the neat PU and the highest protection efficiency of 99.94%. This synergetic effect of 2NA-GO was due to the aromatic structure and relatively low molecular weight of 2NA. The aromatic structure developed π–π interfacial interactions between the amine group and phenyl groups of the hard segments in the PU backbone. Furthermore, the lower molecular weight contributed to the uniform dispersion of the filler. Based on the results, molecular structure and molecular weight could be a critical factor in designing the f-GO to improve the mechanical and corrosion properties of PU composites. Additionally, this fact can be contributed to PU industries, which require a high anticorrosion performance as well as enhanced mechanical properties.

Polyurethanes (PUs) are one of the most widely used polymers in research and industry. They can be synthesized from chemical sources and natural sources. PUs are a very useful class of polymers and exhibit many desirable properties that can be exploited in various applications. PUs are formed by the reaction between polyols and isocyanates. A wide variety of polyols and isocyanates are available for synthesis, and hence we can produce a large number of PUs. PUs show high mechanical strength, chemical resistance, flexibility, and resilience. One of the major advantages of some specially designed PUs is their ability to recover their primary shape, which is known as shape memory. The shape-memory effect (SME) of PUs makes them popular in biomedical, electronic, and thermal applications. The SME can be monitored using different measures such as shape fixity, recovery time, and recovery rate. Various stimuli are applied to shape-memory materials to induce shape memory. PU polymers can be modified with different nanofillers, and these fillers influence the shape-recovery parameters. PU composites are popular because of a good property–price relationship. This chapter discusses the various factors affecting the SME of PU composites and the effect of different types of fillers on the PU matrix.

Us 4,996,286 latent curing agent for epoxy resins

Smart polyurethane composites for 3D or 4D printing: General-purpose use, sustainability and shape memory effect

The temperature dependence of the dynamic viscoelastic behavior of interpenetrating networks (IPN) of polyurethane (PU) prepared from poly(oxypropylenediol) (POP) and toluylene diisocyanate (TDI), and of polyurethane diacrylate (PUA) prepared from POP and TDI by reacting isocyanate groups of the prepolymer with 2-hydroxyethyl acrylate, was measured in the main transition region. The photoelastic behavior of IPN swollen in dimethylformamide (DMF) and methyl ethyl ketone (MEK) was examined in the rubbery region. The temperature dependences of the dynamic Young modulus E* of IPN in the concentration range of PUA ≥ 50 vol.% indicate a pronounced two-phase behavior. The effect of the composition of IPN on the temperature dependence of the modulus E* was quantitatively described by Takayanagi's two-phase model with the conclusion that the PU network is the continuous phase of IPN at ≤ 90% PUA. While in the range of high concentrations of PUA (≥50%) the contributions of phases to E* are additive within the whole range of temperatures, the thermomechanical behavior at low PUA concentrations (≤40%) is more complex. This finding is interpreted by the existence of an interfacial layer which leads to the loss of the distinct two-phase character of IPN. The higher number of elastically active network chains (EANC) of the PUA network compared with the PU network corresponds to different molecular weights of POP used in the preparation of both components. The nonadditive dependence both of the concentration of EANC and of the stress-optical coefficient on composition confirms the heterogeneous character of the IPN structure.

Experimental investigations to enhance the tribological behaviour of biodegradable oil by using manganese doped ZnO/FMWCNTs nanomaterials as lubricant additive

Bone tissue engineering (BTE) aims to regenerate the damaged or diseased bone by combining cells, growth factors, and biomaterials. Synthetic bone tissue, which is widely available, is a promising alternative to autografts, allografts, and natural fillers. Biomaterials like 3D scaffolds mimic the extracellular matrix, supporting cell growth and tissue regeneration. However, clinical applications face challenges such as limited osteogenic and angiogenic capabilities, weak mechanical strength, and risks of infection and immune reactions. The current work introduces a mechanically robust cryogel-hydrogel hybrid scaffold, loaded with extracellular vesicles (EVs) and cell secretomes as osteoinductive cues. The scaffold’s mechanical strength was assessed against its individual components. Its physical characteristics, including swelling capacity and porous structure, were analyzed using field emission scanning electron microscopy (FESEM), and the incorporation of nano-hydroxyapatite (nHAp) was confirmed through Fourier transform infrared (FTIR) spectroscopy. Three scaffolds were tested: a cryogel scaffold of gelatin and nano-hydroxyapatite (nHAp), a hydrogel scaffold of poly(ethylene glycol) diacrylate (PEGDA), and a hybrid cryogel scaffold of gelatin and nano-hydroxyapatite with a PEGDA interpenetrating network (IPN). The results indicated that the hybrid cryogel scaffold with IPN had the greatest normalized ALP content and lowest cytotoxicity, making it the best choice for further study. To explore the osteoinductive potential of Mesenchymal Stem Cell-derived EVs, three scaffold variations were tested: a hybrid IPN scaffold, IPN + nHAp scaffold, and IPN + nHAp + EVs scaffold. These were evaluated for viable cell count, ALP activity, DNA content, and calcium accumulation. The IPN + nHAp + EVs scaffold demonstrated the greatest potential for BTE, with the highest mechanical strength—20.82-fold greater than the single-network cryogel and 1.75-fold stronger than the PEGDA hydrogel. It also showed the highest normalized ALP content, 3.39-fold and 1.47-fold greater than the IPN and IPN + nHAp scaffolds, respectively, and the highest calcium deposition, 1.30-fold higher than the IPN + nHAp scaffold. In conclusion, this study successfully developed a hybrid scaffold system with improved mechanical characteristics and osteogenesis potential, advancing the field of bone tissue engineering.

A two-step approach was used to synthesize a thermo-responsive polyurethane and its blends with amino-functionalized-polystyrene (PS) and multiwall carbon nanotubes (MWCNTs) aiming at enhanced mechanical, thermal and shape memory properties. The synthesis of novel shape-memory polyurethane was confirmed by FTIR spectroscopy. SEM analysis of samples revealed excellent interfacial interaction due to chemical and physical interlinking between both polymers (PU synthesized and polystyrene functionalized) and functionalized multiwall carbon nanotubes (FMWCNTs) filler. The significant improvement in mechanical and thermal properties was observed for synthesized blends (PU/modified PS) as the filler content increased. The mechanical properties of PU/modified-PS blend having 3% loading amount of FMWCNTs were enhanced from 28.6 to 59.3 MPa as compared to those of neat PU. Due to proper fabrication and strong interfacial interaction, enhancement in thermal properties was also evident from the results with increasing filler loading amount. A sharp decrease in thermal, mechanical and recovery properties was also evident due to agglomerates net-points formation when loading amount of carbon filler increased from a certain level. Almost 100% shape recoveries were achieved for all samples, but the recovery durations of the samples were different. Modified-PS and FMWCNTs with PU formed three-dimensional interlocked networks which provided excellent mechanical strength, thermal stabilities and efficient shape recovery to the synthesized blends. Shape recovery response time of blends and nanocomposite was also found to decrease almost half of that of the pristine PU (less than 37 s for blends). Enhanced thermal stabilities, tensile properties, smaller shape recovery time, almost 100% shape recovery capabilities and sustainability, all factors favor the potential use of these blended composite materials in robotics, aeronautics, medical devices and high-performance materials in auto-industry.

The preparation of cation-functionalized multi-wall carbon nanotube/sulfonated polyurethane composites

This paper investigates the impact of halloysite nanotube (HNT) content on mechanical and shape memory properties of additively manufactured polyurethane (PU)/HNT nanocomposites. The inclusion of 8 wt% HNTs increases their tensile strength by 30.4% when compared with that of virgin PU at 44.75 MPa. Furthermore, consistently significant increases in tensile modulus, compressive strength and modulus, as well as specific energy absorption are also manifested by 47.2%, 34.0%, 125% and 72.7% relative to neat PU at 2.29 GPa, 3.88 MPa, 0.28 GPa and 0.44 kJ/kg respectively. However, increasing HNT content reduces lateral strain due to the restricted mobility of polymeric chains, leading to a decrease in negative Poisson’s ratio (NPR). As such, shape recovery ratio and time of PU/HNT nanocomposites are reduced by 9 and 45% with the inclusion of 10 wt% HNTs despite an increasing shape fixity ratio up to 12% relative to those of neat PU.

Novel bio-based electrode polyurethane (PU) fabricated using various conducting materials such as graphene oxide (GO), gold (Au), and carbon nanotube (CNT) as the primary source of a charge carrier. Initially, PU/GO, PU/Au, and PU/CNT polymers were synthesized using a pre-polymerization approach. Therefore, the application of conductive materials modifies and increases the conductivity of PU. The connection between PU and the conductive materials (GO, Au, and CNT) was identified using Fourier transform infrared (FTIR), whereby some important functional groups obtained in this spectrum investigation, such as the presence of amide (-NH) and carbonyl urethane(-C = O), following the absence of diisocyanate groups (-NCO) revealed the synthesis was satisfactory. The glass transition temperatures (Tg) of PU/GO, PU/Au, and PU/CNT were analyzed using differential scanning calorimetry (DSC). In contrast, the mass loss during the heat treatment was observed using thermogravimetric analysis (TGA). Furthermore, thermal studies have proven that PU/GO has higher thermal stability compared to PU/Au and PU/CNT. The field emission scanning electron microscopy (FESEM) presents satisfactory results between PU composites and pure PU. The conductivity of PU and PU composites was examined using electrochemical impedance spectroscopy (EIS) and showed that PU/GO has a better electrical conductivity (σ) at 3.68 × 10−3 S cm−1.

The development of two novel elastomeric erosion resistant coatings for the protection of wind turbine blades is presented. The coatings are prepared by modifying polyurethane (PU) with (i) hydroxyl functionalised graphene nanoparticles (f-GNP) and (ii) f-GNP and a hydrophobic silica-based sol–gel (SG). Tensile, monotonic and cyclic compression and tearing tests have been conducted on the neat PU and the two newly developed elastomeric PU nanocomposites (PU + GNP and PU + GNP + SG) to allow their properties to be compared. The test results showed that the mechanical properties of PU and the modified PUs have strong dependency on temperature, strain rate and nanoparticles loading and addition of GNP and SG to PU improved the mechanical properties. Compared to PU, Young’s modulus and modulus of toughness of PU + GNP + SG increased 95% and 124%, respectively. The PU + GNP nanocomposite displayed the highest tearing strength and the PU + GNP + SG nanocomposite showed the highest elongation at break. An investigation of the microstructures of the modified PUs by FTIR, field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX) are discussed. Hydrophobicity of the PU and developed PU nanocomposites are reported by measuring their water droplet contact angles and their free surface energies.