Optical properties and artistic color characterization of nanocomposite polyurethane materials

Polymer-Zeolites composites have been prepared, using castor oil based polyurethane (PU) as a host and AlPO4-5 as particulate filler. The prepared PU/zeolite composites have been characterized for mechanical properties such as tensile strength and tensile modulus. These PU composites exhibited an improved mechanical performance compared to the unfilled PU. Thermo gravimetric analyzer (TGA) curve shows that all the chain-extended PUs are stable up to 250 °C and maximum weight loss occurs at 490 °C. The thermal stability of composites increases with increase in zeolite content. Microcrystalline parameters and micro voids of composites have been measured by using wide-angle X-ray scattering (WAXS) and Positron Annihilation Lifetime (PALS) methods respectively. The microcrystalline parameters and micro-voids from PALS indicate the interaction of the filler with the matrix is stronger beyond 5% of the filler which reflect the mechanical performance as well. Surface morphology of composites has been studied using Scanning Electron Microscopy (SEM). The photomicrograph of SEM indicates a uniform distribution of zeolite filler in the PU matrix.

Objective: to compare the remodeling features of polyurethane (PU) and bovine pericardium (BP) patches that have been implanted in a sheep carotid artery for 6 months. Materials and methods. Synthetic matrices were fabricated from a 12% PU solution in chloroform by electrospinning on a Nanon-01A machine (MECC, Japan). Biological matrices made from commercially produced PU (Kem-Periplas Neo, CJSC Neocor, Russia) were used for comparison. The matrices were implanted as vascular patches into sheep carotid arteries (n = 3). Implantation period was 6 months. Via ultrasound scan, the patency of arteries bearing the implanted vascular prostheses was evaluated. After removal, the matrix samples were studied by histological examination, scanning electron microscopy and confocal microscopy. Prior to this, they had been stained with specific fluorescently labeled antibodies. The GraphPad Prism 8 application was used to process statistical data. Results. The sheep carotid artery wall was completely patent, with no aneurysmal dilatations, significant stenoses, and hematomas six months after the PU and BP matrices were implanted. The PU matrix was distinguished by a less pronounced connective-tissue capsule and no neointima hyperplasia; the thickness of the remodeled PU wall was 731.2 (711.5; 751.3) μm. At the same time, there was BP neointimal hyperplasia with a thickness of 627 (538; 817) μm and a remodeled wall thickness of 1723 (1693; 1772) μm. In comparison to BP, the PU matrix exhibited greater endothelialization and structural integrity. Conclusion. An in vivo study on sheep demonstrated the potential of PU matrix, a novel and effective material for vascular reconstruction, to maintain harmonious remodeling, bioinertness and structural integrity when in contact with blood. Due to its excellent elastic qualities and durability, PU is interesting both as a monocomponent and as a component of a composite material that can be used to create products for the needs of cardiovascular surgery.

A self-healing sustainable halloysite nanocomposite polyurethane coating with ultrastrong mechanical properties based on reversible intermolecular interactions

Aiming at an easy-processing shape memory polymer, we report different thermo-responsive shape memory polyurethane (SMPU) nanocomposites derived from Hydroxyl Terminated Poly-Butadiene (HTPB) and the Poly Tetra Methylene Glycol (PTMG) encapsulated with different concentrations of carbon nanofiber (CNF) in a cross-linked shape memory polyurethane (PU) matrix. By introducing the optimum concentration of the nanofiller with the PU matrix, we can improve essential properties of PU composites such as morphology, mechanical flexibility, as well as shape memory properties, which are considered the crucial requirement for the effective design of PU composites for a precise application. Two compositions of PU composites were prepared by encapsulating CNF, viz. PU-0.1CNF and PU-0.5CNF, the content of CNF being 1 wt.% and 5 wt.%, respectively. Morphological, thermal, and mechanical studies of these two PU composites show that CNF is homogeneously blended within the PU matrix and well dispersed. The thermal stability of prepared polymer films was evaluated with the help of Thermo-Gravimetry, indicating increased stability with the addition of CNF nanofillers. DSC analysis helps to determine the glass transition temperature (Tg ) as well as the shape transition temperature (Ttrans ). The tensile study confirmed that PU-0.5CNF possesses a greater Young’s modulus value and is not constant in elastic loads. The anti-corrosion property of the prepared SMPU nanocomposite coatings coated over the SS plate was evaluated using a 3.0 wt% NaCl (simulated seawater) solution. Extrapolation of Tafel plots and electrochemical impedance spectroscopy (EIS) provided a higher value of positive corrosion potential (Ecorr ) and a lower value of corrosion current (Icorr ). The electrochemical experiment results demonstrated that PU-0.1CNF nanocomposite coating on SS has better anti-corrosive properties and protection efficiency (PEF% = 98.43%) and behaves like a physical barrier to resist corrosion. These HTPB/PTMG PU nanocomposites exhibit excellent shape memory properties and have a unique composition having both the properties of anti-corrosion and shape memory effects. The results show that by properly selecting the composition we can tailor-make a PU having both anticorrosion and shape memory properties.

Polyurethane (PU) is a popular material for nanocomposites application in polymer science and technology. In pure form, PU is not suitable for engineering applications that require additional processing to improve the mechanical and thermal properties. High-performance PU nanocomposites with superior properties may be obtained by reinforcement with nanostructures such as graphene (Gr) and hexagonal boron nitride nanosheets (h-BNNS). In the present research, h-BNNS and Gr are used as a reinforcement into the PU matrix. Solvent casting method has been used to obtain PU/Gr, PU/h-BNNS, and PU/Gr + h-BNNS (hybrid) nanocomposites. Gr and h-BNNS are reinforced into the PU matrix at weight % (wt.%) of 0.3, 0.5, and 0.7, respectively. In hybrid PU nanocomposite the combination of both Gr and h-BNNS has been used in the wt.% of 0.3, 0.5, and 0.7. Characterization techniques such as Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and dynamic mechanical analysis (DMA) were employed to elucidate the morphological and structural changes within the PU nanocomposite matrix. Results revealed the establishment of polymerization in all three types of reinforcement and the presence of hard segments in the h-BNNS reinforced PU nanocomposites, which indicates the presence of hydrogen bonding. h-BNNS reinforced PU nanocomposites revealed the formation of strong interfacial interaction between the h-BNNS and the PU matrix. Significant changes in the storage modulus (E') were observed with the various types of reinforcing agents. Reinforcement of 0.5 wt.% of h-BNNS yields better results compared to Gr and hybrid reinforcement.

Studies on Inter and Intra Molecular Hydrogen Bonding and Morphologies of Single-walled Carbon Nanotubes/polyurethane-amide

Chapter 2 - Micro- and Nanomechanics of PU Polymer-Based Composites and Nanocomposites

Preparation of flexible and elastic thermal conductive nanocomposites via ultrasonic-assisted forced infiltration

Polyurethane (PU) composites with various porosities and spherical pore structures were prepared using thermally expanded hollow thermoplastic microspheres. Thermal and mechanical properties of PU composites were mostly governed by the amount of porosity. The measured thermal conductivity of PU composites was estimated using theoretical models, proving the formation of spherical pore structures (e ≈ 1) in PU matrix and serving as an internal porous material (EMT model < k < parallel model).

Developing green composite with high biomass content is one crucial way to realize the strategy of ‘carbon reduction’. The type of polyurethane prepolymer and its soft segment’s structure have an important influence on the structure and properties of composite materials. This work focused on preparing different kinds of wood powder-polyurethane prepolymer (WCLPU) composite with high biomass content to study the effects of the molecular weight of the soft segment of the polyurethane prepolymer (PCLPU) on the structure and properties of the composites. The results showed that the composite materials with 70 wt% wood content exhibited high strength and good bending performance. Specifically, with decreasing molecular weight of the PCLPU soft segment, the bending strength and bending modulus of the modified WCLPU composite also increased. This work has laid a foundation for studying the effects of the molecular weight of the PCLPU soft segment on the structure and properties of composite materials.

Polyurethane nanocomposite based gas barrier films, membranes and coatings: A review on synthesis, characterization and potential applications

Fluidized bed combustion fly ash as filler in composite polyurethane materials

A series of castor oil‐based polyurethane (PU) with and without the incorporation of Halloysite nanoclay as filler are synthesized via addition polymerization of polycaprolactone‐diol (PCL) and methylene diphenyl diisocyante (MDI) as monomers. The PUs are characterized by using attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), thermogravimetric anaysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), and pencil hardness test. The TGA thermogram showed that the incorporation of castor oil affected the thermal stability of the PU matrices by 7–9% in reduction of the decomposition temperature; whereas the incorporation of Halloysite nanoclay into the PU matrices increased the thermal stability by 3–5% in the detection of higher decomposition temperature. The DSC thermograms of the castor‐oil based PU and castor oil‐based PU with Halloysite nanoclay showed reduction in glass transition temperature (Tg) by 13–33 and 8–14 °C, respectively as compared to pristine PU and castor‐oil based PU. It is envisaged that the reduction in Tg is caused by the non‐uniformity of dispersion of the Halloysite nanoclay throughout the PU matrices and hence, affected the mobility of the PU chains. The SEM images further confirmed the non‐uniformity of dispersion of the Halloysite nanoclay in the PU films. Pencil hardness test indicated that the PU films coated on glass slides had lower than 1H hardness.

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.

The current work investigates the effect of the addition of graphene nanoplatelets (GNPs) and graphene oxide (GO) to high hard-segment polyurethane (75% HS) on its thermal, morphological, and mechanical properties. Polyurethane (PU) and its nanocomposites were prepared with different ratios of GNP and GO (0.25, 0.5, and 0.75 wt.%). A thermal stability analysis demonstrated an enhancement in the thermal stability of PU with GNP and GO incorporated compared to pure PU. Differential Scanning Calorimetry (DSC) showed that both GNP and GO act as heterogeneous nucleation agents within a PU matrix, leading to an increase in the crystallinity of PU. The uniform dispersion and distribution of GNP and GO flakes in the PU matrix were confirmed by SEM and TEM. In terms of the mechanical properties of the PU nanocomposites, it was found that the interaction between PU and GO was better than that of GNP due to the functional groups on the GO’s surface. This leads to a significant increase in tensile strength for 0.5 wt.% GNP and GO compared with pure PU. This can be attributed to interfacial interaction between the GO and PU chains, resulting in an improvement in stress transferring from the matrix to the filler and vice versa. This work sheds light on the understanding of the interactions between graphene-based fillers and their influence on the mechanical properties of PU nanocomposites.