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.

The remarkable structural features of organic modified montmorillonite particles (OMMT) enable them to complete their important role in enhancing different properties of polyurethane copolymer with 75 wt.% hard segments (PUC/75). Based on the melt intercalation approach, various amounts of OMMT were incorporated into PUC/75 solution followed by the injection moulding process. It is essential to mention that the synthesized PUC/75 in this work relied on using 1,5-Pentanediol as a chain extender in order to produce a long-term and thermal-stable PUC successfully. The effect of incorporating various loading of OMMT on rheological properties of neat PUC/75 and its nanocomposites was investigated. The structure of PUC/OMMT was studied using X-ray diffraction (XRD) and scanning electron microscopy. Additionally, differential scanning calorimetry (DSC) thermograms were utilized to investigate OMMT effect on the thermal transitions and crystallinity of resultant PUC nanocomposites. Interestingly, the dynamic rheological analysis exhibited a remarkable increase in melt rheology behaviour with increasing OMMT loading compared to neat PUC/75. This could imply a good interaction between the functional group on the surface of OMMT and PUC/75 domains; particularly hard domains, herein the DSC results showed moderate improvement in melt temperature (Tm) of PUC/OMMT nanocomposite. However, a decline in crystalline temperature (Tc) was also seen due to aggregation of OMMT, especially at higher OMMT loading. While XRD results exhibited a slight shifting in crystalline peaks of PUC nanocomposites relative to neat PUC/75.

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Purpose: This work aims to study the effect of hard segments (HS) content on the thermal, morphological and mechanical properties of polyurethane polymers based on 1.5 pentanediol chain extenders. Design/methodology/approach: Two comparable series of polyurethanes were synthesised including homo-polyurethane (Homo-PU) and copolyurethane (Co-PU). The Homo-PU consists of 100% wt. of hard segments (HS). The Co-PU composes of 30%wt. of soft segments (SS) using a poly(ethylene glycol)-block-poly(propylene glycol)-blockpoly( ethylene glycol) material. The effect of hard segments content on the morphology of Homo-PU and Co-PU was also studied. Findings: The Homo-PU and Co-PU materials show three distinct degradation steps with the higher thermal stability of the Co-PU compared to the Homo-PU. Enthalpy of fusion (ΔHM) and heat capacity (ΔCP) of polyurethane (PU) samples decrease with decreasing HS content. In the cooling cycle, the higher exothermic peak of crystallization is observed in the Co-PU. In contrast, the cold crystalline peak is observed in the 2nd heating cycle of the Homo-PU. Melting temperature (TM) increases with increasing SS content. Glass transition temperature (Tg) of PU samples shifts to higher temperature with increasing HS content. Storage modulus (E’) of the Co-PU is higher than E’ of the Homo-PU. All N-H groups in PU samples are hydrogen-bonded, whilst most of the C=O groups are hydrogen-bonded. The degree of hydrogen bonding in PU samples decreases with decreasing HS content. The Homo-PU shows better hardness than the Co-PU and higher brittleness at low temperature. WAXS results of the Homo-PU display better crystallinity compared to the Co-PU. Research limitations/implications: The main challenge in this work was how to synthesis Thermoplastic polyurethanes (TPUs) with specific properties to compete other common polymer such as Polyamides (PA) and Polypropylene (PP).Practical implications: Thermoplastic polyurethanes (TPUs) can be used in various application such as backageing, foot,automobiles and constructions. Originality/value: A new type of TPUs that synthesized using different type of chain extender (1.5 pentanediol). Two different types of TPUs were synthesized one contained 30% SS and 70% HS and a second one contained 100% HS.

In this work, the effects of thermoplastic polyurethane (TPU) chemistry and concentration on the cellular structure of nanocellular polymers based on poly(methyl-methacrylate) (PMMA) are presented. Three grades of TPU with different fractions of hard segments (HS) (60%, 70%, and 80%) have been synthesized by the prepolymer method. Nanocellular polymers based on PMMA have been produced by gas dissolution foaming using TPU as a nucleating agent in different contents (0.5 wt%, 2 wt%, and 5 wt%). TPU characterization shows that as the content of HS increases, the density, hardness, and molecular weight of the TPU are higher. PMMA/TPU cellular materials show a gradient cell size distribution from the edge of the sample towards the nanocellular core. In the core region, the addition of TPU has a strong nucleating effect in PMMA. Core structure depends on the HS content and the TPU content. As the HS or TPU content increases, the cell nucleation density increases, and the cell size is reduced. Then, the use of TPUs with different characteristics allows controlling the cellular structure. Nanocellular polymers have been obtained with a core relative density between 0.15 and 0.20 and cell sizes between 220 and 640 nm.

A series of thermoplastic polyurethanes (TPUs) with different amounts of hard segments (HS) (40, 50 and 60 wt.%) are synthesized by a pre-polymer method. These synthesized TPUs are characterized by Shore hardness, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and rheology. Then, these materials are foamed by a one-step gas dissolution foaming process and the processing window that allows producing homogeneous foams is analyzed. The effect of foaming temperature from 140 to 180 °C on the cellular structure and on density is evaluated, fixing a saturation pressure of 20 MPa and a saturation time of 1 h. Among the TPUs studied, only that with 50 wt.% HS allows obtaining a stable foam, whose better features are reached after foaming at 170 °C. Finally, the foaming of TPU with 50 wt.% HS is optimized by varying the saturation pressure from 10 to 25 MPa at 170 °C. The optimum saturation and foaming conditions are 25 MPa and 170 °C for 1 h, which gives foams with the lowest relative density of 0.74, the smallest average cell size of 4 μm, and the higher cell nucleation density of 8.0 × 109 nuclei/cm3. As a final conclusion of this investigation, the TPU with 50 wt.% HS is the only one that can be foamed under the saturation and foaming conditions used in this study. TPU foams containing 50 wt.% HS with a cell size below 15 microns and porosity of 1.4–18.6% can be obtained using foaming temperatures from 140 to 180 °C, saturation pressure of 20 MPa, and saturation time of 1 h. Varying the saturation pressure from 10 to 25 MPa and fixing the foaming temperature of 170 °C and saturation pressure of 1 h results in TPU foams with a cell size of below 37 microns and porosity of 1.7–21.2%.

This study focuses on a new fabrication of nanocomposite based on Polyurethane Copolymer (PUC) intercalated with organo-modified montmorillonite nanoparticles (OMMT), via an efficient combination of solution mixing and melt blending processes. The combination of solution mixing and melt interaction processes produced PUC/OMMT nanocomposites with enhanced properties. The OMMT filled PUC was characterised by TEM and tensile test. The effect of thermal treatment process was also studied due to subsequent microphase separation of PUC resulting from microdomain miscibility. TEM observation recognised a decent dispersion state of OMMT within PUC, owing to their exfoliated and intercalated structure. This morphology was greatly influenced by induced thermal treatment. The dynamic mechanical thermal analysis (DMTA) revealed that storage modulus and glass transition temperature of the nanocomposites increased with OMMT incorporation. The tensile modulus and tensile strength of nanocomposites showed an improvement with the addition of OMMT.