Papers by Keyword: Polyurethane

Abstract: The escalating global demand for energy efficient infrastructure has intensified interest in Phase Change Materials (PCMs) for thermal regulation in buildings. PCMs, owing to their high latent heat storage capacity, can significantly reduce operational energy demands when integrated into construction materials. However, for structural applications, the mechanical integrity of concrete remains paramount, requiring careful evaluation of how PCM incorporation affects its strength characteristics over time. In concrete technology, the introduction of secondary functional materials often alters the internal microstructure, influencing both load bearing capacity and durability. For PCMs, this balance between thermal enhancement and mechanical performance remains a pertinent research frontier in sustainable construction. However, in recent past, focus of the research in construction sector has not brought this aspect to the limelight for practical integration of these materials into concrete especially in Pakistan. Therefore, this study has attempted to instroduce this technology in construction sector of Pakistan by investigating the influence of two distinct microencapsulation shell materials, Melamine Formaldehyde (MF) and Polyurethane (PU), on the compressive strength of PCM modified concrete. Fine aggregates were partially substituted with microencapsulated n-octadecane paraffin PCMs by mass to observe performance trends. Experimental results demonstrated a consistent and progressive reduction in compressive strength with increasing PCM content, with MFPCM mixtures exhibiting comparatively lower strength loss than PUPCM mixtures throughout the curing period. The observed deviations ranged from 7.73% at the lowest replacement level to a maximum of 24% at the highest level, emphasizing the decisive role of shell material stiffness and composition in preserving structural performance while enabling thermal benefits. Through these results, this research has paved a way for construction sector in Pakistan to incorporate the PCM technology in concrete by conducting more research on PCM properties.

Abstract: This study presents the synthesis of polyurethane (PU) films using recycled polyethylene terephthalate (rPET) as a sustainable substrate. The rPET was depolymerized through the glycolysis reaction to produce a polyol, which was then reacted with polymeric methylene diphenyl diisocyanate (PMDI) via solution polymerization to form Polyurethane Film. The effect of varying NCO/OH molar ratios (1.00, 1.25, and 1.50) on the properties of the resulting films was investigated, with a focus on enhancing mechanical performance. The PU films were characterized by their physical appearance, FT-IR spectroscopy, and mechanical properties. At the NCO/OH ratio of 1.00, the PU remained in the form of sticky substance like glue and was unable to form into a solid film. However, increasing the ratio to 1.25 and 1.50 resulted in continuous, flexible films with significantly improved mechanical strength. FT-IR analysis confirmed the formation of urethane linkages, as evidenced by a clear reduction in –OH and –NCO functional groups after the film forming. The best performance was observed at an NCO/OH ratio of 1.50, yielding a PU film with a Young’s modulus of 0.528 N/mm², tensile strength of 1.289 N/mm², and elongation at break of 496.587%. These results highlight the importance of the NCO/OH ratio in tailoring films with suitable properties and support the potential of rPET-based PU as a sustainable material for advanced applications.

Abstract: This research aims to study the properties of polishing pads made from polyurethane mixed with rice husk fiber for use in chemical mechanical polishing (CMP) of sapphire. After cleaning and sizing, the rice husk fiber was modified using hydrochloric acid (HCl). Then, both unmodified and modified rice husk fibers were mixed with polyurethane at ratios of 7.5, 10, and 12.5 phr to form polishing pads. The hardness and polishing performance of these pads in sapphire CMP were then tested. The experimental results showed that polishing pads from rice husk fiber could be successfully formed and remained stable. The natural fibers were evenly distributed across the contact surface of the pads. The hardness of polishing pads from rice husk fiber was smaller than conventional polishing pad (SUBA800) in range of 40.5–47.5%. Polishing results revealed that pads made from polyurethane mixed with unmodified and modified rice husk fiber achieved the highest material removal rates (MRR) of 94.2% and 64.7%, respectively, compared to the conventional pad. These results indicate that both types of fibers able to be used as a material for manufacturing polishing pads for adding value and reducing the waste from the agricultural.

Abstract: The article investigates the influence of ultraviolet (UV) on polyurethane foams' structural and mechanical characteristics. To assess the impact of changes and degradation of foam properties, studies were conducted for two groups of samples: those without exposure to UV and those exposed to natural UV for 3 months. According to the analysis of IR spectra, insignificant chemical changes in the structure of the outer surface of the samples were established as a result of three months of UV influence on the foam. No noticeable chemical changes were found in the inner part of such samples. Compression tests of samples of different groups were carried out under static loading to study the change in mechanical characteristics. Based on experimental tests, changes in the values of mechanical, strength, and deformation characteristics were investigated: Young's modulus, elastic strength, yield strength, and degree of deformation recovery. A conclusion was made about the resistance of polyurethane foam to ultraviolet influence for a period of up to three months.

Abstract: Good Handling Practices (GPH) for fish will have an impact on the quality of fish catches. Therefore the addition of material as a good insulator in the hatch of a fishing vessel is needed. Polyurethane as an insulator material can be used as one of the additional materials in the hatch of a fishing vessel. This study aimed to compare the thermal conductivity properties of the composition and thickness of polyurethane. The results will find out how the influence of composition and thickness of polyurethane affect the insulation of the fishing vessel hatch. The ideal polyurethane insulation should have a material density ρ ≥ 30kg/m³. Density values from testing variations in polyurethane composition show density values in the range of 40kg/m³-100kg/m³, this outcome meets the criteria for a high-quality polyurethane insulating material.

Abstract: Strain sensors for wearable electronics function by identifying mechanical deformations and translating into electrical signals. For optimal performance, electrical conductivity, electrical sensitivity, and flexibility are major properties of strain sensors. Polyurethane (PU) shows promise for custom strain sensors due to its high flexibility. Additionally, using digital light processing (DLP) 3D printing to shape PU is suitable for detecting body movements. Therefore, the aim of this study is developing 3D-printed PU to strain sensing devices, utilizing the surface coating method on 3D-printed PU with carbon black (CB) and polydimethylsiloxane (PDMS) to fabricate the (PDMS+CB)/CB/PU strain sensor. The conductive network of CB enhances sensitivity, while PDMS is incorporated to act as an adhesive for the durability of CB on the PU surface. The results of the experiment reveal a gauge factor of 6.04 with range from 1 to 10% elongation. The strain sensor of this study has high potential to use for strain sensing technology and is capable of detecting small body movements.

Abstract: Ternary polymer blends of ferroelectric Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, heterostructure Polyurethane (PU) with hard and soft segments, and amorphous Polymethyl methacrylate (PMMA) has been investigated on energy storage performances and electrocaloric effect. The microstructure phase of polymer blends has been analyzed using the X-ray diffraction (XRD) technique. The frequency-dependence of dielectric properties for polymers blend has been conducted. The ferroelectric, energy storage and electrocaloric properties of polymers blend depending on temperature were studied. The result showed that the dielectric constant of PVDF-HFP@PU composite is higher than PVDF-HFP@PMMA composites due to the strong interfacial polarization effect and contribution of the polymer blend. Moreover, it was noted that the crystalline–amorphous interface properties depend on the polymer blend with PU and PMMA, resulting in ferroelectric, energy storage and electrocaloric properties when temperature increases. Therefore, the comparison based on heterostructure and amorphous structure for series polymer blends can be used to predict practical devices.

Abstract: Resistance to ultraviolet light is an essential factor that coating materials must possess, especially for outdoor applications. In this study, the effect of ultraviolet light exposure on the properties of polyurethane coating with the addition of chlorinated rubber was systematically examined. The ultraviolet light exposure was performed using an ultraviolet weathering tester for 500 hours. The samples were investigated through mechanical testing, complemented by scanning electron microscope and Fourier transform infrared spectroscopy. The increase in the tensile strength and elongation at break of the polyurethane coating with the addition of chlorinated rubber was observed and compared to the pristine sample. In the beginning of the ultraviolet exposure, the tensile strength increased 486% and 114% for pristine polyurethane and polyurethane/chlorinated rubber until of 80 hours ultraviolet exposure, indicating repolymerization during the ultraviolet exposure. It was confirmed by the Fourier transform infrared spectra which showed an increase in peak intensity at wave number of 1712 cm־ˡ which indicated C=O bond in the polyurethane. The surface morphology showed micro-cracking caused by ultraviolet exposure. Finally, it was concluded that the addition of chlorinated rubber improved the resistance to ultraviolet light.

Abstract: Mild steels were the most frequently used materials in industries and factories since it possesses unique properties but due to weak environmental changes, these cause deterioration and corrosion to the materials’ surface. To prevent such, protective coatings were applied to protect against corrosion in which by incorporating titanium nanoparticles in polyurethane coatings. Titanium nanoparticles were synthesized using titanium butoxide as a precursor. The obtained nanoparticles were used as an inhibitor mixed with coconut oil-based polyurethane polyol blend against the corrosion on mild steel of 3.5% of sodium chloride solution which has been investigated using the Tafel polarization technique. The polarization curves of the corrosion potential for bare mild steel, along with different amounts of titanium nanoparticles coating, exhibit a positive shift. This shift indicates that the coating film effectively reduces the transport path for the corrosive solution, providing a protective barrier against corrosion. This observation is further supported by the results of the adhesive strength test, which demonstrates that the attachment of the coating films to the metal increases with higher amounts of titanium nanoparticles. This indicates improved adhesion and a stronger bond between the coating and the substrate, enhancing the overall corrosion resistance. The increase of contact angle test confirms the improvement of the coating’s hydrophobicity with the addition of titanium nanoparticles. This suggests that the coating repels water more effectively, further contributing to its protective properties against corrosion. Results also show that the addition of 4wt% of titanium nanoparticles has better anti-corrosion properties than the PU CCP alone, and 0.5, 1.0, and 2.0wt% of titanium added.

Abstract: In this paper, the performance of microstrip patch antenna that is made of fully biodegradable materials has been studied. The polymer resins of Polyurethane as a binder agent were produced using polyol extracted from palm oil while the host composites were made from oil palm empty fruit bunch fiber. The performance of Polyurethane – Oil Palm (PolyOP) Empty Fruit Bunch composite as a microwave dielectric substrate was tested by fabricating microstrip patch antenna on it. The performance of fabricated patch antenna was measured using Vector Network Analyzer (VNA) and is compared with simulation results obtained from High Frequency Structure Simulator (HFSS) simulator. The difference of percentage in resonant frequency, return loss, bandwidth and VSWR between simulation and measurement were found to be 0.4%, 75.2%, 67.9%, and 12.7%, respectively.