Preparation and Analysis of Thermal and Mechanical Properties of HTPB-type Polyurethane Elastomer Containing Paraffin Microcapsules

Two microcapsules with different paraffin phase changes were prepared using styrene-divinylbenzene copolymer and melamine resin as the capsule wall and paraffin(with a melting point of 50°C)as the capsule core.The microcapsules were directly added to the hydroxyl terminated polybutadiene(HTPB)-polyurethane elastomer system to fabricate the polyurethane elastomer composites.The thermodynamic stability and mechanical properties of the material were then studied.The results show that the thermal stability of the polyurethane elastomer does not decrease after adding paraffin phase change microcapsules,and the thermal stability of the polyurethane elastomer with melamine resin as the wall increases.Tensile strength increased from 367 kPa to 797 kPa,and compression strength increased from 245.9 N to 344.7 N.In addition,capsule walls comprised different monomers/paraffin microcapsules of the copolymer of styrene and divinylbenzene.The optimal mechanical property was obtained at a monomer/paraffin ratio of 1:1.The compression strength increased and the tensile strength decreased.The tensile strength of the microcapsule with melamine resin capsule wall and the compression strength of the microcapsule with polystyrene capsule wall were considerably improved.

Influences of Polyol on the Chemical, Thermal, and Mechanical Properties of Polyurethane Elastomers Crosslinked by <i>β</i>-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized from an aromatic diisocyanate (4, 4’-diphenylmethane diisocyanate);a polyether polyol (polytetramethylene glycol, molecular weight: 1000), polyester polyol (poly-caprolactonediol, molecular weight: 1000, or polycarbonate diol, molecular weight: 1000);and β-cyclodextrin (β-CD) as a cross-linker. The effect of the polyol on the morphologies and chemical, thermal, and mechanical properties of the resultant β-CD-based PUEs were investigated in this study. The obtained films were characterized via solubility and swelling tests (chemical properties), differential scanning calorimetry (crystallinity degree), dynamic mechanical analysis (thermal stability), thermogravimetric analysis (thermal stability), tensile testing (mechanical properties), nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy (morphology), contact angle determination (morphology), and scanning electron microscopy (morphology).

Preparation and properties of cast polyurethane elastomers with molecularly uniform hard segments based on 2,4-toluene diisocyanate and 3,5-dimethyl-thioltoluenediamine

A series of three cast polyurethane elastomers were prepared from 2,4-toluene diisocyanate (TDI) and 3,5-dimethyl-thioltoluenediamine (D MTDA) chain extender, with polyethylene adi-pate (PEA), polyoxytetramethylene glycol (PTMG) and polycaprolactone (PCL) soft seg-ments. The polyol molecular weights em-ployed was 2000g/mol. The polyurethane elastomers were characterized by an elec-tronmechanical universal testing machine, an Akron abrasion loss tester, a LX-A Shore du-rometer, a rebound resilience equipment and a Dynamic- Mechanical analyzer. In addition, fractured surface of the polyurethane elas-tomers was investigated by a field emission scanning electron microscopy (SEM). The test results showed the PCL based elastomer ex-hibits the excellent tear and stress-strain properties that polyester based elastomers offer, while retaining superior compression set and resilience similar to polyether based elas-tomers. The static and dynamic properties of the PCL based elastomer were more suitable for dynamic applications. The SEM micro-graphs of all polyurethane samples indicated the existing of the microphase separation structure. Particles of the dispersed phase formed by the hard phase and crystalline part of the soft phase grows bigger with the in-creasing crystallinity of the soft segments. The hard domains are irregular shapes and with the sizes of a few micrometers.

Predicting the Mechanical Properties of Polyurethane Elastomers Using Machine Learning

Bridging the gap between the computation of mechanical properties and the chemical structure of elastomers is a long-standing challenge.To fill the gap,we create a raw dataset and build predictive models for Young’s modulus,tensile strength,and elongation at break of polyurethane elastomers(PUEs).We then construct a benchmark dataset with 50.4%samples remained from the raw dataset which suffers from the intrinsic diversity problem,through a newly proposed recursive data elimination protocol.The coefficients of determination(R^(2)s)from predictions are improved from 0.73-0.78 to 0.85-0.91 based on the raw and the benchmark datasets.The fitting of stress-strain curves using the machine learning model shows a slightly better performance than that for one of the well-performed constitutive models(e.g.,the Khiêm-Itskov model).It confirmed that the black-box machine learning models are feasible to bridge the gap between the mechanical properties of PUEs and multiple factors for their chemical structures,composition,processing,and measurement settings.While accurate prediction for these curves is still a challenge.We release the raw dataset and the most representative benchmark dataset so far to call for more attention to tackle the longstanding gap problem.

Fabrication of Silane and Desulfurization Ash Composite Modified Polyurethane and Its Interfacial Binding Mechanism

Polyurethane/desulfurization ash(PU/DA)composites were synthesized using"one-pot method",with the incorporation of a silane coupling agent(KH550)as a"molecular bridge"to facilitate the integration of DA as hard segments into the PU molecular chain.The effects of DA content(φ)on the mechanical properties,thermal stability,and hydrophobicity of PU,both before and after the addition of KH550,were thoroughly examined.The results of microscopic mechanism analysis confirmed that KH550 chemically modified the surface of DA,facilitating its incorporation into the polyurethane molecular chain,thereby significantly enhancing the compatibility and dispersion of DA within the PU matrix.When the mass fraction of modified DA(MDA)reached 12%,the mechanical properties,thermal stability,and hydrophobicity of the composites were substantially improved,with the tensile strength reaching 14.9 MPa,and the contact angle measuring 100.6°.

Thermal properties of polyurethane elastomer with different flexible molecular chain based on para-phenylene diisocyanate

This work focuses on the relationship between flexibility of molecular chains and thermal properties of polyurethane elastomer（PUE）, which laid the foundation of further research about how to improve thermal properties of PUE. A series of PUE samples with different flexibility of molecular chains was prepared by using 1,4-butanediol（1,4-BDO）/bisphenol-a（BPA） blends with different mole ratios including9/1, 8/2, 7/3, 6/4 and 5/5. As comparison, PUE extended with pure 1,4-BDO and BPA was also synthesized.These samples were characterized by differential scanning calorimetry（DSC）, thermogravimetric analysis（TGA）, dynamic mechanical analysis（DMA）, etc. The results showed that with the decrease in flexibility of molecular chains the glass transition temperature（Tg） increased and low-temperature properties became worse. Besides, all samples had a certain degree of microphase separation, and soft segments in some samples were crystallized, i.e. the decreasing flexibility of molecular chains led to the impossibility of chains tightly packing and crystalline domains forming so that the degree of microphase separation decreased and the thermal properties became worse.

DynamicMechanical and Chemorheology Analysis for the Blended Epoxy System with Polyurethane Modified Resin

As the important matrix material,epoxy resin has been widely used in the composites for various fields.On account of the poor toughness of epoxy resin limiting their suitability for advanced applications,considerable interests have been conducted to modify the epoxy resin to meet the engineering requirements.In this study,the bio-based polyurethane(PU)modified resin was adopted to modify the pure bisphenol-A epoxy by blending method with various proportions.Aiming to illuminate the curing behavior,mechanical and thermal properties,the blended epoxy systems were characterized by viscosity-time analysis,dynamic mechanical analysis(DMA)at different frequencies and temperatures,mechanical tensile test,thermogravimetric analysis(TGA)and Fourier transform infrared(FT-IR)spectroscopy.The results indicated that the introduction of PU modified epoxy was found to significantly inhibit the viscosity growth rates especially when the content of PU modified epoxy resin is higher than 60%.Notwithstanding the dynamic modulus and T_(g)reduced with the increment of PU modified epoxy,remarkable increment on the elongation at break was found and the flexibility was greatly promoted with the introduction of PU modified epoxy.The proportion of PU modified epoxy in the blends should be put balance considerations to obtain optimal mechanical properties.TGA results and FTIR spectrum demonstrated that the addition of PU modified epoxy did not change the thermal decomposition mechanism and chemical reaction mechanism,but the addition of PU modified epoxy inhibits the curing reaction of epoxy resin by measured and calculated the damping temperature domain
T from 35.7℃ to 48.9℃.

Longitudinal Mechanical Properties of Small-Diameter Polyurethane Vascular Graft Reinforced by Tubular Knitted Fabric

The vascular graft with 4 mm diameter was prepared by casting one layer of polyurethane (PU) film onto the knitting tubular fabric as the reinforced support. The effects of different PU content and wall thickness on the longitudinal mechanical properties of vascular graft were investigated. The breaking elongation, breaking force, initial modulus and breaking work were studied. The results showed that the longitudinal mechanical properties of vascular graft were enhanced as the content of polyurethane increased, which resulted from the combination of PU excellent elasticity and fabric preferable strength.

Effects of Size and Surface Modification of Multi-walled Carbon Nanotubes on Mechanical Properties of Polyurethane-based Nanocomposites

Polyurethanes/multi-walled carbon nanotube （PU/CNT） composites were prepared with a help of ultrasonically dispersing CNT in the traditional procedure of synthesizing polyurethane. In this case, the various loading levels, sizes and surface-modified groups were considered to regulate the mechanical performances of the PU/CNT nanocomposites. Moreover, the structure and mechanical properties of all the PU/CNT nanocomposites were investigated by attenuated total reflection-Fourier transform infrared spectroscopy, dynamic mechanical analysis, scanning electron microscope, transmission electron microscope, and tensile testing. The experimental results showed that a moderate loading-level of 0.1wt% and a diameter of 10-15 nm for CNT could produce the maximum tensile strength and elongation while it was worth noting that the surface carboxylation of CNT could further enhance the tensile strength and elongation of the PU/CNT nanocomposites.

Preparation, morphology and mechanical properties of acrylate-modified polyurethane/unsaturated polyester resin graft-IPNs

Acrylate modified polyurethane resin was first synthesized, and interpenetrated with unsaturated polyester resin to form IPNs and gradient IPNs which cured at room temperature. The polymerization process was traced by an IR spectroscopy technique and the simultaneous interpenetrating techniques were determined. The morphology of these IPNs were estimated by TMA and TEM methods. The results indicated that large amount of interpenetrating and entanglement make T g linked up effectively, and domains between two phases can be in nanometre ranges, which changed with composition ratios. The mechanical properties results showed that IPNs varied from elastomeric to plastic materials. It was noteworthy that, with the introduction of modified groups and the formation of graft construction in IPNs, the miscibility in the systems was improved a lot. These further led to the improved mechanical properties of IPNs with elastomer reinforced and plasticizer toughened as well. The reinforced miscibility between the networks can apparently change mechanical property especially for the gradient ones when the materials are elongated.

Effect of Cellular Structure on Mechanical Properties of Polyurethane Foam Curing Materials

Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.

Mechanical and Thermal Properties of Sugar Palm Fiber Reinforced Thermoplastic Polyurethane Composites:Effect of Silane Treatment and Fiber Loading

The aim of the present study was to develop sugar palm fiber(SPF)reinforced thermoplastic polyurethane(TPU)composites and to investigate the effects of fiber surface modification by 2%silane treatment and fiber loading(0,10,20,30,40 and 50 wt%)on the mechanical and thermal properties of the obtained composites.Surface treatment was employed to improve the fiber-matrix interface,which was expected to boost the mechanical strength of the composites,in terms of tensile,flexural and impact properties.Thermal properties were also investigated by thermal gravimetric analysis(TGA)and dynamic mechanical analysis(DMA)to assess the thermal stability of the developed composites.Furthermore,scanning electron microscopy(SEM)was used to study the tensile fracture samples of composites with a view towards evaluating the effects of fiber surface treatments on the fiber/matrix interfacial bonding.The findings of this study reveal that the silane treatment has determined good bonding and linkage of the cellulose fiber to the TPU matrix,hence contributing to enhanced mechanical and thermal properties of the composites.The composite formulation with 40 wt%sugar palm fiber loading showed optimum values such as 17.22 MPa for tensile,13.96 MPa for flexural,and 15.47 kJ/m^2 for impact strength.Moreover,the formulations with higher fiber content exhibited satisfactory values of storage modulus and thermal degradation,while their good interfacial adhesion was evidenced by SEM images.

Synthesis and Properties of Novel Polyurethane-Imide Elastomers

Novel polyurethane-imide elastomers were prepared from isocyanates (hexamethylene, and 4,4’-dicyclohexyl diisocyanates), polytetramethylene glycol (PTMG1000, Mw = 1000), pyromellitic dianhydride, and 4,4’-diphenylmethane diamine. The formation of PUIEs was confirmed by Fourier transform infrared spectroscopy. The resultant films were studied through X-ray diffraction analysis, contact angle measurement, atomic force microscopy, solubility and swelling tests, tensile test, differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis.

Mechanical Properties of Small-diameter Superfine Silk Powder/Polyurethane Vascular Graft Reinforced by Tubular Knitted Fabric

In this paper,a kind of composite microtube,which is made from superfine silk powder and polyurethane,reinforced by polyster and spandex tubular fabrics,was examined.The cross-section of composite microtubes were microporous,and micropores were uniform distributed,the inner surface was relatively smooth.The results showed that the wall thickness of composite microtubes increased,which led to the strength,the breaking work and the initial modulus incresead;that the spandex content increased brought about the initial modulus and the breaking work decreased,but the breaking extension and the breaking load were firstly increased and then decreased;and all the mechanical properties decreased as the SFSP content increased.

Structure and Mechanical Properties of Waterborne Polyurethane-based Composites Filled with Self-assembled Supramolecular Nanoplatelets

New composites of waterborne polyurethane （WPU） as a matrix were prepared by incorporating rigid supramolecular nanoplatelets （SNs） as filler, which were self-assembled by the selective inclusion of β-cyclodextrin （β-CD） onto poly（propylene oxide） （PPO） segment in the poly（ethylene oxide）- block-PPO-block-poly（ethylene oxide） （PEO-b-PPO-b-PEO）. It is worth noting that, when the loading level of SN is lower than 3wt%, the SNs with moderate PEO length result in the simultaneous increase in strength, elongation and Young＇s modulus in contrast with neat WPU. If there is no stretching free PEO chain, both strength and elongation decrease in spite of an increase in Young＇s modulus. However, too long PEO chains result in the decrease of mechanical performances while the relatively higher loading-level of SNs also inhibits the enhancement of strength and elongation.

Investigate the Effect of the Magnetic Field on the Mechanical Properties of Silicone Rubber-Based Anisotropic Magnetorheological Elastomer during Curing Process

In this investigation,a new silicone rubber-based MRE material was prepared to be used as a forming medium in manufacturing thin-walled complexshaped Ni-based tubes through the bulging process.Thus,it is significant to investigate the effect of magnetic field intensity,magnetic field loading time,and angle on the mechanical properties of the prepared MRE material during the curing process.The obtained results showed that increasing the magnetic field intensity during the curing process can improve the orientation of the chain structure in the elastomer matrix effectively.However,its mechanical properties are the best under the corresponding magnetic field intensity of 321 mT.Besides,by extending the magnetic field loading time in the curing process,the orientation of the chain structure was optimized,at the same time,the mechanical properties were also improved,and the best loading time is about 20–25 min.By changing the loading angle of the magnetic field during the curing process,the mechanical properties of the MRE were improved.When the loading angle of the magnetic field is 90°,the elastomer showed the best compression mechanical properties and excellent compression reversibility.Besides,for the anisotropic MRE material,the performance with magnetic compression is always better than that without magnetic compression.

Mechanical, Thermal and Morphology Properties of Thermoplastic Polyurethane Copolymers Incorporating α,ω-Dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] of Varying Poly(propyleneoxide) Molecular Weight

Novel segmented thermoplastic polyurethane (TPU) copolymers were synthesized using two-step solventless bulk polymerization. 4,4’-methylenediphenyl diisocyanate (MDI) and 1,4-Butanediol (BDO) were used to form hard segment of TPU and α,ω-dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] (α,ω-dihydroxy-(PPO-PDMS-PPO)) was used to form soft segment of TPU, where the molar ratio of the –N=C=O/OH was 1.02 and the hard segment weight percentage was 30%. A series of TPUs were characterized by fourier transform infrared spectroscopy (FT-IR). The investigation of triblock oligomer’s PPO molecular weight impact on the derived TPU’s mechanical properties, thermal performance, surface water repellency and morphology performance was carried by Instron material tester, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angles (WCA), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDX) and wide angle X-ray diffraction (WAXD), respectively. FT-IR confirmed α,ω-dihydroxy-(PPO-PDMS-PPO) well cooperating into urethane structure and analyzed hydrogen bonding between N-H group with hard segment C=O group and N-H group with soft segment C-O-C group. DSC and WAXD results showed α,ω-dihydroxy-(PPO-PDMS-PPO) segments crystallization. SEM-EDX results showed that the presence of a spherulitic morphology, which arose from the crystallization of the PPO segments. The thermal properties measured by TGA and DSC were slightly affected by molecular weight of PPO and microphase separation. The weight loss of TPUs started between 294°C and 300°C, and Tg was in the range of -70°C to -107°C. TPU copolymers’ surface hydrophobicity property was excellent with WCA range of 95°?to 112°. TPU-3 with 1000 molecular weight PPO has the optimized mechanical properties with tensile strength 16.4 MPa and the modulus at 100% elongation 6.2 MPa and elongation 398%.

Thermoplasticity in Polyurethane-Imide Elastomers

Polyurethane-imide elastomers (PUIEs) are formed from isocyanates, polyols, diamines, and acid anhydrides through liquid polymerization. However, thermoplastic PUIEs have rarely been reported because the synthesis of thermoplastic PUIEs remains a challenge in polymer chemistry. In this study, PUIEs were prepared from 4,4'-diphenylmethane diisocyanate, polyols (polytetramethylene glycol (Mw = 1000), polycaprolactone diol (Mw = 1000), and polycarbonate diol (Mw = 1000)), 4,4'-oxydianiline, and acid anhydrides (pyromellitic dianhydride and 4,4'-oxydiphtaric anhydride). The thermoplasticities of the resultant PUIEs were investigated, and only PUIEs synthesized using 4,4'-oxydiphtaric anhydride expressed thermoplasticity.

Analysis of the Performances and Optimization of Polyurethane Concrete with a Large Percentage of Fly Ash

The properties of polyurethane concrete containing a large amount of fly ash are investigated,and accordingly,a model is introduced to account for the influence of fly ash fineness,water ratio,and loss of ignition(LOI)on its mechanical performances.This research shows that,after optimization,the concrete has a compressive strength of 20.8 MPa,a flexural strength of 3.4 MPa,and a compressive modulus of elasticity of 19.2 GPa.The main factor influencing 28 and 90 d compressive strength is fly ash content,water-binder ratio,and early strength agent content.

CPE增容TPU/PVC共混弹性体及相形态

为提高热塑性聚氨酯弹性体(TPU)与聚氯乙烯(PVC)的相容性,以氯化聚乙烯(CPE)为增容剂,经双螺杆挤出机熔融共混制备TPU/PVC共混型热塑性弹性体,测试了不同CPE用量的共混弹性体的拉伸强度、断裂伸长率和硬度等力学性能,以及动态流变性能、动态力学性能和热稳定性。通过扫描电子显微镜(SEM)对共混弹性体的相态结构进行研究。结果表明,当TPU/PVC质量比为70/30时,共混弹性体综合力学性能最佳,拉伸强度为19.92 MPa,断裂伸长率为972%。随着CPE用量的增加,TPU/PVC共混弹性体的拉伸强度、断裂伸长率、硬度等均先增大后减小;CPE用量为6份时,TPU/PVC共混弹性体拉伸强度达到最大,为23.73 MPa,相较未加CPE时提高19.1%。加入CPE的共混弹性体复数黏度和储能模量均呈下降趋势。此外,CPE的加入还能有效提升弹性体高温热稳定性,TPU和PVC两种组分的损耗因子峰内移靠近,共混弹性体液氮脆断面的SEM照片显示PVC相筹明显变小且更为均匀,以上说明CPE对共混弹性体的增塑、增容作用明显,且CPE用量为6份时增容效果最佳。