Injectable and in situ foaming shape-adaptive porous Bio-based polyurethane scaffold used for cartilage regeneration

Irregular articular cartilage injury is a common type of joint trauma,often resulting from intense impacts and other factors that lead to irregularly shaped wounds,the limited regenerative capacity of cartilage and the mismatched shape of the scaffods have contributed to unsatisfactory therapeutic outcomes.While injectable materials are a traditional solution to adapt to irregular cartilage defects,they have limitations,and injectable materials often lack the porous microstructures favorable for the rapid proliferation of cartilage cells.In this study,an injectable porous polyurethane scaffold named PU-BDO-Gelatin-Foam(PUBGF)was prepared.After injection into cartilage defects,PUBGF forms in situ at the site of the defect and exhibits a dynamic microstructure during the initial two weeks.This dynamic microstructure endows the scaffold with the ability to retain substances within its interior,thereby enhancing its capacity to promote chondrogenesis.Furthermore,the chondral repair efficacy of PUBGF was validated by directly injecting it into rat articular cartilage injury sites.The injectable PUBGF scaffold demonstrates a superior potential for promoting the repair of cartilage defects when compared to traditional porous polyurethane scaffolds.The substance retention ability of this injectable porous scaffold makes it a promising option for clinical applications.

Synthesis and Characterization of Nonionic Waterborne Polyurethane and Application to Wool Fabric Finishing

A nonionic waterborne polyurethane(WPU) was synthesized by the self-emulsification method using polyether diol(N220),isophorone diisocyanate(IPDI),trimethylolpropane poly(ethylene glycol monomethyl ether)(N120),1,4-butanediol(BDO) and trimethylolpropane(TMP) as the main materials.The effects of the NCO/OH ratio on the emulsion and film properties of NWPU were explored.The experimental results show that the NWPU prepared at an NCO/OH ratio of 1.1 has good emulsion stability and easy film formation,and the resultant film was elastic,soft,and transparent.The sample was used for wool finishing and the application performance was evaluated.When the NWPU dosage reached 40 g·L^(-1),the fabric area felt shrinkage rate reduced from 8.97% to 4.75%,the pilling rating raised from grade 2-3 to grade 4,and the whiteness value only decreased by 3.87%.

Propagation Properties of Shock Waves in Polyurethane Foam based on Atomistic Simulations

Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics simulations.Firstly,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental data.The pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock wave.The microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete compaction.Finally,it leads to stress relaxation and velocity homogenization.The shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of density.Besides,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the system.The energy is dissipated mainly through the multiple interactions of the waves under shock.The energy is dissipated mainly by the friction between atoms under non-shock.

Synthesis of Organic-Inorganic Hybrid Aluminum Hypophosphite Microspheres Flame Retardant and Its Flame Retardant Research on Thermoplastic Polyurethane

Aluminum hypophosphite microspheres(AHP) were synthesized by hydrothermal method using NaH2PO2·H2O and AlCl3·6H2O as raw materials, and then the AHP microspheres were polymerized by surface polymerization of micro-nanospheres with cyclic cross-linked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)(PZS). A new organic-inorganic poly(phosphonitrile)-modified aluminum hypophosphite microspheres(PZS-AHP) were synthesized by encapsulation and applied to flame retardant thermoplastic polyurethane(TPU). The microstructure and chemical composition of the PZS-AHP microsphere were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray spectroscopy. The thermal stability of PZS-AHP microsphere was explored with thermogravimetric analysis. Thermogravimetric data indicate that the PZS-AHP microspheres have excellent thermal stability. The thermal and flame-retarding properties of the TPU composites were evaluated by thermogravimetric(TG), limited oxygen index tests(LOI), and cone calorimeter test(CCT). The TPU composite achieved vertical burning(UL-94) V-0 grade and LOI value reached 29.2% when 10 wt% PZS-AHP was incorporated. Compared with those of pure TPU, the peak heat release rate(pHRR) and total heat release(THR) of TPU/10%PZS-AHP decreased by 82.2% and 42.5%, respectively. The results of CCT indicated that PZS-AHP microsphere could improve the flame retardancy of TPU composites.

Large-scale model testing of high-pressure grouting reinforcement for bedding slope with rapid-setting polyurethane

Bedding slope is a typical heterogeneous slope consisting of different soil/rock layers and is likely to slide along the weakest interface.Conventional slope protection methods for bedding slopes,such as retaining walls,stabilizing piles,and anchors,are time-consuming and labor-and energy-intensive.This study proposes an innovative polymer grout method to improve the bearing capacity and reduce the displacement of bedding slopes.A series of large-scale model tests were carried out to verify the effectiveness of polymer grout in protecting bedding slopes.Specifically,load-displacement relationships and failure patterns were analyzed for different testing slopes with various dosages of polymer.Results show the great potential of polymer grout in improving bearing capacity,reducing settlement,and protecting slopes from being crushed under shearing.The polymer-treated slopes remained structurally intact,while the untreated slope exhibited considerable damage when subjected to loads surpassing the bearing capacity.It is also found that polymer-cemented soils concentrate around the injection pipe,forming a fan-shaped sheet-like structure.This study proves the improvement of polymer grouting for bedding slope treatment and will contribute to the development of a fast method to protect bedding slopes from landslides.

Preparation and Tribological Properties of Onion-like Carbon/Waterborne Polyurethane Coatings

Rice husk powder was used as a carbon source in a high-temperature carbonization reaction for the production of rice husk ash(RHA).Under the catalysis of ferric nitrate,onion-like carbon(OLC)nanomaterial with a particle size of approximately 200 nm was successfully prepared and incorporated into waterborne polyurethane(WPU).The tribological properties of the coatings were determined using a controlled-atmosphere tribometer(WMT-2E)under dry-friction conditions.Following the friction test,the friction mechanism was investigated by characterizing the abrasive spot surfaces of the test samples using 3D laser microscopy and scanning electron microscopy/energy dispersive spectrometer.The final results demonstrated that the thermal stability of WPU composite coatings containing various concentrations of OLC nanoparticles was significantly enhanced,binding forces between coatings and steel sheets increased,and hardness improved compared to pure WPU coatings.Tribological tests revealed a notable enhancement in the anti-wear properties of WPU coatings due to the presence of OLC particles.Specifically,the wear rate of the 1.5%OLC/WPU coating was reduced by 45.3%.The coating’s anti-wear mechanism was attributed to the improvement in the mechanical properties of WPU due to OLC,as well as OLC’s participation in the formation of a transfer film under induced friction,which protected the matrix.

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°.

Experimental investigation on weak shock wave mitigation characteristics of flexible polyurethane foam and polyurea

In recent years,explosion shock wave has been considered as a signature injury of the current military conflicts.Although strong shock wave is lethal to the human body,weak shock wave can cause many more lasting consequences.To investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual protection.Experimental results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not damaged.The shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic characteristics.The overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample thickness.For the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three materials.In this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are designed.Different layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective performance.Within the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm respectively.The overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of single-layer polyurea and polyurethane foam with higher areal density.

Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering

The purpose of this research study was to investigate the properties of polyurethane coatings based on lignin nano-particles.For this purpose,the prepared coatings were applied to pine wood surfaces and weathered artificially.Subsequently,color and gloss of the coatings were measured before and after the weathering test.Field emission scanning electron microscopy(FE-SEM)micrographs prepared from the coatings showed that the average size of nano-particles in the polyurethane substrate was approximately 500 nm.Nuclear magnetic resonance(13C-NMR)spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based polyurethane.Differential calorimetric analysis(DSC)test revealed that the glass-transition temperature(Tg)of lignin nanoparticles modified with diethylenetriamine(DETA)was 112.8℃ and Tg of lignin nano-particles modified with ethylenediamine(EDA)was 102.5℃,which is lower than the Tg of un-modified lignin(114.6℃)and lignin modified with DETA(126.8℃)and lignin modified with EDA(131.3℃).The coatings modified with lignin nano-particles had a greater change in gloss.The lignin nano-particles in the modified coating are trapping hydroxyl radicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodified polyurethane coatings.After weathering test,the nano-lignin-based coating had a rougher surface with a lower contact angle(0.78°)compared to the unmodified polyurethane coating(0.85°).

Bio-Based Rigid Polyurethane Foams for Cryogenic Insulation

Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m·K and an apparent density of 37-40 kg/m^(3).The developed rigid PU foams had anisotropic compression strength properties,which were higher parallel to the foaming direction.Moreover,the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix;thus,the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry,dynamic mechanical analysis,and thermogravimetric analysis methods.Lastly,the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.

Adhesion of Technical Lignin-Based Non-Isocyanate Polyurethane Adhesives for Wood Bonding

Lignin is the most abundant aromatic natural polymer,and receiving great attention in replacing various petro-leum-based polymers.The aim of this study is to investigate the feasibility of technical lignin as a polyol for the synthesis of non-isocyanate polyurethane(NIPU)adhesives to substitute current polyurethane(PU)adhesives that have been synthesized with toxic isocyanate and polyols.Crude hardwood kraft lignin(C-HKL)was extracted from black liquor from a pulp mill followed by acetone fractionation to obtain acetone soluble-HKL(AS-HKL).Then,C-HKL,AS-HKL,and softwood sodium lignosulfonate(LS)were used for the synthesis of technical lignin-based NIPU adhesives through carbonation and polyamination and silane as a cross-linker.Their adhesion per-formance was determined for plywood.FTIR spectra showed the formation of urethane bonds and the reaction between lignin and silane.The NIPU adhesives prepared with C-HKL showed the highest adhesion strength among the three lignin-based NIPU adhesives.As the silane addition level increased,the adhesion strength of NIPU adhesives increased whereas formaldehyde emission decreased for all NIPU adhesives prepared.These results indicate that NIPU adhesives based on technical kraft lignin have a great potential as polyol for the synth-esis of bio-based NIPU adhesives for wood bonding.

The role of polyurethane foam compressible layer in the mechanical behaviour of multi-layer yielding supports for deep soft rock tunnels

The polyurethane foam(PU)compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels.Nevertheless,the mechanical behaviour of the multi-layer yielding supports has not been thoroughly investigated.To fill this gap,large-scale model tests were conducted in this study.The synergistic load-bearing mechanics were analyzed using the convergenceconfinement method.Two types of multi-layer yielding supports with different thicknesses(2.5 cm,3.75 cm and 5 cm)of PU compressible layers were investigated respectively.Digital image correlation(DIC)analysis and acoustic emission(AE)techniques were used for detecting the deformation fields and damage evolution of the multi-layer yielding supports in real-time.Results indicated that the loaddisplacement relationship of the multi-layer yielding supports could be divided into the crack initiation,crack propagation,strain-hardening,and failure stages.Compared with those of the stiff support,the toughness,deformability and ultimate load of the yielding supports were increased by an average of 225%,61%and 32%,respectively.Additionally,the PU compressible layer is positioned between two primary linings to allow the yielding support to have greater mechanical properties.The analysis of the synergistic bearing effect suggested that the thickness of PU compressible layer and its location significantly affect the mechanical properties of the yielding supports.The use of yielding supports with a compressible layer positioned between the primary and secondary linings is recommended to mitigate the effects of high geo-stress in squeezing tunnels.

Effect of Amine Type on Lignin Modification to Evaluate Its Reactivity in Polyol Construction for Non-Isocyanate Polyurethanes(NIPU)

Polyols are groups of organic compounds which contain carbon and are randomly linked to other atoms,especially carbon-carbon and carbon-hydrogen.These compounds are mainly used as reactants to make other polymers.Among biopolymers,lignin is regarded as the base of a new polymer in polyol construction.The present study aimed to investigate the effects of amine type(diethylenetriamine and ethylenediamine)on the modification of lignin-based polyols,so as to provide an alternative to petroleum polyols and,in turn,increase functional groups and reduce their harm to humans’health and the environment.To this aim,first,lignin was extracted from raw liquor.Next,the extracted lignin was reacted with diethylenetriamine(DETA)and ethylenediamine(EDA).Finally,the Mannich method was used for the reaction between amine lignin and propylene carbonate.The results of the Fourier Transform Infrared(FTIR)spectroscopy analysis showed that modification with DETA led to more structural change in lignin and peak 1100 indicates the presence of C–O bond related to urethane bonds in modified lignin.Moreover,adding propylene carbonate to aminated lignin did not result in much change in the results of the FTIR analysis.Additionally,urethane bonds can be seen in the results of GPC at 400℃–500℃.Furthermore,a slight decrease in thermal stability was observed in lignin modified with amine and propylene carbonate,compared to the raw lignin sample.

Polyurethane Hybrid-Based Wood Adhesive: Review

Based on commercially available polyvinyl alcohol (PVA) stabilised polyvinyl acetate (PVAc), emulsion adhesives are neither heat nor moisture-resistant and show weak strength at high relative humidity and high temperatures. Pre- or post-crosslinking is another method used to manufacture a conventional vinyl-based homopolymers or copolymers system with improved water resistance. Vinyl neodecanoate (VeoVa), N-methylolacrylamide (NMA), Methacrylamide, methacrylic acid (MAA), and other self-crosslinking comonomers are typically inserted to produce highly water-resistant vinyl based homopolymers or copolymers. Additionally, organic crosslinkers like glyoxal, glutaraldehyde, citric acid, tartaric acid, and the like, as well as inorganic crosslinkers like acidic metal salts like aluminium chloride, aluminium nitrate, boric acid, and the like, can be used to prepare the highly water-resistant vinyl based homopolymers or copolymers. It is also possible to combine the self-crosslinking comonomers with the organic crosslinkers. Recently, a different hybrid chemistry has been developed that improves lap shear strength, has outstanding water resistance, good durability, and doesn’t require any additional crosslinker agents. Two distinct polymers were combined to develop hybrid polymers. They usually involve mixing an organic polymer with a polymer. There are many capping agents that are used for polyurethanes to produce acrylics that are capped with polyurethane and used as an oligomer in PVAc wood glue. Here, in this paper, we reviewed the different hybrid chemistry based on polyurethane chemistry for wood bonding applications.

Hydrolysable Chestnut Tannin Extract Chemical Complexity in Its Reactions for Non-Isocyanate Polyurethanes(NIPU)Foams

Non-isocyanate polyurethane(NIPU)foams from a commercial hydrolysable tannin extract,chestnut wood tannin extract,have been prepared to determine what chemical species and products are taking part in the reactions involved.This method is based on two main steps:the reaction with dimethyl carbonate and the formation of urethane bonds by further reaction of the carbonated tannin with a diamine-like hexamethylene diamine.The hydroxyl groups on the tannin polyphenols and on the carbohydrates intimately linked with it and part of a hydrolysable tannin are the groups involved in these reactions.The carbohydrate skeleton of the hydrolysable tannin is also able to participate through its hydroxyl groups to the same two reactions rendering the whole molecular complex able to react to form NIPUs.The analysis by Matrix-Assisted Laser Desorption Ionization(MALDI-TOF)mass spectrometry and 13C Nuclear Magnetic Resonance(13C NMR)to further investigate the reaction mechanisms involved revealed the unsuspected complexity of chestnut hydrolysable tannin,with different fragments reacting in different manners forming a hardened network of considerable complexity.As the morphology and performance of these types of foams changes slightly with the change in the amount of glutaraldehyde and hexamine hardeners,the best performing foam formulation previously determined was scanned by SEM and analysed chemically for the structures formed.

Modification of Nano-α-Al2O3 and Its Influence on the Surface Properties of Waterborne Polyurethane Resin Composite Passivation Films

Silane coupling agent KH560 was used to modify the surface of nano-α-Al2O3 in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al2O3 was determined by nano-particle size analyzer, and the effects of nano-α-Al2O3 content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al2O3 were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al2O3 dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al2O3 increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al2O3.

Synthesis of Ionic and Non-Ionic Modified Waterborne Polyurethane Curing Agent

By using HDI and TMP as the main raw materials,polyethylene glycol 400(PEG400)is used as a non-ionic hydrophilic modifier,and sodium hydroxyethyl sulfonate is used as an ionic hydrophilic modifier to synthesize a dual hydrophilic modified polyurethane curing agent.Research revealed that introducing PEG400 for hydrophilic chain segments and sodium hydroxyethyl sulfonate for hydrophilic ionic groups in the polyurethane curing agent component leads to a uniform distribution of hydrophilic components,significantly enhancing compatibility with the aqueous polyol component,and results in excellent film performance.The synthesis process and film were characterized using Fourier transform infrared spectroscopy and high-resolution scanning electron microscopy in the study.

Advancements and Applications of Polyurethane Curing Technology in Railway Track Bed Construction in China

This paper examines the application of polyurethane curing technology in the construction of railway track beds,with a specific focus on its implementation in China’s rapidly developing railway infrastructure.The study begins by identifying the limitations of traditional ballasted track beds,especially under the demands of high-speed and heavyload railways.It then methodically analyzes the advantages of polyurethane-cured track beds,highlighting their improved mechanical properties,including enhanced stability and durability.The paper further explores the benefits of transitioning to prefabricated polyurethane track beds,emphasizing significant cost reductions,better construction quality,and enhanced maintainability.Through a detailed review of experimental data and practical applications,the paper demonstrates the efficacy of polyurethane track beds in various railway settings.A critical part of the research involves optimizing the structural parameters of polyurethane track beds to achieve the best balance of mechanical and damping properties.The conclusion of the paper underscores the potential of polyurethane curing technology as a transformative approach to railway track bed construction,offering a solution to the challenges posed by traditional methods and aligning with the evolving needs of modern railways.

Pu在膨润土层中的反应性迁移模拟研究(2)——Pu的种态分布及反应性迁移分析

为评估柯尔碱膨润土工程屏障材料的安全性能,采用考虑渗流扩散、溶解-沉淀、表面配位吸附、放射性衰变等多过程动态耦合的反应性迁移模拟方法,综合运用TOUGHREACT等程序开展了Pu在柯尔碱膨润土层中反应迁移的数值模拟,结合地下水-膨润土体系演化模拟分析了Pu的种态分布特征,叠加表面配位模型预测分析了Pu的长期迁移规律。结果表明:地下水中Pu主要以难迁移的Pu(OH)_(4)(aq)形式存在;由于膨润土的低渗透性和强吸附性,正常情景下Pu的扩散范围很小而将长期滞留于1 m厚膨润土中;在忽略强吸附阻滞作用的保守情景下,Pu在渗流作用下可扩散迁移出膨润土层;考虑到长时间尺度下不可避免存在的不确定性,建议重视渗流扩散为主导的其他过程和情景研究。

南海环境中Pu、Np的清除机制和空间迁移模拟研究

海洋环境中Pu、Np两种放射性元素源自人类核活动.由于洋流、海陆交汇等多重效应导致Pu、Np被富集于边缘海区域,威胁人类的环境安全.目前国内外对海洋中Pu、Np的研究未成体系,研究方法多局限于含量分析.为研究河流输入量、地形、气候等因素对于海洋中Pu、Np清除效率的影响,本文采用扇形磁场高分辨率质谱(SF-ICP-MS)对南海水体、沉积物中的Pu、Np比活度,^(240)Pu/^(239)Pu和^(237)Np/^(239)Pu原子比进行精确分析.在模拟海洋生态环境和顺序提取实验基础上,研究Pu、Np在海洋中的扩散问题.根据得到的Pu、Np比活度和同位素原子比等在水体、颗粒物以及沉积物中的分布数据,拟合得到Pu、Np在南海传输和扩散的特征关键参数,以解释南海海水中Pu、Np的清除机制.最后利用数据构建南海Pu、Np空间迁移与清除的稳态模型(S-ADE),后续将通过模拟及现场取样分析对模型进行相互校验.研究结果可为核事故中Pu、Np等放射性污染物的溯源与迁移的快速分析与综合评估,以及放射性污染防护与治理提供方案.