Deterministic performance parameters for an automotive polyurethane clearcoat loaded with hydrophilic or hydrophobic nano-silica

In this study, two different nano-silica particles (hydrophilic, Aerosil TT600 and hydrophobic, Aerosil R972) were selected in order to provide the most transparent, UV-absorbent nano-clearcoats. These nano-silica particles were used to improve and optimize properties of 2-pack polyurethane clearcoats based on acrylic polyol. Micro-PIXE analysis was employed to illustrate distribution of nano-silica in the polyurethane matrix. Physical and chemical degradations were investigated via spectrophotometry and FTIR spectroscopy.Additionally, thermal stability and the ability of the clearcoats to resist simulated car wash conditions were also studied. Contrary to belief, coatings loaded with hydrophilic nano-silica which are more UV-absorbent had less durability in UV-B/H₂O accelerated tests.     

Investigating changes in electrochemical properties when nano-silica is incorporated into an acrylic-based polyurethane clearcoat

Two different types of nano-silica (i.e., hydrophilic Aerosil 200 and hydrophobic Aerosil R805) were employed in the preparation of 2-pack acrylic polyol polyurethane nano-coatings so that the electrochemical properties of the resultant coatings could be investigated. Electrochemical impedance spectroscopy was used to evaluate the corrosion performances of such nano-coatings applied onto mild steel substrates that were immersed in 3.5% (w/w) NaCl solutions. It was observed coatings that contained nano-silica increased the barrier properties of the binder, as well as the coatings’ electrochemical resistance compared with pure polyurethane coatings. The surface tension of pure polyurethane was measured by a tensiometer. Rheological properties were also determined at various shear rates by a rotaviscometer. Results showed that the surface tension of hydrophobic nano-silica is very close to the pure polyurethane matrix, giving the better compatibility of the two. This was further confirmed by transmission electron microscopy and by the fact that the hydrophobically filled nano-silica coatings showed shear thinning behavior in the fluid state. Also observed was better corrosion performance of the resultant hydrophobic nano-coatings compared to coatings embedded with hydrophilic nano-silica.     

超临界CO2快速膨胀法制备SiO2/聚氨酯超疏水涂层

用超临界CO₂快速膨胀法制备了SiO₂/聚氨酯超疏水涂层。首先用十三氟辛基三乙氧基硅烷（F-硅烷）和γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷（KH-570）改性纳米二氧化硅,制备出含双键的纳米二氧化硅粒子,将其分散在超临界CO₂中,再利用超临界CO₂快速膨胀法将其喷射到双键封端的且已添加了引发剂的聚氨酯涂层表面,通过加热,使纳米二氧化硅粒子接枝在聚氨酯涂层表面,形成稳固粗糙结构,获得了超疏水性质。研究了喷嘴温度、反应釜温度和压力、偶联剂配比、表面粗糙度对涂层疏水性的影响。结果表明：涂层的静态水接触角可达到169.1°±0.6°;在喷嘴和釜内温度都为90℃,釜内压力为16 MPa,F-硅烷和KH-570配比为1∶1,表面粗糙度为7.3 μm时,所制得涂层具有较好的超疏水性,且具有优良的耐刮伤性。该法高效环保,涂层性能优良,适于大面积制备。     

Investigating the variations in properties of 2-pack polyurethane clear coat through separate incorporation of hydrophilic and hydrophobic nano-silica

In the present study, a 2-pack polyurethane clear coat curable at ambient conditions was selected. Two different types of nano-silica (i.e. hydrophilic and hydrophobic nano-silica) were employed as fillers in order to vary the properties of the resultant nano-composite polyurethane coatings.     

The effect of weathering and thermal treatment on the scratch recovery characteristics of clearcoats

The scratch and scratch recovery characteristics of two clearcoats, a polyurethane and an acrylic/melamine/silane clearcoat, were measured by a variety of methods. On most size scales tested, the polyurethane possessed superior scratch and mar resistance. The polyurethane also possessed improved scratch recovery after warming for 2 h at 60°C. After 2000 h of accelerated weathering, the scratch recovery characteristics of the polyurethane were largely maintained, while the acrylic/melamine/silane showed a significant drop in scratch recovery performance. Performance of both coatings was related to T _g, hardness, and crosslink density.     

Solid dispersion particles of tolbutamide prepared with fine silica particles by the spray-drying method

Solid dispersion particles of tolbutamide (TBM) were prepared by formulating nonporous (Aerosil 200 (hydrophilic), Aerosil R972 (hydrophobic)) or porous (Sylysia 350 (hydrophilic), Sylophobic 200 (hydrophobic)) silica as a carrier and applying the spray-drying (SD) or evaporation (Eva) method. In the solid dispersion particles prepared by the SD method, TBM existed in a meta-stable form (Form II) irrespective of the type of silica. On the other hand, when the Eva method was used, various crystalline forms of TBM were observed in the solid dispersion particles according to the type of silica. Polymorphs of Forms III and IV were prepared with Aerosil 200 and Aerosil R972, respectively, while crystalline Form II was obtained when either of the forms of porous silica, Sylysia 350 or Sylophobic 200, was formulated. The dissolution property of TBM in the solid dispersion particles prepared with hydrophilic silica was remarkably improved compared with those of the original TBM crystals (Form I) or spray-dried TBM without silica (Form II). In the case of hydrophobic silica, the release rate of TBM from the solid dispersion particles was much slower than that of original TBM. The meta-stable form of TBM in the solid dispersion particles was stable for at least 4 weeks when stored at 60 °C and 0% RH, while the spray-dried TBM without silica (Form II) was gradually converted to the stable form (Form I) under the same storage conditions. Under the humid storage conditions (60 °C, 75% RH), the spray-dried TBM without silica (Form II) immediately converted into the stable form (Form I) within 1 day, while TBM (Form II) in the solid dispersions in a matrix of silica was stable for at least 1 week.     

Thermal stability and abrasion resistance of polyacrylate/nano-silica hybrid coatings

Polyacrylate (PAE)/nano-silica (SiO₂) hybrids were prepared by an in situ sol–gel process of tetraethyl orthosilicate in the presence of PAE toluene solution. The hybrid coatings were fabricated using a PAE/SiO₂ suspension by the traditional casting. Their intermolecular interaction and morphology, as well as thermal, mechanical, and optical properties, were investigated using Fourier transform infrared spectroscopy, field-emission scanning electron microscope, differential scanning calorimetry and TG/DTA thermogravimetric analysis, coating impact testing, and UV–Vis spectroscopy, respectively. At the same time, their abrasive properties were carried out by abrasion resistance and nanoindentation tests. The results indicate that silica nanoparticles, with diameter about 30 nm, can disperse homogeneously in the PAE matrix, where hydrogen bonds between the PAE and nano-silica are formed. Therefore, homogeneous dispersion of nano-silica particles provides high transparency for the PAE/SiO₂ hybrid coating as the size of nano-silica phase is much smaller than the wavelength (390–770 nm) of visible light. PAE/nano-silica hybrid coatings have increased T _g and thermal stability including the onset decomposition temperature, 10 % weight loss temperature, and char at 700 °C. Additionally, the incorporation of nano-silica particles improves the glossiness of the PAE/nano-silica hybrid coatings and enhances their abrasion resistance and surface hardness. The nano-silica content has obvious effect on the thermal, mechanical, optical, and anti-abrasion properties of PAE/SiO₂ hybrid coatings. With the consideration of all the properties of hybrid coatings, the PAE/SiO₂ hybrid containing 10 phr of nano-silica has the optimal composition. These PAE/nano-silica hybrid coatings have potential applications in high-performance hologram image recording.     

水性聚氨酯/纳米SiO_2杂化材料的制备及性能研究

首先合成内交联的WPU预聚体,以KH550为偶联剂,加入亲水性的纳米SiO2(A200),通过溶胶-凝胶过程合成了一种水性聚氨酯/纳米SiO2杂化材料(WPUNS)。通过FTIR、TG、DSC、物理机械性能测试对WPUNS的结构和膜性能进行了研究,用动态激光光散射法测试了杂化乳液的粒径和粒径分布,并用TEM对乳液形貌进行了观察。红外分析表明,WPU大分子和A200之间形成了化学键,粒径和乳液形貌观察显示了PU大分子包裹A200粒子形成了复合粒子结构。当w(A200)由0增大到2%时,粒径由79.9 nm增至139.9 nm,膜的拉伸强度由6.32 MPa增加到20.46 MPa,吸水率由28.3%降低到6.3%,硬度亦相应提高。TG分析表明,A200的加入可以提高材料的耐热性。DSC表明,A200的加入使硬段Tg向高温扩展。     

The influence of nano-silica on the thermal conductivity of polyurethane foam

This study reports the influence of nano-silica particles (0.0–0.45 %wt) on properties of polyurethane foams (PUF) using monoglycerides, sorbitol, and glycerol as components of polyol. The morphology, density, mechanical, thermal stability, and thermal conductivity properties of samples were investigated in this study. When 0.35 %Wt of nano-silica was used to reinforce PUF, the compression strength of PUF achieved the highest value (82.49 kPa). The thermal gravimetric analysis showed that the presence of nano-silica can improve the thermal stability of PUF samples. Scanning electron microscopy studies indicated that PUF samples containing 0.3, 0.35, and 0.45 %Wt of nano-silica had more uniform cell structures than pure PUF sample. Finally, the thermal conductivity of pure PUF and PUF/nano-silica were measured at three different levels of humidity (33% RH, 57% RH and 75% RH) at 25°C. The lowest thermal conductivity value achieved was 0.034 W/mK.     

Preparation and characterization of polyurethane clearcoats and investigation into their antigraffiti property

A type of antigraffiti polyurethane clearcoat was prepared and characterized. Polymethylsiloxane grafted by fluorocarbon side chains (PSF) was first synthesized through hydrosilylation of polymethylhydrosiloxane with dodecafluoroheptyl acrylate. Hydroxyl fluoroacrylate resins with different hydroxyl contents were synthesized via free radical-initiated solution polymerization and further applied to prepare polyurethane clearcoats. The synthesized polymers were structurally characterized by using Fourier transform infrared and ¹H nuclear magnetic resonance. The prepared polyurethane clearcoats underwent contact angle measurement, dynamic thermal mechanical analysis, nanoscratch experiments, and atomic force microscopy. The results reveal that low surface energy, high crosslink density, low coefficient of friction, and low roughness were jointly beneficial to antigraffiti properties. Antigraffiti testing was carried out on the clearcoat with 8.0 wt% PSF and 2.0 wt% active silicone fluid, and this clearcoat showed high resistance to acrylic spray paint, permanent markers, and other graffiti materials.     

Study of the influence of nano-silica particles on the curing reactions of acrylic-melamine clear-coats

In present study, the influence of presence of nano-silica particles having different surface modifications on curing reaction of a thermosetting acrylic-melamine clear-coat is clarified.Acrylic-silica nano-composites were made by grinding and dispersing of silica nano-particles in a thermosetting acrylic resin via milling. The resulting compositions were characterized in terms of curing reaction and the final film morphology. The cure reaction of the Neat and nano-particle containing clear-coats was monitored by differential scanning calorimetry (DSC). It was found that the presence of nano-silica particles, either hydrophilic or hydrophobic, reduces the activation energy of cure and increases the total heat of reaction. The morphology of the film is also extensively influenced by the presence of nano-particles.     

Novel surfactant-free waterborne acrylic-silicone modified alkyd hybrid resin coatings containing nano-silica for the corrosion protection of carbon steel

We report a novel waterborne acrylic-silicone modified alkyd nanocomposite latex containing nano-silica prepared by the surfactant-free miniemulsion polymerization. The influences of γ-methacryloxy-propyltrimethoxysilane- (MPS-) modified nano-silica particle contents to the thermal, mechanical and anti-corrosion performance of hybrid latex coatings were studied. The results revealed that the incorporation of nano-silica particles into latex films could directly increase the thermal stability and mechanical properties. Electrochemical corrosion studies revealed that these nanocomposite coatings exhibited superior corrosion resistance performance (inhibition efficiency 99.36% and corrosion rate 1.09 × 10 ^?3 mm per year) than that of the control system (without SiO₂ NPs).     

Nano-structure phosphorus-containing polyurethane dispersions: synthesis and crosslinking with melamine formaldehyde resin

Nano-particle-size phosphated polyurethane dispersions were synthesised from phosphorus-containing macroglycol, bis (hydroxymethyl) propionic acid and methylene-bis-(4-isocyanatocyclohexane) (H₁₂MDI). After the carboxylic acid groups of the phosphated polyurethane were neutralised by suitable bases, water was added to form the phosphated polyurethane dispersion. Chain flexibility affected particle-size reduction because flexible particles are more deformable in a shear field. During phase inversion the dispersed phase can more easily be broken into smaller particles. Depending on the number of hydrophilic groups present, the dispersion can be obtained in a very finely divided form, so that it practically has the appearance of a solution.Crosslinking of the dispersions with melamine showed that hexamethoxymethyl melamine does not self-condense during the curing and co-condensation was predominant. It was further shown that the cure response of the polyurethane dispersions was affected by the nature of the neutralising amine. Triethanolamine neutralised dispersions gave very poor cure response compared with triethylamine due to the low-volatility and the tendency to enter side reaction with the melamine.     

硅烷偶联纳米SiO2改性形状记忆聚氨酯

本文采用经硅烷偶联剂表面处理的纳米SiO2粒子制备了形状记忆聚氨酯／SiO2纳米复合材料。并用SEM、DSC、TGA对其进行分析,考察其形状记忆行为及力学性能。结果表明,形状记忆聚氨酯中加入纳米SiO2后,其热稳定性能提高了,形状回复起始温度(Ti)提高约10℃,形状回复速率提高约3．8倍,而力学性能有所下降。     

原位生成纳米SiO2及其作为填料对聚氨酯硬质泡沫塑料性能的影响

通过选择适当的乳化剂和水解温度以及控制水对于乳化剂的摩尔比,采用油包水微乳液法在聚醚多元醇中原位合成了纳米SiO2,该聚醚多元醇进一步与TDI反应制备出聚氨酯硬质泡沫塑料.TEM显示原位合成的SiO2微粒呈球状且分散,粒径为50～70nm.随着SiO2填加量的增加,该聚氨酯硬质泡沫塑料的吸水率先升后降.因为原位生成纳米SiO2的加入,聚氨酯硬质泡沫塑料的拉伸强度得到显著提高,冲击强度缓慢增大,而压缩强度则先轻微降低,一直到SiO2的含量为0.9wt%时才开始急剧增大.     

Comparative Properties of Hydrophilic and Hydrophobic Fumed Silica Filled Two-Component Polyurethane Adhesives

Two fumed silicas, one hydrophilic and another hydrophobic, were added to a two-component polyurethane (PU) adhesive and their properties compared. The filled polyurethanes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and water and diiodomethane contact angle measurements. The adhesive strength was evaluated from single lap-shear tests of solvent wiped stainless steel/polyurethane adhesive joints. The fumed silicas were well-dispersed in the polyurethane matrix as bundles of nanometric spherical silica particles. However, some micron size agglomerates of fumed silica appeared in the filled polyurethane. The addition of fumed silica favoured the degree of phase separation between the hard and the soft segments in the polyurethane. The polyurethanes were not fully cured under the conditions used in this study and the addition of fumed silica inhibited the curing reaction; the extent of the curing reaction was not affected by the hydrophilic or hydrophobic nature of the fumed silica. The filled polyurethanes were further cured during DSC experiments and this was noticed by the appearance of the melting of the hard segments and the displacement of the second glass transition to a higher temperature. On the other hand, the addition of fumed silica increased the wettability and the surface energy of the polyurethane; this increase was mainly due to an increase in the polar component of the surface energy. The increase in surface energy is somewhat more marked in the case of the hydrophilic silica filled polyurethane, indicating that the polarity of the fumed silica affected the surface properties of the polyurethane. Finally, the addition of the hydrophilic fumed silica increased the adhesion of the filled polyurethane adhesive to stainless steel which was in agreement with the higher surface energy of the hydrophilic fumed silica filled polyurethane.     

Effect of nano‐silica on gas permeation properties of polyether‐based polyurethane membrane in the presence of esterified canola oil diol as a nucleation agent for hard segments

In this research esterified canola oil diol (COD) was used to synthesize a green thermoplastic polyurethane. The mixture of synthesized COD as a polyester and polytetramethylene‐glycol as a polyether with different molar ratios were used to synthesize a thermoplastic polyurethane. Membranes were prepared by solution casting technique and nano‐silica particles were used to improve their gas separation performance. The effects of COD segments on phase separation and thermal properties of blocky segments of polyurethanes were evaluated using Fourier transform infrared spectroscopy and thermal gravimetric analysis. Results showed that phase separation behavior of the synthesized polyurethane was significantly increased with COD content. The COD segments showed high tendency to interact with hard segments of polyurethane in a way that new domains with higher thermal stability is created. Permeability of pure CO₂, CH₄, N₂, and He gases were taken using constant pressure method at different pressures. Nano‐silica particles showed high inclination to interact with COD segments and significantly influenced the phase separation as well as gas permeation properties of polyurethane. Interactions of nano‐silica particles with the soft segments of polyurethane increased the glassy behavior of polymer and improved the CO₂/CH₄, CO₂/N₂, and CO₂/He ideal selectivities (permselectivities). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45979.     

Investigation of biocompatible nanosized materials for development of strong calcium phosphate bone cement: Comparison of nano-titania,nano-silicon carbide and amorphous nano-silica

The present paper deals with the effect of adding SiC, TiO₂ and SiO₂ nanoparticles on setting time, mechanical strength and hydraulic reactions of calcium phosphate cements (CPCs). The initial and final setting times of CPC increased by adding both nano-SiC and nano-TiO₂ additives but decreased by using nano-silica. Nano-titania and nano-silica had great effect on compressive strength of as-set CPC whereas slight changes were found by using nano-SiC. Although a sharp increase in compressive strength of all cements was observed by soaking them in physiological solution, the soaked additive-free cements and nano-SiO₂-added ones exhibited the greatest strength values. The results showed that adding these nano-additives did not influence on conversion rate of cement reactants to apatite phase during soaking in physiological solution period but the morphology of the formed phase was almost different. Overall, the results determined that nano-SiO₂ and nano-TiO₂ particles were appropriate additives to improve short-term mechanical strength of CPCs a(s-set CPCs), though nano-SiO₂ was found more effective because it improves the long-term mechanical strength of CPC (after soaking) too.     

Characterization of clearcoats containing phosphoric acid-functionalized acrylic polyols for automotive precoated metal sheet coatings

In this study, the various physical and mechanical properties of clearcoats prepared through a new crosslinking method were investigated. The method was aimed at developing clearcoat systems to improve the deep-draw processing and formability performance in precoated metal (PCM) sheets for automotive applications. From phosphoric acid-functionalized acrylic polyols (PAFAPs) first synthesized in this study and glycidyl methacrylate-modified acrylic copolymer (GMAMAC), phosphoric acid-GMA modified acrylic polyols (PAGMAPs) were newly prepared as new binders in automotive clearcoats. Several clearcoats were formulated with different molecular weights and hydroxyl contents from PAFAPs and GMAMAC. Using clearcoats themselves, the crosslinking reactions for these clearcoats were compared by evaluating the curing behaviors with a rigid-body pendulum test (RPT) and the changes of chemical structures via attenuated total reflectance FTIR spectroscopy. The mechanical properties of the clearcoats were systematically characterized, using dynamic mechanical analysis (DMA) and universal testing machine analysis (UTM). Also, various tests were carried out using PCM sheets by depositing clearcoats above the same PCM-based primers and basecoat layers on galvanized steel. The fracture and deformation patterns related to surface damages on the clearcoat surface were visualized using a nano-scratch test, in association with atomic force microscopy. In particular, deep-draw processing tests, based on forming process simulations, were employed to scrutinize the effect of clearcoats developed in this study on the forming feature in PCM sheets. From the results of RPT, DMA, and UTM tests, the primary crosslinking networks of PAGMAPs from the synthesized PAFAPs and GMAMAC, and also succeeding secondary crosslinking networks between PAGMAPs and blocked isocyanates, were closely correlated with the degree of crosslinking (X _c), in accordance with the molecular weight between crosslinks (M _c), and glass transition temperature (T _g). As a result, the presented clearcoats with a long pendulum period, a low rubbery modulus, and a large tensile strain value, which are the significant factors for developing automotive PCM sheet technology, have truly demonstrated more superior formability during the deep-draw process. It is confirmed that properties of clearcoats with toughness and flexibility could be optimally controlled by PAGMAPs for automotive coatings.     

Kinetics study of living microemulsion polymerization mediated by reversible addition-fragmentation chain transfer

The present work focuses on the development of functional polyurethane hybrids through the incorporation of surface modified TiO₂ nanoparticles. For improving the nano-particle dispersion and increasing possible interactions between nano-particles and polyurethane matrix, the surface of the nano-particles was modified with 1,3,5-triazine core silane coupling agent. The surface modification of nanoparticles was confirmed by FESEM, FT-IR and Raman spectroscopic techniques. The functionalized nanoparticles were then inscribed in 0, 1 and 2 weight percentages into polyurethane matrix. The as prepared composite coatings were investigated for various anti-microbial, thermo-mechanical and anticorrosive properties. The tensile strength of polyurethane was improved by 300 % upon addition of 2 wt% of modified TiO₂ nanoparticles as compared to neat polyurethane. Fog test and electrochemical polarization studies suggest that the corrosion resistance increases with increase of the modified TiO₂ content in the coating formulation. The composite coatings also have good resistance towards various bacterial and fungal stains as compared to the pure polyurethanes. The coatings substantially gain hydrophilic nature symbiotically with TiO₂ content suggesting its potential application as self-cleanable material.