Preparation of Scratch and Abrasion Resistant Polymeric Nanocomposites by Monomer Grafting onto Nanoparticles, 3. Effect of Filler Particles and Grafting Agents

After modification with different trialkoxysilanes, nano‐sized silica and alumina particles were used as fillers in transparent UV/EB curable acrylates for polymer reinforcement, particularly to attain scratch and abrasion resistant coatings. The acid catalyzed condensation of the organosilanes forms a polysiloxane shell which covers the nanoparticle like a nanocapsule. CP MAS NMR spectroscopy and MALDI‐TOF mass spectrometry proved to be useful for the characterization of the polysiloxane structures. Grafted oligomers with more than 20 monomeric units were observed. Nanoparticles modified by methacroyloxy(propyl)trimethoxysilane and vinyltrimethoxysilane can copolymerize with acrylates. Compared with the pure polymers, these crosslinked polyacrylate nanocomposites, containing up to 35 wt.‐% silica, exhibit markedly improved surface mechanical properties. Promising scratch and abrasion resistance of radiation‐cured nanocomposite materials were also obtained by propyltrimethoxysilane grafting which results in an organophilation of pyrogenic silica. Both colloidal and pyrogenic nano‐sized silica nanopowders were used as fillers in polyacrylate films. The concentration of colloidal SiO₂ in commercial acrylate formulations amounts up to 50 wt.‐%, whereas pyrogenic silica, notwithstanding their surface modification by silanes, results in a thickening effect which limits its content to about 35 wt.‐%. Nevertheless, a comparison showed a distinct improvement in the surface mechanical properties such as haze and diamond microscratch hardness for surface‐modified pyrogenic silica.     

Functionalized inorganic/organic nanocomposites as new basic raw materials for adhesives and sealants

A high content of nano sized silica and alumina filler was embedded in radiation-curable acrylate formulations by acid catalyzed silylation using trialkoxysilanes. By grafting methacryloxy and vinyl functionalized silanes polymerization-active silico-organic nanoparticles were prepared. In radiation (UV,EB)-induced polymerization reactions these modified nanoparticles form covalent crosslinks to acrylate substrates, thus efficiently modifying their viscoelastic properties. To elucidate the structure of the surface-grafted methacryloxypropyl-, vinyl-, and n-propyl-trimethoxysilane ²⁹Si MAS NMR and MALDI-TOF mass spectrometry were employed. In accordance with NMR findings, MALDI-TOF MS showed highly condensed oligomeric siloxanes comprising more than 20 monomeric silane units. A ladder-like structure of bound polysiloxanes is proposed rather than a simplified picture of tridentate silane bonding. Hence, silane coupling agents do not only modify the chemical nature of the filler surface but also strongly effect the rheological properties of the acrylate nanodispersions.     

UV-waterborne polyurethane-acrylate nanocomposite coatings containing alumina and silica nanoparticles for wood: mechanical, optical, and thermal properties assessment

The effect of alumina and silica nanoparticles on mechanical, optical, and thermal properties of UV-waterborne nanocomposite coatings was investigated. The addition of nanoalumina and nanosilica was shown to decrease the hardness because of nanoparticle aggregation. In comparison to the neat coating and despite the presence of aggregates, the scratch resistance of nanocomposite coatings was significantly improved. As expected, the gloss of UV-waterborne coatings was reduced following the addition of nanoparticles due to an increase of the surface roughness. Alumina and silica nanoparticles were found to enhance the glass transition temperature of PUA nanocomposite coatings by hindering the mobility of macromolecular chains at the interface around the nanoparticles. Finally, the interest and efficiency of grafting trialkoxysilanes was demonstrated with the study of nanosilica behavior. Not only was the dispersion of nanosilica enhanced following trialkoxysilanes grafting onto silica nanoparticles, but also the scratch resistance and the adhesion of UV-waterborne coatings containing nanosilica markedly increased even with 1 wt% content. Silica which is recommended in the wooden furniture and kitchen cabinet manufacturing industry as nano-reinforcement provides improved properties well suited in surface coating applications to efficiently protect surface of wood substrates.     

Nano/Micro Particle Hybrid Composites for Scratch and Abrasion Resistant Polyacrylate Coatings

Summary: UV curable acrylate formulations with a high content of fumed, nano‐sized silica were prepared to improve their application for abrasion and scratch resistant top coats. Grafting of trialkoxysilanes onto the surface of nanoparticles facilitated their embedding in the formulation and alleviated the effect of undesired increase in viscosity and dilatancy. Modified nanoparticles were obtained from several organosilanes and characterized by a multitechnique approach. To avoid problems during redispersion, in situ modification of nano‐sized silica was performed using the liquid acrylate formulation as a diluting and deagglomerating agent. These nanocomposite materials exhibit markedly improved properties as compared to neat acrylate coatings, e.g. heat, scratch, and abrasion resistance. However, a much better abrasion resistance was obtained for coatings containing both silica nanoparticles and corundum microparticles. By using various grades of corundum, a synergetic effect of nano/micro hybrid composite materials has been studied for parquet and flooring applications.

Pictures of neat polyacrylate coating (on the left) and nano/micro hybrid composite material (18 wt.‐% silica +15 wt.‐% corundum) on parquet substrate after Taber Abraser Test.     

UV curing and matting of acrylate coatings reinforced by nano-silica and micro-corundum particles

For UV curable coatings, the effect of the type of photoinitiator and of the photoinitiator content on surface properties has been studied. Increasing photoinitiator concentrations yielded higher acrylate conversion but a lowering of surface hardness. Thus, curing under oxygen-free conditions with 2 wt.% photoinitiator should be applied rather than 6 wt.% photoinitiator for irradiation in air. Compared to nanocomposite materials, UV-cured polyacrylate coatings reinforced by silica nanoparticles and corundum microparticles exhibit markedly improved scratch and abrasion resistance. By using various grades of corundum, a synergetic effect between nano- and microparticles has been observed. These nano/micro-hybrid composite materials are recommended as clear coat for parquet and flooring applications.     

电子束固化木器清漆的制备及性能研究

电子束(EB)固化技术作为一种重要的辐射固化技术,其固化的清漆涂层性能在许多方面优于紫外(UV)光固化清漆涂层。本研究通过选取不同类型的商品化丙烯酸树脂及活性稀释剂配制木器涂料配方,分别利用电子束(EB)和紫外光(UV)对其进行固化,然后对固化后的涂层进行基本性能、热性能和机械性能的表征。研究结果表明:EB固化速度快,固化膜具有较高的铅笔硬度和附着力,而且树脂种类和单体结构的不同会对电子束固化涂层的热性能及机械性能产生影响。     

Synthesis and characterization of nanosilica/polyacrylate composite latex

The nanosilica/polyacrylate organic–inorganic composite latex was synthesized by in‐situ emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) in the presence of silica nanoparticles, which were modified by silane coupling agent. The surface properties and dispersibility of silica nanoparticles modification, chemical structure, Zeta potential, diameter distribution of the composite latex prepared, surface roughness, and thermal stability of the hybrid film formed by the composite latex were investigated by fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), Zeta meter, ZetaPlus apparatus (dynamic light scattering method), atomic force microscopy (AFM), and thermogravimetric analysis (TGA), respectively. After modification with silane coupling agent, silane was grafted onto the surface of silica nanoparticles to form the organic layers, which was able to efficiently prevent the silica nanoparticles from aggregating to individually homogeneous disperse in the in‐situ emulsion polymerization system and improve the compatibility of silica nanoparticles with the acrylate monomers. The nanosilica/polyacrylate organic–inorganic composite latex prepared had the properties of silica nanoparticles and pure polyacrylate latex but was not simply a combination. Strong chemical bonding tethered the silica and acrylate chains to form the core/shell structural composite latex. Consequently, the hybrid film formed by nanosilica/polyacrylate composite latex exhibited a smooth surface and better thermal properties than the pure polyacrylate film. POLYM. COMPOS. 27:282–288, 2006. © 2006 Society of Plastics Engineers     

Alumina and zirconia acrylate nanocomposites coatings for wood flooring: Photocalorimetric characterization

Radiation curable coatings are presently the standard in wood flooring industries, although important improvements can still be brought to these coatings. In this work, nanocomposites coatings for wood flooring were prepared from various acrylate reactives. Nanoparticles were added in the neat acrylate formulation prepared from two acrylate monomers, two acrylate oligomers, a defoaming agent and a photoinitiator. Particle size characterization was performed by a dynamic light scattering technique. Reinforcing agents and coupling agents addition effects on acrylate resin conversion were studied by photo-calorimetry (photo-DSC). For each nanocomposite sample, heat of reaction and induction time were determined from exotherms and these datas were used to study the effects of reinforcing agents and coupling agents on curing kinetics of radiation curable nanocomposite coatings. Photo-DSC studies show that nanoparticles and coupling agent clearly affect coatings polymerization. In fact, zirconia nanoparticles tend to decrease polymerization. Alumina nanoparticles do not affect negatively curing coatings. Silane coupling agent affects positively the curing of acrylate coatings, although zirconate coupling agent tends to decrease it.     

UV-cured polymer-boehmite nanocomposite as protective coating for wood elements

An organo-modified Boehmite (OMB) was used to prepare nanocomposite UV-cured coatings, based on an innovative photopolymerizable siloxane-modified acrylic formulation, for possible use as protective coatings. 3 wt.% of the nanofiller was dispersed into the mixture in the presence of a proper photoinitiator for UV curing. Different amounts of a silane coupling agent were added to the mixture in order to enhance the compatibility between the nanofiller and the siloxane-modified acrylic formulation. The kinetics of the radical photopolymerization reaction, induced by UV radiations, was studied by photo-calorimetric analysis. The rheological behaviour of the formulations produced was studied as function of the shear rate using a plate and plate rheometer. The formulations, coated on a glass substrate, were photo-cured by using a medium pressure Hg UV lamp. On the coatings photo-polymerized in air were measured: gel content, transparency, scratch and surface hardness. The water absorption effect of the coating based on the novel organic photo-curable nanocomposite on walnut wood elements was evaluated.     

The utilization of specific interactions to enhance the mechanical properties of polysiloxane coatings

Moisture-curable polysiloxanes were modified with ionic groups to enable specific interactions between the polysiloxane matrix and silica nanoparticle reinforcement. A trimethoxysilane-functional quaternary ammonium salt (QAS) was used to modify the polysiloxane matrix. A comparison of the mechanical properties of coatings containing QAS modification to analogous coatings without QAS modification showed that QAS modification resulted in a dramatic improvement in mechanical properties of silica nanoparticle-reinforced coatings. QAS modification provided major enhancements in both tensile modulus and toughness. The coatings were characterized using positron annihilation spectroscopy, photo-acoustic FT-IR, differential scanning calorimetry, transmission electron microscope, and atomic force microscopy. The characterization results suggested that the QAS moieties present in the polysiloxane matrix undergo specific interactions with the surface of silica nanoparticles enabling an enhancement in interfacial adhesion between the polymer matrix and the nanoparticles. Most likely, the specific interaction that provided the enhanced mechanical properties was an ion–dipole interaction involving silanol groups present on the surface of the silica nanoparticles. The enhanced modulus and toughness of these polysiloxane materials may enable their application as a fouling-release coating for ship hulls, since current polysiloxane-based fouling release coatings suffer from poor mechanical properties and durability.     

PDMS乳液/硅溶胶杂化水分散体系及其复合膜的制备与表征

以聚硅氧烷(PDMS)乳液/硅溶胶杂化水分散液为成膜基质,硅烷偶联剂KH 550为固化剂,制备了双组分水基有机硅涂料;将其固化后得到PDMS/硅溶胶复合膜。通过水分散液的粒径分布及红外光谱分析,研究了水分散液的脱水成膜过程;采用扫描电镜(SEM)和原子力显微镜(AFM)对复合膜的断面和表面形态进行了表征。结果表明:PDMS乳液加入硅溶胶后,粒径分布变宽,粒径略有增加;成膜后,硅溶胶粒子与PDMS长链发生了相互作用,并作为分散相被包埋在PDMS中;复合膜表面形成簇状结构,表面粗糙度随着硅溶胶含量的增加而增加。当硅溶胶与PDMS乳液的固体质量比由10%增加到30%时,复合膜的拉伸强度由0.76MPa升高到3.10MPa,而拉断伸长率从680%下降到470%。     

含硅聚氨酯预聚体改性聚丙烯酸酯清漆的制备与研究

采用端羟基聚硅氧烷、功能单体与异佛尔酮二异氰酸酯缩聚制备新型含硅聚氨酯预聚体(Si-PU),Si-PU与丙烯酸酯单体共聚,得到Si-PU改性聚丙烯酸酯。以改性聚丙烯酸酯为成膜物质,以异氰酸酯基树脂为固化剂按基团等物质的量比配制成双组分清漆,并制备涂膜。采用FT-IR对改性前后聚丙烯酸酯结构进行了表征。研究了Si-PU用量对聚丙烯酸酯清漆的黏度、耐热性、附着力及其涂膜绝缘性的影响。FT-IR表明,Si-PU已经接枝到了丙烯酸酯共聚物的骨架中。Si-PU质量分数在0～15%,涂膜的附着力不变,且Si-PU用量为聚丙烯酸酯的15%时,得到综合性能良好的含硅聚氨酯改性聚丙烯酸酯清漆。     

Nylon 11/silica nanocomposite coatings applied by the HVOF process. II. Mechanical and barrier properties

Nylon 11 coatings filled with nominal 0–15 vol % of nanosized silica or carbon black were produced using the high velocity oxy‐fuel combustion spray process. The scratch and sliding wear resistance, mechanical, and barrier properties of nanocomposite coatings were measured. The effect of powder initial size, filler content, filler chemistry, coating microstructure, and morphology were evaluated. Improvements of up to 35% in scratch and 67% in wear resistance were obtained for coatings with nominal 15 vol % contents of hydrophobic silica or carbon black, respectively, relative to unfilled coatings. This increase appeared to be primarily attributable to filler addition and increased matrix crystallinity. Particle surface chemistry, distribution, and dispersion also contributed to the differences in coating scratch and wear performance. Reinforcement of the polymer matrix resulted in increases of up to 205% in the glass storage modulus of nanocomposite coatings. This increase was shown to be a function of both the surface chemistry and amount of reinforcement. The storage modulus of nanocomposite coatings at temperatures above the glass transition temperature was higher than that of unfilled coatings by up to 195%, depending primarily on the particle size of the starting polymer powder. Results also showed that the water vapor transmission rate through nanoreinforced coatings decreased by up to 50% compared with pure polymer coatings. The aqueous permeability of coatings produced from smaller particle size polymers (D‐30) was lower than the permeability of coatings produced from larger particles because of the lower porosities and higher densities achieved in D‐30 coatings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2272–2289, 2000     

有机硅树脂及涂料研究的一些新进展

介绍了环脂基取代、官能基化的新型聚硅氧烷树脂的合成过程及在光固化、脱模、有机-无机纳米复合涂料、氨基-环氧体系涂料中的潜在应用;对硅氧烷-丙烯酸及有机改性剂改性的杂化水分散体的性能表征作了介绍。     

高耐候性聚硅氧烷涂料的研制

以高硅含量、高固低黏的改性聚硅氧烷树脂为基础,制备了聚硅氧烷涂料,并用氨基硅烷固化,制得改性聚硅氧烷涂层。考察了氨基硅烷固化剂用量和种类对聚硅氧烷涂层老化失光和变色行为的影响规律。研究结果表明:在改性聚硅氧烷树脂固定不变的情况下,可通过固化剂的种类和用量调节聚硅氧烷涂料的耐老化性。聚硅氧烷涂料具有远优于聚氨酯涂料的耐老化性和耐盐雾性,可作为氟碳面漆的理想替代品。     

Behavior of epoxy resin filled with nano-SiO2 treated with a Eugenol epoxy silane

Harvesting biobased silane coupling agent to enhance the connection between fillers and epoxy matrix is vital to achieve sustainable and environmentally friendly products. In this work, a eugenol based epoxy silane-coupling agent with high purity was prepared and used for the surface modification of nano-sized silica particles. The surface structure composition and physical properties of the modified nano-SiO₂ were characterized through nuclear magnetic resonance, Fourier transferred infrared spectrometer, X-ray photoelectron spectroscopy, and thermal gravimetric analyzer. An epoxy nanocomposite was subsequently prepared by incorporating the resulting modified nano-SiO₂ as an enhancing filler. The nanocomposites glass transition temperature, the morphology of fracture surface, dynamic mechanical properties, and thermostability were investigated. Results showed that the eugenol epoxy silane-coupling agent bearing a long chain structure of benzene ring in the molecular structure could improve the compatibility of silica fillers with epoxy resin and contribute to a better dispersion state in the matrix, thus enhancing the overall performance of epoxy-cured products.     

Oligosilazane cured by moisture as fluorine-free hydrophobic coating for waterproof polymer-matrix composite materials

Preceramic oligosilazane was applied as a waterproof hydrophobic surface coating for electromagnetic wave-transmitting material (silica cloth-reinforced bismaleimide laminated composite). Oligosilazane spread readily on the surface of the material, due to its good wetting ability, enabling formation of silazane coatings using various processing methods such as spraying, dipping, wiping, etc. When using oligosilazane containing micrometer-sized silica particles as filler, a hydrophobic surface was realized after moisture curing under ambient condition. The hydrophobic surface with oligosilazane coating inhibited water absorption shows promise for application as a waterproof surface coating of electromagnetic wave-transmitting materials.     

Influence of polymer–filler interactions on retraction behaviors of natural rubber vulcanizates reinforced with silica and carbon black

In general, silica‐filled rubber compounds contain a silane coupling agent to improve the filler dispersion and polymer–filler interactions. The silane coupling agent modifies the silica surface and makes crosslinks between the rubber and the silica. Influence of the modification of silica on the retraction behaviors of natural rubber (NR) vulcanizates reinforced with silica and carbon black was studied. Variation of the retraction behaviors of NR vulcanizates with filler composition was also investigated. The vulcanizates containing the silane coupling agent were recovered faster than those without the silane coupling agent. The recovery difference between the vulcanizates without and with the silane coupling agent increased with increased silica content. For the vulcanizates containing the silane coupling agent, the retraction behaviors were nearly the same, irrespective of filler composition. But, for the vulcanizates without the silane coupling agent, the vulcanizate was recovered more and more slowly as the silica content increased. The experimental results are explained with the polymer–filler interactions, modification of silica surface, and formation of crosslinks between silica and rubber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 691–696, 2006     

Development of Scratch- and Abrasion-Resistant Coating Materials Based on Nanoparticles,Cured by Radiation

The aim of this study was to compare the effect of monomers, prepolymers, and nanosilica on the scratch and abrasion resistance of nanocomposite coatings. Ultraviolet (UV) and electron beam (EB) curing were used to cure the nanocomposite coatings. The effect of monomers, prepolymers and nanosilica particles on the viscosity, pendulum hardness, gel content, scratch and abrasion resistance were studied. It was found that the optimum formulation for scratch and abrasion resistance contained 15% Ebecryl 600 epoxy acrylate resin with 30% monomer PETIA and 30% of Aerosil OX-50 nanosilica.     

环保型木器涂料

介绍水性和紫外光固化两类环保型木器涂料及其研究进展。水性木器涂料主要为丙烯酸酯与聚氨酯两大类，其研究进展集中表现为乳液改性，包括自交联、共混共聚、微乳液等；紫外光固化木器涂料包括其光固化树脂、活性稀释剂和光引发剂的功能及进展；指出研究新型乳液以提高水性木器涂料涂膜的表面性能，开发新型原材料以降低紫外光固化木器涂料的成本、扩大适应范围将成为今后环保型木器涂料的研究重点。