Modifications of paper and paperboard surfaces with a nanostructured polymer coating

Organic nanoparticles synthesized by imidization of styrene-maleic anhydride copolymers are deposited as a top-coating onto paper and paperboard substrates from a stable aqueous dispersion with maximum solid content of 35 wt.%. The morphology, physical characteristics and chemical surface properties of the coatings are discussed in this paper, using scanning electron microscopy, atomic force microscopy, contact angle measurements and Raman spectroscopy. Due to the high glass transition temperature of the polymer nanoparticles, a unique micro- to nanoscale structured coating is formed that favourably improves the gloss, printing properties (ink-jet printing test and off-set printing test), surface hydrophobicity (maximum water contact angle 140°) and water repellence (reduction of Cobb-values). The interaction of the nanoparticle coatings with the cellulosic paper web results in improvement of the mechanical paper strength and is attributed to hydrogen-bonding between the nanoparticles and the cellulosic fibers.     

Preparation of a hydrophobic cerium oxide nanoparticle coating with polymer binder via a facile solution route

In this work, cerium oxide (CeO₂) nanoparticles (NPs) were synthesized using a facile, low temperature solution process and coated using spin coating and spray coating approaches, for the fabrication of a hydrophobic surface coating. Silicon wafer (Si) substrates coated with CeO₂ NPs exhibited excellent hydrophobic behavior, but poor adhesion of the NPs to the substrate was observed - likely due to the low surface polarity of CeO₂ NPs. Polyacrylic acid (PAA) was introduced as an adhesion promoter to improve NP surface characteristics and obtain an adherent and cohesive coating. Slight polarity tuning and binder inclusion significantly enhanced the binding capability of the NPs as determined by peel-off measurements. The superior mechanical properties of NP coatings were attributed to the incorporation of PAA in the polymeric network. It improves inter-particle and particle-substrate secondary interactions, ultimately aiding NP cohesion and adhesion when deposited onto the Si substrate. The adhesive and hydrophobic properties of CeO₂ NP coatings were maintained upon exposure to high temperatures, and the coatings are transparent as well, making them suitable for various applications, such as cookware, glass coating and technology components.     

Synthesis of poly(styrene-co-maleimide) and poly(octadecene-co-maleimide) nanoparticles and their utilization in paper coating

Aqueous polymer dispersions comprising of poly(styrene-co-maleimide) (SMI) or poly(octadecene-co-maleimide) (OMI) nanoparticles were synthesized by thermal imidization of the corresponding maleic anhydride copolymer precursors with ammonia using an organic solvent free process. Different reaction parameters such as temperature, time, agitation speed and stirrer geometry, and molar ratio of ammonia-to-anhydride were investigated in order to find optimal conditions. The obtained copolymer nanoparticles exhibited glass transition temperatures (T_g's) between 140 and 170 °C with particle sizes ranging from 50 to 230 nm. The compositional analysis was conducted by recording ¹H NMR and ATR-FTIR spectra. In addition, SMI dispersions were successfully spray dried and analyzed by SEM. Finally, the polymer dispersion's utility as auxiliary organic pigment in paper coating formulations was evaluated.     

Preparation and characterisation of α-methylstyrene–butadiene latexes for paper coating applications

The purpose of this work is to demonstrate how α-methylstyrene (AMS) can replace styrene in preparing styrene–butadiene (SB) type latexes and to compare the properties of the paper coating of the prepared α-methylstyrene–butadiene emulsion with the commercial styrene–butadiene latex reference sample. A lot of work is nowadays being conducted on different biorefinery concepts replacing fossil oil with biomass based raw materials due to the expected rise of the fossil oil cost. Aromatics can in principle be produced from renewable raw materials, such as lignin, sugars and terpenes for example. The potential methods include thermochemical conversions, catalytic fast pyrolysis, metabolic engineering, catalytic aromatisation and dehydrogenation among others. Terpenes, such as α-limonene and pinene, are possible sources of aromatics, and they can indeed be catalytically converted to p-cymene. Industrial hydrodealkylation and disproportionation processes developed by major petrochemical companies can further convert p-cymene to BTX aromatics or simultaneously dehydrogenate the alkyl chain of p-cymene to styrenic monomers such as α-methylstyrene. Based on the measured paper properties for uncalendered and calendered coated samples, AMS proved to be adequate to replace the oil based styrene in commercial reference SB latexes. Even though the emulsion polymerisation for the α-methylstyrene–butadiene latex was not optimised, almost all tested properties were at least equally good as in the commercial reference sample. α-Methylstyrene containing coating colours had slightly higher viscosity than the other coating colours. Coating colours containing α-methylstyrene seems to have an improved water retention compared to the commercial reference styrene–butadiene latex coating colour and the laboratory prepared styrene–butadiene coating colour. The paper coated with the commercial reference latex containing coating colour was less porous than the other coated papers. Despite of that, both dry and wet surface strength were at least equally good as in the case of the commercial reference latex. The results are promising when thinking of the future development of the bio-based latexes.     

Hybrid coating pigments of poly(styrene-co-maleimide)/kaolin/alumina trihydrate for paper coating

Novel organic–inorganic hybrid pigments were prepared by in situ imidization of poly(styrene-co-maleic anhydride) (SMA) aqueous dispersion with ammonia in the presence of inorganic pigments, i.e. kaolin (K) or a mixture of kaolin (K)/alumina trihydrate (ATH). The objective was to allow the organic nano-particles of poly(styrene-co-maleimide) (SMI) to precipitate during their formation onto the surface of the inorganic pigment(s) and to investigate their potential in paper coatings. The produced hybrid pigments were characterized by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT-FTIR), scanning electron microscopy (SEM), wide-angel X-ray diffraction (WXRD) spectroscopy and their particle sizes were determined by dynamic light scattering technique. By FTIR measurements the formation of maleimide was confirmed and the existence of strong hydrogen bonding between organic and inorganic components could also be detected. Whereas, the SEM images revealed that the surface of silicate layers had successfully been to a large extent covered by the organic nano-particles to give raise to novel hybrid particles. In addition, the particle size measurements support the observation that the organic nanoparticles for the most part had been chemically or physically attached to the larger inorganic particles. Thus, this in situ imidization process in the presence of clay particles provides a neat method of dispersing the formed nanoparticles onto the inorganic surface through hydrogen bonding. The produced hybrids were applied as auxiliary pigments in paper coating where they improved gloss without roughening the paper surface.     

Adhesion phenomena in (co)extrusion coating of paper and paperboard

In extrusion coating, the inadequate adhesion between the polymer coating and the fiber-based paper substrate (paper and paperboard) is both a common and a constant problem. The lack of adhesion between the printing ink, or glue, and the polymer coating is another area where adhesion improvement is needed. The common means of improving adhesion are flame, corona, and ozone treatments. A modem extrusion coating line is equipped with both a pretreatment and a post-treatment unit. From the work presented here, the following observations were made. The higher the applied corona power and the thicker the coating, the higher the surface energy and polarity of the low density polyethylene (PE-LD) surface. When a high corona power was applied to the coating, only the polar component of the surface energy was increased. The surface energy decreased sharply as a function of aging, but remained more or less constant after about 2 weeks' storage time. The contact angles of water on paper correlated well with the oxygen contents (determined by ESCA) and with the applied corona power. The polarities of both paper and paperboard increased as a function of the applied corona power. Corona pretreatment of paper and paperboard improved their adhesion to PE-LD remarkably. The adhesion of the polypropylene (PP) homopolymer is based more on mechanical interlocking than on interfacial bonding. On the other hand, the oxidizing pretreatments of the paper substrates significantly promoted the adhesion of the PP copolymer.     

Paper coating performance of hemicellulose-rich natural polymer from distiller's grains

Coatings contribute to about 10% of the overall cost of paper production of which, the binder is the highest cost component in the formulation. In addition to costs, the binders that are currently being used are synthesized from fossil fuel feedstock raising concerns towards the sustainability of paper coatings. Furthermore, papers coated with waxes, polyolefins and other synthetic materials are difficult to recycle or compost. These challenges inherent with synthetic binders can be addressed by using renewable, plant based binders. This research focused on an abundant and underutilized source of hemicellulose based binders (DG gum) that can be extracted from distiller's dried grains. The extracted binder was compared with polyvinyl alcohol (PVA) in a coating formulation consisting of 10:1 CaCO₃ to binder formulation coated on light weight paper. Cobb test, dry and wet tensile tests, optical properties (brightness, color, opacity), water vapor transmission rate (WVTR) analysis were performed to compare the hemicellulose based binder with PVA. The results indicate water absorptivity reduction by 25% for both DG gum and PVA coatings from the base paper value. Dry tensile index was lower with higher coating weights for both coatings with similar performance. The performance on WVTR analysis for both coatings was also comparable. No significant differences in optical properties after coating were observed from that of the base paper. These results suggest that hemicellulose based binder extracted from distiller's grains has the potential to replace synthetic binders in paper coating formulations.     

Enhanced anti-graffiti or adhesion properties of polymers using versatile combination of fluorination and polymer grafting

Commonly used polymers and polymer articles have some advantages, e.g. low. But very often they have not very good adhesion, barrier properties, low conductivity, etc. Specialty polymers possessing necessary properties, e.g. fluoropolymers, can be used to fabricate polymer articles. However, practical use of specially synthesized polymers is restricted due to their high cost and complexity of synthesis. It is possible to coat a polymer with another polymer layer with necessary properties but this co-extrusion method is difficult to apply due to a complexity of applied equipment. Also the problems of adhesion between two polymers and polymers compatibility are to be solved. Very often application properties of polymer goods (adhesion, barrier properties, conductivity, etc.) are defined mainly by their surface properties. Hence, it is not necessary to fabricate articles from specialty polymers but simpler, cheaper, and more convenient to apply a surface treatment of articles made from commonly used relatively cheap polymers. In this case, only thin surface layer several nm to several μm in thickness is to be modified and direct fluorination (treatment with mixture of F₂ and other gases) can be effectively used. For our research we have chosen common widely used polymers. We targeted to improve hydrophobicity/hydrophylicity, adhesion properties and surface conductivity of polymers. For the first time modification of the surface of high density (HDPE), low density (LDPE) and ultrahigh molecular weight polyethylene (UHMWPE), polypropylene (PP), polyethylene terephthalate (PET) and polyvinylchloride (PVC) was performed by direct fluorination followed by a grafting of acrylic acid, styrene, acrylonitrile, vinylidene chloride, aniline and thiophene from the gas phase. Aniline grafting was studied to improve surface conductivity of polymers. Grafting of polymers was confirmed by ATR and MATR FTIR spectroscopy and energy-dispersive X-ray microprobe spectroscopy (cartography). AFM was used to study polymers surface. Influence of the nature of grafted monomers on the surface energy was studied. It was shown that depending on the nature of a grafted monomer hydrophobicity or hydrophilicity can be markedly improved. The hydrophobicity of modified polymers is not changed and is even improved with time contrary to virgin polymers. For the case of PP and UHMWPE grafting of styrene and acrylonitrile improved anti-graffiti properties (graffiti and pollutions from the polymer surface can be easier removed). For the case of HDPE and LDPE grafting of styrene and acrylonitrile improved printability. Grafting of aniline did not improved electrical conductivity. The uniformity of grafted polymers distribution was investigated by energy-dispersive X-ray microprobe spectroscopy (cartography) for the first time.     

Compressibility of porous TiO2 nanoparticle coating on paperboard

Compressibility of liquid flame spray-deposited porous TiO₂ nanoparticle coating was studied on paperboard samples using a traditional calendering technique in which the paperboard is compressed between a metal and polymer roll. Surface superhydrophobicity is lost due to a smoothening effect when the number of successive calendering cycles is increased. Field emission scanning electron microscope surface and cross‒sectional images support the atomic force microscope roughness analysis that shows a significant compressibility of the deposited TiO₂ nanoparticle coating with decrease in the surface roughness and nanoscale porosity under external pressure.

PACS

61.46.-w; 68.08.Bc; 81.07.-b     

Estimation of the effective particle sizes within a paper coating layer using a void network model

A range of calcium carbonate-based tablets and paper coating layers, with latex or starch as binder, were prepared. Their dry porous structures were analysed by mercury porosimetry. Some of these samples were also examined by electron microscopy. The porous space of these structures has been simulated using a network model named Pore-Cor, which creates network structures with percolation behaviour and porosity matching those of the experimental sample. Representative particles were grown between the cubic pores and cylindrical throats of the void network model until they touched up to four of the adjacent void features. The sizes of these representative particles, or skeletal elements, have been previously shown to be realistic for the case of unconsolidated sand and glass beads. The size distributions of these skeletal elements were compared with each other and with experiment using a Mann-Whitney test. The sizes of the skeletal elements were found to increase with the particle size of the calcium carbonate powder. The properties of the binders, used in the paper coating formulations, were found to have a major influence on the sizes of the skeletal elements, whose sizes also increased with coating thickness. These findings give insights into the wet structure and the drying process of paper coatings.     

Solventless coupling of perfluoroalkylchlorosilanes to atmospheric plasma activated polymer surfaces

Perfluoroalkylchlorosilanes are found to readily undergo surface coupling reactions with atmospheric pressure dielectric-barrier discharge activated polymer substrates to yield hydrophobic/oleophobic surfaces. Trichlorosilane variants give rise to much better levels of surface functionalization compared to their monochlorosilane analogues.     

Studying dispersion quality of nanoparticles into a bio-based coating

The aim of this study was to improve performance of a vegetable oil-based coating with addition of nanoparticles. Uniform distribution of added nanoclay, nanosilica and nanoalumina is the key to ensure the increased abrasion resistance. A high speed mixer, bead mill and ultrasonic mixer were used to disperse the nanoparticles into coatings. The quality of nanoparticle dispersion in liquid coating was studied by dynamic light scattering (DLS), and in dry film by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Using a high-speed mixer with addition of glass beads resulted in exceptional dispersion of nanoparticles in coating as confirmed by the above techniques. Although, addition of nanoclay had a positive effect on drying time of coating (reducing it by 37%), it had negative effects on viscosity (increasing it by 5 times). Overall, addition of 1% nanoparticles significantly increased the abrasion resistance of modified coating after 2000 abrasion cycles in comparison with pure unmodified coatings as applied on larch wood flooring samples.     

纸塑复合包装材料纸中化学物迁移预测模型

基于一维Fick扩散理论,考虑了纸和塑料涂层界面处的分配系数及纸和塑料涂层中不同的扩散系数,建立了迁移预测模型,得到了其解析解。分析了各参数如分配系数、扩散系数、纸中化学污染物初始浓度和量纲1时间对迁移行为的影响。结果表明,随纸塑界面处分配系数k_CP的增大,从纸中迁移入功能阻隔层塑料中的化学污染物量和通过功能阻隔层塑料迁移进入食品中的化学污染物量明显增多;塑料中扩散系数D_C的变化显著影响了塑料和食品中化学污染物的量,而纸中扩散系数D_P的改变对迁移的影响不显著。     

A microwave‐assisted process for coating polymer and glass surfaces with semiconducting ZnO submicron particles

A new method for coating glass slides with ZnO particles with an average size of 200 nm is proposed in the current article. The coating was performed under microwave radiation. Two main morphologies are found for the ZnO crystals that are deposited on glass slides. The first morphology is that of a very dense coating of ZnO hexagonal rods growing perpendicular to the glass surface. The second is the growth of ZnO flower‐like particles. In addition to coating the glass by ZnO particles, we also report on coating other polymers [poly(methyl methacrylate) plate, polycarbonate beads, Nylon 6,6 beads, and polypropylene beads) by ZnO. The morphology obtained for ZnO coated on polymers is different from that detected for coating ZnO on glass. The unorganized coating of ZnO rods on polymers has been observed. The coated glass slides were characterized by X‐ray diffraction, volumetric titration, EDS, scanning electron microscope, and optical measurements (DRS and transmittance spectroscopy). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

节能防腐钛纳米聚合物涂料的应用与涂装

介绍了钛纳米聚合物涂料在炼油厂油汽冷却器管束上的应用状况.分析表明,与未经防护的碳钢水冷却器相比,使用钛纳米聚合物涂层的冷却器管束,可节约资金16.3万元/(台·年);与采用7910涂料的冷却器管束相比,可节约资金12万元/(台·年).经国家有关部门鉴定,该项技术在我国水冷器和冷凝器管束防腐防垢技术方面,达到了国内领先水平.     

Simulation of the consolidation of paper coating structures: probabilistic versus deterministic models

Two categories of mathematical models were compared for the simulation of consolidation of paper coating structures, that is for the packing of pigments on a paper substrate under dewatering conditions. The first category uses probabilistic methods, relying on a random number generator to either determine the initial position of the pigments or their motion. The second category uses deterministic methods based on force balances. In this work, two probabilistic models and two deterministic models are described and their respective advantages and drawbacks are critically reviewed. Simulation results obtained using three of these methods are compared for the case of monodisperse and bidisperse spherical suspensions. Porosity calculations of the numerical packings obtained with the (deterministic) discrete element method (DEM) and two probabilistic methods, the Monte-Carlo (MCD) and the steepest descent (SDD) deposition methods, are compared with experimental data from the literature. These calculations reveal significant differences in the pore volume obtained with these three models. An analysis based on the bridging and relaxation phenomena that prevail in the flow of such particulate systems provide an explanation for these differences and show the strong potential of the discrete element method.

The choice of the simulation method depends on the objective of the simulations. DEM will provide more accurate predictions of macroscopic quantities such as the porosity or the roughness, but requires very long computational times. MCD or SDD will only provide qualitative trends, but is computationally far less intense. A combination of strategies might be appropriate, using MCD (or SDD) to provide guidelines and DEM to enhance the results predicted by MCD.     

Influence of the size of spraying powders on the microstructure and corrosion resistance of Fe-based amorphous coating

The Fe-based amorphous coatings with the composition of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ were successfully sprayed on mild steel substrate by the high velocity oxygen fuel (HVOF) spraying process with different feedstock powder sizes (i.e., powder A: −33 + 20 μm, powder B: −45 + 33 μm, powder C: −55 + 45 μm). The coatings were characterized for its morphology, microstructure and thermal stability by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion behavior of the coatings in 3.5 wt% NaCl solution was studied with potentiodynamic and potentiostatic polarization test. It was found that the particle size of the feedstock powders had a significant influence on microstructure and corrosion resistance of the resultant coatings. The coatings sprayed with the finest powders show the most compact structure; while the coating with the coarser powders exhibits a better corrosion resistance. It is found that the corrosion resistance of the coatings is closely related to the wetting behavior which is affected by the oxygen content and the roughness of coatings. The coatings with hydrophobicity exhibit a better corrosion. The present result demonstrates that the amorphous coatings with hydrophobicity and excellent corrosion resistant are promising for industrial application in marine environment.     

Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

Spin and dip coating of light-emitting polymer solutions: Matching experiment with modelling

This paper reports experimental observations on spin and dip coating of light-emitting polymer (LEP) solutions where both the process conditions as well as the solution properties are factors influencing thickness and uniformity of thin LEP films. In terms of spin coating, which is a typical process for the manufacture of polymer light-emitting diodes (PLEDs), a number of process variables including spin speed were systematically explored. A matching series of dip-coating experiments was also carried out with the retraction speed as a primary variable. Modifications of existing models for both spin and dip coating were developed to include solvent evaporation and the effect of solution viscosity change during evaporation. Both models were found to give reasonable agreement with the major observed trends for final film thickness as a function of process conditions tested in this paper.     

Rheological behavior of polymer solutions during fabric coating

The overall performance of coated products is determined by the intrinsic material properties in solution and processing conditions. To characterize the behavior of these materials, the viscosity of polymers in solution at various concentrations was measured and the experimental data were fitted with the Carreau model. The results describe the rheological behavior of coating materials, and provide a basis for the modeling of polymer flow during the coating process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008