Applications of Ultrafine Powder Coatings

Powder coatings have emerged as an alternative to the conventional liquid coatings when environmental regulations become stricter every year. The advantage of powder coatings mainly renders to their solvent-free formulations, because solvent(s) used in liquid coatings are to be evaporated to environment contributing to the total volatile organic compounds (VOCs) emissions. Although advantageous, until recently, powder coating was not able to provide surface finishes comparable to the liquid coatings. However, when ultrafine powders (particularly, in the size range of 15-25 µm) becomes flowable with the aid of nano-additive(s), ultrafine powder coatings (UPCs) came into business with its thinner and smoother films well-comparable to the liquid coatings. Thus UPC offers environmentally friendly alternative to the coating industries having applied to develop many functional coatings. Ultrafine powder coating (UPC) technology has been utilized to develop superhydrophobic powder coatings that mimic lotus leaf surfaces and exhibit water contact angles (CAs) of over 160° and sliding angle (SA) of less than 5° on the coated substrates. Water droplets tend to be very unstable on these surfaces so that they run away from the superhydrophobic surfaces even with the slightest inclination. This unique phenomenon is attributed to the double-scale micro-/nano hierarchical structures that have been successfully fabricated on such surfaces just by incorporating nano-sized hydrophobic additive(s) in the coating formulations. Thus the solvent-free UPC technique has offered simple but environmentally friendly solution in developing superhydrophobic surfaces that could be used as self-cleaning surfaces. Ultrafine powder coating (UPC) technique has been employed to develop polymeric biocompatible powder coatings enriched with nano-Ti02 with varying degree of nanoroughness ranging from -37 nm to -260 nm. The developed coatings have been assessed for their biocompatibility when human mesenchymal cells were cultured on them. Cells attached spread and expressed Runx2 and Collagen Type Ion these biocompati ble coatings. Interestingly, they performed even better than commercially pure titanium (cpTi) when their nanoroughness could be maintained below -50 nm. UPC has been able to tune up the nanoroughness of the developed coatings without changing anything in the existing processes, rather by changing amount of the constituents in the coating formulations. Thus UPC could possibly replace the traditional techniques (plasma treatment, sputter-coating or vapour deposition) to develop bioactive coatings for medical devices with offering simple and inexpensive coating method. Ultrafine powder coating (UPC) technique has also been used to apply flow-modified glass ionomer cement (GIC) powders onto exposed dentine surfaces to occlude exposed dentinal tubules that could effectively treat dentine hypersensitivity. Proprietary ultrafine GIC powders, (Ketac-Cem® and Fuji I® ) have been processed with appropriate amounts of nano-sized Ah03 to improve their flowability before applying them to the dentine sections by using UPC process employing Corona spraying gun. With this powder spraying technique, dentinal tubules have been occluded as deep as -1 mm µm, in some instances. Such deeper dentinal tubule occlusion renders superiority over any other existing technique (i.e., highest penetration depth was revealed in the literatures is -270 µm). Moreover, UPC technique showed a higher proportion of tubules filled. Thus, UPC could enter into the treatment of dentine hypersensitivity

Statistical and Machine Learning-Driven Optimization of Mechanical Properties in Designing Durable HDPE Nanobiocomposites

The selection of nanofillers and compatibilizing agents, and their size and concentration, are always considered to be crucial in the design of durable nanobiocomposites with maximized mechanical properties (i.e., fracture strength (FS), yield strength (YS), Young’s modulus (YM), etc). Therefore, the statistical optimization of the key design factors has become extremely important to minimize the experimental runs and the cost involved. In this study, both statistical (i.e., analysis of variance (ANOVA) and response surface methodology (RSM)) and machine learning techniques (i.e., artificial intelligence-based techniques (i.e., artificial neural network (ANN) and genetic algorithm (GA)) were used to optimize the concentrations of nanofillers and compatibilizing agents of the injection-molded HDPE nanocomposites. Initially, through ANOVA, the concentrations of TiO2 and cellulose nanocrystals (CNCs) and their combinations were found to be the major factors in improving the durability of the HDPE nanocomposites. Further, the data were modeled and predicted using RSM, ANN, and their combination with a genetic algorithm (i.e., RSM-GA and ANN-GA). Later, to minimize the risk of local optimization, an ANN-GA hybrid technique was implemented in this study to optimize multiple responses, to develop the nonlinear relationship between the factors (i.e., the concentration of TiO2 and CNCs) and responses (i.e., FS, YS, and YM), with minimum error and with regression values above 95%

Accelerated Discovery of the Polymer Blends for Cartilage Repair through Data-Mining Tools and Machine-Learning Algorithm

In designing successful cartilage substitutes, the selection of scaffold materials plays a central role, among several other important factors. In an empirical approach, the selection of the most appropriate polymer(s) for cartilage repair is an expensive and time-consuming affair, as traditionally it requires numerous trials. Moreover, it is humanly impossible to go through the huge library of literature available on the potential polymer(s) and to correlate the physical, mechanical, and biological properties that might be suitable for cartilage tissue engineering. Hence, the objective of this study is to implement an inverse design approach to predict the best polymer(s)/blend(s) for cartilage repair by using a machine-learning algorithm (i.e., multinomial logistic regression (MNLR)). Initially, a systematic bibliometric analysis on cartilage repair has been performed by using the bibliometrix package in the R program. Then, the database was created by extracting the mechanical properties of the most frequently used polymers/blends from the PoLyInfo library by using data-mining tools. Then, an MNLR algorithm was run by using the mechanical properties of the polymers, which are similar to the cartilages, as the input and the polymer(s)/blends as the predicted output. The MNLR algorithm used in this study predicts polyethylene/polyethylene-graftpoly(maleic anhydride) blend as the best candidate for cartilage repair

Novel development of biocompatible coatings for bone implants

Prolonged life expectancy also results in an increased need for high-performance orthopedic implants. It has been shown that a compromised tissue-implant interface could lead to adverse immune-responses and even the dislodging of the implant. To overcome these obstacles, our research team has been seeking ways to decrease the risk of faulty tissue-implant interfaces by improving the biocompatibility and the osteo-inductivity of conventional orthopedic implants using ultrafine particle coatings. These particles were enriched with various bioactive additives prior to coating, and the coated biomaterial surfaces exhibited significantly increased biocompatibility and osteoinductivity. Physical assessments firstly confirmed the proper incorporation of the bioactive additives after examining their surface chemical composition. Then, in vitro assays demonstrated the biocompatibility and osteo-inductivity of the coated surfaces by studying the morphology of attached cells and their mineralization abilities. In addition, by quantifying the responses, activities and gene expressions, cellular evaluations confirmed the positive effects of these polymer based bioactive coatings. Consequently, the bioactive ultrafine polymer particles demonstrated their ability in improving the biocompatibility and osteo-inductivity of conventional orthopedic implants. As a result, our research team hope to apply this technology to the field of orthopedic implants by making them more effective medical devices through decreasing the risk of implant-induced immune responses and the loosening of the implant

Nano-SiO2 Enriched Biocompatible Powder Coatings

The success/failure of implants largely depends on their osseointegration with the surrounding bone, which in turn a strong function of their biocompatibility and surface roughness. Therefore, nanoparticles of metal oxides are recently being extensively used into composites in order to enhance their topographical and biological properties. Hence, the objective of this study is to develop biocompatible polymeric powder coatings enriched with nano-SiO2 by using ultrafine powder coating technology and to grow HEPM cell on them. The coating technique involves a pre-processing of the powder mixture with the nanoparticles that ensures the homogeneous dispersion of nanoparticles into the coating ingredients. As a consequence, the presence of SiO2 nanoparticles into the polymeric materials facilitates fabrication of nano topographies onto the coated surfaces. An experimental set up was designed and executed to evaluate the adhesion/ bond strength of the coating and to measure the load bearing capacity that the coatings can withstand before being detached from the substrate. Coating\u27s topographical features and cells\u27 morphology were analyzed by using SEM

Nano-TiO2-enriched biocompatible polymeric powder coatings: Adhesion, thermal and biological characterizations

The success of orthopedic and dental implants largely depends on their biocompatibility with the surrounding body environment and the biocompatibility depends on the physical, chemical, mechanical, topographical and biological properties of the implant materials chosen. Since the last few decades, titanium and its alloys have been among the most widely used ones due to their superior biocompatibility and mechanical properties; however, pure titanium needs to be pre and/or post treated chemically or physically to maintain appropriate textures and surface roughness. In the present study, TiO2 nanoparticles incorporated polymeric powder coatings consisting of smooth and micro-nano scale roughness were developed that exhibited biocompatibility towards Human Embryonic Palatial Mesenchymal (HEPM) Cells. In addition, an experimental set up was designed and executed to evaluate the adhesion/ bond strength of the coating and to measure the load bearing capacity that the coatings can withstand before being detached from the substrate. Coating\u27s topographical features were analyzed by using Scanning Electron Microscopy (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to evaluate the thermal stability of the coating materials. © (2014) Trans Tech Publications, Switzerland

On the Injection Molding Processing Parameters of HDPE-TiO2 Nanocomposites

In recent years, the development and use of polymeric nanocomposites in creating advanced materials has expanded exponentially. A substantial amount of research has been done in order to design polymeric nanocomposites in a safe and efficient manner. In the present study, the impact of processing parameters, such as, barrel temperature, and residence time on the mechanical and thermal properties of high density polyethylene (HDPE)-TiO2 nanocomposites were investigated. Additionally, scanning electron microscopy and X-ray diffraction spectroscopy were used to analyze the dispersion, location, and phase morphology of TiO2 on the HDPE matrix. Mechanical tests revealed that tensile strength of the fabricated HDPE-TiO2 nanocomposites ranged between 22.53 and 26.30 MPa, while the Young’s modulus showed a consistent increase as the barrel temperature increased from 150 °C to 300 °C. Moreover, the thermal stability decreased as the barrel temperature increased