Polysaccharoid coatings are sprayed with hydrophobic polyols

China Coatings Online News News: Since it was developed by researchers at Textaco Chemical in the mid-1980s, the spraying of polypropyl coatings has gained widespread recognition in the coatings market. Compared to other coating alternative technologies, such as epoxy and acrylic, spraying polypropylene is unique because of its application performance under extreme conditions. These properties include rapid curing and use, low temperature curing (below 0 degrees C), insensitive moisture, low VOC content and excellent physical and mechanical properties. Together with improvements in construction equipment, these features have driven polysaccharina to become a leading technology in related fields such as secondary sealing, corrosion protection, waterproof film and tank lining.
polyphosphonate coating chemistry can be divided into two parts: (1) pure polypropyl, and (2) hybrid polycean, both of which are chemical reactions based on isocyanate curing. Pure polyester coatings are the result of a step-by-step reaction between pre-polymers at the isocyanate seal and curing mixtures containing only endamine-based resins and chain-expanding agents. On the other hand, hybridized polycean is a product of pre-polymer at the isocyanate sealing end, reacting with cured mixtures containing hydroxy and endamine-based resins and chain-expanding agents. Although few differences in the final physical and mechanical properties of pure polycetalyc and hybrid polysaccharides have been observed, the addition of hydroxyl-containing resins to the hybrid polysaccharides requires the addition of catalysts to maintain the same level of reaction activity as pure polysaccharides. Due to the competitive reaction between water and end hydroxyl resins and reactive isocyanate groups, hybrid polythione becomes sensitive to moisture and bubbles are formed when high levels of moisture are present.
and pure polypropyl chemical process has been occupying the main market for spray polypropyl, but recently developed hybrid polypropyle spray coating has become a new hot spot. Formulaters are taking advantage of the performance benefits of hybrid polysaccharides to improve some of the properties of polysaccharide coatings. These properties include mechanical properties, heat resistance, and chemical resistance. The availability of endamine-based resins, such as polyetheramines, is limited in design, and end hydroxy resins (e.g. polyols) have a wide range of variability. These polyols can vary in the structure of the main chain, relative molecular mass, and ability groups. These features allow the development of high-performance hybrid polysaccharide coatings whose performance levels cannot be achieved using typical pure polysaccharide techniques. For example, a recently published article shows that polyester polyols can improve the hydrocarbon-resistant solvent properties of polyurethane by adding polyester polyols to the polymer main chain2. By introducing polyester polyols into the formulation, the authors were able to develop coatings with excellent xylene resistance, an aggressive chemical commonly encountered in the oil and gas industry, which can be used in secondary sealing and container linings.
we recently introduced a new hydrophobic VORAPEL ™ polyol 3. These polyols have been used to make cast polyurethane elastomers that exhibit excellent moisture resistance and good water-soluble acid resistance (e.g. 10% hydrochloric acid and 30% sulphuric acid). As water-soluble acids are increasingly used in sewage treatment, chemical treatment, iron and steel pickles, oil and gas recovery, we are expanding the utility of these hydrophobic polyols by developing hybrid polysaccharide spray coatings. When applied to reinforced concrete, this material provides a coating with good mechanical properties, good adhesion and resistance to high concentrations of acids.
test
the pre-esters are synthesized in a 15-litre glass reactor equipped with a thermometer, a top agitator, a nitrogen inlet and outlet for continuous nitrogen flow. In the first step, polyols are added to the reactor, with a few drops of benzoyl chloride, and heated to a temperature of 50 degrees C. Once the polyols are balanced, liquid medylene isocyanate (MDI) is added to the reactor in two parts within 1 hour. After adding each equal serving of isocyanate, the temperature of the reactor should be carefully monitored to ensure that the temperature does not rise due to the heating reaction between polyols and isocyanate. After adding the last part of isocyanate, heat the reactor to 70 degrees C and hold it at this temperature for 3 hours. The reactor is then cooled to 50 degrees C to prevent thermal burns and the prejudging is packed and stored in a clean, dry metal tank. Pre-dests prepared in this way have a shelf life of up to six months.
mixtures used to cure pre-polymers are prepared by adding raw materials directly to a clean, dry metal tank. Although there is no mandatory specific order of addition, in this case the order in which raw materials are added is added according to the mass concentration in the formula from the lowest to the highest. If the catalyst is used, the catalyst should be carefully weighed on the analytical balance and diluted with a resin mixture of 40 to 50 grams before adding. The material is mixed with a high-speed blender at a speed of about 1000 rpm and put into use immediately.
elastomer coatings are prepared with Isotherm PM or other suitable multi-component high-pressure spraying equipment. Distribute the material at a static pressure of 2000psi and spray it with a Lorek Fusion cleaning spray gun or ProblerAP-2 polypropyl spray gun. Spray the sample on a low surface energy material, such as polyethylene, and the coating can be peeled off within 20 to 30 minutes of spraying. The model for adhesion testing is applied to a 1/4 inch thick steel plate, which is blasted according to the SSPC10 standard to a roughness of 2 to 4 mm. All models are dried at room temperature for 7 days before physical properties and chemical resistance tests are performed.
test hardness in accordance with ASTM test method standard D2240; Test stretch strength and fracture elongation in accordance with ASTM test method standard D1708 or D412. Tear strength (C die) is determined in accordance with ASTM test method standard D624. The hydrolysal × was measured by dipping a 2×2-inch sample (3 mm thick)
in water for 2 weeks at a temperature of 95 degrees C. After soaking, pat the sample dry, weigh, and store it in a plastic bag to prevent moisture from evaporating before the stretch test. Test chemical media resistance in accordance with ASTM test method standard D534-95 and impregnate the 2×2 inch sample with 7-21 days of the required medium at 25 degrees C. The sample is then rinsed with water, dried, and stored in a plastic bag before the stretch test is carried out. The pull-out adhesion test is carried out in accordance with assTM test method standard D4541, and the self-calibration (IV type) pneumatic adhesion tester is used for testing. For samples impregnated with chemical media, the test post is glued to the coating surface after 1 week of drying at 25 degrees C.
results and discussion
evaluate the physical and mechanical properties of hybrid spray polypropylene coatings based on hydrophobic VORAPEL polyols and compare them with the performance of those pure polysaccharide coatings. For this study, two methods were used to introduce VORAPEL polyols into the formulation. In the first method, the pre-polymer (pre-polymer 2) of 16% NCO obtained from VORAPEL is cured with a standard polyplumine resin containing polyamines. In the second method, the same 16% NCO-sealed pre-polymer is cured with a resin mixture that also contains VORAPEL polyols. Samples obtained using these two methods contain nearly 25% (mass ratio) VORAPEL (hereinafter referred to as VORASTAR™7000 pure polypluoride) and 50% (mass ratio) VORAPEL (hereinafter referred to as VORAPEL 7000 hybrid polypluoride). The addition of the above-mentioned VORAPEL polyols to the pre-esters at the NCO sealing end had little effect on the viscosity of the pre-adhesives. However, when polyetheramine was replaced with VORAPEL polyols, a significant decrease in resin viscosity was found. From a practical point of view, the lower viscosity is more convenient for the correct mixing of 1:1 formulations than the pure polycep system, allowing the system to be treated at lower temperatures. The ability to handle materials at lower temperatures provides greater flexibility for spray construction equipment, using viscosity at a given temperature as a way to control the pressure difference between isocyanate and resin batch pumps. Keeping the pressure difference < 100psi ensures that the material can be sprayed and fully mixed at the desired ratio of 1:1.
the reactivity of all elastomer systems is highly dependent on the choice of resin curing agent mixtures. The effective gel time of the two polyetheramine/DETDA resin mixture systems is 3 to 5 seconds, and the drying time is between 7 and 10 seconds. The hybrid formula containing VORAPEL polyols in the resin mixture was extended to 7 seconds and the drying time was 20 seconds. Surprisingly, the addition of VORAPEL to the formulation did result in a moderate increase in the hardness of the coating. The hybrid polypluoride containing only VORAPEL polyols obtained a shore A hardness of 90, while a pure polyol had a shore A hardness of only 85. In general, excellent mechanical properties such as elongation and tear strength are achieved when a resin mixture containing polyetheramine is used in pure polyester materials.
differences in stress-strain properties in pure polysaccharid materials are also reflected in their thermal flow curves, which are analyzed by DMTA over a temperature range of -100 to 200 degrees C. Track the tan and energy storage modules (G') of each system. The VOLORSTAR 7000 pure polypite material has a much higher energy storage volume (approximately 80 mPa) at room temperature than the hybrid polyp (25 mPa). Polymers with high energy storage mods require greater force (stress) to stretch the material (strain), resulting in greater extreme pull strength and elongation performance. On the other hand, high hardness polymers, such as VORAPEL hybrid materials, require less force to stretch the material, which is a preferred choice for applications such as waterproofing. The high temperature stability of VORASTAR 7000 hybrid polysaccharides also showed moderate improvement. The tan-ting curve shows that these two pure polycarp materials can withstand a melting transition of about 150 degrees C, while the melting temperature of the hybrid polysaccharide exceeds 200 degrees C.
the ability of polyol VORAPEL to change the overall hydrophobicity of elastomer samples, our initial efforts focused on measuring hydrolytic stability. Since polypropyle is known to exhibit excellent hydrolysal stability under normal environmental conditions, we have chosen a more stringent set of conditions to test our materials. The data in Table 2 represent changes in quality and mechanical properties after 14 days of immersion in ionized water at 95 degrees C. The sample was assessed for changes in pull strength, elongation, hardness and quality after impregnation. Compared to pure polypropyl samples, all VORAPEL-containing materials have excellent hydrolysed aging properties. When VORAPEL polyols were added to both pre-polymer and resin parts, the loss of stretch strength was reduced from 57% to only 35%, and almost complete elongation and hardness were observed. The improved hydrolytic stability of the VORAPEL 7000 hybrid formula may be due to a significantly lower quality increase in the sample after impregnation. Pure polysaccharides absorb about 5% of their own mass in water, while VORAPEL 7000 hybrids absorb only < 1% of water. By minimizing the absorption of water in the polymer substrate, both the plasticization effect of water (lower hardness) and the hydrolytic lysate (lower stretch strength) of amino methylate/tulle bonds are reduced. The results of high temperature hydrolysal aging show a delicate balance between the treatment of sprayed polysacchar down and the long-term performance of polypropyl. Although this is the fact that hybrid polysaccharides are often sensitive to atmospheric humidity during curing, the total hydrolytic properties of polymers can be significantly improved by carefully selecting polyol compositions; Especially in the construction process can control environmental conditions, such as humidity.
many industrial uses of polyrubon coatings have been discovered to protect steel and concrete surfaces from corrosion from the presence of water-soluble acids such as hydrochloric acid and sulphuric acid. These industries include steel processing, oil and gas production, mining and wastewater treatment. Although there are some polysaccharide coatings on the market that can withstand low concentrations of water-soluble acids, a polysaccharide coating that can prove itself resistant to high concentrations of water-soluble acids over a longer exposure period is still needed. Resistance in these types of applications is best defined as a combination of the coating's ability to maintain its original rigidity and flexibility, as well as its ability to resist swelling (increased size and mass). To achieve this, we decided to evaluate the performance of polypropyl coatings containing VORAPEL in these uses. Effects of dipping polypropyl coatings in 28% HCl and 50% H2SO4. After 7 days of immersion in 28% hydrochloric acid at 25 degrees C, the stretch strength of the two pure polycarbonate coatings was reduced by nearly 90% and flexibility decreased by 50%. Although a moderate improvement in quality improvement was found when VORAPEL (55% to 85%) was added to the polyp, there was little effect on the decrease in mechanical properties. When hydrophobic polyol VORAPEL is added to the isocyanate and resin mixtures at the same time, the coating still has 91% of its original stretch strength and the mass increase is reduced to <2%. Global Coatings Network understands a similar trend in coatings for samples soaked in 50% H2SO4 for 7 days. In this case, however, only the VOORASTAR hybrid system survived the exposure test. After exposure, the sample retains 60% of the stretching performance, retains more than 90% of the starting flexibility, and only 23% of the mass is increased. The surface shows minor color changes and surface defects. Two pure polyphenyl samples showed extreme swelling, with mass increases of 135% and 90% respectively (based on VORAPEL). The surface deformation is so severe that the material cannot be tested for mechanical properties.
potential disadvantage of developing a specific set of hybrid coatings resistant to chemical media and solvents is that samples are increasingly susceptible to other types of chemical media. For example, hydrophobic polymers designed to be water resistant are generally susceptible to erosion from non-polar media. To understand the water resistance and non-polar media capabilities based on the VORAPEL system, we studied the effects of diesel on the mechanical properties of elastomer. As shown in Table 4, there was little difference in the addition of VOAPEL polyols to the prejudge formula (VORASTAR 7000 pure polyphenyl) compared to the pure polypropylene formula. Similar changes in stretching and elongability were found, with only small differences in the percentage increase in mass (9% to 13%). When higher content VORAPEL was added to the polymer (hybrid polyceramics), it was found that the mechanical properties decreased and the mass increased almost twice as much as the pure polysaccharide samples containing polyether amine resins as curing agents. Surprisingly, after all the samples were impregnated in diesel, there was no change in appearance, and the hybrid polysaccharide material maintained excellent adhesion.
chemical medium aging and adhesion
polypropyllycea coatings can often fail due to coating separation from the substrate. Coating peeling may be the result of impact or chemical media erosion of polymers. Excellent ability to maintain the original mechanical properties and low quality increase are important features of the coating, i.e. its ability to adhere to the surface and in