Coating industry: Strippable coating is a kind of functional coating for short-term protection of matrix surface, with good constructability, corrosion resistance and anti-friction properties, and is widely used in furniture, construction, machinery, Marine engineering and other fields. Solvent-based strippable coatings currently occupy a large market, with simple coating, good mechanical properties, short curing time and other characteristics, but the large use of organic solvents is undoubtedly one of its big shortcomings. In contrast, water-based peeling coatings are free of volatile solvents, which has great advantages in health and environmental protection requirements, and its research and development and application heat are increasingly prominent.

1.The function and mechanism ofwater-based peelable coating

For strippable coatings, strippability and cohesiveness are two important indicators. The adhesion of the peel coating film should be moderate, too high adhesion will affect the peel of the film, too low adhesion will affect the corrosion resistance of the film, can be used to measure the substrate adhesion of the peel coating by 180° peel strength test to verify its strippability. At the same time, the coating film should have strong cohesion, the coating film will be stretched away from the substrate when it is stripped, and the film layer should remain continuous without fracture; If the strength of the film is not enough, the film layer may fracture or break into small pieces during peeling, which can not achieve the purpose of peeling. Tensile strength and elongation at break are usually used as indicators to measure the cohesion of the film.

The main function of water-based peeling coatings is protection and decontamination. The use of water-based peeling paint as a protective film on the surface of furniture, mechanical parts, etc., can avoid direct contact between the medium such as microorganisms in the air and the surface of the protected object, slow down the corrosion failure rate of the surface, and thus play a protective role; At the same time, this protective film has a certain elasticity, and can play a buffering and protective role in the impact and grinding of the outside world. In addition, during the film forming process, the water-based strippable coating transfers the pollutants on the surface of the object to the film through adsorption; Or through the viscosity of the film-forming substance itself, the residue or pollutant on the surface of the protected object is adhered to; Both of these methods can transfer residues or pollutants to the film, and finally tear off the protective film on the surface of the object, thereby removing residues or pollutants.

2.Classification of water-based peelable coating

According to the different film forming substances, water-based peeling coatings can usually be divided into vinyl, acrylic resin, polyurethane and other different types.

Vinyl water-based strippable coatings: Many vinyl resins can be used to make water-based strippable coatings, the most commonly used is polyvinyl alcohol. As a hydrophilic polymer material, polyvinyl alcohol is conducive to the preparation of water-based strippable coating, the actual use of the process to add appropriate accessories and fillers, you can get good protective performance, and achieve special functionality, not only can be used to remove heavy metal pollution on the surface of the substrate, radioactive pollution, but also can be used to protect the surface of the substrate. It can even be used to protect cultural relics such as murals.

Acrylic resin water-based peelable coating: Acrylic resin is widely used in the coating industry because of its good weather resistance, oil resistance and high temperature oxidation resistance. The strippable coating prepared by acrylic emulsion has good strippability, adhesion and durability over a wide temperature range, and can retain good stripping properties after long-term outdoor exposure. At present, the related research direction mainly focuses on monomer copolymerization, substance modification, the influence of pigment filler, etc. The copolymer of acrylic monomer resin and polyvinyl alcohol can also be used to prepare strippable coatings.

Polyurethane waterborne strippable coatings: Because of its good mechanical properties and special molecular structure, polyurethane resin can be used as a film forming substance of strippable coatings, but also as a thickening agent of other strippable coatings. As a film forming material, polyurethane resin has the advantages of high mechanical strength, acid and alkali resistance, organic solvent resistance, salt spray resistance and good strippability. As a thickener, the hydrophilic and hydrophobic groups contained in its structure can significantly improve the chemical and biological stability of the coating film, improve the rheological properties of the coating, effectively prevent the coating layer deterioration, and enhance its construction convenience. Polyurethane-based coatings have relatively high wear resistance and flexibility, and have good adhesion to various substrates (such as wood, concrete, floor and plastic), so polyurethane-based peel coatings can be applied to metal, plastic, ceramic, automotive shell, concrete, floor and other substrates.

Other water-based strippable coatings: other substances such as liquid rubber, silicone, cellulose and derivatives can also be used as film forming substances for water-based strippable coatings.

3.Research and application prospect of water-based peelable coating

From the perspective of film forming resin, it is difficult for a single structure resin to meet the modern practical needs, so the film forming resin synthesized by a variety of monomer copolymerization is a major research focus of water-based peeling coatings. At the same time, in order to improve the strippability of the coating, a good strippable agent is also the key research direction of the strippable coating. In addition, the selection, allocation and use of materials such as fillers and emulsifiers have a great impact on the strength, stability, protection or decontamination performance of water-based strippable coatings, and are becoming a popular Angle for their research and development. Water-based coating can peel application range, in addition to the traditional furniture, machinery, automobile, etc on the surface of the temporary protection, now also gradually towards the new plate has not extended. Protection and maintenance during the storage and transportation of cultural relics, decontamination and antibacterial in the food processing industry, anti-scratch, moisture-proof and mildew of optical instruments, and trace collection in judicial identification... The application fields of water-based peeling coatings are becoming more and more novel, sophisticated and diversified.