The thermosetting resin needs to add diluents to reduce its viscosity and facilitate further processing. These diluents are actually cheaper organic solvents than the resin, so they also play a role in reducing processing costs. For example, the inactive diluents often added to epoxy resin include acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, n-butanol, styrene, etc. For thermoplastic resin, the purpose of adding solvent is mainly to meet the requirements of process. Because the addition of solvent can be used as a temporary measure to reduce the viscosity of polymer, so that the polymer can be processed into products - for example, suitable solvent can dissolve and join the polymer for bonding, polymer solution can be used for coating, and solvent should also be added for wet spinning. However, the solubility characteristics of polymers are very different from those of small molecular compounds: there is a solubility limit for low molecular weight crystals such as sucrose, which is expressed in grams of soluble sucrose per liter of solvent; However, for amorphous polymers, there is usually no limit to their solubility, that is, they can be miscible with solvents in any proportion. The essence of polymer dissolution can be understood as that the "pores" between polymer molecular segments caused by thermal movement are immediately occupied by more mobile solvent molecules, and this process can continue until all polymer molecules are separated from each other and become "solutions". The process of dissolving the polymer can also be seen as a controlled diffusion process. Sometimes the concept of certainty can be said that the polymer dissolves the solvent rather than the opposite. If the polymer molecule is cross-linked, the movement of the chain segment is limited. A slightly cross-linked polymer will swell or slightly dissolve in the solvent until the penetration force or diffusion force is balanced by the elastic contraction force of the extended polymer molecule, but it will not dissolve into a mobile solution. Highly cross-linked polymers will not move in segments and absorb this liquid, so it is impossible to swell or partially dissolve. Generally, there is a critical dissolution temperature for soluble polymers. Below this temperature, the system is divided into two phases: insoluble swelling polymers and almost pure solvents. A large amount of nonsolvent can be added to the polymer solvent without precipitating the polymer. Adding these nonsolvents in the event can improve the solubility, and they are often called latent solvents. It is often the case that the mixture of two non solvents is a good solvent for a polymer. For example, the solvent for cellulose nitrate is an ether alcohol mixture, while the opposite also exists. For example, cellulose acetate can be dissolved in aniline or strong acid, but not in their mixture. The most useful way to increase the dissolution rate of powdered polymer is: first, suspend the powdered material in a non solvent, and then add a real solvent. This operation process can prevent the agglomeration between polymer particles; The second is to accelerate the dissolution rate by heating. Common corresponding brands of Chinese general diluents: x-1: · Nitrocellulose paint diluent x-3: perchloroethylene paint diluent x-4: phenolic paint diluent x-5: acrylic paint diluent x-6: alkyd paint diluent x-7: epoxy paint diluent x-9: phenolic paint diluent x-13: silicone paint diluent
Banana water, also known as Tianna water, is mainly composed of isoamyl acetate. It is highly volatile, flammable, explosive and toxic. It is dangerous. It is called banana water because of its strong smell of bananas. Ethyl acetate, n-butyl acetate, benzene, toluene, acetone, ethanol and butanol are prepared into a mixed solvent according to a certain weight percentage, which is called banana water. Pure banana water is a colorless, transparent and volatile liquid with a strong smell of bananas. It is slightly soluble in water and can be dissolved in various organic solvents. It is flammable and is mainly used as a solvent and diluent for painting. Preparation method of banana water: according to the weight ratio, take 15% n-butyl acetate, 15% ethyl acetate, 10-15% n-butanol, 10% ethanol, 5-10% acetone, 20% benzene and 20% xylene, and then fully mix them to make banana water. It is commonly used as a thinner for furniture paint, article paint and automobile paint.