Main types and characteristics of polyurethane foam

Due to different production processes, the formula components are adjustable Polyurethane can be made into many different types of foam. This diversity can be classified.

（ 1) hard foam , soft foam and semi-hard foam

press<font face The softness and hardness of polyurethane foam can be divided into Softpolyurethane foam (polyurethane soft foam for short), hardPolyurethane foam(polyurethane rigid foam) and semi-rigid foam in betweenPolyurethane foam (polyurethane semi-rigid foam, abroad Also called semi-soft foam).

Polyurethane soft foam is commonly known as polyurethane sponge and foam. This type of foam has good elasticity and is mainly used in various cushions and cushioning materials, such as cushions, back cushions and armrests for cars, boats, furniture and sofa seats, mattresses, clothing linings, etc. .

Polyurethane rigid foam is hard. Low-density hard foam is mostly brittle material. Most polyurethane rigid foam has a closed-cell structure and is foamed with a low thermal conductivity foaming agent. Therefore, the thermal conductivity is low and it is widely used in various thermal insulation fields. High-density hard foam has good toughness and high strength.

Semi-rigid foam has a certain open-cell structure, has good load-bearing performance and good vibration absorption performance, and is mostly used in cushioning materials, automobile parts, etc.

（ 2) High density and low-density foam plastics

Polyurethane foamIncludes soft foam, hard foam and semi-hard foam. According to different uses, there are high density and low density. The details will be introduced in the relevant sections.

（ 3) polyester Type and polyether typePolyurethane foam

According to the types of oligomer polyol raw materials used, Polyurethane foamCan be divided into polyether type and polyester type. Polyester typePolyurethane foamhigh strength, but because the ester group is not resistant to hydrolysis, the hydrolysis resistance of the foam is poor, and the cost of polyester polyol It is relatively high, which also limits its application; polyether polyols are rich in varieties, relatively low in cost, and have good hydrolysis resistance. Therefore, polyether polyols are used in the soft foam market. <font face="宋体"According to the production process of polyurethane foam, it can be divided into one-step method and prepolymer method (two-step method). At present, the one-step method is basically used to produce polyurethane foampolyurethane foam. In the production of hard foam, semi-rigid foam and high-resilience molded foam, for the convenience of use, polyol and additives are premixed into one component, and polyisocyanate is used as another component. After measurement, the mixture is mixed and foamed. Bubble.

Polyurethane foam can be produced using continuous and batch processes. Ordinary soft foam can be produced using a continuous process. The foam plastic is cut to obtain block foam (referred to as block foam). Block foam can be produced from both soft foam and hard foam. >Polyurethane foam is mainly soft foam. Unless otherwise specified, "Block bubbles" generally refers to block-shaped soft bubbles. Rigid polyurethane foam laminates used in building materials and insulation boards mostly adopt a continuous production process. Rigid polyurethane foam can also be produced through a spray molding process and can be foamed on site.

Molded foam plastics are generally produced by the intermittent method. Foam plastic parts of the required shape are foamed directly in the mold. This process is often used when products with special geometric shapes need to be produced. Hard foam, semi-hard foam, and soft foam can all be produced through molding methods, such as high-resilience foam, microporous polyurethane soles, whole-leather soft foam, and RIM products. Depending on whether heating and curing are required, molded soft foam can be divided into cold molding and hot molding. Some batch processes do not require molds and are poured directly, such as hard foam laminated boards, refrigerators, freezers, water heater insulation layers, etc. Box foaming of soft and hard foam still has some applications in small businesses.