Polyurethane Pultrusion Products Technology

 

Pultrusion Mold Opening Method and Injection Box Design Structure

 

Pultrusion Mold Opening Classification is as Follows:

 

Pure Unidirectional Fiber Wall Products

 

Pure fiber polyurethane pultrusion products The injection box structure is medium and low pressure injection.

The yarn is relatively dispersed through the injection box and fully impregnated in the injection box before entering the mold cavity for extrusion and mixing. After mixing, the fiber and resin are completely combined and shaped in the temperature zone. A process method for pultrusion to produce a finished product. During the design process of the mold, the mold manufacturer should open the mold according to the thickness and structure of the product, with an appropriate amount of slope for the mold injection box and the resin guide groove.

 

 

Attached Figure Mold Schematic Diagram

 

 

 

The Mold Opening Classification of Pultrusion Molds is as Follows:

 

Adding Felt or Axial Cloth or Adding Multi-directional Fiber Products

 

Multi-Directional Fiber Polyurethane Pultrusion Products

The Injection box Structure is Medium-High Pressure Injection.

 

The multi-directional fiber first passes through the cold mold (the cold mold cavity size is equivalent to the product cavity size) to shape the yarn and felt before entering the injection box with a certain space. The resin and fiber are combined by high-pressure injection in the injection box. The fiber and resin are combined through the correct mold cavity, and are shaped in the temperature zone.

 

A process method for pulling out the finished product. During the design process of the mold, the mold manufacturer should appropriately increase the volume and slope of the mold cold mold injection box and the resin guide groove according to the thickness and structure of the product. Simple diagram

 

 

Case 1 of theoretical calculation method for raw material usage of polyurethane pultrusion products (combined with calculation cases, language explanation, explanation of experience threading)

 

Calculation method of threading amount of “certain” slot-type bridge polyurethane products

 

Calculation Method for Yarn Throughput of Polyurethane Products for “[Model]” Channel-Type Cable Trays.

 

 

 

How to Design Precise Guide

 

Polyurethane pultrusion products have a high fiber content, and the fibers are easily squeezed in the mold cavity, causing yarn congestion, which in turn causes various problems. Therefore, the role of precise guide in the process cannot be ignored.

 

Principles to Follow in Making Precise Guides:

 

Select reasonable grams of fiber or felt cloth according to product performance requirements, cross-section and thickness.

 

There must be a certain tension when the fiber passes through the guide structure.

 

When making preforms, the yarn should be gradually introduced into the mold cavity. If necessary, a cold mold should be added to confirm whether the yarn is running along the predetermined track.

 

The guide yarn plates that the yarn passes through should be gradually merged. During the merging process, the yarn amount required for the thickness of the product needs to be accurately calculated.

 

In fact, the yarn has an extrusion process after entering the mold cavity through the guide. When distributing the last yarn plate of the yarn, we try to introduce the merged yarn in the form of a plane or arc surface. Each plane or arc surface is a whole to avoid large distortion or overlap of the yarn after being squeezed in the mold cavity.

 

The concept of precise guidance is that the fiber enters the mold cavity uniformly. Even if it is squeezed in the mold cavity, it is limited and does not affect the normal production and performance of the product. Such guidance can meet the size and performance of each part of the product.

 

How to design uniform temperature control

 

Polyurethane resin is very sensitive to mold temperature. Polyurethane can usually be cured in 15 minutes at room temperature and react in a few seconds at 200 degrees. Therefore, good polyurethane products must be molded at a uniform temperature. Too high or too low temperature or uneven local temperature will affect the product or fail to exert the characteristics of resin application. Therefore, stable temperature control is a necessary link in the whole process (see figure for details)

 

Mold design

 

Process Requirements for Glue Injection Machine

It has the characteristics of wide discharge range, accurate and stable discharge, ultra-wide variable ratio, easy regulation, stable injection pressure, etc.

 

High-pressure pump (plunger pump) and low (normal) pressure pump (gear pump, screw pump).

 

Choose the appropriate pump according to the product requirements, and explain in detail.

 

 

Select suitable raw materials according to product requirements and follow what standards.

 

Product structure classification Pure yarn thin wall, pure yarn thick wall, felt thin wall, felt thick wall, ultra-small cross section, large cross section

 

Rough Classification of Performance Requirements

 

Tensile strength, hoop strength, impact strength, elastic modulus, flame retardant or heat resistance, water absorption, insulation When developing or outsourcing, we must first fully analyze the product requirements, conduct docking analysis on the process and mold structure, and then select the corresponding resin and fiber. The existing resin manufacturers can make appropriate adjustments to the viscosity, strength and toughness of the resin, including flame retardancy, etc.

 

The existing raw material manufacturers of glass fiber can also match the wettability of the process and adjust the strength of the yarn within a certain range. Attached is the polyurethane test report. In short, the specific product is analyzed specifically. The supporting raw materials on the market can basically meet the product requirements within the maximum performance range of polyurethane. Before processing the product, fully analyze the product structure and performance to ensure that the polyurethane pultrusion process is satisfied before making in-depth investments.

 

The impact of traction equipment and traction fixtures on the process and how to choose them.

 

Polyurethane pultruded products have greater resistance when starting the machine and adding yarn. Choosing appropriate equipment according to the shape of the product and customizing the tooling and fixtures on the production equipment are the key to improving efficiency, saving costs and continuous and stable production. The general principle is to make the product and the fixture have a larger contact area as possible to disperse the force, minimize the downward pressure to ensure that the product is less affected by external mechanical forces and deformed. What products are suitable for hydraulic equipment and under what circumstances should crawler equipment be selected.