Application of low foaming hollow blow molding
DATE：2021/10/19 9:05:58 / READ： / SOURCE：This station
Application of low foaming hollow blow molding
The low-foaming plastic transport box made by Weiyi Company with hollow blow molding can bear a weight of 2t. The same size plastic transport box can only bear a weight of less than 1t. In addition, low foaming hollow blow molding of sandwich structure is also being widely used. In 1995, Krupp launched a new hollow blow molding foam molding machine. This is a kind of extrusion hollow blow molding foam plastic molding machine, the product is sandwich three-layer composite hollow blow molding foam plastic furniture. Kautex Werke AG in Germany spent a year successfully developing a two-layer air duct for automobiles. The outer layer is a non-foamed or less-foamed layer, while the inner layer is a high-foamed layer. Other application examples are toys, car dashboards, door linings, cosmetic bottles, etc.
In addition, expandable polyethylene pellets can also be used for hollow blow molding. The parts obtained by this method have pearly luster, high whiteness, and independent bubbles, which make the parts rich in heat insulation, cushioning and softness. The standard molding conditions of the low-foaming hollow molded parts of expandable polyethylene pellets and the physical properties of the resulting products are shown in Table 10-5. In the table, the flexible foam is LDPE expandable pellets, and the semi-rigid foam is MDPE expandable pellets. The manufacturing equipment and approximate parameters of the products in the table are: the product is a 500c cylindrical bottle, and the blank of the double-head hollow molding machine weighs 20g is made by the extruder, the extruder screw diameter is 45m, and L/D=16:1. The inner diameter of the die hole is 134m, and the outer diameter is 17.8mm. When the blank is extruded from the die of the extruder, the expansion ratio is very large due to the accompanying foaming, and the expansion rate of the die is usually 2.5 to 3.5. Therefore, compared with the die of the unfoamed extrusion blank, the aperture of the foamed extrusion blank should be relatively small. In addition, under the premise of not stretching too many cells, a traction auxiliary device can be added to help extrude the extruded blanks with the best foam distribution and the thickness of the blanks. Compared with other foam molding methods, hollow blow molding is still under development. Many new technologies are also in the experimental stage, such as microbubble technology. Many plastic raw material manufacturers have also seen the prospects for the development of hollow blown foam plastics, and have accordingly developed some resins with higher melt tension (corresponding to higher molecular weights). In practical applications, some companies mix in an appropriate proportion of LDPE (linear low-density ethylene) to maintain the proper diameter of the foam and reduce the deformation of the foam.
In practical applications, low-foaming hollow blow molded products have to consider the possibility of recycling. A typical example is to use the same plastic with different grade groups or composite layers of low-foaming hollow blow molded products. The specific combination is as follows.
①The skin layer is made of non-foaming, smooth and scratch-resistant high-grade plastics. The middle layer is foamed low-grade same plastics or even recycled plastics of the same type for secondary use.
②The skin layer is made of low-foaming or micro-foaming plastic (the amount of foaming added is small). The layer is of the same type and grade with higher foaming ratio, but with high-grade foaming agent added.
The above two methods are application examples that are easy to recycle.
Author：admin