Polyethylene foam life jacket core material
DATE：2022/6/1 8:47:58 / READ： / SOURCE：This station
Polyethylene foam life jacket core material
Polyethylene foam plastic life jacket is made of polyethylene foam life jacket core and canvas through special processing. This kind of life jacket must be worn quickly when in use. After falling into the water from 3m height, the head should be exposed to the water within 2~3s, and can turn over automatically within 5S to make people face upward to achieve the purpose of life saving. Compared with other foamed plastics, polyethylene foamed plastics are used as the core of life jacket, which has the advantages of light weight, soft material, comfortable wearing, good fastness and aging resistance, rich raw materials and simple processing technology. Coating compound production line www.handern com1. raw materials and formula
① Polyethylene resin uses low-density polyethylene resin (LDPE) with a melt flow rate of about 2g/10min. The melt flow rate directly represents the fluidity of polyethylene resin in the molten state, so as to compare the relative molecular weight. Generally, if the melt flow rate is large, the relative molecular weight is small, and the processing performance is correspondingly better. The melt flow rate was measured by a melt flow rate meter. ② Chemical crosslinking agent diisopropyl peroxide ③ foaming agent Azodicarbonamide. ④ Activator tribasic lead sulfate.
See table 6-15 for the core material formula of polyethylene foam life jacket. Table 6-15 proportioning amount of polyethylene foam lifejacket core material formula raw material name / proportioning amount of quality parts of raw material name! Mass fractionation ethyl resin 100 Azodicarbonamide peroxide diisopropyl benzene 0.8~1 tribasic lead sulfate was used to prepare foamed plastics with foaming ratio of 40. Azodicarbonamide was used as foaming agent. Generally, 20 parts shall be added to 100 parts of LDPE. In order to disperse the foaming agent evenly, white oil, turpentine, propylene oxide or ethylene oxide can be coated on the surface of the resin to make the foaming agent stick to the LDPE solid particles, or a small amount of it can be mixed in the granular resin to soften at a lower temperature
High powdery resin. Coating compound production line www.handern com
2. production process
The production process of polyethylene foam lifejacket core material is shown in Figure 6-6. LDPE resin crosslinking agent foaming agent mixing plastic drawing sheet punching chip material foaming agent crosslinking agent pressure heating decomposition activator cooling demoulding heating swelling foaming cooling demoulding inspection packaging polyethylene foam lifejacket core figure 6-6 production process of polyethylene foam lifejacket core material
3. equipment coating compound production line www.handern com
Production equipment includes plasticizer, steam cylinder, hydraulic press, blank mold and forming mold. See Fig. 6-8 for the intersection structure. See Fig. 6-7 for the structure of the die for the joint polyethylene molding blank, and the structure of the cross-linked polyethylene molding die
4. operation process coating compound production line www.handern com
① Weigh the material. Weigh materials according to the components in the formula · 208 ② mixing. First, mix the polyethylene resin in the plasticizer for about 5min, and control the temperature at 110~120 ℃. After the polyethylene resin is melted into pieces, add the diaminodicarbonamide and tribasic lead sulfate, and reduce the temperature to about 70~100 ℃. Mix for 10min. In the mixing process of adding foaming agent, if the temperature is too high, the foaming agent will decompose prematurely.
③ Add diisopropyl peroxide, mix for 5min at the same temperature, press into pieces, and cut into blocks. When chemical crosslinking agent is used for atmospheric crosslinking, it is also necessary to prevent the decomposition of crosslinking agent in the process of mixing and forming billets. Therefore, the processing temperature should be strictly controlled.
④ Molded into a blank. Put the sheet into the mold, place it in the steam cylinder, heat it to 160 ℃, pressure 0.6MPa, mold it for 12~15min, cool it to room temperature, and take out the hard block shaped unfoamed blank. This process makes polyethylene cross-linked.
⑤ Foaming molding. Put the blank into the foam forming mold with fine holes around, pressurize it on a 140t press, the gauge pressure is 9.8MPa, the steam pressure is 0.6MPa, and heat it for 13~. 209'15min, make it expand and foam to form, then cool it for 6~8min, demould it to become a product. There are two methods for heating the mixed and formed billet. One is to heat at a certain temperature for a period of time to decompose the crosslinking agent (but the foaming agent cannot decompose), and the resin is crosslinked; Then raise the temperature to decompose the foaming agent. This method is called two-stage heating method. There is also a one-stage heating method, which directly heats the billet to a temperature above the decomposition temperature of the foaming agent. In the one-stage heating method, a part of the cross-linking agent decomposes before the foaming agent. This principle is the same as the previous method. However, the amount of cross-linking agent in one-stage heating method is greater than that in two-stage heating method, which improves the cross-linking efficiency and the strength and heat resistance of foamed plastic products. No matter which heating method is used, the cross-linking resin needs to be heated above the melting point. Therefore, it is necessary to prevent decomposition of the crosslinking agent during mixing and forming of the billets. It is better that the crosslinking agent decomposes rapidly when heating the preform after forming. Attention should be paid to these two requirements of crosslinking agent during processing. In addition, if the decomposition temperature of cross-linking agent is high, the resin will be in a state of low melt viscosity for a long time, resulting in the deformation of the billet due to flow and adhesion to the carrier belt. The following methods can be used to solve the problem of adhesive tape.
① Non adhesive polytetrafluoroethylene, metal or other non adhesive materials are used as carrier tapes.
② Silicone oil, polytetrafluoroethylene lotion, mica powder and other anti sticking materials are used. ③ Salt bath floating or air floating.
④ The surface of the material is initially heated at high temperature to make the surface slightly cross-linked to maintain the shape of the billet.
5. problems, causes and solutions in production
Problems easy to occur in production, causes and solutions: Causes and solutions for abnormal phenomena: bubble collapse heating time is too long, and the bubble is too small. Appropriately reduce the heating time, and gas escape. Strengthen the sealing of the mold. There are holes in the incomplete crosslinked foam
Improve the crosslinking degree of raw materials with impurities. The foaming agent is mixed unevenly or agglomerated, and strengthen the raw material inspection. Coating compound production line www.handern com
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