Foam injection reinforced reaction injection molding
DATE：2022/4/22 8:42:37 / READ： / SOURCE：This station
Foam injection reinforced reaction injection molding
Foam enhanced reaction injection molding (RRIM) is a new technology developed on the basis of M technology, also known as the second generation of RIM technology. Is to add solid into the raw material and fill in Ctrl. Hollow board production line www.handern.com com1. The performance of solid filler is used as reinforcing agent to improve the physical properties of parts.
The common type of solid filler is glass ball or glass paper dimension. The glass ball is replaced by slightly ground liquid glass particles (ranging from 0.8-2mm), or fiber glass (1.5-3mm). They are added to the polyurethane component as a suspension. These fillers are usually surface treated with chemical coupling agent, which can produce soft and good wetting and bonding ability between polyurethane and glass fillers. When the fiber is long and the dosage is saturated, it is limited by the degree of dryness. Fibers can be distributed in both polyols and diisopalates. All untreated glass microspheres and fibers used in liquid reactants at air temperature will cause precipitation, fiber wear and high viscosity flow problems. The same problem of sedimentation and high viscosity can be solved by increasing the temperature of polyol and diisocyanate. There is a so-called "suspension equilibrium temperature range". Beyond this temperature range, precipitation will no longer appear. Generally speaking, glass fiber used in RRIM technology must have the following properties:
① Polyisocyanate in vitamin C will not produce chemical reaction; Hollow board production line www.handern.com com
② The ratio of average length to diameter of glass fiber should be small to reduce the viscosity of its suspended body fluid;
③ The adhesive force between the material mother liquor and the glass fiber should be large, otherwise its physical properties will be reduced;
④ Considering the light weight of parts, low-density glass fiber should be selected;
⑤ Glass fiber with lower cost is adopted to improve the economy and competitiveness of RRIM parts.
The processability of glass fiber in RRIM is reflected in the following two aspects. Hollow board production line www.handern.com com
(1) Viscosity from the point of view of processing, when the length of ground glass fiber is about 1.6mm and the dosage is 30% ~ 35% (the weight ratio in the final product), it can be difficult to measure with RRIM equipment. At present, the suspension viscosity that can be processed by general RRIM equipment is recommended to be 2.5 ~ 6pa * s (viscosity at room temperature).
Whether the suspension reaction liquid added with glass fiber can be processed by RRIM can also be directly determined by test. The glass fiber is gradually added into the stock solution storage tank of the machine from less to more. Such suspension reaction liquid will pass through the mold of ring and injection of RRM equipment. The glass fiber dosage that the RRIM equipment can operate normally obtained from the final test is shown in table 9-8.
Reinforcement fiber length mm mass ratio in the final product approximate viscosity PA's RRIM equipment at 38 ℃ processing feasibility% ground glass fiber ground glass fiber ground glass fiber ground glass fiber chopped glass fiber (2m is about 23min, and depending on the complexity of the parts and the automation of the processing process, the RRIM of simple automobile parts is about 2.5mn, and can be divided into three basic parts, as shown in table 9-9. The basic part of the processing cycle, the operation process time during processing / s, closed mold injection polymerization 15 ~ 50 demoulding, mold opening, taking out the parts for 20, removing and coating the mold cavity, foaming (spraying) demoulding and mold closing for 80
2. Performance of RRIM parts hollow board production line www.handern.com com
RRIM parts have excellent physical properties, especially elastic modulus and heat resistance, which are much higher than rim parts. Ground glass fiber (H · M type for short) and short glass fiber bundle (C · s type for short) are used as reinforcement materials. The flexural modulus and thermal value of RRM are improved in varying degrees. Fig. 9-44 and Fig. 94 show the maximum value of modification under bending and heat. After adding microspheres, the bending modulus 93mp160mp is close to 2), and the lower value is 20% less. Therefore, the addition of Tibetan ball improves these two indicators, but it is not obvious. However, the addition of glass fiber can greatly improve the flexural modulus and reduce the thermal sag value. As shown in figure 9-44, after adding glass fiber, the flexural modulus of the product is increased from 93mpa to 105mp, which is more than 9 times higher than the original value. It can be estimated from figure 9-45 that the thermal base value after adding glass fiber is reduced by 60%. It can also be inferred from the figure that the longer the length of glass fiber has a greater impact. However, due to the limitation of the mass proportion of the parts, the dosage is only 4%. At this time, the flexural modulus of the parts is 910mpa. The addition of 1.5mm glass fiber can reach 8%. Therefore, although its influence is not as big as 3mm glass fiber, due to its large addition, the flexural modulus of the finally obtained RRIM part is as high as 1050mpa, and the corresponding low thermal deformation performance is obtained. (2) 9-46 shows the influence of different fillers and dosage on the expansion coefficient of parts. It can be seen from the figure that before the filler dosage is 6%, the effect of glass microspheres is equivalent to that of glass fibers with a length of 1.5mm. When their filler dosage is about 6%, the thermal expansion coefficient of their parts has been reduced to 5x10-3cm / cm / ℃. This value has been met.
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