Introduction of Aramid Composite Material Application and Molding Process

The full name of aramid is "aramid fiber", and the DuPont’s Kevlar is a kind of aramid fiber, that is, para-aramid fiber. It is a new type of high-tech synthetic fiber. It has super high strength, high modulus, high temperature resistance, acid and alkali resistance, and light weight. Its strength is 5 to 6 times that of steel wire, its modulus is 2 to 3 times that of steel wire or glass fiber, and its toughness is 2 times that of steel wire. The weight is only about 1/5 of the steel wire. It does not decompose or melt at a temperature of 560 degrees. It has good insulation and anti-aging properties, and has a long life cycle. The discovery of aramid is considered a very important historical process in the material industry.

Aramid composite helmets occupies a very important position in military and police bulletproof helmets and bulletproof vests. It has light weight, strong bulletproof ability and large protective area. Compared with ordinary helmets, it has obvious advantages.

The process of aramid material molding temperature control mainly includes two aspects, one is to preheat the molding material, and the other is to control the molding temperature.

In the molding process, the role of the mold temperature machine mainly includes the mold installation temperature control, heating rate control, molding temperature and heat preservation control, and cooling.

Before pressing the aramid material, use a mold temperature machine to preheat the molding material to evaporate water and other substances, which can increase the curing rate and shorten the pressing cycle; enhance the uniformity of product curing, improve the physical and mechanical properties of the product, and increase the molding material Of mobility.

Following is the control point of Aramid SMC.

1. Mold loading

Mold loading temperature refers to the temperature required by the mold when the material is put into the cavity. It mainly depends on the type of material and the quality index of the molded material. Generally, when the volatile content of the molding material is high, and the insoluble resin content is low, the molding temperature is lower. On the contrary, it is necessary to increase the mold temperature appropriately. The product structure is complex and the mold installation temperature of large products is generally within the range of room temperature -90℃.

2. Heating process

Refers to the heating rate from the mold loading temperature to the highest pressing temperature. For the rapid molding process, the molding temperature is the pressing temperature, and there is no problem of heating rate. For the slow molding process, an appropriate heating rate should be selected according to the type of molding material resin and the thickness of the product. Compression molding mold temperature machine can complete the mold heating process at a certain heating rate through a programmed program.

3. Reach the molding temperature

The resin will release or absorb a certain amount of heat during the curing process, and the degree of the resin polycondensation reaction can be judged according to the heat release, so as to provide a basis for determining the molding temperature. Under normal circumstances, first determine a relatively large temperature range, and then select a reasonable molding temperature through process-performance tests. The molding temperature has a great relationship with the variety of molding materials. The molding temperature is too high, the resin reaction speed is too fast, the fluidity of the material decreases too fast, and early local curing often occurs, and the cavity cannot be filled. If the temperature is too low and the product holding time is insufficient, defects such as incomplete curing will occur.

4. Heat holding process

The function of the heat holding process is to completely solidify the product and eliminate internal stress. The length of the holding time depends on the type of molding material, the level of molding temperature and the structural size and performance of the product. Compression molding mold temperature machine uses heat transfer oil as the heat transfer medium, the temperature can be maintained at 300 ℃, and the temperature control accuracy needs to be controlled at ±0.1 ℃.

5. Cooling process

In the slow molding, after the heat preservation, the temperature must be gradually lowered under a certain pressure, and the mold release operation can be performed when the mold temperature drops below 60°C. There are two cooling methods for the mold temperature machine: natural cooling and forced cooling.

The rapid pressing process does not require a cooling operation. After the heat preservation is completed, the mold can be demolded at the molding temperature, the product is taken out of the mold, and the necessary auxiliary processing is performed to obtain the product.