grp pultruded profiles process because of the agricultural production system with a high degree of mechanization, continuous production, product quality and performance stability, etc., over the years to obtain continuous stability of the high growth. However, due to the majority of pultruded factories are not large, weak technical force, so the production process encountered many problems, the common problems are.

1, resin gel coat mixture of thickening phenomenon

The so-called thickening phenomenon refers to the use of a good resin gel coat mixture in the process of gradually increasing the viscosity, and the viscosity of the increase in speed, until the mixture is difficult or even impossible to use the degree.

This phenomenon is often encountered, but it is difficult to find the problem and the solution, the reason for this phenomenon is due to the presence of highly acidic components in the formula, mainly the formula used in the liquid release agent, this group of components and the mixture of alkaline fillers such as calcium carbonate or metal oxide pigment chemical reaction, so that the separation of calcium ions or other metal ions. These separated calcium ions or other metal ions will quickly and polyester molecular chain end of the carboxyl group chemical reaction to generate complexes, forming a polyester-metal complexes of the mesh structure, so that the mixture of the viscosity increases sharply, reducing mobility, the rapid increase in viscosity leads to its difficulty in penetrating the glass fiber, so that the pulling resistance also increases. The resulting products have degraded performance due to insufficient infiltration. Highly acidic components will also have a chemical reaction with some acid-sensitive pigments, so that the color of the product drift.

2、The choice of filler

Filler is a very important component in the pultrusion formula, used properly, can improve the processability of the resin system and the performance of the cured products, but also can significantly reduce the cost of composite materials. If used improperly, they can also seriously affect the processing properties and product performance. In general, any powdered mineral can be used as a filler.

The effect of fillers on liquid resin systems is to increase viscosity, produce thixotropy, accelerate or retard curing, and reduce exotherm. Among the process factors they influence, the important one is the effect on viscosity and rheology. The main influence on viscosity is the oil absorption rate of the filler. In other words, the lower the oil absorption rate is, the larger the filler can be added while maintaining the same viscosity. In addition, the specific surface area of the filler will affect the polymerization speed. Light calcium carbonate and talc have large specific surface area, which will block the curing; while heavy calcium carbonate has a smaller specific surface area and better curing performance.

By coating the surface of calcium carbonate with agricultural production system substances to form active calcium carbonate, it makes the aggregated state particles reduce, the dispersion increases, and the inter-particle voids decrease, thus reducing its oil absorption rate even more. In addition, the price of the filler is also an important reference for choosing which filler to use. Among several common fillers, the low cost is bicarbonate and talc, the cost of surface activated bicarbonate is slightly higher, the cost of kaolin is in the middle, and the high is aluminum hydroxide. Aluminum hydroxide is usually used as a flame retardant filler and not as a general filler.

The effect of various fillers on the mechanical and physical properties of the cured products is roughly equivalent. The effects on flame retardancy and electrical properties are slightly different. In addition, the impact on the dynamic mechanical properties of the product is more complex, and the filler particle size, particle size distribution, particle shape, hardness and filling amount are related.

3、Cracking of the product

Cracking of the products, including surface cracks and internal cracks, is a very uncomfortable problem for grp pultruded profiles manufacturers. Cracking is mainly caused by the thermal stress resulting from exothermic shrinkage. There is a consensus among many manufacturers on this point. However, it is still difficult to find a better way to eliminate thermal stresses. Although proper adjustment of die temperature and extrusion speed may temporarily alleviate the problem, the cracks will reappear as the environmental conditions change and for some unidentified reasons. There may be times when cracking occurs suddenly under very normal circumstances, leaving you unprepared.

Adding only a small amount of anti-cracking brightening powder (2-5% of the resin amount) will have a significant effect. Since the amount added is not large, it has little effect on the performance of the product and can also enhance certain properties. In addition to reducing cracking, it also has the advantages of increasing the luster of the product surface and making the color of the product more uniform. Adding this component to the formula can reduce the scrap rate to a great extent and make the production smoother and more smooth.