Epoxy resin cast parts prone apparent problems and the inherent problems. China Association of epoxy resin industry experts say, the apparent problem mainly bubbles, cracks, defects, deformation of the problems inherent in the main parts mechanical strength, electrical properties meet the requirements, partial discharge or breakdown, system the pieces heat distortion temperature low. The current industry this full attention to adaptation of the world's leading epoxy Preparation and application development momentum.
The expert pointed out that the same apparent quality of the intrinsic quality of the epoxy resin cast member is related bubbles, cracks, defects, and other phenomena parts, mechanical strength, electrical properties are often substandard, the analysis of these phenomena The reason to consider needs from raw materials, formulations, and parts of the design and casting process. The selection of raw materials, formulations, determines the ultimate quality indicators of the parts. Such as ordinary anhydride-BPA type epoxy resin pouring member, the limit of its Tg of about 125 ℃, you must select the other curing agents, or other epoxy resins if further increase Tg. But even with a good raw material, a reasonable formula, if the casting process to select unreasonable, operating techniques, the workpiece is also impossible to achieve the required performance of the original design.
For easy pouring manufacturing problems and their causes, expert analysis considered the following aspects: First, the bubbles pouring pieces produce bubbles is a common phenomenon, within a range of quality control of the bubble is a relative concept, that only bubble size and the number of points, absolutely no bubble is not the marrow, the goal of quality control is to require fewer bubbles and small produce bubbles for many reasons, mainly due to the vacuum efficiency low vacuum or vacuum pumping degree rate up to less requirements, the resin, curing agent containing volatile too much, too much filler absorbent no pretreatment, curing reaction is too fast when casting implosion is formed, the viscosity of the mixture is too large; two is a defect, the defect can be said that a large bubbles, i.e. the bubble reaches a certain level called defective, the cause of the defects including castable viscosity too large to not fill the mold, mold Mifengbuyan produce leakage of part of the material, and the initial curing temperature is too high, the mixture gel fast; Third cracking cracking epoxy cast member has been epoxy casting technology is an important topic of research, especially due to the internal stress generated microfractures affect the quality of casting workpiece, casting parts mainly caused cracks pouring material selection and formulation design unreasonable (too brittle materials, casting pieces of hot and cold change cracking too big casting material shrinkage during curing, casting parts during the curing process to produce a large number of micro-cracks), of casting workpiece design or mold, embedded piece design unreasonable pouring member is formed inside the stress concentration point, releasing careless operation, local force is too large (due to the releasing material is not completely cured and demolding temperature is higher, the mechanical strength of the cured product is very low under the external force very easy to produce cracks), gel curing temperature is too high, the cooling rate is too fast in the workpiece after curing.
Must pay attention to another one of the reasons is that parts insufficient mechanical strength pouring insulators in electrical work, tend to be some external force, insulated rod support bar under tension, pressure, the bending force air switch, SF6 switch insulator by internal pressure, external mechanical strength can cause the insulation of fracture, bending, the quality of the bursting of the accident, parts mechanical strength caused mainly because of the material selection or recipes unreasonable, curing bad, the batching operation inaccurate measurement or curing time is too short and low curing temperature, bubbles, cracks, defects in casting parts design, the structure is irrational. China Association of epoxy resin industry experts said, and be mindful of) parts electrical properties mainly the performance of partial discharge, leakage, electrode breakdown, electricity life is too short to produce this kind of problem because casting pieces of mechanical strength is the lack of the insulators internal injury, casting bubbles, cracks, defects, material selection or formulation design unreasonable, such as excessive conductive ions in the material inappropriate choice of filler, electrical use harsh environment such as surface aging too fast deterioration , parts design unreasonable.
