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26
2022
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01
New Pultrusion Process for Epoxy Core Rods
One of the most important components of organic composite insulators is the core rod. This not only ensures the fire resistance of the composite insulator but also serves as a component that withstands the mechanical load of the composite insulator. Its quality is a crucial guarantee for the reliability of the composite insulator.
One of the important components of organic composite insulators is the core rod. This not only guarantees the fire resistance of the composite insulator but also bears the mechanical load of the composite insulator, making its quality a crucial assurance for the reliability of composite insulators. The production of composite insulators has led manufacturers to propose more specific and higher requirements. At the same time, core rod manufacturers are continuously introducing new processes to improve product quality. In recent years, significant progress has been made in the development and production processes of heat-resistant core rods, acid-resistant core rods, transparent core rods, and injection-extruded core rods, particularly in vacuum extrusion and injection extrusion processes. This article first introduces the development of extrusion processes and the characteristics of core rods produced by different processes.
Progress in epoxy core rod extrusion technology in our country:
Pultrusion molding technology began in the 1950s, with its first patent registered in the United States. There were 60 applications and 70 developments, with rapid growth in the 1980s. In recent years, pultrusion products have maintained a growth rate of over 10%. The extrusion molding process has gained attention from peers around the world, with various extrusion equipment and processes emerging one after another. For example, vertical extrusion, horizontal extrusion, bent steel profile extrusion, injection extrusion, etc. The rise of epoxy extruded core rods for insulating porcelain and composite insulating porcelain occurred simultaneously in the early 1980s. Tensioning equipment includes ceramic sand machines, pre-forming molds, epoxy resin immersion tanks, forming molds, and traction machines. The process involves glass fibers passing through a sand-coating machine and pre-forming (some companies do not have this), followed by immersion in an open tank at normal pressure to soak glass fibers before being pulled by a traction machine after solidification.
Vacuum-assisted extrusion process:
In 2001, to address issues such as high air speed and large opacity in ordinary extruded core rods, a vacuum-assisted extrusion process was developed. This process features multiple immersions and vacuum assistance to minimize contact area between glue and atmosphere to improve product performance. Glass fibers are divided into several layers; after initial immersion they enter a pre-forming mold with adhesive containing certain amounts of adhesive glass fibers that enter a vacuum soaking system to remove air pockets under vacuum conditions while reducing air pockets for complete penetration.
This process has achieved better results in relatively dry environments like Northwest China; products produced have shown significant improvements in several aspects:
(a) Fewer air pockets lead to higher product transparency and easier elimination of product defects (such as fabric flaws, debris, insufficient adhesive).
(b) Multi-layer immersion reduces contact area between adhesive and atmosphere affecting product under environmental conditions.
(c) Complete soaking of glass fibers through multiple vacuum-assisted soaks;
(d) These aspects ensure that vacuum-extruded cores are more stable than ordinary extrusions.
Core rod issues and outlook on extrusion technology:
Currently, the production process for composite insulator core rods in our country mainly relies on traditional methods; the biggest issue is that product characteristics vary significantly with time and seasons. Core rod manufacturers need to strengthen control measures while closely monitoring changes in product characteristics. A relatively simple method is timely monitoring of high-temperature mechanical properties and color changes of products. Additionally, since most core rods are opaque, manufacturers must work hard to eliminate defects such as dead ends, debris, insufficient adhesive application or hard glue lumps as well as partial cracks. Thirdly it is essential to enhance control over glass fibers and raw materials especially curing agents while standardizing processing procedures. Fourthly it is necessary to establish dedicated standards for deep rods used in composite insulators; current technical conditions referenced are still incomplete.
Core rod
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