Classification of rubber formulations and post-curing treatment of rubber products
1. Basic formulation (standard formulation)
The basic formulation, also known as the standard formulation, is generally used for the identification of raw rubber and compounding agents.
2. Performance formulation (technical formulation)
The formulation design aimed at achieving certain performance requirements for rubber products, with the goal of meeting product performance and processing requirements, enhancing certain characteristics, etc. Performance formulations should comprehensively consider the combination of various properties based on the basic formulation to meet the usage conditions of the products.
3. Practical formulation (production formulation)
The practical formulation, also known as the production formulation, often encounters some process issues when the performance formulation developed under laboratory conditions is put into production, such as poor dispersion of compounding agents during mixing, short scorch time of the rubber compound, excessive expansion of the die during extrusion, and sticking to the rollers during calendering.
Rubber products often require certain post-treatment after curing to become qualified finished products. This includes: ① Trimming and finishing of rubber molded products to ensure a smooth surface and that the dimensions meet requirements; ② Processing through some special techniques, such as surface treatment of products to enhance the performance of products for special purposes; ③ For products containing fabric skeletons, such as belts and tires, thermal stretching and cooling, and cooling under inflation pressure after curing are required to ensure the stability of product dimensions, shapes, and good performance.
1. Trimming of molded products after curing, Dongguan Debao Rubber Products Factory
During the curing of rubber molded products, the rubber material will inevitably flow out along the parting surface of the mold, forming flash, also known as burrs or flash edges. The amount and thickness of the flash depend on the structure, precision of the mold, the parallelism of the platens of the flat vulcanizing machine, and the amount of excess rubber. Currently, products produced with edge-less molds have particularly thin flash, which can sometimes be removed during demolding or can be easily wiped off. However, this type of mold is relatively expensive and prone to damage, and most rubber molded products require trimming after curing.
1. Manual trimming
Manual trimming is an ancient method of trimming, which includes manually using punches to cut the rubber edges; using scissors, scrapers, and other tools to remove the rubber edges. The quality and speed of manually operated trimmed rubber products can vary from person to person, and the trimmed products' geometric dimensions must meet the requirements of the product drawings, without scratches, abrasions, or deformation. Before trimming, it is essential to clearly understand the trimming areas and technical requirements, master the correct trimming methods, and use the right tools.
2. Mechanical trimming
Mechanical trimming refers to the use of various specialized machines and corresponding process methods to trim rubber molded products. It is currently the most advanced trimming method. Dongguan Debao Rubber Products Factory
(1) Mechanical punch trimming uses pressure machinery and molds to remove the rubber edges of the products. This method is suitable for products and their rubber edges that can be placed on the mold or punch base, such as bottle stoppers, rubber bowls, etc. For products with a high rubber content and low hardness, impact cutting is generally used to trim the edges, which can reduce uneven edges and side depressions caused by the product's elasticity; for products with a low rubber content and high hardness, direct cutting with a knife edge mold can be used. Additionally, punching can be divided into cold cutting and hot cutting; cold cutting refers to cutting at room temperature, requiring higher cutting pressure and better cutting quality; hot cutting refers to cutting at higher temperatures, and care should be taken to prevent prolonged high-temperature contact with the product, which can affect product quality.
(2) Mechanical cutting trimming is suitable for trimming larger-sized products, using cutting tools. Each cutting machine is specialized, and different products use different cutting tools. For example, after tire vulcanization, there are rubber strips of varying lengths at the air vent and exhaust line areas, which must be trimmed using a grooved tool while the tire is rotating.
(3) Mechanical grinding trimming is typically used for rubber products with inner holes and outer circles, usually employing grinding methods. The grinding tool is a grinding wheel with a specific particle size, and the precision of grinding trimming is relatively low, resulting in a rough surface that may contain residual sand particles, affecting the usage effect.
(4) Low-temperature shot blasting trimming is suitable for fine products with high trimming quality requirements, such as O-rings and small rubber bowls. The products are rapidly cooled below the brittle temperature using liquid nitrogen or dry ice, and then metal or plastic pellets are sprayed at high speed to shatter and remove the flash, completing the trimming.
(5) Low-temperature brushing trimming uses two nylon brushes rotating around a horizontal axis to brush off the rubber edges of the frozen rubber products.
(6) Low-temperature tumbling trimming is the earliest adopted method of frozen trimming, utilizing the impact force generated by the rotation of the tumbler and the friction between products to cause the flash of products that have been frozen below the brittle temperature to break and fall off. The tumbler is generally octagonal in shape to increase the impact force on the products inside, and the rotation speed of the tumbler should be moderate. Adding abrasives can improve efficiency. For example, the trimming process for rubber plugs of electrolytic capacitors uses low-temperature tumbling.
(7) Low-temperature vibration trimming, also known as vibration freezing trimming, involves the products undergoing spiral vibration in a circular sealed box, resulting in strong impacts between the products and between the products and abrasives, causing the frozen brittle rubber edges to break off. Low-temperature vibration trimming is better than low-temperature tumbling trimming, with a lower product damage rate and higher production efficiency.
(8) Low-temperature swinging and shaking trimming is suitable for small or micro-sized products or micro rubber products containing metal skeletons, used to remove rubber edges from product holes, corners, and grooves along with abrasives.
(8) 低温摆动、抖动修边对小型或微型的制品或含有金属骨架的微型橡胶制品适用，与磨蚀剂一起修去产品孔眼、边角、槽沟中的胶边。 |
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