The vulcanization process of rubber products plays a crucial role in industrial production. However, this process often comes with a myriad of challenges. In this article, we will focus on 24 common issues encountered in the vulcanization of rubber products and provide corresponding solutions. Our aim is to assist manufacturers and engineers in gaining a better understanding of these challenges and effectively addressing them.
The vulcanization of rubber products is a complex and precise process that directly impacts the quality and performance of the final products. By delving into the study and resolution of potential problems during vulcanization, we hope to enhance the stability, durability, and overall performance of rubber products, thereby advancing technological progress in the rubber industry.
1. Rubber products are lacking glue (shown as the appearance of the rubber body is incomplete and not fully filled)
Inaccurate weighing of the rubber material; poor fluidity of the rubber material; improper placement of the rubber material; blocked glue injection hole; glue overflow; insufficient injection pressure; sudden power outage before the injection/injection pressure is completed; the actual amount of glue used does not match the process; The rubber material of the injection press is baked unevenly; the same product has different process parameters on different machines; the injection hole is too small.
2. Degumming of rubber products (shown as the rubber body and the skeleton are separated from each other and not bonded)
The grease on the surface of the skeleton has not been cleaned before gluing; (shown as the adhesive frame is not sticky)
Adhesive failure: the surface coating or primer is not dry; it has been stored for an extended period of time; there is a sudden power outage before glue injection is started after the mold is closed; unqualified adhesive is used; the skeleton is installed in the high-temperature mold for too long.
The surface of the skeleton coated with adhesive is contaminated: dust prevention measures are not taken and it is contaminated by dust and release agents. The skeleton is not removed during equipment maintenance and is contaminated by oil. Clean gloves are not replaced when installing the skeleton;
The adhesive on the surface of the skeleton is too thick or has accumulation; the mold temperature is too high or too low; the mold sealing is not tight; the glue injection hole is too large; secondary processing.
3. Rubber products have rotten edges (scorched edges) (shown in defects such as wrinkles and delamination in the parting part of the mold cavity)
The mold temperature is too high; the distance between the tearing grooves of the edge tearing mold is unreasonable; and the exhaust is improper.
4. Impurities (shown as the presence of different materials or other objects on the surface of the rubber body)
The mixed rubber contains cooked rubber; the cooked rubber on the mold has not been cleaned; the glue injection holes have not been cleaned; internal impurities (impurities in the raw materials themselves);
5. Rubber products are stuffy (shown as a little sticky, spongy rubber on the rubber body; the mixed rubber is not mature)
Insufficient exhaust times; no exhaust holes or rubber tracks designed on the mold; insufficient exhaust delay; improper feeding method; too much rubber; improper exhaust method.
6. Bubbles (another manifestation of stuffiness, forming a bag on the surface of the rubber body, filled with air)
The surface of the skeleton coated with adhesive is contaminated (gradually degummed with a bubble); the adhesive on the surface of the skeleton is not completely dried; the moisture in the raw materials exceeds the standard; there is too much moisture in the mixed rubber.
7. Insufficient sulfur in rubber products (shown as mesh, pores inside the rubber product, or bulges on the surface of the product)
The process vulcanization temperature is too low; the process vulcanization time is insufficient; the loading and unloading time of the mold is too long, causing the mold temperature to drop; the T90 of the mixed rubber is too long; the operator does not produce according to the process vulcanization time (shorten the vulcanization time).
8. Rubber products are over-vulcanized (shown as rubber products have scorch or surface wrinkles)
The vulcanization temperature is too high or the time is too long;
9. Rubber products shift (shown as the parting surfaces of the product cannot transition smoothly and are staggered from each other)
The guide posts or guide post holes of the mold are worn, causing the matching gap between them to increase; the upper and lower molds of the mold have no error-proofing technology when closing the mold. The mold can be closed by turning 180 degrees without damaging the mold. ; The guide pillars of the mold fall off; for skeleton products, the positioning pins in the mold cavity fall off or are improperly matched.
10. Skeleton making of rubber products (shown by skeleton deformation, fracture, excessive burrs, etc., resulting in an unqualified skeleton)
The frame or mold cavity is unqualified; the frame is not placed correctly; the mold structure is unreasonable, making it difficult to place the frame.
11. Rubber products have leaky skeletons (shown as no rubber in the rubber-covered part of the skeleton)
The frame or mold cavity is unqualified; the positioning pins in the mold cavity fall off or are improperly matched; when the mold is installed, the upper and lower molds of the mold are not properly matched.
12. Deformation of rubber products (shown as the product losing its original shape)
The material of skeleton raw material is poor; the sandblasting time is too long or the sand grains are too coarse (plastic shells, aluminum shells, pipes with larger inner diameter and thinner wall thickness); the matching gap between the mold cavity and the skeleton is too large; the glue injection pressure is too high; Pure rubber or plastic products are placed improperly.
13. The thickness of the rubber edge of rubber products
The amount of glue is too much; the upper and lower mold mating surfaces (parting surfaces) of the mold are worn; the mold has no rubber track or the rubber track is unreasonable; the clamping pressure is too small; the mold parting surface is not matched properly (caused by design).
14. The rubber product mold is dirty (shown as inconsistent color, dirt, and lack of luster on the surface of the product)
There is dirt in the mold cavity; the adhesive on the surface of the skeleton is applied too thickly and flows into the mold cavity during vulcanization, causing the rubber to stick to the mold cavity (causing the adhesive to stick to the mold cavity); the rubber material causes dirt to easily occur in the mold cavity; it is easy to use water-based release agents Produces mold dirt.
15. Mold sticking of rubber products (shown by the formation of irregular rubber defective areas on the surface of the rubber body)
The mold temperature is too low; the rubber formula is poor (such as the internal release agent content is small); the skeleton adhesive is not completely dried.
16. The injection hole of the rubber product is too deep (shown as an obvious pit on the surface of the rubber body)
Unreasonable design; improper exhaust; excessive mold temperature; improper demoulding.
17. The rubber product skeleton is broken
The glue injection pressure is too high or the tensile strength and elongation of the skeleton are too low, such as 181H, 515c shells, etc.;
The matching gap between the mold cavity and the frame is too large.
18. Delamination of rubber products (shown by the phenomenon of non-adhesion between rubber and rubber in parts of the rubber body)
The heat refining temperature of the rubber material is too low and the number of thin passes is not enough; the vulcanization temperature is too high; and the exhaust is improper.
19. Rubber products are damaged by prying (shown as the rubber body or skeleton of the part being partially damaged in the later stage of vulcanization)
The mold structure is unreasonable; the demoulding equipment is unreasonable; the demoulding method is improper.
20. Mold marks and unevenness of rubber products (shown as obvious, irregular pitting, scratches, and uneven unevenness on the surface of the rubber body)
There are traces on the mold cavity; there are hard objects in the rubber material.
21. Shrinkage and cracking of rubber products (shown as cracks on the surface of the rubber parting part)
The mold temperature is too high; the mold mating surface is improper.
22. Rubber products are torn (shown as being torn off at the protruding parts of the product)
The tear strength of the rubber is poor; the vulcanization demoulding or trimming method is improper.
23. Rubber products are burned (shown as irregular marks on the rubber surface)
The temperature is too high; the speed of loading the skeleton or rubber is slow; the fluidity of the rubber is poor; the exhaust time is too long; the injection pressure is low and the speed is slow.
24. Cracks in rubber products
The mold temperature is too high; the tear strength of the rubber material is poor.
Pay attention :
Hydraulic products: Defects such as lack of glue, impurities, bubbles, and stuffiness in the sealing ring are never allowed to exist;
Bushing products: There should be no rubber material blocking the pipe hole, and there should be no burrs in the skeleton hole ;
Products with threads: the threads cannot be damaged or crushed;
The surface of the galvanized skeleton must not damage the surface layer and pay attention to the color change of the galvanized layer after vulcanization.
