The Role of PEG in Rubber

Polyethylene glycol (PEG) is a commonly used substance that has applications in various industries. In rubber, it is mainly used to neutralize the acidity of fillers, accelerate vulcanization and enhance crosslinking density. It has excellent water solubility and good compatibility with many organic components. It also has excellent lubricity, moisturizing properties, dispersing properties, and can be used as an anti-static agent and softener.

In general, PEG-4000 is used in rubber. If the molecular weight is too low, the compatibility is poor and it is easy to precipitate. Moreover, it is a liquid, which is not easy to add. If the molecular weight is too high, the number of alcohol groups per unit mass is less (low hydroxyl value), and the neutralizing effect of acid is worse. Because PEG-4000 has a solid flake-like molecular weight, it is easy to process and add, and it is less prone to precipitation. The medium molecular weight polymer has better compatibility with rubber, so PEG-4000 is generally chosen. Hai'an Petrochemical specializes in producing polyethylene glycol.

The following are the main functions of polyethylene glycol:

one Processing aid

It can improve the extrusion speed of rubber compounds, improve demolding properties, and make the finished product surface bright. It also helps to expel moisture during vulcanization. When used in tires and rubber molded products, Hainan Petrochemical PEG-4000 has good lubricating properties, making the finished product surface smoother. It can also be used as an internal demolding agent in the production process of natural rubber and synthetic rubber. The advantage is that it is non-volatile, does not produce ash change, and the mold remains clean after demolding. Moreover, the surface of the molded product is also made smoother and cleaner by its addition.

2. Sulfur activator

It serves to adjust the bonding performance between the rubber and fillers (especially white ones), and also has the function of lowering the Mooney viscosity and improving the vulcanization rate. It has a better activating effect on thiazole-type accelerators, which can improve the vulcanization speed and cross-linking degree, especially for EPDM white CB-reinforced extrusion microwave continuous vulcanization formulations. It is best not to use PEG in products bonded with metals.

3. Acid-activated fillers

In particular, it can be used as a dispersant for white carbon black to activate the vulcanization system and wet the surface of acidic fillers such as silica. One reaction is neutralization, and the other is similar to coating. Because acidic fillers will adsorb, please note that the adsorbent is the promoter. The amount used and the amount of acidic surface area per unit volume of the filler, etc. are proportional. We can basically understand that the acidic surface has been neutralized. Of course, other vulcanization reactions may also produce acids such as HS. Those are left to the zinc oxide to deal with.



4. Activated Dispersing Agent

As an activator and dispersant for various fillers and pigments in rubber compounds, it can reduce or eliminate the influence of fillers on vulcanization, make various additives disperse evenly and prolong the scorch time, thereby improving the physical and mechanical properties of rubber products. In various colored rubber products, it can make the products have vivid colors.

Because of its polar characteristics, it can also enhance the absorption of non-polar rubber (such as EPDM) to microwaves.

As the molecular weight of polyethylene glycol increases, its activity decreases moderately, while the modification of filler surface hydroxyl groups is slightly weakened. However, the deactivation of accelerator vulcanization is slightly weakened, which means that as the molecular weight increases, it helps stabilize vulcanization scorching and slightly weakens the reinforcing effect of the material on rubber.