The addition of magnesium oxide to neoprene has greater strength and wettability.
Metal oxides have four functions in chloroprene adhesives: acid absorbers, anti-scorch agents, vulcanizing agents, and resin reactants. Over time, neoprene will release trace amounts of hydrogen chloride, which can promote further decomposition of the polymer and corrode metals and natural fibers. Adding metal oxides can absorb hydrogen chloride to prevent further degradation.
The commonly used metal oxides are mainly zinc oxide and magnesium oxide. Magnesium oxide has functions such as acid absorption, pre-reaction, scorch prevention, and vulcanization, and is an indispensable component of chloroprene adhesives. The pre-reaction of magnesium oxide and resin can improve the heat resistance of the adhesive and prevent stratification and precipitation. The amount of magnesium oxide affects both the pre-reaction effect and the performance of the adhesive. As the amount of magnesium oxide increases, the high-temperature strength increases, but the glue is stable Sexuality is reduced. The addition of magnesium oxide can effectively speed up the drying of the adhesive film and greatly improve the initial bonding strength, which may be due to calcined light magnesium oxide or active magnesium oxide. Light magnesium oxide is a white amorphous powder, odorless and tasteless. The relative density is 3.58, the melting point is 28520C, and the boiling point is 36000C. It can gradually absorb carbon dioxide and moisture in the air to generate basic magnesium carbonate. Zinc oxide added to chloroprene adhesive can absorb acid, but it is not objective to think that it is a vulcanizing agent because chloroprene adhesives are mostly used at outdoor temperatures and will not vulcanize due to cooling, and they will precipitate at the bottom during storage. At the same time, zinc oxide can make the glue liquid turbid and make the glue film sticky, as if it is dry but not dry. It is used to bond polyurethane foam plastics. Zinc oxide will promote the aging of the material.
Based on the above reasons, zinc oxide can be eliminated. In fact, CR adhesives used in foreign electrical appliances no longer add zinc oxide, and the glue is both transparent and non-stratified. The required bonding strength can be achieved without zinc oxide, and it can also avoid scorching during rubber mixing, prevent the adhesive from gelling and precipitating during long-term storage, and will not cause phase separation of the glue liquid. If the chloroprene adhesive is used at high temperatures after bonding, it is beneficial to add a small amount (1 to 3 parts) of ultrafine activated zinc oxide.