The market for plastic bottle cap molds is characterized by huge demand, numerous market segments, and intense competition. An increasing number of manufacturers are entering this space, driving the continuous evolution of diverse and differentiated plastic bottle cap designs. However, it is often overlooked that these molds are highly susceptible to rust. What, then, are the common causes of rust formation on plastic bottle cap molds?
A common cause of rust is the release of gases resulting from the overheating and decomposition of the molten plastic material. If this occurs during a pause in production, the corrosive gases present in the vicinity can cause the mold to rust. Therefore, after stopping the injection molding process, the mold must be wiped clean with a soft cloth and kept closed to prevent corrosion caused by gases from nearby injection molding machines. When closing the mold, remember to apply grease; do not neglect to seal the gate. For prolonged shutdowns, spray a rust inhibitor into the mold cavity-but first, wipe the cavity clean with a soft cloth to ensure there are no existing rust spots.
Any carbide residue adhering to the mold cavity surface that could lead to rust must be removed promptly. Carbides precipitated or generated during the molding process often cause wear or corrosion; if detected, they should be wiped away immediately with a dry cloth.
While the electroplated layer inside the mold cavity helps prevent rust, it is not entirely effective; corrosive gases can sometimes penetrate the plating through microscopic pores, causing deep corrosion. Frequent wiping of the mold is essential to prevent rust from forming on the plated surface.
Circulating cooling water through the mold can also lead to rust. If the mold is cooled below the freezing point, atmospheric moisture will condense into water droplets on the mold surface, causing rust if not wiped away. Although condensation may not occur during the active molding process, it forms immediately after production stops. Therefore, try to avoid interrupting production; if a stoppage is necessary, shut off the cooling water and wipe the mold surface dry. When the aforementioned situations arise, it is essential to ensure timely protective measures are taken to prevent the plastic bottle cap mold from rusting easily.