Haftvermittler - primer per Wittfoht, Kunststofftechnisches WB
Definition: a coating applied to a substrate to improve adhesion


For future reference, you can help us help you by providing some context. Sperreigenschaft + plastic containers (your previous question) doesn't provide much to go on. You should quote at least the sentence in which the term occurs, overall context such as intended target audience (is this marketing material, a data sheet, etc.) also helps others provide you with intelligent, meaningful suggestions. Generally these text do not constitute materials that would compromise the national security if they were revealed. So, PLEASE, a bit more context!