ISO 9001:2000 Certifications
Closures standard thread profiles
There are two most popular thread profiles for thermoplastic closures which called "unscrewing" or "stripped" types. There is no good or bad threads. Each of them have their own advantages and disadvantages. Which is suitable usually dictated by their end application and usage. Both types are briefly explained as below:
The features of an unscrewing thread
1).During the molding operation, a mechanism in the molds unscrews the closure. This action protects the integrity of the thread. Therefore the thread profile can better controlled and the closure wall is less distorted by the application torque.
2).During the capping operation, the application torque is better transformed into vertical forces that compress the sealing system against the bottle neck.
3).When an unscrewing cap is lined the liner is usually glued since it can not be restrained properly by the thread.
The Disadvantage of unscrewing Thread
1).This type of thread is not ideal for multiple liners.
2).Unscrewing caps limit the closure design (by example an interrupted thread cannot be unscrewing in a molds). Also, the molds are more complexed and more expensive to produce.
3).There is no restriction on the selection of the raw materials that can be used to produce the closures.
The features of a "Stripped" thread
1). During the the molding operation, the closure is simply pushed off the molds, without the unscrewing action. Evidently, there is a compromise in the design of the thread profile to allow the cap to "strip" during the molding operation and to give adequate cap retention on the bottle neck.
2). The liners do not have to be glued, they can simply be retained by the threads.
3). Stripped threads are a good solution when Gosdar Mfg. Co., Ltd want to use multiple liners and makes possible some designs (i.e.: Interrupted threads).
4). The choice of raw materials to molds this type of closures is limited (polyethylene and polypropylene are the most popular choices).