The main function of the optical brightener is to whiten and brighten plastic and improve the appearance of plastics. Optical brighteners in plastics are added mainly in three methods: the dry whitening method, the wet whitening method, and the masterbatch whitening method.
Here is a brief introduction:
1. Dry whitening method:
The dry whitening method is to add a certain amount of optical brightener dry powder directly to the plastic substrate before molding, and mix evenly with the plastic substrate. When the extruder reaches the melting temperature, the mixture will be extruded into the screw firing melting. It will make the optical brighteners uniformly distributed in the melt, and then finally pelletize or compression molding.
The dry whitening method mainly applies to rigid PVC, polyethylene, polypropylene, ABS, and other thermoplastic resins for injection molding whitening. The dry method whitening agent is relatively cheap in cost. But it has the disadvantage of large dust dispersion and environmental pollution.
2. Wet whitening method
In plastic whitening processing, in order to improve the dispersion effect, sometimes it is also necessary to add a certain amount of binder, such as butyl stearate, to the plastic whitening agent. This assures that the whitening agent better adheres to the surface of the material and also reduces its dust pollution.
The wet whitening method mainly applied to soft or flexible PVC. For example, it can be formulated into a 10% solution of dioctyl phthalate plasticizer and then added in batches.
3. White masterbatch method
At present, white masterbatch has become the main method for whitening plastics. It is a mixture of pellet substances of fluorescent whitening agent or pigments with the resins.
When using white masterbatch, just mix the masterbatches and resin evenly in proportion. And then use it directly for molding plastic products.
The most commonly used optical brighteners in plastics are OB, OB-1, FP-127, KCB, KSN, etc.
For more information, please feel free to contact us via: sales@obachemical.com
