Fluorescent whitening agent has always played the role of “monosodium glutamate” in plastic processing. The addition of a few ten thousandths can whiten and brighten plastic products and improve the appearance of plastics.
There are many ways to add whitening agents, but their use methods are mainly divided into three categories: dry whitening, wet whitening and masterbatch whitening.
Dry whitening
Plastic dry whitening is to add a certain amount of fluorescent whitening agent dry powder directly to the plastic substrate before molding, mix with the plastic substrate first, and extrude the mixture when the extruder reaches the plastic melting temperature. Melt into the screw to make the plastic whitening agent evenly distributed in the melt, and finally carry out granulation or compression molding.
Dry process plastic whitening agent is mainly used for injection molding whitening of rigid PVC, polyethylene, polypropylene, ABS and other thermoplastic resins. Fluorescent whitening agents used in dry whitening agents are relatively cheap, but have the disadvantages of large dust scattering and environmental pollution.
Incident whitening
In order to improve the dispersion effect of wet whitening, it is sometimes necessary to add a certain amount of binder to the plastic whitening agent, so that the plastic whitening agent can better adhere to the surface of the material, so as to reduce its dust flying and pollution.
The plastic brightener can also be dispersed in the auxiliary solution and added in batches in the form of auxiliary dispersion. For example, it can be used in soft polyvinyl chloride (PVC), which can be formulated into 10% phthalic acid. After the dioctyl ester plasticizer solution, it was added in batches.
In wet whitening, the plastic whitening agent is a finely dispersed slurry, which has the disadvantage of being sticky because a non-volatile organic solvent is mixed into the plasticizer. Hony Chemical generally recommends this whitening method for soft PVC.
Masterbatch whitening
At present, the use of “masterbatch” in plastics has become an important means of plastic coloring. When using color masterbatch, as long as the color masterbatch and resin are mixed evenly in proportion, they can be directly used for molding plastic products.
A small amount of stirring only needs to be done by hand. In the case of a large amount of processing, in order to ensure the dispersibility of the masterbatch, mechanical stirring can be used. After the color masterbatch is mechanically mixed with the resin plastic, it can be sent to the injection molding machine with the pre-molding device, and the color is pre-molded at the same time.
Precautions for use
First，the amount of fluorescent whitening must be well controlled. The amount of whitening agent added is not as good as possible. Excessive amount will make the plastic yellow.Second, the brightener and raw materials must be stirred evenly.
Here are a few ways to use plastic brighteners, and the specific ones you need to choose according to your own situation. If you have any questions about the use of plastic brighteners, please feel free to leave a message on the message board.
Post time: Mar-26-2022