Before each plastic is processed, if the polymer has been selected, the next thing to consider is what kind of additives are used, and the amount of it. Whether the plastic additives are selected correctly directly affects the processing, product performance and service life. When selecting auxiliaries, there are generally four main issues to consider.
1, the compatibility of additives and polymers The so-called compatibility means that the additives and polymers can be mixed together well and evenly, without phase separation and precipitation performance. Auxiliaries must be stable in the product for a long time, so as to play its due role, so it should be as far as possible to choose auxiliaries with good compatibility with polymers. However, there is only a specific range of compatibility between various auxiliaries and a given polymer, beyond which the auxiliaries precipitate.
2, the adaptability of additives to processing conditions For example, if the processing of polymers needs to be carried out at high temperatures for a long time, when selecting additives, it is necessary to consider whether it can adapt to such processing conditions. If the processing temperature of polypropylene is relatively high, the stabilizer that does not decompose, does not volatilize or less volatilize should be selected at this temperature; Choose a colorant that does not decompose and fade at high temperatures. The same polymer, due to the different processing methods used, the additives required are not the same.
3, give full play to the synergistic effect of a plastic often use a variety of auxiliaries, these auxiliaries in a system, often interact with each other, if properly coordinated, when used with synergistic effect, called "synergy". For example, the ultraviolet absorber 2 hydroxy-4-octyloxybenzophenone and the antioxidant tri-decyl phosphite when mixed, has a significant synergistic effect.
On the contrary, if the selection is improper, the use of a reduction effect, it is said. Antagonism ". For example, when carbon black and amine antioxidants are used in polyethylene, they have an antagonistic effect and weaken the original stabilizing effect of each other.
4, the use of products to restrict the use of additives the choice of plastic additives is often limited by the use of products, such as plastic products always have to contact with people, especially those food packaging and blood transfusion materials, etc., more closely related to human health, so you must choose non-toxic exploration: for products often in contact with oil or water. Additives that are not easy to be extracted by oil or water must be selected.
