What is the difference between internal and external plasticizing and what are their plasticizing principles?
The production of plastic products can not be separated from the use of plasticizers, because only the use of PVC resin production of plastic parts of the cost is too high, and often need to obtain a variety of different performance in the production process, and mixed with different plasticizers can achieve this “cost reduction and interest” purposes, but in the actual use of plasticizers, according to the form of plasticization Divided into internal plasticizing and external plasticizing two cases, here Aoshi editorial compiled for you the difference between internal plasticizing and external plasticizing and its plasticizing principle, for your reference.
First, the difference between internal plasticizing and external plasticizing
1, internal plasticizing
Internal plasticizing is a chemical plasticizing method, due to the second monomer and polymer chain segments have a stable chemical combination, so it is not drawn out by the medium, but from the process and cost considerations, the internal plasticizer cohesion is weaker, the use of temperature is narrower, and must be added in the process of polymerization, so it is usually used only for slightly flexural plastic products.
PVC environmental protection external plasticizer
External plasticizing is a physical plasticizing method, performance is more comprehensive, easy to produce and use, wide range of applications, but easy to migrate and volatile and loss. Most of the commonly used external plasticizers are ester organic compounds, usually no chemical reaction with the polymer, the interaction with the polymer at elevated temperatures and the polymer is mainly the role of swelling, and then with the polymer to form a solid solution. Plasticizers are usually referred to as external plasticizers.
Second, the principle of internal plasticizing and external plasticizing
1, the principle of internal plasticization
Plasticizing is the introduction of a monomer in the polymerization process of the second monomer, due to the second monomer copolymerization in the molecular structure of the polymer, destroying the polymer molecular chain of the degree of regularity, which reduces the degree of crystallinity of the polymer, reduces the intermolecular forces, increasing the plasticity. Such as block copolymerization, graft copolymerization and other methods.
Another type of internal plasticizing is the introduction of branched chains (or substituents or grafted branches) in the polymer molecular chain, and the branched chains can reduce the polymer chain to chain force, thus increasing the plasticity of the plastic parts.
P-phenylene environmental plasticizers
2, external plasticizing principle
External plasticizing is with the help of certain low molecular substances with solvation ability, mixed into the resin molecules, increasing the distance between the molecules in order to reduce the intermolecular gravitational force of the resin, equivalent to the use of mechanical methods of coercion, dispersed in the polymer need to be plasticized, and generally they do not react with the polymer, do not become a part of the polymer chain segments. The result of external plasticizing is a reduction in the intermolecular gravitational force, which makes the plasticized resin soft and reduces the processing temperature of the resin.