What is the difference between internal and external plasticizing and what are their plasticizing principles?

Quick answer: UV monomers and oligomers are usually chosen by viscosity, adhesion, flexibility, shrinkage, and cure speed as a package. The most reliable formulas come from balancing those properties rather than maximizing only one.

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
2、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.

Flame retardant plasticizers of the same series

Lcflex® T-50	T-50; ASE	CAS 91082-17-6
Lcflex® ATBC	Acetyl tributyl citrate	CAS 77-90-7
Lcflex® TBC	Tributyl citrate	CAS 77-94-1
Lcflex® TCPP	TCPP flame retardant	CAS 13674-84-5
Lcflex® DOTP	Dioctyl terephthalate	CAS 6422-86-2
Lcflex® DEP	Diethyl phthalate	CAS 84-66-2
Lcflex® TEC	triethyl citrate	CAS 77-93-0
Lcflex® DOA	Dioctyl adipate	CAS 123-79-5
Lcflex® DOS	SEBACIC ACID DI-N-OCTYL ESTER	CAS 2432-87-3
Lcflex® DINP	Diisononyl Phthalate	CAS 28553-12-0/685 15-48-0
Lcflex® TMP	Trimethylolpropane	CAS 77-99-6
Lcflex® TEP	Triethyl phosphate	CAS 78-40-0
Lcflex® TOTM	Trioctyl trimellitate	CAS 3319-31-1
Lcflex® BBP	Bio-based plasticizers, High-efficiency plasticizer
Lcflex® TMP	Trimethylol propane	CAS 77-99-6
Lcflare® TCEP	Tris(2-chloroethyl) phosphate	CAS 115-96-8
Lcflare® BDP	Bisphenol-A bis(diphenyl phosphate)	CAS 5945-33-5
Lcflare® TPP	Triphenyl phosphate	CAS 115-86-6

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How buyers usually evaluate UV monomers and resin systems

Most successful UV formulations are built by choosing the backbone first and then tuning the reactive monomer package around the substrate, cure method, and end-use stress. That usually produces a more stable result than choosing materials by viscosity or price alone.

• Start from the final property target: hardness, flexibility, adhesion, and shrinkage rarely point to exactly the same raw-material package.
• Screen the reactive package as a whole: oligomer, monomer, and photoinitiator choices interact strongly in UV systems.
• Use viscosity as a tool, not the only decision rule: the easiest-processing material is not always the one that performs best after cure.
• Check the real substrate: plastic, metal, label film, gel systems, and coatings can reward very different polarity and cure-density balances.

Recommended product references

• CHLUMIFLEX ATBC: A practical non-phthalate plasticizer reference for application and compliance screens.
• CHLUMIFLEX DOTP: A standard terephthalate-plasticizer benchmark in flexible-plastics applications.
• CHLUMIFLEX DBP: A conventional plasticizer comparison point in broader plasticizer discussions.
• CHLUMICRYL IBOA: A strong low-viscosity monomer reference when hardness and good flow both matter.

FAQ for buyers and formulators

Can one UV monomer or resin solve every formulation problem?
Usually no. Commercially strong formulas depend on how several components work together to balance cure, adhesion, flow, and durability.

Why should monomers be screened together with oligomers?
Because monomers can change viscosity, cure rate, shrinkage, and substrate behavior enough to alter the final ranking of the same backbone resin.