What is the relationship between plastic additives and plasticizers?
Plastic additives, also known as plastic additives, are some compounds that must be added to polymers (synthetic resins) to improve their processing properties or to improve the performance of the resin or plastic itself is insufficient.
Plastic additives are important for improving the performance of the resin itself, for example, in order to reduce the molding temperature of polyvinyl chloride resin, so that the products are soft to add plasticizers. In order to prepare lightweight, anti-vibration, heat and sound insulation foam and to add foaming agents; some plastics are very close to the thermal decomposition temperature and molding process temperature, without adding heat stabilizers can not be formed.
Therefore, plastic additives in the plastic molding process occupies a particularly important position. But the traditional plastic additives are mostly petroleum-based sources, with the progress of people’s awareness of environmental protection and safety awareness, bio-based plastic additives show higher safety and environmental protection and other characteristics, plastic additives of environmental transformation has become the trend.
In all plastic additives, plasticizers account for a very large proportion, is the current plastic rubber use zui large amount of additives, 90% for PVC resin.
The main role of plasticizers is added to polymer materials to improve their plasticity, can change the nature of the polymer, increasing its plasticity, flexibility, stretching and other properties, making it easy to process.
In fact, almost all thermoplastic polymer processing will use plasticizers to a greater or lesser extent. The essence of thermoplastic polymer processing is to increase the activity of polymer molecules by heating, weakening their intermolecular forces, thus making them plastic.
However, for some polar polymers with high intermolecular forces and unstable to heating, it becomes very difficult to mold by heating alone, and the strong intermolecular forces make the finished products of such polymers hard, inelastic and flexible without adding plasticizers or in inadequate amounts.
To make flexible PVC products, a sufficient amount of plasticizer must be added. Sometimes the amount added is even more than 50% of the total mass of the product, for example, medical PVC products, toys with 35% to 40%, food packaging products about 28%, the amount added varies.
The appearance of plasticizers by reducing the glass transition temperature of the polymer, melting temperature and elastic modulus of elastomers, so that the tensile properties, flexibility, elongation of the product better.
Plasticizers plasticizing mechanism is mainly through the volume effect and shielding effect of two aspects to achieve.
1. Volume effect
This effect is formed because the addition of non-polar plasticizers will increase the distance between the polymer molecules, the molecular force between the molecules decreased, which reduces the van der Waals force between the resin molecules, thus reducing the melt viscosity of plastics. This effect will increase with the addition of plasticizers, and the structure of plasticizers will also have an impact on the plasticizing efficiency.
2. Shielding effect
This effect is caused by polar plasticizers. The addition of polar plasticizer makes the interaction between polar plasticizer and polymer enhanced, which reduces the polar connection between polymers and achieves the effect of reducing the melt viscosity.
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