What physical-mechanical improvements of the polymer mixtures are obtained with the use of nanofillers

In the production of recycled polymers or compounds with virgin polymers, some recipes require the addition of a certain percentage of mineral fillers in order to modify some characteristics.

Among the most used are calcium carbonate, talc, glass fiber and mica, in the form of powder, granules or fiber, which are dispersed during mixing with the polymer.

Talc and calcium carbonate are normally added in percentages ranging from 10 to 50% to modify some characteristics of polymers, such as mechanical resistance to compression, workability, reduction of expansion, improvement or reduction of fluidity or simply for economic reasons.

The use of mineral fillers in polymer mixtures also brings with it some problems to be kept in mind, depending on the percentages of use and the type of filler.

In general, it can be said that the density of the polymer mix increases, the brightness of the colors decreases, the fragility of the product can become consistent and the wear of the machines tends to increase.

Many of these negative characteristics during processing, but which also reverberate on finished products, can be resolved using nanofillers.

The latter can be defined as a new class of composite materials, consisting of a polymer matrix and particle reinforcements, having at least a nanometer size.

These nanofillers can be defined, to all intents and purposes, as nanofillers and the three categories are classified according to their structure:

• 3D (isodimensional) nanofillers defined as nano particles or nanospheres with a size less than 100 nm.

• fibers or tubes with a diameter of less than 100 nm. such as, for example, carbon nanotubes.

• nano-layers, characterized by a single dimension of the order of nanometers, typically occur in the form of stratified inorganic crystallites in which each layer has a thickness of some nanometers, while the other two dimensions can reach even thousands of nanometers (for example nanoclays).

The advantage of nanofillers, among others, is the better dispersion than mineral ones, with better adhesion to the matrix and better saturation of spaces.

In addition, we can mention another fundamental advantage that concerns the improvement of the physical and mechanical performance of the polymer mixture, with a low percentage of use.

While, as we have said, to modify the characteristics of the polymeric mixtures through mineral fillers, percentages varying between 10 and 50% are used, with nanofillers the percentage of use is around 5-10%.

This reduced percentage leads to limiting the increase in density and improving workability compared to other traditional filling systems.

If we consider a polymer mixture with a 5% of nanofillers, we can say that the physical-mechanical properties can be superior, compared to the base polymer and also to the same loaded one with a mineral filler.

In particular we will have:

• greater resistance to abrasion and impact

• greater rigidity

• decrease of the thermal expansion value

• greater dimensional stability

• reduced gas permeability

• better resistance to solvents

• less heat release during combustion

• ease of recyclability

Furthermore, there are aesthetic advantages using the nanofillers, which are comparable to the use of the original polymer alone, as a better distribution in the mass creates a better quality superficial compared to the use of traditional fillers.

In particular we can mention a better optical transparency, less roughness, better color brilliance and better dimensional stability of the product over time.

Automatic translation. We apologize for any inaccuracies. Original article in Italian