Calcium Carbonate Boosts Plastic Film Performance and Sustainability

Calcium carbonate, known for its low cost, white color, and excellent overall performance, is widely used as an inorganic filler in plastic films. Forming calcium carbonate into masterbatch for plastic film production offers advantages such as simplifying the process, improving mixing efficiency, enhancing production output, and reducing dust dispersion.

Characteristics of Calcium Carbonate as Plastic Film Filler

As a filler for polymer materials, calcium carbonate can increase the material's dimensional stability, stiffness, heat resistance, and reduce costs. But it will also increase its density, and if used improperly, it can lead to a decrease in mechanical properties such as material strength, impact resistance, toughness, and glossiness.

Calcium carbonate powder, as a filler for thin film materials, is a hydrophilic inorganic compound with hydrophilic hydroxyl groups on its surface, exhibiting strong alkalinity. The hydrophilic and oleophobic properties of calcium carbonate result in poor affinity with organic polymers, easy aggregation, uneven dispersion within the polymer, and interface defects between the two materials, leading to poor direct application results. As the filling amount increases, these drawbacks become more apparent, such as excessive filling that may even render the product unusable. Therefore, we need to modify the calcium carbonate.

The Influence of Calcium Carbonate on the Properties of Thin Films

(1) In Terms of Mechanical Properties

Using ultrafine heavy calcium carbonate to modify LLDPE/mPE. The results showed that adding 5% calcium carbonate increased the dart impact strength of the film by 13.2%, the elongation at break by about 5%, and the tensile strength slightly increased.

(2) In Terms of Thermal Performance

After adding fillers, due to the good thermal stability of calcium carbonate, the thermal expansion coefficient and shrinkage rate of the product can be reduced, and the thermal stability of the product increases with the increase of fillers.

(3) Other Performance

Polyethylene (LDPE, LLDPE) anti fog film modified with materials such as calcium carbonate and talc powder has a longer non drip retention period. Pre mixing with anti fog agents can improve the anti fog performance of the film. Compared to the blank film, the ability of calcium carbonate modified polyethylene film to block infrared and ultraviolet rays has been improved to a certain extent. Adding calcium carbonate film can also promote film degradation and play a positive role in environmental protection.

In addition, adding calcium carbonate can also improve the moisture permeability, freshness, and breathability of polyethylene film.

Application of Calcium Carbonate in Thin Films

Many high polymers can be used to make films, which have a wide range of applications, mainly as packaging materials, protective agricultural films, mulching films, etc.

(1) Application of Calcium Carbonate in Polyethylene Film

The film-forming effect of polyethylene is good, and the properties of films made from different varieties vary. Polyethylene films with added calcium carbonate have improved performance in many aspects, such as improving the mechanical properties of the film, the thermal stability of the product, the anti fog droplet performance of the film, and promoting film degradation, which can play a positive role in environmental protection. In addition, the addition of calcium carbonate can improve the moisture permeability, freshness preservation, and breathability of polyethylene film. It is reported that polyethylene film with added calcium carbonate is currently the most widely used and largest amount of plastic packaging film, accounting for more than 40% of the consumption of plastic packaging film.

(2) Application of Calcium Carbonate in Polypropylene Film

Thin films made of polypropylene material have good performance. Except for a small amount of polypropylene films that are blown by blow molding, most films are highly oriented using biaxial stretching technology. Biaxially oriented polypropylene film is widely used in printing, composite, adhesive tape and other fields due to its non toxicity and excellent mechanical strength. In addition, calcium carbonate can also be used in polypropylene microporous membranes prepared by thermally induced phase separation method. Due to the excellent properties of polypropylene itself, microporous membranes prepared using it have both the efficient separation ability of functional membranes and the excellent mechanical properties of plastic films, and can be widely used in industry, medicine, energy, military, and daily life.

(3) Application in Polyvinyl Chloride and Its Related Variety Films

Calcium carbonate can be used for polyvinyl chloride film, and when its dosage is increased within the specified range, it can improve the tensile strength and elongation at break of the film. Calcium carbonate can also be used for polyvinylidene chloride films. The addition of calcium carbonate can not only adjust the barrier properties of the film, but also improve the processing performance and mechanical properties of the film. Calcium carbonate can also be used for polyvinylidene fluoride membranes. Polyvinylidene fluoride membranes prepared by thermally induced phase separation method can achieve the goal of controlling the morphology and structure of porous membranes by changing the content and particle size of calcium carbonate. By processing, the porosity of the membrane can be increased while also improving the water flux and retention rate of the membrane.

Preparation of Calcium Carbonate Thin Film

Due to the poor compatibility between calcium carbonate and polymers, if added directly, the filler is difficult to disperse evenly, resulting in difficulties in processing the filling system, poor product performance, and limited filler dosage. To address these issues, calcium carbonate is typically subjected to surface treatment. Calcium carbonate surface treated with coupling agents such as silane, titanate, or aluminate often combines with the base resin through surface adsorption, physical entanglement, van der Waals forces, and other forms. Compared to unmodified calcium carbonate, modified calcium carbonate is more evenly dispersed in the resin and has better membrane performance.