The best talcs are significantly more expensive than fillers such as calcium carbonate and must provide additional benefits to justify their use. The main advantages of talc are greater increase in hardness and heat temperature than the same amount of filler such as calcium carbonate. In particular, they are used in polypropylenes for various automotive applications and in household appliances. In some applications, they are used in combination with low-cost fillers such as calcium carbonates. The extra softness is an advantage as it means that machine wear is less than other fillers (although the presence of hard impurities, especially quartz, can compromise it).


The difference in the effect on stiffness between calcium carbonate and two talc with different aspect ratio in polypropylene matrix is shown in the figure.
Analysis of unfilled PP
As can be seen in the figure, the PBA configuration presents the weakest cellular structure of all the experimental configurations. CBA provides an improved cell structure but there are areas without foam inside the part (with the exception of the skin structure). Meanwhile, the hybrid foam particles presented the best cellular structure. It is well known that unfilled PP is a poor choice of polymers for the foaming process, as it limits diffusion in the semi-crystalline structure and also limits the nucleation of the foaming process. does This explains why the PBA moieties in this polymer exhibit a weak cellular structure. Large cells are formed due to the high shear stress applied to the polymer from nucleation, whereby there is cell fusion, causing many smaller cells to form larger cells. CaCO 3 has previously been added to PP in a batch processing foaming method and has been shown to decrease the average cell diameter, increase cell density, and exhibit a more homogeneous cell structure. Considering that the composition of CBA is mainly CaCO 3 , it has been proven to show a good cell structure by the foaming process with FIM.

SEM images of the cross-section of unfilled PP (white bar indicates 100 μm).

SEM images of talc-filled PP sections (white bar indicates 100 μm).
Analysis of talc-filled PP
Compared to the images of unfilled PP, it can be clearly recognized that talc-filled PP shows enhanced properties for the foaming process, except for the hybrid foam of unfilled PP described earlier. CBA still gives PBA an improved cell structure, but PBA is significantly better with the addition of talc. As with unfilled PP, the hybrid foam method produces a superior microcellular structure for talc-filled PP, with increased foam producing a smaller and finer cell structure.
Talc is used as a nucleating agent in polypropylene, which usually depends on the crystalline structure and talc particles, which have a crystalline and layered structure, as well as van der Waals bonds, which provide a unique surface for the nucleation of polymers. As a result, talc can increase the number of nuclei in the polypropylene melt.
Thermal deviation temperature
Thermal stability is another key feature of semi-crystalline thermoplastics that benefit from the use of layered fillers such as talc.
Talc is used to increase the crystallization temperature of PP. The layered structure of talc makes the sample solidify faster, thus reducing the injection molding cycle time.
Talc type and level | HDT (centigrade) |
---|---|
None | 97 |
20% w/w low aspect ratio talc | 109 |
20% w/w high aspect ratio talc | 121 |
Talc is used in PP to increase the efficiency of the thermoforming process, which is used due to its nucleation property and other polymer processes.
At low concentrations (less than 3% by weight), talc acts as a nucleating agent and reduces the size of the spherulite and shortens the processing time.
Creep and stiffness
Table A comparison of the effect of talc on the creep of a polypropylene composite
Creep (expressed as % change in strain after Filler type and level 2 years
Talc type and level | HDT (centigrade) |
---|---|
None | 97 |
20% w/w low aspect ratio talc | 109 |
20% w/w high aspect ratio talc | 121 |
Permeability
The layered nature means that talc can significantly reduce the permeability of polymers, especially if the particles are aligned for maximum effect.
This is illustrated by the data in the table comparing the oxygen and water vapor transmission rates of talc-containing polypropylene with calcium carbonate-containing film.
Table A comparison of the effect of a lamellar talc on the permeability of homopolymer polypropylene film
Oxygen transmission rate | Water vapor transmission rate | |
---|---|---|
Filler type and level % w/w | cm3/m2 in 24 h | g/m2 in 24 h |
None | 430 | 0.50 |
30% calcium carbonate | 325 | 0.41 |
30% talc | 190 | 0.31 |
Impact resistance
Impact resistance is always an important property for PPs, but it is a complex property to describe. The impact strength in these semi-crystalline polymers can be influenced by many properties of talc, especially particle size, dispersion and layering, and these are often not sufficiently explained in the literature on talc compounds, rather than various factors. Be clearly quantified.
Talcs appear to generally reduce the impact strength of homopolymer and homopolymer polypropylene at levels above 10 wt%. (What is clear is that the smaller talcs have the best impact resistance, as shown in the figure.)

The effect of talc particle size (d50) on the impact resistance of polypropylene copolymer (20% by weight of talc)
There is evidence that very fine talcs actually increase impact strength below 10% by weight, an effect believed to result from polymer nucleation. This is shown in the figure.
Fig. The effect of fine talc addition level on the impact resistance of high impact grade polypropylene.
Tensile strength
The results show the tensile strength against the predicted result through simple modeling method for unfilled PP and PP filled with talc. The error range for unfilled PP is between 22.2% and 9.5%, while talc-filled PP has a greater inaccuracy between 26.0% and 12.4%. The main reason for this is that the equations have not been modified to accommodate talc to the polymer, the previously derived equations were for the addition of talc to the polymer and not for the polymer with talc already incorporated.

Comparison of bending strength
The flexural strength results are experimental and predicted for unfilled PP and talc filled PP. The largest error is 16.5% while the smallest error is 3.1% (shown as a dashed line, so that the predicted data for talc PP is an overprediction). Therefore, showing that simple flexural strength modeling provides improved results compared to the tensile strength of polymers in this experiment. As with the tensile results, the least accurate comparisons are obtained from the chemical foaming agent, while the most accurate comparisons are related to the hybrid foaming method.

modulus of elasticity (E)
The graph of the average value of E for unfilled PP shows that the parts produced with chemical foam have the highest ability to resist length changes under tension, 949.7 MPa, then the combination of the two foaming methods is 825.4 MPa. The physical floor is the lowest with 817.5 MPa. For parts made with chemical materials and hybrid foams, parts with greater mass have the ability to increase resistance to elongation, both with reduced E as part weight decreases. Interestingly, there is an increased deviation in E for the physical foam test pieces with the lowest mass, which can be explained by the poor foaming ability of unfilled PP. The physical foaming results show a different stress-strain behavior compared to the chemical and composite samples as E increases as the mass of the parts.

Young’s modulus (E) versus weight loss (a) Unfilled PP (b) PP filled with talc.
It seems that PP filled with talc shows a more consistent behavior than unfilled PP. Chemical and physical foam follow a similar pattern for E values, with weight loss: 1442.9 MPa, 1367.2 MPa, and 1139.3 MPa for chemical foam, while 1450.3 MPa, 1379.6 MPa, and 1155.1 MPa for physical foam. For the hybrid foam method, the E values are lower with weight loss at 1312.0 MPa, 1230.5 MPa and 1087.3 MPa. Like unfilled PP, parts produced using the hybrid foam method have much more deflection than the other two methods, resulting in a more unpredictable part. The ratio of E and mass is also the highest for the hybrid foam, together with the high deviation in these results, it indicates a significant foaming and foaming behavior of the material in terms of the ability of the parts to resist length changes during stress. Physical foaming process control and talc PP results are more predictable with the inclusion of talc filler compared to unfilled PP results. This can be justified by the fact that talc is a known nucleating agent for polyolefin materials, which is shown here to produce foamed parts that are more compatible with higher E values.
ultimate tensile strength (S u )
Like the modulus of elasticity, S u of the parts was checked along with the weight of the produced parts. In addition, the predicted results were also added.

Ultimate tensile stress (Su) against weight loss (a) Unfilled PP (b) PP filled with talc.
The average S u value of the diagram for unfilled PP (a) shows that the parts produced with chemical foam have the highest ability to withstand the loads that extend the test section (19.2 MPa), followed by the combination of these two foams. . Methods (17.1 MPa). It is shown that the physical foam is generally less Su and is constant regardless of the mass of the test pieces. As in the previous section, the poor results from physical foaming of unfilled PP are well known. All three foam processes show tensile strengths that are significantly higher than the simulated results. For parts made with chemical materials and a combination of chemical and physical foam, parts with greater mass have the ability to increase resistance to tensile loads. Similar to the E results, the hybrid foam methods have a much wider distribution of results. The deviation for the hybrid foaming methods due to the nucleation rate is very high, by combining the two foaming methods, the nucleation energy increases significantly and thus causes large changes in the morphology of the final part.
For the test pieces produced with PP filled with talc (b), the general behavior is the same as the results of E: in that S u decreases with decreasing mass. The lower Su values compared to unfilled PP can be explained that the plasticity is impaired by the addition of talc due to the stress concentration and poor shear sliding ability of the polymer matrix. S u is the product of the force per unit area, and the inhomogeneous cross-sectional area and bubble content that reduces the mass clearly change the unit area of the test piece. The chemical and physical foaming methods have higher Su than the hybrid foaming method, and all three of the simulation results are higher. The inclusion of a talc filler along with physical foaming has a significant effect on Su. There is a decrease in S u with a decrease in mass. It is explained by the reduction of the polymer in the cross-sectional area of the sample. However, for all compositions, S u is lower with talc compared to unfilled PP. For both materials, simple modeling results underestimate S u. A possible reason for this is that the equations use the general skin thickness, which is not the case as seen in the microscopic properties section of this research.
Flexural modulus data
Tensile mechanical properties are important for the design of polymer parts. In addition to E and S u, the maximum load bearing capacity of a material without permanent deformation is considered as a mechanical criterion. The results of maximum bending strength (σfM) for two PP materials are shown

Maximum flexural strength (σfM) against weight loss (a) Unfilled PP (b) PP filled with talc.
The graph of the average value of σ fM for unfilled PP (a) shows that the parts produced with chemical foam have the highest ability to resist fracture during bending (30.8 MPa). Then it is followed by the combination of two methods of foaming (29.8 MPa). For parts made with chemical materials and a combination of chemical and physical foam, parts with higher mass can withstand the highest stress. The values are 30.5 MPa and 28.9 MPa, respectively, thus identifying the chemical foam as not only the highest σfM, but also more consistent across a wide range of part masses. There is a wide range of deviation in σfM for the hybrid foam test pieces and this is consistent with the tensile tests in the previous section. The physical flooring results show a different σfM behavior compared to other flooring methods, and this result is also similar to the tensile results.
The results for the test pieces produced with PP filled with talc (b) show a different behavior from that of unfilled PP. All foamed compositions have lower σfM than unfilled PP. They also have a similar σ fM (27.5–27.3 MPa) at high mass, and this σ fM decreases with decreasing mass due to more foaming in the parts. Again, chemical foam is more consistent in terms of mass and mechanical properties. In terms of the ability of the parts to withstand the highest stress at the moment of yielding, the control of the composite foam process with talc-filled PP shows that there is a wide σfM distribution, especially in parts with low mass. All the mechanical test data presented in this research, except for unfilled PP foaming, follow a clear trend, as the weight decreases and the foams increase, the mechanical properties decrease. Experimental data show that with the strongest mechanical properties, the chemically foamed parts do not have the highest cell density, but have the thickest skin thickness in the case of both tested PPs. The current research trend is to obtain foamed polymer samples with the highest cell density, but in this research it can be seen that the cell density has little effect on the mechanical strength compared to the thickness of the skin. which has a major weight on tensile and bending properties. Shish kebabs show very high strength and modulus, but they are able to form on the skin layer only because of poor cutting and fast freezing. However, when the skin begins to decrease in size, this can lead to a decrease in mechanical strength.
The results of the simple model under-predicted the actual results, apart from the highest weight savings for talc-filled PP using the hybrid foam method.
Recycling issues
The main use of the polymer for talc fillers is in thermoplastic compounds for the automotive industry, and these compounds are believed to have high recycling rates. Many major automotive markets have strict environmental goals that encourage recycling. Therefore, in the European Union, the End-of-Life Directive requires that at least 95% of a vehicle’s weight must be reused or recycled. Talc-filled thermoplastics are recycled and reused for a variety of automotive applications, primarily underhoods, body arch liners, and cable harness components. There is also recycling into non-automotive parts such as water and sewer pipes, furniture bases, etc. According to the Industrial Minerals Association (ima-europe.eu), about 95% of the talc used in automotive manufacturing in Europe is recycled in some cases.
Harmful effects
Detrimental effects on performance can be problematic for some talcs, particularly polypropylene, which is particularly prone to such problems. These effects vary significantly from talc to talc and are mainly due to structural impurities such as aluminum and iron, which can degrade the polymer. It should be noted that the reactivity of these impurities can vary significantly depending on their chemical environment, and therefore metal surface alone is not a sufficient guide to performance. In some cases, it becomes problematic. This is shown in the figure.
In this SHA+ sample test, it shows the amount of elements in the sample by weight
The effect of talc surface modification on the thermal stability of polypropylene homopolymer (150 degrees Celsius)
In general, the quality of the layered structure of talc can be determined by methods such as the ratio between the width and height of the particle using the distribution of particle size and the determination of the percentage of hydrophobic and hydrophilic sites on the surface, as well as the investigation of crystalline characteristics, short-range order and particle structure.
Talc is also used for filling in polypropylene, which causes soft texture, less wear, high gloss, good transparency and less oil absorption.