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(THE INFLUENCE OFCALCIUM CARBONATE MORPHOLOGY

IN REINFORCEMENT OF THERMOPLASTICS)

(تاثیر مورفولوژی کربنات کلسیم در تقویت ترموپالستیک ها)

(Javad M.Sefidabi, Mohammad S. Yalfani, Maryam Golbaghi)

Presenter: (Maryam Golbaghi)

Paper Code: (imbpa15-00260027)

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Introduction

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Bentonite

Kaolin

Talc

Silica

Mica

CaCO3

Types of Films

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Calcium CarbonateKaolin clay

Silica

Talc Wollastonite Mica

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Talc products are processed using various combinations of

dry grinding, air separation and flotation depending upon the

quality of the crude ore and the properties required for

intended applications.

The talc most often used as filler is commonly called platy

talc. It is distinctly lamellar characteristically soft talc.

Purity is typically >90% and filler grades are 325 mesh and

finer.

Mg3Si4O10(OH)2

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Al2Si2O5(OH)4

Airfloat: Dry-ground, air separated

Water-washed: (disordered metakaolin) Al2Si2O5(OH)4 → Al2Si2O7 + 2 H2O

Delaminated: aluminium-silicon spinel which is sometimes also referred to as a gamma-alumina type

structure: 2 Al2Si2O7 → Si3Al4O12 + SiO2

Calcined: platelet mullite and highly crystalline cristobalite: 3 Si3Al4O12 → 2(3 Al2O3·2 SiO2) + 5 SiO2

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Bentonite is a native colloidal hydrated aluminum silicate or clay found in the midwest

United States, Wyoming, and Canada. Consisting mainly of montmorillonite, a smectite

clay, it is a very fine, odorless, pale buff or cream colored to grayish powder. It consists

of particles in the range of 50 to 150 microns, but also has numerous particles in the 1 to

2 micron range.

The applications of Bentonite:

• Pharmaceutical applications

• As a suspending agent or a viscosity building agent

• As an adsorbent

• As gelling agent

• As emulsion stabilizer

• As clarifying agent

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CaCO3 :

Ground calcium carbonate (GCC)

Precipitated calcium carbonate (PCC)

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Ground calcium carbonate (GCC)

Ground natural carbonates (GCC) are further

characterized as dry-ground products, usually in grades

from 200 mesh to 325 mesh, and wet-ground products.

Of the wet-ground products, fine ground (FG) calcium

carbonates: 3 to 12 micrometers

Ultrafine ground (UFG): 0.7 to 2

Rhombohedral

Prismatic

Aragonitic

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Precipitated calcium carbonate (PCC)

Precipitated calcium carbonate (PCC) is produced for applications requiring any

combination of higher brightnesss, smaller particle size, greater surface area, lower

abrasivity, and higher purity than is generally available from ground natural products.

Fine PCC: 0.7 micrometer

Ultrafine PCC: 0.07 micrometer

Scalenohedral

Spherical

Clustered aragonitic

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Calcite, the most stable form of PCC, has rhombohedra or octahedral structure.

Aragonite and vaterite have an orthorhombic structure that because of its meta-

stability will remain orthorhombic only at temperatures below 400 °C.

High purity limestone (95 % CaCO3) is calcined at 1000 °C in a kiln to produce

carbon dioxide gas and calcium oxide (CaO - lime). The next step is to react the

CaO with water to yield a slurry of Calcium hydroxide (Ca(OH)2 - slake):

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Comparison of calcium carbonates

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Factors affecting on the particle sizes

The carbonation stage (during PCC production)

The pH of aqueous medium

Temperature

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Precipitated calcite particles at different reaction times: (a, d and g)

non-stirred; (b, e and h) mechanically stirred, and (c, f and i)

ultrasounds agitated.

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Research by Agnihotri et al. has shown that particle size is

affected by the CO2 gas flow rate during carbonation.

The particles size is found to decrease with increasing flow

rate.

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The size of the primary particles too decreased with increasing temperature and pH and is the result of the increase in nucleation rate of the primary particles.

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The application of thermoplastics in automotive, aerospace and electronic field has been increasingly

expanded, where the resistance of the products has special importance. High resistant of polymeric

products against impact and scratch is one of the important factors for users.

One of the modifying methods of surface

strength of the polymers is the filler

coating. The reinforcement of polymers is

carried out using surface-coated fillers.

Precipitated Calcium Carbonate (PCC) has

been used as most effective filler to

improve the physical and mechanical

properties of polymers.

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the role of agglomerated particle on stress concentrator can be divided into two parts.

The first is decreasing of stress concentrator points and the second is increasing the

value of stress concentration, i.e., the debonding around a big particle can happen at

lower stress rather than the smaller particles. According to Fig. Calcium Carbonate

with average size of ~ 2.0 µm has a better filler article dispersion and then to form

smaller agglomerates than CaCO3 with 3.0 µm size.

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the role of agglomerated particle on stress concentrator can be divided

into two parts. The first is decreasing of stress concentrator points and the

second is increasing the value of stress concentration, i.e., the debonding

around a big particle can happen at lower stress rather than the smaller

particles. According to Fig. Calcium Carbonate with average size of ~ 2.0

µm has a better filler article dispersion and then to form smaller

agglomerates than CaCO3 with 3.0 µm size.

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It is difficult to distribute Calcium Carbonate

homogeneously in plastic materials since it

has a hydrophilic character. Therefore,

Calcium Carbonate becomes hydrophobic by

coating with compatible and apparent

compound. Calcium Carbonate after surface

coating becomes hydrophobic and compatible

with polymer matrix, and thus mechanical

properties of final product would be

enhanced.

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Differential thermal analytical (DTA) plots and Infrared (IR) spectra were

employed to confirm the stearic acid coating on the Calcium Carbonate surface.

The peaks at 2925 and 2885 cm‒1, are ascribed to the methylene groups of alkyl

chain and the shoulder at 1615 cm‒1 corresponds to the appearance of a

carboxylic group, indicating that stearic acid has been attached to the surface of

CaCO3 .

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Differential thermal analysis (DTA) was employed to explain the mechanism of the physical or chemical

adsorption of stearic acid binding to the surface. Based on Fig. 5, the peaks on DTA curves of samples at

217 °C and 248 °C are attributed to the molecules of stearic acid physically adsorbed in layer of calcite.

The peaks on DTA curves of samples at 342-460 °C are attributed to the molecules of stearic acid

chemically adsorbed in layer of calcite.

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Surface coating of PCC with stearic acid effectively reduces the surface

tension from about 210 to 40-60 mg/m2, which results in a better

dispersion of rigid particles and decreases the adhesion between fillers and

a polymer matrix. From the dissolution curves, where the amount of the

bonded coupling agent is plotted against the quantity used for the

treatment, two characteristic quantities can be determined.

The efficacy of the surface treatment

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If the amount of the coupling agent is increased further, some of it still

can be bonded to the surface, but the dissolved portion increases

drastically. Finally a concentration is reached above which no more coupling

agent can be adsorbed on the surface. The maximum amount of coupling

agent which can bonded to the surface can be determined from the

horizontal part of the dissolution curve and is designated as Cmax--this is

1.95 wt% in case (a).

The efficacy of the surface treatment

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The efficacy of the surface treatment

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The improvement of the coating amount:

In order to improve the toughness of the final polymeric nanocomposites, the

determination of the optimum coating amount of surfactant for PCC fillers is another

critical factor. This depends on the type of surface modification, the chemical reaction, and

the arrangement of the surfactant molecules on the surface.

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IS (J/m)E (MPa)EB (%)σB (MPa)Stearic acid (%)

11.9 ± 0.81673 ± 8014.2 ± 2.628.8 ± 0.6Untreated

12.7 ± 0.91679 ± 5419.1 ± 2.827.3 ± 0.60.3

13.7 ± 0.41717 ± 3718.4 ± 1.528.5 ± 0.40.5

13.1 ± 0.81897 ± 5822.7 ± 2.625.7 ± 0.30.7

13.02 ± 0.91658 ± 7620.9 ± 3.125.8 ± 0.81.0

Mechanical properties of HDPE blend with CaCO3

(3.0 µm) treated with stearic acid

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Mechanical properties of HDPE blend

with CaCO3 (2.0 µm) treated with stearic acid

IS (J/m)E (MPa)EB (%)σB (MPa)Stearic acid (%)

15.7 ± 0.71824 ± 9917.8 ± 2.525.9 ± 1.1Untreated

15.2 ± 0.51872 ± 5817.4 ± 2.127.4 ± 0.40.3

15.6 ± 0.51903 ± 3815.4 ± 1.325.9 ± 0.70.5

16.6 ± 0.82111 ± 10515.4± 2.224.6 ± 1.40.7

16.0 ± 1.01751 ± 7019.6 ± 2.921.5 ± 1.91.0

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The shape of PCC particles can have two

strong effects on the quality of final filler-

polymer compound.

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The shape of particles can ease their dispersion. For example,

needle-like or rod particle may be dispersed better than spherical

ones. Usually spherical particles have higher tendency to

agglomerate than the needle-like or rod ones. Therefore, they resist

against dispersion. In addition, when PCC particles shape with high

dispersion capacity is used for filler-polymer compound production,

lower mechanical energy is consumed through extrusion

Depending on the polymer structure, PCC particles can incorporate

into the matrix when their shape can leave least possible void space

between particles and polymer molecules.

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As it is shown in Fig. (A), PCC in rod form can have high interfacial contact

with linear polyethylene molecules. Spherical particles may create big

distance between groups of polymer molecules leading to empty spaces.

Such void spaces deteriorate the mechanical properties of composite, in

particular impact strength.

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PCC is produced using chemical procedure in which the shape and the size of particles are controlled by the operational parameters. The shape of PCC particles can influence the filler-polymer composite formation. They can ease the dispersion of particles into the matrix of polymer by least resistance against segregation from each other. In addition, particles with appropriate shape have higher resemblance with polymer molecules resulting to minimum void spaces within the matrix of polymer.

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