I. Introduction

The optimization and streamlining of certain structures, parts manufacturing combined with high technical qualities (mechanical strength and physicochemical), recycling and reclamation of industrial waste, reducing maintenance costs … have motivated the use and development of specific materials whose composition and characteristics accommodate themselves to technological constraints.

The composite materials based on expanded perlite and unsaturated polyester resin (organic resins regenerated), were developed for this purpose. The basic idea is to combine in the same mass of different materials by their chemical and structural natures in

order to increase performance mechanical, physical and / or chemical that can facilitate implementation [1].

II. Materials and methods

1. The expanded perlite

a- petrographic aspect

Perlite is a volcanic rock of spheroidal texture (Fig.1), formed of aluminum silicates mainly of sodium feldspars and / or potassium and quartz with 2 to 5 % of water constitution. After grinding and heating (900-1200 ° C), perlite expands, significantly increasing the volume but keeping the same mass (Fig. 2).

The resulting product is a white powder lumpy formed of vitreous kernels. The expanded Character recognized of perlite, unlike other siliceous volcanic rocks gives its main exploitable properties in the construction industry, horticulture, environment and other industries including ceramics.

Figure 1.
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Polarized light microphotograph unparsed of vitrous perlite.

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Glass, containing a phenocryst of feldspars, is cut into small beads (= perlites) by small cracks.

Figure 2.
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The perlite as a total rock under different forms, grinded and expanded

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b- Chemical composition and physic-chemical characteristics

In Tables I and II below, are respectively the chemical composition of perlite from various occurrences and some physical, chemical and mechanical characteristics.

Table I Chemical composition of major elements of perlite from various fields
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Table 2
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Table II Technical Specifications of expanded perlite [4]
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2. Polyester resin

The table below lists some technical specificities of resin polyester used in the mixture.

Table 4
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a- Preparation

- Polycondensation

1 st stage: monoester

figure 3

2 nd stage: poly esterification

The monoester can react with a molecule of glycol acid, or on itself.

figure 4

The equilibrium displacement polyesterification occurs by three different methods:

  • by vacuum action,

  • training by neutral gas,

  • training by solvent

- Copolymerization

The Curing of unsaturated polyester resin is obtained by copolymerization of polycondensate with the monomer. The reaction is conducted in the presence of organic peroxide:

  • At ambient temperature, in combination with accelerators

  • Or hot.

III-Elaboration and synthesis

Three operations are essential to the implementation of a composite material:

  1. 1.

    Impregnation of reinforcement by the resin.

  2. 2.

    Shaping the geometry of the part.

  3. 3.

    Curing of system.

There are various techniques for the preparation of the composite material [5, 6]. One used in this case is compression molding. This is a artisanal method which involves manually put in shape, parts based of marble powder more a reinforcement or filler in form of a paste; all mixed with a thermosetting matrix generally of unsaturated polyester resin.

1. Description of the process

a- Preparation of the mold surface

The mold is spread with wax (de-molding agent) uniformly to the buffer. This waxing operation serves to protect the surface of the molded part, for that, it’s recommended to operate naturally in a dust free environment. [7]

b- The paste preparation

In a cylindrical enclosure equipped by a mixer, we prepare the paste to mold, consists of a mixture of polyester resin and a filler of perlite, associated with the marble powder and other ingredients as catalyst (methyl peroxide ethyl cetone) and accelerator (cobalt octoate) to the socket (Fig. 3).

Figure 3
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The various ingredients entering into the formulation of the paste

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c- Compression and formatting

The prepared viscous paste is cast onto walls of the open mold according to the chosen form and dimensions [8,9].

The mold closed and maintained under pressure until fully curing, which usually requires several minutes (Fig. 4). Then the parts are de-molded delicately from the periphery of the mold.

Figure 4.
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A device for shaping of the composite material which the mold appears under pressure

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2. Formulations

The tables below detail the various formulations undertaken in the manufacture of parts distributed in groups of samples (Tab.III)

Tab. III:
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Formulations of different tested parts for the preparation of the composite material

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figure 8
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tile of dimension 100 mm × 100 mm according to the thickness, the rate of expanded perlite and the nature of the used reinforcement.

a- According to the thickness

For the group 1 of samples (Table IV), more the piece is thicker, the load of rupture and the applied stress are large (Fig. 5). The variation does not follow a linear curve.

Table IV: bending test measurement according to the thickness of the composite parts
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Fig. 5
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Stresses applied to composite tile according to the thickness

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b- According to the rate of expanded perlite

• Marble powder - expanded perlite mixture:

Table V: Bending test according to the rate of expanded perlite
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Figure 6
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Stresses applied to composite tile according to the rate of expanded perlite

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The lowest stress recorded by the materials composed of the highest rate of expanded perlite.

• Sand - perlite mixture

Table VI: The bending test measurement according to the rate of expanded perlite
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Figure 7:
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Stresses applied to composite tile according to the rate of expanded perlite

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With perlite, the material possesses the smallest elongation and the smallest stress resistance. In addition, the introduction of marble powder increases substantially this property in comparison with a filler of sand.

• The nature of reinforcement

Tab. VI: the bending test measurement according to a reinforcement based of worn plastic filaments.
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The load of rupture is significantly improved by reinforcement the mixture of plastic fabric worn 2D (group 4, Fig. 8) while the stress does not vary much (Table VI).

Figure. 8
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Variation in tensile strength according to the nature of the reinforcement.

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2. The water absorption [11]:

The technique involves the impregnation of the dry sample in an enclosure filled water and its submission to the hydrostatic weighing.

Table VII The absorption rate measurement in the different samples of the composite material based expanded perlite.
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Table VII shows the increasing of water absorption with the quantity of expanded perlite introduced into the material. This variation is linked, all the more, to the coarse particle size of the expanded perlite which contains interstices or pores favor draining of water molecules despite the hydrophobic nature of the polyester resin involved in the mixture.

1. The density [11]:

Table VIII Density measurement in different samples of the composite material based on expanded perlite.
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Given the very low density of the expanded perlite (0.08 to 0.12), the density of the composite is even lower than the perlite content is high. Table VIII shows in addition, that the reinforcement plastic (group 4) may also contribute to the lightening of material.

3. Abrasion test [12]:

The abrasion resistance of the materials prepared was quantified by measuring the length of the imprint produced on a face by a rotating disc, in the presence of an abrasive.

Table IX: Abrasion Measurement for different types of composite materials based on expanded perlite.
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Materials containing marble powder and sand to a less degree have a higher resistance to abrasion than the materials containing only expanded perlite (Table IX).

5. Chemical resistance: [13]

The prepared tiles from different formulations are subjected to the corrosive solutions action (NH4Cl, NaOCl, HCl, KOH) to assess their chemical resistance degree. The attack period is defined according to the use of the material; floor or wall, but generally limited to 30'-1h.

Table 12
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The composite material remains generally refractory to chemical attack which only affects the cut sides that have available interstices for corrosive solutions.

V. Conclusion

The composite materials developed in this study, from an organic resin associated with the expanded perlite and other mineral charges such as marble powder and / or sand.

Different formulations are produced; considering both the proportion of expanded perlite, the nature of the mineral used as reinforcement and the thickness of the plates. The different tests performed to exhibit mechanical and mechanic- chemical properties allow obtaining the following conclusions:

  • Parts that offer the most strength is thicker with have reinforcement in plastic (wastes) and low rate of expanded perlite.

  • Increasing the rate of expanded perlite reduced the density of the composite materials and gives them lightness.

The fields of application of the composite material developed herein are highly related to characteristics mentioned above. Its chemical mechanical strength gives it a certain rigidity, which allows its use as soil protection blankets. On the other hand, the lightness of the product is indicated for use in wallboard for thermal or acoustic insulation.