**2. Preparation**

372 Thermoplastic Elastomers

temperature it behaves like a filler. Zinc stearate is the most largely used ionic plasticizer but some others can be also used, like calcium stearate, zinc acetate, stearamide (Nahmias &

A formulation of ionic thermoplastic elastomer compound consists generally of a neutralized ionomer, ionic plasticizer, non-ionic plasticizer, filler, antioxidants, other polymers, etc. (Zuga & Cincu, 2006a). A significant increase of vitrifying point by incorporating ions into polymers was prouved (Eisenberg, 1977). This increase depends on the nature of the basic ion, the effect being stronger as the ionic forces are larger. They have also shown that the nature of the basic ion influences not only the value of Tg (glass transition temperature), but also the position and shape of the module – temperature curve. The increase of ion content leads to an increase of the module and the increase of the specific

An important contribution to establishing the relation between properties and the ion content in ionomers has been brought by research on carboxylated elastomers. Ionomer-rubbers have remarkable properties such as: high module, large elongation at break and a constant plateau in the module – temperature curve. This constant plateau can be explained through the presence of a small concentration of stable interchain bonds, called multiplets. Elongation at break has been attributed to the loosening of ionic bonds by exchange reactions between crosslinking bridges of various chains, thus hindering an excessive strain. Finally, due to the presence of ionic aggregates which may act as "filling materials", of reinforcement and of

Rheological studies on ionomers in melt (Szymczyk & Roslaniec, 1999) have highlighted a remarkably large increase of melt viscosity, as a result of introducing ions into polymers. This increase depends on the ion concentration or on the neutralization degree and less on the nature of ions. Also, the non-Newtonian character of ionomers in melt is noticed, probably due to the fact that the movement of chain segments and chains implies dissociation of ion pairs in cluster aggregates. This dissociation certainly has a determining influence on rheological properties in melt. In partially neutralized ionomers, hydrogen bonds between the carboxyl

There are a few studies (Zuga & Cincu, 2006b, 2006c; Datta & Kharagpur, 1997; Paeglis & O'Shea, 1988) on ionomers based on maleated and/or sulphonate EPDM rubber indicating the fact that, by introducing neutralization agents (zinc oxide, sodium hydroxide etc.) when a metal base is obtained, modifications of physico-mechanical properties which take place in system are assumed to be due to the rigid phase resulted from the restriction of chain mobility in the ionic aggregate area and a reduction of crystallinity compared to that

This review gives an overview about our research on ionic thermoplastic elastomers based on maleated ethylene propylene diene terpolymer (EPDM-g-MA). The investigations were aimed to obtain some new generations of ionic thermoplastic elastomers with high technical and processing characteristics intended to be processed on the injection moulding machines, resulting in high quality products complying with the international market requirements. Two types of maleated ethylene propylene terpolymer elastomers (EPDM-g-MA) with various levels (0.5 and 1.0 %) of maleic anhydride were used. The EPDM-g-MA rubbers were modified by neutralizing them with zinc oxide and stearic acid, and then the ionomer

quasi-crosslinking, the initial high module of materials can be explained.

functional groups may also have a significant effect on flow properties.

existing in the initial elastomer is noticed (Stelescu, 2010).

Marco Serra, 2002; Zuga et. al, 2009; Stelescu et al., 2011).

plateau of vulcanized rubber.

Ionic thermoplastic elastomers can be obtained by processing of ethylene propylene diene elastomers (EPDM) grafted with maleic anhydride (EPDM-g-MA) having different contents of maleic anhydride. The compositions of thermoplastic elastomers contain besides EPDMg-MA the following elements: neutralizing agents of the ionic groups (zinc oxide in the presence of stearic acid), ionic plasticizers (zinc stearate), nonionic plasticizers (paraffin oil), fillers (precipitated silica, carbon black, chalk), polyolefins (high density polyethylene

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 375

(2 min), introducing zinc stearate, paraffin oil and filler (5 min), homogenizing the blend and removing it from roll in 2 mm thick sheets (4 min). The working parameters were:

No. Ingredient Quantity (phr)

*Raw and auxiliary material testing and acceptance* 

> *Material weigh feeding*

*Preparing the thermoplastic ionic elastomer compound* 

*Compound homogenization on the roller mill* 

*Compound granulation in an electrically heated granulating machine* 

> *Quality control for the resulted pellets*

100 5-20 0.5-2 0-40 0-50 0-90 0-160 2.0

friction 1:1.1 and temperature 150-170oC, for blends without polyolefins.

EPDM-g-MA (Royaltuf 485, Royaltuf 498)

Filler (carbon black, precipitated silica, chalk)

Fig. 2. Laboratory processing stages for ionic thermoplastic elastomers

Nonionic plasticizer (Paraffin oil)

Table 1. Mix formulation of thermoplastic composition

1. 2. 3. 4. 5. 6. 7. 8.

Zinc oxide Stearic acid Ionic plasticizer

Polyolefins (PE, PP) Antioxidants (Irganox 1010)

(HDPE), polyethylene grafted with maleic anhydride (PE-g-MA), polypropylene (PP)), clays, antioxidants (Irganox 1010).

EPDM-g-MA elastomers exhibit the peculiar features of EPDM elastomers, but they can react with divalent metal oxides salts leading to the crosslinking by ionic bonds. The structure of EPDM-g-MA is shown in Fig. 1. The most used EPDM-g-MA elastomers contain 0,5% MA having semicrystalline structure and 1% MA with amorphous structure. The ionic plasticizer solvates the ionic domains at higher temperatures improving flow and at the room temperature it has the role of a filler.

Fig. 1. Chemical structure of EPDM-g-MA elastomers

In the compositions of thermoplastic elastomers, plasticizers assure the decrease of blend stiffness, suitable adherence, improvement of extruding, calendering or elongation, the decrease of freezing temperature of vulcanizates, the enhancing of ozone rezistance and the price reducing. Due to their property to dissolve in rubber, the pasticizers get into the polymer chains diminishing the intermolecular interactions but in the same time new polymer plasticizer interaction appear in system.

The fillers are fine powder materials incorporated in blends in order to improve the composition properties (active fillers) and to reduce price (inactive fillers). The active fillers determine improving of some mechanical properties of elastomer composition namely tensile strength, shearing strength, abrasion resistance, repeated strain resistance.

Carbon black is a filler for many rubber materials having concomitantly the function of reinforcement, filling and coloring material. In rubber blends the particle sizes, structure and pH were affected by the carbon black content. Higher specific surface higher the break and tear resistance of the rubber. The increase specific surface leads to the energy consumption for mixing, rendering difficult the blend processing and the decrease of elasticity of the vulcanized products. The use of carbon black in rubber compositions provides a higher thermal and dimensional stability, increased hardness, enhanced thermal and electrical conductivities, better processing ability.

Polyolefins are utilized in elastomer compositions in order to improve tensile strength, tear strength, chemical reagent resistance.

Thermoplastic compositions were prepared by melt blending technique, on a laboratory electrically heated roller mill equiped with a cooling system. The process flow for the preparation of ionic thermoplastic elastomer compositions is shown in Fig. 2. After the raw materials were tested, the ingredients were weighed according to the processing formulations. The blend constituents were added in the following sequence: roll binding of maleated EPDM (and HDPE) (5-8 min), embedding zinc oxide, stearic acid and antioxidant (2 min), introducing zinc stearate, paraffin oil and filler (5 min), homogenizing the blend and removing it from roll in 2 mm thick sheets (4 min). The working parameters were: friction 1:1.1 and temperature 150-170oC, for blends without polyolefins.


Table 1. Mix formulation of thermoplastic composition

374 Thermoplastic Elastomers

(HDPE), polyethylene grafted with maleic anhydride (PE-g-MA), polypropylene (PP)),

EPDM-g-MA elastomers exhibit the peculiar features of EPDM elastomers, but they can react with divalent metal oxides salts leading to the crosslinking by ionic bonds. The structure of EPDM-g-MA is shown in Fig. 1. The most used EPDM-g-MA elastomers contain 0,5% MA having semicrystalline structure and 1% MA with amorphous structure. The ionic plasticizer solvates the ionic domains at higher temperatures improving flow and at the

m n

In the compositions of thermoplastic elastomers, plasticizers assure the decrease of blend stiffness, suitable adherence, improvement of extruding, calendering or elongation, the decrease of freezing temperature of vulcanizates, the enhancing of ozone rezistance and the price reducing. Due to their property to dissolve in rubber, the pasticizers get into the polymer chains diminishing the intermolecular interactions but in the same time new

The fillers are fine powder materials incorporated in blends in order to improve the composition properties (active fillers) and to reduce price (inactive fillers). The active fillers determine improving of some mechanical properties of elastomer composition namely

Carbon black is a filler for many rubber materials having concomitantly the function of reinforcement, filling and coloring material. In rubber blends the particle sizes, structure and pH were affected by the carbon black content. Higher specific surface higher the break and tear resistance of the rubber. The increase specific surface leads to the energy consumption for mixing, rendering difficult the blend processing and the decrease of elasticity of the vulcanized products. The use of carbon black in rubber compositions provides a higher thermal and dimensional stability, increased hardness, enhanced thermal

Polyolefins are utilized in elastomer compositions in order to improve tensile strength, tear

Thermoplastic compositions were prepared by melt blending technique, on a laboratory electrically heated roller mill equiped with a cooling system. The process flow for the preparation of ionic thermoplastic elastomer compositions is shown in Fig. 2. After the raw materials were tested, the ingredients were weighed according to the processing formulations. The blend constituents were added in the following sequence: roll binding of maleated EPDM (and HDPE) (5-8 min), embedding zinc oxide, stearic acid and antioxidant

tensile strength, shearing strength, abrasion resistance, repeated strain resistance.

clays, antioxidants (Irganox 1010).

room temperature it has the role of a filler.

O

Fig. 1. Chemical structure of EPDM-g-MA elastomers

polymer plasticizer interaction appear in system.

and electrical conductivities, better processing ability.

strength, chemical reagent resistance.

<sup>O</sup> <sup>O</sup>

Fig. 2. Laboratory processing stages for ionic thermoplastic elastomers

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 377

zinc oxide is presented in Fig. 3, the resulting carboxylic salts can act as ionic crosslinkings

Fig. 3. Schematic representation of ionic elastomers obtained by neutralization with zinc oxide

Analyzing physico-mechanical properties of blends based on EPDM-g-MA (Royaltuf 485 and 498 elastomers) with 0.5 % and 1.0% maleic anhydride, respectively, neutralized with

Hardness of ionic thermoplastic composition shows an increase from 71 to 74 oShA when introducing 5 phr of zinc oxide, while for composition with Royaltuf 498, hardness exhibits an increase from 55 to 66 oShA, then further increasing of zinc oxide quantity does not lead to the improving of this property (Fig. 4). Elasticity has very good values especially in the case of Royaltuf 498 elastomer utilization (Fig. 5), but the elasticity practically does not increase to zinc oxide quantity increasing in blend, values of 60% being obtained for Royaltuf 498 composition.

> Royaltuf 485 Royaltuf 498

Royaltuf 485 Royaltuf 498

0 5 10 15 20

ZnO, phr

0 5 10 15 20

ZnO, phr

The tensile strength increase from 10.4 to 18.5 N/mm2 for Royaltuf 485 blends when the maximum value is observed for 5 phr of zinc oxide, after which it exhibit a slight decrease

m n

O O-

Zn2+

O O-

Fig. 4. Dependence of hardness on variation of ZnO level

Elasticity, %

Fig. 5. Elasticity variation depending on ZnO quantity

Hardness, ShA

(Setua & White, 1991).

zinc oxide the following are noticed:

When the thermoplastic compositions are formulated the resulting compound characteristics depend on the quantity of ionic or nonionic plasticizer, neutralizing degree, the ratio elastomer/filler and filler type, the quantity and type of polyolefins.

A basic formulation for ionic thermoplastic elastomers contains the components from Tab. 1. The quantities from Tab. 1 are expressed in parts per hundred parts of rubber (phr).

The resulting blends were granulated on an extruder-granulator equipped with feeder hopper, screw with three beating zones, granulating device and rotary cutter. Feeding was done using materials under the form of strips with 2-3 mm thickness and 20-30 cm length, obtained as a result of blend homogenizing. The thermal regime of extruder-granulator in obtaining EPDM-g-MA rubber granules is presented in Tab. 2. The maleated EPDM-blend granules were then cooled and homogenized. The temperatures during granulation process are given in Tab. 3. Upon the granulation operation we must be sure that the keeping time of EPDM-g-MA rubber blend in extruder-granulator correspond to that required to achieve ionic crosslinking, determined used an rheometer (20 min).



Table 2. Thermal regime for obtaining EPDM-g-MA rubber granules

Table 3. Process variables for granulation of thermoplastic ionic elastomer composition

The pellets needed to determine the physico-mechanical characteristics of resulting ionic thermoplastic elastomer compositions were obtained by injection moulding in a mould with two cavities using an electrically heated injection moulding machine. The test samples were prepared in the following stages: 1) electrical supply, adjusting the process temperature and bringing the machine up to the process temperature; 2) feeding the ionic thermoplastic elastomer pellets in feeder hopper; 3) heating the pellets up to 165-170oC within the injection machine screw; 4) injecting the melt composition in the mould; 5) cooling the plates for 3 min; 6) taking the plates off the mould.

Laboratory tests aim to measurements of tensile strenght, tear strenght, hardness, elasticity, melt flow index, abrasion resistance, flexion resistance, accelerated aging, etc.

#### **3. Influence of the crosslinking degree on EPDM-g-MA ionic elastomer characteristics**

In order to study the effect of neutralizing degree on the physico-mechanical properties of EPDM-g-MA rubber, zinc oxide was used as neutralization agent (Stelescu, 2010). Chemical structure of an EPDM-g-MA elastomer which subjected to the neutralization reaction with

When the thermoplastic compositions are formulated the resulting compound characteristics depend on the quantity of ionic or nonionic plasticizer, neutralizing degree,

A basic formulation for ionic thermoplastic elastomers contains the components from Tab. 1.

The resulting blends were granulated on an extruder-granulator equipped with feeder hopper, screw with three beating zones, granulating device and rotary cutter. Feeding was done using materials under the form of strips with 2-3 mm thickness and 20-30 cm length, obtained as a result of blend homogenizing. The thermal regime of extruder-granulator in obtaining EPDM-g-MA rubber granules is presented in Tab. 2. The maleated EPDM-blend granules were then cooled and homogenized. The temperatures during granulation process are given in Tab. 3. Upon the granulation operation we must be sure that the keeping time of EPDM-g-MA rubber blend in extruder-granulator correspond to that required to achieve

> Area 1 (oC)

145-155 150-180

Table 3. Process variables for granulation of thermoplastic ionic elastomer composition

The pellets needed to determine the physico-mechanical characteristics of resulting ionic thermoplastic elastomer compositions were obtained by injection moulding in a mould with two cavities using an electrically heated injection moulding machine. The test samples were prepared in the following stages: 1) electrical supply, adjusting the process temperature and bringing the machine up to the process temperature; 2) feeding the ionic thermoplastic elastomer pellets in feeder hopper; 3) heating the pellets up to 165-170oC within the injection machine screw; 4) injecting the melt composition in the mould; 5) cooling the plates for 3

Laboratory tests aim to measurements of tensile strenght, tear strenght, hardness, elasticity,

In order to study the effect of neutralizing degree on the physico-mechanical properties of EPDM-g-MA rubber, zinc oxide was used as neutralization agent (Stelescu, 2010). Chemical structure of an EPDM-g-MA elastomer which subjected to the neutralization reaction with

melt flow index, abrasion resistance, flexion resistance, accelerated aging, etc.

**3. Influence of the crosslinking degree on EPDM-g-MA ionic elastomer** 

Area 2 (oC)

160-170 160-190

(oC)

145-155 160-170 145-155 Area 3 (oC)

145-155 150-170 Jet (oC)

150 160

the ratio elastomer/filler and filler type, the quantity and type of polyolefins.

ionic crosslinking, determined used an rheometer (20 min).

Table 2. Thermal regime for obtaining EPDM-g-MA rubber granules

No. Heating zone in granulating machine Temperature range

Types of ionic thermoplastic

Blends without polyolefins Blends with polyolefins

> Pre-heating Blending Cooling

min; 6) taking the plates off the mould.

**characteristics** 

elastomer granules

1. 2. 3.

The quantities from Tab. 1 are expressed in parts per hundred parts of rubber (phr).

zinc oxide is presented in Fig. 3, the resulting carboxylic salts can act as ionic crosslinkings (Setua & White, 1991).

Fig. 3. Schematic representation of ionic elastomers obtained by neutralization with zinc oxide

Analyzing physico-mechanical properties of blends based on EPDM-g-MA (Royaltuf 485 and 498 elastomers) with 0.5 % and 1.0% maleic anhydride, respectively, neutralized with zinc oxide the following are noticed:

Hardness of ionic thermoplastic composition shows an increase from 71 to 74 oShA when introducing 5 phr of zinc oxide, while for composition with Royaltuf 498, hardness exhibits an increase from 55 to 66 oShA, then further increasing of zinc oxide quantity does not lead to the improving of this property (Fig. 4). Elasticity has very good values especially in the case of Royaltuf 498 elastomer utilization (Fig. 5), but the elasticity practically does not increase to zinc oxide quantity increasing in blend, values of 60% being obtained for Royaltuf 498 composition.

Fig. 4. Dependence of hardness on variation of ZnO level

Fig. 5. Elasticity variation depending on ZnO quantity

The tensile strength increase from 10.4 to 18.5 N/mm2 for Royaltuf 485 blends when the maximum value is observed for 5 phr of zinc oxide, after which it exhibit a slight decrease

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 379

 Royaltuf 485 Royaltuf 498

0 5 10 15 20

0 5 10 15 20

ZnO, phr

10 phr ZnO 15 phr ZnO 20 phr ZnO

From the analysis of physico-mechanical properties of blends based on EPDM-g-AM Royaltuf 485 rubber and Royaltuf 498 rubber, respectively, it is noticed that, together with the increase of the neutralization degree, due to the property of groups specific to maleic anhydride existing on the macromolecular chain of reacting with oxides of divalent metals (zinc oxide), ionic bonds form similar to sulphur bridges from vulcanized rubber. This ionic crosslinking has led to an improvement in the value of the module, in tensile and tear strength. It can be inferred that EPDM-g-AM elastomers have reacted chemically with the

ZnO

Minimum moment, Nm 3.8 5 9 7 Maximum moment, Nm 6 17.5 19 20 Optimal vulcanization time 25' 22'45" 17'30" 16'15"

Minimum moment, Nm 4.4 5.6 13.4 11.4 Maximum moment, Nm 9 16.6 16.7 17.5 Optimal vulcanization time 25' 22'30" 16'15" 11'15"

Table 4. Rheological characteristics of EPDM-g-AM blends containing zinc oxide

ZnO, phr

 Royaltuf 485 Royaltuf 498

Tear strength, N/mm

Fig. 9. Tear strength dependence on ZnO level

Characteristics / ZnO level 5 phr

zinc oxide.

*Blends with Royaltuf 485* 

*Blends with Royaltuf 498* 

Elongation at break, %

Fig. 8. Elongation at break variation with ZnO quantity

while the zinc oxide quantity continues to increase (Fig. 6). Module increases together with the increase of neutralization degree in the elastomer compositions (Figs. 6,7). Elongation at break exhibits very high values and a maximum between 5-15 phr of zinc oxide was observed for the two elastomer compositions.

By increasing of neutralization degree this parameter decreases (Fig. 8). Tear strength exhibits a significant and continuous increase for Royaltuf 485 composition when a increase from 38.5 to 53.5 N/mm was observed at the increse of ZnO quantity from 0 to 10 phr. After this ZnO content a slight decrease of tear strength was noticed for Royaltuf 498 composition (Fig. 9).

Fig. 6. Tensile strength and module dependencies on ZnO quantity for Royaltuf 485 blends

Fig. 7. Tensile strength and module variation with ZnO quantity for Royaltuf 498 blends

Comparing characteristics of blends made with Royaltuf 485 rubber with those made with Royaltuf 498 elastomer, both neutralized with zinc oxide, it is noticed that physicomechanical properties are better in blends in which Royaltuf 485 rubber was used. This behaviour is determined by the composition and structure of the two types of rubber; thus, blends containing elastomer with semi-crystalline structure (Royaltuf 485) have exhibited higher values of hardness, module, tensile strength, elongation at break and tear strength than blends containing Royaltuf 498 elastomer which has an amorphous structure

The rheological properties of compositions based on EPDM-g-MA elastomer containing different ZnO levels are presented in Tab. 4. It is noticed that zinc oxide replaces sulfur and vulcanization agents in these blends. The optimal time of vulcanization decreases as the quantity of neutralization agent (ZnO) increases, and the minimum and maximum moments increase as a result of the reinforcing effect due to ionic bond formation.

Fig. 8. Elongation at break variation with ZnO quantity

while the zinc oxide quantity continues to increase (Fig. 6). Module increases together with the increase of neutralization degree in the elastomer compositions (Figs. 6,7). Elongation at break exhibits very high values and a maximum between 5-15 phr of zinc oxide was

By increasing of neutralization degree this parameter decreases (Fig. 8). Tear strength exhibits a significant and continuous increase for Royaltuf 485 composition when a increase from 38.5 to 53.5 N/mm was observed at the increse of ZnO quantity from 0 to 10 phr. After this ZnO content a slight decrease of tear strength was noticed for Royaltuf 498 composition

> 100% Module 300% Module 500% Module Tensile strength

> > 100% Module 300% Module 500% Module Tensile strength

0 5 10 15 20 25

Fig. 6. Tensile strength and module dependencies on ZnO quantity for Royaltuf 485 blends

Zinc oxide quantity, phr

0 5 10 15 20 25

Zinc oxide quantity, phr

Fig. 7. Tensile strength and module variation with ZnO quantity for Royaltuf 498 blends

Comparing characteristics of blends made with Royaltuf 485 rubber with those made with Royaltuf 498 elastomer, both neutralized with zinc oxide, it is noticed that physicomechanical properties are better in blends in which Royaltuf 485 rubber was used. This behaviour is determined by the composition and structure of the two types of rubber; thus, blends containing elastomer with semi-crystalline structure (Royaltuf 485) have exhibited higher values of hardness, module, tensile strength, elongation at break and tear strength than blends containing Royaltuf 498 elastomer which has an amorphous

The rheological properties of compositions based on EPDM-g-MA elastomer containing different ZnO levels are presented in Tab. 4. It is noticed that zinc oxide replaces sulfur and vulcanization agents in these blends. The optimal time of vulcanization decreases as the quantity of neutralization agent (ZnO) increases, and the minimum and maximum moments

increase as a result of the reinforcing effect due to ionic bond formation.

Elasticity module and tensile strength, N/mm2

Elasticity module and tensile strength, N/mm2

observed for the two elastomer compositions.

(Fig. 9).

structure

Fig. 9. Tear strength dependence on ZnO level

From the analysis of physico-mechanical properties of blends based on EPDM-g-AM Royaltuf 485 rubber and Royaltuf 498 rubber, respectively, it is noticed that, together with the increase of the neutralization degree, due to the property of groups specific to maleic anhydride existing on the macromolecular chain of reacting with oxides of divalent metals (zinc oxide), ionic bonds form similar to sulphur bridges from vulcanized rubber. This ionic crosslinking has led to an improvement in the value of the module, in tensile and tear strength. It can be inferred that EPDM-g-AM elastomers have reacted chemically with the zinc oxide.


Table 4. Rheological characteristics of EPDM-g-AM blends containing zinc oxide

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 381

pronounced for compositions with active fillers (carbon black, silica) as compared to compositions containing inactive fillers (chalk). For the compositions containing Royaltuf 485 the increase of filler level determines an increase of hardness of 41 % for compositions having precipitated silica and of 33 % for compositions with carbon black, respectively. The same effect was observed for compositions containing Royaltuf 498, where the hardness increase with 34.8% introducing precipitated silica and with 28.8 % for compositions having carbon black as filler. The introducing of chalk determines a lower increase of hardness

The elasticity decreases by introducing fillers in composition. For compositions containing Royaltuf 485 the elasticity was diminished from 34 to 26 % in the case of carbon black utilization and lower decrease together with the increase of chalk level (from 34 to 30 %). The elasticity shows a nonuniform variation in compositions with silica or chalk and it decreases till 28% in compositions with carbon black (compositions with Royaltuf 498).

Ingredients / Sample O2 U21 U22 U23 C21 C22 C23 F21 F22 F23

Zinc oxide, g 20 20 20 20 20 20 20 20 20 20 Stearic acid, g 2 2 2 2 2 2 2 2 2 2 Zinc stearate, g 20 20 20 20 20 20 20 20 20 20

Chalk, g *- - - - 30 60 90 - - -*  Carbon black HAF, g *- - - - - - - 30 60 90* 

Hardness, ºShA 66 70 83 89 67 70 73 79 80 85 Elasticity, % 32 35 32 30 34 32 32 23 25 23

Elongation at break, % 753 553 487 200 660 527 513 460 433 313

Tear strength, N/mm 36 34.5 44.5 57 33 49 43.5 59.5 70 57 Specific weight, g/cm3 1.02 1.07 1.16 1.21 1.14 1.18 1.21 1.08 1.15 1.22

Table 6. Formulations and characteristics of rubber blends based on EPDM-g-MA (Royaltuf

Tensile strength also decreases together with the increase of silica and chalk levels for the both compositions. In case of compositions containing carbon black the tensile strength

100 100 100 100 100 100 100 100 100 100

*- 30 60 90 - - - - - -* 

10 10 10 10 10 10 10 10 10 10

1 1 1 1 1 1 1 1 1 1

7.7 5.5 6.6 6.5 6.6 6.1 6.5 10.6 9.2 8.2

77 53 41 12 67 44 49 69 60 51

111 162 211 257 147 220 252 150 169 198

(about 15 %, Tab. 5).

EPDM-g-AM Royaltuf

Precipitated silica Perkasil, g

Paraffin oil, Texpar oil

Antioxidant Irganox

Characteristics

Tensile strength,

Residual elongation ,

Abrasion resistance ,

498, g

22, g

1010, g

N/mm2

%

mm3

498)
