Home

Method for Determining Properties and Structure of Blend Rubber Materials

● Step 3 : The material sample is pressed on a hydraulic press with heating according to the following mode: vulcanization temperature is 170 o C, pressure is 6 kg/cm 2 for 15 minutes.

● Step 4 : Take the mold out and let it cool slowly, then take the sample out.

2.2.1.3. Manufacturing CR/PVC blend rubber samples

a) Single component of material fabrication

Table 2.3. Single component of CR/PVC material


Raw materials, chemicals

Content (ppm)

PVC-S CR DOP

Cd-stearate Ba-stearate Stearic acid S

ZnO

Promoter M Promoter DM Carbon Black N 330 SiO 2

0 100

100 0

60 (% by PVC) 1.5 (% by PVC) 1.5 (% by PVC) 1

3

5

0.3

0.6

30

12

Maybe you are interested!

b) Material manufacturing process

● Step 1: Mix PVC separately with cadmium stearate stabilizer, barium stearate and DOP plasticizer, then heat-cured at 70 o C for 6 hours.

● Step 2: Take PVC mixed with plasticizer and mix it with CR rubber and additives in a closed mixer at 170 o C, for 7 minutes and speed of 50 rpm.

● Step 3: After mixing, the rubber - plastic mixture is cooled and mixed with accelerator and sulfur at room temperature on a 2-roll rolling mill for 5 minutes at a temperature less than 50 o C.

● Step 4: The material sample is pressed on a hydraulic press according to the following mode: temperature

vulcanization 170 o C, pressing pressure 6kg/cm 2 , time 15 minutes.

● Step 5: Take out the mold and let it cool slowly before taking the sample.

2.2.1.4. Manufacturing of NBR/CR/PVC blend rubber samples

a) Single component of material fabrication

Table 2.4. Single component for manufacturing NBR/CR/PVC material


Raw materials, chemicals

Content (ppm)

NBR CR PVC DOP

Cd-stearate Ba-stearate Stearic acid S

ZnO

Promotion D Promotion DM

Carbon black N 330

SiO 2

x 1 x 2 x 3

60 (% by PVC) 1.5 (% by PVC) 1.5 (% by PVC) 1

3

5

0.3

0.6

30

12

Condition

x 1 + x 2 + x 3 = 100

b) Material manufacturing process

● Step 1: Mix PVC separately with stabilizers cadmium stearate, barium stearate and plasticizer DOP, then incubate at 70 o C for 6 hours.

● Step 2 : Take PVC mixed with plasticizer and mix with two rubbers (CR, NBR) and additives on a closed mixer at 170 o C, time 7 minutes and speed 50 rpm.

● Step 3: The rubber-plastic component and additives are mixed with accelerator and sulfur on a 2-roll mill for 5 minutes at a temperature below 50 o C.

● Step 4 : The material sample is pressed on a hydraulic press with heating according to the mode: heat

vulcanization temperature 170 o C, with pressure 6 kg/cm 2 for 15 minutes.

● Step 5: Take the mold out and let it cool slowly, then take the sample out.

2.2.2. Method for determining properties and structure of blended rubber materials

2.2.2.1. Method for measuring tensile strength of materials

Tensile strength is the tensile stress recorded at the moment the sample breaks. The tensile strength of blended rubber material samples is determined according to TCVN 4509: 2006 [110] or ISO 37 - 2006 standards. The sample for measuring tensile strength is made in the form of a dumbbell as described in the figure below:

The device used to measure tensile strength is the YG - 632 tensile tester (Taiwan).

The tensile strength TS b (MPa) of the sample is calculated according to the following formula:

T S b

F b

W

t

In there :

F b is the tensile force of the sample (N)

W t is the cross-sectional area of ​​the test specimen (mm 2 ) The results are averaged from 5 measured specimens.

2.2.2.2. Method for determining elongation at break of materials

Elongation at break is the elongation when pulled over the test length at the breaking point. The standards for the sample and measurement are the same as the method for determining tensile strength (according to TCVN 4509: 2006) [110] on the YG - 632 tensile tester (Taiwan).

Elongation at break (E b ) is calculated by the following formula:

E

l 1l 0x 100%

b l

0


In there:

l 0 is the length between two marked points on the sample before tensile test (mm) l 1 is the length between two marked points on the sample immediately after fracture (mm) The results are averaged from 5 measured samples.

2.2.2.3. Method for determining permanent elongation of materials

The residual elongation is the difference in length of the sample after being pulled to break and left to rest for 3 minutes before being pulled to break, calculated as a percentage compared to the original length. The standard of the measuring sample and measuring equipment are the same as the method for determining the tensile strength (according to TCVN 4509: 2006) [110].

The residual elongation ( E ) is calculated by the formula:


E remainder =

l 2l 0x 100%

l

0


In there:

l 0 is the length between two marked points before pulling (mm);

l 2 is the length between two marked points after 3 minutes of tensile stress (mm). The result is the average of 5 measured samples.

2.2.2.4. Method for determining material hardness

The hardness (Shore A hardness) of blended rubber materials is determined according to TCVN 1595-1: 2007 [111] or ISO 7619-1: 2004. The principle of measurement is to measure the depth of the indenter when pressing into the material under specified conditions. The measurement is performed on a TECLOCK (Jis K6301A) hardness gauge (Shore A) of Japan. The rectangular test piece must allow measurement at 5 points. The hardness index is read on the scale after 3 seconds from the time of impact on the sample. For samples that after 3 seconds, the indenter continues to press deep into the sample, the hardness index is determined after 15 seconds. Each sample is measured at

3 different positions. The result is the average of 5 measurements.

2.2.2.5. Method for determining the abrasion resistance of materials

Acron abrasion resistance measurement of materials is performed according to Vietnamese standard TCVN 1594 - 87 [112]. Akron abrasion resistance test is performed on Y - 634 abrasion resistance tester (Taiwan).

The amount of abrasion (V) of the sample, in cm 3 /1.61 km, is calculated by the formula:


In there:

Vm 1 m 2

d

m1 is the mass of the sample before abrasion (g);

m2 is the mass of the sample after abrasion (g);

d is the density of the rubber being tested g/cm 3 (density of blended rubber is determined according to standard TCVN 4866: 2007 [113].

2.2.2.6. Method for determining the swelling of materials in petroleum environment

The swelling of blended rubber materials in some liquid environments, including gasoline and oil, is performed according to TCVN 2752: 2008 [114] or ISO 1817 - 2005. The principle of the method is to determine the change in mass, change in volume or change in dimensions, surface area of ​​the blended rubber sample before and after immersing the test sample in gasoline, oil, etc. environments.

The percentage change in mass ∆m (%) of blended rubber is calculated by the formula:


In there:

( m )

m 0

m1 x 100

m 0


m0 is the mass of the sample before immersion (g) ;

m1 is the mass of the sample after immersion (g).

Results are averaged from 5 measurements.

2.2.2.7. Method for determining the aging coefficient of materials

a) Method for determining the aging coefficient of blended rubber materials according to TCVN 2229-77 standard [115]

The samples are prepared according to the specified standards and placed in a Memmert oven (Germany) at 70 o C (or 100 o C) for 24, 48, 72, 96, 144,... hours. After the specified time, the samples are taken out and left to stand for at least 4 hours at room temperature and no more than 96 hours, then the properties of the samples are measured after performing the aging test.

The aging coefficient ( K B ) of the material is calculated by the product of the tensile strength and elongation at break before and after aging according to the formula:

K

Z 2

B Z


In there :

1


Z 1 is the product of tensile strength and elongation at break before aging;

Z 2 is the product of tensile strength and elongation at break after aging.

Results are averaged from 5 measurements.

b) Method for determining the aging coefficient of materials in a humid heat radiation environment according to ASTM D4587-91 standard [116]

The specimens were cut into 10 x 14 (cm x cm) rectangles and placed on an aluminum plate in an ATLAS (USA) UVCON accelerated weathering chamber. The testing regime was cyclical, with each 12-hour cycle consisting of 8 hours of UV radiation at 340 nm, 70 o C temperature and 4 hours of condensation at 50 o C. After a certain number of cycles (2, 4, 6, 8, 10,… testing cycles), the specimens were measured for their physical and mechanical properties (tensile strength, elongation at break, hardness, etc.).

Aging coefficient ( K B ) is calculated by the product of tensile strength and elongation at break before and after aging according to the formula:

K

Z 2

B Z


In there :

1


Z 1 is the product of tensile strength and elongation at break before aging;

Z 2 is the product of tensile strength and elongation at break after aging.

Results are averaged from 5 measurements.

2.2.2.8. Scanning electron microscopy (SEM) method

To study the morphological structure of the material, we used the scanning electron microscope (SEM) method: the material sample was immersed in liquid nitrogen, fractured and then sliced ​​with a thickness of about 1 mm. Then the sample was mounted on a support, the cut surface of the sample was coated with a thin layer of Pt, by the method of evaporation in a vacuum under voltage to increase the contrast. The sample was placed in the measuring chamber of the scanning electron microscope to take pictures of the fracture surface.

2.2.2.9. Thermogravimetric analysis (TGA) method

Thermogravimetric analysis (TGA) is a method of analyzing the continuous change in mass of a sample with increasing temperature. This method provides information on the temperature of onset of decomposition, the rate of decomposition and the percentage of mass loss of the material at different temperatures. The TGA analysis of the blended rubber sample was performed on a SETARAM (France) machine. The conditions for thermogravimetric analysis are as follows:

+ Environment: air;

+ Temperature increase rate: 10 o C/min;

+ Research temperature range: from 30 o C to 800 o C.

2.2.3. Experimental planning method

The experimental planning method is a modern method for studying multicomponent systems. Experiments are carried out according to a pre-established plan with simultaneous changes of factors that allow to establish the level of interaction between them and thus significantly reduce the number of experiments. The studied property of the system is a continuous function of the arguments (the composition of the components that make up the system) and is often represented in the form of a polynomial that describes the system with considerable accuracy from a statistical point of view, through which the optimal composition ratio of the system under study can be determined [117, 118, 119]. To determine the optimal composition ratio of the three-component system NBR/CR/PVC, we performed the following methods:

2.2.3.1. Statistical experimental model based on passive experimental results

The statistical experimental model based on passive experimental results is a general model established based on passive experimental results that do not follow a predetermined mathematical model. From the experimental data set, we will process to find the average value, variance, test the homogeneity of the variances and on that basis calculate the experimental reproduction variance of tensile strength, elongation and hardness. Next, we will establish a mathematical model and evaluate the compatibility of that model by comparing the difference between the calculated value according to the model and the experimental value or evaluate through statistical standards. Assuming the three-component system NBR/CR/PVC has the corresponding components x 1 , x 2 , x 3 , we will calculate the average value y from the measurement results y 1 , y 2 , y 3 according to the formula:

m

what​​

y j 1 ;

m

i 1, n

(2.1)

i

Variance s 2 according to the following formula:

m

y ji

y 2

i

s 2

j 1

m 1

; i 1, n

(2.2)


From the largest variance value s 2 max among n values ​​of s 2 j and calculate the norm

Comment


Agree Privacy Policy *