RESULTS AND DISCUSSION

RESULTS AND DISCUSSION

3.1 SELECTION OF FACTORS:

The quantity of CaCO₃ in the master batch and the let down ratio of the master batch into the virgin matrix were chosen as the two variables, combinations of these factors are changed according to the design. The let down ratio of the filler was chosen as one of the variables because the mechanical properties are dependent on the amount of the filler present in the virgin matrix.

3.1.1 FIXING OF + / - LEVELS OF THE FACTORS:

Calcium Carbonate was chosen as the filler, the filler level was varied from 1% to 29% in the virgin matrix, and the level of calcium carbonate in the master batch is the other factor, which is varied from 56% to 84%.

Table 3.1 Coded levels for the factors

Variable	Code	-1.414	-1	0	+1	+1.414
% of CaCO3 In Master Batch	X1	56	60	70	80	84
Let down ratio	X2	1	5	15	25	29

3.2 OPTIMIZATION OF FILLER RATIO:

The CaCO₃ filled master batch was mixed with the virgin matrix as per the proportions shown in the design table. Then the compounds are prepared and they are characterized for mechanical properties such as Tensile strength, Modulus, Hardness, etc. as explained in the chapter 2.

3.3 REGRESSION ANALYSIS:

The regression analysis is performed to generate a response equation, which consists of the main, quadratic and the interaction terms. Simultaneously the P – value, R – square value and the adjusted R – square value are calculated. Factors for which the P – value are, less than 0.05 are said to have an impact on the property that is being evaluated. The factors with positive co – efficients have a positive effect on the property and vice – versa.

Table 3.2 Two variable design matrix for CaCO₃ filled HDPE using CCD

	CODED		UNCODED
Trial	X1	X2	X1	X2
1	-1	-1	60	5
2	-1	+1	60	25
3	+1	-1	80	5
4	+1	+1	80	25
5	-√2	0	56	15
6	+√2	0	84	15
7	0	-√2	70	1
8	0	+√2	70	29
9	0	0	70	15
10	0	0	70	15
11	0	0	70	15