Shrinkage maximum, equation

Two extreme cases can be predicted for the shrinkage of an LCP molded part based upon 3-dimensional CTE data. In the first case the part is assumed to shrink from the melt temperature (Ts) to room temperature (Tf). Here it is postulated that no real part packing occurs during molding. For the second case, the part is assumed to cool from the mold temperature (Tm) to room temperature. For this case, maximum packing would occur. For cooldown from melt temperature, the equations are ... 

So far as shrinkage s definition 0 = d(lnV )/dt leads to = V exp then for the finished process of consolidation at the first stage the maximum shrinkage is = GlX then from the last but one equation for nic we receive... 

This equation describes quite accurately the situation of an adhesive drop on a solid surface. The surface energies do not alter profoundly as the liquid solidifies, although stresses may build up due to shrinkage. Hence, the equation is also valid for the situation of a solid adhesive on a substrate. It follows that the adhesion maximum is obtained when cos0 = 0, that is when the liquid spreads completely. This implies the existence of larger forces between the liquid molecules and the solid, compared to that between the liquid molecules themselves, which further implies a high tt v value. The adhesive force will tend to zero for contact angles above 90°, in which case is small. 

FIGURE 4.5 Dimensionless velocity of spreading (v+, solid line) and velocity of drop shrinkage (v, dotted line) on dimensionless time, calculated according to Equation 4.75. Intersection of these two dependences determines the value of the dimensionless time 0.08, when the radius of the drop base reaches its maximum value, = 1 (in dimensionless units). 

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