The cure mechanism of acrylic-melamine resin was studied by means of DSA (Dynamic Spring Analysis). The equation (1) on a degree of cure (X) was derived experimentally which might adequately represent the cure behaviour from the beginning to the end. in X1-m+ exp (c in X+ d) =ln ((1 m) kt) (1) Where, X= (E'r-E'ro) / (E'r∞-E'ro) E'ro, E' r and E'r∞=modulus of relative elasticity at t=0, t, ∞ respectively c, d and m=constant k=the cure rate constant t = cure time Equation (1) was obtained by the insert of the modification term, (c in X+ d), in equation (2) which was limitedly adapted to the initial cure behaviour. X 1-m= (1-m) kt (2) The modification term, exp (c in d), was derived from the ratio, texp/tcalc, where texp and tcale are time experimentally determined and time calculated from equation (2) at a given degree of cure (X) respectively. The modification term, exp (c in X+ d), was considered to be due to the decrease of the segmental mobility caused by network formation. This leads to equation (3) which indicates that X is the function of the formation of network structure, i. e., the cure rate constant (k) depends on a degree of cure. X1-m/ (1-m) =k (X) t (3) Where, k (X) =k exp (-d, Xc) k=k0 exp (-ΔEa/RT) k (X), k=cure rate constant ΔEa=apparent activation energy ko, d, and c=constant R= gas constant T= absolute temperature Equation (3) indicates that the cure rate constant (k) is a function of a degree of cure (X) which becomes smaller as the formation of the network proceeds, i. e., as a degree of cure (X) increases.
The graft polymerization of methyl methacrylate (MMA) onto the surface of color black (CB) has been investigated using CB-butyllithium (BuLi) complexes as catalyst and N, N-dialkylformamides, such as dimethylformamide (DMF), and related compounds as regulator. In the absence of DMF, a large quantity of gel containing CB particles yields and the grafting ratio, that is, the quantity of poly-MMA fixed on the surface of CB, is found to exceed 100 to 300% by weight for this grafting process. The gel fraction, however, decreases with an addition of DMF to MMA, consequently giving a colloidal product which forms a stable dispersion in organic solvents such as acetone. The grafting ratios also decrease with the increase in the concentrations of DMF. In addition, N, N-dialkylacetamides such as diethylacetamide are found to be efficient regulators. On the other hand, the reaction of BuLi with DMF is also known to give the amino alkoxide, BuCH (OLi) N (CH3) 2 (CA. 79, 91504n). The mechanism by which DMF regulates the gel formation is proposed to explain the experimental results.