In particular, these properties depend on the degree of unsaturation
of the fatty acids, as well as the quantity and quality of the compounds present in the nonsaponifiable fraction .
In addition, chain branching is also affected by the MWD (and therefore by temperature and concentrations of butadiene and DEAC), as short chains can probably be incorporated at higher rates, given the higher mobility and availability of the internal unsaturations
of these chains.
Thorough mixing and careful control of halogenation ensures that only the small amount of unsaturation
reacts with the halogen by way of a substitution at the allylic position along the polymer backbone.
In a subsequent step (Process 1B), the unsaturation
sites provided by the grafted coagent serve as attachment points during reactive processing with peroxide and mercaptopropyltrimethoxysilane (MPTMS).
The spectrum does not show any peak at 2.8 ppm, which indicates that there is no contribution of bis-allylic protons ([--CH.sub.2], comprised between two unsaturations
The use of high sulfur to produce such compounds is not feasible with EPDM due to low levels of unsaturation
, particularly the lack of backbone unsaturation
17) also did not show an unsaturation
peak at 3155 [cm.sup.-1] indicating reaction of the added BMI.
Table 2 contains data on the various types of unsaturation
and tertiary hydrogens in the polyethylenes.
In practice, a standard titration is achieved with non-ozonized PE because It is known that Iodi ne can add up onto the unsaturations
of polyolefins (25).
It is postulated that as degradation proceeds, cross-linking occurs between the free radicals, facilitated by the presence of unsaturation
, causing the observed increase in the tensile modulus, and an increase in [T.sub.g] and loss modulus .
Moreover, in add ition to catalyst residues, the increased concentration of unsaturations
may influence stability [6, 8, 22].
In the case of unsaturated EPDM, crosslinks are also formed via addition of an EPDM macro-radical to the pendant unsaturation
of the third monomer.