Primary molecular weight definition

Peptides extracted from casein with N, N-dimethyl formamide have complex electrophoretic patterns identical to those of the fraction first prepared by Long and co-workers and called X-casein (El-Negoumy 1973). These peptides are identical electrophoretically to those released by the action of plasmin, which is present in fresh raw milk, upon asr casein (Aimutis and Eigel 1982). Two of these peptides have tryptic peptide maps and molecular weights identical to those of a pair of the peptides produced by plasmin degradation of asl-casein. These peptides appear to be fragments of a8l-casein which are present in milk as the result of plasmin proteolysis. More definitive information on their primary structure is needed before nomenclature for these fragments can be established. 

In the SmC liquid crystals, the primary order parameter is the director tilt and not the spontaneous polarization. The polarization, therefore, is often called secondary-order parameter, and the SmC materials are called improper ferroelectrics. The main reason for this is the weakness of the dipole-dipole interactions in the molecules. The polar order can be estimated by the ratio of the actual spontaneous polarization and which is the value that would appear when complete polar order is assumed. From its definition, the polarization is the density of the molecular dipoles. Assuming molecular dipoles of 3 Debye ( 10 Cm) and typical molecular weight of 300 g, density of about 1 g/cm = 10 kg/m, we get that in 1 m we have 6 10 molecules, which would give Po 2 W C/m = 2000nC/cm. For a SmC with Pg <100 nC/cnP, this means that less than 5% of the dipoles are ordered in one direction. For this reason, in the first approximation the polarization is proportional to the tilt angle. This relation, indeed, is found to be true for materials with moderate or low polarization. However, for materials with large polarization, like Pg 500 nC/cm, the dipole-dipole interaction becomes considerable, and the proportionality is not true. The deviation is more pronounced at lower temperatures, when the dipole-dipole... 

Plasticizers may also be further subdivided into primary and secondary types. Primary plasticizers are those used as the sole plasticizer or as the major component of the plasticizer system. Secondary plasticizers are typically blended with primary plasticizers to improve certain performance properties such as reduced flammability and improved processing, or simply to lower cost. Acmally, there are some overlaps in these definitions, since some secondary plasticizers, can function as primary plasticizers when used at relatively low levels. An example is di-2-ethylhexyl adipate (DOA). DOA is often used as the sole or primary plasticizer in PVC meat wrap, typically at 30 parts per 100 of resin (phr). But it also functions as a secondary plasticizer when added at the 10 percent level to a general purpose plasticizer, for example to improve the low-temperature flexibility or flex rating of a PVC shoe sole. Other examples would include the use of a primary plasticizer, such the higher-molecular-weight phthalate diisodecyl phthalate (DIDP) for use as a minor component in blends with polymeric plasticizers to help improve processability or to lower costs. 

---