The phase behavior of the binary system consisting of the commercial nucleating and clarifying agent 1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol (DMDBS, Millad 3988) and isotactic polypropylene (i-PP) was investigated over the entire concentration range by means of differential scanning calorimetry (DSC), rheology, and optical microscopy. Experimental phase diagrams were constructed from data obtained in melting and crystallization studies, and a simple binary monotectic is advanced. Distinct regimes in the phase diagram, which apparently dictate nucleation and clarification of i-PP by DMDBS, are discussed. A maximum increase in the crystallization temperature of i-PP due to the nucleating action of DMDBS was observed in compositions containing between 0.2 and 1 wt % of the latter. Liquid−liquid phase separation was observed at elevated temperatures for i-PP/DMDBS mixtures comprising more than 2 wt % of DMDBS. A study of the optical properties of the i-PP/DMDBS system revealed that values for haze and clarity of injection-molded plaques progressively decreased and increased, respectively, in the concentration range between 0.2 and 1 wt % DMDBS in i-PP; at DMDBS concentrations exceeding 1 wt % the presence of the additive had an adverse effect on the optical properties of i-PP. Finally, a surprisingly strong influence of cooling kinetics on the phase behavior and, consequently, on the optical properties of the i-PP/DMDBS system was detected, which is of obvious relevance for industrial applications.

We report the discovery of a family of organic compounds, substituted 1,3,5-benzenetrisamides, thatsdepending on subtle details of their chemical structuresare capable of selectively and extremely efficiently nucleating the growth of the common R-crystal modification of the major industrial polymer isotactic polypropylene (i-PP), rendering this normally turbid material highly transparent ("clarified") at exceedingly low concentrations (as low as a weight fraction of 0.0002), inducing the mechanically distinct, tough i-PP β-polymorph, or promoting growth of hybrids of both crystallographic modifications with heretofore unknown combinations of the above desirable optical-mechanical properties. In addition, these trisamide-based compounds exhibit excellent thermal stability and do not feature absorption of visible light, adding to a most favorable set of characteristics that provides marked benefits over the presently employed nucleating/clarifying agents.

Structural studies of substituted 1,3,5-benzenetrisamides, a new family of highly versatile and efficient nucleating and clarifying agents for polymeric materials, are reported. Subtle details of the molecular structure of these species are shown to have a major influence on their solid-state order, morphology, and ability to nucleate specific polymorphs of isotactic polypropylene and induce a broad spectrum of useful mechanical and optical properties in the latter material.