Meaningful evaluation of plastisol gelation and fusion temperatures by dynamic mechanical analysis

Abstract

AbstractIn most PVC plastisol processing operations, gelation and fusion characteristics of the plastisol are critically important. For example, in chemically foamed plastisols, plastisol fusion temperature and blowing agent decomposition temperature must be carefully coordinated. In rotomolded parts, rates of gelation may determine the quality of the finished parts. For plastisol products made by any process, the final fusion temperature determines the processing temperatures required to give the finished product acceptable mechanical properties. For a variety of reasons, the methods commonly used to characterize plastisol gelation and fusion (hot bar test, resin in plasticizer clear point, torque rheometer measurements, etc.) provide comparisons between plastisols but do not provide temperatures that are easily related to actual industrial processes. With dynamic mechanical analysis (DMA), one can characterize, under low shear conditions, the temperatures at which gelation begins, gelation ends, and complete fusion occurs. Additionally, it is possible to record plastisol viscosities (and other dynamic mechanical properties) over the processing temperature range. We used a multiple linear regression program to analyze the DMA data for plastisols heated from 30 to 210°C and containing either 70, 80 or 90 phr of Jayflex dihexyl phthalate (DHP) or Jaylflex di‐isodecyl phthalate (DIDP). Further, we determined the plasticizer phr dependence and the reproducibility of gel and fusion temperatures given by data analyzed in this manner. Finally, for comparison, we analyzed the reproducibility of initial and final plastisol gel temperatures and fusion temperatures, which were determined by visually analyzing the DMA data for plastisols containing 70, 80, and 90 phr of Jyflex plasticizers DHP, Jayflex 77, diisononyl phthalate (DINP), and DIDP. Precise characterization of plastisol gelation and fusion behavior will, undoubtedly, facilitate substitution of plastisol ingredients as is often required by those who manufacture and process plastisols.