Rheometric study of the gelation and fusion processes of poly(vinyl chloride‐co‐vinyl acetate) plastisols with different commercial plasticizers

Evolution of the complex viscosity of pastes of PVC‐VA (vinyl chloride‐vinyl acetate copolymer) plasticized with different commercial plasticizers has been studied. Knowledge of the rheological behavior of the formulations allows for better understanding of the gelation and fusion processes. Twenty commercial plasticizers of different types and with different functional groups have been studied and are grouped into five families: phthalate esters with linear chains, phthalate esters with branched chains, adipates (normal and polymeric), citrates, and rest of the plasticizers (carboxylates, alkylsulfonates, and pentaerythritol ester derivatives). Interesting relationships among the observed rheologies and the nature and molecular weight of the plasticizer have been observed. The evolution of the complex viscosity with temperature—at the temperatures where the blowing agents normally used in PVC plastisol foaming processes generate the main amount of gas—has been newly discussed with regard to the chemical structure and molecular weight of all of the plasticizers used. It was found that several different dynamic processes must be synchronized in order to understand the relationships among the chemical structure, plasticization, plasticizer compatibility, rheological properties, and foaming process of such materials. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Effects of vinyltrimethoxy silane on thermal properties and dynamic mechanical properties of polypropylene–wood flour composites

The viability of vinyltrimethoxy silane was investigated as a coupling agent for the manufacture of wood–plastic composites (WPC). The effect of silane pretreatment of the wood flour on the thermal and the dynamic mechanical properties and thermal degradation properties of the composites were studied. Moreover, the effect of organosilane on the properties of composites was compared with the effect of maleated polypropylene (MAPP). DSC studies indicated that the wood flour acts as a PP-nucleating agent, increasing the PP crystallization rate. In general, pretreatment with small amounts of silane improved this behavior in all the WPCs studied. Thermal degradation studies of the WPCs indicated that the presence of wood flour delayed degradation of the PP. Silane pretreatment of the wood flour augmented this effect, though without significantly affecting cellulose degradation. Studies of dynamic mechanical properties revealed that the wood flour (at up to 30 wt %) increased storage modulus values with respect to those of pure PP; in WPCs with a higher wood flour amount, there was no additional increase in storage modulus. Pretreatment of the wood flour with silane basically had no effect on the dynamic mechanical properties of the WPC. These results show that with small amounts of vinyltrimethoxy silane similar properties to the MAPP are reached. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nanoclay‐reinforced poly(butylene adipate‐co‐terephthalate) biocomposites for packaging applications

Increasing generation and inadequate disposal of waste progressively compromise our environment. Solutions are proposed by the development of biodegradable polymers, that is, for short‐term applications like packaging. The present study focuses on the design and characterization of biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) nanocomposites reinforced by different types of nanoclays. The addition of natural and modified montmorillonite and bentonite to PBAT by melt mixing enhances slightly the thermal stability and increases the crystallization temperature, independently of the fillers' dispersion state. By contrast, storage modulus in dynamic mechanical analysis is increased when adding nanoclay, and improvement is higher for well‐dispersed organomodified fillers. Dispersion states and morphology of the nanocomposites are studied by X‐ray diffraction as well as scanning and transmission electron microscopy. PBAT‐based composites with modified bentonite reveal to show the best performance at room temperature (which is the temperature of interest for potential packaging applications) in comparison with the other investigated nanocomposites.POLYM. COMPOS., 33:2022–2028, 2012. © 2012 Society of Plastics Engineers