Modification of isotactic polypropylene by the free‐radical grafting of 1,1,1‐trimethylolpropane trimethacrylate

Abstract

The chemical modification of isotactic polypropylene was performed by the free-radical-promoted grafting of 1,1,1-trimethylolpropane trimethacrylate (TMPTMA) in the presence of dicumyl peroxide (DCP) as the initiator. The reaction was carried out both in a batch internal mixer and in a corotating twin-screw extruder; the effects of the peroxide and monomer concentrations on the extent of modification in terms of the grafting efficiency and polymer chain structure variations were investigated. The modified samples were characterized with Fourier transform infrared to determine the structure of the grafted groups and the degree of functionalization, with gel permeation chromatography and the melt flow index to evaluate changes in the molecular weight, and with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis to measure the final thermal properties. In addition, solvent extrac-tion with xylene was performed to highlight the presence of gel and its extent. The structure of the grafted groups was determined, and the number of grafted groups was quantitatively evaluated. The degree of functionalization increased with an increasing TMPTMA/DCP molar ratio. Thermal analysis results hinted at the presence of grafted chains with an increased percentage of TMPTMA. Although degradation reactions predominated at high amounts of peroxide, grafting and branching processes became competitive at high levels of TMPTMA. The balance between competing b-scission and grafting/branching reactions could be adjusted on the basis of feed conditions. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 950-958, 2007

Foaming of reactively modified polypropylene: Effects of rheology and coagent type

“…These include an increase in the crystallization temperature and crystallization rates. 8–10 We have recently attributed this phenomenon to the formation of coagent-rich cross-linked nanoparticles that form within these systems and act as nucleating sites for crystallization and foaming. 11…”

Surface functionalization of polypropylene‐bearing isocyanate groups in solid state and their cyclotrimerization with diisocyanates

“…T m of the PP‐modified has declined from the pure PP beads. This may be due to the grafted TMI short chains that form a disordered branched structure, which destroyed the uniform molecular structure of PP chains . The degradation of the polymer chains during PP modification was also one of the reasons.…”

The effect of tunable modification parameters on the structure and properties of polypropylene with cyclotrimerization surface of isocyanates

“…Likewise, the TG spectrum in Figure and the data in Table showed that T d5 and T d10 of PP‐g‐TMI decreased significantly compared with the pure PP beads; after cyclotrimerization was completed, the decomposition temperatures likely increased. In the first stage, T m and T d decreased because the regular structure of the PP chains was disrupted; the PP chains were disrupted because the grafted TMI is a short chain forming a randomly branched structure . The networked structure consisted of heterocyclic rings formed through cyclotrimerization.…”

“…In the first stage, T m and T d decreased because the regular structure of the PP chains was disrupted; the PP chains were disrupted because the grafted TMI is a short chain forming a randomly branched structure. 30 The networked structure consisted of heterocyclic rings formed through cyclotrimerization. These rings were rigid structures limiting the motion of chains.…”