Influence of hydrogen bonding on the melt rheology of polypropylene

Abstract

The rheological behavior of hydroxyl-functionalized polypropylene (PPOH) copolymers modified with up to 3.9 mol% hydroxyl groups was compared with unmodified polypropylene (PP) in the melt state. The hydroxyl groups interacted via hydrogen (H-) bonding, the strength of which increased with increasing hydroxyl concentration. The hydrogen bonds persisted at temperatures as high as 250C, even though the H-bonding strength decreased with increasing temperature. A direct consequence of H-bonding was an increase in the elasticity, viscosity and relaxation time of the PPOH copolymers compared to PP, and also an increase in these properties with increasing hydroxyl concentration. The zero-shear viscosity exhibited a power-law relationship with the hydroxyl concentration,  0  [M v ] 3.6 [OH] 2 , which was found to be consistent with the predictions from Leibler-Rubinstein-Colby (LRC) theory for associating polymers. The PPOH copolymers exhibited apparent molecular weights 2-8 times higher than the actual molecular weights. The PPOH copolymer with 3.9 mol% hydroxyl groups displayed a gel-like behavior that suggested the formation of an elastic network in the melt presumably due to the phase separation of H-bonded OH groups into nanoclusters. The network, however, was weak since non-Newtonian viscous flow occurred under nonlinear deformations.

Evaluation of poly(4‐methyl‐1‐pentene) as a dielectric capacitor film for high‐temperature energy storage applications

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Synthesis of chloromethyl benzimidazole grafted polybenzimidazole with enhanced UV absorption and its effect as a stabilizer on the ultraviolet‐aging behaviors of poly(vinyl chloride) films

“…Samples underwent further UV degradation after 750 h of UV irradiation; this resulted in the formation of more carboxylic acid groups. Pure PVC also had certain numbers of carbonyl and hydroxyl groups before UV irradiation . The reason was that the thermooxidative aging during PVC synthesis resulted in a slight removal of small molecules, such as HCl, and the formation of carbonyl, carboxylic acid, and hydroxyl groups .…”

A triethylene glycol dimethacrylate- free dental composite for reduced water-sorption and shrinkage

“…The increase in CM may be attributed to the strong hydrogen bonds from the urethane linkage, which leads to an increase in elastic component. 24 In other words, the three ethylene glycol units on TEGDMA provide soft and flexible components to the system. 25,26 Furthermore, decreasing TEGDMA increased the viscosity but decreased DC, shrinkage and water sorption (see Table 4).…”