Thiol-ene chemistry with TEMPO as an initiator has been utilized to synthesize a first-generation dendrimer having eight peripheral hydroxyl groups. Long chain branched impact copolymer polypropylene (ICP) and linear low-density polyethylene (LLDPE) were prepared by a postreactor modification process by a meltgrafting dendrimer onto a polyolefin chain using peroxide and maleic anhydride as a co-agent. Long chain branching in ICP controlled the chain scission initiated by peroxide by increasing entanglement, while for LLDPE, it controlled the excessive crosslinking because of peroxide. Neat and modified ICP and LLDPE samples were analyzed by FT-IR, TGA, DSC, HT-GPC, MFI, and parallel-plate rheometry as well as for their melt strength. The presence of long chain branching was mainly confirmed by time−temperature superposition (TTS) analysis obtained using a parallel-plate rheometer. In comparison to neat polymers, modified ICP and LLDPE samples showed higher values of Arrhenius flow activation energy. In the case of ICP, higher processability was observed for a dendrimer-grafted sample, while modified LLDPE samples exhibited higher melt strength as compared to neat polymers. Van Gurp−Palmen plots showed a decrease in phase angle as a function of angular frequency for modified ICP and LLDPE samples, which also confirmed their thermorheological complex behavior.

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Mesoporous silica was evaluated as functionalized filler in impact copolymer polypropylene (ICP) in its original form as well as after organic modification. Mesoporous silica was synthesized by base-catalyzed hydrolysis of tetraethyl orthosilicate in the water–acetone medium. The organic modification of mesoporous silica was carried out using commercially available silane with a terminal unsaturated bond and by synthesizing silane precursor by chemical treatment via TEMPO-initiated thiol–ene chemistry to introduce alkyl chains terminating in hydroxyl groups. The characterization for all types of mesoporous silica prepared was done using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). ICP–mesoporous silica composites were prepared using 1, 5, and 10 phr mesoporous silica and organically modified mesoporous silica loading via reactive compatibilization and were tested for their thermal, morphological, rheological, and mechanical properties. The addition of mesoporous and organically modified mesoporous silica enhanced thermal stability and nucleation with respect to neat ICP. Tensile and flexural moduli were improved while maintaining their impact strength. Analysis of rheological properties revealed a rise in zero-shear rate viscosity in ICP–mesoporous silica composites. DMA studies showed higher storage and loss modulus with the addition of mesoporous silica in ICP.

Polypropylene (PP) was blended with branched polyethylenimine (PEI) with the aim to prepare blends having CO 2 adsorption property. The CO 2 adsorption properties will be conferred due to the presence of variety of amine functionality in PEI. PEI contains primary, secondary as well as tertiary amine groups. Before testing CO 2 adsorption, PP-PEI blends were characterized using variety of techniques, for example, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and polarized light optical microscopy. In this work, we have studied in detail both compatibilized as well as noncompatibilized blends of PP and PEI. The compatibilization was achieved via addition of maleic anhydride grafted PP. Finally, all the compatibilized as well as noncompatibilized blends were studied for CO 2 adsorption. The compatibilized blends showed better thermal, mechanical as well as CO 2 adsorption properties as compared to the noncompatibilized blends. POLYM. ENG.

A generation two dendrimer (G2) having eight terminal double bonds has been prepared via esterification reaction from a dendritic precursor having eight hydroxyl end groups (G1). The reactive extrusion of impact co-polymer polypropylene (ICP) with G1 resulted in improved processability while leading to enhanced melt strength in the case of linear low-density polyethylene (LLDPE). G2 being an extension of G1, was melt grafted on ICP using a radical initiator to introduce long-chain branching in the polymer backbone. The prepared samples were analyzed for their molecular weight distribution, thermal, rheological properties, and mechanical properties. Thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) analysis showed higher thermal stability and slightly higher crystallization temperature with grafting of G2 on ICP. The rheological analysis through melt flow index measurements and parallel plate rheometer indicated higher processability, melt strength, complex viscosity, and zero-shear viscosity for ICP grafted with an optimized amount of G2. The presence of long-chain branching was confirmed with an increase in activation energy for ICP modified with G2 as compared to neat ICP. Modified ICP samples retained their bulk mechanical properties as neat ICP.

In this paper, isothermal and non-isothermal crystallization behaviour of neat polypropylene (PP), blends of PP/maleic anhydride grafted polypropylene (PP-g-MA), and PP/PP-g-MA/polyethylenimine (PEI) has been studied by differential scanning calorimetry (DSC). DSC analysis confirmed that PEI promotes crystallization of PP for blends compatibilized with reactive co-agent PP-g-MA, that was confirmed by decreased crystallization time in compatibilized PP-PEI blends as compared to neat PP. The Avrami equation has been used to analyze isothermal crystallization kinetics for all the compositions. Determined Avrami exponent's (n) values confirmed three-dimensional crystal growth in all the samples and PP sample with 1% PEI and 1% PP-g-MA (PP/1PP-g-MA/1PEI) was found to have the least crystallization half time (t 1/2 ). In addition to this, activation energy (∆E a ) for PP/1PP-g-MA/1PEI blend decreased remarkably as compared to neat PP. The non-isothermal crystallization kinetics was studied by Jeziorny extended Avrami and Mo theories. Application of Jeziorny-Avrami equation showed larger value of log k' in case of PP/1PP-g-MA/1PEI indicating enhanced rate of crystallization. Lower value of Mo's parameter F(T) for PP/1PP-g-MA/1PEI than neat PP established higher crystallization rate for the compatibilized blend and hence supported the prior results.

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