H-Bonding leading to latent initiators for olefin metathesis polymerization

Improving Environmental Stress Cracking Resistance of High-Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach

The aim of this paper is to determine the effect of polymer density, correlated to the comonomer content, and nanosilica addition on the mechanical and Environmental Stress Cracking Resistance (ESCR) characteristics of high-density polyethylene (HDPE). In this regard, five HDPE samples with similar Melt Flow Index (MFI) and molar mass but various densities were acquired from a petrochemical plant. Two polymerization reactors work in series and differ only in the amount of 1-buene comonomer fed to the second reactor. To ascertain the microstructure of the studied samples, GPC and SSA (successive self-nucleation and annealing) analyses were accomplished. All samples resulted having similar characteristics but slightly various SCB/1000 C=7.26-9.74 (SCB=Short Chain Branching). Consequently, meanwhile studied HDPEs reveal similar notched impact and stress at yield values, the tensile modulus, stress-at-break, and elongation-at-break tend to demonstrate different results with the SCB content. More significantly, ESCR characteristic varied considerably with SCB/1000 C extent, so that higher amount of SCB acknowledged advanced ESCR. Notably, blending HDPE sample containing higher amount of SCB/1000 C, with 3 wt.% of chemically modified nanosilica enhanced ESCR characteristic by 40 %. DFT (Density Functional Theory) calculations unveiled the role of the comonomer, quantitatively by binding energies and qualitatively by Non Covalent Interaction (NCI) plots.

In-situ photo-crosslinkable elastomer based on polyalphaolefin/halloysite nanohybrid

In this research, new injectable and in situ photocurable elastomeric nanohybrids have been fabricated from polyalphaolefin (PAO) resins and halloysite nanofiller. In this regard, the co-oligomerization of long α-olefin monomers (C6, C8 and C10) with alkenol counterparts was carried out via a simple cationic route to provide OH-functionalized PAOs. The newly formed PAO type copolymer resins as well as halloysite nanoclay were then equipped with photocurable CC bonds containing an acrylate moiety. After the characterization of the final chemical substances and also of the intermediate structures, experimentally and computationally by means of Density Functional Theory (DFT) calculations, the neat treated PAO and PAO/halloysite nanohybrids were subjected to a curing process by visible light irradiation (λ ∼ 475 nm, blue light). The crosslinking efficiency of the neat resins and the formed nanohybrid was evaluated using shrinkage strain-time curves and equilibrium swelling method. The suggested nanohybrid is not only biocompatible (96 % in the MTT assay), and hydrophilic (with a water contact angle of 61°), but also exhibits an easy, fast and robust curing process with great potential for coating and sealing technologies for medical devices.