No abstract

Based on the industrialized graphene (GN) product, a series of intrinsic flame-retardant urea-formaldehyde/ graphene-silane coupling agent (UF/GN-SA) nanocomposite foams were fabricated via in situ polymerization and water-based foaming process. It was found that at low GN content, GN sheets dispersed homogeneously in the foams. Compared with neat UF foam, the composite foam exhibited circular cells with smaller cell size, narrower cell size distribution, thicker cell walls, lower porosity, and less water absorption. Introduction of 0.5 wt% GN resulted in about 29.5% decrease in pulverization ratio, 71.8% increase in compressive strength, and 132.6% increase in compressive modulus. The reinforcing mechanism of the UF/GN-SA nanocomposite foam was explored. Due to the dense cell structure, formation of GN centered network structure, and reinforcing effect of GN, greater compressive stress was required to destruct the foam. UL-94 V-0 rating was achieved for the composite foams with remarkably suppressed flame expansion. POLYM. COMPOS., 40:E811-E820, 2019.

No abstract

A rare earth nucleating agent (RENA) was introduced to fabricate polyethylene (PE) pipe resin, which self‐assembled into various structures in PE melt during processing and further induced PE molecules to epitaxially crystallize on its surface to form, among others, a hybrid shish‐kebab crystalline structure due to good crystallographic matching between RENA and PE. Under stress, the shish structure formed by needle‐like RENA assembly arranged preferentially along the drawing direction, which was beneficial for an orderly arrangement of PE chains epitaxially crystallizing on its surface in the process of stress‐induced recrystallization and thus promoted the formation of a dense oriented crystalline structure with a large number of shish structures, resulting in higher degree of crystallinity and orientation, and lower long period and lateral size of lamellae than those of PE sample. By orientation, compared with PE sample at the same draw ratio, PE‐RENA samples showed much higher tensile strength and modulus. Especially, the oriented PE‐RENA pipes showed an approximately 96% and 100% increase in tensile strength along the hoop direction and internal pressure resistance, respectively, compared with unoriented pipe sample. This work provides a facile method for fabricating highly enhanced PE pipes with wide application prospects. © 2021 Society of Industrial Chemistry.

No abstract