Surface Recrystallization of Polyethylene Extended-Chain Crystals

Abstract

Rough fracture surfaces of extended-chain polyethylene crystals become unstable at temperatures below the bulk melting point. There is no way for the extended chains, which are up to 20,000 methylene units long, to change position without collapse. As a result, the rough surfaces smooth out on heating by covering themselves with oriented folded-chain lamellae.

Structural hierarchy and surface morphology of highly drawn ultra high molecular weight polyethylene fibers studied by atomic force microscopy and wide angle X-ray diffraction

“…From the annealing experiment, we can infer that the S130 fibers see temperatures in excess of 130 C during drawing. Wunderlich [46] demonstrated that chain folded crystals could be grown on the fracture surface of extended chain crystals by annealing the fracture surface at temperatures (120 C) approaching the onset of melting. While not specifically discussed in the context of polyethylene fibers, the same conditions may be present at the surface of a microfibril where areas on the uneven fiber surface are exposed.…”

Melt Crystallization and Morphology of Poly(p‐phenylene sulfide) under High Pressure

“…The striations run parallel to the molecular chain direction and their thickness ranges up to 200 nm, which approximately equaled the average length of the molecular chains 38,48,49. Figure 9(a) and 9(b) present two representative SEIs of the fracture surface of sample C9 crystallized at 200 MPa, 370 °C for 24 h. The lamellar crystals in the sample were coarser than the extended‐chain crystals of PE23 or PET,29 but were similar to the extended‐chain crystals of nylon 6 (PA6) 25. However, some extended‐chain crystals with the parallel striations exposed clearly were also detected in the sample, as designated in Figure 9(c), where an extended‐chain crystal with thickness up to 3.5 µm can be observed.…”

“…Endowed with a combination of three‐dimensional crystal ordering and long‐chain molecular orientational ordering, the extended‐chain crystals of polymers are an ideal system for studies on low‐dimensional physics and have potential applications as functional components,20,21 which is quite different from their metastable folded‐chain counterpart. After Wunderlich et al reported that polyethylene (PE) extended‐chain crystals with thickness of up to 3 µm could be formed under high pressure,22 many researchers have carried out investigations on high‐pressure crystallization behaviors of certain polymers and obtained their extended‐chain crystals 21–30. As for PPS, although a wide variety of morphologies of spherulites as well as single crystals were observed during the above‐mentioned investigations,5,31 the extended‐chain crystals of the polymer have not been prepared so far.…”

Growth of Large Polymer Extended‐Chain Single Crystals in a Poly(ethylene terephthalate)/Bisphenol A Polycarbonate Blend under High Pressure

“…The pictures reveal parallel striations more clearly, particularly pronounced in phase image. According to the investigation on other polymers, [4,5] the striations should run parallel to the molecular chains. The thickness along c-axis of the crystals in the highpressure crystallized PET/PC blend was beyond 100 mm.…”

“…[3,4] After the report that PE extended-chain crystals could be formed at high pressure, many researchers carried out investigations on high-pressure crystallization behaviors of some singlecomponent polymers, and obtained their extendedchain crystals. [2][3][4][5][6][7] However, the thickness of crystals was small and the growth time was long. For example, it took 200 h growing extended-chain crystals of PE with c-axis Summary: High-quality synthetic polymer extended-chain single crystals with c-axis thickness exceeding 100 mm are obtained in a polyethylene terephthalate/polycarbonate (PET/ PC) blend rapidly.…”