Nanofibrillar surface structures of gel‐drawn UHMW‐polyethylene tapes

Abstract

The fibrillar structure of gel-drawn ultrahigh molecular weight polyethylene was studied by scanning force microscopy (SFM), transmission electron microscopy (TEM) and 'H-NMR. Periodically striped 20-50 nm wide nanofibrils were depicted at the surface of the ultradrawn tapes. A periodicity of about 25 nm was observed independently of the draw ratio in the range 10 = A S 70. This is consistent with the long period derived from SAXS experiments. The stripes were more pronounced at low draw ratios and a short range interfibrillar correlation was detected in that case. Based on variations in the 'H-NMR relaxation times and segment orientation, it is concluded that structural defects are concentrated within small domains inside the crystallites and that the striped structure originates from defect layers within the fibrillar crystallites.

Scanning Force Microscopy on the Orientation of Gel‐Crystallized Ultrahigh Molecular Weight Polyethylene

“…Scale bar = 250 nm [loll are offered by the rather recently developed friction (lateral force) and tapping modes*.Figure 17shows SFM micrographs which were recorded from the same area of a drawn tape (A = 10) by four different modes. A normal force micrograph depicts just the nanofibrils with a diameter of 50 nm, while the lateral force and tapping modes were able to visualize a regular pattern along the nanofibrils with a periodicity of 26 nm[64]. This periodicity is consistent with the long period of gel-drawn PE derived from SAXS data[lo].…”

“…Enlargements of the scanning force micrographs of Figure 8; (a) location 3; (b) location 4; (d) location 5; (e) location 6. Scale bars = 1 p. The twodimensional profile was taken from (a) along the A-A line [64] oriented parallel to the draw direction. This orientation is seen even more clearly in Figure 9(b).…”

“…Photograpic image of a neck drawn melt crystallized (a) and solution crystallized (b) UHMW PE film; the elonagtion in the neck is X = Transmission electron micrographs of polyethylene lamella crystallites which have been picked up with a cellulose acetate replica a t the surface of the necking region[64] …”

Adhesion properties on nanometric scale of silicon oxide and silicon nitride surfaces modified by 1‐octadecene

“…Thus, the total adhesion force is estimated as the sum F ad C F cap . 23 We suppose that in the case of hSiNi and hSiOi uncovered substrates capillary forces play a major role because of their superior hydrophilicity. 23 In particular, for a small spherical tip the capillary contribution to the adhesion force can be calculated as…”

New Developments in Polymer Analytics II

“…In the first one, the scanning force microscope is used to examine structure of either ex-situ [84,88,409,410] or in-situ deformed samples [411]. In these experiments, the tip was used as a "passive probe" to obtain submicrometer information about structure changes caused by uniaxial stretching of amorphous polystyrene [409], ultra-high-molecular-weight polyethylene [84,410], and hard elastic polypropylene [411]. In the second and more interesting approach, the SFM tip has been used as an "active probe" which both deform the sample and simultaneously measures the reaction force as well as the induced deformation [67,70,115,122,136,159,412,413].…”