Cryogenic mechanical milling of high density polyethylene

Abstract

HDPE was analyzed after being submitted to cryogenic mechanical milling (CMM) by X-ray diffraction (WAXS), polarized light microscopy and differential scanning calorimetry (DSC). After CMM, besides the known phase transformation of the orthorhombic PE crystals into the monoclinic modification, slight changes in the melting and crystallization behavior as well as an unexpected increase in crystallinity were observed. The observed results can be explained by assuming a solid/solid phase transition as the responsible mechanism.

Effect of high‐energy ball milling on the structure and mechanical properties of ultra‐high molecular weight polyethylene

“…Figure shows that whereas before the deformation the UHMWPE powder preferentially consisted of an amorphous phase (a halo with center at 2θ = 19.45°) and an orthorhombic crystalline phase [with two intensive peaks at 2θ = 21.5° (110) and 2θ = 23.9° − (200)], after deformation a new peak appeared at 2θ = 19.55°. This peak corresponded to the monoclinic phase, which is usually formed in PEs as a result of deformation processes, including ball milling . An increase in the milling time resulted in an increase in the related monoclinic phase peak intensity.…”

“…Both the amorphous and crystalline phases took up orientation of the plane perpendicular to the applied impact. Structural orientation as the result of polymer particles flattening during ball milling has also been proposed for polyethylene (PE) and poly(ethylene terephthalate) …”

Mechanical milling as a technology to produce structural and functional bio-nanocomposites

“…17,66,[83][84][85] Similar reports showed that polymers undergo either a crystalline phase transition or a simple amorphization when they are subjected to mechanical milling. 86 Milling overcomes some problems associated with conventional blending methods such as thermal degradation due to excessive heating in the melting process, or the difficulty in removing the polymer from the solvent if the solution method is used. 71 …”

Characterization of polymer properties and identification of additives in commercially available research plastics

“…87,89 Increased crystallinity in polymers may occur because mechanical work during cryomilling provides enough heat to overcome the cold crystallization temperatures locally, or from strain mediated crystallization. 88,90 Researchers in one study found that changes induced by cryomilling are primarily physical in nature and can be erased by thermal treatment. 91 SAXS and WAXS were used to observe structural changes after cryomilling.…”