Effective dissolution of UHMWPE in HDPE improved by high temperature melting and subsequent shear

Abstract

A simple and effective way was expected to improve the blending of ultra-high-molecular-weight polyethylene (UHMWPE) in high-density polyethylene (HDPE) matrix. HDPE/UHMWPE blends were subjected to high temperature melting (HTM) at 280 C for up to 10 h, followed by shear at 175 C. These results were examined by scanning electron microscopy, polarized optical microscopy, and melt rheological behavior. UHMWPE particle was swelled partially during HTM, and this swollen region could be peeled from the particle by the subsequent shear, which resulted in more "dissolution" of UHMWPE in HDPE matrix. These results were also validated by the rheological behavior. POLYM. ENG. SCI., 55:270-276, 2015. 273 FIG. 7. Storage modulus G 0 (a) and tan deltas tan d (b) as function of the frequency for different samples. FIG. 8. Schematic diagram of changes in morphology of HDPE/UHMWPE blend.

Short‐time fabrication of well‐mixed high‐density polyethylene/ultrahigh‐molecular‐weight polyethylene blends under elongational flow: morphology, mechanical properties and mechanism

“…However, Fig. (b) shows very few dark spots with a size of 30–50 µm for the sample from the ERE; the cauliflower‐like dark zones seem to be partially ‘dissolved’ UHMWPE particles . This might be attributed to that UHMWPE phase was ‘dissolved’ in the HDPE matrix, and a few partially ‘dissolved’ UHMWPE particles were dispersed in the HDPE matrix.…”

“…Figure (b) shows that the G ′ gradually changes from lower than G ′′ to higher than that with increasing UHMWPE content. Compared to pure HDPE, the intersection between G ′ and G ′′ gradually shifted to low‐ ω zone until disappearing, which indicated an increasing relaxation time and a distinct solid‐like response . The time–concentration superposition principle is used to further explain the liquid‐to‐solid transition by shifting all curves on top of one another .…”

“…Figure shows that the particle size of neat UHMWPE powder was 200–300 µm. Generally speaking, the UHMWPE particles not dispersed in the matrix appear darker than the HDPE matrix because of fewer scattered incident electrons due to the lower crystallinity of UHMWPE . Therefore, the shape, size and quantity of dark area can be used to analyze the dispersion of UHMWPE in the matrix.…”

“…(a), where the dark UHMWPE phase has a size of 100–200 µm that is close to the size of original UHMWPE powder. This indicated that there was almost no motion of UHMWPE chains to the HDPE matrix due to the ultrahigh entanglement of UHMWPE chains; therefore, UHMWPE phase dispersed in the matrix in the form of as‐received particles …”

“…Little melting UHMWPE could diffuse into the HDPE matrix, while diffused UHMWPE chains could play a role in toughening and nucleating as well as improving the abrasion resistance of the matrix . Some researchers employed the two‐step processing method to prepare effective dispersed HDPE/UHMWPE blends which presented an improvement in mechanical properties . Those investigations achieved good dispersion of UHMWPE in the HDPE matrix with the assistance of pre‐ or post‐processing compared to the single mixing process; however, these are not yet continuous and economical processing techniques for industrial production due to the long time and large energy consumption.…”