Effect of the ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends on their physical properties

This study examined the effect of the ultradrawing behavior of gel film specimens of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and UHMWPE/low‐molecular‐weight polyethylene (LMWPE) blends on their physical properties. The concentration of a gel film approximated its critical concentration at a fixed drawing temperature; its achievable draw ratio was higher than that of other blend specimens with various concentrations. Noticeably, when about 5 wt % LMWPE was added to a UHMWPE/LMWPE gel film specimen, the achievable draw ratio of the gel film increased, and this contributed to an apparent promoting effect on its anticreeping properties and thermal stability. Therefore, when UL_B?0.9 was drawn to a draw ratio of 300, the anticreeping behavior was improved to less than 0.026%/day. Moreover, with respect to the thermal stability, when the same specimen was drawn to a draw ratio of 300, the retention capability of its storage modulus could resist a high temperature of 150°C, which was obviously much higher than the temperature of an undrawn gel film specimen (70°C). To study these interesting behaviors further, this study systematically investigated the gel solution viscosities, anticreeping properties, dynamic mechanical properties, thermal properties, molecular orientations, and mechanical properties of undrawn and drawn UHMWPE/LMWPE gel film specimens. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Ultradrawing behavior of one- and two-stage drawn gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends

The ultradrawing behavior of gel films of plain ultrahigh molecular weight polyethylene (UHMWPE) and UHMWPE/low molecular weight polyethylene (LMWPE) blends was investigated using one- and two-stage drawing processes. The drawability of these gel films were found to depend significantly on the temperatures used in the one- and two-stage drawing processes. The critical draw ratio (λ_c) of each gel film prepared near its critical concentration was found to approach a maximum value, when the gel film was drawn at an “optimum” temperature ranging from 95 to 105°C. At each drawing temperature, the one-stage drawn gel films exhibited an abrupt change in their birefringence and thermal properties as their draw ratios reached about 40. In contrast, the critical draw ratios of the two-stage drawn gel films can be further improved to be higher than those of the corresponding single-stage drawn gel films, in which the two-stage drawn gel films were drawn at another “optimum” temperature in the second drawing stage after they had been drawn at 95°C to a draw ratio of 40 in the first drawing stage. These interesting phenomena were investigated in terms of the reduced viscosities of the solutions, thermal analysis, birefringence, and tensile properties of the drawn and undrawn gel films. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 149–159, 1998     

Ultradrawing properties of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends prepared at various formation temperatures

The ultradrawing behavior of ultrahigh‐molecular‐weight polyethylene/low‐molecular‐weight polyethylene film specimens prepared at various concentrations and formation temperatures was studied. The critical draw ratio (D_rc) of UL_?0.7 film specimens was found to depend significantly on the formation temperature used to prepare the film specimens. At any fixed drawing temperature, the D_rc values of UL_?0.7 specimens prepared at various formation temperatures increased significantly as the formation temperatures were reduced. In fact, with an optimum drawing temperature of 95°C, the D_rc values of UL_?0.7 specimens prepared at a formation temperature of 0°C reached 488, about 50% higher than that of UL_?0.7 specimens prepared at a formation temperature of 95°C. These interesting phenomena were investigated in terms of the thermal, birefringence, and tensile properties of these undrawn and drawn UL_?0.7 specimens. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3728–3738, 2003     

In situ fibre‐reinforced composite films of poly(lactic acid)/low‐density polyethylene blends: effects of composition on morphology,transport and mechanical properties

This study aimed to investigate the effects of blend composition on packaging‐related properties of poly(lactic acid) (PLA) and low density polyethylene (LDPE) blown films. Blend films with PLA contents of 5–20 wt% were produced and compared. Scanning electron micrographs of cross‐sectional cryofractured surfaces of the blend films revealed that in situ fibre‐reinforced composites were obtained. Viscosity ratio of the polymer components of ca 1 confirmed that fibre formation was favourable for this blend system. PLA microdomains were dispersed throughout the film in forms of long fibres (length‐to‐diameter ratio > 100) and ribbons. The number of fibres and ribbons increased with an increase of PLA content. Critical content of PLA was found to be 20 wt% for effective improvement of both moduli and gas barrier properties. Incorporation of poly[ethylene‐co‐(methyl acrylate)] compatibilizer showed minimal effect on PLA structure. However, it did improve moduli and O₂ barrier properties when sufficient amount (1.5 pph) was used in 10 wt% PLA/LDPE. In short, flow behaviour, ratio of polymer components and degree of compatibility together played intricate roles in the morphology and hence mechanical and transport properties of PLA/LDPE immiscible blends. © 2017 Society of Chemical Industry