Rheological and mechanical properties of blends of LDPE with high contents of UHMWPE wastes Jeanette Gonz  alez, 1 Carmen Rosales, 1 Marco Gonz  alez, 1 Natalia Le  on, 1 Roberto Escalona, 3 H  ector Rojas 2 1 Dpto. de Mec anica, GPUSB II, Universidad Sim on Bol  ıvar, Apdo. 89000, Valle de Sartenejas, Caracas, Venezuela 2 Laboratorio de Materiales y Manufactura “E”, Universidad Sim on Bol  ıvar, Apdo. 89000, Valle de Sartenejas, Caracas, Venezuela 3 Coordinaci on de Ingenier  ıa de Materiales, Universidad Sim on Bol  ıvar, Apdo. 89000, Valle de Sartenejas, Caracas Venezuela Correspondence to: J. Gonz alez (E - mail: jjgonza@usb.ve) ABSTRACT: The mixing of UHMWPE wastes with other polymers aims to reduce the environmental impact of waste materials. The dynamic rheological behavior of the blends, tensile and abrasion properties, Shore D hardness and impact resistance, and morphology are important in characterizing polymer blends. In this work, we have sought to obtain blends containing different proportions of UHMWPE wastes and LDPE with properties suitable for the manufacture of useful products. The blends exhibit an increase in com- plex viscosities, storage modulus, and Young’s modulus with increasing content of UHMWPE wastes and a decrease in both the max- imal elongation and Charpy impact resistance. Summarizing, the addition of up to 60 wt % of industrial fragments of UHMWPE is possible using conventional methods of processing to prepare blends with values of tensile strength, abrasion, and Shore D hardness similar to those of LDPE. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44996. KEYWORDS: industrial wastes; low density polyethylene; polymer blends; rheological properties; ultra-high molecular weight polyethylene Received 2 November 2016; accepted 15 February 2017 DOI: 10.1002/app.44996 INTRODUCTION Ultrahigh molecular weight polyethylene (UHMWPE) is among the polymers considered as engineering materials. Because of its self-lubricating nature and wear resistance, it is commonly used to make machine parts, such as gears and bearings, for the food and medical industries. The UHMWPE nascent powder does not flow under the usual plastics processing conditions because of its high molecular weight. This feature makes it difficult to process in conventional equipment like extruders or injection- molding machines. 1,2 On the other hand, conventional polyethylene (PE) is obtained in several ways, and each method produces materials with dif- ferent rheological, thermal, and mechanical properties that are due to their structural variations. Low-density polyethylene (LDPE) has a lower content of long-chain branches (1–3 per 1000 backbone carbon atoms) and short-chain branches (10–30 per 1000 backbone carbon atoms). Molecular parameters such as weight-average molecular weight (M w ), molecular weight dis- tribution (MWD), branch content, branch type, and their com- position distribution have a strong influence on the miscibility of blends of LDPE and high-density polyethylene (HDPE). 3,4 In other research works, the rheological and thermal properties of blends composed of a polyolefin as matrix and UHMWPE nascent powder as dispersed phase have been studied. These blends exhibited a rise in complex viscosities as well as in the storage and loss modulus with the increase in the proportion of UHMWPE nascent powder. This behavior was attributed to the addition of a polymer with very high molecular weight to the continuous phase, which restricts the mobility of the matrix. 5–7 Different techniques are reported for preparing polyolefin/ UHMWPE blends. These include solid-state shear milling tech- nology, melt mixing, sequential loading, coarse powder blending followed by injection molding, and solvent blending techni- ques. 8–10 The solvent blending technique seems to provide good homogeneity when UHMWPE is incorporated in conventional polyethylenes, but it is not efficient or environmentally friendly. The authors have found that in melt mixing, the incomplete melting of UHMWPE nascent powder resulted in dispersed UHMWPE particles, which greatly affects the final blend prop- erties. Moreover, in using solid-state shear milling technology, polymer degradation occurs by chain scission of the blend com- ponents. 8,9 Shen et al. 10 observed that the effective dispersion of UHMWPE in HDPE is achieved using a high melting tempera- ture followed by shearing. However, this methodology involves V C 2017 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2017, DOI: 10.1002/APP.44996 44996 (1 of 13)