High density polyethylene
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PE is a highly versatile and adaptable biomaterial utilized extensively in medical fields, especially for structural applications. Thus it should be kept from contact with halogenating agents and environments. In addition, high temperatures, ultraviolet light, and gamma irradiation lead to environmental oxidation of PE materials. Chemicals like nitric acid produce oxidative deterioration and affect the mechanical properties of PE. In terms of chemical properties, PE is inert, and there are no effective solvents to dissolve it at room temperature. Machined components are made from either a sheet or a bar, whereas compression-molded components are made by compressing powder particles into the desired shape. PE components are manufactured by machining or compression molding. As molecular weight increases, material strength also increases, while elasticity decreases. PE is categorized into five groups: low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE), and ultrahigh-molecular-weight polyethylene (UHMWPE). Cuie Wen, in Structural Biomaterials, 2021 12.5.2 Polyethylene Linear LDPE (LLDPE) has a greater proportion of short branches resulting in greater flexibility.Īnahita Rohani Shirvan. PE polymer chains can be extended to produce ultra-high molecular weight (UHMW) PE to give a very dense PE product. PE can be further modified by resin manufacturers to increase its structural and functional properties. HDPE is lightweight and possesses good tensile strength, while LDPE exhibits good chemical resistance. As an example, high-density PE (HDPE) has a comparatively more linear morphology and a higher degree of crystallinity than low-density PE (LDPE). These characteristics allow PE products to be tailored for a variety of uses. An especially convenient quality of PE is its ability to be easily altered during processing to give a variety of forms that differ based on polymer chain length, density and crystallinity. PE is an easily processed thermoplastic, which can be made into a variety of shapes and forms, including tubing.
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PE is found nearly everywhere today, from plastic grocery bags, plastic wrap, drain pipes, milk cartons, to trash cans. Polyethylene (PE) is a common yet extremely useful and cost-effective plastic polymer. Hom Nath Dhakal, Sikiru Oluwarotimi Ismail, in Sustainable Composites for Lightweight Applications, 2021 1.2.1.5 Polyethylene 18.10), heat-healing strength and toughness frequently used for cling films, etc., whereas HDPE film provides excellent barrier properties for gas and water due to its higher crystallinity than LDPE film. Furthermore, LLDPE has crystal clear feature (refer Fig. In contrast, LLDPE plastic materials have remarkable mechanical properties than LDPE at same density. LDPE flexible films are extensively used for frozen foods, bakery products, fresh meat, and poultry as well as other products.
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Furthermore, this type of PE plastic is not suitable for easily oxidized food products due to low oxygen barrier properties, which is affected by external conditions and physical conditions, such as: humidity, polarity, volume, density, crystallinity, and temperature Furthermore, LDPE is more compatible for flexible films other than HDPE due to its flexible, soft, and stretchable characteristics. Generally, PEs has not only good processability but also shows a remarkable water vapor barrier functions, which is necessary for various water-sensitive food products, such as dried and liquid food stuffs. PEs densities are relatively low when compared to other conventional polymers the values range between 0.916 and 0.940 g/cm 3 for LLDPE and 0.840–0.970 g/cm 3 for HDPE. PE is a member of the polyolefins class, which also have various types of PE, depending on density of polymer type.