Novel polymeric alloy
Neoloy ...
{{Chembox | ImageFile = | ImageSize = | ImageAlt = | IUPACName = Neoloy | OtherNames = | Type = Nano-composite polymeric alloy | Main ingredient = Polyolefin | Section1 = ! colspan=2 style="background: #f8eaba; text-align: center;" |Identifiers
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| Section2 = ! colspan=2 style="background: #f8eaba; text-align: center;" |Properties
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| Density
| 0.96g/cm3
|-
| NEOLOY | |
|---|---|
| Young's modulus (E) | 2800–3100 MPa |
| Tensile strength(σt) | 55–75 MPa |
| Elastic limit | 50–150% |
| notch test | 3.6 kJ/m2 |
| Glass temperature | 75 °C |
| Vicat B | 170 °C |
| linear expansion coefficient (α) | 7×10−5/K |
| Water absorption (ASTM) | 0.16 |
| Source[1] | |
+== Neoloy ==
Neoloy is the registered trademark for a polymeric nanocomposite alloy based on polyester/polyamide thermoplastic nano-fibers in a polyolefin matrix. Developed by PRS in 2007, the creep resistant alloy is used commercially for high-strength geosynthetics, particularly in the manufacturer of polymeric strips used to form cellular confinement systems (geocells). Neoloy (often referred to in published research as Novel Polymeric Alloy – NPA) was developed to replace High-density Polyethylene (HDPE) in geosynthetics. Although HDPE is widely used due to its low cost, ease of manufacturing and flexibility, its high creep, low tensile strength and sensitivity to elevated temperatures limits its use in long-term, critical applications (Leshchinsky, 2009).
Neoloy is a polymeric alloy of polyolefin and engineering polymer. The polyolefin, mostly Polyethylene (PE) provides stress cracking resistance, hydrolytic resistance, very low temperature functionality and tear resistance, while the engineering polymer, nylon (PA) or polyester (PET) for example, provides strength, stiffness, retention of mechanical strength at elevated temperatures, creep resistance and long-term dimensional stability. The melt strength of the Neoloy is higher than PE, yet blow molding and extrusion are still possible.
Used in the manufacture of geosynthetics, such as a cellular confinement system, Neoloy based geocells have a higher tensile stiffness and strength, and are more durable over dynamic loading and under elevated temperatures than those made from HDPE (Han, 2011). This enables a long-term design strength that is suitable for long-term use in infrastructure, such as highways, railways, container yards and high retaining walls.
Production
Neoloy is manufactured for geosynthetic applications in a proprietary process, such as high-modulus geocells or geogrids, usually in multi-layer strips. Outer layers are comprised of blend of polyolefins while the core layer is formed from a high performance polymer. The blend is generally immiscible (an alloy), where the high performance polymer is dispersed in a matrix formed by the polyolefins. Since polymer blends are basically unstable, they undergo stabilization during melt processing, at a nano-level combined with compatibilized material. Neoloy can be produced in sheets, plates, grids, fibers and 3D articles.
The Neoloy core layer/s is made of a high performance polymer compound with a storage modulus of ≥1400 MPa at 23°C, measured by Dynamic Mechanical Analysis (DMA) at a frequency of 1 Hz according to ASTM D4065; or an ultimate tensile strength of at least 30 MPa. The outer layers are usually comprised of a polyolefin polymer, with a blend or alloy with other stabilizers, fillers, additives, fibers and elastomers. The high performance alloys of polyamides, polyesters, and polyurethanes are combined with polypropylene, copolymers, block copolymers, blends and/or other combinations.
Manufacture
Although most polypropylene homopolymers are too brittle and most polypropylene copolymers are too soft for load support applications, some grades of polypropylene polymers are stiff enough for some engineering strength, yet soft enough so that a geosynthetic can be handled for installation. These polymers are modified, via proprietary treatment processes and/or additives to attain the required physical properties. Unlike low crystalline polymers such as polypropylene, which require a post-extrusion processing such as orientation, cross-linking, and/or thermal annealing, higher crystalline polymers such as Neoloy can be extruded as strips and welded in section without post-extrusion treatment.
The sheet can be extruded into strips and welded, sewed, or bonded together to form geosynthetic products. The polymeric strip may further comprise additives to attain the required physical properties. Such additives may be selected from, among others, nucleating agents, fillers, fibers, nanoparticles, hindered amine light stabilizers (HALS), antioxidants, UV light absorbers, and carbon black. Fillers may be in the form of powders, fibers, or whiskers.
Nanoparticles are added to the polymeric composition for various purposes. For example, inorganic UV-absorbing solid nanoparticles have practically no mobility and are therefore very resistant against leaching and/or evaporation. UV-absorbing solid nanoparticles are also transparent in the visible spectrum and are distributed very evenly.
Properties
Neoloy polymeric alloy features excellent mechanical properties, thermal stability, good chemical resistance and excellent engineering properties. Neoloy has a coefficient of thermal expansion CTE less than about 80 ppm/°C; resistance to acidic media greater than polyamide 6 resin and/or resistance to basic media greater than PET resin; resistance to hydrocarbons greater than that of HDPE; creep modulus of > 400 MPa at 25°C at 20% of yield stress load for 60 minutes (ISO 899-1); and 1 percent secant flexural modulus > 700 MPa at 25°C (ASTM D790). Neoloy has a tensile strength in the range of 19.1 to 32 MPa with an elastic modulus of 440 to 820 MPa (at 2% strain).
Applications
Neoloy was developed for a high-modulus geosynthetics, including geocells, geogrids and geomembranes suitable for use in heavy load support applications, which require higher strength, stiffness and durability than commonly used HDPE geocells. In a geocell application, the high modulus of Neoloy means stiff and strong cell walls, which provide a very high elastic response to dynamic loading even after millions of cycles without permanent plastic deformation <Pokoharel - TBD>. A Neoloy geocell maintains its geometry and engineering characteristics for long-term, even under dynamic loading, thermal cycling and elevated temperatures, thereby enabling its use in applications in heavy duty civil infrastructure applications.
This is a new development in the geocell industry. Rather than conventional use which limits geocells to low volume roads or low-load applications (such as slope and channel protection), Neoloy-based geocells can be used in heavy-duty load support applications such as the reinforcement of upper base layers of paved roads and motorways, railways, intermodal ports and storage yards, working platforms, as well as very high retaining walls and embankments, where long-term durability under heavy loading is critical (Leshchinsky, et al, 2009). At the same time, the same Neoloy properties enable the manufacture of lighter geocells, suitable to less demanding applications, such as moderate slopes, retaining walls at less than 80% inclination, and channels with a water flow of less than 10m /s.
See Also
• Neoweb • Cellular Confinement Systems • HDPE • Testing standards for geocells?
References
1. Definition: Neoloy is a polymeric alloy of polyolefin and engineering polymer. The polyolefin, mostly Polyethylene (PE) provides stress cracking resistance, hydrolytic resistance, very low temperature functionality and tear resistance, while the engineering polymer, mostly aromatic polyester (PET for example), provides strength, stiffness, retention of mechanical strength at elevated temperatures, creep resistance and long-term dimensional stability. The melt strength of the Neoloy is higher than PE, yet blow molding and extrusion are still possible. 2. Composition: 30-95% Polyolefin, 70-5% engineering polymer 3. Properties: Density: 0.9-1.2 gr/cm^3, tensile strength: 12-60 MPa, Storage modulus: 100-5000 MPa, CTE: 70-150 ppm/C degree, brittleness temperature: minus 100 C, upper temperature limit: 50-80 C 4. Production: a proprietary process developed by (company name, link...). The process enables utilization of waste PET bottles after primary washing and drying, without need to pre-dry or pre-compound post industrial waste.TBD 5. Forms: pellets, sheets, plates, grids, fibers and 3D articles 6. Compatible manufacturing methods: injection molding, extrusion, blow molding, rotational molding, compression molding. 7. Applications: • Geocells (link to geocell, Neoweb...) • Geogrids (links...) • Geomembranes • Pipes • Molded 3D elements for automotives, pallets and consumer