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Wood Fiber Reinforced Thermoplastic and Thermosets Composites
Published in Omar Faruk , Jimi Tjong , Mohini Sain, Lightweight and Sustainable Materials for Automotive Applications, 2017
Regarding biological degradation, the two major components of wood fiber-based thermoplastic composites, polyolefins and lignocellulosic fibers or particles, display different behavior. Polyolefins are highly resistant to biodegradation, especially without prior abiotic oxidation because their backbone is solely built of carbon atoms. Other formulation components such as plasticizers, lubricants, stabilizers, and colorants may cause fungal colonization and decay on plastic materials. Nondurable wood is also prone to fungal decay, however, if the wood particles are well encapsulated by the thermoplastic matrix (i.e., at filler levels ≤ 50% by wt.) and if moisture uptake can be minimized, fungal decay should not be an issue (Clemons and Ibach 2004, Schirp and Wolcott 2005, Schirp et al. 2008). It is important to remember that the availability of moisture is a prerequisite for biological decay. Once water has entered into the material, it will leave only very slowly since the plastic in WPC provides a barrier to gas evaporation. One way to reduce moisture uptake of the composites is to use thermally treated wood particles. In Figure 3.13, WPC based on thermally treated beech wood flour is shown. Particle size reduction occurred during processing (Figure 3.14).
Exterior Enclosure Components
Published in Kathleen Hess-Kosa, Building Materials, 2017
A “polyolefin,” also referred to as a polyalkene, is a class of organic thermoplastic polymers that includes, but is not limited to, polyethylene and polypropylene. In the manufacturing process, plasticizers and polymer additives (including fire retardants) are mixed with the alkene monomers prior to polymerization. The end product is less temperature sensitive than PVC, and there is no halogen (e.g., chlorine) content—unless a halogenated fire retardant (e.g., brominated compounds) was added to the formulation. TPO product emissions are not as much a concern as that of PVC membranes. TPO polymers have a considerably higher melting point than PVC products. The melting point for polypropylene is of 226–338°F (139–170°C), and the melting point for polyethylene is of 248–356°F (120–180°C). These temperatures are not likely to be met or exceeded on even the darker colored roofs.As with PVC products, plasticizers are not matrix bound and when released into the ambient air may cause eye and respiratory tract irritation—especially with the elevated temperatures generally encountered on roof tops. Plasticizer emissions are less likely, but still possible, from TPO roof membranes.As with PVC products, polymer additives, not matrix bound, when released into the ambient air may pose a toxic and/or irritant hazard. Elevated temperatures may be contributory to chemical emissions from additives. Furthermore, in some cases, water runoff of some water-soluble, toxic additives can pose an environmental hazard.
Insertion or Ziegler–Natta Polymerization of Olefins
Published in Samir H. Chikkali, Metal-Catalyzed Polymerization, 2017
Samir H. Chikkali, Ketan Patel, Sandeep Netalkar
Applications of various polyolefins have been summarized under each section. The purpose of the section is to give a broader overview of the polyolefin industry and differentiate various classes of polyolefins based on the market and size of the market (Figure 2.64). Polyolefin-including PE, PP, poly(1-butene), poly(4-methyl-1-pentene), ethylene–propylene elastomer (EPR), and EPDM are the most widely used commercial polymers, with over 180 million metric tons global annual consumption, or close to 60% of the total polymer produced in year 2014.* The major types of polyolefins include PP, HDPE, LLDPE, LDPE, metallocene polyethylene (mPE), and various copolymers and elastomers. The polyolefin family of products serves a wide variety of end-use markets in the major sectors of packaging, automotive, construction, medical, wire and cable, and others. By nature, an industry of this size is considered a commodity producer. However, almost all of the major polyolefin producers consider polyolefins as a specialty product with plenty of opportunities for value addition and creation through technological innovations. Unlike the incremental technological developments more common in other polymers, polyolefin technology developments are significant and routinely leapfrog the existing ones. These tremendous developments in technology impact the whole industry as a unit as well as the high profit sectors, often causing confusion regarding expected impact on profitability and classification of specialty versus commodity. As a case in point, metallocenes introduced in the early 1990s were initially positioned in the market as specialties with high expectations for profitability, but are settling down as differentiated commodities. The family of polyolefins can be classified into the following three classes based on the market size they serve: (a) commodities, (b) differentiated commodities, and (c) specialties based on the specialty index which is a combination of various parameters such as profitability, demand, number of players, price, and technical barriers as the criteria.
Thermally enhanced polyolefin composites: fundamentals, progress, challenges, and prospects
Published in Science and Technology of Advanced Materials, 2020
A.U. Chaudhry, Abdel Nasser Mabrouk, Ahmed Abdala
The current interest in thermally enhanced polyolefin to meet the requirements of many emerging applications focuses on an excellent combination of thermal and mechanical properties. Several reviews discuss the progress in improving κ of polymers via controlling/altering the polymer morphology [22] and fabrication of composites and nanocomposites with conductive fillers [10–12,26,27]. However, to the best of our knowledge, no review focuses on enhancing κ of polyolefin via the fabrication of composites with conductive fillers and nanofiller. This comprehensive review is dedicated to the progress in improving κc of polyolefin composites. Polyolefin are a unique class of polymers, not only because of their vast production scale and low cost but also because they are the most challenging polymer for the fabrication of composites and nanocomposites due to their nonpolar nature that leads to poor dispersion of the filler and weak interface between the polymer and the filler. This weak interface promotes phonon scattering that limits the enhancement in κc. A review dedicated to this class of polymers provides an in-depth analysis of the key aspects that govern the enhancement of κ in terms of processing, filler type, and loading. Moreover, other essential elements such as heat transfer mechanism in polymer composites, modeling, and simulation of thermal conductivity in polymers and polymer composites, and thermal conductivity measurement techniques are also discussed. Therefore, this comprehensive review will contribute to accelerating the development of commercially viable thermally conductive polyolefins.
State of art review on the incorporation of fibres in asphalt pavements
Published in Road Materials and Pavement Design, 2023
Shenghua Wu, Ara Haji, Ian Adkins
Polyolefin is formed by the polymerisation of olefin monomer units. The most common polyolefin include polypropylene (PP) and polyethylene (PE). These polymers are prevalent in a wide array of applications depending on the material characteristics of the polymer, most notably consumer plastic. It is generally agreed that the addition of those fibre materials either virgin or recycled can improve strength, rutting and fatigue resistance of asphalt mixtures, as well as moisture resistance (Al-Hadidy & Tan, 2009; García-Travé et al., 2016; Morova et al., 2016; Othman, 2010; Punith & Veeraragavan, 2011; Qi et al., 1995; Sol-Sánchez et al., 2015; Sun et al., 2020; Yoo et al., 2011; Ziari and Moniri 2019).
Effect of synthetic fibres on fracture performance of asphalt mortar
Published in Road Materials and Pavement Design, 2020
Panos Apostolidis, Xueyan Liu, Gerald C. Daniel, Sandra Erkens, Tom Scarpas
Polyolefins consist of long and asymmetric chains (CH2 = CHx, x representing the alkyl group) composed of more than 85% by mass of ethane, propane or olefin units (Mather, 2009). There are two main synthetic components of polyolefins; polypropylene (PP) and polyethylene (PE). Generally speaking, polyolefin has excellent mechanical properties, such as high tensile strength and abrasion resistance, low specific gravity, non-water absorbent, and the ability to be thermally bonded. The PP yarns, which are the most dominant chemical component in polyolefin fibres, have excellent resistance to mineral acids and alkali as well as high shear strength, bulk elasticity and dimensional stability.