Pet structure. This is the short form for polyethylene terephthalate.
Pet structure. from publication: Molecular Weight Determination of Polyethylene Terephthalate | Polyethylene terephthalate (PET) is one of the most Download scientific diagram | Chemical structure of PET from publication: Improved permeate flux and rejection of ultrafiltration membranes prepared from polyethylene terephthalate (PET) bottle Jun 18, 2021 · We present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, $$ ( {\hbox {C}}_ {10} {\hbox {H}}_8 {\hbox {O}}_4)_n$$ , also called mylar Polyethylene terephthalate (PET) is a thermoplastic polymer that possesses a wide range of properties, making it highly sought after in various industries. The first polymer to be discussed will be polyethylene terephthalate (PET). Its transparency, lightweight nature, strength, chemical resistance, and thermal stability contribute to its versatility and widespread use. PET is spun into fibers for permanent-press fabrics, blow-molded into disposable beverage bottles, and extruded into photographic film and magnetic recording tape. It is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. IsPETase, from the PET-assimilating bacterium Ideonella sakaiensis, is a Polyethylene terephthalate (PET) exemplifies how the ratio of amorphous and crystalline phases within a sample can be affected by different cooling rates. The ‘G’ in PETG stands for “glycol,” which is added during the polymerization process. In contrast, the PET-MWCNT composites revealed a nanohybrid shish-kebab (NHSK) morphology, with reduced orientation and crystallinity. Feb 14, 2024 · Polyethylene Terephthalate (PET) – a versatile polymer shaping industries. PET is a polymer – a macromolecule made out of thousands of repeating monomer units. Dec 13, 2017 · Poly-ethylene terephthalate (PET) is a widely used plastic which accumulates in the environment with detrimental consequences. Jan 1, 2014 · PET (poly (ethylene terephthalate)) is one of the synthetic semi-aromatic polyesters and has terephthalic acid and ethylene glycol units in main chain. 3–0. Discover its use in plastic bottles, food containers, and clothing. Préforme PET avec bouchon Le poly (téréphtalate d'éthylène) 6, plus connu sous le nom anglais de polyethylene terephthalate (parfois francisé de manière impropre en « polyéthylène téréphtalate ») ou PET, que l'on trouve également avec l'abréviation PETE, est un polymère de type polyester saturé thermoplastique, par opposition aux Nov 11, 2021 · PDF | In this study, a detailed research has been done on polyethylene terephthalate (PET) related production and technologies, properties and usage | Find, read and cite all the research you May 20, 2021 · Poly (ethylene terephthalate) (PET) is the most abundant polyester plastic and a major contributor to plastic pollution. Unravel PET's mysteries in this blog, exploring its history, uses, manufacturing, structure, recycling, and material properties. PET monomers join to form linear polymers that terminate in carboxyl groups, whose protonation state change according to the pH conditions of the environment. Poly (ethylene terephthalate) What is a polyester? Download scientific diagram | Molecular structure of PET. 5. PBT (Polybutylene Terephthalate): PBT is made by polymerizing butanediol with terephthalic acid or dimethyl Polyethylene terephthalate (aka PET, PETE or the obsolete PETP or PET-P) is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. The chemical industry makes it. from publication: EVALUATION OF THE AIR AGING MEDIA OF POLY (ETHYLENE TEREPHTHALATE) IN OXYGEN PLASMA | Fabric samples 100% polyester Jun 1, 2024 · PET, or polyethylene terephthalate, is a common plastic used in the manufacturing of products such as water bottles, food packaging, and textiles. Explore its key benefits, limitations, properties, toxicity, processing guidelines and applications. Download scientific diagram | The molecular structure of PETG from publication: Fine dispersion morphology of polystyrene/poly (ethylene terephthalate glycol) blending generation for controlled Uncover the essential properties of PET plastic, its various types, and how it’s used in packaging, textiles, and more. In this article, we will delve into the intricacies May 15, 2025 · Polyethylene Terephthalate (PET) Explained Polyethylene Terephthalate (PET) is a widely used plastic known for being strong, lightweight, and moisture-resistant. Polyethylene terephthalate (PET) is a widely used thermoplastic polyester known for its lightweight, toughness, and excellent recyclability, playing an irreplaceable role in modern industry. AI generated Nov 30, 2020 · Abstract Linear 1,10-decanediamine was chosen as a modified monomer to prepare modified poly (ethylene terephthalate) (PET) with a low content of amide bonds through two different synthetic methods. It is also popular for packaging salad dressings, peanut butter, cooking oils, mouthwash, shampoo, liquid hand 1. 92 Å resolution X-ray crystal structure of PETase, which reveals features common to both cutinases and lipases. As a result, it may guide the development of more efficient and economic IL catalysts for use in the PET recycling industry. Chemical structure of polyethylene terephthalate The manufacturing process begins with a film of molten polyethylene terephthalate (PET) being extruded onto a chill roll, which quenches it into the amorphous state. So, what is PET plastic? In the following content, we will explore the chemical properties From the crystal structure, the monomer of PET would seem to possess a center of symmetry as seen from Figure 1 showing the projection of the molecules along c-axis and normal to (010) plane. PET for your product, you should know the characteristics of these two plastics, including their chemical structure, appearance, temperature resistance, cost, and environmental Code d'identification de la résine PET. Samples were prepared by dropping the matrix, which consisted of a solution of 2,4,6-trihydroxy acetophenone at a concentration of 10 mg/ml (in ethanol/water v/v 1/1), on to the slide. Discover how PET's structure affects its properties, such as melting point, strength, density, transparency, and gas barrier. Nov 8, 2024 · The environmental and economic challenges posed by the widespread use and disposal of plastics, particularly poly (ethylene terephthalate) (PET), require innovative solutions to mitigate their impac Ethylene terephthalate | C18H14O8 | CID 19046907 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological Jan 26, 2018 · Poly(ethylene terephthalate) (PET) is a widely used plastic and its accumulation in the environment has become global problem. Polyethylene terephthalate (or poly (ethylene terephthalate), [5] PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins. Chemical Structure and Composition PBT and PET belong to the same polyester family and have a similar backbone structure, but they differ slightly in the alkyl chain lengths of their molecular composition. PET chemical structure. PTT (poly (trimethylene terephthalate)) is also a synthetic aromatic polyester with terephthalic acid and propylene glycol units. This comprehensive guide covers PET’s chemical structure, production processes, environmental impacts, and recycling methods to grasp what it entails fully. S. After removing the solvent, the oligo (ethylene terephthalate)s solution was dropped on to the matrix. However, the end property, melting behavior, and processing technology for PET depend on the chemistry of the reactant, catalyst, and other additives used here. It is a semicrystalline polymer, and most of the industrial success of PET derives from its easily tunable crystallization kinetics, which allow users to produce the polymer with a high crystal fraction for applications that Oct 12, 2017 · Central to its PET biodegradation capability is a secreted PETase (PET-digesting enzyme). The pET Expression Systems provide the plasmids and host strains. The effects of TDP, ODP and HQ on melt post-polycondensation process and crystallization kinetics, melting behaviors, crystallinity and Oct 31, 2023 · What is PET Plastic? Polyethylene terephthalate, better known as PET Plastic (also sometimes as PETE ), is the most used thermoplastics globally in various textiles, films, electronics, packaging, automobiles, etc. Thermal observations of RPET samples suggest that crystalline characteristics and melt crystallized structures of RPET are different from that of neat PET. Join us in uncovering the facets of this remarkable material that's integral to our daily lives. Polyethylene terephthalate (PET) Polyethylene terephthalate (PET) is one of the most important and widely used engineering thermoplastic materials and polymers. This chapter not only provides insight of chemistry of the polymer but also describes the structure–property relationship for the Download scientific diagram | Chemical structures of PET, PBT, and PTT. It is widely used in synthetic fibers, films, and food packaging. As a result, it has excellent film-forming and molding properties. POLYESTERS This page looks at the formation, structure and uses of a common polyester sometimes known as Terylene if it is used as a fibre, or PET if it used in, for example, plastic drinks bottles. Oct 17, 2022 · Learn about PET, a condensation copolymer of ethylene glycol and terephthalic acid, used in fibers, bottles, and other applications. 85,86 PET is an aromatic and semi-crystalline polymer with many attractive characteristics such as high strength and toughness, high glass transition temperature, superior mechanical properties, chemical resistance and excellent Jul 16, 2024 · PET (Polyethylene Terephthalate) is one of the most flexible and largely used plastics daily. Jun 1, 2016 · Uniaxially deformed PET-MWCNT films displayed improved mechanical properties compared with unfilled PET films. The biorecycling of PET waste requires the complete depolymerization of PET to terephthalate and ethylene glycol. Also shown are the terminal PET monomers with (c) protonated and (d) deprotonated May 29, 2023 · Learn about PET plastic (Polyethylene Terephthalate), its composition, production process, and everyday applications. Polyethylene terephthalate (PET) is defined as a thermoplastic polyester produced by condensation polymerization of mono-ethylene glycol and terephthalic acid or dimethyl terephthalate. PET is a versatile material with the ability to be remade from its polymer sta All of the pET vectors and companion products are available as kits designed for convenient cloning, expression, detection, and purification of target proteins. Dec 2, 2023 · Learn about the chemical composition, molecular unit, and crystalline structure of PET, a widely used thermoplastic material. PET is synthesized by polyesterification of ethylene glycol and terephthalic acid. Looking for a complete range of polyethylene terephthalate grades, resume your PET resin selection here. Polyethylene terephthalate (aka PET, PETE or the obsolete PETP or PET-P) is a thermoplastic polymer resin of the polyester family. The biggest utilizer of PET is the textile industry, in which thermoplastic is mainly known by the name Polyester. During production, the material undergoes very fast cooling, resulting in a high amorphous Jun 1, 2024 · The research showed that this structure could degrade PET without using costly catalysts containing precious metals. Enzymatic PET hydrolysis is the most ecofriendly recycling technology. Learn about the chemical structure, properties, and applications of polyethylene terephthalate (PET), a thermoplastic polymer resin of the polyester family. are made from PET. It belongs to the class of polymers known as the thermoplastic polymer resin of the polyester family and has many applications in fibers, containers and injection molding as well as biaxial oriented films. Oct 1, 2020 · Polyethylene terephthalate (PET) is the third most widely diffused polymer exploited in the packaging industry, monopolizing the bottles market for be… PET is a clear, strong, and lightweight plastic that is widely used for packaging foods and beverages, especially convenience-sized soft drinks, juices and water. Here the authors report crystal structures of a PET-hydrolyzing Download scientific diagram | 6 Chemical structure of PET. As shown in the chemical equation, PET is made industrially by the reaction of equimolar amounts of terephthalic acid and ethylene glycol at 220–260 °C and 0. 85,86 PET is an aromatic and semi-crystalline polymer with many attractive characteristics such as high strength and toughness, high glass transition temperature, superior mechanical properties, chemical resistance and excellent Discover Polyethylene Terephthalate (PET): properties, structure, uses, safety, and recycling. from publication: New enzymes with potential for PET surface modification | This work describes newly Polyethylene terephthalate, commonly known as PET, is the most important polyester. PET can be processed using a Dec 15, 2018 · The crystal structure of polyethylene terephthalate (Terylene) has been determined by the interpretation of the X-ray diffraction patterns given by drawn fibres. This combination of factors makes PET an ideal material for applications that require clear, visually appealing packaging. Download scientific diagram | Molecular Structure of Polyethylene Terephthalate PET Chemical Formula: (C10H8O4)n from publication: An Experimental Study on Plastic Paver Tiles | Plastic is one of Jan 1, 2019 · Polyethylene terephthalate (PET) is popular for its widespread use from thermoplastic product to fiber. Aug 5, 2020 · Abstract This review presents an overview of the state of the art in understanding of the chemistries behind polyethylene terephthalate (PET) degradation under hydrolytic and photolytic conditions, which are the main degradation processes that operate in the natural environment. Polyethylene terephthalate (aka PET, PETE or the obsolete PETP or PET-P) is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. Jul 8, 2025 · Find key facts about Polyethylene Terephthalate (PET Polymer). Jun 23, 2025 · Discover the pet chemical structure, its applications, and sustainability in various industries. Oct 17, 2022 · Poly (ethylene terephthalate), known familiarly as PET, is a condensation copolymer of ethylene glycol 1 and terephthalic acid 2. From beverage bottles to textile fibers, PET plastic is everywhere, profoundly impacting our daily lives. PET is produced from the polycondensation of ethylene glycol and terephthalic acid. Abstract Polyethylene terephthalate (PET) is one of the most widely used polyesters today – it is used in packaging, fabric, engineering, electronics, and biomedical industries. Oct 8, 2024 · What is Polyethylene Terephthalate (PET)? PET plastic is an abbreviation for Polyethylene terephthalate, commonly referred to as PET or PETP. This small difference leads to significant changes in their properties. Jul 10, 2024 · Poly(ethylene terephthalate) (PET) is a thermoplastic polyester with excellent thermal and mechanical properties, widely used in a variety of industrial fields. Polyethylene Terephthalate (PET) is Versatile plastic widely used in various industries and is popular choice for packaging, textiles, and other applications Jan 1, 2012 · The effect of two difunctional chain extenders, 1,6-diisocyanatohexane (NCO) and 1,4-butanediol diglycidyl ether (EPOX), in the reactive melt-processing of a post-consumer poly (ethylene terephthalate) (r-PET) was investigated. Shown are the chemical structure of a PET monomer in (a) trans and (b) cis isomeric forms. Clear explanations for Chemistry students with real-life examples. SAXS/WAXS data revealed a well oriented lamellar structure for unfilled PET films. Dec 25, 2023 · Poly (ethylene terephthalate) (PET) is a semi-crystalline type of polyester plastic, which is mainly used for textile fibers, but also renowned as the most widely used type of plastic used for plastic bottles, notably single-use bottles for soft drinks and water [3], [5]. It is often incorrectly expressed as polyethylene terephthalate, without the parentheses. The density of PET ranges from 1. 33 g/cm 3 for the amorphous region to about 1. Jul 5, 2011 · Polyethylene terephthalate (PET) is a linear polymer widely used in beverage bottles and other plastic containers. The chemical structure of a PET monomer is presented in Figure 1. It is a copolymer that is made by modifying the basic Polyethylene Terephthalate (PET) structure. The most common way of doing this is the sequential process, in which the film is first drawn in the machine direction using heated rollers Jun 27, 2024 · The high transparency of PET is a result of its unique chemical structure, controlled crystallinity, the use of additives, and advanced processing techniques. To produce PET, chemists use two different kinds of monomers: terephthalic acid and ethylene glycol. The history of enzymatic PET depolymerization has revealed two critical issues for the industrial depolymerization of PET Download scientific diagram | 1 Chemical structure of PET. Molecular weight is the most important characteristic for determining the mechanical properties and ability to fabricate these Polyethylene terephthalate also known as poly (ethylene terephthalate), usually reduced as PETE, PET, or the outmoded PET-P or PETP, is the great collective thermoplastic resin covering polymers of the nylon/polyester-based family. Understanding PET’s journey, from its raw materials to the end products we encounter daily, provides insights into the world of plastics and their impact on modern society. PET has the characteristic of being a transparent, amorphous thermoplastic when it is subjected to rapid cooling, while it behaves as a semicrystalline plastic when cooled slowly or when cold-drawn. PETase retains the ancestral α/β-hydrolase fold but exhibits a more open active-site cleft than homologous cutinases. Apr 29, 2025 · Polyethylene Terephthalate (CAS 25038-59-9) information, including chemical properties, structure, melting point, boiling point, density, formula, molecular weight Jul 4, 2025 · Polyethylene terephthalate, or PET, a strong, stiff synthetic fiber and resin and a member of the polyester family of polymers. 6 MPa Explore the versatile world of Polyethylene Terephthalate (PET), its properties, applications, environmental impact, and future prospects. PET has a highly symmetrical molecular structure, which gives it good crystal orientation capabilities. ProleanTech uses advanced injection molding techniques to turn PET into high-quality parts and products. Its chemical structure is shown in Fig. It has a fantastic set of properties, like chemical, mechanical Jun 9, 2022 · Comprehensive guide on polyethylene terephthalate (PET), covering its properties, production process, grades, benefits, drawbacks, and health implications. Virtually all single-serving and 2-liter bottles of carbonated soft drinks and water sold in the U. Our Nov 5, 2021 · Publications on polyethylene terephthalate (PET) continue to increase including the number of publications on recycling. Jul 28, 2025 · How to write an article? | B1 Preliminary (PET) - Structure - Writing Guide - Example Answers - Exam Questions - Writing Checklist - Things to Focus On - Useful Phrases & Expressions - Requirements Chemical Entities of Biological Interest (ChEBI) is a freely available dictionary of molecular entities focused on 'small' chemical compounds. The torque evolution during processing in a batch mixer and the molecular weight of the chain-extended r-PET, as determined by SEC analysis, were comparatively . Polyethylene terephthalate glycol, known as PETG or PET-G, is a thermoplastic polyester that delivers significant chemical resistance, durability, and formability for manufacturing. The molecular chain structure of PBT is similar to that of PET, and… Jan 1, 2011 · PDF | Polyethylene terephthalate, commonly coded as PET, PETE, is a thermoplastic polymer resin of the polyesters and is used in liquid containers, | Find, read and cite all the research you Nov 21, 2012 · Biaxially stretched poly (ethylene terephthalate) (PET) films are currently the most widely used polymeric substrate material in the fields of display technologies, electronic devices, storage Jan 1, 2020 · The structure and morphology of PET are successfully modified via precipitation method forming RPET. Jul 4, 2025 · Polyethylene terephthalate, or PET, a strong, stiff synthetic fiber and resin and a member of the polyester family of polymers. Mar 5, 2025 · While polyethylene (PE) and polyethylene terephthalate (PET) might sound similar, the two materials are completely separate polymers with distinct properties and applications. Abstract Three kinds of modified poly (ethylene terephthalate) (PET) were prepared by solution blending combined with melt post-polycondensation, using 4,4′-thiodiphenol (TDP), 4,4′-oxydiphenol (ODP) and hydroquinone (HQ) as the bisphenols, respectively. This is the short form for polyethylene terephthalate. Here the authors report the crystal structure of a Ideonella May 31, 2025 · Imagine a world without the ubiquitous plastic bottle—no convenient way to hydrate on the go, no durable containers for your favorite beverages. Apr 15, 2025 · Explore the structure, benefits, and recycling process of polyethylene terephthalate, one of the world’s most used plastics. That’s why lazy chemists usually call it PET. from publication: IMPACT MODIFIED POLY (ETHYLENE TEREPHTHALATE)-ORGANOCLAY NANOCOMPOSITES | This study was conducted to investigate the Sep 29, 2012 · To properly understand the differences in performance between PET and PBT we need to compare apples to apples — the semi-crystalline forms of each polymer. PET finds applications in packaging, textiles, electrical and electronics, automotive, medical and Mar 25, 2024 · Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are two types of aromatic polyester plastics. Yes, it’s a bit of a mouthful. It is then biaxially oriented by drawing. Here, we present a 0. 5 g/cm 3 for the crystal regions. It is commonly used for packaging beverages and food due to its high-temperature resistance and is characterized by the presence of low molecular weight oligomers, including acetaldehyde. Learn about Polyethylene Terephthalate in this article, its definition, Structure, Chemical Formula, Chemical and Physical Properties, Uses, Effects, FAQs Polyethylene terephthalate (sometimes written poly (ethylene terephthalate)), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resins. It contains information The repeat structure of polyethylene terephthalate. 1. Apr 29, 2025 · Polyethylene Terephthalate (PET) is a thermoplastic polyester with a semi-crystalline structure. PET Molecular Stucture Part 1: Basic Knowledge of PET PET Bottle Flakes PET Foam Beads The molecular structure of PET plastic is highly symmetrical and […] Jan 13, 2017 · Well, that means the bottle is made from the compound polyethylene terephthalate. The bulk density is somewhere in between. Different methods for PET molecular weight determination are reviewed in this chapter. Polar ester groups in poly (ethylene terephthalate) hold the polyester into strong crystals Phenyl rings in poly (ethylene terephthalate) are stacked to form strong, ordered crystals. Discover insights that drive innovation and sustainability in your projects! Nov 8, 2024 · The environmental and economic challenges posed by the widespread use and disposal of plastics, particularly poly (ethylene terephthalate) (PET), require innovative solutions to mitigate their impact. Find out its chemical structure, properties, production, and hazards. from publication: Discrimination of Thermoplastic Polyesters by MALDI-TOF MS and Py-GC/MS | The aim of this work is to Sep 30, 2023 · The chemical structure of PET is more complex than PE, with oxygen atoms in addition to carbon and hydrogen atoms in the backbone. The unit cell, which contains one c PET has a highly symmetrical molecular structure, a good crystal orientation ability and an excellent optical propertity. Jul 1, 2025 · 3D-Printed recycled polyethylene terephthalate (PET) sandwich structures – Influence of infill design and density on tensile, dynamic mechanical, and creep response Polyethylene terephthalate (PET) Polyethylene terephthalate (PET) is one of the most important and widely used engineering thermoplastic materials and polymers. Laboratory studies, carried out under so-called accelerated weathering conditions, have been reviewed and are Jul 2, 2024 · Abstract Polyethylene terephthalate (PET) is a major component of plastic waste. It forms a relatively rigid structure with a Tg of approximately 70°C, a melting point of ~250°C, and crystallizes in a triclinic structure. With its lightweight, durable, and versatile properties, PET has become an essential material in modern-day society [11]. What makes PET polymerspolyemrs special is theirits ability to be recycled and theirits versatility in various industries. It mainly includes polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The solvent was evaporated again. In this technical deep dive, we’ll unravel the complexities of PET, a material whose importance spans Feb 23, 2021 · Polyethylene Terephthalate (PET) is also abbreviated as PETE. It may also be PET chemical structureDid you have an account with the NIH 3D Print Exchange? Polyethylene terephthalate (or poly (ethylene terephthalate), [5] PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins. Find out how PET is used in packaging, textiles, automotive, medical, and construction industries, and its environmental impact and recycling. It is a semicrystalline polymer, and most of the industrial success of PET derives from its easily tunable crystallization kinetics, which allow users to produce the polymer with a high crystal fraction for applications that demand Download scientific diagram | Molecular structure of poly (ethylene terephthalate) PET. This reality is hard to fathom, thanks to polyethylene terephthalate (PET), a remarkable polymer that revolutionized packaging and textiles. However, the increasing use of PET has also led to a global crisis in waste management, as the improper disposal of PET Download scientific diagram | Chemical structure of PETE from publication: Thermal Degradation of Poly (ethylene terephthalate) Waste Soft Drinks Bottles and Low Density Polyethylene Grocery Bags Sep 30, 2023 · Polyethylene Terephthalate (PET) is a ubiquitous and versatile polymer that touches our lives in numerous ways, from the bottles we drink to the fibers in our clothing. See its chemical properties, production, and hazard codes. If you have to choose between using PE vs. To evaluate the effect of amide bonds on the properties of poly (ester amide) analogs (PETAs), the performance of this new type of PET was compared with 1,10-decanediol-modified PET as a control Unlock the potential of PET: Polyethylene terephthalate with our comprehensive analysis and testing. Abstract Poly (ethylene terephthalate) (PET) is a thermoplastic polyester with excellent thermal and mechanical properties, widely used in a variety of industrial fields. It is a modern consumer goods component that includes water bottles, food containers, synthetic fibers, and packaging. jcqstwhouafeymxvqrwnymrnmexbcknpvfsqepdszhfuxywfa