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Low-density polyethylene

February 10, 2024

Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Dr John C. Swallow and M.W Perrin who were working for Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization.[1] Its manufacture employs the same method today. The EPA estimates 5.7% of LDPE (resin identification code 4) is recycled in the United States.[2] Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2013 the worldwide LDPE market reached a volume of about US$33 billion.[3]

LDPE has SPI resin ID code 4
Schematic of LDPE branching structure

Despite its designation with the recycling symbol, it cannot be as commonly recycled as No. 1 (polyethylene terephthalate) or 2 plastics (high-density polyethylene).[4][5]

Properties edit

LDPE is defined by a density range of 917–930 kg/m3.[6] At room temperature it is not reactive, except to strong oxidizers; some solvents cause it to swell. It can withstand temperatures of 65 °C (149 °F) continuously[6] and 90 °C (194 °F) for a short time. Made in translucent and opaque variations, it is quite flexible and tough.

LDPE has more branching (on about 2% of the carbon atoms) than HDPE, so its intermolecular forces (instantaneous-dipole induced-dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher. The side branches mean that its molecules are less tightly packed and less crystalline, and therefore its density is lower.

When exposed to consistent sunlight, the plastic produces significant amounts of two greenhouse gases: methane and ethylene. Because of its lower density (high branching), it breaks down more easily than other plastics; as this happens, the surface area increases. Production of these trace gases from virgin plastics increases with surface area and with time, so that LDPE emits greenhouse gases at a more unsustainable rate than other plastics. In a test at the end of 212 days' incubation, emissions recorded were 5.8 nmol g-1 d-1 of methane, 14.5 nmol g−1 d−1 of ethylene, 3.9 nmol g−1 d−1 of ethane, and 9.7 nmol g−1 d−1 of propylene. When incubated in air, LDPE emits methane and ethylene at rates about 2 times and about 76 times, respectively, more than in water.[7]

Chemical resistance edit

Applications edit

 
A GEECO bowl, c.1950, still used in 2014
 
A piece of packaging foam made from LDPE
 
A Ziploc bag made from LDPE
 
Facial wash gel bottle made of LDPE

Polyolefins (LDPE, HDPE, PP) are a major type of thermoplastic.[10] LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic parts for computer components, and various molded laboratory equipment. Its most common use is in plastic bags. Other products made from it include:

See also edit

References edit

  1. ^ Dennis Malpass (2010). Introduction to Industrial Polyethylene: Properties, Catalysts, and Processes. John Wiley and Sons. pp. 1–. ISBN 978-0-470-62598-9.
  2. ^ "Municipal Solid Waste Generation,n word and Disposal in the United States" (PDF). EPA.gov. 15 November 2016.
  3. ^ "Market Study: Polyethylene LDPE (2nd edition)". Ceresana.
  4. ^ Brady, Angela (28 December 2018). "How to Recycle Number 4 Plastic". San Francisco Chronicle.
  5. ^ "Exactly What Every Plastic Recycling Symbol Really Means". Good Housekeeping. 18 February 2022.
  6. ^ a b BPF. "Polyethylene (Low Density) LDPE, LLDPE". www.bpf.co.uk. Retrieved 2018-06-14.
  7. ^ Karl, David M.; Wilson, Samuel T.; Ferrón, Sara; Royer, Sarah-Jeanne (1 August 2018). "Production of methane and ethylene from plastic in the environment". PLOS ONE. 13 (8): e0200574. Bibcode:2018PLoSO..1300574R. doi:10.1371/journal.pone.0200574. ISSN 1932-6203. PMC 6070199. PMID 30067755.  This article incorporates text by Royer et al available under the CC BY 4.0 license.
  8. ^ Qiu, Xia-Wen; Pei, Jie; Wu, Chen-Chou; Song, Lin; Bao, Lian-Jun; Zeng, Eddy Y. (August 2021). "Determination of low-density polyethylene–water partition coefficients for novel halogenated flame retardants with the large volume model and co-solvent model". Chemosphere. 277: 130235. Bibcode:2021Chmsp.277m0235Q. doi:10.1016/j.chemosphere.2021.130235. PMID 33794435. S2CID 232764239.
  9. ^ "LDPE Chemical Compatibility Chart". CP Lab Safety.
  10. ^ a b Achilias, D.S.; Roupakias, C.; Megalokonomos, P.; Lappas, A.A.; Antonakou, Ε.V. (November 2007). "Chemical recycling of plastic wastes made from polyethylene (LDPE and HDPE) and polypropylene (PP)". Journal of Hazardous Materials. 149 (3): 536–542. doi:10.1016/j.jhazmat.2007.06.076. PMID 17681427.
  11. ^ LDPE products and applications. Exxon Mobil Corporation
  12. ^ . IDES – The Plastics Web

External links edit

  •   Media related to Low-density polyethylene at Wikimedia Commons
  • 2010_MSW_Tables_and_Figures_508.pdf. epa.gov

February 10, 2024
density, polyethylene, ldpe, thermoplastic, made, from, monomer, ethylene, first, grade, polyethylene, produced, 1933, john, swallow, perrin, were, working, imperial, chemical, industries, using, high, pressure, process, free, radical, polymerization, manufact. Low density polyethylene LDPE is a thermoplastic made from the monomer ethylene It was the first grade of polyethylene produced in 1933 by Dr John C Swallow and M W Perrin who were working for Imperial Chemical Industries ICI using a high pressure process via free radical polymerization 1 Its manufacture employs the same method today The EPA estimates 5 7 of LDPE resin identification code 4 is recycled in the United States 2 Despite competition from more modern polymers LDPE continues to be an important plastic grade In 2013 the worldwide LDPE market reached a volume of about US 33 billion 3 LDPE has SPI resin ID code 4Schematic of LDPE branching structureDespite its designation with the recycling symbol it cannot be as commonly recycled as No 1 polyethylene terephthalate or 2 plastics high density polyethylene 4 5 Contents 1 Properties 1 1 Chemical resistance 2 Applications 3 See also 4 References 5 External linksProperties editLDPE is defined by a density range of 917 930 kg m3 6 At room temperature it is not reactive except to strong oxidizers some solvents cause it to swell It can withstand temperatures of 65 C 149 F continuously 6 and 90 C 194 F for a short time Made in translucent and opaque variations it is quite flexible and tough LDPE has more branching on about 2 of the carbon atoms than HDPE so its intermolecular forces instantaneous dipole induced dipole attraction are weaker its tensile strength is lower and its resilience is higher The side branches mean that its molecules are less tightly packed and less crystalline and therefore its density is lower When exposed to consistent sunlight the plastic produces significant amounts of two greenhouse gases methane and ethylene Because of its lower density high branching it breaks down more easily than other plastics as this happens the surface area increases Production of these trace gases from virgin plastics increases with surface area and with time so that LDPE emits greenhouse gases at a more unsustainable rate than other plastics In a test at the end of 212 days incubation emissions recorded were 5 8 nmol g 1 d 1 of methane 14 5 nmol g 1 d 1 of ethylene 3 9 nmol g 1 d 1 of ethane and 9 7 nmol g 1 d 1 of propylene When incubated in air LDPE emits methane and ethylene at rates about 2 times and about 76 times respectively more than in water 7 Chemical resistance edit Excellent resistance no attack no chemical reaction to dilute and concentrated acids alcohols bases and esters Good resistance minor attack very low chemical reactivity to aldehydes ketones and vegetable oils Limited resistance moderate attack significant chemical reaction suitable for short term use only to aliphatic and aromatic hydrocarbons mineral oils and oxidizing agents Poor resistance and not recommended for use with halogenated hydrocarbons 8 9 Applications edit nbsp A GEECO bowl c 1950 still used in 2014 nbsp A piece of packaging foam made from LDPE nbsp A Ziploc bag made from LDPE nbsp Facial wash gel bottle made of LDPEPolyolefins LDPE HDPE PP are a major type of thermoplastic 10 LDPE is widely used for manufacturing various containers dispensing bottles wash bottles tubing plastic parts for computer components and various molded laboratory equipment Its most common use is in plastic bags Other products made from it include Trays and general purpose containers Corrosion resistant work surfaces Parts that need to be weldable and machinable Parts that require flexibility for which it serves very well Very soft and pliable parts such as snap on lids Six pack rings Juice and milk cartons are made of liquid packaging board a laminate of paperboard and LDPE as the waterproof inner and outer layer and often with of a layer of aluminum foil thus becoming aseptic packaging 11 12 Packaging for computer hardware such as hard disk drives screen cards and optical disc drives Playground slides Plastic wraps Plastic bags Plastic containers Pipes Housewares Battery cases Automotive parts Electrical components 10 See also editFilm blowing machine High density polyethylene HDPE Linear low density polyethylene LLDPE Medium density polyethylene MDPE Polyethylene terephthalate PET PETE Stretch wrap Ultra high molecular weight polyethylene UHMWPE References edit Dennis Malpass 2010 Introduction to Industrial Polyethylene Properties Catalysts and Processes John Wiley and Sons pp 1 ISBN 978 0 470 62598 9 Municipal Solid Waste Generation n word and Disposal in the United States PDF EPA gov 15 November 2016 Market Study Polyethylene LDPE 2nd edition Ceresana Brady Angela 28 December 2018 How to Recycle Number 4 Plastic San Francisco Chronicle Exactly What Every Plastic Recycling Symbol Really Means Good Housekeeping 18 February 2022 a b BPF Polyethylene Low Density LDPE LLDPE www bpf co uk Retrieved 2018 06 14 Karl David M Wilson Samuel T Ferron Sara Royer Sarah Jeanne 1 August 2018 Production of methane and ethylene from plastic in the environment PLOS ONE 13 8 e0200574 Bibcode 2018PLoSO 1300574R doi 10 1371 journal pone 0200574 ISSN 1932 6203 PMC 6070199 PMID 30067755 nbsp This article incorporates text by Royer et al available under the CC BY 4 0 license Qiu Xia Wen Pei Jie Wu Chen Chou Song Lin Bao Lian Jun Zeng Eddy Y August 2021 Determination of low density polyethylene water partition coefficients for novel halogenated flame retardants with the large volume model and co solvent model Chemosphere 277 130235 Bibcode 2021Chmsp 277m0235Q doi 10 1016 j chemosphere 2021 130235 PMID 33794435 S2CID 232764239 LDPE Chemical Compatibility Chart CP Lab Safety a b Achilias D S Roupakias C Megalokonomos P Lappas A A Antonakou E V November 2007 Chemical recycling of plastic wastes made from polyethylene LDPE and HDPE and polypropylene PP Journal of Hazardous Materials 149 3 536 542 doi 10 1016 j jhazmat 2007 06 076 PMID 17681427 LDPE products and applications Exxon Mobil Corporation DOW LDPE 5004I IDES The Plastics WebExternal links edit nbsp Media related to Low density polyethylene at Wikimedia Commons 2010 MSW Tables and Figures 508 pdf epa gov Retrieved from https en wikipedia org w index php title Low density polyethylene amp oldid 1204575913, wikipedia, wiki, book, books, library,

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