Latex

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Tapping of latex from a tree, for use in rubber production Latex-production.jpg
Tapping of latex from a tree, for use in rubber production

Latex is an emulsion (stable dispersion) of polymer microparticles in water. [1] Latices are found in nature, but synthetic latices are common as well.

Contents

In nature, latex is found as a milky fluid, which is present in 10% of all flowering plants (angiosperms). [2] It is a complex emulsion that coagulates on exposure to air, consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or scarlet latex. Since the 17th century, latex has been used as a term for the fluid substance in plants, deriving from the Latin word for "liquid". [3] [4] [5] It serves mainly as defense against herbivorous insects. [2] Latex is not to be confused with plant sap; it is a distinct substance, separately produced, and with different functions.

The word latex is also used to refer to natural latex rubber, particularly non-vulcanized rubber. Such is the case in products like latex gloves, latex condoms, latex clothing, and balloons.

IUPAC definition for latex IUPAC definition for latex.png
IUPAC definition for latex

Biology

Articulated laticifers

The cells (laticifers) in which latex is found make up the laticiferous system, which can form in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the meristem of the stem or root. The cell walls between these cells are dissolved so that continuous tubes, called latex vessels, are formed. Since these vessels are made of many cells, they are known as articulated laticifers. This method of formation is found in the poppy family and in the rubber trees (Para rubber tree, members of the family Euphorbiaceae, members of the mulberry and fig family, such as the Panama rubber tree Castilla elastica ), and members of the family Asteraceae. For instance, Parthenium argentatum the guayule plant, is in the tribe Heliantheae; other latex-bearing Asteraceae with articulated laticifers include members of the Cichorieae, a clade whose members produce latex, some of them in commercially interesting amounts. This includes Taraxacum kok-saghyz , a species cultivated for latex production. [6]

Non-articulated laticifers

In the milkweed and spurge families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling, latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In many euphorbs, the entire structure is made from a single cell – this type of system is known as a non-articulated laticifer, to distinguish it from the multi-cellular structures discussed above. In the mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the embryo.

The laticiferous system is present in all parts of the mature plant, including roots, stems, leaves, and sometimes the fruits. It is particularly noticeable in the cortical tissues. Latex is usually exuded as a white liquid, but is some cases it can be clear, yellow or red, as in Cannabaceae. [2]

Productive species

Latex is produced by 20,000 flowering plant species from over 40 families. These include both dicots and monocots. Latex has been found in 14 percent of tropical plant species, as well as six percent of temperate plant species. [7] Several members of the fungal kingdom also produce latex upon injury, such as Lactarius deliciosus and other milk-caps. This suggests it is the product of convergent evolution and has been selected for on many separate occasions. [2]

Defense function

Rubber tapping latex Latex being collected from a tapped rubber tree.jpg
Rubber tapping latex

Latex functions to protect the plant from herbivores. The idea was first proposed in 1887 by Joseph F. James, who noted that latex of milkweed

carries with it at the same time such disagreeable properties that it becomes a better protection to the plant from enemies than all the thorns, prickles, or hairs that could be provided. In this plant, so copious and so distasteful has the sap become that it serves a most important purpose in its economy. [8]

Evidence showing this defense function include the finding that slugs will eat leaves drained of their latex but not intact ones, that many insects sever the veins carrying latex before they feed, and that the latex of Asclepias humistrata (sandhill milkweed) kills by trapping 30% of newly hatched monarch butterfly caterpillars. [2]

Other evidence is that latex contains 50–1000× higher concentrations of defense substances than other plant tissues. These toxins include ones that are also toxic to the plant and consist of a diverse range of chemicals that are either poisonous or "antinutritive."

Latex is actively moved to the area of injury; in the case of Cryptostegia grandiflora , latex more than 70 cm from the site of injury is mobilized. [2] The large hydrostatic pressure in this vine enables an extremely high flow rate of latex. In a 1935 report the botanist Catherine M. Bangham observed that "piercing the fruit stalk of Cryptostegia grandiflora produced a jet of latex over a meter long, and maintained [this jet] for several seconds." [9]

The clotting property of latex is functional in this defense since it limits wastage and its stickiness traps insects and their mouthparts. [2]

While there exist other explanations for the existence of latex including storage and movement of plant nutrients, waste, and maintenance of water balance that "[e]ssentially none of these functions remain credible and none have any empirical support". [2]

Applications

Opium poppy exuding fresh latex from a cut Opium pod cut to demonstrate fluid extraction1.jpg
Opium poppy exuding fresh latex from a cut

The latex of many species can be processed to produce many materials.

Personal and healthcare products

Natural rubber is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use. [11] This latex is used to make many other products including mattresses, [12] [13] gloves, swim caps, condoms, catheters and balloons.[ citation needed ]

Opium and opiates

Dried latex from the opium poppy is called opium, the source of several useful analgesic alkaloids such as codeine, thebaine, and morphine, the latter two of which can then further be used in the synthesis and manufacture of other (typically stronger) opioids for medicinal use, and of heroin for the illegal drug trade. The opium poppy is also the source of medically useful non-analgesic alkaloids, such as papaverine and noscapine.[ citation needed ]

Clothing

Latex is used in many types of clothing. Worn on the body (or applied directly by painting), it tends to be skin-tight, producing a "second skin" effect. [14]

Industrial and biological applications of synthetic latices

Synthetic latices are used in coatings (e.g., latex paint) and glues because they solidify by coalescence of the polymer particles as the water evaporates. These synthetic latices therefore can form films without releasing potentially toxic organic solvents in the environment. Other uses include cement additives and to conceal information on scratchcards. Latex, usually styrene-based, is also used in immunoassays. [15]

Allergic reactions

Some people only experience a mild allergy when exposed to latex, like eczema, contact dermatitis or developing a rash. [16]

Others have a serious latex allergy, and exposure to latex products such as latex gloves can cause anaphylactic shock. Guayule latex has only 2% of the levels of protein found in Hevea latices, and is being researched as a lower-allergen substitute. [17] Additionally, chemical processes may be employed to reduce the amount of antigenic protein in Hevea latex, yielding alternative materials such as Vytex Natural Rubber Latex which provide significantly reduced exposure to latex allergens.

About half of people with spina bifida are also allergic to natural latex rubber, as well as people who have had multiple surgeries, and people who have had prolonged exposure to natural latex. [18]

Microbial degradation

Several species of the microbe genera Actinomycetes , Streptomyces , Nocardia , Micromonospora , and Actinoplanes are capable of consuming rubber latex. [19] However, the rate of biodegradation is slow, and the growth of bacteria utilizing rubber as a sole carbon source is also slow. [20]

See also

Related Research Articles

<span class="mw-page-title-main">Natural rubber</span> Polymer harvested from certain trees

Rubber, also called India rubber, latex, Amazonian rubber, caucho, or caoutchouc, as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, Indonesia, and Cambodia are four of the leading rubber producers.

<span class="mw-page-title-main">Neoprene</span> Family of synthetic rubbers

Neoprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. Neoprene exhibits good chemical stability and maintains flexibility over a wide temperature range. Neoprene is sold either as solid rubber or in latex form and is used in a wide variety of commercial applications, such as laptop sleeves, orthopaedic braces, electrical insulation, medical gloves, liquid and sheet-applied elastomeric membranes or flashings, and automotive fan belts.

In polymer chemistry, emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomers, and surfactants. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer are emulsified in a continuous phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers. The name "emulsion polymerization" is a misnomer that arises from a historical misconception. Rather than occurring in emulsion droplets, polymerization takes place in the latex/colloid particles that form spontaneously in the first few minutes of the process. These latex particles are typically 100 nm in size, and are made of many individual polymer chains. The particles are prevented from coagulating with each other because each particle is surrounded by the surfactant ('soap'); the charge on the surfactant repels other particles electrostatically. When water-soluble polymers are used as stabilizers instead of soap, the repulsion between particles arises because these water-soluble polymers form a 'hairy layer' around a particle that repels other particles, because pushing particles together would involve compressing these chains.

<i>Asclepias</i> Genus of flowering plants

Asclepias is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans and many other species, primarily due to the presence of cardenolides. However, as with many such plants, some species feed upon them or from them. The most notable of them is the monarch butterfly, which uses and requires certain milkweeds as host plants for their larvae.

<span class="mw-page-title-main">Latex allergy</span> Medical condition

Latex allergy is a medical term encompassing a range of allergic reactions to the proteins present in natural rubber latex. It generally develops after repeated exposure to products containing natural rubber latex. When latex-containing medical devices or supplies come in contact with mucous membranes, the membranes may absorb latex proteins. In some susceptible people, the immune system produces antibodies that react immunologically with these antigenic proteins. Many items contain or are made from natural rubber, including shoe soles, pen grips, hot water bottles, elastic bands, rubber gloves, condoms, baby-bottle nipples, and balloons; consequently, there are many possible routes of exposure that may trigger a reaction. People with latex allergies may also have or develop allergic reactions to some fruits, such as bananas.

<span class="mw-page-title-main">Styrene-butadiene</span> Synthetic rubber polymer

Styrene-butadiene or styrene-butadiene rubber (SBR) describe families of synthetic rubbers derived from styrene and butadiene. These materials have good abrasion resistance and good aging stability when protected by additives. In 2012, more than 5.4 million tonnes of SBR were processed worldwide. About 50% of car tires are made from various types of SBR. The styrene/butadiene ratio influences the properties of the polymer: with high styrene content, the rubbers are harder and less rubbery. SBR is not to be confused with the thermoplastic elastomer, styrene-butadiene block copolymer, although being derived from the same monomers.

<i>Parthenium argentatum</i> Species of plant in the Asteraceae family native to the southwestern United States and Mexico

Parthenium argentatum, commonly known as the guayule, is a perennial woody shrub in the family Asteraceae that is native to the rangeland area of the Chihuahuan Desert; including the southwestern United States and northern Mexico. It was first documented by J.M. Bigelow in 1852 through the Mexican Boundary Survey and was first described by Asa Gray. Natural rubber, ethanol, non-toxic adhesives, and other specialty chemicals can be extracted from guayule. An alternative source of latex that is hypoallergenic, unlike the normal Hevea rubber, can also be extracted. While Castilla elastica was the most widely used rubber source of Mesoamericans in pre-Columbian times, guayule was also used, though less frequently. The name "guayule" derives from the Nahuatl word ulli/olli, "rubber".

<i>Papaver somniferum</i> Species of flowering plant in the family Papaveraceae

Papaver somniferum, commonly known as the opium poppy or breadseed poppy, is a species of flowering plant in the family Papaveraceae. It is the species of plant from which both opium and poppy seeds are derived and is also a valuable ornamental plant grown in gardens. Its native range was east of the Mediterranean Sea, but now is obscured by ancient introductions and cultivation, being naturalized across much of Europe and Asia.

<span class="mw-page-title-main">Phytochemistry</span> Study of phytochemicals, which are chemicals derived from plants

Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids.

A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32 million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubber, just like natural rubber, has many uses in the automotive industry for tires, door and window profiles, seals such as O-rings and gaskets, hoses, belts, matting, and flooring. They offer a different range of physical and chemical properties which can improve the reliability of a given product or application. Synthetic rubbers are superior to natural rubbers in two major respects: thermal stability, and resistance to oils and related compounds. They are more resistant to oxidizing agents, such as oxygen and ozone which can reduce the life of products like tires.

Nitrile rubber, also known as nitrile butadiene rubber, NBR, Buna-N, and acrylonitrile butadiene rubber, is a synthetic rubber derived from acrylonitrile (ACN) and butadiene. Trade names include Perbunan, Nipol, Krynac and Europrene. This rubber is unusual in being resistant to oil, fuel, and other chemicals.

<span class="mw-page-title-main">Foam latex</span>

Foam latex or latex foam rubber is a lightweight form of latex containing bubbles known as cells, created from liquid latex. The foam is generally created though the Dunlop or Talalay process in which a liquid latex is foamed and then cured in a mold to extract the foam.

A laticifer is a type of elongated secretory cell found in the leaves and/or stems of plants that produce latex and rubber as secondary metabolites. Laticifers may be divided into:

<span class="mw-page-title-main">Polyisoprene</span> Group of synthetic polymers, including cis-1,4-polyisoprene

Polyisoprene is strictly speaking a collective name for polymers that are produced by polymerization of isoprene. In practice polyisoprene is commonly used to refer to synthetic cis-1,4-polyisoprene, made by the industrial polymerisation of isoprene. Natural forms of polyisoprene are also used in substantial quantities, the most important being "natural rubber", which is derived from the sap of trees. Both synthetic polyisoprene and natural rubber are highly elastic and consequently used to make tires and a variety of other applications.

<span class="mw-page-title-main">Poppy straw</span> Portion of opium poppy

Poppy straw is derived from opium poppies that are harvested when fully mature and dried by mechanical means. Opium poppy straw is what remains after the seed pods have been harvested - that is, the dried stalks, stem and leaves of poppies grown for their seeds. The field-dried leaves, stalk, and seed pod are then used in commercial manufacture of morphine or other poppy-alkaloid derived drugs, by first processing the material, separating the seeds, and then making concentrate of poppy straw where no extraction using the traditional methods of latex extraction has been made. The straw was originally considered an agricultural by-product of the mechanised poppy seed harvest, which was primarily grown for its edible and oil-producing seed. This changed in 1927 when János Kabay developed a chemical process to extract morphine from the crushed capsule. Concentrated poppy straw, consisting mainly of the crushed capsule without the seeds, soon became a valuable source of morphine. Today, concentrate of poppy straw is a major source of many opiates and other alkaloids. It is the source of 90% of the world supply of legal morphine and in some countries it also is a source of illegal morphine, which could be processed into illegal heroin.

<i>Taraxacum kok-saghyz</i> Species of flowering plant

Taraxacum kok-saghyz, often abbreviated as TKS and commonly referred to as the Kazakh dandelion, rubber root, or Russian dandelion, is a species of dandelion native to Kazakhstan, Kyrgyzstan and Uzbekistan, notable for its production of high-quality rubber. T. kok-saghyz was discovered in Kazakhstan in 1932 by Soviet scientists seeking a domestic source of rubber.

<span class="mw-page-title-main">Yulex</span> Arizona agricultural products company

Yulex Corporation makes products from Guayule a residual agricultural material.

<i>Takhtajaniantha tau-saghyz</i> Species of flowering plant from central Asia

Takhtajaniantha tau-saghyz is a species of plant in the family Asteraceae.

David Spence was one of the pioneering rubber chemists. He helped the war effort during the Second World War by devising new ways of extracting natural rubbers from plants, and worked to improve the processing of the rubber. Over the course of his career, he worked to improve the dyeing processes for rubber products and the vulcanization of rubber, and in developing new accelerants for strengthening lower-quality natural rubber. In 1941, he became the first recipient of the Charles Goodyear Medal, awarded by the American Chemical Society.

The tissues that are concerned with the secretion of gums, resins, volatile oils, nectar latex, and other substances in plants are called secretory tissues. These tissues are classified as either laticiferous tissues or glandular tissues.

References

  1. ↑ Wang, Hui; Yang, Lijuan; Rempel, Garry L. (2013). "Homogeneous Hydrogenation Art of Nitrile Butadiene Rubber: A Review". Polymer Reviews. 53 (2): 192–239. doi:10.1080/15583724.2013.776586. S2CID   96720306.
  2. 1 2 3 4 5 6 7 8 Anurag A. Agrawal; d Kotaro Konno (2009). "Latex: a model for understanding mechanisms, ecology, and evolution of plant defense Against herbivory". Annual Review of Ecology, Evolution, and Systematics . 40: 311–331. doi:10.1146/annurev.ecolsys.110308.120307.
  3. ↑ Paul G. Mahlberg (1993). "Laticifers: an historical perspective". The Botanical Review . 59 (1): 1–23. doi:10.1007/bf02856611. JSTOR   4354199. S2CID   40056337.
  4. ↑ Harper, Douglas. "latex". Online Etymology Dictionary .
  5. ↑ latex . Charlton T. Lewis and Charles Short. A Latin Dictionary on Perseus Project .
  6. ↑ "Taraxacum kok-saghyz". Pfaf.org. Archived from the original on 2014-03-20. Retrieved 2013-03-21.
  7. ↑ Thomas M. Lewinsohn (1991). "The geographical distribution of plant latex". Chemoecology . 2 (1): 64–68. doi:10.1007/BF01240668. S2CID   44594197.
  8. ↑ Joseph F. James (1887). "The milkweeds". The American Naturalist . 21 (7): 605–615. doi: 10.1086/274519 . JSTOR   2451222.
  9. ↑ Buttery, R. R.; Boatman, S. G. (1976). Kozlowski, T. T. (ed.). Water Deficits and Plant Growth, Volume IV: Soil Water Measurement, Plant Responses, and Breeding for Drought Resistance. Vol. IV (1st ed.). New York, New York 10003: Academic Press, Inc. p. 252. ISBN   978-0124314269.{{cite book}}: CS1 maint: location (link)
  10. ↑ Mathews, Jennifer P. (2009). Chicle: The chewing gum of the Americas, from the ancient Maya to William Wrigley. Tucson: University of Arizona Press. ISBN   978-0-8165-2821-9.
  11. ↑ J. E. Bowers (1990). Natural Rubber-Producing Plants for the United States. Beltsville, MD: National Agricultural Library. pp.  1, 3. OCLC   28534889.
  12. ↑ Liman, Stacy (26 June 2020). "Latex Mattresses: The Best Latex Mattress Guide" . Retrieved 17 August 2020.
  13. ↑ Yurkovich, Dror. "Dunlop latex vs. Talalay latex". Getha. Archived from the original on 2021-04-13. Retrieved 2021-04-22.
  14. ↑ Kink and everyday life : interdisciplinary reflections on practice and portrayal. Kylo-Patrick R. Hart, Teresa Cutler-Broyles. Bingley. 2021. ISBN   978-1-83982-918-5. OCLC   1262726608.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  15. ↑ Akamine, Y.; Sato, S.; Kagaya, H.; Ohkubo, T.; Satoh, S.; Miura, M. (2018-04-20). "Comparison of electrochemiluminescence immunoassay and latex agglutination turbidimetric immunoassay for evaluation of everolimus blood concentrations in renal transplant patients". Journal of Clinical Pharmacy and Therapeutics. 43 (5): 675–681. doi: 10.1111/jcpt.12686 . ISSN   0269-4727.
  16. ↑ "Latex Allergy | Causes, Symptoms & Treatment". ACAAI Public Website. Retrieved 2019-03-24.
  17. ↑ Anderson, Christopher D.; Daniels, Eric S. (8 May 2018). Emulsion Polymerisation and Latex Applications. iSmithers Rapra Publishing. ISBN   9781859573815 . Retrieved 8 May 2018– via Google Books.
  18. ↑ "Latex allergy - Symptoms and causes". mayoclinic.com. Archived from the original on 7 October 2013. Retrieved 8 May 2018.
  19. ↑ Helge B. Bode; Axel Zeeck; Kirsten Plückhahn; Dieter Jendrossek (September 2000). "Physiological and Chemical Investigations into Microbial Degradation of Synthetic Poly(cis-1,4-isoprene)". Applied and Environmental Microbiology. 66 (9): 3680–3685. Bibcode:2000ApEnM..66.3680B. doi:10.1128/aem.66.9.3680-3685.2000. PMC   92206 . PMID   10966376.
  20. ↑ Rose, K.; Steinbuchel, A. (2 June 2005). "Biodegradation of Natural Rubber and Related Compounds: Recent Insights into a Hardly Understood Catabolic Capability of Microorganisms". Applied and Environmental Microbiology. 71 (6): 2803–2812. Bibcode:2005ApEnM..71.2803R. doi:10.1128/AEM.71.6.2803-2812.2005. PMC   1151847 . PMID   15932971.
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