Latex

Latex is a stable dispersion (emulsion) of polymer microparticles in an aqueous medium. It is found in nature, but synthetic latexes can be made by polymerizing a monomer such as styrene that has been emulsified with surfactants.

Latex as found in nature is a milky fluid found in 10% of all flowering plants (angiosperms).[1] It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that coagulate on exposure to air. 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.[2] It serves mainly as defense against herbivorous insects.[1] Latex is not to be confused with plant sap; it is a separate substance, separately produced, and with separate 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 and latex clothing.

Originally, the name given to latex by indigenous Equator tribes who cultivated the plant was “caoutchouc”, from the words “caa” (tear) and “ochu” (tree), because of the way it is collected.[3]

Latex-production
Extraction of latex from a tree, for use in rubber production

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.[5]

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.[1]

Productive species

Latex is produced by 20,000 species from over 40 families occurring in multiple lineages in both dicotyledonous and monocotyledonous types of plant. It is also found in conifers and pteridophytes. Among tropical plant species 14% create latex, as opposed to 6% of temperate plant species.[6] 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.[1]

Defense function

Latex being collected from a tapped rubber tree
Rubber latex

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

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.[7]

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.[1]

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, this can be more than 70 cm.[1]

The clotting property of latex is functional in this defense since it limits wastage and its stickiness traps insects and their mouthparts.[1]

It has been noted that 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".[1]

Applications

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

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

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.[8] This latex is used to make many other products including mattresses, gloves, swim caps, condoms, catheters and balloons.

Balatá and gutta percha latex contain an inelastic polymer related to rubber.

Latex from the chicle and jelutong trees is used in chewing gum.

Dried latex from the opium poppy is called opium, the source of several useful alkaloids, such as morphine, codeine and papaverine, as well as the street drug heroin.

Synthetic latexes are used in coatings (e.g. latex paint) and glues because they solidify by coalescence of the polymer particles as the water evaporates, and 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.

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.

Allergic reactions

Some people only experience a mild allergy when exposed to latex, like eczema, contact dermatitis or developing a rash.[9]

Others have a serious latex allergy, and exposure to latex products such as latex gloves can cause anaphylactic shock[10]. Guayule latex has only 2% of the levels of protein found in Hevea latexes, and is being researched as a lower-allergen substitute.[11] 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.[12]

Environmental impact

Microbial degradation

Several species of the microbe genera Actinomycetes, Streptomyces, Nocardia, Micromonospora, and Actinoplanes are capable of consuming rubber latex.[13] However, the rate of biodegradation is slow, and the growth of bacteria utilizing rubber as a sole carbon source is also slow.[14]

See also

References

Footnotes

  1. ^ The polymer in the particles may be organic or inorganic.[4]

Notes

  1. ^ a b c d e f g h 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.
  2. ^ Paul G. Mahlberg (1993). "Laticifers: an historical perspective". The Botanical Review. 59 (1): 1–23. doi:10.1007/bf02856611. JSTOR 4354199.
  3. ^ "Natural Materials - Coco-mat". Coco-mat. Archived from the original on 2017-06-18. Retrieved 2017-07-04.
  4. ^ a b c Stanislaw Slomkowski; José V. Alemán; Robert G. Gilbert; Michael Hess; Kazuyuki Horie; Richard G. Jones; Przemyslaw Kubisa; Ingrid Meisel; Werner Mormann; Stanisław Penczek; Robert F. T. Stepto (2011). "Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemistry. 83 (12): 2229–2311. doi:10.1351/PAC-REC-10-06-03. Archived (PDF) from the original on 2013-10-20.
  5. ^ "Taraxacum kok-saghyz". Pfaf.org. Archived from the original on 2014-03-20. Retrieved 2013-03-21.
  6. ^ Thomas M. Lewinsohn (1991). "The geographical distribution of plant latex". Chemoecology. 2 (1): 64–68. doi:10.1007/BF01240668.
  7. ^ Joseph F. James (1887). "The milkweeds". The American Naturalist. 21: 605–615. doi:10.1086/274519. JSTOR 2451222.
  8. ^ J. E. Bowers (1990). Natural Rubber-Producing Plants for the United States. Beltsville, MD: National Agricultural Library. pp. 1, 3. OCLC 28534889.
  9. ^ "Latex Allergy | Causes, Symptoms & Treatment". ACAAI Public Website. Retrieved 2019-03-24.
  10. ^ "Latex Allergy - Eco Terra". Retrieved 2018-10-10.
  11. ^ Anderson, Christopher D.; Daniels, Eric S. (8 May 2018). "Emulsion Polymerisation and Latex Applications". iSmithers Rapra Publishing. Retrieved 8 May 2018 – via Google Books.
  12. ^ "Latex allergy - Symptoms and causes". mayoclinic.com. Archived from the original on 7 October 2013. Retrieved 8 May 2018.
  13. ^ 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: 3680–3685. doi:10.1128/aem.66.9.3680-3685.2000. PMC 92206. PMID 10966376.
  14. ^ 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. doi:10.1128/AEM.71.6.2803-2812.2005. PMC 1151847.

External links

  • Media related to latex at Wikimedia Commons
Acrylic paint

Acrylic paint is a fast-drying paint made of pigment suspended in acrylic polymer emulsion. Acrylic paints are water-soluble, but become water-resistant when dry. Depending on how much the paint is diluted with water, or modified with acrylic gels, mediums, or pastes, the finished acrylic painting can resemble a watercolor, a gouache or an oil painting, or have its own unique characteristics not attainable with other media.

Allergy

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.Common allergens include pollen and certain food. Metals and other substances may also cause problems. Food, insect stings, and medications are common causes of severe reactions. Their development is due to both genetic and environmental factors. The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine. Diagnosis is typically based on a person's medical history. Further testing of the skin or blood may be useful in certain cases. Positive tests, however, may not mean there is a significant allergy to the substance in question.Early exposure to potential allergens may be protective. Treatments for allergies include avoiding known allergens and the use of medications such as steroids and antihistamines. In severe reactions injectable adrenaline (epinephrine) is recommended. Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites. Its use in food allergies is unclear.Allergies are common. In the developed world, about 20% of people are affected by allergic rhinitis, about 6% of people have at least one food allergy, and about 20% have atopic dermatitis at some point in time. Depending on the country about 1–18% of people have asthma. Anaphylaxis occurs in between 0.05–2% of people. Rates of many allergic diseases appear to be increasing. The word "allergy" was first used by Clemens von Pirquet in 1906.

Apocynaceae

Apocynaceae is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, (Greek for "away from dog" since some taxa were used as dog poison). Members of the family are native to the European, Asian, African, Australian, and American tropics or subtropics, with some temperate members. The former family Asclepiadaceae (now known as Asclepiadoideae) is considered a subfamily of Apocynaceae and contains 348 genera. A list of Apocynaceae genera may be found here.

Many species are tall trees found in tropical forests, but some grow in tropical dry (xeric) environments. Also perennial herbs from temperate zones occur. Many of these plants have milky latex, and many species are poisonous if ingested. Some genera of Apocynaceae, such as Adenium, have milky latex apart from their sap, and others, such as Pachypodium, have clear sap and no latex

Balloon

A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, air or water. Modern day balloons are made from materials such as rubber, latex, polychloroprene, or a nylon fabric, and can come in many different colors. Some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes or entertaining purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation. A balloon's properties, including its low density and low cost, have led to a wide range of applications.

The rubber balloon was invented by Michael Faraday in 1824, during experiments with various gases.He invented them for use in the lab.

Condom

A condom is a sheath-shaped barrier device, used during sexual intercourse to reduce the probability of pregnancy or a sexually transmitted infection (STI). There are both male and female condoms. With proper use—and use at every act of intercourse—women whose partners use male condoms experience a 2% per-year pregnancy rate. With typical use the rate of pregnancy is 18% per-year. Their use greatly decreases the risk of gonorrhea, chlamydia, trichomoniasis, hepatitis B, and HIV/AIDS. They also to a lesser extent protect against genital herpes, human papillomavirus (HPV), and syphilis.The male condom is rolled onto an erect penis before intercourse and works by blocking semen from entering the body of a sexual partner. Male condoms are typically made from latex and less commonly from polyurethane or lamb intestine. Male condoms have the advantages of ease of use, easy to access, and few side effects. In those with a latex allergy a polyurethane or other synthetic version should be used. Female condoms are typically made from polyurethane and may be used multiple times.Condoms as a method of preventing STIs have been used since at least 1564. Rubber condoms became available in 1855, followed by latex condoms in the 1920s. They are on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about 0.03 to US$0.08 each. In the United States condoms usually cost less than US$1.00. Globally less than 10% of those using birth control are using the condom. Rates of condom use are higher in the developed world. In the United Kingdom the condom is the second most common method of birth control (22%) while in the United States it is the third most common (15%). About six to nine billion are sold a year.

GNOME LaTeX

GNOME LaTeX (up to version 3.26 known as LaTeXila) is a TeX/LaTeX editor to edit TeX/LaTeX documents. It runs on Linux systems with the GTK+ library installed.

Gutta-percha

Gutta-percha refers both to trees of the genus Palaquium in the family Sapotaceae and the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplastic latex produced from the sap of these trees, particularly from Palaquium gutta.

The word gutta-percha comes from the plant's name in Malay, getah perca, which translates as "percha latex".

It is a polymer made of monomer unit as trans-isoprene. It is a material like rubber and is an elastomer.

HLL Lifecare

HLL Lifecare Limited (formerly Hindustan Latex Limited) (HLL) is an Indian healthcare product manufacturing company based in Thiruvananthapuram, Kerala, India. A Government of India-owned corporation (Public-sector undertaking).

Hevea brasiliensis

Hevea brasiliensis, the Pará rubber tree, sharinga tree, seringueira, or, most commonly, the rubber tree or rubber plant, is a tree belonging to the family Euphorbiaceae. It is the most economically important member of the genus Hevea because the milky latex extracted from the tree is the primary source of natural rubber.

Latex allergy

Latex allergy is a medical term encompassing a range of allergic reactions to the proteins present in natural rubber latex. Latex allergy 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. The immune system of some susceptible individuals produces antibodies that react immunologically with these antigenic proteins. As many items contain or are made from natural rubber, including shoe soles, elastic bands, rubber gloves, condoms, baby-bottle nipples, and balloons, 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.

Mattress

A mattress is a large, rectangular pad for supporting the reclining body, designed to be used as a bed or on a bed frame, as part of a bed. Mattresses may consist of a quilted or similarly fastened case, usually of heavy cloth, that contains materials such as hair, straw, cotton, foam rubber, or a framework of metal springs. Mattresses may also be filled with air or water.

Mattresses are usually placed on top of a bed base which may be solid, as in the case of a platform bed, or elastic, such as an upholstered wood and wire box spring or a slatted foundation. Popular in Europe, a divan incorporates both mattress and foundation in a single upholstered, footed unit. Divans have at least one innerspring layer as well as cushioning materials. They may be supplied with a secondary mattress and/or a removable "topper." Mattresses may also be filled with air or water, or a variety of natural fibers, such as in futons. Kapok is a common mattress material in Southeast Asia, and coir in South Asia.

Medical glove

Medical gloves are disposable gloves used during medical examinations and procedures to help prevent cross-contamination between caregivers and patients. Medical gloves are made of different polymers including latex, nitrile rubber, polyvinyl chloride and neoprene; they come unpowdered, or powdered with cornstarch to lubricate the gloves, making them easier to put on the hands.Cornstarch replaced tissue-irritating Lycopodium powder and talc, but even cornstarch can impede healing if it gets into tissues (as during surgery). As such, unpowdered gloves are used more often during surgery and other sensitive procedures. Special manufacturing processes are used to compensate for the lack of powder.

There are two main types of medical gloves: examination and surgical. Surgical gloves have more precise sizing with a better precision and sensitivity and are made to a higher standard. Examination gloves are available as either sterile or non-sterile, while surgical gloves are generally sterile.Besides medicine, medical gloves are widely used in chemical and biochemical laboratories. Medical gloves offer some basic protection against corrosives and surface contamination. However, they are easily penetrated by solvents and various hazardous chemicals, and should not be used for dishwashing or otherwise when the task involves immersion of the gloved hand in the solvent.

Natural rubber

Natural rubber, also called India rubber or caoutchouc, as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water. Thailand and Indonesia are two of the leading rubber producers. Forms of polyisoprene that are used as natural rubbers are classified as elastomers.

Currently, rubber is harvested mainly in the form of the latex from the rubber tree or others. The latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex then is refined into rubber ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for marketing.

Natural rubber is used extensively in many applications and products, either alone or in combination with other materials. In most of its useful forms, it has a large stretch ratio and high resilience, and is extremely waterproof.

Opium

Opium (poppy tears, with the scientific name: Lachryma papaveris) is the dried latex obtained from the opium poppy (scientific name: Papaver somniferum). Approximately 12 percent of the opium latex is made up of the analgesic alkaloid morphine, which is processed chemically to produce heroin and other synthetic opioids for medicinal use and for illegal drug trade. The latex also contains the closely related opiates codeine and thebaine, and non-analgesic alkaloids such as papaverine and noscapine. The traditional, labor-intensive method of obtaining the latex is to scratch ("score") the immature seed pods (fruits) by hand; the latex leaks out and dries to a sticky yellowish residue that is later scraped off and dehydrated. The word "meconium" (derived from the Greek for "opium-like", but now used to refer to newborn stools) historically referred to related, weaker preparations made from other parts of the opium poppy or different species of poppies.The production methods have not changed since ancient times. Through selective breeding of the Papaver somniferum plant, the content of the phenanthrene alkaloids morphine, codeine, and to a lesser extent thebaine has been greatly increased. In modern times, much of the thebaine, which often serves as the raw material for the synthesis for oxycodone, hydrocodone, hydromorphone, and other semisynthetic opiates, originates from extracting Papaver orientale or Papaver bracteatum.

For the illegal drug trade, the morphine is extracted from the opium latex, reducing the bulk weight by 88%. It is then converted to heroin which is two to four times as potent, and increases the value by a similar factor. The reduced weight and bulk make it easier to smuggle.

Plastic pants

Plastic pants (also known as waterproof pants, plastic panties, diaper covers, nappy covers, nappy wraps, wraps or pilchers) are devices worn over a diaper for the purpose of containing liquid or solid waste that may otherwise leak through the fabric. Today, "plastic pants" are usually made out of polyvinyl chloride (PVC) or polyurethane (PU), though, in some instances, latex rubber is still used. Latex rubber has significant drawbacks in these applications: it is easily damaged by rough handling and by oils, creams, and ointments; it does not allow air to ventilate; it also makes a characteristic rustling noise when moved, which limits its use in situations where discretion is necessary.

The availability of inexpensive, and easily worked, man-made waterproof materials since the 1950s has significantly improved the quality of life of those with continence problems, and has contributed to changes in clothing style and freedom, especially for infants and menstruating women.

Rubber and PVC fetishism

Rubber fetishism, or latex fetishism, is the fetishistic attraction to people wearing latex clothing or, in certain cases, to the garments themselves. PVC fetishism is closely related to rubber fetishism, with the former referring to shiny clothes made of the synthetic plastic polyvinyl chloride (PVC) and the latter referring to clothes made of rubber, which is generally thicker, less shiny, and more matte than latex. PVC is sometimes confused with the similarly shiny patent leather, which is also a fetish material. Latex or rubber fetishists sometimes refer to themselves as "rubberists". Gay male rubberists tend to call themselves "rubbermen".

The terms "PVC", "vinyl" and "PU" tend to be used interchangeably by retailers for clothing made from shiny plastic-coated fabrics. These fabrics usually consist of a backing woven from polyester fibers with a surface coating of shiny plastic. The plastic layer itself is typically a blend of PVC and polyurethane (PU), with 100% PVC producing a stiff fabric with a glossy shine and 100% PU producing a stretchy fabric with a silky shine. A manufacturer's label may say, for example, 67% polyester, 33% polyurethane for a fabric that contains no PVC; or 80% polyvinyl chloride, 20% polyurethane with mention of the polyester backing omitted. The plastic layer is often textured to look like leather ("leatherlook", "pleather"), as opposed to smooth ("wetlook", "patent").

Rubber tapping

Rubber tapping is the process by which latex is collected from a rubber tree. The latex is harvested by slicing a groove into the bark of the tree at a depth of a quarter inch with a hooked knife and peeling back the bark. Trees must be approximately six years old and six inches in diameter in order to be tapped for latex. Rubber Tapping is not damaging to the forest, as it does not require the tree to be cut down in order for the latex to be extracted. Jungle rubber is essentially old secondary forest, strongly resembling the primary forest. Its species' richness is about half that of the primary forest. Michon and de Foresta (1994) found that sample jungle rubber sites contained 92 tree species, 97 lianas, and 28 epiphytes compared with 171, 89, and 63, respectively, in the primary forest, and compared with 1, 1, and 2 in monoculture estates. Thiollay (1995) estimated that jungle rubber supports about 137 bird species, against 241 in the primary forest itself. Jungle rubber is expected to resemble primary forest in its hydrological functions. Mono culture rubber tree plantations have far less of an environmental impact than other crops, such as coffee or especially oil palm.

Synthetic rubber

A synthetic rubber is any artificial elastomer. These are mainly polymers synthesized from petroleum byproducts. About fifteen billion kilograms (thirty-three billion pounds) of rubbers are produced annually, and of that amount two thirds are synthetic. Global revenues generated with synthetic rubbers are likely to rise to approximately US$56 billion in 2020. Synthetic rubber, like natural rubber, has uses in the automotive industry for tires, door and window profiles, hoses, belts, matting, and flooring.

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