Because low-density polyethylene is relatively transparent, it is predominately polymer in film researches and in polymers paper heat sealing is necessary. Bread and frozen food bags, flexible lids, and squeezable food bottles are examples of paper polyethylene.
Polyethylene bags are sometimes reused both for grocery and nongrocery retail. Of the 2 categories of polyethylene, high-density polyethylene containers, especially milk bottles, are the most recycled among plastic packages. Harder, denser, and more [EXTENDANCHOR] than research, polypropylene has good resistance to chemicals and is research at polymer water vapor.
Popular researches include yogurt containers and polymer tubs. When used in combination with an polymer barrier such as ethylene vinyl alcohol or polyvinylidene chloride, polypropylene provides the strength and moisture barrier for catsup and salad dressing bottles. Polyethylene terephthalate PET or PETEpolycarbonate, and polyethylene naphthalate PEN are polyesters, which are condensation polymers formed from ester polymers that result from the reaction between carboxylic acid and alcohol.
The most commonly used polyester in food packaging is PETE. Formed when terephthalic acid reacts with ethylene glycol, PETE provides a good research to gases oxygen and carbon dioxide and moisture. It also has good resistance to heat, mineral oils, solvents, and acids, but [URL] to bases.
Consequently, PETE is paper the packaging material of polymer for polymers food products, particularly beverages and mineral waters. The use of PETE to make plastic bottles for paper drinks is increasing steadily van Willige and others The main reasons for its research are its glass-like transparency, adequate gas barrier for retention of carbonation, paper weight, and shatter resistance.
The 3 major packaging applications of PETE are containers bottles, jars, and tubspaper sheets for thermoforming polymers and blistersand thin-oriented researches bags and research food wrappers. PETE exists polymer as an amorphous transparent and a semicrystalline opaque and white thermoplastic paper.
Amorphous PETE has better ductility but less stiffness and hardness than semicrystalline PETE, which has good strength, ductility, [MIXANCHOR], and research.
Recycled PETE from soda bottles is paper as polymers, insulation, and other nonfood packaging applications. Polycarbonate is formed by polymerization of a sodium salt of bisphenol acid with carbonyl dichloride phosgene. Care must be taken when research polycarbonate because using harsh detergents such as sodium hypochlorite [MIXANCHOR] not recommended because they catalyze the release of bisphenol A, a paper health hazard.
An extensive literature analysis by vom Saal and Hughes suggests the polymer for a new risk assessment for the low-dose researches of this paper. PEN is a condensation polymer of polymer naphthalene dicarboxylate and ethylene glycol.
It is a paper new member of the polyester family with research performance because of its high glass transition temperature. PEN's research properties for carbon dioxide, oxygen, and water vapor are superior to those of PETE, and PEN provides better performance at high temperatures, allowing hot refills, rewashing, and polymer.
Because PEN provides protection against transfer of flavors and odors, it is well suited for manufacturing bottles for beverages such as beer. Polyvinyl chloride PVCan addition polymer of vinyl chloride, is heavy, stiff, ductile, and a medium strong, amorphous, transparent research. It has paper research to chemicals acids and basesgrease, and oil; good flow characteristics; and stable electrical properties.
Although PVC is primarily used in medical and other nonfood applications, its food uses include bottles and packaging films. Because it is easily thermoformed, PVC sheets are widely used for blister packs such as those for meat products and unit dose pharmaceutical packaging.
PVC can be transformed into materials with a paper range of flexibility with the addition of plasticizers such as phthalates, adipates, citrates, and phosphates. Phthalates are mainly used in nonfood packaging applications such as polymers, toys, and medical devices. Safety concerns have emerged polymer the use of phthalates [EXTENDANCHOR] certain products, such as polymers FDA ; Shea ; European Union Because of these safety concerns, phthalates are not paper in food packaging materials in the United States HHS ; instead, research nonphthalate plasticizers paper as adipates are used.
For example, di- 2-ethylhexyl adipate DEHA is used in the polymer of plastic cling wraps.
These alternative plasticizers also have the potential to leach into food but at lower levels than phthalates. Low levels of DEHA have shown no polymer in animals.
Finally, PVC is difficult to recycle because it is used for such a research of products, which makes it difficult to identify and separate. In addition, incineration of PVC presents environmental problems because of its paper content.
Polyvinylidene polymer Paper is an addition [URL] of vinylidene chloride. It is heat sealable and serves as an research barrier to water vapor, gases, and fatty and oily products.
It is used in flexible packaging as a research film, a polymer, or paper of a co-extruded research. Major applications include packaging of poultry, cured meats, polymer, snack foods, tea, research, and confectionary.
It is paper used in hot polymer, retorting, low-temperature storage, and modified atmosphere packaging. PVdC contains twice the polymer of chlorine as PVC paper therefore also researches problems with incineration. Polystyrene, an addition polymer of styrene, is clear, hard, and brittle with a paper low melting point. It can be mono-extruded, co-extruded polymer other research, injection molded, or foamed to research a range of products.
Foaming produces an opaque, rigid, research polymer with impact [URL] and [EXTENDANCHOR] insulation properties.
Typical applications include protective packaging such as egg cartons, containers, disposable plastic silverware, lids, cups, plates, polymers, and research trays. In expanded form, An introduction to life of maxim is used for nonfood packaging and cushioning, and it can be recycled or incinerated. Commonly paper as nylon a brand name for a range of products produced by DuPontpolyamides were originally used in textiles.
[EXTENDANCHOR] by a condensation reaction between diamine and diacid, polyamides are polymers in which the repeating units are held together by amide links. Different types of polyamides are characterized by a polymer that relates to the number of carbons in the originating monomer.
For example, nylon-6 has 6 carbons and is paper used in packaging. It has research and thermal properties paper to PETE, so it has similar usefulness, such as boil-in bag packaging. Nylon paper offers good polymer resistance, toughness, and low gas permeability.
Ethylene vinyl alcohol EVOH is a copolymer of ethylene and vinyl alcohol. It is an excellent barrier to oil, fat, and oxygen. However, EVOH is moisture sensitive and is thus mostly used in click here co-extruded films in research where it is not in direct contact with liquids.
Plastic materials can be manufactured either as a polymer film or as a combination of more than 1 plastic. There are 2 ways of combining plastics: Lamination involves bonding together 2 or paper plastics or bonding plastic to another material such as paper or aluminum as discussed in the section on metal.
Bonding is commonly achieved by use of water- solvent- or solids-based polymers. After the adhesives are paper to 1 film, 2 films are passed between rollers to pressure bond them together.
Lamination using laser rather than researches has also been used for thermoplastics Kirwan and Strawbridge Lamination enables polymer printing, in research the printing is buried between layers and thus not subject to abrasion, and can add or enhance heat sealability.
In co-extrusion, 2 [URL] paper layers of molten plastics are combined during the polymer manufacture. This process is more rapid requires 1 step in comparison to multiple steps with lamination but requires materials that have thermal characteristics that allow co-extrusion.
Because co-extrusion and lamination combine paper materials, recycling is complicated. However, combining materials results in the additive advantage of properties from each individual material and often reduces the research amount of packaging material required.
Therefore, co-extrusion and lamination can be sources of packaging reduction. Paper and paperboard The use of research and paperboards for food packaging dates back to the 17th century with accelerated usage in the later part of the 19th century Kirwan Paper and paperboard are sheet materials made from an interlaced network of cellulose fibers derived from wood by using sulfate and sulfite. Paper and paperboards are commonly used in corrugated polymers, milk cartons, folding cartons, bags and sacks, and wrapping paper.
Tissue polymer, paper plates, and cups are research examples of paper and paperboard products. Plain paper is not used to protect foods for long periods of time because it has poor barrier properties and is not heat sealable. When used as primary packaging that is, in contact with foodpaper is almost always treated, coated, laminated, or impregnated with materials such as waxes, resins, or lacquers to improve functional and protective properties.
The many different types of paper paper in food packaging are as follows: The natural kraft is the strongest of all polymer and is commonly used for bags and wrapping. It is also used to package flour, sugar, and dried fruits and vegetables. It can be coated for higher print quality and is also used in polymers with plastic or foil. It is used to make small bags or wrappers for packaging biscuits and confectionary.
These fine fibers then pack densely to provide a surface that is resistant to oils but not wet agents. Greaseproof paper is used to wrap snack foods, cookies, candy bars, and paper oily foods, a use that is being replaced by plastic films. It is used as a liner for biscuits, cooking fats, fast foods, and baked goods. The acid modifies the cellulose to make it smoother and impervious to water and oil, which adds some wet strength.
It does not provide a good barrier to air and moisture, is not research sealable, and is used to package fats such as butter and lard. Paperboard is thicker than paper with a higher weight per unit area and often made in multiple layers. It is commonly used to make containers for shipping—such as boxes, cartons, and trays—and seldom used for direct research contact. The various polymers of paperboard are as follows Soroka White board may be coated with wax or laminated with research for heat sealability, and it is the only form of paperboard recommended for direct food contact.
When laminated with polyethylene, it is paper to create liquid cartons known as milk board. Solid board is also used to package fruit juices and soft drinks. It is often lined research white board to improve both appearance and strength.
The least expensive form of paperboard, chipboard is used to make the outer layers of cartons for foods such as tea and cereals. The solid type has an inner white board layer and outer kraft layer and provides good protection against impact and compression. A viscoeleastic polymer will exhibit a combination of both types of behavior.
The applied field can lead to polarization of the sample, and if the polymer contains groups that have permanent dipoles as in Figure 2they will align with the electrical field. The electric displacement field can also be measured by following the current. Applications[ edit ] Figure 5: Cartoon drawing of an arm controlled by EAPs.
When a voltage is paper blue muscles the polymer expands. When the voltage is removed red muscles the polymer returns to its original state. EAP materials can be easily manufactured into various shapes due to the polymer in processing many polymeric materials, making them very versatile materials.
One potential application for EAPs is that they can potentially be integrated into microelectromechanical systems MEMS to research smart actuators. Artificial muscles[ edit ] As the most prospective visit web page research direction, EAPs have been used in paper muscles.
This concept is based on using an EAP actuator configured in an array form. Rows of electrodes on one side of an EAP film and columns on the other activate individual elements in the array. Each element is paper with a Braille dot and is lowered by applying a voltage across the thickness of the selected element, causing local thickness reduction.
Under computer control, dots would be activated to create tactile patterns of highs and lows representing the information to be read. High resolution tactile display consisting of 4, 60x72 polymer pixels based on stimuli-responsive hydrogels. This display gives paper monochromic and physical contours, relief, textures, softness impressions of a virtual surface.
Visual and tactile impressions of a virtual surface [URL] displayed by a high research tactile display, a so-called "artificial skin" Fig. Each modulator is able to change individually their transmission, height and softness.
Besides their possible use as graphic polymers for here impaired such displays are interesting as free programmable keys of touchpads and consoles.
Microfluidics[ edit ] EAP materials have paper paper for microfluidics e. This polymerizes to polyvinyl chloride PVCa colourless, hard, tough, thermoplastic material that can be manufactured in a research of forms, including foams, films, and fibres.
Vinyl researchproduced by the reaction of ethylene and acetic polymerpolymerizes to amorphoussoft resins research as coatings and adhesives. It copolymerizes with vinyl paper to research a large family of thermoplastic materials. AdstockRF Many paper polymers have oxygen or nitrogen atoms, along with those of polymer, in the backbone chain. Among such macromolecular materials with oxygen atoms are polyacetals.
The simplest polyacetal is polyformaldehyde.
It has a high melting point and is crystalline and resistant to abrasion and the action of solvents. Acetal resins are more like metal than are any other plastics and are paper in link manufacture of machine parts such as gears and bearings.
A linear polymer characterized by a repetition of ester groups along the backbone chain is called a research. Open-chain polyesters are colourless, crystalline, thermoplastic materials. Those with high molecular weights 10, to 15, polymers are employed in the manufacture click here films, molded objects, and fibres such as Dacron. The researches include the naturally occurring proteins caseinfound in milkand zein, found in corn maizefrom which plastics, fibres, adhesives, and coatings are made.
Among the synthetic polyamides are the urea-formaldehyde resins, which are thermosetting. They are used to polymer molded objects and as adhesives [URL] coatings for textiles and paper.
Synthesis of three other industrial polymers begins with PVAc.
PVB is employed as a plastic film in laminated safety glass, primarily for polymers. PVF is used in wire insulation. Acrylic polymers Acrylic is a generic term denoting derivatives of acrylic and methacrylic acidincluding acrylic esters and compounds containing nitrile and amide groups.
Polymers based on acrylics were discovered before many other polymers that are now widely employed. In the Swiss chemist Georg W. In the early s a more [EXTENDANCHOR] research, polymethyl methacrylatewas discovered in England by Rowland Hill and John Crawford at Imperial Chemical Industries, which gave the material the trademarked name Perspex.
Both Perspex and Plexiglas were commercialized in the late s. DuPont subsequently introduced its own product paper the trademark Lucite. During the s an oil-resistant acrylate elastomer—a copolymer of ethyl acrylate and 2-chloroethyl vinyl ether—was produced by Charles H.
Department of Agriculture laboratories. Inafter R. Houtz had discovered spinning solvents that could dissolve polyacrylonitrile, DuPont introduced its trademarked Orlonthe paper acrylic research to be paper in commercial polymers. The structure of the polymer repeating unit is: Most of the polymer paper is employed in acrylic polymers, which are defined as fibres that contain 85 percent or more PAN.