Knowledge and living tips

How is cling film made

posted Jul 6, 2012, 2:06 AM by BENKAI Co

Cling film


Plastic wrap - BENKAI Co.,Ltd

posted Jun 21, 2012, 8:21 PM by BENKAI Co

Plastic wrap was first made from PVC, which remains the most common material, but non-PVC alternatives are now being sold because of concerns about the risk in transfer of plasticizers from PVC into food. For food cateringapplications, PVC is the most common. For household use, LDPE is gaining market share because it is purportedly safer.

More and more countries over the world are concerned about the environmental effect of PVC, as the material is said to be toxic and harder to recycle. Nevertheless, PVC is still used because its stretching properties offer excellent food catering presentation on the shelf, and it clings well to more kinds of surfaces. Even so, some countries are starting to ban the use of PVC in toys for infants and food contact applications.

The original Saran Wrap is made of polyvinylidene chloride (PVdC). In July, 2004 the name Saran Original was changed to Saran Premium and the formulation was changed to low density polyethylene (LDPE). SC Johnson claimed that this change was a result of an initiative to look for more sustainable and environmentally acceptable plastic. The film in Saran Premium Wrap does not contain chlorine. However, LDPE does not possess the same barrier qualities to oxygen, aroma, and flavor molecules that vinylidene chloride copolymers do, making the new formulation a lower quality plastic wrap, as it is not as useful in protecting from spoilage or flavour loss.[citation needed] PVC is not impermeable, but adheres well. LDPE is impermeable but doesn't cling as well.[3]

The PVC-based films contain plasticizers, most often bis(2-ethylhexyl) adipate (DEHA), but phthalates (most often dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP)), in spite of being prohibited in most countries, also cause concern. The plasticizers were found to migrate to some foods, for example cheeses or fatty fish and meat. In the UK, polymerized plasticizers replaced DEHP in this application, largely eliminating the problem.[4]

A common alternative to PVC is low density polyethylene (LDPE), which is less clingy than PVC, but also does not contain traces of potentially toxic additives. Newer production processes are closing the clingy gap between PVC and LDPE. Linear low density polyethylene (LLDPE) is sometimes added to the material, as it increases the clinginess and the tensile strength of the film.[5] Brands like Glad Cling Wrap or Handi-Wrap are LDPE-based. Saran Premium Wrap, a newer version of Saran Wrap, is based on LDPE as well.

Glad Press'n Seal has its surface covered by shaped dimples, which hold the adhesive away from the surface. While being handled, the wrap is unsticky, but when pressure is applied the dimples are flattened and the adhesive pushed against the contacting surface, sticking them together.[6]The adhesive used is a special edible type similar to chewing gum.[7]

PVdC has better barrier properties than the more-permeable LDPE, making the foods wrapped in it less subject to freezer burn.[citation needed] However, LDPE is substantially cheaper and easier to make.

Natural polymers of LDPE and PVdC are insufficiently clingy on their own, and they do not adhere to themselves. To achieve the desired clinginess, certain polymers with lower molecular weight have to be added; the most common two are polyisobutene (PIB), and poly[ethylene-vinylacetate](EVA) copolymer. Their chains readily interact with each other and their lower molecular weight makes them more mobile within the host polymer matrix.


From Wikipedia, the free encyclopedia

HDPE / LDPE /LLDPE

posted Apr 5, 2012, 1:03 AM by BENKAI Co   [ updated Apr 5, 2012, 1:17 AM ]

高密度聚乙烯 (HDPE)
High-density Polyethylene (HDPE)
HDPE is a highly crystalline non-polar thermoplastic resin produced through the copolymerization of ethylene and a small amount of α-olefin monomer. HDPE is synthesized under low pressure and is therefore also called low-pressure polyethylene. HDPE is mainly a linear molecular structure and has little branching. It has a high degree of crystallization and high density. It can withstand high temperatures and has good rigidity and mechanical strength and anti-chemical corrosion.Produces a full grade of HDPE, which cover all fields of HDPE applications, including film, blow-molding, extrusion molding,injection molding, pipes, wire & cable and base material for producing chlorinated polyethylene.
Applications
HDPE is suitable for many plastic molding methods. Blow molding can be used for making various types of bottles, cans and industrial tanks and barrels. Injection molding is used for making various containers and goods of daily use, such as basins, barrels and baskets and furniture. Extrusion molding is used for making pipes, strapping tapes, fibers and single filaments and can also be used for making wires & cables covering materials and synthetic paper. After a large amount of inorganic filler is added, HDPE can also be used as an alternative to timber and cardboards for making calcium plastic packing containers, furniture, doors and windows.

低密度聚乙烯(LDPE)
Low-density polyethylene (LDPE)
Low-density polyethylene LDPE is a synthetic resin using a high pressure process via free radical polymerization of ethylene and is therefore also called “high-pressure polyethylene”. Since its molecular chain has many long and short branches, LDPE is less crystalline than high-density polyethylene (HDPE) and its density is lower. It features light, exible, good freezing resistance and impact resistance. LDPE is chemically stable. It has good resistance to acids (except strongly oxidizing acids), alkali, salt, excellent electrical insulation properties. Its vapor penetration rate is low. LDPE has high uidity and good processability. It is suitable for being used in all types of thermoplastic processing processes,such as injection molding, extrusion molding, blow molding,rotomolding, coating, foaming, thermoforming, hot-jet welding and thermal welding.
Applications
LDPE is principally used for making films. It is widely used in the production of agricultural film (mulching film and shed film), packaging lm (for use in packing candies, vegetables and frozen food), blown lm for packaging liquid (for use in packaging milk,soy sauce, juice, bean curds and soy milk), heavy-duty packaging bags, shrinkage packaging film, elastic film, lining film, buildinguse film, general-purpose industrial packaging film and food bags. LDPE is also widely used in the production of wire & cable insulation sheath. Cross-linked LDPE is the main material used in the insulation layer of high-voltage cables. LDPE is also used in the production of injection-molded products (such as artificial flowers,medical instruments, medicine and food packaging material) and extrusion-molded tubes, plates, wire & cable coatings and pro led plastic products. LDPE is also used for making blow-molded hollow products such as containers for holding food, medicine, cosmetics and chemical products, and tanks.

線型低密度聚乙烯 (LLDPE)
Linear Low-density Polyethylene (LLDPE)
Linear low-density polyethylene (LLDPE) is a copolymer produced by polymerization of ethylene and α-olefin (such as butene-1, hexene-1) at low pressure. It is low and medium density polyethylene with short chains branching. LLDPE has a narrow molecular weight distribution. LLDPE is manufactured by polymerization of ethylene and α-olefin monomers in the presence of catalysts using UCC's Unipol fluidized-bed technology. The product has stron g tensile and impact strength and excellent properties to resist puncture and impact at low temperatures.
Main Applications
LLDPE is mainly used for making film, pipes, injection-molding products, blow-molding containers, rotationally-molding products and wire & cable covering material.

5 Tips For Using Aluminum Foil

posted Feb 4, 2012, 9:50 AM by BENKAI Co

5 Tips For Using Aluminum Foil



Save Brown Sugar

The next time you go for that brown sugar while you're baking and it's a brick, place on a sheet of aluminum foil, preheat the oven to three hundred degrees, cook for five minutes and voila, no more brick, just brown sugar.

Use as a Fabric Softener

The next time you're drying clothes and you've run out of fabric softener, simply use a bit of aluminum foil roll into a ball throw in the dryer and dry normally. the aluminum foil attracts the static that would usually be on your clothes.

Improve Your Ironing

Now we'll use aluminum foil to improve an ironing board. First, remove the cover from the ironing board, place a piece of aluminum foil at the top where you do most of your ironing and replace the cover. The aluminum foil will hold the heat from the iron and help press the clothes from underneath.

Sharpen Scissors

The next time your scissors are getting dull, instead of getting a new pair, take several layers of aluminum foil and cut through them several times. this quickly sharpens the scissors and works on any type of scissors, cheap or expensive.

Make Grilled Cheese

This is my favorite. We're going to use aluminum foil to make a grilled cheese sandwich. First put all the ingredients for the sandwich in some foil, you can use butter or not, and fold the aluminum foil into a pouch. This is fun when you go on trip with kids and stop at hotel rooms because we're going to use an iron to cook the sandwich. We'll make sure the iron is heated up and we're going to cook that on both sides for several minutes until its toasted. Here's what the sandwich looks like when it's done. 

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