From Wikipedia, the free encyclopedia
boxes being stretch wrapped
Stretch wrap or stretch film is a highly stretchable
that is wrapped around items. The elastic recovery keeps the items tightly bound. In contrast,
is applied loosely around an item and shrinks tightly with heat.
It is frequently used to unitize pallet loads but also may be used for bundling smaller items. Types of stretch film include bundling stretch film, hand stretch film, extended core stretch film, machine stretch film and static dissipative film.
The most common stretch wrap material
or LLDPE, which is produced by
with s, the most common of which are ,
and . The use of higher alpha-olefins (hexene or octene) gives rise to enhanced stretch film characteristics, particularly in respect of elongation at break and . Other types of
can also be used. Many films have about 500% stretch at break but are only stretched to about 100 – 300% in use. Once stretched, the elastic recovery is used to keep the load tight.
There are two methods of producing stretch wrap. 1) Blown: the resin is melted and extruded through an annular die, it is air-cooled. This is a slower process but provides for higher quality in all the areas listed below. The cost of production is also higher due to the quantity that can be produced per hour. 2) Cast: the film is extruded through a slot die, then passed over cooling rollers. This makes the cooling process quick. The quality is not as good as blown but more can be produced in an hour with lower costs.
Other properties such as break strength, cling, clarity, tear resistance, , etc. are also important.
unitizing, stretch wrap can have several functions:
improved stability of products or packages, forming a
more efficient handling and storage of unit loads
some degree of dust and moisture protection
some degree of
and resistance to
some degree of sun protection (UV stretch wraps)
of certain foods
Making sure boxes stay on the pallet and properly aligned is an important consideration in warehouse distribution, especially as the demands for increased throughput continues to rise.
Typical fully automatic
Categories and sub-categories of stretch wrappers:
Manual (or Hand) Wrappers:
: An extension of the film's core serves as a this type of wrapper offers little stretch control and is hard on hands.
: A simple structure supports a film roll and a mechanical brake system provides resistance creating stretch of the film.
Pole wrappers: Similar to the mechanical brake system, but the roll and brake are at the end of an extended pole, creating an ergonomic design which eliminates the need to bend to wrap the bottoms of loads and strain to reach the tops of loads. Used for space missions too.
Semi-Automatic Wrappers:
: The load to be wrapped sits on a turntable which spins the load relative to the film roll, which is housed in a carriage which can move up and down a fixed "mast". Stretch is achieved by rotating the load at a faster rate than the film is fed.
: The film is housed in a carriage on a vertical ring, the load is fed horizontally through the eye of the rotating ring, applying film to the load. A variation of an orbital stretch wrapper is a horizontal ring system, in which the load remains still while a horizontal ring is rotated around the load and moves up and down vertically relative to the load, similar to a rotary arm stretch wrapper.
Rotary arm wrappers: In this system, the load remains still while a rotating arm turns around it wrapping the load. This system is used for light loads or for speeds which would otherwise cause the load to topple due to high rotation speeds.
Typical fully automatic
Automatic Wrappers:
Typical fully automatic rotary ring stretch wrappers
Automatic wrappers are generally a variant of a semi-automatic system. Automatic wrappers include a conveyor system to automatically load the wrapping machine and automatic systems to apply, seal, and cut the film.
: The load to be wrapped sits on a turntable which spins the load relative to the film roll, which is housed in a carriage which can move up and down a fixed "mast". Stretch is achieved by rotating the load at a faster rate than the film is fed.
Rotary arm wrappers: In this system, the load remains still while a rotating arm turns around it wrapping the load. This system is used for light loads or for speeds which would otherwise cause the load to topple due to high rotation speeds.
Rotary ring wrappers: The film is housed in a carriage on an horizontal ring in which the load remains static while the horizontal ring is rotating around the load and moves up and down vertically relative to the load, similar to a rotary arm stretch wrapper. The rotary ring technology is really a more balanced system with less wear and maintenance than the other available wrapping technologies. These wrappers are capable to reach the highest production capacities (up to 160 pallets/hour).
Wikimedia Commons has media related to .
Dahll, R K; Sharma (August 2012). . Journal of Food Science and Technology. 49 (4): 495–499 2017.
, Guard, "Film Wrapping Dispenser P Silbernagel - US Patent 4,723,393, 1988 -", published 1978
, Parry, "APPARATUS FOR APPLICATIONOF PLASTICS STRETCH FILMS", published 1979
D4649 Guide for Selection and Use of Stretch Wrap Films
Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009,  
: Hidden categories:楼主邀你扫码
参与上面帖子讨论
发表于：03-12-03 23:51
脸能小吗???
是不是要按摩很长时间?
　我是一条鱼　妈妈总说我丢三拉四　
　不是忘了这个就是忘了那个　
　哎。。。。。我也没办法　
发表于：03-12-04 00:18
恩,我买过索肤特的,按摩半天呢!
　　你　　
　　一会看我　　
　　一会看云　　
　　我觉得　　
　　你看我时很远　　
　　你看云时很近　 　
发表于：03-12-04 00:33
不是说脸可以变的很小拉
其实要变的那样除非是去整容在可以变的那么明显''
纤容霜的工效是紧实面部肌肤从而使脸部的线条变的明显
比如说因为发胖而皮肤变松出现的双下巴
就可以通过纤容霜收紧,逐渐看不出来
发表于：03-12-04 11:53
奥,是减去赘肉,或是应该叫紧实皮肤
发表于：03-12-04 12:54
哈哈，摸起来舒服
楼上的，让我摸一下　 ：）
　~~　　　　　　　　　　　　　　　　　　　 ~　　　　　　　　　　　　
　 ~~~....　　　　　　　　　　　　　　　　 ~~~~~ ...　
　........　~~~~~~~　　　　　　~~~~~~　.........　
　..............大漠苍烟起，孤狼仰天啸...........　
　..............一骑绝尘去，伊人在何方...........　
　　　　　　　　　　清风轩 轩主　
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