Slip Masterbatches & Concentrates
Additives which enhance and reduce handling problems are used extensively in the manufacture of polyolefin films. In their natural state, most polyolefins exhibit a degree of “tackiness” and hence, cannot be readily processed into packaging films without the presence of additives to ease their ability to “separate and slide.”
Slips are used to reduce a film’s resistance to sliding over itself or parts of converting equipment. Commercially important slips are in the chemical family known as amides, and are typically referred to as fast bloom (oleamide) and slow bloom (erucamide). Other amides are used in the case of special processes (e.g. higher heat extrusion coating applications or customized mixtures where balancing slip and antiblock properties).
Effectiveness of slip is normally determined by COEFFICIENT OF FRICTION (COF) COF is a ratio of the force required to slide one layer of film across another, relative to the force exerted on it. Loosely defined, films are considered as low, medium or high slip as follows:
Slip agents are effective when they to “bloom” to the surface of the film after extrusion. Different slip agents have different rates of surface bloom and COF reduction. It does take time for the slip agent to bloom; the ultimate COF may not be obtained until 7-10 days after extrusion (depending on amide used). Typically, the vast majority of COF reduction takes place within 24-48 hours.
In general, the shorter chain length amides bloom to the surface more rapidly but are less thermally stable. Higher chain length amides have a slower rate of bloom with higher thermal stability. While it might initially seem that a faster bloom rate always offers advantages, many film processors would prefer a slower rate of migration, particularly in roll stock, where a low COF film could cause winding difficulties and “telescoping” of rolls. A slower rate of bloom result in easier film treatment (e.g. corona treating immediately after extruding the film). Excessively high amounts of any slip agent make corona treatment very difficult and may cause buildup on the producer’s equipment.
Non-Migratory “Permanent” Slip
As their name implies, Ampacet’s Non–Migratory Permanent Slips are designed to stay where you put them. This ability gives them some very unique advantages over conventional “blooming” slips such as:
- They are useful in multilayer films, which require slip properties on one side only.
- They can be used in the skin layer only (not needed in the core layer).
- There is no adverse effect on heat sealing.
- The COF does not change over time.
- They may be FDA approved at all levels.
- They can be used for high temperature applications.
- A low COF is achieved as soon as the film is made–no conditioning period involved.
- A COF as low as 0.25 may be achieved.
- There is less interference with printing.
- There is effective mold release for blow molded bottles, without affecting label adhesion.
The high loading requirements and economics of permanent slips as compared to conventional “blooming” slips make them undesirable for monolayer applications.
Ampacet makes a broad variety of slip concentrates designed to fit various needs, in terms of bloom rate as well as base resin requirements. Slip concentrates are available in a variety of polyolefins making them more compatible with polypropylene and other resins.
To learn what Ampacet Slip Masterbatch would fit best in your process, please complete the product inquiry form or contact your local Ampacet representative.