What Are Polystyrene Sheets?

Polystyrene film is a rigid transparent film with very high tensile strength. As early as the early 1930s, in order to meet the needs of radars, Germany conducted a careful study on the stretching of polystyrene films. Polystyrene is used to make strong film materials. Later countries have also put into production one after another and developed rapidly. China started the production of polystyrene films in the early 1960s.

Polystyrene has many advantages such as high transparency, non-toxicity, easy welding, convenient molding and processing, and low cost. However, its use as a film packaging material is limited due to its brittleness. Until the application of biaxial stretching technology, The biaxially stretched polystyrene film (BOPS) effectively reduced the brittleness of the polystyrene film and made its application in packaging possible. However, because polystyrene is an amorphous polymer, the application of biaxial stretching technology has greatly improved the performance of polystyrene films compared to crystalline polymers such as polypropylene, and the application of biaxial stretching processing technology. To a certain extent, it has weakened the economic competitiveness of polystyrene films, which has affected the development of BOPS films.

In recent years, with the improvement of people's awareness of environmental protection, BOPS films have been in a more advantageous position in the competition with PVC films. BOPS, as a new type of plastic packaging material, has made some progress. China has also introduced a number of BOPS film and sheet production lines, but from the application point of view, the main product is still BOPS sheet for thermoforming, and the application of BOPS film has yet to be developed. ^[1]

The biggest feature of polystyrene film is that it has excellent electrical properties. The dielectric constant is 2.4 2.7, and it is basically independent of frequency. The dielectric loss tangent value is 5 × 10 ^-4 , which is the smallest of the existing plastic films. It has a dielectric strength of 50 kV / mm and is particularly suitable as a high-frequency insulating material. The water resistance of polystyrene film is very outstanding. Its water absorption is 1/2 of that of PVC film, 1/5 of PET film, and 1% of cellulose triacetate film.

The main purpose of polystyrene film is to use its superior electrical properties as telecommunications equipment in the defense industry and cutting-edge technology, such as

Raw materials require clean and dry film-grade polystyrene resin.

There are several production processes for this product, namely flat sheet stretching method, bubble tube method and flat tube one-step stretching method. The characteristics of each method are as follows.

(1) Flat sheet stretching method

The equipment of this method is relatively large and has the disadvantage of generating waste edges, but the thickness is uniform and the stretching ratio can be freely controlled, which is conducive to wide and high-speed production.

(2) Foam tube method

This method is characterized by simultaneous stretching, simple equipment, low cost, small footprint, produced film without waste edges, good horizontal and vertical performance balance, but complicated heating and cooling methods, unstable film tubes, and uniform thickness Poor sex.

(3) Flat tube one-step stretching method

This method has the earliest development of production technology, mature technology, simple equipment, small footprint, and low equipment costs. The disadvantage is that the film thickness tolerance is large, generally reaching ± 10%. ^[2]

1. Fresh-keeping packaging for fresh fruits and vegetables

It is said that the use of polystyrene film's moderate oxygen permeability, excellent water vapor permeability and anti-fogging properties can improve the storage effect of fruits and vegetables; meanwhile, its high transparency and gloss can help display goods, To good promotional effect. In Japan, polystyrene films have been successfully used in the packaging of asparagus, spinach, strawberry, tomato and flowers.

2.Processed food packaging

The use of polystyrene film is non-toxic, oil-resistant, fragrant, and easy to heat seal, high transparency, good printing effect and other characteristics, used in processed food packaging has high safety, good display effect and other advantages.

3.Kink packaging

Polystyrene film has good kink performance, is not easy to rebound, non-toxic and tasteless, high gloss, high transparency, good printing effect, and is considered to be one of the most ideal materials for candy single kink packaging.

In addition, polystyrene can also be used as a transparent material for window opening parts of envelopes and other window packaging. Promotion effect. ^[3]