Clear BOPS Sheet for Thermoforming Machine Use

Polystyrene Film Rigid Transparent Film

 

Polystyrene film is a kind of rigid transparent film with high tensile strength, as early as in the early 1930s, Germany in order to radar the needs of the polystyrene film stretching carried out careful research, the brittle polystyrene into a strong film material, for people to use. Later on, various countries also put into production one after another and developed rapidly. China started the production of polystyrene film in the early 1960s.

 

Production methodFlat sheet stretching method

AdvantagesExcellent electrical properties

Application: Fresh fruit and vegetable packaging

 

Catalogue

1Introduction

2Characteristics

3Processes

4Applications

 

Polystyrene has many advantages such as high transparency, non-toxicity, easy welding, convenient moulding and processing, low cost, etc. However, its use as film packaging material is limited due to its brittleness until the application of bi-directional stretching technology, which produces bi-directional oriented polystyrene film (BOPS), effectively reduces the brittleness of polystyrene film and makes its film application in packaging possible. But because polystyrene is a non-crystalline polymer, the application of bi-directional stretching technology, polystyrene film performance improvement is far less significant than polypropylene and other crystalline polymers, and the application of bi-directional stretching processing technology, and to a certain extent, weakened polystyrene film in the economic competitiveness, which affects the development of BOPS film.

 

In recent years, as people's awareness of environmental protection, so that BOPS film in competition with PVC film, in a more favourable position (BOPS incineration, does not produce environmentally hazardous substances such as hydrogen chloride, recycling granulation and reuse is also more convenient), BOPS as a new type of plastic packaging materials, there is a certain degree of development. China has also introduced a number of BOPS film, sheet production line, but in terms of application, the main products are still BOPS sheet for thermoforming, BOPS film applications are still to be developed. 

 

Features

 

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

The main use of polystyrene film is to make use of its superior electrical properties, as the defence industry, cutting-edge technology and other aspects of the telecommunications equipment, such as variable capacitors, high-frequency cable insulation. It can also be used as food packaging film, especially suitable for vegetables, fish, meat and other need for breathable conditions.

 

Process

 

The raw material requirement is clean and dry film grade polystyrene resin.

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

 

(1) Flat sheet stretching method

This method of equipment is relatively large, and has the disadvantage of producing waste edge, but the thickness is uniform, stretching times can be freely controlled, conducive to wide, high-speed production.

 

(2) Bubble tube method

This method is characterised by simultaneous stretching, simple equipment, low cost, small footprint, the film produced without waste edges, longitudinal and transverse performance balance is good, but the heating and cooling methods are complex, the film tube is unstable, thickness uniformity is poor.

 

(3) Flat tube one-step stretching method

This method of production technology development of the earliest, mature technology, simple equipment, small footprint, low equipment costs, the shortcomings of the film thickness tolerance is large, generally up to ± 10%.

 

Application Areas

 

1. Fresh fruit and vegetable preservation packaging

It is said that the use of polystyrene film's moderate oxygen permeability, excellent water vapour permeability and anti-fogging properties can improve the storage of fruits and vegetables; at the same time, its high transparency and high gloss, which helps to display the goods and play a good role in promotion. In Japan, polystyrene film has been successfully used for asparagus, spinach, strawberries, tomatoes and flowers and other commodities packaging.

 

2. Processed food packaging

The use of polystyrene film non-toxic, oil-resistant, aroma and easy to heat sealing, high transparency, good printing results and other characteristics, used in processed food packaging has a high degree of security, show good results and other advantages.

 

3. Candy twisted packaging

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

 

In addition, polystyrene can also be used for envelopes and other window packaging window parts of the transparent material, has the advantages of good transparency, easy adhesion; used for clothing and apparel materials such as packaging, has a good display and promotional effect.