Retort bags are made of multi-layer thin film materials, which are dried or co extruded to form a certain size bag. The composition materials can be divided into 9 types, and the retort bag made must be able to withstand high temperature and damp heat sterilization. Its structural design should also meet the requirements of good heat sealing, heat resistance, water resistance, high strength, and high barrier performance.
1. PET film
BOPET film is made by extruding PET resin through T film and biaxially stretching, which has excellent properties.
(1) Good mechanical performance. The tensile strength of BOPET film is the highest among all plastic films, and extremely thin products can meet the needs, with strong rigidity and high hardness.
(2) Excellent cold and heat resistance. The applicable temperature range of BOPET film is from 70 to 150 ℃, maintaining excellent physical properties over a wide temperature range, making it suitable for the vast majority of product packaging.
(3) Excellent barrier performance. It has excellent comprehensive water and gas resistance performance, unlike nylon, which is greatly affected by humidity. Its water resistance rate is similar to PE, and its permeability coefficient is very small. It has a high barrier to air and odor, and is one of the fragrance retaining materials.
(4) Chemical resistance, oil resistance, as well as most solvents, dilute acids, dilute alkalis, etc.
2. BOPA film
BOPA film is a biaxial stretching film, which can be obtained by blowing and biaxial stretching simultaneously. The film can also be gradually biaxially stretched using the T-mold extrusion method, or simultaneously biaxially stretched using the blow molding method. The characteristics of BOPA film are as follows:
(1) Excellent toughness. The tensile strength, tear strength, impact strength, and rupture strength of BOPA film are all among the best among plastic materials.
(2) Outstanding flexibility, needle hole resistance, and difficulty in puncturing the contents are a major feature of BOPA, with good flexibility and a good packaging feel.
(3) Good barrier properties, good aroma retention, excellent resistance to chemicals other than strong acids, especially oil resistance.
(4) The temperature range is wide, with a melting point of 225 ℃, and can be used for a long time between -60~130 ℃. The mechanical properties of BOPA remain stable at low and high temperatures.
(5) The performance of BOPA film is greatly affected by humidity, especially in terms of dimensional stability and barrier properties. After being damp, BOPA film generally elongates laterally, except for wrinkling. Longitudinal shortening, with a maximum elongation of 1%.
3. CPP film
CPP film, also known as cast polypropylene film, is a non stretching, non oriented polypropylene film. Divided into homopolymer CPP and copolymer CPP according to raw materials. The main raw material for cooking grade CPP film is block copolymer impact resistant polypropylene. The performance requirements are: the softening point temperature of Vicat should be higher than the cooking temperature, the impact resistance should be better, the medium resistance should be better, and the fish eye and crystal point should be as few as possible.
4. Aluminum foil
Aluminum foil is the only type of metal foil in soft packaging materials, used for packaging items with a long application time. Aluminum foil is a metal material with unparalleled water resistance, gas resistance, light shielding, and flavor retention properties compared to any other packaging material. It is a packaging material that cannot be completely replaced to this day.
5. Ceramic evaporation coating
Ceramic vapor coating is a new type of packaging film, which is obtained by vaporizing metal oxides on the surface of plastic film or paper as the substrate in high vacuum equipment. The characteristics of ceramic vapor coating mainly include:
(1) Excellent barrier performance, almost comparable to aluminum foil composite materials.
(2) Good transparency, microwave permeability, high temperature resistance, suitable for microwave food.
(3) Good fragrance retention. The effect is similar to glass packaging, and it will not produce any odor after long-term storage or high-temperature treatment.
(4) Good environmental friendliness. Low combustion heat and less residue after incineration.
6. Other thin films
(1) PEN film
The structure of PEN is similar to PET, and it has various properties of PET, and almost all of its properties are higher than PET. Excellent comprehensive performance, high strength, good heat resistance, good barrier performance, and transparency. The outstanding UV resistance is the biggest highlight of PEN. PEN's barrier to water vapor is 3.5 times that of PET, and its barrier to various gases is four times that of PET.
(2) BOPI film
BOPI has an extremely wide temperature range, ranging from -269 to 400 ℃. The film that has completed the reaction has no melting point, and the glass transition temperature is between 360 to 410 ℃. It can be continuously used in air at 250 ℃ for more than 15 years without significant performance changes. BOPI has excellent comprehensive performance, high physical and mechanical properties, radiation resistance, chemical solvent resistance, dimensional stability, and flexibility and folding resistance.
(3) PBT film
PBT film is one of the thermoplastic polyester films, namely butylene terephthalate film. Density is 1.31-1.34g/cm ³， The melting point is 225~228 ℃, and the glass transition temperature is 22~25 ℃. PBT film has superior properties compared to PET film. PBT has excellent heat resistance, oil resistance, aroma retention, and heat sealing properties, making it suitable for packaging bags used in the production of microwave food. PBT film has good barrier properties and can be used for packaging flavored food. PBT film has excellent chemical resistance.
(4) TPX film
TPX film is formed by copolymerization of 4-methylpentene-1 with a small amount of 2-olefin (3%~5%), and is the lightest plastic with a specific gravity of only 0.83g/cm ³， Other performance is also very excellent. In addition, TPX has good heat resistance and is the most heat-resistant material among polyolefins. It has a crystallization melting point of 235 ℃, good mechanical properties, high tensile modulus and low elongation, strong chemical resistance, oil resistance, high resistance to acid, alkali, and water, and resistance to most hydrocarbons. It can withstand solvent temperatures up to 60 ℃, surpassing all other transparent plastics. It has high transparency and a transmittance of 98%. Its appearance is crystal clear, decorative, and has strong microwave penetration.
If you have any retort pouch requirements, you can contact us. As a flexible packaging manufacturer for over 20 years, we will provide your right packaging solutions according to your product needs and budget.
Post time: Nov-04-2023
