Analysis of common materials for retort pouches, helping you create high-quality packaging bags

Retort pouches are made of multi-layer film materials, formed into packaging bags of a certain size through dry lamination or co-extrusion lamination. The constituent materials are usually divided into 9 categories. The manufactured retort pouches must withstand high-temperature sterilization, and their structural design should also meet the requirements of good heat sealing, heat resistance, water resistance, high strength, and high barrier performance.

Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will analyze the materials used for retort pouches.

1、 PET Film

BOPET film is made by biaxially stretching PET resin after T-die extrusion, and it has excellent properties.

Good mechanical properties. BOPET film has the highest tensile strength among all plastic films; even very thin products can meet the requirements, with high rigidity and hardness.

Cold and heat resistant. The applicable temperature range of BOPET film is 70~150℃, maintaining excellent physical properties within a wide temperature range, suitable for most product packaging.

Excellent barrier properties. It has excellent comprehensive water and gas barrier properties. Unlike nylon, which is greatly affected by humidity, its water resistance is similar to PE, and the permeability coefficient is extremely small. It has extremely high barrier properties against air and odors, and is one of the aroma-preserving materials.

Resistant to chemicals, oils, and greases, as well as most solvents, dilute acids, and dilute alkalis.

2、 BOPA Film

BOPA film is a biaxially oriented film that can be produced by simultaneous biaxial stretching using a blown film method. It can also be produced by a T-die extrusion method for step-by-step biaxial stretching. The characteristics of BOPA film are as follows:

Excellent toughness. The tensile strength, tear strength, impact strength, and burst strength of BOPA film are among the best in plastic materials.

Outstanding flexibility and puncture resistance; it is not easily pierced by the contents. This is a major characteristic of BOPA; its good flexibility also results in a good packaging feel.

Good barrier properties and aroma retention; resistant to chemicals except strong acids, especially excellent oil resistance.

Wide operating temperature range; the melting point reaches 225℃, and it can be used continuously between -60~130℃. The mechanical properties of BOPA remain stable at both low and high temperatures.

The performance of BOPA film is greatly affected by humidity, especially dimensional stability and barrier properties. After BOPA film absorbs moisture, in addition to wrinkling, it generally elongates laterally and shortens longitudinally, with a maximum elongation rate of up to 1%.

3、 CPP Film

CPP film, or cast polypropylene film, is an unstretched, non-oriented polypropylene film. According to the raw materials, it is divided into homopolymer CPP and copolymer CPP. The main raw material for retort-grade CPP film is block copolymer impact-resistant polypropylene. Its performance requirements are: Vicat softening point temperature must be greater than the retort temperature, impact resistance must be good, medium resistance must be good, and fish eyes and crystal points should be as few as possible.

4、 Aluminum Foil

Aluminum foil is the only metal foil type among flexible packaging materials and is used for packaging items with long usage times. Aluminum foil is a metal material, and its water resistance, gas resistance, light shielding, and flavor retention are unmatched by any other packaging material. It is a packaging material that has not yet been completely replaced.

5、 Ceramic Vapor-Deposited Film

Ceramic vapor-deposited film is a new type of packaging film. It uses plastic film or paper as a substrate, and metal oxide is vaporized and deposited on the surface of the substrate in a high-vacuum device to obtain the film. The characteristics of ceramic vapor-deposited film are mainly:

Excellent barrier properties, almost comparable to aluminum foil composite materials.

Good transparency and microwave permeability, high temperature resistance, suitable for microwave food.

Good aroma retention. The effect is the same as glass packaging; no peculiar smell will be produced after long-term storage or high-temperature processing.

Good environmental protection. Low combustion heat and little residue after incineration.

6、 Other Films

PEN Film

The structure of PEN is similar to that of PET. PEN has various properties of PET, and almost all properties are higher than PET. It has excellent comprehensive performance, high strength, good heat resistance, good barrier properties, and transparency. The outstanding UV barrier property is the biggest highlight of PEN. The water vapor barrier property of PEN is 3.5 times that of PET, and the barrier property against various gases is four times that of PET.

BOPI Film

BOPI has an extremely wide operating temperature range, reaching -269~400℃. The completed film has no melting point, and the glass transition temperature is between 360~410℃. It can be used continuously at 250℃ in air for more than 15 years with little change in performance. BOPI has extremely excellent comprehensive performance, high physical and mechanical properties, radiation resistance, chemical solvent resistance, dimensional stability, and softness and fold resistance.

PBT Film

PBT film is one of the thermoplastic polyester films, namely, butylene terephthalate film. The density is 1.31~1.34g/cm³, the melting point is 225~228℃, and the glass transition temperature is 22~25℃. PBT film has better properties than PET film. PBT has excellent heat resistance, oil resistance, aroma retention, and heat sealing properties, and is suitable for producing packaging bags for microwave food. PBT film has good barrier properties and can be used to package fragrant foods. PBT film has excellent chemical resistance.

TPX Film

TPX film is a copolymer of 4-methyl-1-pentene and a small amount of 2-olefins (3%~5%), and it is the lightest of all plastics, with a density of only 0.83g/cm³. It also boasts other excellent properties. In addition, TPX has good heat resistance, the best among polyolefins, with a crystalline melting point of 235℃. It has good mechanical properties, high tensile modulus and low elongation, strong chemical resistance, oil resistance, high resistance to acids, alkalis, and water, resistance to most hydrocarbons, and solvent resistance up to 60℃, exceeding all other transparent plastics. It has high transparency, with a light transmittance of 98%, a crystal-clear appearance, and strong decorative properties. It also has strong microwave permeability.