Summary of 11 plastic film properties

Casting method: A non-stretched, non-oriented flat extruded film is produced by a melt flow quenching process. The film produced by this process does not have a distinct orientation structure.

Extrusion method: Common ones are uniaxial stretching and biaxial stretching. The basic principle of biaxial stretching: the high polymer raw material is first heated and melted into a thick sheet by an extruder, and then carried out in the longitudinal and transverse directions by a stretching machine in an appropriate temperature range above the glass transition temperature and below the melting point. Stretching a certain number of times, the molecular chains are oriented and arranged in an order parallel to the plane of the film, and then heat-set in a tensioned state to fix the oriented macromolecular structure, and finally form a film by cooling and subsequent treatment. .

Blow molding method: usually produced by extrusion blow molding, plasticizing and extruding materials, forming tube blank inflation molding, and then cooling, drawing and coiling. The blown film is oriented. The blow molding process is simple and is the most commonly used film forming process.

11 film properties:

PVC

PVC film and PET have similar advantages. They are transparent, airtight and acid-resistant. In the early days, many mineral waters were packaged in PVC bottles. However, because PVC may release carcinogens due to incomplete polymerization of some monomers, PVC is not suitable for filling food-grade substances. Now it has been changed to PET bottles, and the label material is No. 3. Recycled materials can be re-made: water pipe elbows, artificial leather, wire covering, fireproof building materials, etc.

PS

The PS film has low water absorption, but its dimensional stability is good, and it can be processed by injection molding, compression molding, extrusion, and thermoforming. Generally, it is classified into foamed and unfoamed according to whether it is subjected to a foaming process. Unfoamed PS is mainly used in building materials, toys, stationery, etc. It can also be made into containers filled with fermented dairy products (such as Yakult, health, and many other dairy products or lactic acid products). Tableware, marked material symbol is No. 6. Recycled materials can be re-made: you can take hard, fragile, non-elastic plastic re-products such as camera casings and hangers.

PP

Ordinary PP film is blow molded, which is simple in process and low in cost, but its optical performance is slightly lower than CPP and BOPP. PP is characterized by high temperature resistance (about -20 ° C ~ 120 ° C), and melting point of up to 167 ° C, suitable for filling soy milk, rice pulp and other products that require steam sterilization. Its hardness is higher than that of PE. It is used to make container caps. The symbol of the material is No. 5. Identification method: Generally speaking, PP has a high hardness and a shiny surface, which does not produce a pungent odor when burned, while PE has a heavier candle smell.

PET

Polyester film (PET) is a thermoplastic engineering plastic. A film material which is formed into a thick sheet by extrusion and then biaxially stretched. Polyester film is characterized by excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high and low temperature resistance, chemical resistance, oil resistance, air tightness and good aroma retention. It is a commonly used barrier property. One of the composite film substrates, but with poor corona resistance and high price. The thickness of the film is generally 0.12 mm, and the outer layer material of the food packaging which is commonly used for packaging has good printability. Mark the material symbol in the plastic product as No. 1. Its recycled materials can be re-made: monofilament → wig, zipper serrated; sheet → packaging box (egg box, stationery L clip); polyester cotton → filled cotton, non-woven fabric, polyester fabric.

PA

Nylon plastic film (polyamide PA) is currently produced in a variety of industrial products, of which the main varieties used to produce film are nylon 6, nylon 12, nylon 66 and so on. Nylon film is a very tough film with good transparency and good gloss. Tensile strength, tensile strength, high and low temperature resistance, oil resistance, organic solvent resistance, abrasion resistance and puncture resistance are good, and the film is soft and excellent in oxygen barrier, but the barrier to water vapor is better. Poor, moisture absorption, moisture permeability, heat sealability is poor. Suitable for packaging hard items such as greasy foods, fried foods, vacuum packed foods, cooked foods, etc.

HDPE

The HDPE film is called a geomembrane or a barrier film. Its melting point is about 110 ° C -130 ° C, the relative density of 0.918-0.965 kg / cm3. It is a kind of thermoplastic resin with high crystallinity and non-polarity. The original HDPE has a milky white appearance and a semi-transparent shape in a slight cross section. It has good resistance to high and low temperature and impact resistance, even at low temperatures of -40F. Its chemical stability, rigidity, toughness, mechanical strength and tear strength are excellent, and as the density increases, mechanical properties, barrier properties, tensile strength and heat resistance will increase accordingly, and it can withstand acid and alkali. Corrosion by organic solvents, etc. Identification method: Most of them are opaque, feel like wax, and there is rustling when the plastic bag is rubbed or rubbed.

LDPE

LDPE film has low density, softness, low temperature resistance and impact resistance. It has good chemical stability. Under normal circumstances, it is resistant to acid (except strong oxidizing acid), alkali and salt corrosion, and has good electrical insulation. Most of LDPE is used in plastic bags, and the material symbol is - No. 4. Its products are mostly used in civil engineering and agricultural fields, such as geomembrane, agricultural film (shed film, plastic film, green film, etc.). Its recycled materials, trims, etc. can be made into elastic plastic re-products such as trash cans, tool boxes, bicycle mats, and garbage trucks. Identification method: The plastic bag made of LDPE is softer, and it will not emit rustling when it is smashed. The outer packaging plastic film is soft and easy to tear is LDPE, and the brittle and hard is PVC or PP film.

PVA

The polyvinyl alcohol (PVA) high barrier composite film is a film having a very high barrier property formed by coating a modified polyvinyl alcohol water-soluble liquid on a substrate on a polyethylene plastic substrate. Since the polyvinyl alcohol high barrier composite film has good barrier properties and meets environmental protection requirements, the market prospect of the packaging material is very bright, and there is a broad market space in the food industry.

CPP

Cast polypropylene film (CPP) is a non-stretched, non-oriented, extruded film produced by melt casting and quenching. It is characterized by high production speed, high output, good transparency, gloss, barrier, softness and uniformity of thickness. It can withstand high temperature cooking (cooking temperature above 120 °C) and low temperature heat sealing (heat sealing temperature is less than 125 ° C), excellent performance balance. Subsequent work such as printing and compounding is widely used in the packaging of textiles, foods and daily necessities, and the inner layer substrate of composite packaging can prolong the shelf life of food and increase the aesthetics.

BOPP

Biaxially oriented polypropylene film (BOPP) is a transparent flexible packaging material developed in the 1960s. It is a special production line that mixes, melts and kneads polypropylene raw materials and functional additives into sheets, and then pulls them. Stretched into a film. The film not only has the advantages of low density, corrosion resistance and heat resistance of the PP resin, but also has good optical properties, high mechanical strength, rich raw material sources, excellent printing performance, and can be used with paper, PET and Other substrates are compounded with high definition and gloss, excellent ink absorption and coating adhesion, high tensile strength, excellent grease barrier properties, low electrostatic properties, and the like. It is widely used in the field of printing and compounding, and as a packaging material in tobacco and other aspects.

Aluminized

The aluminized film combines the properties of a plastic film and metal. The surface of the film is coated with aluminum to prevent light and ultraviolet radiation, which not only prolongs the shelf life of the content, but also improves the brightness of the film. It replaces the aluminum foil to a certain extent, and has the advantages of low cost, good appearance and good barrier property. Therefore, the application of aluminized film in composite packaging is very extensive, mainly used in drying, puffed food packaging, medicine and cosmetic packaging of biscuits.