BOPP film is a very important flexible packaging material and is widely used. BOPP is colorless, odorless, tasteless, non-toxic, and has high tensile strength, impact strength, rigidity, toughness, and good transparency. BOPP film has low surface energy and needs corona treatment before gluing or printing. However, after corona treatment, BOPP film has good printing adaptability, and can be printed with color to obtain exquisite appearance effect, so it is often used as the surface material of composite film.

BOPP film also has shortcomings, such as the tendency to generate static electricity on high-speed production lines, and it is necessary to install an electrostatic eliminator. The film is widely used in the packaging of bread, clothes, shoes and socks, as well as the cover packaging of cigarettes and books. The initiation tear strength of BOPP film is improved after stretching, but the secondary tear strength is very low, therefore, there can be no incision left on both ends of BOPP film, otherwise BOPP film is easy to tear when printing and laminating. BOPP can produce sealing tape after coating self-adhesive, which is a market with a large amount of BOPP.

BOPP films can be produced by either the tube film method or the flat film method. The performance of BOPP film obtained by different processing methods is also different. Due to the large tensile ratio (up to 8-10), the BOPP film produced by the flat film method has higher strength than the tube film method, and the uniformity of the film thickness is also better.

BOPP Definition

Biaxially oriented polypropylene film (referred to as BOPP film) is a new type of excellent transparent flexible packaging material. It is a crystalline polymer product, after bidirectional stretching, due to the action of molecular chains, the crystallinity increases, thereby significantly improving the tensile strength, elastic modulus, impact strength, tear strength and flexural strength and other properties with good transparency, gloss, moisture resistance, but also has the advantages of light texture and relatively low price. BOPP film is suitable for all kinds of packaging, printing, laminating, aluminization, etc.

BOPP classification

1. According to the use, it can be divided into:

Ordinary type: also known as light film, flat film. It is used for printing, lamination (transparent type, matte type), coating (adhesive tape and PVDC coated film base film). It is the most versatile and highest-yield variety of film products;

Heat sealing type: used for ordinary packaging, such as cigarette packaging film, three-layer heat sealing film, five-layer air blocking film, pearlescent film, coated heat sealing film, etc.;

Label film: used for commodity labeling, advertising printing, books and magazines, bottle labels and overall packaging, etc.;

Metallized film: for vacuum aluminization;

Capacitor film: used for capacitors and metal capacitors

2. Membrane type subdivision:

Ordinary film: BOPP ordinary film, also known as light film, is suitable for food packaging, paper lamination and printing composite of general packaging, and is the largest product in BOPP products. Flat film, also known as light film, is one of the most common films in biaxially oriented polypropylene film (BOPP film) series products, which is widely used in various printing and composite products for the packaging of various foods and articles. Among them, the 15um thickness flat film is mainly used for the lamination of books and other papers.

Cigarette film: Although the overall use of cigarette film is not large, it is the most profitable product in BOPP film. The characteristics of cigarette film production and sales are high technical requirements and large entry costs.

Matting (matte) film: matting film is a kind of plastic matting product with low gloss (gloss less than 15) high haze into diffuse reflection matting effect, which has the characteristics of paper-like appearance, realistic color reproduction during printing and comfortable feel. Matting film is a film made of biaxially stretched matting masterbatch on a single surface layer.

Heat sealing film: heat sealing film is divided into single-sided heat sealing film and two-way heat sealing film, which is a polypropylene heat sealing film (BOPP heat sealing film) made by bidirectional stretching using heat sealing masterbatch on the surface, which is mainly used in the heat sealing packaging of food, medicine and other electrical components.

Pearlescent film: white opaque BOPP pearlescent film has a satin-like texture, soft and pleasing pearl luster, low density, excellent flatness, gas barrier, can be widely used in dried fruits, ice cream, candy, high-grade soap gifts and other direct packaging, at the same time it is also a good printing base lining, in the surface printing can not be carried out full plate priming, therefore, BOPP pearlescent film is favored, compared with ordinary BOPP film, BOPP pearlescent film has three typical characteristics: emitting pearl luster, Good shading, especially for UV light blocking) and low density. In particular, the first two characteristics show that BOPP pearlescent film is extraordinary, making it enter the high-end market in the field of packaging and bring considerable economic benefits to manufacturers.

Transfer film: In recent years, a few BOPP manufacturing enterprises have successfully developed BOPP transfer film to replace PET transfer film, because BOPP transfer film is cheaper than PET, and there is no need to coat isolation materials in the use process, saving a process and corresponding materials, the gold and silver cardboard made of gold and silver cardboard made of PET film as transfer film is consistent in brightness, so a large number of PET transfer film is replaced by BOPP film transfer film, and the market space is very large.

BOPA film

BOPA film is biaxially oriented nylon film, which is an important surface material for the production of various vacuum packaging and other composite packaging materials. In order to ensure that the nylon film has good barrier property and prevent nylon from absorbing moisture due to strong hydrophilicity, resulting in reduced barrier resistance, when using, a multi-layer composite process is usually used, and the BOPA film is placed in the middle layer of the composite film as a barrier layer.

BOPA film is made from polyamide 6 (nylon 6) as a raw material. The polyamide molecule contains a polar amide group (-CO-NH-), in which the -NH-group can form a hydrogen bond with the -C=O group, and the formation of hydrogen bond is one of the important factors for polyamide to have high crystallinity, but not all the molecules in polyamide can be crystallized, and there is also a part of amorphous polyamide with movable type printing, and the amide group in this part of the amorphous polyamide molecular chain can be coordinated with water molecules, that is, it has water absorption. It has been proposed that every 2 amide groups in the polyamide 6 molecule can be coordinated with 3 water molecules, of which 1 water molecule exists in a strong hydrogen bond, and the other 2 water molecules exist in a loosely bound state. Water penetrates into the nylon to weaken the existing bonds for sticker printing, It is precisely because of these characteristics of its molecular structure that polyamide 6 has the following characteristics: excellent mechanical properties, wear resistance and corrosion resistance; Self-lubricating; High temperature resistance; It has good oxygen barrier, puncture and tear resistance; The disadvantage is that it is highly absorbent.

BOPA film is a colorless, odorless, tasteless and non-toxic packaging material with excellent transparency, with good strength and barrier, and can be used for vacuum packaging of sausages and other foods; It has good high and low temperature resistance, and the service temperature is between -60 °C and 150-200 °C; In addition, BOPA film also has excellent oil resistance, organic solvent resistance, alkali resistance, chemical resistance, etc.; At the same time, BOPA film is not easy to generate static electricity, does not absorb dust, and has excellent vacuum printability, easy to vacuum aluminum. Cast nylon sheets have good elongation and can be used for vacuum thermoforming.

Nylon film is a very easy to absorb moisture coated paper printing, after moisture absorption will have an adverse effect on the use, such as size changes lead to inaccurate overprinting during printing, surface water film leads to insufficient composite strength, blistering, etc., so in the high humidity environment to do a good job of moisture-proof protection of nylon film.

Specifically, we should pay attention to the following aspects:

(1) Do not open the package too early before use.

(2) Try to use it all at once, and wrap the remaining residual film with a good barrier material.

(3) When printing, the first color group is not printed on the plate roller, and it is pre-dried.

(4) Put it in the maturation room to dry for 2-3 hours before use.

(5) Ensure reasonable temperature (25°C±2°C) and humidity (≤85%RH) in the production workshop.

Due to the strong hydrophilicity of nylon film, the moisture resistance of nylon film used alone is poor, and the barrier property will decrease after moisture absorption, therefore, once the BOPA film is produced, it should be tightly sealed with aluminum immediately to prevent it from absorbing moisture. When using, the whole roll of film should also be used up at one time, if it has to be used up, it should be stored in a dry place after being tightly wrapped with aluminum. As for the nylon film that has absorbed moisture, it needs to be re-dried before printing and laminating, otherwise there will be failures such as glue leakage and print leakage.

Functional BOPA film, i.e., biaxially oriented nylon film, is a kind of functional film with good comprehensive performance produced based on biaxially oriented process technology. Functional BOPA film is mainly used to form flexible packaging materials by compounding with other general materials (PET, PP, PE, etc.). Functional BOPA films can be divided into general-purpose BOPA films and new BOPA films.

General-purpose BOPA film refers to a functional film product produced by using polyamide 6 chips as raw materials, melting and extruding castings by special equipment, and then through biaxially oriented process. Compared with other functional BOPA films such as BOPP and BOPET, general-purpose BOPA films have outstanding performance in terms of physical properties, chemical properties and environmental performance, with excellent barrier, puncture resistance, stretch resistance and can take into account the aesthetics of the product at the same time, and have a wide range of applications in the fields of medium and high-end food and beverage flexible packaging, pharmaceutical packaging, and daily chemical packaging, and can fully meet the needs of fresh food, ready-to-eat food, prefabricated dishes, pet food and other emerging food fields. It is easy to tear and other needs, and has a good market prospect in the trend of China's consumption upgrading.