Characteristics of common vacuum packaging bags
Vacuum bags are not produced from a single raw material and are produced in several composites. The following are the common raw materials for vacuum packaging bags, which are used by vacuum packaging machine manufacturers when purchasing vacuum packaging bags.
Manufacturing process: blown film method, casting method
Features: odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -70 ~ -100 °C), good chemical stability, can withstand most acid and alkali corrosion (not resistant to oxidizing properties) The acid is insoluble in common solvents at normal temperature, has low water absorption and excellent electrical insulation properties. In general, as the density increases, mechanical properties and barrier properties increase, and heat resistance is also good. PE type:
LDPE: low density polyethylene, high pressure polyethylene
LLDPE: linear low density polyethylene
MDPE: medium density polyethylene, bimodal resin
HDPE: high density polyethylene, low pressure polyethylene
UHMWPE: Ultra High Molecular Weight Polyethylene
UHMWPE UHMWPE is very strong and can be used as a body armor.
Modified polyethylene: CPE, cross-linked polyethylene (PEX)
Main uses: such as agricultural film, floor covering film, agricultural film, vegetable greenhouse film, etc.; packaging film such as candy, vegetables, frozen food, etc.; liquid packaging blown film (milk, soy sauce, juice, tofu, soy milk) ; heavy packaging bags, shrink wrap film, elastic film, lining film. This material cannot be used on commercial vacuum packaging machines and will be broken. Only used on small household vacuum packaging machines.
Manufacturing process: casting method (CPP), biaxial stretching method (BOPP)
Features: BOPP physical stability, mechanical strength, air tightness, high transparency and gloss, toughness and wear resistance, is currently the most widely used printing film, generally used thickness of 20 ~ 40μm, the most widely used is 20μm . The main disadvantage is poor heat sealability. CPP can be divided into ordinary CPP and cooking grade CPP. It has excellent transparency, uniform thickness and uniform longitudinal and horizontal properties. The thickness of ordinary CPP film is generally between 25 and 50μm. It has good transparency after compounding with OPP. Bright, strong hand, this film also has good heat sealability. The thickness of the cooking grade CPP film is generally between 60 and 80 μm, and can be cooked at a high temperature of 121 ° C / 30 min. The oil resistance and air tightness are good, and the heat seal strength is high. The general meat package inner layer is made of cooking grade. CPP film.
Main use: BOPP is generally used as the outer film of composite film; CPP is generally used as the inner layer material of composite film. This is a commonly used material for vacuum packaging bags.
Manufacturing process: biaxial stretching
Features: Extremely high mechanical strength, rigidity, heat resistance, and chemical resistance. The transparency and gloss are also excellent, water permeability, gas permeability is not large, particularly good aroma retention, excellent printing performance (generally no surface treatment is required).
Main use: It is used for all kinds of food, medicine, non-toxic and sterile packaging materials. This is often used in vacuum bags.
4.PA (NY) polyamide (nylon)
Manufacturing Process: Casting Method (CPA), Biaxial Stretching (BOPA)
Features: It has good comprehensive performance, including mechanical properties (very high puncture resistance), heat resistance, abrasion resistance, chemical resistance and self-lubricating, and has low friction coefficient and certain flame retardancy. It has good softness and printability and is easy to process. The disadvantage is that it has high water absorption, affects dimensional stability and affects the composite fastness.
Main use: It is applied to vacuum bag, retort bag and liquid packaging. Special nylon MXPA with higher barrier, high temperature resistance and impact resistance. Such vacuum bags are often used.
5.AL aluminum foil
Features: low mechanical strength, easy to fold, easy to tear. It has the advantages of moisture-proof, air-tight, shading, abrasion resistance, fragrance preservation, non-toxic and tasteless. For the packaging of cooked food, the use of this composite aluminum foil material can at least guarantee that the food will not deteriorate for more than one year. There are hard aluminum foil and soft aluminum foil. The thickness of the hard aluminum foil is 20~30μm; the thickness of the soft aluminum foil is 7~9μm. The pressure delay requires a large amount of lubricating oil to cool and lubricate. Single-chip pressure delay, two-sided light; two pieces of calendering, one side of light, one side of dark. Hard aluminum is generally used as a composite layer (relatively low surface finish), and soft aluminum is used in printing composites. Regarding the pinhole problem: 7 μm is less than 50 holes/m 2 ; 9 μm is less than 30 holes/m 2 ; 11 μm is less than 10 holes/m 2 .
Main use: It is used for the packaging of beer, canned water and other beverages, and cooked foods. The surface oil stain is divided into four grades A, B, C, and D. Such vacuum bags are also commonly used.
6.EVA ethylene-vinyl acetate copolymer
Characteristics: The performance of this material is determined by the content of vinyl acetate (VA). When VA>25%, the heat resistance is poor, the adhesion is good, the blocking property is large, and the acetic acid smell is large. It should be applied on hot melt adhesive as a film. application. VA ≤ 25%, generally 5 to 15%, the less the VA content, the more like PE performance. Very good transparency, puncture resistance, cold resistance, softness, impact resistance, low temperature easy to seal, but heat resistance and moisture resistance are worse than PE (more expensive).
Main use: for aseptic packaging, hot tanks and retort pouches. The packaged food includes sauces, yoghurt, ketchup, fruit juice, meat, cheese and fruit. This vacuum bag is also used.
7.EVOH (EVAL) ethylene-vinyl alcohol copolymer
Features: BOEVAL high breaking strength, impact strength and puncture resistance, good aroma retention, transparency and softness, strong printing performance, no static electricity, excellent barrier properties, is one of the best film packaging performance of food and medicine However, the price is expensive (film is about 100,000 yuan / ton, pellets is 6,000 to 70,000 yuan / ton). Disadvantages: high water absorption (larger than EVA), water vapor transmission rate is higher than LDPE, O2 transmission polarity.
Main use: Similar to EVA. For aseptic packaging, hot tanks and retort pouches. The packaged food includes sauces, yoghurt, ketchup, fruit juice, meat, cheese and fruit. This kind of raw material vacuum packaging bag is often used.
8.PT cellophane (cetinol)
Features: highly transparent, colorless, good rigidity, no static electricity, high polarity, good printability, low gas permeability, good gloss, especially sun light, no aging, not easy to pollute, good heat resistance, The kinks do not rebound. Disadvantages: large brittleness, easy to break, poor cold resistance, non-resistance, no heat sealability, coated PT heat sealability is very low. Divided into two types of moisture-proof and non-moisture-proof [KPT/PT]. PT contains 0-15% water-soluble plasticizer, which has high hygroscopicity and high water permeability.
Main use: Widely used in the inner liner of paper and decorative packaging paper. This material is rarely used.
9.PVC (polyvinyl chloride)
Manufacturing process: calendering, blow molding, and stretching.
Features: There are three types of hard, semi-rigid and soft. Advantages: transparency, printability. Disadvantages: poor heat resistance and cold resistance. When the PVC film is thin enough, it is self-adhesive.
Main use: Suitable for beverage label film, wine bottle cap packaging, etc. The film is used for fruit and vegetable coatings. This kind of raw material, vacuum packaging bags are rarely used.
10.PVDC (polyvinylidene chloride)
Characteristics: PVDC film is the best barrier film, not susceptible to temperature changes, good transparency, heat resistance and cold resistance. Divided into stretched PVDC film / PVDC emulsion. PVDC emulsion acts as a coating to increase barrier properties (whitening after steaming).
Main use: Widely used in casing food packaging, medicine, military packaging, etc. This vacuum packaging bag is also used.
11. Aluminized film (PET, CPP, PT, PVC, OPP, PE, paper)
Features: beautiful decoration, excellent barrier properties; contrast light barrier, improved overall performance, water permeability reduced by tens to hundreds of times.
Main use: instant noodles, puffed food packaging. This type of vacuum packaging is rarely used.