- Reduce the thermal seal temperature formula for blowing film machine
The starting temperatures of various heat sealing films were as follows: LDPE 135 ° C, LLDPE 148 ° C, EVA (VA content of 7.5%) 107 ° C, EVA (VA content 12%) 93 ° C, EMA (methyl methacrylate) 79 ° C, EMAA (Vinyl methacrylic acid) 93 ° C, surledn121 ° C, EAA (vinyl acrylic acid) 93 ° C.
The various resins have good compatibility, and the extrusion blown film or extruded in the extrusion can reduce the heat sealing temperature after mixing each other. Such as:
LDPE + EVA (50% + 50%)
LDPE (50%) + 50% EMA;
LDPE70% + 30% EAA;
LDPE70% + 30% EMAA.
- Improve the heat-sealed film with cold resistance or heat resistance
The cold-resistant temperatures of various hot segments are as follows: EVA, EAA, EMAA can resist -65 ° C ~ -73 ° C, LLDPE can resist-68 ° C ~ -73 ° C, PC (polycarbonate) can be resistant to -65 ° C ~ -75 ° C, LDPE can resist -48 ° C ~ -50 ° C, MDPE can resist -42 ° C ~ -45 ° C, surleng can resist-38 ° C ~ -42 ° C, HDPE can be resistant to -40 ° C, polystyrene can be 0 ° C, homopolypropylene can be resistant to 5 ° C, copolymerized propylene (a copolymer containing 5% to 8% of ethylene) can be resistant to -8 ° C.
Polyethylene and its acrylic copolymers have good low temperature resistance, while homogeneous polymer resistance is poorly resistant, and propylene is copolymerized with ethylene in a copolymerization method to increase the cold resistance of propylene homopolymer. Such as: the ethylene content of 5% to 8% is -8 ° C, and the ethylene content is 20%, the cold resistance can reach -15 ° C, and the film is flexible, it should be pointed out that the compatibility of polyethylene and polypropylene should not be very Ok, only general, the PE + PP blend is not desirable. Polypropylene cold resistance can also be increased with ethylene-acrylic acid copolymerization, and the PP is not compatible with the surleys resin, so that both cannot be blended.
Its formula is:
HPP (homogenic polypropylene) 50% + EVA50%;
HPP (homopolymerized propylene) 70% + 30% EAA;
HPP70% + 30% EMA;
HPP70% + 30% Emaa.
High temperature resistance of various plastics is as follows: EVA, EAA, EMAA can have a long time to resist 55 ° C ~ 85 ° C, LDPE 85 ° C ~ 100 ° C, MDPE resistance 95 ° C ~ 105 ° C, HDPE resistance to 115 ° C ~ 120 ° C, surleys 70 ° C ~ 85 ° C, LLDPE 95 ° C to 115 ° C, PS 85 ° C, HPP 80 ° C, copolypropylene (B-CPP) 130 ° C ~ 135 ° C, PA66 at 160 ° C to 165 ° C.
When a thermally resistant film is required, an HPP film or a B-CPP film can generally be used directly. The PP is used to blend modification only when the material with an acrylic acid and its ester is the main heat sealing material, and the heat resistance is used to improve heat resistance, such as 70% EAA + 30% B-CPP, 70% EMAA + 30% B. -CPP.
- Improve heat sealing strength formula
At 2 kg / cm2 pressure and a heat seal rod heat seal 508 μm, the heat seal strength of the unit g / 25.4mm is as follows: LDPE: 1800
LLDPE is 2500
EVA (VA7.5%) is 1800
EVA (12% VA) 1700
EMA is 1300 EMAA1800
Surlyn2000 EAA is 1700
It can be seen from the above, LLPE is a high heat sealing intensity. The most commonly used LDPE50% + LLDPE50% mixture as a heat sealing film, has a good heat sealing strength.
- The heat sealing property of mixed inclusions
The performance of the heat sealing property is compared: ionic polymer (surled> MPE> LLDPE> HDPE> MDPE> LDPE> EVA.
Formulation 1: HDPE70% + LDPE30% + white raw materials
Uses: Extruding the film, can be used in Papan sterilization simple packing milk film, shallow cooling and sales.
Formula 2: HDPE / LDPE or HDPE / EVA coextrusion
Features: The inner layer of the coextruded film has a lower melting point and has high strength in the outer layer, suitable for the inner seal layer and a simple milk film.
Formulation three: LDPE or LDPE50% + LLDPE50% or other polyolefin compounds added 600 ppm or more mustard amide.
Features: After a dry composite film, at 35 ° C, after a week, it can have a dynamic friction coefficient of 0.2 to 0.4, suitable for packaging of powder, high viscosity liquid, the key is that the ripening temperature is around 35 ° C. Can’t be too high.
Formulation four: HDPE Mi <1g / 10min + 0.3 ~ 0.7% of calcium stearate is a nucleating agent.
Features: The film has high strength and improved transparency
Formulation 5: LDPE70 ~ 85% + MPE5 ~ 15%,
Features: The price is moderate, and there is a hot sealing property, the height heat sealing strength, when the film is blown, the film is stable, the thickness of the thickness is better.
Formulation six: HDPE (Mi 20g / 10min), 90 parts weight + LLDPE (Mi 2G / 10min), 10 parts.
Features: After mixing, extruding the blown film, has good strength and thermal bond, and good clamp heat sealing.
Formulation Seven: Ethylene-propylene block copolymer (Mi 0.5 g / 10 min), 30%; HPP (Mi 0.5 g / 10min), 30%; HDPE (Mi 0.3 g / 10min), 40% mixed extruded film.
Features: There is a good torn strength, a high temperature cooking resistance of 115 ° C, and the height of stress cracking.
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