Common Problems and Solutions of PVC Absorption Technology

February 27, 2018

Introduction of suction process:

 

 

Plastic absorption is a kind of plastic processing technology. The main principle is that the flat plastic sheet is heated and softened, the vacuum is adsorbed on the mold surface, and formed after cooling. It is widely used in plastic packaging, lighting, advertisement, decoration and other industries.

 

Absorbent packaging products mainly include: bubble shell, tray, suction plastic box. Also called: vacuum cover. Bubble cover, etc. Plastic packaging equipment mainly package: suction molding machine, punching machine, sealing machine, high frequency machine, folding machine. Packaging products can be divided into: plug-in, suction card double bubble shell, half bubble shell, fold bubble shell, three fold bubble shell, etc.

 

The use of transparent plastic plastic process will be transparent plastic sheet made of specific convex shape of the mask on the surface of the product, to protect and beautify the role of products, the ordinary plastic yingpian stick on the surface layer of the solute material, so that the surface of the tray has a solute handle, used to improve packaging grades, with special plastic tray the process of modified material, the material surface resistance value of 11 ohm put less than 10. Mainly used for static tray electronic.IT products.

 

The mould used for suction production is the gypsum mould with the lowest cost, the second is the copper plating mould, and the most expensive mold is the aluminum mold. The mold has a hole in the hole and is used for the vacuum adsorption heat of the hard sheet to form the absorbent product.

 

As we often say, absorbent molding machine is used to adsorb the hot softening plastic hard sheet on the mold surface. After cooling, the plastic is formed in the shape of concave and convex shape.

 

Plastic cutting: plastic products formed by suction packaging, after punching, the large sheet is divided into a single product by cutting die.

 

Folding: one of the absorbent packaging products is called plug-in packaging, the three edges of the bubble shell need to be folded to the back of the folding machine, so that in the next packaging process, the paper card is inserted into the folding edge to form card cartridge packaging.

 

Thermal sealing: is a plastic absorption packaging process, with the sealing machine will be coated with absorbent oil on the surface of the paper card and bubble shell together, forming card packaging,

 

High frequency sealing: it is a kind of high cycle wave machine to produce ultrasonic wave, which binds bubble shell and bubble shell together to form double bubble shell packaging. Unlike high frequency sealing, ultrasonic wave can not only seal PVC.PET.PETG material, but also seal PET material. And packaging products with electromagnetic damage, especially suitable for electronic packaging: the disadvantage is the ultrasonic edge can only be spaced dotted, and usually only one edge at a time.

 



 

The principle of PVC plastic film:

 

The PVC film is close to MDF during heating and softening, and the air between PVC film and MDF film is removed by vacuum, and the PVC film is tightly attached to MDF by atmospheric pressure. This process is called vacuum plastic film.

 

The characteristics of PVC film:

 

The adhesive used for vacuum plastic film is vacuum absorbent adhesive, which is mainly waterborne polyurethane adhesive and mixed with other resins. In principle, hot melt adhesive and solvent-based adhesive can also be used, but water-based adhesive is non-toxic, odorless and moderate in price. Suitable for mechanized operation.

 

The biggest feature of this process is that it does not need to be sprayed with paint or paint, it is a lacquer free process, in addition, it can be coated with concave and convex grooves, curved surface edges, and hollowed-out engraving parts, which can not be compared with other processes.

 

Application of PVC absorbent film:

 

Vacuum plastic film coating technology is widely used in the manufacture of computer platform, loudspeaker board, cabinet, door and furniture, and a large number of applications in the processing and manufacturing of automotive interior accessories.

 

Vacuum plastic absorption processing is developing rapidly, and the medium density fiberboard (MDF) of 45% in Japan is covered with vacuum plastic film, and the MDF processed by PVC in China has reached 30 million m, and has been increasing at a rate of more than 8% per year.

 

Performance requirements of vacuum absorbent adhesive:

 

Vacuum absorbent adopts spray sizing, so it is required that the viscosity of vacuum absorbent adhesive is moderate, which can adapt to the change of winter and summer weather, and can realize spray atomization. In addition, vacuum absorbent adhesive also has the following characteristics:

 

1) good flowability and clean surface after suction.

 

(2) high solid content, fast drying.

 

3) good initial adhesion, in the grooves, the edge of the special requirements for the initial adhesion of plastic.

 

(4) the heat-resistant aging property is good, at least at 60 ℃, after 24 hours baking, the film does not curl, shrink, and foaming.

 

(5) the activation temperature is low, the activation temperature must be one when using waterborne polyurethane adhesive, the activation temperature must be in the range of 55 ~ 65 ℃, the temperature is too high and the PVC membrane is easy to perforate.

 

Common problems and Solutions in PVC suction process

 

Phenomenon 1: groove foaming

 

Cause analysis:

 

1. If the temperature or pressure does not meet the requirements, resulting in false aspiration;

 

2.The quantity of glue is not enough, the quantity of spraying is less or the plate is permeated with glue;

 

3. Not enough preheating (softening PVC film) or absorbing time (molding time);

 

4. After plastic forming, the pressure is removed before the temperature is dropped.

 

5.The heat resistance of the glue itself is not enough.

 

Solutions:

 

1. Increase in temperature or vacuum;

 

2. Increase the sizing quantity and select the good quality plate;

 

3. Increase preheating or molding time;

 

4. After plastic molding, the temperature is cooled to room temperature or slightly higher before withdrawing from the vacuum.

 

5 . The curing agent is used .

Phenomenon II: local foaming

 

Cause analysis:

 

1. Uneven spray of glue, resulting in a small amount of local adhesive, resulting in a decrease in bond strength;

 

2. PVC membrane contains plasticizer. Under the condition of aging or heating, plasticizer is easy to migrate to the surface, which affects the bond strength.

 

3. The heating pipe in the suction machine has a problem, resulting in uneven temperature.

 

Solutions:

 

1. As far as possible, the amount of glue sprayed evenly;

 

2.Use PVC film of good quality;

 

3. Timely maintenance of equipment.

 

Phenomenon 3: the edge cannot be sucked or contracted

 

Cause analysis:

 

1. The side temperature is low or the vacuum degree is not enough when the plastic is sucked;

 

2.The heat resistance of glue is not enough;

 

3.After the suction molding, the pressure is removed before the temperature is dropped.

 

Solutions:

 

1. Increase in temperature or vacuum;

 

2. Use of curing agent;

 

3. After suction molding, the temperature is cooled to room temperature or slightly higher before withdrawing from the