The main properties of plastic products

The main properties of plastic products

Plastics is made from plastic as main raw materials processing of living supplies, industrial supplies.

Compared with other materials, plastic has the performance characteristics of the following aspects:

1. Light weight plastic is lighter material, relative density distribution is between 0.90 2.2. Obviously, the plastic can float to the surface of the water? Foamed plastics, in particular, because there a microporous, quality of a material is lighter, relative density 0.01. This makes the plastic can be used to reduce the weight of the product production.

2. Excellent chemical stability The vast majority of plastic of acid, alkali and other chemicals have good corrosion resistance. Especially commonly known as king plastic for ptfe (F4), its chemical stability is better than gold, even in the "aqua regia" boiled over ten hours also can't bad. Because the F4 has excellent chemical stability, is the ideal of corrosion resistant material. Such as F4 transport corrosive and viscous liquid can be used as the material.

3. The excellent electrical insulation properties Common plastic is a poor conductor of electricity, its surface resistance and volume resistance is very big, with Numbers of up to 109 a 1018 ohms. The breakdown voltage, dielectric loss Angle tangent value is very small. As a result, the plastic in the electronic industry and mechanical industry has been widely used. Such as plastic insulated control cables.

4. A poor conductor of heat, with noise elimination and damping effect Generally speaking, the thermal conductivity of the plastic is relatively low, quite steel 1/75-1/225, the microporous foam contains gas, its better heat insulation, sound insulation, shockproof sex. Such as polyvinyl chloride (PVC) thermal conductivity was only about 1/357 of the steel, aluminum 1/1250. On insulating ability, single glass window plastic is 40% higher than the single glass window aluminum, 50% higher than double glass. Will be combined with hollow glass, plastic form used in residential, office, room, hotel, save central heating in the winter and summer air conditioning saving costs, benefits obviously.

5. Wide distribution and high mechanical strength than strength Some plastic as hard as a stone, steel, and some soft such as paper, leather; From the plastic hardness, tensile strength, elongation and impact strength mechanical properties, such as wide distribution, there is a lot of use of choice. Because of the proportion of plastic small, strength, and thus has high specific strength. Compared with other materials, plastic also exists obvious shortcoming, such as easy burning, high stiffness than metal, aging resistance is poor, no heat, etc.

overmolding

Secondary molding forming

overmolding 

The secondary forming is one of the plastic molding processing method. With plastic material or parison as raw material, make its external force by heating and a method of the shape of the products needed.

Secondary molding is a the piece, pipe, plate, such as plastic material, heating in a kind of rubber state, deformation by external force and moulding for all kinds of simple shape, then through cooling stereotypes and products. Secondary molding including the hollow blow molding, thermoforming, stretching film forming method, such as only applies to thermoplastic plastic molding. Secondary molding is in a molding on the basis of a method.

Mainly includes the following several forming methods:

thermoforming

Hot forming is a thermoplastic plastic sheet is heated to softening, the gas pressure, liquid pressure or mechanical pressure, using the appropriate tooling or jig and make its products a molding method. Plastic thermoforming method are many, generally can be divided into:

Molding using single mode (male die and female die) or to die, using plus mechanical pressure or weight, to make all kinds of products from sheet forming method, it is different from a processing molding. This method is suitable for all thermoplastics.

Differential pressure molding using single mode (male die and female die) or to die, also don't have to die, in the gas under the action of pressure difference, make the heating to soft plastic sheets with mould surface, cooling is made after forming methods of various kinds of products. Can be divided into the vacuum forming and differential pressure molding pressure molding.

Thermoforming especially suitable for thin wall, large surface area of the products manufacturing. The commonly used plastic varieties have various types of polystyrene, organic glass, PVC, ABS, polyethylene, polypropylene, polyamide, polycarbonate, and polyethylene terephthalate, etc.

Thermoforming equipment including clamping system, heating system, vacuum and compressed air system and forming mould, etc.

Biaxial tensile

To make molecular reorientation of thermoplastic film or plate, etc, especially above the glass transition temperature of the bidirectional tensile process. Stretch orientation to between the glass transition temperature and melting point of polymer, after directional tensile and rapid cooling to room temperature, the film or monofilament, on the drawing direction has a lot to improve mechanical properties.

Suitable for directional stretching of polymer are: polyvinyl chloride (PVC), polyethylene terephthalate, polyvinylidene chloride, poly (methyl methacrylate, polyethylene, polypropylene, polystyrene, and some of the styrene copolymer.

Solid phase forming

Solid phase forming is a thermoplastic material or stock under pressure for products with mold the molding method. In the plastic molding process of molten (softening) under temperature (below the melting point at least 10-20 ℃). Solid phase forming. Including plastic of non-crystalline class above the glass transition temperature, melting point below the high elastic area processing is often called thermoforming, and below the glass transition temperature is called cold forming or room temperature molding processing, also often called cold working methods or room temperature plasticity of plastic processing.

The method has the following advantages: short production cycle; Improve the toughness and strength of products; Simple equipment, can produce large and super large products; Cost reduction. Defect is: hard to produce complex shape, the precision of products; It is difficult to control production process, the products easy to be out of shape, craze.

Solid phase forming include: sheet roll, deep drawing or sheet stamping, hydraulic forming, extrusion, cold stamping, roll forming, etc.

Injection molding common problem

Injection molding common problem

1, injection molding products warp and contraction deformation causes?

Answer: 1, cylinder temperature is too low; 2, short forming period; 3, the injection pressure is too high; 4, the injection speed quickly; 5, the holding time is too long; 6, uneven mold temperature, should adjust the mould cooling system, setting up reasonable cooling circuit; 7, gate section is too small; 8, ejection mechanism design is unreasonable, should try to increase the out area and point out; 9, die strength is insufficient, should try to increase its rigidity.

2, what is the causes and solutions of product ellipse?

A: ellipse is uneven due to the rubber products, product all round pressure not divide evenly, make products to elliptic. Solution: use 3 into the glue, make the product into the glue.

3 when using black color masterbatch, ABS, peeling products is easy to break, how to solve?

A: mother color pigment used in the carbon powder is overmuch, cause product peeling. Replaceable mother color pigment.

4, white products appear black spots, mixed color, how to control?

Answer: 1, the raw material. In the process of mixing materials, ingredients, pay attention to clean, prevent the impurities, mixed with dust; 2, the machine. (1) inside the cylinder to clean, screw on the presence of carbonized layer and rubber product; (2) the screw head, nozzle flange and nozzle parts whether matter, inner surface smooth and no dead Angle phenomenon; (3) the screw head for wear and tear, screw to install center degrees whether meet the requirements, presence of oscillating phenomenon. 3, mold. Mold flow channel without acute Angle, injection points shoulds not be too small.

5, injection molding products owe note the cause and the elimination method have?

A: plastic injection products owe note the cause and the elimination method basically has: 1, the melting temperature is too low, will raise the cylinder and nozzle temperature; 2, molding cycle is too short, should be appropriately extended; 3, low injection pressure, should be appropriate increase; 4, the injection speed too slow, should be appropriate to speed up. 5, the holding time is short, should be appropriately extended; 6 and underfeeding, should increase for shoes; In July and screw back pressure on the low side, should be appropriate increase. 8, gating system structure of small size, should be appropriate amplification and gate flow channel section. 9, mold venting is not good, should increase the vent, improve the exhaust performance of mold; 10, die strength is insufficient, should try to improve the rigidity of the die.

6, injection machine inlet temperature have any impact on product?

Answer: the inlet temperature too high or too low, can cause the machine back to the material is not stable, make add capacity is not stable, affect the size and appearance of the product.

7, set the injection molding process step is what?

A: set the injection molding process steps: 1, set the temperature of melting; 2, set mold temperature; 3, set screw dislocation and speed; 4, set back pressure; 5, set maximum injection pressure to the machine; 6, set pressure; 7, set injection speed; 8, set the holding time; 9, set the sample cooling time; 10, set to open mould time; 11, setting out board stroke; 12, minimize the holding time.

8, the main reason for the injection molding products have flash? What are those?

A: the main cause of injection molding products have flash are: 1, the template is not flat, or template insufficient rigidity and deformation; Haven't enough 2, clamping force, mold locking; 3, the injection pressure is too high; 4, raw material MFR value too high, the melt viscosity is low; 5, material temperature, mold temperature is too high.