Nylon material properties

A, classification and properties of nylon classification:

1, according to the number of carbon atoms of diamine and dibasic acid, composed of two monomer synthetic nylon: 46, 66, 610, 66, 613, 1010, 1313,

2, according to the monomer containing named in the number of carbon atoms: nylon 4, 5, 6, 7, 8, 9, 11, 12, 13

Second, features:

1, nylon has good toughness, self lubrication and wear resistance, chemical resistance, gas permeability, and oil resistance, non-toxic, and the advantages of easy coloring, so the nylon is widely applied in industry.

The technological characteristic of the rheological properties of nylon, nylon: most for crystalline nylon resin, when the temperature exceeds its melting point, the melt viscosity is small, the melt liquidity is wonderful, should prevent excessive edge. Due to the melt condensation speed at the same time, should prevent material blocking the nozzle, runner and gate products caused by insufficient phenomenon. Mould overflow boundary value of 0.03, and the melt viscosity are sensitive to temperature and shear stress change, but is more sensitive to temperature, lower viscosity of the melt from the cylinder temperature first.

Four, nylon nylon absorbent, water absorption and the dry wet nylon in molding process, characterized by viscosity fell sharply and mixed with surface silver bubble products, the products obtained mechanical strength decreased, so the material must be dry before processing.

Crystalline: in addition to the transparent nylon, nylon mostly for the crystallization of polymer, high crystallinity and tensile strength, abrasion resistance, hardness, lubricity, and so on a performance improvement, thermal expansion coefficient and water tends to decline, but bad for transparency and impact resistance. Had a greater influence on the mold temperature on the crystallization, mould temperature high crystallinity, die temperature bottom end of crystallinity.

Shrinkage: similar to other crystalline plastics, nylon resin shrinkage rate larger problems, the maximum nylon with crystallization of contraction, when products crystallinity big products shrinkage increases, in the process of forming lower mold temperature, increasing injection pressure, lower temperature will decrease the contraction, but the internal stress of products is more easy to deformation. PA66 shrinkage rate of 1.5 to 2%

Molding equipment: nylon molding, mainly pay attention to prevent "nozzle flow delay phenomenon", so the nylon material processing generally choose the self-locking type nozzle.

Products and moulds:

1, the products of wall thickness Do so than for 150-200 between nylon, nylon products wall thickness below 0.8 mm generally between 1-3.2 mm, and the products of contraction associated with products of wall thickness, the thicker the thickness contraction.

2, exhaust nylon resin overflow boundary value is about 0.03 mm, so the vent groove should be controlled below 0.025.

3, mold temperature products thin wall molding mould heating control or require high crystallinity, required products have certain flexibility of general use cold water temperature control.

Third, molding technology of nylon

Cylinder temperature: as nylon is a crystalline polymer, so obvious, melting point of nylon polymer in the injection molding of the selected material barrel temperature with the performance of the resin itself, equipment and products of shape factors. Nylon 6 melt temperature is 225 ℃ at the bottom, nylon 66 is 260 ℃. * due to the poor thermal stability of nylon, should not be so high temperature for a long time to stay in the cylinder, lest cause the material color is yellow, due to the liquidity of nylon is better at the same time, the temperature over flow quickly after its melting point.

Injection pressure: nylon low melt viscosity, good fluidity, but the cooling speed faster, the complex shape and wall thickness thinner products are easily appear shortage problem, so still need high injection pressure. Pressure is too high, usually products will overflow edge problems; Pressure is too low, products can produce corrugated, bubble, obvious welding scar or lack of product defects, most varieties of nylon injection pressure does not exceed 120 mpa, the general selection within 60-100 mpa is meet the requirements of most of the products, as long as the products don't appear bubbles, defects such as dents, generally do not want to use high pressure maintaining pressure, so as not to cause internal stress increased.

Injection speed: for nylon, injection speed for quick profit, can prevent the ripples caused by too fast cooling, molding shortage problem. Fast injection speed impact on the performance of the products is not prominent. Mold temperature mold temperature on the crystallinity and the molding shrinkage has certain influence, anti-embrittlement high crystallinity, wear resistance, hardness and elastic modulus increased, decreased water imbibition, products molding shrinkage rate increase; Low mold temperature low crystallinity, good toughness and elongation is higher.

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electrical and electronic engineering plastics application

Compared with general plastics, engineering plastics has more excellent mechanical properties, electrical properties, chemical resistance, heat resistance, abrasion resistance, dimension stability, etc; Compared with metal materials, engineering plastics has the advantages of light weight, small energy consumption when molding. Engineering plastics has become the world's plastics industry developing the fastest growing materials

In Asia, engineering plastics are mainly used in electrical industry, more than 50%, and in Europe and the United States, engineering plastics are mainly used in automotive industry. From 1998 to 1998 China engineering plastics consumption annual average increase rate of 26% (see chart 1). Is expected in the next few years the growth rate of 15% ~ 18%. As China's electrical products exports increased year by year, the dosage of the engineering plastics is on the rise. Although the current domestic product technology content and added value is very low, but this does not affect the huge demand for engineering plastics manufacturing. Under cost pressure, requirement for material localization is more and more obvious, which provides a broad prospect of application for engineering plastic.

Commonly used on electrical and electronic engineering plastics

1. The PA (nylon)

PA is characteristic of good toughness and high mechanical strength, wear resistance, but easy bibulous deformation. Mainly used in the manufacture of machine tools in electrical and electronic appliances, air switches, connectors, all kinds of coil skeleton; Tape recorder, video camera, video camera, DVD, OA equipment, machine core, skeleton, supporting parts, gear, wheel; As well as the cable bracket, brace, gear, wheel; And the cable sheath, household appliances, small appliances, etc.

2. PC (polycarbonate)

The advantage of PC is transparent, high impact strength, good mechanical strength, size stability. Drawback is not resistant to solvents, easy to produce stress cracking. Mainly used in the transparent parts of the electrical appliances (such as window, shell, panel, etc.).

PC/ABS alloy is more used in electrical appliances shell, display case, mobile phone shell, shell, batteries, laptop charger shell; Cable connector, OA equipment and small home appliance products.

3. The POM (POM)

POM has superior mechanical properties. Wear resistance and size stability, resistance to chemical corrosion, fatigue resistance, but poor thermal performance, flammable easy decomposition, notch sensitivity. Mainly used in electrical appliances, instrument structure, all kinds of gear, CAM, driving wheel, the recording tape axis core, floppy disks, the doors of machine tool electrical appliances.

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overmolding

To meet the special needs of many plastic products, many plastic products are not made ​​from a plastic material, coupled with the appearance of plastic products and process requirements need to use two or more kinds of plastic materials in multiple injection molding method, called secondary injection molding.

Not only can the second injection devices filled with soft-touch surface, can also increase product functionality and value. In the past 10 years, the second injection technology has revolutionized the consumer goods aesthetic standards, design ideas and functional requirements. Medical device manufacturers are also aware of the potential advantages of this technology, expanding its application in the medical field. Secondary injection technology to create a "soft-touch surfaces" and famous, but it also has many other features, such as: ergonomic design, color appearance, brand identity and characteristics improvement. With this technology, you can increase the product's features (for example: noise, vibration, waterproof, anti-collision) and added value.

Second injection and common injection molding, injection molding and double injection sandwich, as are multi-material injection molding technology. The basic idea is the multi-material injection molding together two or more materials with different characteristics, thereby enhancing the product value

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The properties of the PVC material and injection molding process

PVC material because of cheap, born to have anti-inflammatory properties, tough and strong, good chemical resistance, shrinkage ratio of 0.2 to 0.6%, the product in electrical appliances, machinery, building, daily necessities, toys, packaging applications increasingly widespread, according to the characteristics of PVC material, analysis product injection molding process is as follows:

1, the characteristics of PVC material

PVC thermal stability, molding temperature and decomposition temperature is close to, poor liquidity, easy to form bad appearance defects, PVC material poor heat resistance, burning, acid gases and most easily corrosion mold, processing additive plasticizer increased its liquidity, generally use doping, its strength, good electrical insulation, drug resistance.

2, mould and gate design

To shorten the injection molding cycle, the shorter the sprue, the better, a transverse to the garden, shoot tip of minimum 6 mm diameter, conical, an internal Angle into five degrees, best to add cold slug well, bad cold slug well can prevent melt semisolid material into the cavity, which will affect the surface modification of materials and products such as strength. Draft Angle to between 0.50 to 10, to ensure that the cavity you have plenty of exhaust device, commonly used vent size 0.03 0.05 mm deep, 6 mm wide, or each thimble peripheral clearance of 0.03-0.03 mm. Mould application is made of stainless steel or hard chromium plating.

3, PVC molding process

PVC is heat-sensitive plastic, shear excessive can cause overheating or decomposition, and quickly spread, because one of the decomposition (such as acid or HCI) will produce catalysis, lead to process further decomposition, acid erodes metal, into depression, and can make the metal protective layer spalling, caused by rust, more harmful to the human body

4, injection speed:

Injection speed slower, or excessive shear will make the material degradation, using UPVC production extremely smooth and thick wall products, multi-stage injection speed should be adopted, if there is a beige stripe to radiate from the gate, it indicates that the feed speed is too fast.

5, back pressure：the surface of the common value is 5 bar, increasing back pressure to mixed color and exhaust, but should back pressure is lower, the better.

6, downtime: as the PVC thermal stability is low, so the downtime of flash is very important, put the barrel clean, without leaving any PVC, can use other overheat high stability and resistance of PVC thermoplastic, or (for example, PMMA, PP, LDPE, GPPS), avoid by all means within the same barrel mixed POMT UPVC, otherwise it will cause a strong chemical reaction, cause serious damage to the machine.

7, mixing proportion: shuikou material mixing ratio is 20%, most otherwise it will affect the products quality.

9, typical products: UPVC drainage pipe main purpose is to create, or the computers and TV shell, filter water pressure tank, copy machine shell, and gas meter shell, transparent bubble of printing presses, style, and various electronic components, etc.

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Mould press technology is analysed

IMD's Chinese name: extrusion surface decoration technologies (mould decoration), namely the IMD (In - Mole Decoratiom), IMD is popular In the international surface decoration technology, mainly used In electrical appliances product surface decorative and functional panel, commonly used In the mobile window lens and housing, washing machine control panel, refrigerator, air conditioner control panel of the control panel, car dashboard, rice cooker control panel panel, signs of a variety of domains such as pieces of the appearance.

IMD (In Mold Decoration) is a kind is placed In the injection mould to decorate the plastic Film Film appearance on the surface of the new technology. IMD currently there are two kinds of methods, one kind is the printed Film roll Film made into circulation drum belt, installed in the injection molding machine and injection molds, like the tag Label on front mould surface automatic cycle produced with mobile; People call it the IMD (in mold transfer molding).

The other is a good Film Film printing machine after Forming Forming, again after shearing is placed in the injection mould. Is called on IML film (in the mould injection molding). The Film in general can be divided into three layers: base material (PET) normally, printing INK layer (INK), agglutination materials (as a special kind of glue).

When the injection is completed, through the role glue Film and plastic together together, because itself is surface of wear resistant protective Film PET in the outermost layer, have the effect of the wear resistance and scratch resistance, its surface hardness can be up to 3 h, and will feel more and more bright. The molding material, PBT, PC, PMMA, etc

The traditional plastics processing technology has been gradually cannot satisfy the demand of the new age, light, thin, short and consumer electronic products and the rise of environmental consciousness, IMD technology is based on the arises at the historic moment. Due to the advantage of (IMD) is suitable for 3 c, household appliances, LOGO name plate and plastic products of auto parts, especially the popularity of mobile phone shell, and all kinds of instrument panel. The world's advanced manufacturers such as Bayer (Germany), American GE, are fully in the development process.

(IMD) mould decoration is a relatively new production process automation, compared with other technology (IMD) can simplify production process and reduce the piecemeal components, so can quickly production to save time and cost, also improve quality, increase the complexity of the image and improve the application on the product appearance, product durability advantages (IMD) is the most efficient method, it is on the membrane surface to print, high pressure forming, cutting, and finally combined with plastic molding, exempt from secondary operating procedures and manpower working hours, especially in backlit and curved surface, fake metal and wire processing, logic light lines, frame interference... When printing paint process to handle, but also the timing of use IMD process.

(IMD) mould decoration can replace many of the traditional process, such as thermal transfer, spraying, printing, electroplating and other exterior decoration method. Especially need a variety of color images, backlight, and other related products

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Mould to stick mark

Mould to stick mark

Mould labeling is a different from the traditional direct screen printing, heat shrinkable label, the non-drying label of new label packaging form,

At the beginning of the domestic large-scale application.

Mould labeling is mainly used for the material such as PP, PE, PET blow molding and injection molding products. Namely before blow molding, injection molding has been printed mould

Labeling in blow and injection molding cavity, when blowing, injection mold on, through the effect of high temperature and high pressure in the inside mould making mould labeling on the special product, with the bottle or plastic surface, when the mold opens, a has beautifully printed bottles or note a one-time finish.

Mould stick mark advantages:

1. Enhance the anti-counterfeiting function of products directly, can conform to high standard enterprise brand protection needs more.

2. Mould labeling, can do laser printed, aluminum plating, such as special effects, make the product packing grade is greatly increased.

3. The form is novel and attractive, fall off not easily broken, waterproof, prevent oil, mouldproof

4. Increase the health, safety of packaged products, put an end to the secondary printing and labeling of environmental pollution.

5. The comprehensive cost significantly lower than the traditional label and direct screen printing and environmental protection.

Mould stick mark application industry;

1. Beauty, hairdressing products packaging container

2. Medical and health care products packaging container

3. The food and beverage packaging container

4. Oil powder, such as liquefied products packaging containers

5. Cooking oil, soy sauce, vinegar and other spices packing container

6. Wash basin, barrel, cup, etc. The adornment of the commodity.

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Eliminates when injection molding plastic deformation method

The causes of deformation

1, the shape of products, especially forming shrinkage relationship with product thickness caused by residual stress

2, due to the forming conditions of residual stress in 3, parting the residual stress produced in 4, and deformation due to insufficient cooling time

2. The associated knowledge

1, the deformation of the products (warping, bending, small wrinkles) as well as the reasons of the crack.The residual internal stress in the products.Molding set conditions should be set in eliminate products of internal stress direction. Namely improve material barrel temperature and mould temperature, the material liquid get better state, the injection pressure is not too high.

2, in order to reduce the residual stress, annealing processing, namely under thermal deformation temperature of 10 degrees, more than 2 hours of heating has the effect of stress relief. But this way because of the high cost of annealing and use is not common.

3, if the mould cooling hole not to cooling homogeneity of products, also can produce residual stress, which means that the cooling hole can't be too shallow.

Third, solution.

1, instant: sufficient cooling solidification in the mould (chronograph longer cooling time), and improve the temperature of the material, reduce the injection pressure.

2, short-term: make mold cooling uniformity.

3, long-term: avoid the thickness of products, where product thickness large set gate (1-1), caused by a straight line easy to warp, make it big R curve, products reversible bending die, increase the number of ejection rod, increase the draft.

Four, differences in material:

1, the crystalline materials (poly (PVC), polypropylene, pom, nylon),molding shrinkage rate, and easy to cause bias, non-crystalline material (polystyrene (PVC, ABS) easy to cause residual stress.

Five, the reference items:

1, use orthotics keep at room temperature after molding, to prevent deformation, slightly but not hope too much.

2, in the box forming of thin shape, bending caused by molding temperature, this is common thermal expansion

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