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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Injection molding plastic parts appear flash solution

Injection molding plastic parts appear flash solution

A. The reasons of the burrs

1-1 mold parting surface (PL) sliding surface not to cooperate. 1-2 injection pressure is too high for 1-3 injection machine offset 1-4 lock to touch

2. The associated knowledge

2-1 mold parting surface of PL, the matching of the sliding surface, the ejection pin, block and so on. Constitute the mould of the gap between various slot, if material flow has become a flash. Flash a wedge block. Have gradually become big trend.

2-2 remove burrs of plastic parts on repair mold for the principle, on account of the bad forming conditions set at that time the emergence of flash, lower the temperature in the cylinder should be adopted. Lower mold temperature, injection speed reduce material liquidity in the direction of the setting parameters. But, in this would cause products should be paid attention to the internal stresses in the residual.

3. The solution

3-1 instant: reduce the injection pressure, decrease the temperature of the heating cylinder. Reduce the injection speed. 3-2 short term: grinding burrs in the mold surface. 3-3 long: mould using rigid steel material.

4. Because of the difference of the material

4-1 for liquid material is prone to flash, so the mold parting surface would have to close.

4-2 crystalline materials during melt viscosity is very low. Especially need to mould parting surface closely.

5. Reference

5-1 should be paid attention to, for the mould and excessive clamping pressure also can produce flash, parting surface, between the clip into the foreign body damage both mold, and produces the burrs.

5-2 mold material often use S50C JJS (Japan standard domestic 50 # steel) using HRC30 hardening of the special steel in advance, it is difficult to produce burrs in parting surface

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The basic knowledge of injection mould and technical application

That we use in our daily life and production to the various tools and products, to the base of the machine tool, the fuselage shell, small to a germ head screws, buttons, and all kinds of household appliances shell, which has close relation with the mould. The shape of the die decides the shape of the products, precision mold processing quality and determines the quality of these products. Because the material of all kinds of products, appearance, specifications, and different purposes of mould into casting die, forging die, die-casting mould, stamping mould of plastic moulds, such as, and plastic moulds.

In recent years, with the rapid development of plastic industry and general engineering plastics in the aspects of improving strength and precision, the application range of the plastic products are also constantly expanding, such as household appliances, instrumentation, construction equipment, automotive industry, daily hardware, and many other fields, proportion of plastics is rapidly increasing. A reasonable design of plastic parts often can replace more traditional metal pieces. Industrial products and daily products rising trend of plastic.

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Injection molding is the most widely used method in plastic processing. This method is applicable to all thermoplastics and part of thermosetting plastics, plastic products made the great number of them is the other forming methods of dust, as the main tool of injection molding processing, one of the injection mould, the quality of precision, manufacturing cycle and injection molding production efficiency in the process of the level of high and low, directly affect the product quality, yield, cost and product updates, at the same time also determines the enterprise in the market competition ability and speed of reaction.

Injection mould is made up of several steel plate with various parts, basic is divided into:

A forming device (die, die)

B positioning device (guide pin, guide sleeve)

C fixtures (h board, code die hole)

D cooling system (hole)

E thermostatic system (heating tube, hot line)

F runner system (pumping of nozzle hole flow channel slot and port holes)

G ejection system (thimble, top stick)

5, depending on the system of pouring system type of mould can be divided into three categories:

(1) the gate of mould, the runner and gate on the parting line, together with the product in the mould stripping, the simplest design, easy processing, low cost, so more people using gate system operation.

(2) nozzle mould: the runner and gate is not the parting line, generally directly on the product, so to design a set of shuikou parting line, design is relatively complex, processing more difficult, often depending on the product requirements to choose fine runner system.

(3) the hot runner mold: this kind of mold is approximately the same structure and fine shuikou, the biggest difference is that flow into one or more of the temperature of heat flow but and heat pumping mouth, no cold feeding demoulding, runner and gate directly on the product, so the port don't need mold release, also known as no runner system, this system can save raw materials, applicable to the raw material is more expensive, high requirement of products, design and processing difficulties, mould cost is high. Hot runner system, also called hot runner system, mainly composed of hot runner, hot water but, temperature control box. Our common hot runner system there is a single point of hot runner and hot runner 2 more forms. Single point gate is to use a single hot runner of the molten plastic into the cavity directly, it is a single cavity of a single gate of plastic mold; Multipoint hot runner by hot water but the molten material branch to various points in the hot runner set into the cavity, it is suitable for single cavity more into the material or multi-cavity mold

The advantage of hot runner system

1) material floolwing does not need after processing, the whole forming process is fully automated, save the working time, improve work efficiency.

(2) the pressure loss is small. Hot runner temperature and the temperature of the plastic injection machine nozzle is equal, to avoid the surface of the material in the runner, condensate loss in injection pressure.

(3) material floolwing repeated use can make plastic performance degradation, and the use of hot runner system is not shuikou expected, can reduce the loss of raw materials, thereby reducing the product cost. Uniform temperature and pressure in the cavity, plastic stress is small, uniform density, in smaller injection pressure, the shorter the forming time, injection molding injection system is better than the general products. For transparent, thin pieces, large plastic parts or high demand parts can show its advantage more, and with small models produce larger products.

(4) hot nozzle adopt standardization, seriation design, equipped with a variety of selection of the nozzle head, good interchangeability. Unique design and processing of electric heating circle, can achieve uniform heating temperature, long service life. Hot runner system is equipped with heat flow but, thermostat, etc., the design is exquisite, species diversity, use convenient, stable and reliable quality.

Application of hot runner system deficiencies

(1) the whole mould height increasing, by adding hot water but, mold the overall height increase.

(2) the thermal radiation is hard to control, is the biggest trouble of hot runner gating heat loss, is a major issue to solve.

(3) thermal expansion, heat bilges cold shrink is to consider when we design problem.

(4) the mold manufacturing costs have gone up, hot runner system standard accessories price is higher, affect the popularity of hot runner mold.

IML technology introduction

The IML Chinese name: mould insert molding Its process is very significant features are: surface is a layer of hardening of the transparent thin film, the middle is printed pattern layer, the back is plastic layer, because the ink caught in the middle, can make the product to prevent surface is scratched and friction resistance, and can keep the color bright not easy fade for a long time.

The  IML technology introduction

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Keywords: on IML IMD molding process

1. The concept of on IML

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 diagram below:

2, IML craft process

Cutting material - print - ink dry fixed - stick protective Film - flush positioning hole - thermoforming - cutting peripheral shape - material injection molding process is as follows: details are as follows: 1) cutting material: cut rolls of Film Film has good design size square piece, for printing, molding process.

2) print: according to the requirements of the ICONS and text made into a Film, on the square piece cut out good Film Film printing icon and text.

3) ink drying is fixed: square the printed Film Film placed in high temperature oven drying, purpose is fixed on IML ink.

4) stick protective Film: avoid rush in positioning hole process with flowers has printed Film Film surface, sometimes need to put a single or double protective Film.

5) blunt positioning hole: thermoforming positioning hole must be crossroads. The shear process sometimes prior to positioning hole punching.

6) thermoforming (high pressure or copper) : the printed film, after heating with high pressure machine or copper molding in preheating condition.

Shape: 7) shear periphery to forming good stereoscopic film scrap shear off.

8) material injection: after the molding and mold three-dimensional shape exactly the same as the film on the front mold, injection molding on IML products.

3，The advantages and disadvantages of IML process

Advantages:

1) the film production cycle is short, can perform multiple colour;

2) can change design and color in production;

3) is the outermost layers on IML FILM, screen printing ink, in the middle tier, and bright and clean appearance, more to touch the light, it has excellent resistance to scratch;

4) on IML production batch number is flexible, suitable for many kinds of small production

Disadvantages:

1) the early stage of the cycle is long;

2) easy to produce the film falls off, distortion, and so on and so forth;

3) the product defective rate is high.