|
|
|
Q: Why mould release agent?A:Demoulding agent is a kind of functional substance between the mold and the finished product, is to prevent rubber, plastic, elastomer or other materials of mold products, laminated products and other bonded to the mold or other surface, play a role of easy to break away from a class of processing additives. Due to the rapid development of injection molding, extrusion, calendering, moulding, laminating and other processes, the amount of demoulding agent is also greatly increased.
Brief introduction of mold release agent A demoulder is an interfacial coating applied to two surfaces that are easily adhered to each other to make the surfaces easily detachable, smooth and clean. Demoulding agent is used in glass fiber reinforced plastics, metal die casting, polyurethane foam and elastomer, injection molding thermoplastics, vacuum foamed sheet and extruded profile, etc. In moulding, sometimes other plastic fillers such as plasticizers leak out onto the interface and a surface remover is needed to remove it.
In theory, the release agent should have a high tensile strength so that it is not easily polished when in constant contact with the molded resin. This is especially true when there are abrasive mineral fillers or fiberglass reinforcers in the resin. Mold release agents should be chemical resistant so that they will not dissolve in contact with the chemical components of different resins (especially styrene and amines). Release agent should also have heat resistance and stress properties, not easy to decompose or wear; The release agent should be bonded to the mold and not transferred to the processed piece so as not to interfere with painting or other secondary processing operations.
Q:What are the types and uses of mold release agents?A:Type of mold release agent
1.Classification by usage: internal release agent, external release agent;
2.Classification by life: conventional release agent, semi-permanent release agent;
3.Classification by form: solvent-based release agent, waterborne release agent, solvent-free release agent, powder release agent, paste release agent
Release agent4.Classification by active substances:
①Silicon series -- mainly consists of siloxane compounds, silicone oil, silicone resin methyl branched chain silicone oil, methyl silicone oil, emulsified methyl silicone oil, hydromethylsilicone oil, silicone grease, silicone resin, silicone rubber, silicone rubber toluene solution,
②Wax series -- plant, animal, synthetic paraffin wax; Microcrystalline wax; Polyethylene wax, etc.
③Fluorine series -- best isolation performance, low pollution to mold, but high cost teflon; Fluorine resin powder; Fluorine resin coating
④Surfactant series -- metal soap (anionic), EO, PO derivatives (non-ionic)
⑤Inorganic powder series - talc, mica, clay, white clay, etc
⑥Polyether series - polyether and fat mixture, heat resistance is good chemical, used in some rubber industry with limited silicone oil. The cost is higher than that of silicone oil series.
Other water release agent containing masking agent: durable type release agent with masking agent water molecules: silicone + silicone system, more than 800 times a multi-layer composite mold release agent: halogenated hydrocarbon membrane + PE release agent + pva release agent aromatic polysulphone type release agent of mould processing release agent containing halogen polyether type release agent: reduce the vapor pressure, improve the decomposition temperature, does not cause electric contact carbonyl alkyl silane demoulding agent: stripping, improve the adhesive properties of water-based ink surface reaction type release agent: After being coated, the film is formed by chemical reaction and adhered to the surface of the mold. The above are some representative release agents. They have their own characteristics and can be used separately according to their uses. For example, backside treatment agents, peeling paper, anti-adhesive agents (telephone poles, telephone boxes, signboards, signs) used as fiber adhesive tapes, etc., anti-pollution agents (interior, exterior wall finishes, vehicles, roadblocks, rails, etc.) used to prevent residual adhesive around adhesives.
Characteristics of mold release agent
①Demoulding (lubricity) When forming a uniform film with complex shape, the size is accurate.
②Good demoulding continuity.
③The appearance of the forming is smooth and beautiful, not due to brush sticky release agent and lead to dust adhesion.
④Secondary processing is superior. When the release agent is transferred to the forming material, it has no adverse effects on electroplating, hot pressing, printing, coating, bonding and other processing materials.
⑤Easy to coat.
⑥Heat resistance.
⑦Pollution resistance.
⑧Good shape, high production efficiency.
⑨Good stability. Its physical and chemical properties are stable when used with the additives and materials.
⑩Nonflammable, low odor, low toxicity.
Properties of mold release agent
In theory, the release agent should have a high tensile strength so that it is not easily polished when in constant contact with the molded resin. This is especially true when there are abrasive mineral fillers or fiberglass reinforcers in the resin. Mold release agents should be chemical resistant so that they will not dissolve in contact with the chemical components of different resins (especially styrene and amines). Release agent should also have heat resistance and stress properties, not easy to decompose or wear; The release agent should be bonded to the mold and not transferred to the processed piece so as not to interfere with painting or other secondary processing operations.
Chemical principle of mold release agent
1.Polar chemical bonds interact with the mold surface to form an adsorptive film with regenerative force.
2.The siloxane bonds in polysiloxane can be regarded as weak dipole (Si+-O-). When the demoulder is spread on the surface of the mold and arranged in a single orientation, the molecule adopts a unique extended chain configuration.
3.The free surface is covered by the alkyl group in a dense stacking manner, and the demultifying capacity increases with the alkyl density. But when the alkyl group is in possession
Release agent
When the steric hindrance is large, the stretching configuration is limited and the demoulding ability is reduced.
4The molecular weight and viscosity of the demoulding agent are also related to the demoulding ability. The molecular weight is small and the spreading property is good, but the heat resistance is poor.
Selection and evaluation of mold release agent
There are three kinds of demoulding agents: inorganic, organic and high polymer.
Inorganic demultifying agent, such as talc powder, mica powder, clay, white clay and so on as the main components of the complex, mainly used as rubber processing film, semi-finished anti-adhesion agent.
Organic demoulding agents include fatty acid soap (potassium soap, sodium soap, ammonium soap, zinc soap, etc.), fatty acid, paraffin wax, glycerin, vaseline, etc.
The third type of demoulding agent is high polymer, including silicone oil, polyethylene glycol, low molecular weight polyethylene, etc., which have much better efficiency and thermal stability than organic demoulding agents.
Mold release agents are usually powder, semi-solid and liquid, powder and semi-solid can be like wax brush or hand on the surface of the mold. The liquid can be applied to the surface of the mold with tools such as spray or brush to form an isolation film. Liquid demoulding agent to spray is preferred.
The mould release agent filled by metal spray can is used in the developed countries. Due to the good sealing performance of the metal spray tank, it can avoid the oxidation of the demoulding agent or mixed with impurities, and ensure the purity of the demoulding agent when it leaves the factory. Large injection molding equipment installed in the room, the environmental temperature change is small, has no impact on the use of spray mold release agent. But the mold temperature of the die to be considered, to choose a good thermal stability of the release agent, the general requirements of the release agent thermal decomposition temperature is higher than the mold temperature. Otherwise, carbonization and chide will occur. High-grade products and the need for secondary processing (such as painting and printing) to choose suitable for the secondary processing of the release agent. To prevent environmental pollution, it is necessary to choose non-flammable, odor and toxicity of the mold release agent. Economy is an important factor in the selection of mold release agent. Poor quality demoulding agent will cause cracks and wrinkles on the product surface, affect the appearance of the product and the service life of the mold, and bring about environmental pollution. Choose high quality spray demoulding agent, the price is higher, but the comprehensive economic benefit is high.
To sum up, the selection points of mold release agent are as follows:
①The demoulding property is good, the surface tension of spray demoulding agent should be between 17 ~ 23 N/m. Release agent
②Has the heat resistance, does not produce carbonization decomposition when heated.
③Stable chemical properties, no chemical reaction with molding products.
④It does not affect the secondary processing property of plastics.
⑤Do not corrode mold, do not pollute product, little odor and toxicity.
⑥Smooth and beautiful appearance;
⑦Easy coating, high production efficiency;
Cause analysis and solution of surface blemish on finished products
－Spraying uneven cause: improve coating;
－Spraying flow causes: adjust the spraying amount;
－Wiping causes: select the hardness of mold release agent and solvent system;
－Evaporation caused by: different solid solubility or solvent solubility, orange peel phenomenon, solid precipitation during evaporation can not form a uniform skin film, adjust dispersant and solvent;
－Resin flow caused by: easy turning point appearance, mold design overcome;
－Bubble caused: there are many small bubble pits on the surface of the product, raw materials or demoulding performance of demoulding agent, demoulding agent and mold between the air or mold surface roughness, etc., improve the hardness of demoulding agent;
－Shrinkage of products caused by: shrinkage stress over tensile strength, concentric markings, the main choice of material shrinkage rate, injection pressure and other adjustments;
－Die material heat capacity caused: die reinforcement material heat capacity distribution is different, storage heat is different, high temperature response is fast; Or high temperature melting release agent caused by the mold material.
Common solvent diluents for reference
1. Dichloromethane:
CH2Cl2, Boiling point 39.75, relative density 1.326, no flash point, surface tension 28.12mn /m, chemically stable, 290-degree non-oxidation or cracking, strong solubility, no combustion; High concentration of steam causes poisoning and greenhouse effect.
2. Petroleum ether:
It is a low boiling point fraction of petroleum and a mixture of lower alkanes. According to the different boiling points, it is divided into three types: 30-60 ° C, 60-90 ° C and 90-120 ° C. It has low boiling point, high volatility and toxicity similar to that of lower alkanes.
3. 120 # Gasoline:
C4-c11 is a mixture of alkanes, alkenes, cycloalkanes and aromatic hydrocarbons. Its main components are pentane, hexane, heptane and octane. It is highly volatile and has a pungent smell.
4. Naphtha:
Aromatic hydrocarbon mixtures obtained from coal tar light oil distillate, boiling point 120-200℃, composed of toluene demoulding agent, ethylbenzene, etc., can avoid fire and affect nerves.
5. Heptane:C7H16, boiling point 98.4℃, chemically stable, flash point -4℃, surface tension 19.6mN/m, low toxicity.
6. Xylene:C8H10, isomer, distillation range around 140℃, density around 0.86, high flash point flammable, low toxicity, has an impact on the skin.
|
Contact
