parts tooling, Rubber die making, plastic injection mold manufacturing service

parts tooling, Rubber die making, plastic injection mold manufacturing service
parts tooling, Rubber die making, plastic injection mold manufacturing service

Service Details:

  • Brand:Kayou
  • Serial Number: M-0178
  • Country of Origin:Shenzhen, China
  • Certificate:ISO9001

Payment & Shipping Terms:

  • Price Quote:Negotiable
  • Minimum Order: 1
  • Average Delivery Time:25 days
  • Payment Method:T/T
  • Package Details:Wooden Case
  • Ability to Supply:5 Set/per month
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parts tooling, Rubber die making, plastic injection mold manufacturing service

Description

parts tooling, Rubber die making, plastic injection mold manufacturing service

A unified method is used to determine the fluidity of plastics. There are usually two methods for measuring the melt index and spiral length of thermoplastics. The melt index method is to measure the mass of the tested plastics through a standard capillary (2.09mm diameter discharge hole) within 10 minutes at a constant temperature and load. The value is called melt index. It is a quantity reflecting the fluidity of plastics in the melting state. The greater the melt index, the better the fluidity. The unit of melt index is expressed in g/10 min. Usually expressed as MI. According to the requirements of die design, the fluidity of thermoplastics can be divided into three categories.

Plastics with good fluidity, such as polyamide, polyethylene, polystyrene, polypropylene, cellulose acetate and polymethylpentene, etc.

Medium fluidity plastics such as modified polystyrene, ABS, AS, polymethyl methacrylate, polyformaldehyde and chlorinated polyether, etc.

Plastics with poor fluidity, such as polycarbonate, hard polyethylene, polyphenylene ether, polysulfone, polyaromatic sulfone and fluoroplastics, etc. There are three main factors affecting the fluidity of plastics.

The fluidity of plastics increases with the increase of material temperature, but the influence of material temperature on the fluidity of different plastics is different. The fluidity of polystyrene, polypropylene, polyamide, polymethyl methacrylate, ABS, AS, polycarbonate, cellulose acetate and other plastics has great influence on temperature change, while the fluidity of polyethylene and polyformaldehyde is less affected by temperature change.

With the increase of pressure injection pressure, the shear force and fluidity of the melt increase, especially for polyethylene and polyformaldehyde. However, excessive pressure will cause stress in the plastic parts, and will reduce the melt viscosity, forming a flash.

The form, size, layout, surface roughness, cross-section thickness of runner, cavity form, exhaust system, cooling system design, melt flow resistance and other factors of the casting system of die structure directly affect melt fluidity. The fluidity decreases when the melt temperature decreases and the flow resistance increases (e.g. the wall thickness of the plastic part is too thin and the sharp corner is used at the corner).

The chemical structure of thermosensitive plastics may change under the action of heat. Some plastics with poor thermal stability will have the characteristics of decomposition, degradation and discoloration when the material temperature is high and the heating time is long. This sensitivity to heat is called thermosensitivity of plastics. Plastics with high thermal sensitivity (i.e. plastics with poor thermal stability) are usually referred to as thermosensitive plastics. Such as rigid polyvinyl chloride, polytrifluorochloroethylene, polyformaldehyde and so on. It is easy for this kind of plastics to decompose, decompose or superheat in the process of forming at low temperature, or in the case of long heating time, thus affecting the performance and surface quality of the plastics.

Thermosensitive plastics melt will produce various degradation products when thermal decomposition or thermal degradation occurs. Some degradation products will stimulate, corrode or have certain toxicity to human body, mould and equipment; some degradation products will also be catalysts to accelerate the degradation of the plastics, such as the degradation of polyvinyl chloride to produce hydrogen chloride, which can further aggravate the degradation of polymers. In order to avoid thermal degradation of thermosensitive plastics in the process of processing and moulding, thermal stabilizers can be added to the plastics in the design of moulds, selection of injection moulding machines and moulding, and appropriate equipment (screw injection moulding machine) can be used to strictly control the moulding temperature, moulding temperature, heating time, screw speed and back pressure. Equipments and moulds should adopt anti-corrosion measures to remove degradation products in time.

 

 

 

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parts tooling, Rubber die making, plastic injection mold manufacturing service

 

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FAX :
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