Friday, November 10, 2017

Injection Moulding Process

Injection moulding is a two step cyclical process: (a) melt generation by a rotating screw, and (b) Žfilling of the mouldwith molten polymer by the forward ramming of the screw (called a reciprocating screw), followed by a very short packing stage necessary to pack more polymer in the mould to offset the shrinkage after cooling and solidiŽ cation. The material is held in the mould under high pressure until it has solidiŽfied sufŽ ciently to allow ejection.
Tube ExtrusionPolymer injection molding has certain similarities to the die casting process of metals, in which molten metal is forced under high pressure into a steel mould or die. The metal, as the polymer, is pressed into all the crevices of the mould and the pressure is held while the metal freezes.
In polymer injection moulding, the melt path into the mould starts with a sprue, and splits off into individual runners each feeding one of the multiplicity of mould cavities through a gate. Moulds can contain over 100 cavities, each producing a part per injection cycle. Cycle times range from a few secondsto over a minute. Numerous productsranging from boat hulls, lawn chairs and appliance housings to radio knobs and bottle caps are injection moulded. Very high shear rates arise in injection moulding operations (usually up to 104 s21 ) and, to limit temperature increases from viscous heating and also to facilitate easy filling, low viscosity thermoplastic polymer grades are used.
Injection moulding machines are rated by the size of their clamping systems, which are hydraulic, electrical or mechanical toggle systems used to hold the mould closed with sufŽficient force to resist the injection pressure. Machines available usually range from 5 tons for a shot of ~10 g to 5000 tons for shots of more than 50 kg (shot is the total amount of material pumped into the mould in a cycle, including that in the sprue, runners and cavities). Some bigger machines have also been built for the production of very large moulded products. Micromoulding, in which the shot size is below 1 g, is recently finding increased use in biomedical and nanotechnological applications.
Simulation software is used extensively in the design of injection moulds, because of the ability of the Hele – Shaw flow approximation to describe reasonably well the mould Žfilling process. More recently, however, three-dimensional models of flow simulation have come into use. Economics also provide an incentive for the use of software, as moulds can be extremely expensive to make, so minimising trial and error procedures on the factory  oor is desirable. The software is used to design the part cavities, to balance runners, to visualise the filling process, and to predict orientation, shrinkage, warpage and weld lines in the product.
Among the challenging problems faced in computer simulation is the prediction of shrinkage and warpage. Shrinkage is the difference in dimensions between the mould and the cooled moulded part. The main cause is the density increase which occurs as the melt freezes. Crystalline poly- mers such as polyamide (PA, nylon), high density PE, PET and PP give the worst problems, with shrinkages of 1 – 4%. Amorphous polymers such as PS, PMMA and PC have fewer problems, shrinking only 0.3 – 0.7%. Warpage is caused by the density changes mentioned above, and orientation imparted to the part during cavity Žfilling and packing, decidedly in a non-uniform manner.
Gas assist injection moulding involves the injection of nitrogen with the plastic, which creates a hollow void in the moulded part.This allows large parts to be moulded with lower clamp tonnage and signiŽ cant material savings. This innovative process started in the 1980s and its use is rapidly growing.
The process of reaction injection moulding (RIM) involves the injection of low viscosity liquids, which become reactive when mixed and polymerise within the mould.The advantage of this processis that the pressures are low owing to the low viscosities. A disadvantage is the requirement to handle highly toxic substances. Although initial projections called for signiŽficant growth in RIM, this did not materialise. In fact, some manufacturers of automotive parts by RIM have switched to conventional injection moulding.


Wednesday, November 8, 2017

Extrusion machines for PTFE Medical tubing

Sunkoo PFG150 Single Screw Extruder Features:Vertical Ram Extruder for PTFE tube;Ram extruding machine for PTFE tube;Using for Pre-sintering PTFE material;Suit for new PTFE material or Recycle PTFE material;Rangeof diameter PTFE Extrusion 20-150 mm, Heating zones 5 zones; Automatic.

Sunkoo PFG150 Tube Extruder is to extrude PTFE/UHMWPE Tubes. It is designed using latest technology, fully reliable and easy to operate for customers. Performance in terms of production and working hour capacity is competitive to other machines. Low maintenance is required , giving high production in market.
  • Save time and money.
  • PLC design and easy to operate.
  • Long time span. No heating effect during operation.
  • With latest technology and optimized design.
  • Min – Max Dia:20-150mm.
  • Production Per Hour: 10+ kg/h.
  • Unlimited Length
  • Automatic operation.
  • 5 Heating Zones

PTFE molding gasket machine

Gaskets Press Machine Features:Efficiently producing: 300pieces/h(large size);More energy saving: the total power only 5KW;More friendly to environment: no PTFE powder splashing but powder output automatically;More precise: producing gaskets by controlling the power quantity;More time saving : the power cut off automatically while the production number set up;Longer working life : no heat while working.

PTFE gaskets are used in many industrial applications, especially the following:
  • Compressor – High temperature and surface-wear resistant sealing gaskets.
  • Electric Motor – Sealing gaskets for components that require corrosion-resistance, exposure to high and low temperatures and high surface wear.
  • Medical Component – Seals for electronic instrumentation using materials that provide secure seals and long product life. Specialty gaskets, especially miniature sizes, are required for many medical devices.
  • Petrochemical – Gaskets for process equipment that are resistant to corrosive fluids, temperature extremes and surface wear.
Our staff works closely with each customer to ensure that every job meets your exact requirements and our high quality standards. Contact Sunkoo today!
Please note: Any technical data provided is for informational purposes only. Before specifying this machine for your application, please let us know you requirement to better advise suitable machine for you.

Monday, November 6, 2017

Machine Teflon Tape

Thread seal tape (also known as PTFE tape or plumber’s tape) is a polytetrafluoroethylene (PTFE) film for use in sealing pipe threads. The tape is sold cut to specific widths and wound on a spool, making it easy to wind around pipe threads. It is also known by the genericised trade-name Teflon tape; while Teflon is in fact identical to PTFE, Chemours (the trade-mark holders) consider this usage incorrect, especially as they no longer manufacture Teflon in tape form.Thread seal tape lubricates allowing for a deeper seating of the threads, and it helps prevent the threads from seizing when being unscrewed.The tape also works as a deformable filler and thread lubricant, helping to seal the joint without hardening or making it more difficult to tighten,and instead making it easier to tighten.

PTFE is widely used in a variety of needs, such as: anti-acid and organic solvents, which itself has no toxic to people, but one of the raw materials used in the production process of ammonium perfluorooctanoate (PFOA) is considered likely to have a carcinogenic effect.
Large relative molecular of PTFE, the lower one as hundreds of thousands, while higher one can up to one million or more (degree of polymerization of 104 orders of magnitude, while the polyethylene only 103). Degree of crystallinity is generally 90 to 95%, a melting temperature of 327 ~ 342 ℃. Molecule CF2 unit in PTFE arrange by zigzag shape, because the fluorine atom radius larger than the hydrogen, so the adjacent CF2 units can not cross exactly trans orientation, but form a spiral twisted chain, fluorine atom covering almost the entire polymer chain surface. This molecular structure explains various properties of PTFE. At temperatures below than 19 ℃ to form 13/6 helix; phase transition at 19 ℃, slightly unravel the molecular to form 15/7 helix.
Though the perfluorocarbon carbon – carbon bond and carbon – fluorine bonds are broken need to absorb energy 346.94 and 484.88kJ/mol, but PTFE depolymerization energy generate 1mol tetrafluoroethylene only need 171.38kJ. So in the pyrolysis, PTFE mainly depolymerizate tetrafluoroethylene. PTFE at 260,370 and 420 ℃ the weight loss rate (%) were 1×10-4, 4×10-3 and 9×10-2 per hour.
Our engaged in manufacturing PTFE Teflon tape machine, which also called as PTFE tape machine, Thread seal tape machine, more than 20 years, now honor ISO9001 and CE certificate obtained. We are the very first one who manufacture PTFE Tape Machine in China. Not only could we provide you the production line, but also provide raw material. The main machines include: Mixer, Calender, Slitter, Pressing Machine, Oven, Wrapping machine etc..
Range of final PTFE thread seal tape:
Thickness: 0.05-0.3mm or more (according your requirement);
Width: 8mm, 10mm, 12mm, 19mm, 25mm or others, according to your requirement;
Length: 8m, 10m, 12m, 15m, 18m, 20m ,25m, 40, etc..according to your requirement.

Sunday, November 5, 2017

PTFE Etching

Etching is a chemical process that removes the fluorine atoms from the surface layer of the fluoropolymer. This surface layer is so thin; it is most conveniently measured in Angstroms. Once the fluorine atoms are removed, the carbon atoms left behind in the etched polymer quickly forms temporary bonds with atoms from the air, such as oxygen, nitrogen, and sometimes even hydrogen. Since these bonds are much weaker, the carbon atoms are still reactive, reducing the surface lubricity and allowing for a more bondable product. Because of the loss of carbon-fluorine bonds, once the surface of your fluoropolymer is etched, the properties of the etched area are changed. One will no longer have the lubricous and low energy surface that is expected from a fluoropolymer. Instead, one will have a wettable, bondable, frictional surface upon which to glue, mold, or print onto your product.
Etching will only affect the chemistry of the surface with which it comes in contact. The properties of your fluoropolymer are kept intact not only underneath the etched surface, but on the entire remaining unetched surface as well, meaning that the etched product’s bulk properties are unaffected by this process.

The results of the etching are not permanent, however. If left unused for long periods of time or stored incorrectly, the etched part regains its initial low bondability.
Chemical treatment of PTFE is almost impossible because PTFE is completely inert against chemical attack of all conventional organic solvents, acids and lyes. The only chemical substance to attack PTFE is a solution ao alcaline metals which is able to etch PTFE forming alcaline fluorides. The process is very dangerous and all substances involved are extremely hazardous.
A perfect alternative is plasma treatment by hvdrogene used for process gas in a low pressure plasma. Hydrogene ions and radicals react with fluorine atoms to Hydrofluoric acid and leave unsatturated carbon bindings which provide perfect links for organic molecules of coating substances.
The chemical etching process causes a reaction between the fluorine molecules in the surface of the material and the sodium solution. The fluorine molecules are stripped away from the carbon backbone of the fluoropolymer, which leaves a deficiency of electrons around the carbon atom. Once exposed to air, hydrogen, oxygen molecules and water vapour restore the electrons around the carbon atom. This results in a group of organic molecules that allow adhesion to take place.

Friday, November 3, 2017

An extrusion machine for PTFE

Sunkoo’s enormous strength comes from a wonderful combination of its highly efficient and professional management and a dedicated workforce of qualified and experienced engineers and technicians and marketing personnel, which in turn, leads to world-class manufacturing, testing and R & D , besides meeting requirements of clients’ specifications globally.
Our comprehensive array includes PTFE & UHMWPE Rods Ram Extrusion Machines, PTFE & UHMWPE Ram Extrusion Machines, PTFE Molding Machines, PTFE Gasket Machines & Sintering Furnace/Ovens.

What is PTFE?
Polytetrafluoroethylene (PTFE) is a synthetic material accidentally invented in the late 1930s while a chemist was endeavoring to develop a new type of perfluorethylene-based refrigerant. Rather than achieving a chlorofluorocarbon, the scientist was surprised to find that the perfluorethylene used in the process reacted with the iron content of its container and polymerized under pressure. Less than a decade later, this new material was being distributed on a commercial scale and was eventually patented under the name Teflon®. It would be another 20 years before this material would hit the frying pan and become known as the first non-stick coating for cookware, however. In fact, this material was used for a variety of other purposes at first.
PTFE also possesses very low frictional properties, which is expressed as frictional coefficient. This measurement is relative and differs according to the materials brought into contact to generate or simulate friction. In terms of plastics, friction is usually observed against polished steel. To put the low friction coefficient of PTFE into proper perspective, it is the only known synthetic surface material to which the toe pads of a gecko fail to stick. This quality makes it suitable for manufacturing parts that need to resist friction, such as gears and ball bearings.
This material was eventually introduced to American households by Marion Trozzolo, founder of Laboratory Plasticware Fabricators. While Trozzolo had been producing Teflon®-coated scientific tools for a number of years, he became inspired by a French engineer who found it such an effective non-stick coating for his fishing gear that he later treated his wife’s pots and pans with it. While this experiment led to the production of cookware known as Tefal (T-Fal®) in France in the mid-1950s, Trozzolo became the first U.S. producer of Teflon®-coated cookware. In fact, “The Happy Pan,” launched in 1961, earned a place of historical significance in the Smithsonian Institute and Trozzolo a name of distinction in the Plastics Hall of Fame.
Extrusion is a shape forming manufacturing process that involves forcing material into a die to make other shapes with that matetial. It’s like play dough. Imagine having play dough and pushing it through one of those tools with all the holes. You end up with play dough spaghetti. This is an example of extrusion. You can achieve a lot of different stock sizes and lengths by extruding.

Thursday, November 2, 2017

Horizontal Extrusion

Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms parts with an excellent surface finish.

Drawing is a similar process, which uses the tensile strength of the material to pull it through the die. This limits the amount of change which can be performed in one step, so it is limited to simpler shapes, and multiple stages are usually needed. Drawing is the main way to produce wire. Metal bars and tubes are also often drawn.
Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). The extrusion process can be done with the material hot or cold. Commonly extruded materials include metals, polymers, ceramics, concrete, modelling clay, and foodstuffs. The products of extrusion are generally called “extrudates”.
There are many different variations of extrusion equipment. They vary by four major characteristics:
  1. Movement of the extrusion with relation to the ram. If the die is held stationary and the ram moves towards it then it is called “direct extrusion”. If the ram is held stationary and the die moves towards the ram it is called “indirect extrusion”.
  2. The position of the press, either vertical or horizontal.
  3. The type of drive, either hydraulic or mechanical.
  4. The type of load applied, either conventional (variable) or hydrostatic.
A single or twin screw auger, powered by an electric motor, or a ram, driven by hydraulic pressure (often used for steel and titanium alloys), oil pressure (for aluminium), or in other specialized processes such as rollers inside a perforated drum for the production of many simultaneous streams of material.