Probably the most widely prevalent type, pvc granule is manufactured by polymerizing droplets of Vinyl Chloride monomer suspended in water. When Polymerisation is finished, the slurry is centrifuged and also the PVC cake is gently dried by special heating systems so as not to subject the unstabilised resin to heat degradation. Particle dimensions of the resin ranges from 50-250 microns and have porous popcorn like structures which readily absorbs Plasticisers. The structure of your PVC particles could be modified by selecting suitable suspending agents and Polymerisation Catalyst. Less porous types are extensively employed for our prime volume Rigid or Unplasticised PVC applications like PVC Pipes, Windows, Sidings, Ductings. Suspension grades of the coarser particle size and extremely porous structures absorb vast amounts of Plasticiser forming a dryblend at temperatures only 80oC.The greater porous types are used in Plasticised applications like Cables, Footwear, Soft Calendered Sheeting and Films etc.
Emulsion Polymerised PVC is really what Paste Grade Resin is and that is almost exclusively utilized for Plastisols. Paste grade resin is a very fine particle size PVC made by spray drying an Emulsion of PVC in Water just like how milk powder is produced. Paste grade resin needs a lot more energy to create which is considerably costlier than Suspension resin. The paste grade resin carries the emulsifying chemicals and catalysts by using it. It can be therefore less pure than Suspension Polymerized or Bulk Polymerized PVC. The Electrical properties of Paste grade resin plastisols are therefore much poorer than Suspension Resin Compounds. Clarity is poorer than Suspension or Bulk PVC. Paste grade resin is compact in structure, and fails to absorb much Plasticiser at room temperatures. Temperatures more than 160-180oC are needed to drive the plasticer into the Resin during curing. Paste grade Resin is extensively employed for Cushion Vinyl Floorings of wide widths. Different layers of specially formulated pastes are coated either over a suitable substrate (Direct Coating) or on Release Paper (Transfer coating). The layers are fused continuously in long ovens and rolled up after release paper is stripped off. The rolled good flooring could have a tough semitransparent wear layer over printed and foamed layers which can be sitting along with highly filled base coats to develop the thickness. Many extremely attractive and rich effects are possible and they represent the higher end of Vinyl Flooring.
Bulk Polymerisation provides the purest type of rigid pvc compound as no emulsifying or suspending agents are employed. They may be mainly used in transparent applications. They are mainly presented from the lower K value groups, as Unplasticised PVC Foils for Blister Packaging and other Calendered/Extruded Transparent films are the best processed from lower K Value grades. Refinements in Suspension resin technology has edged out Bulk PVC in the recent past.
Vinyl Chloride is copolymerized with comonomers like Vinyl acetate give a range of resins with unique properties. PVAc or Copolymer of Vinyl Chloride and Vinyl acetate is the most essential. The best solubility in solvents of PVAc can make it the prime choice for Vinyl Printing Inks and solvent cements. You will discover a special putting on PVAc in Floor tiling which is the resin of choice for Vinyl Asbestos tiles. The Resin is actually a binder rather than main ingredient. With Copolymer Resin it is actually easy to manufacture floor tiles with Fillers like Asbestos and Calcium Carbonate making up just as much as 84% using the Copolymer along with other compounding additives as little as 16%. Such high levels are certainly not possible with Suspension resin as the melt viscosity is a lot higher and cannot coat and encapsulate such high quantities of inert filler. Special callendering trains will be required for Vinyl asbestos tiles. However with Asbestos falling out favour, such products have slowly died out.
PVC Resins are classified by their K-Value, an indicator from the molecular weight and amount of polymerization.
• K70-75 are high K value resins that gives best mechanical properties but are tougher to process. That they need more plasticizer for same softness. Good performance Cable insulations in Suspension resin and tough coatings for Conveyor belts, Industrial Flooring and similar top end applications in Paste grade are a couple of popular application. This is the costliest.
• K65-68 are medium K value resin which are the most widely used. There is a good balance of Mechanical properties and processibility. UPVC (Unplasticised or Rigid PVC) is manufactured out of the less porous grades while Plasticised Applications are the best created from the better porous grades. There is a lot of grade choice because they cater to nearly all PVC applications. Due to the sheer volume this group of PVC resins are priced the cheapest.
• K58-60 are low K-value ranges. Mechanical properties are lowest, but processing is easiest. Many challenging to process applications like injection moulding, blow moulding and Clear Calendered packaging film are made of the lower K value ranges. Costs are higher than Medium K Value Resins.
• K50-55 are special resins which dexopky06 personalized for some demanding applications. Interesting ones are Battery Separator Resins and Blending resins used along withPaste Grade resin to minimize costs. Processing is easiest.
As PVC is 56% Chlorine, it is amongst the few Polymers that happen to be self extinguishing, as Chlorine is really a strong Flame inhibitor.
Plasticisers make the hard PVC resin softer. Primary plasticizers have good compatibility with PVC resin and can be absorbed in big amounts. In special cases as much as 140-150 PHR of Primary plasticiser may be gelated into PVC for super soft products. Nearly all Plasticisers are liquids and must be absorbed in Suspension resin in heated mixers. High Speed mixers (which generate frictional heat while mixing) are typically the most popular types of dryblending equipment. Heated Ribbon blenders and Sigma mixers are merely used when extremely high Plasticiser levels are needed.
You will discover a wide array of Primary plasticizers for clear pvc granule. This discussion will be restricted to the most popular, the Phthalate Esters. Phthalic acid is reacted with various alchohols to produce a household of Phthalate plasticizers that Di Octyl Pthalate (DOP) is considered the most popular. Other important Primary Plasticisers are DOA & DOS (for low temperature applications), Trimellitates (for high temperature applications and Polymeric Plasticisers (High permanence).