Rubber moulds and PVC moulds are widely used all over. The physical and chemical properties are quite different from each other but rubber and PVC alone possess its own characteristics.
Different types of moulding process are casting, injection moulding, blow moulding, compression moulding, rotational moulding.
Know more about Rubber…
Rubber exhibits its own unique features and physical properties. Mullins effect and Payne effect are the stress-strain behaviour exhibited by rubbers. It is often moulded as hyperelastic. Rubber block suppliers comment rubber strain crystalize. Natural rubber is pliant to vulcanisation and delicate to ozone cracking due to the presence of a double bond in each repeat unit. Turpentine and naphtha (petroleum) are the two main solvents for rubber block manufacturers in Indonesia. Since 1764, the former has been in use when Francois Fresneau made the discovery. In 1779 Giovanni Fabbroni lifted the discovery of naphtha as a rubber solvent. The rubber material is finely divided by shredding prior to its immersion, it does not dissolve easily. While rubber is transported from its collection site an ammonium solution can be used to prevent the coagulation of raw latex. Expansion and contraction property of rubber make it stand out from other materials.
The moulding process of rubber is like pressing a block of rubber into a rubber molding metal cavity. By activating a channel reaction the rubber is then exposed to heat. Usually, allrubber block suppliers use heat and pressure method to form molded rubber products. Compression molding, injection molding, and transfer molding are the three rubber moulding process.
- Compression moulding is done by inserting a sheet inside the mould. It is the simplest moulding method. The rubber is forced to take on the shape of the mould by pressing the two halves of the rubber into the sheet. It is the crudest and oldest form of rubber moulding. In the final stage, it often produces rubber pieces with errors in the final shape. The advantages of compression moulding are:
- Best for small production
- Good for big parts
- Low costing tool
- The material doesn’t have to pass through gates, runners or sprues.
- Injection moulding is heated until it has a toothpaste-like consistency. It is the most precise way to shape rubber. Injecting into a mould the rubber is allowed to harden. Rubber paver mould concrete casting in Cambodia create strong rubber pieces in this way. They retain the exact shape of the mold with few inconsistencies. The advantages of injection moulding are:
- Minimum wastage of material
- Flexibility in colour and material
- Fast production
- Labour cost is low
- Design flexibility
- Transfer moulding is a mix between injection moulding and compression moulding. A large slug of rubber is placed into a pot in this process. More than compression pieces the rubber pieces made by transfer moulding possess high quality but it is less than injection pieces.
- When compared to traditional compression molding they have shorter production cycle times
- Advantages for coloured or translucent compounds
- Supports high precision molding applications
- Over-molding and molding of complex geometries are supported in closed mould transfer.
Get a little information about PVC..
PVC is one among the category of thermosetting plastics which can be softened by heating. PVC is the material which is long-term resistant to degradation and oxidation. In Europe, PVC is usually used for flooring, artificial leather, and decorative sheets. It is a natural resource derived from 57% chlorine and 43% carbon. This is an excellent resistant to fire, splintering, decaying, and insect infestation. Because of its cheap rate they are often used for drip edges, kick-boards, table boards. PVC is used for interior as well as exterior applications.
Properties of PVC
- 1. Mechanical property
PVC cover blocks possess high hardness. Its mechanical properties upgrade with the increasing molecular weight but it gets decreased with increase in temperature. Rigid PVC possess very good mechanical properties, 1500-3000 MPa is the range of elastic modulus and elastic strength of soft PVC is 1.5-15 MPa.
2. Thermal and fire properties
Since its heat stability ios very low it needs a heat stabilizer during the process to ensure the product’s properties. When the temperature reaches 140 °C PVC starts to decompose with melting temperature starting around 160 °C. It has good flame retardancy. The LOI(linear oxygen index) is minimum(up to 45 or more).
3. Electrical properties
The electrical insulating property is subordinate to non-polar polymers like polyethylene and polypropylene because of its higher polar nature. It is a polymer with good insulation properties. It has high dielectric loss tangent value, dielectric constant, and volume resistivity but poor corona resistance. Generally, it is packed for low frequency insulation materials and medium or low voltage.
4. Chemical properties
PVC is used in sewerage piping as it is resistant to salts, acids, fats, bases, alcohols. uPVC and plastified PVC are less resistant to solvents. Some are resistant to fuel and paint thinners. May some solvents expand it or distort it but not liquefy PVC. Whereas some may damage it like acetone or tetrahydrofuran.
- Different types of PVC
- How is PVC made?
PVC moulds for paver blocks in Kuwait are extracted from three emulsion processes. They are:
1. Suspension Polymerization
It is a heterogeneous ultra polymerization process that uses mechanical commotion to blend the mixture of monomers. It is one among the widely used polymerization techniques. Purification and processing of the polymer is much easier than compared to emulsion polymerization. Here, the final product is a 100% solid resin.
2. Emulsion Polymerization
Like vinyl acetate, vinyl chloride, chloroprene, acrylamide, acrylates, and methacrylates it is the most important methods for the polymerization of a large number of monomers. It is rapid than bulk or solution polymerization at the same temperature. Harkins proposed the first hypothesis of the mechanism of emulsion polymerization.
3. Bulk Polymerization
Over other polymerization techniques, mass polymerization has several other advantages. As the final product is 100% solid resin it is a very environmental friendly polymerization which does not require any purification method. Because of the lower heat of polymerization and reactivity, this is much more suited for step-growth polymers. Depending on the solubility of the growing polymer chains in the monomer they can proceed either homogeneous or homogeneous.
- Is PVC toxic?
when it is burned it emits hydrogen chloride which can pose a health hazard. PVC free electrical wire insulation is sometimes preferred in applications where the likelihood of fire is high.
- What are the advantages of going with PVC?
- It is relatively inexpensive and readily available.
- It is very dense and hard.
- It resists impact deformation very well relative to other plastics.
- It possesses very good tensile strength.
- It is well resistant to chemicals and alkalis.
- Common applications of PVC
- Due to its low-cost PVC is widely used in the sewage pipe.
- It chemical and biological resistant and provides easiness in joining.
- It is a popular material for window and door.
- It is very flexible
- Used as a wire insulator
Make a little comparison between the paver mold and rubber mould
|Property||PVC Paver Mould||Rubber Paver Mould|
|Colouring||They can be changed very easily||They cannot be changed easily|
|Acid resistance||Possess excellent acid resistance.||Not acid resistant|
|Alkaline resistance||They are excellent alkaline resistant||Not alkaline resistant|
|Shining property||They give more shining||They are less shiny|
|Weight||They are less in weight||They weigh more weight|
|Price||They are less expensive||They are more expensive|
|Black carbon spot on concrete paving stones||It is not possible with PVC moulds||It is possible with rubber paver mould|