What is PVC resin
Polyvinyl chloride resin, commonly known as PVC resin , is a thermoplastic resin that softens when reheated. The general term for this standard polymer is vinyl. PVC granules are often available in powder form and are highly resistant to degradation by oxidation and atmospheric reactions. In its raw state, it appears as a white powdery solid.
PVC is composed of 57% chlorine and 43% carbon. The process of obtaining PVC resin granules is almost petroleum-independent, so it is considered one of the more renewable plastics.
PVC resin is divided into two categories based on its appearance and flexibility:Rigid PVC: use in constructionSoft PVC: The granules are softened by adding a plasticizer.
PVC suspension resin is made by polymerizing vinyl chloride monomers. After the polymerization process.
PVC resin granules fall into four categories:
Suspension PVC: This process is very cheap and about 80% of PVC resin is made by this process.
Emulsion PVC: This process produces finer particles and the product is mainly used for the production of plastisols.
Bulk polymerized PVC: No emulsifiers or additives are used in this process. This helps create the purest form of PVC
Copolymer PVC: This process is used to give special properties to PVC by polymerizing the granules together with other comonomers. Vinyl floors fall into this category
What is PVC Suspension Resin
PVC suspension resin is a polymer made from vinyl chloride monomer. Widely used in building, construction, automotive and medical industries. This PVC suspension resin considers the environment and public safety.
Polyvinyl chloride (PVC)’s many properties make it ideal for various applications. Biologically and chemically stable. Durable and stretchy. Adding a plasticizer can make it softer and more flexible. Downstream applications may require proper registration and/or approval. Possible uses of polyvinyl chloride are listed below.
Pipe – About half of India’s polyvinyl chloride is used to make a pipe for municipal, construction, and industrial uses. Its lightweight, high strength, low reactivity, and resistance to corrosion and bacteria make it particularly suitable. Additionally, PVC pipe can be fused in a variety of ways, including solvent-cement types, adhesives, and heat-sealing to create permanent, leak-proof joints. Piping is the world’s largest single application for PVC. It is also used in window and door frames, gutters and downspouts, and double-glazed window frames.
Residential and Commercial Siding – Rigid PVC is used to manufacture vinyl siding. Available in a variety of colours and finishes, this material is used as an alternative to wood and metal. It is waterproof, weatherproof, and low maintenance. It is also used in window and door frames, gutters and downspouts, and double-glazed window frames.
Packaging – PVC is widely used as stretch and shrink wrap protective film, laminated film with polyethylene, rigid blister pack, food, and film packaging. It can also be blown into bottles and containers. PVC acts as a microbial and water-repellent barrier to protect food, household cleaning products, soaps, and toiletries.
Wiring Insulator – PVC resin is used as an insulation and flame retardant for electrical wiring. The wires are coated with resin, and the chlorine acts as a scavenger, insulating and reducing the spread of fire.
Medical – PVC is used to manufacture blood and IV bags, kidney dialysis and transfusion equipment, cardiac catheters, endotracheal tubes, artificial heart valves, and other medical devices.
Automotive – PVC suspension resin is used to make body-side mouldings, windshield system components, interior trim, dashboards, armrests, floor mats, wire coatings, wear coatings, adhesives, and sealants.
Consumer Goods – Rigid and flexible PVC are used in modern furniture design, air conditioners, refrigerators, telephone systems, computers, power tools, electrical cords, garden hoses, clothing, toys, luggage, apparel, vacuum cleaners, and credit card seats. PVC can be blended with other plastics to customise product properties such as colour, hardness, and abrasion resistance. This method allows the manufacturer to determine the individual look and feel of the final product.
How PVC Suspension is Different From PVC resin
Each S PVC resin is designed and manufactured to meet specific application needs, such as making rigid or flexible products.
However, not all manufacturers have the same expertise or commitment to optimising product properties. This is reflected in the varying performance of different PVC suspension resins when used in the same manufacturing process.
If a vinyl converter has only one supplier of S PVC resin , its process conditions and operational and management practices are usually “adapted” to that resin, and objectively matched with resins from other manufacturers. comparison becomes difficult.
However, with the current globalised market and increasing competition, it has become possible and necessary to seize the opportunity to use PVC suspension resin from various suppliers in order to maintain or improve the company’s competitiveness. PVC resin Suspension grade is the most commonly used form of PVC resin . It is produced by polymerizing vinyl chloride monomers in an aqueous suspension.
Next, we need to develop the knowledge and experience to properly compare S-PVC resin s so that we don’t buy people who have a negative impact on process economics (more energy and additives for processing due to) or the quality of the final product may affect the product (creating scratches or anything that affects the mechanical properties of the product).
How Molecular Weight of pvc suspension resin is Different from PVC resin
This is the most important variable when choosing an S PVC resin , so all manufacturers strive to meet it.
Polymer chain length determines both application processing (melt viscosity, melt strength, moulding swell, etc.) and product mechanical performance (tensile strength, impact strength, low-temperature behaviour, etc.). Although the chains flow better, they have less crystallinity per molecule, which leads to better physical properties, while longer chains flow less due to entanglement, which increases the crystalline cross-linking network and thus is stronger. material is created.
Although it is generally assumed that molecular weight is uniform and described by a single value, commonly expressed as the ‘K value’, in reality, the temporal and spatial variation of polymer chain length during vinyl chloride polymerization To a lesser extent, the diverse distribution of is mainly due to polymerization temperature (commonly called isotherms) and the conditions under which initiator loading and chain growth occur.
Molecular weights are obtained by measuring the effect of the hydrodynamic volume of polymer chains in dilute solutions, either by viscometry (such as ISO 1628-2) or by chromatography (GPC/SEC).
Manufacturers of PVC suspension resin provide technical data sheets describing their products’ general characteristics and quality certificates of batches produced to confirm that the product meets the specifications provided.
If the molecular weight or K value of the sample cannot be verified directly in your own laboratory or by a third party, it is valid to accept material with a quality certificate if received directly from the manufacturer.
However, if received by an intermediary, it is strongly recommended that this analysis be performed until the authenticity of this intermediary can be verified to avoid confusion or forgery of received S-PVCs.
Comparison:
If the molecular weight of sample B is high, you can expect improved mechanical properties in the final product, but you can also expect reduced processability (increased mix viscosity). This can be compensated for by increasing the consumption of energy and additives. For melting and melting, PVC must be shed. PVC resin Suspension grade is widely used in the production of rigid PVC products, including pipes, fittings, window profiles, siding, and decking. It is also used in the production of flexible PVC products, such as films, sheets, and cables.
How Packaging of Primary Particles are different between SPVC & PVC resin
S PVC resin s with the same K value from different manufacturers often behave differently during processing. The following graph compares two resins produced under different polymerization conditions, but which have the same K value and approximately the same molecular weight distribution. PVC resin suspension grade is a versatile material that is used in many different industries and applications due to its excellent properties and performance characteristics.
Both resins were formulated using the same dry-blending conditions with the same recipe, so the torque-time diagrams measured by torque rheometry show different processing behaviours due to differences in internal morphology.
As mentioned above, the packing method of primary particles has a direct effect on porosity. Loose agglomerates contain larger voids and high porosity, whereas more filled/fused agglomerates contain smaller voids and low porosity.
The porosity of PVC suspension resin is measured by the spontaneous or forced absorption of liquid. This liquid does not swell (penetrate) the polymer matrix under the test conditions and only occupies the volume of the holes or “pores” within the granules.
Standardised methods such as the centrifugal plasticizer absorption method (ASTM D3367) assume that all particles are homogenous and therefore one value is sufficient to describe the porosity. , and other methods such as Mercury Intrusion Porosimetry (ASTM D2873) yield continuous permeation curves with respect to the internal structure.
Directly measure total porosity (cm3 per gram of PVC) regardless of whether you are producing flexible or rigid products and/or ask your supplier to include this analysis in their quality certificate strongly recommended. From how the primary particles are agglomerated.
However, PVC suspension resins always exhibit varying degrees of heterogeneity depending on the conditions under which they were manufactured, so different resins with the same total porosity value may exhibit different morphology distributions.
Therefore, it is recommended to use a method to visualise heterogeneity such as Mercury Intrusion Porosimetry (MIP) or a modified centrifugal plasticizer absorption method at elevated temperatures for various times, as shown in the figure below. increase.
Highly heterogeneous S-PVC resin s consist of granules that range from very porous and easily processable granules to very compact granules with slow plasticizer absorption and poor solubility (“fisheye” and gels that do not dissolve).
Comparison:
If the porosity of sample (B) is higher than that of resin A:
For rigid applications, you can expect faster fusion and easier handling.Flexible applications would expect faster absorption and distribution of the plasticizer.
-If the heterogeneity of sample (B) is greater than that of resin A:
In rigid applications, imperfect additive distribution and melting inhomogeneities that can lead to mechanical failure in the final product are to be expected, reducing energy and additive consumption to homogenise the molten plastic. should compensate for the increase inIn flexible applications, non-uniform plasticizer concentrations and melt inhomogeneities are to be expected, which can lead to cosmetic and even mechanical defects in the final product, thus reducing the energy and It is necessary to compensate for the increased consumption of additives.
How Packaging Of Grains Are Different Between Spvc & PVC resin
This property is usually not considered, but instead the bulk density (the total mass of PVC per unit volume). This is typically measured by a method such as ASTM D1895 Method B. In this type of procedure, a quantity of resin flows through a hopper into a cylinder, both so that the test conditions resemble the granule packing and extruder loading expected from gravity flow under storage conditions.
Since extruder productivity is defined by the amount of material that can be gravity-fed, bulk density is considered an important property in the extrusion of rigid products such as pipes and profiles. Also, while PVC resin s are mixed with some additives before processing, resins with higher bulk density flow more easily, resulting in a denser dry mix and therefore higher productivity.
Bulk density is a less important variable in flexible applications, as high internal porosity is required to absorb plasticizers, and porosity and bulk density are interrelated, so bulk density is expected to be lower. is not considered.
However, since the total volume is accounted for by the volume of solid PVC plus the volume of internal pores (porosity) plus the volume of interparticle voids, bulk density measures how well the S-PVC granules are packed. plug. of internal porosity.
The following formula can be used to calculate the percentage of the volume occupied by porous particles in the S PVC resin sample. This gives you an idea of how easily such PVC resin s flow and compress under gravity.
% Packing= ( (1/ρPVC) + PTU) / (1/ρB )
…where ρPVC is the density of the solid PVC (1.39 g/cm³), PTU is the total porosity of the granule (cm³/gr), ρB is the bulk density (g/cm³) and is measured according to ASTM D1895 Method B or a similar method.
For this reason, regardless of whether you are manufacturing rigid or flexible products, you should measure bulk density (grams of PVC per cm3) directly and/or ask your supplier to include this analysis in their quality certificate. It is highly recommended to request. Granularity can be calculated.
Grain packaging depends on several factors such as:Shape: The better flow of round particles.Surface Roughness: The better flow of smooth particlesSize distribution: Wider size distribution packs better
All of these factors are a result of the polymerization conditions used by PVC suspension resin manufacturers and generally do not change over time, making particle loading an important indicator when comparing resins from different suppliers.
Closer packing of granules will be achieved if the S-PVC manufacturer properly controls and optimizes the polymerization process to form granules with uniform monomer droplets and uniform morphological characteristics.
On the other hand, under unstable and non-optimized polymerization conditions, looser packing of granules is formed, resulting in non-uniform monomer droplets and granules with non-uniform morphology.
Comparison:
If sample B has high packing:
Rigid applications can expect improved melt uniformity and extruder performance while reducing the unit consumption of processing energy.For flexible applications, higher extruder output can be expected to improve plasticizer dispersion and melt uniformity while reducing the unit consumption of process energy.
PVC resin suspension grade has several advantages over other types of PVC resin , including excellent mechanical properties, good thermal stability, and low viscosity, which makes it easy to process.
How Thermal Stabilities are different between SPVC & PVC resin
PVC is plastic with limited thermal stability, its polymer chain is incomplete but contains small amounts of labile functional groups that can trigger a decomposition reaction called dehydrochlorination. Therefore, it propagates along the entire length of the chain via an opening mechanism (hydrochloric acid release). , to form products with low physical properties and yellow to brown or black colour.
Degradation occurs when polymer chains gain mobility through heat generation through a conductive heat transfer and viscoelastic dissipation of mechanical stress. Both processes occur during processing.
However, since PVC is an insulating material, the temperature during heating and melting is not completely uniform, so thermal stability depends not only on the type of PVC chain (concentration of unstable sites) but also on how much energy is required to melt it. It also depends on whether you consume Grains (molecular weight and internal morphology).
To limit the adverse effects of degradation, S-PVC resin manufacturers choose formulations and polymerization conditions to minimise the formation of labile functional groups or slow the spread of degradation.
In any case, vinyl converters need to add compounds called “heat stabilisers”. Its function is to penetrate the PVC matrix and replace the labile functional groups to make them more stable and prevent the cleavage reaction from proceeding in order to avoid degradation of the final product. must be added in sufficient quantity and properly dispersed in the unstable area in time to achieve
Thermal stability can be measured by methods using conductive heat transfer alone (static thermal stability) or in combination with mechanical treatments (dynamic thermal stability).
Dynamic thermal stability is measured using a torque rheometer (ASTM D2538) or other processing equipment to measure rapid changes in rheological properties due to advanced ageing under various temperature and speed conditions. can be evaluated.
All methods of measuring thermal stability differ in the contribution of heat transfer by conduction and self-generated heat by mechanical stress. It also provides a different view of the degradation process, whether we are measuring initiation, evolution, or endpoints.
For this reason, we strongly recommend that you determine the process that best fits your needs and put it in a quality laboratory so that you can compare PVC suspension resin on a like-for-like basis.
Comparison:
If the static thermal stability method is used and sample (B) has low thermal stability:Expect to significantly increase the amount of heat stabiliser if the internal structure of sample (B) is similar or more compact than the current resin (A).If the internal structure of sample (B) is looser than the current resin (A), expect a slight or negligible increase in the amount of heat stabiliser.
If the dynamic thermal stability method is used and sample (B) has low thermal stability,Expect to increase the amount of heat stabiliser accordingly.
PVC resin suspension grade is a versatile and widely used material in the plastics industry, offering a range of benefits for manufacturers and end-users alike. It is also known for its high molecular weight and low residual monomer content, which make it suitable for use in applications that require high purity and resistance to chemicals and UV radiation.
Leave a Reply