WHAT IS UPVC
UPVC is based on polyvinyl chloride (PVC), one of the most versatile polymers found in the century. PVC today finds application in almost all facet of our life, from daily use to highly sophisticated life saving applications. This flexibility of PVC is leveraged through a unique formulation to prepare a special UPVC blend for windows and doors.
UPVC (where ‘U’ stands for unplasticized) is one of the most preferred window framing material across the world. The material comes in a range of colour, is low maintenance and offers benefits which no material so far has matched. This has helped UPVC garner more than 50% market share in countries like UK, USA where it is also known as vinyl or vinyl siding.
BENEFITS OF UPVC WINDOWS:
UPVC windows and doors offer many of the performance characteristics which no other material so far has achieved
UPVC is prepared with a special formulation in which modifiers and stabilizers are added to polyvinyl chloride (PVC) making it rigid and suitable for use as window frames.
PVC:PVC forms the major (approx 80 – 85 %) constituent of blend composition. PVC unlike other polymer is heat sensitive and hence needs additives for processing. The property of material is such that it can be made as soft as rubber or can have strength close to any other engineered plastic. This versatility is developed through additives (like light & UV stabilizer, processing aids, impact modifier, lubricants, fillers, pigments, plasticizer etc.) which are added in PVC during the blending process.
Stabilizer – Heat & Light:As PVC cannot be processed due to its heat sensitive nature, Heat stabilizers are must to improve the stability of PVC and render it process-able. Sufficient stabilizer is required to prevent degradation of base material during processing. Lack of sufficient stabilizer may lead to early discoloration of profile when exposed to sunlight. Since windows are subject to harsh condition of Indian climate – High temperature, the formulation should also take care of endurance of profile to continuous exposure of heat & UV. This typically applies for PVC window profile in the tropical zone wherein the profile is exposed to high temperature with UV radiations. For this light stabilizers are used in recommended dosage.
Processing Aids:These are generally acrylic based material which enhances the melt strength during fusion and contributes in smooth extrusion of profile with uniform cross section.
Impact Modifier:Typically polymers tend to become brittle once subjected to low temperature or exposed to UV radiation. Acrylic based impact modifiers are used to retain impact strength even after UV exposure and at low temperature. Insufficient dosage or low cost impact modifier (like CPE) may not be able to withstand the impact resistance over long period of usage and may become brittle / crack during fabrication, installation, operation or usage.
Lubricants:These additives are used to manoeuvre the process-ability of PVC in the extrusion process. Excessive or insufficient usage of the lubricants may cause product defect.
Pigments – Titanium Di-Oxide:Titanium Di-oxide is an expensive pigment which is used as white pigment, imparting natural white colour to the PVC profile and provides the necessary UV stability for the product to have durability over years of usage. The dosage of TiO2 depends upon the UV radiation of the region. Typically the dosage ranges from 4 parts for climate similar to Europe and 10 parts for harsh tropical climate like Arizona, India, etc. The pigment also gives opacity to the product. Other pigments (organic / inorganic) & brightener are used to colour the pigment but may not have similar UV stability. These should be used cautiously ensuring the weather resistance and colour fastness.
Fillers:These are inorganic minerals (like calcium carbonate) as fine particles homogenized in the PVC blend. Usage of filler has effect on mechanical property (tensile strength, elongation and impact strength), shrinkage and cost. When used in designed proportionate improve the mechanical strength of the polymer and if used in excessive though reduces the cost but impairs the durability of product.