Y.P.Singh
Head-Manufacturing and Design & Technical Services
Fenesta Building Systems, Gurgaon

The life style of urban dwellers . . .the creaking sound of the truck and buses plying on the highway close to the building, the thundering sound of the airplane passing by, the repeating sound of the railway track, the monsoon rain making its way from the frail windows, this year planning of painting before diwali, fear of termite eaten windows falling apart! These are familiar to us in everyday life! Infact, it is so intertwined in our day-to-day life, that we do not even notice these anymore!

Energy and Environment, today, is one of the prominent topics under discussion across the globe. Government, industries and users,all, are now more aware and educated about the subject.

India ranks 6^th as energy consumer, at 3.3% of the total world consumption. India’s annual demand has increased by 64% in the past decade with an estimated 8-10% projected rate through 2020. The Indian Government has recognised the need of energy conservation and formulated Energy Conservation Act in 2001. Bureau of Energy Efficiency (BEE) was established in 2002.



Over the last 7 years, BEE has been able to generate awareness among users and manufacturers and drive energy efficient systems like star rating. Today, in 2010, star rating has been mandated for anufacturers of appliances.

The energy efficiency rating is being now extended to other areas, like, commercial and residential buildings, factories, offices etc.

It is imperative to mention, that institution like CII has created a dedicated eam, Indian Green Building Council (IGBC), and has been working since 2001 to assist the industry in creating ‘Green Building’ to save the environment and energy.

The New Age Material
Poly Vinyl Chloride, commonly known as PVC, is one of the most versatile polymers found in the century. PVC, today, finds application in almost all facets of our life, from daily use to highly sophisticated life saving applications, refer figure 1.

UPVC Windows . . . Transforming Life
What was once just a functional necessity – a hole in the top of a cave designed to let out the heat and smoke from cooking and heating fires – is what we now call a window, and its purpose is both functional and aesthetic. In the past, window frames were constructed of wood, aluminum or steel. But after World War II, facing a shortage of natural materials and a massive rebuilding challenge, Germany began producing extruded frames from PVC, a relatively new thermoplastic. Since then, PVC windows have evolved to meet the challenging needs of the construction industry.

UPVC windows and doors offer many of the performance characteristics (Fig. 2) which no other material so far has achieved.
• Sound attenuation
• Heat insulation
• Durability
• Maintenance free
• Corrosion or rust free
• Impermeable to water / rain
• No blistering or flaking
• Impervious to termites or other insects
• Very low expansion co-efficient
• Free from rot

PVC : ‘Tropical Formulation’ for India
PVC flexibility is well know to be formulated to derive specific properties to meet application needs. Indian climate is very different than other countries / continent in terms of UV radiation. The picture (Fig. 3) depicts high UV radiation exposure of India as compared to other countries in Europe and China. Other than UV, India has a unique temperature variation which can be below zero and as high as 50°C. This mandates the need of special formulation of PVC to suit the climatic condition.



The key properties required in a ‘tropical formulation’ for UPVC windows are:

Stabiliser – Heat & Light
As PVC cannot be processed due to its heat sensitive nature, heat stabilisers are a must to improve the stability of PVC and render it processable. Sufficient stabiliser is required to prevent degradation of the base material during processing. Lack of sufficient stabiliser may lead to early discolouration of profile when exposed to sunlight.

Lead has been one of the most established stabilisers for decades and still being used in many parts of the world. US work with tin stabiliser rather than lead.Across the world, eco-friendly material like Ca-Zn has been on agenda for heat stabilisation of PVC and to some extent has been replaced.



Since windows are subject to harsh condition of Indian climate, as with high temperature, the formulation should take care of endurance of profile to continuous exposure of heat and 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 stabilisers are used in recommended dosage.

High & Low Temperature Impact Resistance
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.

Mechanical Properties
Fillers are inorganic minerals (like calcium carbonate) as fine particles, homogenised in the PVC blend. Usage of a filler has an effect on the mechanical property (tensile strength, elongation and impact strength), shrinkage and cost. When used in designated proportion improve the mechanical strength of the polymer and if used in excessive though reduces the cost, but impairs the durability of the product.

UV Resistance Pigments
Titanium dioxide 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) and brighteners 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.

Absence or reduction of these may affect the profile performance drastically in tropical conditions.

Processability Additives like Processing Aids and Lubricants
Processing aids are generally acrylic based materials which enhances the melt strength during fusion and contributes in smooth extrusion of profile with uniform cross section.

Lubricants (internal and external) are used to maneuver the processability of PVC in the extrusion process. Excessive or insufficient usage of the lubricants may cause product defect.

Conclusion
In the next 5-10 years, estimate is, with the growing need of energy and conservation of environment, UPVC windows will provide the answer for this need. This will usher new opportunities for the industry as well. In the pursuit of this new area, the industry should be cautious in any type of compromises and use only ‘tropical formulation’ and product to meet the extreme Indian tropical climate.

It is imperative to mention that the Government can be a catalyst to this entire cause by formulating policies for mandating use, offering incentives to the end users and formulating standards for manufacturing of this product.