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This is your hub for knowledge and information on windows and doors. Over the years, Fenesta has developed a unique understanding of how they work. This knowledge is shared through this section to help you learn what features and materials enable windows and doors to contribute to your home's comfort

What is UPVC


One of the most versatile polymers found in the world is PVC or Polyvinyl Chloride, and uPVC, a material that is gaining more and more popularity by the day, is based on this polymer. PVC is also one of the most commonly used polymers that find application in almost all facets of our life. It is known to be used in a range of fields, from daily use to even a variety of life-saving equipment. PVC offers a certain level of flexibility that makes it well suited for several applications. Using a unique formulation, this flexibility is leveraged to prepare a special blend, uPVC, which is used in doors and windows as well. The full form of 'U' in uPVC is unplasticised. The uPVC material is used widely as a framing material because of the presence of Unplasticised Polyvinyl Chloride in the polymer; the term is also the widely accepted full form of uPVC. As a framing material, uPVC offers unmatched quality, requires very little maintenance and is available in a number of colour options. With the numerous benefits of uPVC doors and windows, uPVC has managed to garner a 50% market share in countries like the USA and UK. In these countries, it is also known as vinyl siding or vinyl.

Benefits of UPVC Doors & Windows:

What is best about uPVC doors and windows is that their performance characteristics are unmatched. There are several special characteristics that define uPVC, meaning that their benefits too are significant:

  • It requires less energy during production
  • Offers rain insulation
  • It is resistant to chemicals
  • Has many commercial applications
  • It is recyclable
  • Offers UV protection
  • Requires no painting or extra maintenance
  • Provides sound insulation
  • Resistant to saltwater
  • Can match all architectural requirements
  • Offers wind insulation
  • Highly resistant to impact
  • It is environment-friendly
  • Protects against environmental influences
  • It is fire-retardant
  • Offers protection against insects

UPVC Formulation:

uPVC is prepared with a unique formulation that involves the addition of stabilisers and modifiers to PVC. This helps in making the polymer a bit more rigid, meaning that uPVC can then be used in window and door frames as well.


In the blend composition of the polymer, PVC forms a major portion, which is approximately 80-85% Unlike the other polymer, PVC is a heat-sensitive component and requires some additives so it can be processed. This polymer has versatile properties due to which it can either be made as soft as rubber or as hard as engineered plastics. This versatility of PVC is achieved with additives, such as impact modifiers, fillers, UV stabilisers, lubricants, pigments, processing aids, plasticisers and more. All these are added to the material during the blending process.

Stabilizer - Heat & Light:

When it comes to formulating uPVC for doors and windows, what is to be remembered is that PVC cannot be processed alone as it is heat sensitive. So, a heat stabiliser is used in to improve the stability of the polymer and make it processable. Also, what is important for the uPVC formulation is to use a sufficient amount of stabiliser to prevent degradation of the PVC material. If there is a lack of sufficient stabiliser used during the process, it may lead to early discolouration of the material when it is exposed to sunlight. Keeping in mind the harsh climatic conditions and high temperatures experienced during a major portion of the year, it is important for the window or door profile to be able to endure the continuous heat and UV. This is applicable for all profiles that are used in the tropical zone. To make sure that the profile is well-balanced, light stabilisers should be used in a recommended dosage.

Processing Aids:

Processing aids are generally acrylic-based materials that help in enhancing the melt strength of the material at the time of fusion. They also ensure that the profile extrusion is smooth and that the material has a uniform cross-section.

Impact Modifier:

Polymers typically tend to get brittle on exposure to lower temperatures or UV radiations. Impact modifiers that are acrylic-based are used to ensure that the profile retains its impact strength even after it is exposed to a low temperature or to UV light. If the profile receives an insufficient dosage or if a low-cost impact modifier like CPE is used, it will lose its impact resistance over time, becoming brittle and cracking either at the time of fabrication, installation, or operation.


During the extrusion process, these additives are used to help in manoeuvring the processability of PVC. Insufficient or excessive use of lubricants can result in defective products.

Pigments - Titanium Di-Oxide:

Titanium Dioxide is quite expensive and is used as the white pigment to impart a natural white colour to the PVC profile. It provides much-needed UV stability to the product, which enhances its durability over the years. Also, the dosage of the pigments for PVC depends on the amount of UV radiation in the region. Usually, the range of pigment dosage is from 4 parts for climates like Europe to 10 parts for the harsher climatic conditions in places like India or Arizona. This pigment is also known to provide opacity to products. Other organic and inorganic pigments may also be used to add colour to products but may not offer as much stability against UV.


Fillers are the inorganic minerals that are used in a PVC blend. The usage of fillers in PVC enhances the mechanical properties of PVC, like the impact strength and tensile strength. If used in the right proportions, they help increase the mechanical strength of the product but if used in excess they can impair the durability.