0.15% Ni-1 0.30% Ni-2 0.60% Ni-2 0.15% Ni-1 0.15% UVA1
aBlown films 200 p,m thick.
bE50, energy (kLy) to 50% retained elongation.
[6, 35-40]. The weather is variable from time to time and from place to place; hence the weather trial carried out at a certain location is not fully adequate to ascertain the degradation pattern. Hamid and Prichand  conducted an extensive study on weather-induced degradation of LLDPE and hence used a mathematical modeling technique to describe the weathering phenomenon.
Prediction of Lifetime of Greenhouse Films Amin et al.  has developed an empirical model to predict the mechanical properties of greenhouse films exposed for 3 years duration (from 1991-1993) at Dhahran, Saudi Arabia (26.32°N, 50.13oE). Samples were withdrawn periodically and tensile strength and percent elongation at break data were determined along with other properties such as crystalline melting point (Tm) and carbonyl absorbance.
Tensile strength (TS) and percent elongation (PE) data were used to develop empirical equations. Prediction models were developed with exposure time as an independent parameter for both tensile strength and percent elongation at break of exposed greenhouse film, which describes the data accurately as follows:
Figure 5.1 shows the comparison of experimental and predicted values for percent elongation at break (PE). The coefficient of determination R2 was 0.89.
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