# Investigation of the Effect of Operational Factors on Conveyor Belt Mechanical Properties
## 4 Comparison of Results and Discussion  
### Specimens Exposed in the Climatic Chamber  
The test results for the samples exposed to different conditions in the climatic chamber are given in Figure 15.  
The results of tensile modulus for samples subjected to ageing under different climatic conditions demonstrate that the highest tensile modulus can be observed for the samples exposed to a temperature set to \(-30^{\circ}\)C (303 K) (KKA-30-20). In the case of samples exposed to a temperature of \(-20\)\({}^{\circ}\)C (253 K) (KKA-20-20) for 14 days, E decreased by about 5%. It can be observed that below 0\({}^{\circ}\)C temperatures in the Celsius scale have no negative effects on the tensile modulus compared to the tensile modulus of the reference samples. The lowest E was recorded for the samples subjected to ageing at a temperature of 80 \({}^{\circ}\)C (353 K) and a RH of 80% (KKA-80-80): 334 MPa. A higher value of E was obtained for the samples subjected to exposure to the same RH, but at a lower temperature set to 10 \({}^{\circ}\)C (283 K) (KKA-10-80). In the case of KKA-10-80, the value of E was 85% of the value of module E of the samples exposed to a higher temperature (KKA-30-80). It can also be observed that for two cases of ageing at the same temperature of 30 \({}^{\circ}\)C (303 K), but at two different RH values: 80% and 50%, the tensile modulus differed by 3%. Figure 14: KKB-80-80 sample after tensile strength testing. Figure 15: Mechanical parameters of samples tested in the climatic chamber. Summing up the tensile modulus results, it can be observed that:  
* higher values of E were obtained for exposure at below 0 \({}^{\circ}\)C temperature in the Celsius scale (decreasing values of the minus temperature does not have a negative effect on tensile modulus),
* among the tested variants, ageing produces the least desired results at a temperature of 80 \({}^{\circ}\)C (353 K) and at an RH of 80%;
* an increase in the above 0 \({}^{\circ}\)C temperature in the Celsius scale leads to a decrease in tensile modulus,
* a decrease in humidity with the temperature remaining the same leads to a slight decrease in E (KKB-30-80 and KKC 30-50),
* in most cases, the reference samples have a lower E, ranging between 3% and 10%, than samples tested in the climatic chamber, except for two ageing variants--KKB-10-80 and KKB-80-80--where E was lower by 10% and 22% than the reference sample, respectively. Examining the effect of ageing conditions on tensile strength of the tested conveyor belt samples, it was observed that:  
* the highest tensile strength was obtained for three ageing cases, two of them involving exposure at a below 0 \({}^{\circ}\)C temperature in the Celsius scale,
* the lowest tensile strength was obtained for samples exposed at a temperature of 80 \({}^{\circ}\)C (353 K) and an RH of 80% (KKA-80-80),
* decreasing humidity and maintaining the ageing temperature unchanged (KKC-30-50) leads to a 7% decrease in the tensile strength compared to exposing at a humidity of 80% (KKB-30-80),
* in the majority of cases, the tensile strength is lower compared to the tensile strength of the reference samples; in the three cases KKA-20-30, KKA-20-20 (exposing at minus temperature) and KKB-30-80, the obtained tensile strength had the same value. It can be observed that temperature below 0 \({}^{\circ}\)C in the Celsius scale does not have a negative effect on the tensile strength compared to the tensile strength of the reference samples, but it is difficult to determine the effect of temperature or humidity on strength unanimously. The coefficient of correlation (\(\rho\)) between the strength and the temperature is \(\rho=-0.58\) while that between strength and humidity is \(\rho=-0.66\), which can indicate that humidity has a higher effect on the belt's tensile strength than temperature. * the results for the negative temperature can be explained by the fact that lowering the temperature results in a more exponential behavior of the glassy-brittle state, such as increased stiffness and reduced deformability.