With the help of its experts and lab equipment, Sepehr Plastic Padideh Laboratory examines and controls the performance of products based on national standard tests and client requests.

The laboratory unit is comprised of the microbial and physical labs.

The physical lab conducts tests based on characterization of polymer raw materials, compounding of materials, and assessment of their effect on the product in terms of quality, quantity, and mechanical properties.

Tests in this lab include:

Universal Mechanical Properties Test:

  • Tensile strength test, compressive strength test, product storage resistance test, cap opening force test, and stress and strain tests based on national standards 8505 and 8393.
  • Other tests include tests on PET containers based on national standard 11610 and polypropylene containers based on national standard 11604.
  • Packaging box tests based on national standard 150.
  • Ash content and calcium carbonate content test using tube furnace based on national standard 7175.
  • Flip-cap opening/closing force test using screw cap torque tester based on existing standards.

The microbial lab tests products for quality control in terms of health and hygiene using the following equipment:

  • Laminar flow cabinet
  • Different types of culture media
  • Scale
  • Oven
  • Laboratory glassware
  • Incubator
  • Autoclave
  • Identification and detection of bacteria and fungi based on the national standard

Microbial Laboratory

The quality control unit is one of the key organizational units in manufacturing companies such as Sepehr Plastic Padideh Company. This unit is responsible for inspection and quality control of raw material, production process, and end products as well as the process of production and supply of quality and sanitary products. This unit is made up of physical, chemical, and microbiological labs and is responsible for microbial contamination tests for all raw materials up until the production of the healthy end product. These operations are undertaken by the team of experts based in the microbiological laboratory of Sepehr Plastic Company. These seasoned experts assess the necessary tests based on national and international standards according to the internal company SOP.

Some of the microorganisms tested for in the cosmetics industry are:

  1. Aerobic mesophilic microorganisms (Standard 11804)
  2. Coliforms (Standard 3759)
  3. Pseudomonas aeruginosa (Standard 9793)
  4. Escherichia coli (standard 9933)
  5. Staphylococcus aureus (Standard 9934)
  6. Molds and yeasts (Standard 11169)

Testing Process:

First, the TSB culture medium (Tryptic Soy Broth or Nutrient Broth) is prepared and poured into a bottle. Then, the culture medium is smeared across the inner parts of the bottle and incubated at 37-35 °C. In case there is turbidity in the culture medium after 24-48 hours, differential tests are conducted to determine the contamination type.

Aerobic Mesophile Count:

One cc of the 0.01 dilution of the turbid solution is poured into a plate and the pour-plate technique is performed with the tryptic soy agar or nutrient agar medium. The colonies are counted after 48 hours and multiplied by 10.

Differential Tests:

Surface culture is performed using the suspicious liquid medium next to a flame and under the microbial cabinet in Mannitol salt agar (MSA), MacConkey agar, Cetrimide agar, EMB agar, and Sabouraud dextrose agar (SDA) plates. Then the plates are incubated for 24 to 48 hours. (SDA or YGC culture medium is placed in a refrigerated incubator at 25°C for 3-5 days.)


  • The MacConkey agar culture medium is used for the identification of coliforms.
  • The EMB agar culture medium is used for the identification of E. coli bacteria.
  • The Cetrimide agar culture medium is used for the identification of Pseudomonas aeruginosa bacteria.
  • The MSA culture medium is used for the identification of Staphylococcus aureus bacteria.
  • The Chloramphenicol SDA or YGC culture medium are used for the identification of mold and yeast.

The permissible level for coliforms, E. coli, Pseudomonas aeruginosa, and Staphylococcus aureus in cosmetic products is negative; for aerobic mesophiles it is 102×5; and for mold and yeast it is up to 10 colonies per CFU/ml.

Considering that there are national standards on the permissible limits of contamination in bottles, it is determined based on the organization’s SOP, which is being developed. Bottles used for liquid hand wash, dishwashing liquids, and baby and adult shampoos and body wash are more sensitive products considering the microbial risks. Bottles used for washing liquids, poly-wash detergents, and surface cleaners are examined weekly and randomly for microbial contamination.

 Considering the high temperature in the bottle production process, there is little chance for contamination by bacteria that are transmitted through contaminated water (gram-negative bacteria such as coliforms, E. coli, and Pseudomonas aeruginosa), however, the transmission of microorganisms that may be transmitted via infected personnel (e.g Staphylococcus aureus and yeast) is more likely.

Tests on Consumer Products:

All raw materials and products are tested based on the international standards, and then supplied to customers.

Tensile test

The tensile strength, stress (elongation force) and strain (elongation value and percentage) of all products are measured to supply high-quality products meeting customer needs.

The results of the tensile test include:

  1. Maximum force applied before rupture (stress)
  2. Maximum elongation before rupture (strain)
  3. Minimum energy required from film rupture

Melt flow index (MFI)

This test is used to characterize raw materials. Two materials with close MFIs have almost the same properties.

Impact test

Determining the maximum strength of a product against impact

Bottle air pressure test

This test measures the product strength against increased air pressure inside the bottle before bursting.