Polyethylene Glycol (PEG) and Polypropylene Glycol (PPG) are both polyether compounds but differ in properties and applications. PEG is produced through the polymerization of ethylene oxide and is water-soluble, making it ideal for medical and pharmaceutical applications, such as laxatives or in drug delivery systems due to its biocompatibility. On the other hand, PPG, formed from the polymerization of propylene oxide, exhibits hydrophobic characteristics compared to PEG, and is primarily used in industrial applications like in the production of polyurethane foams, lubricants, and surfactants. The main differences between the two lie in their solubility, with PEG being water-soluble and PPG less so, and their usage across different industries based on this property and their respective chemical structures.

Titanium was first used in the 19th century. It was first discovered in 1791 and first reduced to a metal form in 1825. The first widespread industrial use began in the 1940s and 1950s.

Low Density Polyethylene (LDPE) is widely used in packaging due to its flexibility, toughness, and moisture resistance. However, its barrier properties, particularly against gases like oxygen and carbon dioxide, are relatively poor compared to other materials such as High Density Polyethylene (HDPE) or Polyethylene Terephthalate (PET). This limitation often necessitates the incorporation of LDPE into multi-layer structures or coatings that include materials with better barrier properties for applications requiring significant gas or aroma barrier. The permeability of LDPE to various substances is influenced by its molecular structure; the less crystalline nature and higher chain branching of LDPE compared to HDPE results in more free volume, which allows gases and vapors to permeate more readily. Enhancing the barrier properties of LDPE typically involves blending with other polymers, chemical modification, or using advanced manufacturing techniques to create nanocomposites or incorporate barrier-enhancing fillers.