Polypropylene (PP) is a thermoplastic polymer known for its versatility, resistance to various chemical solvents, bases, and acids. It's widely used in packaging, textiles, automotive components, and consumer goods. The density of polypropylene varies slightly depending on its type (e.g., homopolymer, copolymer) and processing technique but generally falls within the range of 0.855 to 0.946 g/cm³. This makes it lighter than many other plastics, contributing to its widespread use in applications where weight reduction is crucial. Its low density, combined with strength and rigidity, makes polypropylene an excellent choice for a wide range of applications, from lightweight, durable packaging to automotive parts that benefit from its lightweight nature to improve fuel efficiency.

Amino acids, the building blocks of proteins, exist in different forms based on the pH of their environment. The predominant form of an amino acid in a neutral pH, such as that of the human body (approximately pH 7.4), is the zwitterionic form. In this form, amino acids have both a positively charged amino group (NH3+) and a negatively charged carboxylate group (COO-) but are overall neutrally charged. This dual charge nature allows amino acids to behave as both acids and bases, a characteristic that is critical for the diverse range of reactions and interactions they participate in within biological systems. The zwitterionic form contributes to the solubility of amino acids in water and is crucial for protein structure and function, influencing how proteins fold, interact, and carry out their roles in the cell.

Polypropylene (PP) is a lightweight, durable thermoplastic polymer known for its versatility in various applications, from packaging to automotive parts. Its properties include high chemical resistance, making it suitable for containers that store liquids like detergents and acids. PP also has a high melting point (around 160°C), allowing it to be used in microwaveable containers and hot fill applications. It's resilient to fatigue, meaning it's ideal for products requiring hinge mechanisms. Additionally, PP has good electrical insulating properties. However, it does have some limitations, such as poor UV resistance, which can be improved through additives. Its low density provides benefits in applications where weight savings are important. PP can be easily modified with additives to enhance properties like impact resistance, making it a highly adaptable material for a wide range of industries.