Linear Low-Density Polyethylene (LLDPE) is a type of polyethylene with unique thermal properties owing to its short chain branching structure, giving it a balance of flexibility and strength. Its melting point generally ranges from 120 to 124°C, making it suitable for applications requiring thermal stability up to moderate temperatures. LLDPE's specific heat capacity is around 2.3 J/g·°C, enabling efficient thermal energy storage and dissipation. Its thermal conductivity is relatively low, typically around 0.33 W/m·K, which means it's not an ideal material for applications requiring rapid temperature changes. The coefficient of thermal expansion for LLDPE is approximately 200 x 10^-6 /°C, which is significant for considering dimensional stability in varying temperatures. These thermal characteristics make LLDPE popular in packaging, containers, and pipes, where durability and resistance to environmental stress cracking are required.

Cellulose is a type of polysaccharide and the most abundant organic polymer on Earth, found primarily in the cell walls of plants. It plays a crucial role in providing structural support to plants. In the context of the human diet, cellulose is classified as an insoluble fiber. This means it does not dissolve in water and is not broken down by the digestive enzymes in the stomach or small intestine. Instead, cellulose passes through the gastrointestinal tract relatively intact, aiding in digestion by adding bulk to the stool and promoting regular bowel movements. Insoluble fibers like cellulose also help prevent constipation by absorbing water, which can soften the stool and make it easier to pass. Furthermore, a diet high in fiber, including insoluble fibers like cellulose, has been associated with numerous health benefits, including a lower risk of diabetes and heart disease. However, because humans cannot digest cellulose, it does not provide any nutritional value or calories.

Polypropylene fibre reinforced concrete (PFRC) is known for its increased resistance to cracking and improved ductility. However, it has its drawbacks. One significant negative is its lower modulus of elasticity compared to traditional concrete, leading to potentially less stiff structures that may not be suitable for all applications. Additionally, the fibers can decrease the workability of the concrete mix, making it harder to place and finish. This can lead to an increased reliance on admixtures to improve workability, potentially raising costs. Another issue is the uniform distribution of fibers; if not adequately mixed, it can lead to weak spots within the concrete. Furthermore, the long-term durability of PFRC in various environmental conditions, such as exposure to UV light or chemicals, remains an area of ongoing research.