The recycling code for polypropylene (PP) is 5. This symbol, part of the Resin Identification Code (RIC) system, helps in the sorting of plastics for recycling purposes. Introduced in 1988, the RIC was developed to facilitate more effective recycling processes by providing a uniform standard for identifying the different types of polymer materials. Polypropylene is a versatile plastic used in a wide range of products, including food containers, packaging, automotive parts, and textiles. Recycling PP can reduce the demand for new plastic, conserve resources, and minimize pollution. However, the actual recycling rates for PP can vary widely by region due to differences in local recycling capabilities and policies. To improve PP recycling rates, consumers are encouraged to check local recycling guidelines and dispose of PP items accordingly.

Starting an online yarn business involves a few crucial steps. Firstly, identify your niche within the yarn market, considering factors such as organic materials, exotic blends, or budget-friendly options. Next, source your products from reliable suppliers or consider producing your own if you have the skills and resources. Establishing an online store can be done through platforms like Shopify, Etsy, or WooCommerce, which simplify the process of setting up and customizing your shop. It's essential to take high-quality photos of your yarn and provide detailed descriptions to attract and inform customers. Marketing your business through social media, blogging, and email newsletters can help reach a wider audience. Lastly, understand the legal requirements for starting an online business in your area, including any necessary business licenses and tax implications.

The glass transition temperature (Tg) is a critical property of polymers that marks the transition from a hard and brittle "glassy" state to a more flexible and rubbery state. At temperatures below Tg, the polymer chains are relatively immobile and rigid, behaving like a glass. As the temperature rises above Tg, the chains gain enough energy to move past each other, becoming more mobile and elastic. This transition affects numerous physical properties such as mechanical strength, flexibility, and viscosity. Understanding Tg is essential for predicting how a polymer will behave under different conditions, aiding in material selection for specific applications. For instance, plastics used in food packaging often have a high Tg to maintain rigidity at room temperature, while rubbers have a much lower Tg to remain pliable.