Biodegradable polymer which, edible films have gained more attention due to their environmentally-friendly characteristics, vast variety and availability, non-toxicity, and low cost. Biodegradable polymers have a long history, and since many are natural products, the precise timeline of their discovery and use cannot be accurately traced. One of the first medicinal uses of a biodegradable polymer was the catgut suture, which dates back to at least 100 AD. The first catgut sutures were made from the intestines of sheep, but modern catgut sutures are made from purified collagen extracted from the small intestines of cattle, sheep, or goats. The concept of synthetic
Strings (tennis) stringing may be a good alternative to natural gut and multi-filament strings. This is especially true for those who have had tennis elbow and find natural gut string to be too costly. Metal wire, usually piano wire, was used in some historical racquets. The "gauge" number determines the thickness of the string. A string rated with a high gauge number is a thinner string, and vice versa. Thinner strings typically offer higher performance but break more frequently than thicker strings. Virtually all modern raquets are strung in a criss-cross horizontal-vertical pattern. Various other patterns have been used in history with