Weekly topic: 5 Wealth points for those who answer correctly, 2 Wealth points for participation； Question 186
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This post was last edited by ljtjbx on 2015-10-10 16:40. Multiple choice: The reason why plastics become harder, more brittle, and lose their elasticity over time is the presence of （ ） in the plastics. A. Breakdown of molecules B. Cross-linking of molecules C. Breakage of molecular chains D. Reduction of side chains in molecular chains Answer: B. Cross-linking of molecules —————————————————— Please note: We will close this thread after 24 hours, and at that time we will announce the best response (the best help), as well as the answer and explanation. Attraction Reward: Those who post a topic in this section within two days to provide a detailed explanation or discussion on the knowledge points related to this question are asked to reply/comments in this post to inform us, and we will have a moderator grant them +Attraction. It is not allowed to simply copy and paste; original content is preferred, with at least some organization by the user along with personal insights.
The reason why plastics become harder, more brittle, and lose their elasticity over time is the presence of (B) within them.
B. Cross-linking of molecules. The reasons for plastic becoming hard, brittle, and losing its elasticity during use can be attributed to four main factors: 1. Molding aspects: too small a gate, too small or improperly configured runner systems, as well as poor mold design. 2. Equipment aspects: There are dead corners or obstacles inside the barrel, the machine’s plasticizing capacity is too low, and the ejection mechanism is tilted or unbalanced. 3. In terms of raw materials: the materials are mixed with other impurities, the plastics have been recycled too many times or the proportion of recycled material is too high, and the quality of the raw materials themselves is poor. 4. In terms of processing: If the temperature of the barrel and nozzle is too low, it should be increased; the pre-plasticization back pressure and rotation speed of the screw should be reduced. The mold temperature should also be adjusted appropriately – it shouldn’t be too high nor too low.
The reason why plastics become harder, more brittle, and lose their elasticity over time is the occurrence of (B. molecular cross-linking) within the plastics.
The reason why plastics become harder, more brittle, and lose their elasticity over time is the presence of （ ） within the plastics. B. Cross-linking of molecules
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