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A major polycarbonate market is the production of compact discs, DVDs, and Blu-ray discs. [13] These discs are produced by injection-molding polycarbonate into a mold cavity that has on one side a metal stamper containing a negative image of the disc data, while the other mold side is a mirrored surface.
A polycarbonate is an oxocarbon dianion consisting of a chain of carbonate units, where successive carbonyl groups are directly linked to each other by shared additional oxygen atoms. That is, they are the conjugate bases of polycarbonic acids , the conceptual anhydrides of carbonic acid , or polymers of carbon dioxide .
The volume of a particular material or compound is affected by ambient moisture and may be considered its coefficient of hygroscopic expansion (CHE) (also referred to as CME, or coefficient of moisture expansion) or the coefficient of hygroscopic contraction (CHC)—the difference between the two terms being a difference in sign convention.
The use of the terms positive and negative for types of electricity grew out of the independent work of Benjamin Franklin around 1747 where he ascribed electricity to an over- or under- abundance of an electrical fluid. [23]: 43–48 At about the same time Johan Carl Wilcke published in his 1757 PhD thesis a triboelectric series.
A study from 2024 found that compared to glass and aluminum, plastic may actually have less of a negative effect on the environment and therefore might be the best option for must food packaging and other common uses. [126] The study found that, "replacing plastics with alternatives is worse for greenhouse gas emissions in most cases."
A measure of the separation of positive and negative electric charges within an electrical system, i.e. a measure of the system's overall electrical polarity. The SI unit for measuring electric dipole moment is the coulomb-metre (C⋅m), but the debye (D), a non-SI unit, is also widely used in chemistry and atomic physics. electrical conductivity
Poly(trimethylene carbonate) (PTMC) is an aliphatic polycarbonate synthesized from the 6-membered cyclic carbonate, trimethylene carbonate (1,3-propylene carbonate or 1,3-Dioxan-2-one). Trimethylene carbonate (TMC) is a colorless crystalline solid with melting point ranging between 45°C and 48 °C and boiling point at 255°C (at 760 mmHg).
Positive and negative feedback, qualitative types; Positive and Negative Affect Schedule, a form of questionnaire measuring psychological effects; Positive or negative externalities, economic activities; Positive and negative politeness, types of politeness strategies in politeness theory; Positive and negative value, ethic or philosophical values