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In case of atactic polypropylene, the methyl group (-CH 3) is randomly aligned, alternating (alternating) for syndiotactic polypropylene and evenly for isotactic polypropylene. This has an impact on the crystallinity (amorphous or semi-crystalline) and the thermal properties (expressed as glass transition point T g and melting point T m ).
For example, atactic polypropylene is usually amorphous and transparent while syndiotactic polypropylene, which has crystallinity ~50%, is opaque. [30] Crystallinity also affects dyeing of polymers: crystalline polymers are more difficult to stain than amorphous ones because the dye molecules penetrate through amorphous regions with greater ease.
The word plastic derives from the Greek πλαστικός (plastikos), meaning "capable of being shaped or molded;" in turn, it is from πλαστός (plastos) meaning "molded." [ 8 ] As a noun , the word most commonly refers to the solid products of petrochemical-derived manufacturing.
The amorphous polyalphaolefins are synthesized by a catalyst system based on a Z-N supported catalyst and an alkyl aluminum co-catalyst. The polymerization process produces a mostly amorphous polymer with low crystallinity. Crystallinity depends on the catalyst system and on the use of co-monomers.
An alarming study that had Americans tossing out their black plastic kitchen utensils, toys and to-go packages earlier this month overstated the concern, the researchers admit.
All polymers (amorphous or semi-crystalline) go through glass transitions. The glass-transition temperature ( T g ) is a crucial physical parameter for polymer manufacturing, processing, and use. Below T g , molecular motions are frozen and polymers are brittle and glassy.
Cats are limited in their perception of color. Human eyes have 10 times more cone cells than feline eyes, meaning we can see a larger range of colors than cats, according to Purina.
Sildenafil citrate (the active ingredient in Viagra) isn’t linked to physical addiction, meaning you won’t develop a physical dependence on it or develop withdrawal symptoms if you stop using ...