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Sandy_dkk

Kemarin jam 03:21:04 PM
tulis saja langsung soalnya.
koordinat apa yang diketahui? kalau koordinat busur, minimal harus diketahui 3 koordinat.

Nursaadah

September 16, 2014, 05:41:54 PM
halooo
temannn...z punya pertanyaan nih ...bgmn mencari panjang busur sebuah lingkaran jika yang di ketahui titik koordinat ???

iyon7

September 16, 2014, 09:56:49 AM
gimana sih cara bertanya ato buat diskusi
 

LabSatu

September 05, 2014, 04:47:59 PM
Halooo,, salam kenal semua dari labsatu

UlfaSeptilia

September 05, 2014, 03:26:53 PM
Selamat sore teman2 yang disini, saya mau tanya soal cisco. kalau ACL pakainya Static Routing bisa gak yah? atau harus EIGRP ama OSPF yah? Makasih sebelumnya
 

Sandy_dkk

Agustus 31, 2014, 01:36:12 PM
bukan rumit kang Farabi, tapi memang tidak bisa.

peterkusuma

Agustus 25, 2014, 10:03:23 PM
Teman2, ada yg tau kelarutan aluminium klorida dalam benzena ga?
Thx
 

Farabi

Agustus 25, 2014, 01:42:52 AM
Jadi penasaran, bisa ga tuh dipecahkan? Perkalian ya bukan pertambahan. Rumit banget kayaknya.
 

Sandy_dkk

Agustus 24, 2014, 11:58:59 PM
oh, ada yg nanya to d bawah? saya gak liat.
ada 3 variabel dan hanya ada 1 persamaan, maka mustahil mengetahui nilai setiap variabel. kecuali yang ditanyakan adalah hasil operasi dari variabel-variabel tsb, formula operasi tertentu masih mungkin ketemu hasilnya tanpa harus mengetahui nilai setiap v
 

Monox D. I-Fly

Agustus 24, 2014, 09:39:37 PM
bukannya 2p.3q.5r itu maksudnya 2p x 3q x 5r ya? Jadinya 1125000 = 30pqr

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Penulis Topik: Vitamin C dan plastik  (Dibaca 2778 kali)

0 Anggota dan 1 Pengunjung sedang melihat topik ini.

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Vitamin C dan plastik
« pada: Maret 04, 2007, 05:03:35 PM »
http://www.nsf.gov/news/news_summ.jsp?cntn_id=108123&org=NSF&from=news

Vitamin C and Water : Healthy for Plastics

Two new laboratory breakthroughs are poised to dramatically improve how plastics are made by assembling molecular chains more quickly and with less waste. Using such environmentally friendly substances as vitamin C or pure water, the two approaches present attractive alternatives to the common plastic manufacturing technique called free radical polymerization (FRP).

"The methods both present novel and complementary ways to dramatically improve efficiency, product control, and cost for the polymer industry," said Andy Lovinger, the National Science Foundation program director who oversees funds for the two projects. "Each of these approaches could have a very significant impact on polymer manufacturing."

Plastics are polymers, long, potentially complex, molecule chains crafted from an array of smaller chemical units.  Using FRP, chemical engineers can create the right plastic for a range of applications, such as a specific trim for a car door or soft foam for a pillow.

For some plastics, the building-block molecules do not easily link together.  To surmount this problem, researchers from Carnegie Mellon University in Pittsburgh, Pa., devised a process called atom transfer radical polymerization (ATRP), which provides creative ways to coax the chemical subunits into chains.  However, this method comes with certain costs, such as the need for a copper catalyst that can become unwanted waste.

Now, the Carnegie Mellon researchers have discovered that adding vitamin C, glucose, or other electron-absorbing agents to the ATRP process can reduce the amount of copper catalyst by a factor of 1000. Because the catalyst often needs to be removed from the end products, less copper means far less waste and drastically reduced removal costs. Mass manufacturing could become more affordable for a range of items such as advanced sensors, drug delivery systems, paint coatings, and video displays.

At the University of Pennsylvania (UPenn), researchers are using a different approach to improve FRP. Called single electron transfer-living radical polymerization, the new method relies upon relatively low-energy reactions, uses elemental copper (copper metal, as opposed to copper in a chemical solution) as a catalyst to limit byproducts and allows manufacturers to use one of the most environmentally friendly solvents in the arsenal, water.  The entirely new method of polymerization builds upon existing mechanisms to craft large molecules very quickly.



 

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