Polimerisasi adalah proses bereaksi molekul monomer bersama dalam reaksi kimia untuk membentuk tiga dimensi jaringan atau rantai polimer. Polimerisasi digolongkan ke beberapa sistem: sistem …Full description
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it describes about the polymerization processes in industries
Partitura de Canto: Un pueblo radical, de Convención Nacional Bautista de México. Lo adoptamos en Ciudad Juárez, Chihuahua. Pr. Isaí Martínez, IB2DF.
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PRACTICE QUESTIONS FOR FOR FREE RADICAL POLYMERIZAT POLYMERIZATION ION 1. Rate Rate const constant antss for for temi teminat nation ion k t may be order of 10 8 liter/mol sec in free-radical polymerizations. Consider the polymerization polymerization of styrene initiated by di-t-butyl 0 peroxide at 60 C. or a solution of 0.01 ! peroxide and 1.0 ! styrene in benzene" the initial rate of polymerization is 1.#x 10 -$ mol/liter sec and M of the polymer produced is 1%8 000. 000. &a' rom the abo(e abo(e informat information ion estimate estimate k p for styrene at 60 0C. &b' )hat is the a(era*e a(era*e lifetime lifetime of a macromolecu macromolecule le durin* initial initial sta*es of polymerization in this system+ n
, C,-
C.
,
.C
C,-
k tc
C,-
,
,
C
C
C,-
ermination ermination is by alone. his process is termination by combination. Rate constant of this reaction is k tctc " k td td 0.
. or a particular particular applicatio application" n" the molecular molecular ei*ht ei*ht of the polymer polymer made in 2roblem 2roblem 1. is too hi*h. )hat concentration of t-butyl mercaptan should be used to loer the number molecular ei*ht of the polymer to 8# 000+ or this" transfer a*ent C is %.$ in the polymerization of styrene. styrene.
%.)hen bulk styrene is heated to 10 0C" polymerization occurs because of thermal initiation in the absence of an added initiator. 3t is obser(ed that polystyrene ith M 00 000 is producedunder these conditions at a rate of 0.011 * polymer/liter/min. 4sin* this information calculate the total initial rate of polymerization expected if an initiator ith concentration 0.1!" k d 10-5 sec-1" and f 0.8 is added to this system at 10 0C. & !olar mass of styrene 105 k t k tctc k td td 0 '. n
5. ree-radical polymerization polymerization can be initiated by a redox system in(ol(ed Ce5 and an alcohol7 RC,, Ce 5
k
Ce% , R-C,,
he propa*ation reaction can be summarized as usual as
k p !n. !
!n1
)here !n. is a macroradical ith de*ree of polymerization n. he ma9or termination reaction in(ol(es the Ce 5 component of the redox system. k t
5
!n . Ce
Ce% , dead polymer.
4sin* the steady-state assumption" deri(e a useful expression for the rate of polymerization. ake the initiator efficiency f and assume that the propa*ation reaction is the only one hich uses si*nificant :uantities of monomer. #. or acrylamide" k p/k t liter/ mol sec at # 0C and termination is by couplin* alone. ;t this temperature the half-life of isobutylryl peroxide is <.0h and its efficiency in methanol can be taken to e:ual to 0.% ; solution of 100 */liter acrylamide in methanol is polymerized ith 10-1 ! isobutyryl peroxide. &a' hat is the initial steady-state rate of polymerization+ &b' ,o much polymer has been made in the first 10 min of reaction in 1 liter of solution+
6. ne hundred liter of methyl methacrylate is reacted ith 10. mol of an initiator at 600C. &a' )hat is the kinetic chain len*th in this polymerization+ &b' ,o much polymer has been made in the first # h of reaction+ k p #.# liter/mol sec k t #.# x 10 6 liter/ mol sec =ensity of monomer 0.<5 * cm % t1/ for this initiator #0 h f 0.% 100 > methyl methacrylate & ! o ' C#,8 100 */mol' 10. moles of an initiator at 60oC.
$. Redox initiation is often used in polymerization in a:ueous system. hus , and e ion can be used to initiate the polymerization of acrylamide in ater. =eri(e an expresiion for the steady-state rate of polymerization. 3n this case7 , e
k
,. , - e%
8. &a' 3n a free-radical polymerization in solution the initial monomer concentration is increased by a factor of 10. &i' ,o is the rate of polmerization affected :uantitati(ely+ &ii' )hat chan*e takes place in the number a(era*e de*ree of polymerization+ &b' 3f the monomer concentration as not chan*ed but the initiator concentration as hal(ed instead7 &i' )hat is the chan*e in the rate of polymerization. &ii')hat is the chan*e in the number of a(era*e de*ree of polymerization+
<. Consider the chain transfer reaction that occur in the radical-initiated homopolymerizations of isopropenyl acetate and methacrylonitrile. )hich monomer yields hi*h-molecular-ei*ht polymers is con(entional free radical polymerizations+ ?xplain the difference.
10. @inyl acetate as polymerized in a free-radical reaction. he initial monomer concentration as 1 mol/ liter and is concentration after 1 h as 0.8# mol/liter. Chloroform as present as chain transfer a*ent"ith concentrations 0.01 mol liter at time zero and 0.00$ mol liter after 1h. )hat is the chain transfer constant C in this case+
11. ;n en*ineer is studyin* the azodiisobutyronile-initiated polymerization of butyl acrylate in solution. Ahe ants to chan*e to monomer and initiator concentrations so as to double the initial steady-state rate of polymerization ithout chan*in* the number a(era*e de*ree of polymerization of the polymer or the reaction temperature. ,o should she proceed+
