BG HHPolyme CN Ch1 Bai Tap

Polymer Center- HUTS *Phn bi tp

Polymer Center- HUTS

Polymer Center- HUTS *


Polymer Center- HUTS *Problem 3

MonomeMt xch c bnDanh phpPoly(etyl acrylat)

Poly(vinylidien clorua)


Polymer Center- HUTS *Below, molecular weight data for a polypropylene material are tabulated. Compute (a) the number-average molecular weight, (b) the weight-average molecular weight, and (c) the degree of polymerization.

Problem 7

Molecular WeightRange (g/mol)xiwi8,00016,0000.050.0216,00024,0000.160.1024,00032,0000.240.2032,00040,0000.280.3040,00048,0000.200.2748,00056,0000.070.11


Khi lng phn t v s phn b khi lng phn t Many properties of polymers are linked to the polymer chain length During polymerization not all polymer chains will grow to the same length this results in a distribution of chain lengths or molecular weights There are several ways of defining the average molecular weight

1. Number average molecular weight (Khi lng phn t trung bnh s) obtained by dividing the chains into a series of size ranges and determining the number of fraction of chainswithin each size range.

Ni - numbers of molecules MiMi represents the mean molecular weight of the size range i and xi is thefraction of the total number of chains within the corresponding size range

2. Weight-average molecular weight (Khi lng phn t trung bnh khi) is based on the weight fraction of molecules within the various size ranges

wi denotes the weight fraction of molecules within the same size interval*Polymer Center- HUTS


Distribution of molecular weights for a typical polymerNumber fractionWeight fraction*Polymer Center- HUTS


Polymer Center- HUTS *Vt liu hc (L Cng Dng)ng Ang B500 hn , mi hn nng 1 kg v2 hn , mi hn nng 250 kg 400 hn , mi hn nng 1 kg v100 hn , mi hn nng 6 kg Trng lng chung = 1000 kgTrng lng chung = 1000 kgTnh



ng kiu Ang kiu B

1000/(500+2)= 1,991000/(400+100)= 2,00[(500x1x1)+(2x250x250)]/1000=125,5[(400x1x1)+(100x6x6)]/1000= 4,00125,5/1,99= 634,00/2,00= 2c trng phn bRngHp


* is always determined by employing methods which depend upon the number of molecules present in the polymer sample. For example, colligative property such as osmotic pressure is used. is more sensitive to molecules of low molecular mass, while is more sensitive to molecules of high molecular mass. is measured by using the methods such as light scattering and ultracentrifugation, sedimentation, etc. which depend upon the mass of individual molecules.Polymer Center- HUTS


Polymer Center- HUTS * = 1,5 2,0 c nhiu polyme nh hn hoc ln hn rt nhiu gi tr trung bnh = 1 (phn tn n - monodisperse) phn t polyme c kch thc gn bng nhau.- i vi polyme ng th (c to thnh t mt loi polyme) c quan h gia khi lng phn t trung bnh v trng hp trung bnh s v trung bnh khi= H s a phn tn (Polydispersity index or heterogeneity index) - S phn b khi lng phn t c th rng hay hp v nh hng r rt n tnh cht vt l ca polyme nh chy, bn v nhit chy mm S phn b khi lng phn t


Polymer Center- HUTS *Phn li gii


Polymer Center- HUTS *Molecular wtRangeMean MixixiMi8,000-16,00012,0000.0560016,000-24,00020,0000.16320024,000-32,00028,0000.24672032,000-40,00036,0000.2810,08040,000-48,00044,0000.20880048,000-56,00052,0000.073640Molecular wt.RangeMean MiwiwiMi8,000-16,00012,0000.0224016,000-24,00020,0000.10200024,000-32,00028,0000.20560032,000-40,00036,0000.3010,80040,000-48,00044,0000.2711,88048,000-56,00052,0000.115720


Polymer Center- HUTS *Now we are asked to compute the degree of polymerization, which is possible using Equation 14.6. For polypropylene, the repeat unit molecular weight is justm = 3(AC) + 6(AH)= (3)(12.01 g/mol) + (6)(1.008 g/mol) = 42.08 g/molAnd


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