effects of on-line melt blending of polypropylene with...

Effects of On-line Melt Blending ofPolypropylene with Polyamide 6 on the Bulk

and Strength of the Resulting BCF Yarn

Polypropylene filament yarns, when compared with polyethyleneterephthalate andpolyamide yarns have lower stretchability after being false twist textured. To over-come this deficiency, other researchers have tried to lower the degree of crys-

tallinity of this fibre by either tension annealing or blending it with polyethyleneterephtha-late and polystyrene. These physical or chemical modifications have not yet achieved asatisfactory level of enhancement of the textureability of polypropylene. Considering theimportance of BCF polypropylene yarns, in this research, the effect of blendingpolypropylene with12.5 and 25 % of polyamide 6 on the bulk of the final bulked continu-ous filament (BCF) yarn has been investigated. The results show that although bothcrimp contraction and crimp modulus increase with the temperature and pressure of hotair during texturing, but blending polypropylene with even 25% of polyamide 6 does notenhance the textureability of BCF yarns. Also, the reduction in the crystallinity of the yarnsdoes not lead to any improvement in the textureability of the polypropylene BCF yarns.

polymer blending;

polypropylene;

polyamide 6;

continuous filament;

strength.

A B S T R A C T

Key Words:

(*)To whom correspondence should be addressed.E-mail: [email protected]

INTRODUCTION

Hossein Tavanai1,*, Mohammad Morshed, and Seyed Majid Hosseini

Textile Engineering Department, Isfahan University of Technology, Isfahan-84156, I.R. Iran

Received 26 February 2003; accepted 15 July 2003

Polypropylene has been gainingincreasing importance in the past 20years. The production of polypropy-lene continuous filament yarns near-ly doubled from 1.380 in 1993 to2.661 million tones in 2000 [1]. Thisincrease in importance and produc-

tion can be related to parameters suchas: low price, easy productionprocess with low energy consump-tion and excellent resistance againstmany chemicals. The application ofpolypropylene both in staple andcontinuous filament form covers a

Iranian Polymer Journal

1122 (5), 2003, 421-430

422

Effects of On-line Melt Blending of Polypropylene ... Tavanai H. et al.

Iranian Polymer Journal / Volume 12 Number 5 (2003)

wide spectrum in both home and industrial textiles. Forexample, bulked continuous filament (BCF)polypropylene yarns are used widely for the productionof floor covering such as tufted and woven carpets. InBCF process also known as hot fluid texturing, spin-ning, drawing and texturing of polypropylene are car-ried out continuously. Production of BCF yarn is a verycommon practice today [2].

A major shortcoming of polypropylene filamentyarns, when compared with polyethyleneterephthalate(PET) and polyamide (PA) yarns is its considerablylower stretchability after being false twist textured.This has been studied by Mohaddes Mojtahedi [3] andSengupta et al. [4-7]. On the whole it can be said thatthe high degree of crystallinity and low heat conductiv-ity of polypropylene have been held responsible for therather poor stretchability of polypropylene yarns aftertexturing. These researchers have tried a way to over-come this deficiency by lowering the degree of crys-tallinity of this fibre by the following two routes:

- Tension annealing- Blending polypropylene with polyethylenetereph-

thalate and polystyreneSengupta et al. [5] showed that tension annealing at

low temperature with the result of lowering the crys-tallinity, increased the stretchability of false twist tex-tured polypropylene yarns to rather a small extent. As amatter of fact, crimp rigidity values (%) of 11.5, 19, 20and 23 for parent yarns increased to 17.5, 21, 22 and 23for annealed yarns. He also showed that as far as thestretchability is concerned, increasing the temperatureof annealing tension has a negative effect. In anotherpart of his investigation Sengupta [6] blendedpolypropylene with 5% of polystyrene, This led to adecrease of the degree of crystallinity from 70% to34%. The stretchability (crimp rigidity) of this blendedyarn increased from 5% for the 100% polypropyleneyarn to 15%. This is of course far from values such as45-50 % for the crimp rigidity of normal polyamideand polyester yarns.

Following the work of Mohaddes Mojtahedi andSengupta et al. [4,5,6,7], Khosroshahi [8] blendedpolypropylene with 1%, 3%, and 5% of polyamide 6 aswell as Vectra LKX 1170, a liquid crystal polymer.Blending with polyamide 6 was carried out in the pres-ence and absence of Overac CA100 as compatibilizer.In Khosroshahi s work [8], blending polypropylenewith liquid crystal polymer did not lead to considerablechanges in the textureability of polypropylene yarn. In

fact, the stretchability (crimp contraction) of 140f36polypropylene yarn blended with 0, 1, 3, and 5% of thisliquid crystal polymer has been reported as 14 (0.7),15.5 (1.1), 14.4 (0.4) and 11.7 (0.6). Values in thebracket show the standard deviation. Blendingpolypropylene with up to 5% polyamide 6 in theabsence of compatibilizer lowered the stretchability ofthe false twist textured yarn by about 2-2.5%. Howev-er, with compatibilizer, the values of crimp contractionfor the polypropylene yarn blended with 0, 2, and 5%polyamide 6 was 14 (0.7), 13.5 (0.6) and 15.9 (1.1).Again it seems that blending polypropylene with up to5% of polyamide 6 even in the presence of compatibi-lizer does not lead to considerable improvement in thestretchability of polypropylene yarn.

Research activities concerning polyblending ofpolypropylene with polyamide 6 dates back to 1974,when Ide and Hasegawa [9] reported that the dispersedpolyamide 6 in polypropylene matrix leads to an unsta-ble situation in extrusion and spinning faces difficulty.Ide made use of maleic anhydride as a compatibilizerfor the first time to make the miscibility of polypropy-lene with polyamide 6 and also the spinning of thisblend possible. This substance is still being used as acompatibilizer. In this context, parameters such asmolecular weight, molecular chain length and sidechains have considerable effect on the function of com-patibilizer [10]. It has been reported that blendingpolypropylene with polyamide 6 affects properties suchas moisture regain, melting point and viscosity [11,12,13].

To summarize the research already carried out inthis field, it can be said that the physical or chemicalmodifications made to polypropylene has not yetachieved a satisfactory level of enhancement of its tex-tureability.

Considering the importance of BCF polypropyleneyarns, it is the aim of this research to investigate theeffect of blending polypropylene with a higher portionof polyamide 6 namely 12.5 and 25 % on the bulk ofthe final BCF yarn.

EXPERIMENTAL

MaterialsIn this research, polypropylene granulate from TabrizPetrochemicals was used. These granulates had a MFIvalue of 16 and a melting point of 170 C. Polyamide 6

Effects of On-line Melt Blending of Polypropylene ...Tavanai H. et al.

Iranian Polymer Journal / Volume 12 Number 5 (2003) 423

granulate intended for blending with polypropylenegranulate was provided by Parsilon Company. Themelting point of polyamide 6 was 220 C. As compati-bilizer, maleic anhydride (industrial grade) and as ini-tiator, 2,5 dimethyl-di(tert-butyl peroxy) hexanol fromAkzo Company (Holland) was used. The compatibiliz-er and initiator were first mixed with polypropylenepowder (MFI = 25). The percentage of compatibilizerand initiator in this mixture was 5% and 0.003%,respectively. This mixture (2%) was mixed withpolypropylene and polyamide 6. The choice of theamount of compatibilizer was based on using the mini-mum quantity that led to acceptable spinability.

As spin finish, a 17% emulsion of Rolfil PN/80(Cesulpinia- Italy) was used. This was added to theyarn before the first godet. The spin finish pick up wasabout 0.5%.

EquipmentThe equipment used in this research was as follows:

- Twin screw extruder (46 mm diameter, L/D = 44,Frester, Japan) for preparing the compatibilizer mix-ture. This extruder consisted of 9 heating zones with atemperature profile of 189, 190, 191, 189, 185, 181,178, 175 and 170 C.

- Pilot spin-draw-texture (BCF) line with two spin-nerets each having 120 trilobal orifices. The extruderhad 6 heating zones.

- Electronic hank winder (Hans Bearer AG,Switzerland) for preparing the hanks needed for crimpproperty measurements.

- Laboratory Oven (Teb Azemoon-Iran) for crimpdevelopment

- Zwick tensometer (Model 1446) based on CREmethod for measuring the tenacity of the samples.

- Manual crimp property instrument for the meas-urement of crimp properties.

- MOMEM (MB100) FTIR Spectroscope (Braunand Hartmann) for measuring the crystallinity of thesamples.

Sample ProductionThree groups of BCF yarns were produced as follows:

- 100% Polypropylene- 87.5% Polypropylene and 12.5% polyamide 6- 75% Polypropylene and 25% polyamide 6

The temperature profile of the 6 heating zones ofthe extruder for the production of three above men-tioned groups of yarns was, respectively, as follows:

190, 195, 200, 205, 210 and 215 C215, 220, 225, 230, 235 and 235 C215, 220, 225, 230, 235 and 235 C

The draw ratio between the first (slow) and second(fast) godet was 4.5.

The texturing conditions were chosen according tothe following matrix leading to 20 samples for eachgroup:

Hot air temperature ( C) 110 120 130 140 150Hot air pressure (bar = kgf/cm2) 1 2 3 4Values out of the above mentioned range were

either not practicable or led to no considerable changein the properties of the yarns. The BCF yarns with a lin-ear density of 1600 decitex were produced with a speedof about 1050 m/min. Considering the type of themachine used, higher speeds led to unacceptable yarnbreakage. The traverse speed during winding was 212cycles/min.

MethodsBulk and stretchability of the yarns were measuredaccording to DIN 53840. Five specimens were chosenfor each experiment and the average of crimp contrac-tion as well as crimp modulus values was calculated.

Strength of yarns was measured by Zwick ten-someter according to ASTM: D2256-80. 20 specimenwere chosen for this test.

Degree of crystallinity of the BCF yarns for thepurpose of comparison was measured by the FTIRspectrum obtained from BOMEM MB100. The speci-men were prepared by mixing 100 parts of the yarn inpowder form with 1 part KBr in the form of a thin film.

RESULTS AND DISCUSSION

Tables 1-3 show the average values and the relatedcoefficient of variation for crimp contraction, crimpmodulus and tenacity of BCF textured 100%polypropylene, 87.5% polypropylene, 12.5%polyamide 6 and 75% polypropylene, 25% polyamide6 yarns.

Figures 1-3 and 4 - 6 show three dimensionally, thevariation of crimp contraction and crimp modulus ver-sus the temperature and pressure of hot air during BCFtexturing of the yarns, respectively. As it can be seenand as the analysis of variance carried out on the datashows, both crimp contraction and crimp modulus

424



increases with the temperature and pressure of hot air. The maximum crimp contraction obtained for the

blends containing 100%, 87.5% and 75% polypropy-lene is 6.8%, 5.3% and 5.3%, respectively. The threedimensional picture is very similar for the three cases.The corresponding maximum crimp modulus valuesare 5.3%, 4.4% and 4.3%. Again the three dimensionalpictures for the crimp modulus are very similar. Fromthese results, it can be concluded that blendingpolypropylene with even 25% of polyamide 6 will notenhance the textureability of BCF yarns. These resultsagree with the observations made by Khosroshahi et al.[8]. It seems unlikely that blending polypropylene withrelatively big portions of polyamide 6 such as 12.5%and 25% will enhance the textureability of the falsetwist textured polypropylene yarns. However, this

needs a separate research. Figures 7-9 show the three dimensional variation of

the tenacity of the BCF yarns. From these pictures, itcan be concluded that similar to crimp contraction andcrimp modulus, blending the polypropylene withpolyamide 6 does not lead to any improvement for thetenacity of the resulting BCF yarns. As it can be seen,there is even a general decrease of about 2-3 cN/tex forthe 87.5% polypropylene and 12.5% polyamide 6 blendwhen compared with 100% polypropylene. The tenaci-ty decreases further for 2-3 cN/tex , as the portion ofpolyamide 6 is increased to 25%. Khosroshahi [8] hasalso observed similar results.

Figures 7-9 show also the effect of the temperatureand pressure of hot air used as hot fluid in BCF textur-ing. As it can be seen, in most cases increasing temper-

Figure 2. Variation of crimp contraction versus temperature

and pressure of hot air during BCF texturing of 87.5%

polypropylene and 12.5% polyamide 6 blend yarn.


and pressure of hot air during BCF texturing of 75%

polypropylene and 25% polyamide 6 blend yarn.

Figure 4. Variation of crimp modulus versus temperature and

pressure of hot air during BCF texturing of 100% polypropy-

lene yarn.


and pressure of hot air during BCF texturing of 100%

polypropylene yarn.



Table 1. Crimp contraction, crimp modulus and tenacity of BCF textured yarn (100% polypropylene).

Crimp contraction

(%)

Crimp modulus

(%)

Tenacity

(cN /Tex)

Temperature

(ºC)

Pressure

(bar)

X(CV)

X(CV)

X(CV)

3.2(6.6)3.4

(6.7)3.7

(6.2)3.5

(8.6)3.5

(4.6)4.2

(8.1)4.5

(9.7)4.3

(6.3)3.7

(8.4)3.8

(5.8)4.5

(12.8)4.6

(6.6)4.6

(7.0)5.3

(3.9)5.1

(7.0)4.3

(6.6)4.8

(6.7)6.1

(5.8)6.9

(3.6)6.6

(6.1)5.9

(2.8)6.6

(2.5)6.6

(1.6)6.2

(2.4)

2.7(10.4)

2.8(10.6)

3.2(6.9)2.9

(10.3)2.9

(5.7)3.7

(6.5)3.8

(11.1)3.6

(6.3)3.3

(9.7)3.3

(6.6)3.7

(13.9)4.0

(7.6)3.7

(7.6)3.9

(4.2)3.9

(7.3)3.6

(7.6)3.4

(9.1)4.4

(7.8)5.0

(4.5)5.0

(11.8)4.2

(1.4)4.8

(4.6)4.8

(3.3)4.4

(3.5)

18.6(4.3)17.1(4.2)16.1(4.3)16.4(5.0)17.0(4.8)16.8(5.9)17.1(5.7)16.7(5.5)17.5(5.2)16.8(5.4)16.3(5.2)16.0(6.5)16.8(7.7)15.7(5.0)15.4(3.7)16.8(3.6)16.2(3.7)15.7(4.5)15.6(5.2)15.6(4.1)16.6(4.6)16.5(3.7)16.3(4.0)16.1(4.7)

110

110

110

110

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120

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130

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140

150

150

150

150

160

160

160

160

1

2

3

4

1

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1

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1

2

3

4

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Table 2. Crimp contraction, crimp modulus and tenacity of BCF textured yarn (87.5% polypropylene and 12.5% polyamide 6).

Crimp contraction

(%)

Crimp modulus

(%)

Tenacity

(cN /Tex)

Temperature

(ºC)

Pressure

(bar)

X(CV)

X(CV)

X(CV)

3.2(7.7)4.1

(5.9)3.5

(2.3)3.9

(2.9)3.1

(4.6)3.8

(5.0)4.4

(1.5)3.7

(5.9)3.9

(9.9)4.4

(6.0)4.7

(1.3)4.8

(4.4)4.3

(6.7)4.8

(2.7)5.0

(4.7)5.1

(5.5)4.8

(6.7)5.3

(4.1)5.4

(7.3)5.2

(2.7)4.9

(7.6)5.1

(1.5)5.3

(2.1)5.0

(1.6)

2.8(8.8)3.5

(4.0)3.1

(3.2)3.5

(2.4)2.7

(5.4)3.3

(7.8)4.0

(1.7)3.3

(6.7)3.5

(10.9)3.8

(10.2)4.1

(1.7)4.1

(4.9)3.8

(9.0)4.1

(3.9)4.3

(3.8)4.3

(6.4)4.0

(7.4)4.4

(5.1)4.7

(8.1)4.4

(3.2)4.3

(8.7)4.5

(1.7)4.7

(2.2)4.4

(2.1)

15.1(4.4)14.8(4.2)15.1(4.5)16.0(4.6)16.2(3.8)15.2(4.1)15.3(4.3)15.0(3.9)16.2(3.9)17.2(4.3)15.0(4.9)15.7(4.2)14.5(4.0)14.3(4.8)15.4(5.0)15.7(5.5)15.7(6.2)14.7(4.4)14.5(4.8)14.2(4.1)14.2(5.5)13.7(4.1)13.4(4.4)13.5(4.2)

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110

110

110

120

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120

120

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140

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150

150

160

160

160

160

1

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4

1

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4

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3

4

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4

1

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3

4

1

2

3

4



Table 3. Crimp contraction, crimp modulus and tenacity of BCF textured yarn (75% polypropylene and 25% polyamide6).

Crimp contraction

(%)

Crimp modulus

(%)

Tenacity

(cN /Tex)

Temperature

(ºC)

Pressure

(bar)

X(CV)

X(CV)

X(CV)

2.9(2.7)3.4

(7.0)3.0

(2.5)3.3

(5.4)2.8

(4.5)3.4

(3.0)3.9

(6.1)4.1

(1.4)3.5

(2.4)4.4

(2.3)4.4

(1.9)4.7

(3.6)5.0

(2.4)4.9

(4.0)5.4(3)5.4

(2.3)4.7

(5.6)5.0

(3.7)4.9

(4.4)5.0

(3.8)4.4

(2.3)5.0

(2.6)5.5

(7.8)5.3

(5.6)

2.4(6.0)2.9

(5.5)2.6

(3.2)2.8

(6.5)2.4

(6.1)2.8

(3.7)3.2

(8.5)3.1

(4.1)2.7

(3.1)3.4

(3.6)3.4

(2.8)3.7

(4.5)3.8

(4.2)3.8

(6.5)4.3

(3.1)4.2

(3.0)3.7

(7.3)4.1

(4.2)3.8

(3.4)3.8

(4.3)3.5

(2.5)3.9

(4.5)4.2

(8.2)4.3

(6.7)

12.9(6.3)13.1(5.5)12.8(5.3)13.3(5.2)12.5(4.2)13.6(5.5)12.6(3.1)12.9(4.2)13.2(4.6)12.9(7.5)12.8(4.7)13.0(6.1)12.5(5.5)13.2(3.7)13.0(3.2)12.0(3.1)12.9(3.1)12.5(3.6)12.0(3.8)12.0(3.6)12.0(3.2)12.5(3.0)11.8(3.5)12.3(3.7)

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160

160

1

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428




pressure of hot air during BCF texturing of 87.5% polypropy-

lene and 12.5% polyamide 6 blend yarn.


pressure of hot air during BCF texturing of 75% polypropy-

lene and 25% polyamide 6 blend yarn.

Figure 8. Variation of tenacity versus temperature and pres-

sure of hot air during BCF texturing of 87.5% polypropylene

and 12.5% polyamide 6 blend yarn.


sure of hot air during BCF texturing of 100% polypropylene

yarn.


sure of hot air during BCF texturing of 75% polypropylene

and 25% polyamide 6 blend yarn.

Figure 10. FTIR Spectrum of BCF textured 100% polypropy-

lene yarn (air pressure = 3 bar, air temp. = 150 ºC).

0

.01

.02

.03

1200 1000 800 600

Wavenumber(cm-1)

ature and pressure decreases the tenacity of the BCFyarns. This is especially true for a simultaneousincrease of temperature and pressure.

Figures 10-12 show the FTIR spectrum of the BCFyarns with highest crimp contraction from each group(air pressure = 3 bar, air temp. = 150 C) obtained byBOMEM (MB100), FTIR Spectrometer. The percent-age crystallinity of 100%, 87.5% and 75% polypropy-lene BCF yarns calculated from the FTIR spectrumwere 92.06, 89.23 and 85.33, respectively. As it can beseen, the reduction in the crystallinity of the yarns inthe order of magnitude observed here does not onlylead to any improvement in the textureability of thementioned polypropylene yarns, but also leaves somenegative effect. Mohaddes Mojtahedi did not alsoobserve any improvement in the stretchability of 100%polypropylene false twist textured yarns with lower

crystallinity. These results cast some uncertainty overthe claims by Sengupta that generally lowering thedegree of crystallinity can improve the textureability ofpolypropylene yarn. In fact, it calls for a more thoroughinvestigation in this field which should throw somelight on this matter. Considering the fact that blendingpolypropylene with polyester or polystyrene has posi-tive effects on the textureability of polypropyleneyarns, a research is needed to study morphology param-eters such as crystallite size, crystallite orientation,degree of perfection of the crystallites and the state ofthe amorphous regions. This may lead to a better under-standing of the parameters affecting the textureabilityof polypropylene and act as a help to improve this prop-erty.

As far as the tenacity results are concerned, thedecrease in the tenacity due to the introduction ofpolyamide 6 can be related to the decrease in the crys-tallinity shown by the FTIR analysis. Moreover, oneshould not forget that the possibility of the formationof defects such as voids as a result of blendingpolyamide 6 with polypropylene could also contributeto the drop in the tenacity. Separation of these two fac-tors needs further detailed investigations.

CONCLUSION

The results showed that both crimp contraction andcrimp modulus of the 100% polypropylene as well asthe blends containing 12.5% and 25% polyamide 6increases with the temperature and pressure of hot airduring BCF texturing process. However, blendingpolypropylene with even 25% of polyamide 6 does notenhance the textureability of BCF yarns, although theresults obtained by the FTIR analysis showed thatblending polypropylene with polyamide 6 does reducesthe crystallinity of BCF yarns. This finding contradictsthe belief that the shortcomings in the textureability ofpolypropylene is due to its high degree of crystallinityand it could be overcome by lowering the degree ofcrystallinity. A more detailed study of morphologyparameters is proposed.

The temperature and pressure of hot air used as hotfluid in BCF texturing leads to a decrease in tenacity inmost cases, especially when temperature and pressureare increased simultaneously. It is also concluded that



Figure 11. FTIR Spectrum of BCF textured 87.5% polypropy-

lene, 12.5% polyamide 6 blend yarn (air pressure = 3 bar, air

temp. = 150ºC)

Wavenumber (cm-1)

.03

.02

.01

0

1200 1000 800 600

Figure 12. FTIR Spectrum of BCF textured 75% polypropy-

lene and 25% polyamjde 6 blend yarn (air pressure = 3 bar,

air temp. =150 ºC)

Wavenumber (cm-1)

0

.01

.02

1200 1000 800 600

430



blending polyamide 6 with polypropylene leads to adecrease for polypropylene and polyamide 6 blendwhen compared with 100% polypropylene. Thedecrease in the crystallinity as well as possible forma-tion of structural defects as a result of blending is heldresponsible for the decrease in tenacity.

ACKNOWLEDGEMENT

The authors wish to thank Mr Hossein Ghazvini,Managing Director of Pars Polypropylene Company(Isfahan-Iran) for his technical assistance. Furthermore,they are also grateful to Miss F. Ali Hosseini and Mr A.Ataian for their FTIR assistance.

REFERENCES

1. Beal A., Current world market trends for PP fibres, Chem.Fib. Int., 47, 344-350 (1997).

2. Gupta V.B. and Khotari V.K., Manufactured Fibre Tech-nology, Chap. 16, Chapman & Hall, London, 471-486(1997).

3. Mohaddes Mojtahedi M.R., False twist texturing ofpolypropylene yarns, Ph.D. Thesis, The University ofLeeds, England (1996).

4. Sengupta A.K., Sen K., and Mukhopadhyay A., Falsetwist texturization of polypropylene multifilament yarns,Part I: Time-temperature effects, Text. Res. J., 56, 281-286(1986).

5. Sengupta A.K., Sen K., and Mukhopadhyay A., Falsetwist texturization of polypropylene multifilament yarns,Part II: Reducing feeder yarn crystallinity through tensionannealing, Text. Res. J., 56, 389-392 (1986).

6. Sengupta A.K., Sen K., and Mukhopadhyay A., Falsetwist texturization of polypropylene multifilament yarns,Part III: Reducing feeder yarn crystallinity through meltblending with small amounts of polyester and poly-styrene, Text. Res. J., 56, 425-430 (1986).

7. Sengupta A.K., Sen K., and Mukhopadhyay A., Falsetwist texturization of polypropylene multifilament yarns,Part IV: Structural influences on dye uptake, Text. Res. J.,56, 511-515 (1986).

8. Khosroshahi A. and Seyed Esfahani M., The effect ofpolymer blends of polypropylene with polyamide 6 andliquid crystal polymer on its textureability, Amir Kabir J.,13, 614-622, Autumn (2002).

9. Ide F. and Hasegawa A., Studies on polymer blends ofnylon 6 and polypropylene or nylon 6 and polystyrene,using the reaction of polymer, J. Appl. Polym. Sci., 13,963-974, (1974).

10. Lewin M. and Preston J., Hand-Book of Fibre Scienceand Technology, High Technology Fibres, Chap.1, 1-50,Chapman and Hall (1986).

11. Takahashi T., Konda A., and Shimitzu Y., Viscosity ofpolypropylene /polyamide 6 blends, Sen-Igakaishi, 52,573-581 (1996).

12. Takahashi T. and Konda A., Effect of viscosity ratios onstructure polypropylene/ polyamide 6 melt blends, ibid,52, 507-515 (1996).

13. Sachine N. and Surekha D., Relationship between mor-phology and mechanical properties of binary and compat-ibilized ternary blends of polypropylene and nylon 6, J.Appl. Polym. Sci., 61, 97-107 (1996).

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