Fisheries Research 81 (2006) 326330

The effect of natural sunlight on the s6 multifilament and monofilament fi

ayaTechnay 20

Abstract

The effec olyamof different drawelongation a d elosamples due xposuof elongatio 2006 Else

Keywords: W ation

1. Introdu

Polyamcotton/hemnous produis available as multifilament twisted and monofilament singletwines for netting purposes. In the gill net sector, the use ofPA as multifilament twine is the commonest material used forgill net fabrication (Radhalakshmy et al., 1993). Initially, PAmultifilamegill nets. Inadopted thi0.23 mm dwas later reament of 0replacemen

The resproperty desunlight walem has nopolymer m

Corresponnology, Matsyfax: +91 484

E-mail ad(S.N. Thomas

e inreatatherructungth

(Achhammer et al., 1953; Winslow and Hawkins, 1967; Liu etal., 1995). Molin (1959) reported that one of the disadvantages ofPA nets for fishing purposes was their relatively high sensitivityto ultraviolet rays. Carrothers (1957) reported that on average,

0165-7836/$doi:10.1016/jnt and later, PA monofilament became popular forthe quest for better catching efficiency, fishermen

nner materials, as the PA monofilament of 0.20 andiameter used earlier for gill nets employed inshoreplaced by 0.16 mm diameter. The use of PA monofil-.16 mm diameter in webbing necessitates frequentt as this lasts for 69 months only.

istance to photo-degradation is considered a basictermining the durability of the material. Exposure tos known to degrade most natural fibres, and the prob-t been overcome with the development of syntheticaterials. Resistance to light and weathering was much

ding author. Present address: Central Institute of Fisheries Tech-apuri P.O., Cochin 682029, Kerala, India. Tel.: +91 484 2666845;

2668212.dresses: saly t@rediffmail.com, salythomas@ciftmail.org).

a well-maintained PA net loses about 25% of its strength duringthe first season and another 10% during the second season. Whenconducting weathering and light exposure tests, loss in break-ing strength was commonly used as a measure of the amount ofdegradation (Egerton and Shah, 1968; Little and Parsons, 1967;Singleton et al., 1965). Al-Oufi et al. (2004) assessed both thebreaking strength and elongation capability as measures of theeffects of solar radiation on PA continuous filaments.

Weathering studies conducted in India on fishing net twineshave been confined to polyethylene (PE) and PA multifilamenttwines (Meenakumari et al., 1985, 1995; Meenakumari andRavindran, 1985; Meenakumari and Radhalakshmi, 1988). Theweathering resistance of PA monofilament has not been studiedin India. With the recent popularity of PA monofilament twines,the assessment of its weathering resistance has become veryimportant. A study of the photo-degradation of PA monofilamentyarn in comparison to PA multifilament twine was, therefore,undertaken.

see front matter 2006 Elsevier B.V. All rights reserved..fishres.2006.06.012Saly N. Thomas , C. HridSchool of Industrial Fisheries, Cochin University of Science and

Received 6 October 2005; received in revised form 8 M

t of natural sunlight on four polyamide monofilament yarns and four pRTex were exposed to 180 days solar radiation and sub-samples weret break. Significant reduction in both breaking strength (P < 0.01) anto weathering. Breaking strength reduced linearly with the period of e

n at break.vier B.V. All rights reserved.

eathering; Polyamide; Monofilament; Multifilament; Breaking strength; Elong

ction

ide (PA) became the first synthetic material to replacep in India for fishing gear construction and its indige-ction started in 1962 (Meenakumari et al., 1993). PA

the samvery g

Weular stof stretrength of polyamideshing net materialsnathanology, Cochin 682016, Kerala, India06; accepted 16 June 2006

ide multifilament twines was studied. The samples, eachn at intervals to study the effect on breaking strength and

ngation at break (P < 0.01) have been recorded in the testre, while no such linear relationship was found in the case

all-vegetable fibres, while synthetic fibres showeddifferences in that respect (Klust, 1959).ing causes modification and breakdown of the molec-re of polymers, which in turn results in the loss, extensibility, general durability and appearance

S.N. Thomas, C. Hridayanathan / Fisheries Research 81 (2006) 326330 327

2. Materials and methods

The testament yarndiameter (T0.32 mm (Tspecificatio455), 210 dThe diamemicroscopeon aluminiuwith sufficbuilding upnorth-southsunlight wday. Marinon Willingof noon rada solar collshine Interranging frowere remo

and elonga180 days ofber to Maytest site. Durainfall in trespectivelsamples wea Universaaccordance(40 test samat each sam

Breakinlated as a pecontrol twunserviceavalue (Branthe same w

3. Results

3.1. Assess

The chaResults shbreak of saof varianceproperties.icant reduc(P < 0.01) ispective ofits initial bmultifilameextension aand PA muthe end of 1

Table 1Specifications and physical properties of samples studied

pecifi

ype

A moA moA moA moA mu10 d

A mu10 d

A mu10 d

A mu10 d

re wn ped. Inn pe

< 0.0etw

05)nt msolanth-give

due tbect, whbrea

me ied inf allph dposufor an thre wthe material. The present observations were in confor-ith those of Meenakumari and Radhalakshmi (1988) formultifilament twines. However, in the case of elongationk, no linear relationship was found between the reductiongation and the increase in exposure time.ervation of the retention of breaking strength and exten-pability showed that PA multifilament was more suscepti-eathering than PA monofilament. To confirm the greater

tibility of multifilament to weathering, the retention ofh features of PA monofilament and multifilament sam-

f comparable thickness were analysed. It was seen thatltifilament of 210 d 1 2 (0.37 mm diameter) retained5.3% of the breaking strength while PA monofilamentmm diameter retained 70.4% of strength (Table 2). This

that PA multifilament was more susceptible to weatheringonofilament. Alsayes et al. (1996) also observed highermaterial comprised samples of: (i) PA 6 monofil-of four specifications, viz. of diameter 0.16 mm

ex 23), 0.20 mm (Tex 44), 0.23 mm (Tex 50) andex 90) and (ii) PA 6 multifilament twine of fourns, viz. 210 d 1 2 (Rtex 51), 210 d 6 3 (Rtex 9 3 (Rtex 683) and 210 d 12 3 (Rtex 911).

ter of the samples was measured using a travelling. The test samples were suspended without tensionm nails set 1 cm apart on a rectangular wooden frame

ient ventilation and to prevent the temperature fromexcessively. The mounted samples were held in adirection at an angle of 45 on the roof top where

ould fall directly on the samples during the wholee atmospheric conditions prevailed at the test sitedon island, Cochin, India. The month-wise amountiation during the exposure period was recorded byector (model SE-MSR 3003A36) designed by Sun-national to measure global radiation at wave lengthsm 0.3 to 3m. Sub-samples from the test materialved for measuring the change in breaking strengthtion at break after 8, 15, 30, 45, 60, 90, 120, 150 andexposure. The test exposure was done from Decem-

, when there was almost continuous sunshine at thering this period, the mean monthly temperature and

he area ranged from 30.6 to 32.7 C and 0 to 503 mm,y. The retrieved samples and the unexposed controlre tested for breaking strength and elongation using

l Testing Machine (UTM) of model ZWICK 1484 inwith Anon (1971). Five replicates of each sampleples, viz. n = 5 per sample specification) were testedpling and the mean value was taken.

g strength after a given period of exposure was calcu-rcentage of the mean initial strength of the unexposed

ines of each test sample. The twine is consideredble when the strength is reduced to 50% of its originaldt, 1959). Elongation at break was also calculated inay.

and discussion

ment of mechanical strength properties

racteristics of the samples tested are given in Table 1.owed reduced breaking strength and elongation atmples exposed to sunlight (Table 2). An analysis(ANOVA) showed consistent reduction of these

At the end of 180 days of exposure, there was signif-tion in breaking strength and in elongation at breakn all the samples. PA monofilament, on average (irre-thickness of different samples) retained 64.6% of

reaking strength at the end of 180 days whereas PAnt retained only 46.6% (Table 2). In the case of thet break, PA monofilament, on average retained 57.8%ltifilament retained 53.2% of the original values at80 days of exposure (Table 2).

No. S

T

1 P2 P3 P4 P5 P

(26 P

(27 P

(28 P

(2

Thebetweeretainebetweeals (Pences b(P < 0.differesity ofthe moperiodrationothers,of ligh

Thesure tiobservyarn othe graand exabovebetweeexposulife ofmity wthe PAat breain elon

Obssion cable to wsuscepstrengtples oPA muonly 2of 0.32showsthan mcation Weight/m (g)

Strength(N)

Elongatonat break (%)

Diameter(mm)

nofilament 0.16 0.036 14.8 27.7nofilament 0.2 0.044 16.4 34.7nofilament 0.23 0.047 21.7 32.8nofilament 0.32 0.050 36.3 35.1ltifilament

1 2)0.37 0.053 26.6 27.1

ltifilament6 3)

1.04 0.483 210.7 39.9

ltifilament9 3)

1.30 0.725 312.4 35.8

ltifilament12 3)

1.54 0.98 513.9 34.3

as substantial difference between materials andriods of exposure in terms of strength and elongationthe case of strength, there was significant differenceriods of exposure (P < 0.001) and between materi-01). In the case of extension too, significant differ-een exposure time (P < 0.001) and between materialswere found. The different reductions in strength inonths could be due to seasonal changes in the inten-r radiation on the earth surface. This is evident fromwise amount of noon radiation during the exposuren in Table 3. Indurfurth (1953) reported that deterio-o weathering was more rapid at certain locations thanause of differences in the duration of the wavelengthsich particularly damaged the fibre.king strength reduced linearly with increase in expo-ndicating that the process is continuous. This was

the case of multifilament twine and monofilamentdimensions. The regression equation when fitted toepicting the relationship between breaking strengthre time showed a linear relationship (R2 = 0.903 andll twine dimensions). This shows that the relationshipe rate of deterioration of strength and the period ofas linear and this can help in predicting the service

328 S.N. Thomas, C. Hridayanathan / Fisheries Research 81 (2006) 326330

Table 2Breaking strength and elongation at break as a percentage of initial values

Exposure period (days) 0.16 mm diameter 0.2 mm diameter 0.23 mm diameter 0.32 mm diameterStrength Elongation Strength Elongation Strength Elongation Strength Elongation

(a) PA monofilament0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.08 99.3 94.7 96.5 89.5 93.9 82.9 100.6 98.4

15 91.1 82.6 90.3 83.1 93.2 95.4 97.1 93.230 83.6 75.2 89.7 78.7 89.2 75.0 91.8 84.645 79.6 71.6 87.2 73.2 90.4 83.2 92.2 82.560 78.1 70.7 85.3 67.6 88.5 82.3 88.9 71.590 68.8 66.4 73.4 61.2 82.1 77.1 85.8 74.4

120 57.8 59.4 66.8 60.3 73. 8 68.0 78.6 67.8150 73.9 68.9 75.1 68.6180 71.7 63.4 70.4 59.4

Exposure per 210 d 9 3 210 d 12 3n Strength Elongation Strength Elongation

(b) PA multifi0 100.0 100.0 100.0 100.08 92.1 90.6 96.9 101.9

1530456090

120150180

degradationon monofil

A criterrial, basedgation, beidurabilityviz. 0.16,ing strengtoriginal levthe 210 d retention ogreater thicRadhalaksh

3.2. Effect

The effenetting yar

Table 3Monthly aver

S. No. Mo

1 De2 Jan3 Fe4 Ma5 Ap6 Ma

s offfere55.1 60.9 64.5 60.652.7 47.3 63.4 60.9

iod (days) 210 d 1 2 210 d 6 3Strength Elongation Strength Elongatio

lament100.0 100.0 100.0 100.0

87.5 85.8 90.2 92.591.4 85.7 91.5 82.582.3 73.1 81.4 77.773.2 62.3 81.3 72.762.2 60.6 75.8 81.043.1 46.8 62.3 58.433.4 41.5 55.0 60.934.3 46.5 57.1 60.225.3 35.4 45.2 53.6

by ultraviolet light on multifilament material thanament.

sampleany diion for assessing the service life of fishing net mate-on the concept of 50% retention of strength or elon-ng acceptable was considered for the evaluation of(Brandt, 1959). In monofilament, all the samples,0.20, 0.23 and 0.32 mm diameters retained break-h and extension capability above 50% level of theel after 180 days exposure. In multifilament, only12 3 samples retained 50% strength. The higher

f strength in 210 d 12 3 can be attributed to thekness of the twine in conformity with the findings ofmy and Nayar (1973).

of thickness of material on degradation

ct of weathering also depends on the thickness of thens. The ratio of surface to mass is very important. The

age noon radiation at the test site

nth Year Exposure time (days) Radiation (W/m2)cember 1998 8, 15, 30 98uary 1999 45, 60 112

bruary 1999 90 154rch 1999 120 108ril 1999 150 91y 1999 180 96

the materiaFig. 1 s

PA monofiexposure. Tple 0.16 mmincreasing47.2, 36.6,retained by

Fig. 1. Variatsunlight.89.6 78.8 93.9 97.086. 8 79.8 84.5 83.781.7 74.2 89.0 90.665.3 63.7 68.7 70.355.7 54.0 68.6 77.343.3 46.2 62.5 69.838.2 55.6 58.9 65.736.5 50.8 51.7 66.5

each material were analysed separately to discovernce in performance with respect to the thickness of

l.hows the retention in strength of each sample of

lament of different thicknesses at specific periods ofhe maximum strength loss was in the thinnest sam-diameter and the loss decreased progressively with

thickness of the sample. After 180 days of exposure,28.4 and 29.6% of the original breaking strength wassamples of 0.16, 0.20, 0.23 and 0.32 mm diameter,

ion in breaking strength with time in PA monofilament exposed to

S.N. Thomas, C. Hridayanathan / Fisheries Research 81 (2006) 326330 329

Fig. 2. Variation in elongation at break with time in PA monofilament exposedto sunlight.

respectively (Table 2). Fig. 2 shows the retention in elongation ofdifferent PAsure. The mthe thinnesof exposurevalue was rdiameter, roration of estrength.

In the cing strengtprogressive(Figs. 3 and48.3% of th210 d 1 respectiveltial elonga210 d 6

The resuthe weathewere foundper filamenmonofilamthe less noticant for th

Fig. 3. Variatsunlight.

Fig. 4. Variatto sunlight.

degraded oat 1300 C

eet ostatitinreethe

nce saviolaineactiolymety ofties dt shpre

re v

t. Altifilicknckerationextehas

e ofe inh onmonofilament samples at specific periods of expo-aximum reduction in extension was again found in

t sample (0.16-mm diameter). At the end of 180 days, 52.7, 39.1, 36.6 and 40.6% of the original extensionetained by samples of 0.16, 0.20, 0.23 and 0.32 mmespectively (Table 2.). In all cases, the rate of deteri-xtension was greater than the rate of deterioration of

ase of PA multifilament also, the loss in break-h and extension capability showed a more or lessdecrease with increasing thickness of the samples4). After 180 days of exposure, 74.7, 54.9, 63.5 and

e original breaking strength was retained by samples2, 210 d 6 3, 210 d 9 3 and 210 d 12 3,

y. Similarly 64.6, 46.4, 49.2 and 33.5% of the ini-tion value was retained by samples 210 d 1 2,

3, 210 d 9 3 and 210 d 12 3, respectively.lts indicate that filament sizes and thickness affectedr resistance. Fibres with high denier per filament

to be more resistant than fibres with low deniert. Ede and Henstead (1964) indicated that thicker

ent gave better resistance. The bigger the diametericeable is the photo-degradation, which was insignif-icker ropes as the layers below were protected by the

for a sh(1996)as a limthe degthickerresistaby ultrbe expface rethe poa variepropersunligh

Therials asunlighthe muThe ththe thidegradwouldfindingpracticbe donresearcion in breaking strength with time in PA multifilament exposed to

ditions neeother commpolypropyl

Acknowled

The firsFisheries Tout her Ph.Cochin Un

Reference

Achhammer,nisms. Naion in elongation at break with time in PA multifilament exposed

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ene.

gement

t author wishes to thank Director, Central Institute ofechnology, Cochin for granting a sabbatical to carryD. programme at the School of Industrial Fisheries,iversity of Science and Technology.

s

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The effect of natural sunlight on the strength of polyamide 6 multifilament and monofilament fishing net materialsIntroductionMaterials and methodsResults and discussionAssessment of mechanical strength propertiesEffect of thickness of material on degradation

AcknowledgementReferences