A Study on the Weldability of Simultaneous Two-Axis Drawing Nylon I=ilm

Hiroshi KIMURA, * Takuzi YAMAGUCHI, * Masaki IMACHI, **

Masakazu TsuBoKAwA*, Noriyuki MOORI*,

(Received March 10, 1972)

In this paper we describe an experimental study to obtain the welding

conditions without losing the characteristic of simultaneous two-axis drawing

nylon film.

INTRODUCTION

227

The purpose of this paper is to clarify the characteristic of simultaneous two-axis

drawing nylon film and seeking after the possibilities of welding bond, making use

of the property of thermoplastic's. Namely, molecular chain oriented by simulta­

neous two-axis drawing is considered to be set at random by welding, which causes

a great property change on both weld and heat affected zone, and thus the

characteristic of simultaneous two-axis drawing nylon film can be considered to be

done away with. The focus of the study, therefore, is to obtain the welding

conditions without losing the characteristic of simultaneous two-axis drawing nylon

filmY

EXPERIMENTAL RESULTS AND CONSIDERATION

Welding method used is heating plate weldingll • 2) and suitable conditions are set

up by studying the interrelation among heating plate shape, heating temperature,

welding pressure and welding time. Specimen used was simultaneous two-axis

drawing 6-nylon film, 0.025 mm in thickness. First, tensil strength and elongation

were recorded from tension tests on machine direction (M. D.), transverse direction

CT. D.), and a 45-degree angle direction, and microstructure was examined by X-ray

diffraction. Heat cycle influence was examined by giving heat influence from-196°C

(produced by liquid nitrogen) to 200°C (produced by hot air circulating dryer).

Specimen used in the tension test was JIS K6475 type-3 dambel type. Fig. 1 shows the

shape of welding specimen and peeling specimen. Fig. 2 & 3 shows the general structure

and important parts of welding apparatus made only for this experiments. The

suitable voltage necessary for the desired heating temperature is obtained from

* Dep. of Textile Eng.

** Textile Research Institute

228

(al JIS K 6745 Type-l

(b) Peeling test specimen. r= Welded part.

rr=:~ l' I i § =! (0) Tension test specimen.

Fig. 1 The Shape of Specimens .

.J, Pressure

A.C lOOV

Pyrometer bLIJ Cold junction I~oad

cell

1 ; Iron plate. 2 ; Asbestos. 3 Iron plate. 4 ; Heater. S Heating plate. 6 Specimen.

Recorder 7 Teflon. S i Rubber.

9 Fig. 2 Welding equipment.

i Iron plate.

Fig. 3 Heating apparatus.

A. C.lOO V regulated by slidac, and the temperature was detected from heating plate

by thermocouple. Welding pressure was

made based on lever principle and was

picked up by compression load cell and

was put into tensilon recorder. The

pressure was made quickly, and welding

time was recorded just after necessary pressure being obtained. Both up and

down side of specimen surface were cov­

ered with O.18mm teflon film mixed with

glass clothes in order that specimen stick

to neither heating plate nor rubber plate.

Specimen was preheated just before the

experiment in the hot air circulating dryer at 50°C for 25 hr. for the sake of

'llO r O--------r

[~ !-----------!j ~-~-- 100

Type.l

~ ________________ ~-i

I=:; !-----~I 1----- 79 .

Type.2

Type. 3

Fig. 4 Heating plate.

229

getting better conditions. Bubbles born at welding time are thus avoided. Heating

plate attached to the welding apparatus is made of copper, and 3 different types in

shape are shown in fig. 4. Type 1 is for peeling specimen, type 2 is for manufacturing

tensile specimen, type 3 is for inspecting the differences of joint efficiency resulted

from the various shapes of heating plate. Changes of microstructure caused by

.. ~ '-"" ~ (/) !Ii <1! .... ~ <1! .... ::I +' U td .... r..

15

3 6 9 12 15 Fracture stress (kg/rnmz )

Fig. 5 Relation between fracture stress and directional property of base material.

100'---~--~--'----r---r---,--~------,

10 20 40 80 160 Jleating time (sec.J

Fig. 7 Effect of temperature. (200°C)

<If'

.~ td .... ~ <1! ....

.~ ~ ::>

100

80

60

40

20

Fig. 6 Relation between ultimate strain and directional property of base material.

100

I 0 0 0

0

50

5

0-----6--0----0

10

10 20 40 Immersion time (days)

Fig. 8 Fracture stress and ultimate strain of nylon film immersed in liquid nitrogen.

230

100~---r---"--r-----;------'

5~--+---4----~--------+------~

5~--4----+----~-------+----~

o~--~-~--~-----~---~ 10 20

Times of repetition

40

(times)

Fig. 9 Fracture stress and ultimate strain of nylon film exposed repeated temperature from -196°C to 200°C.

100

0- 0 0 <:5

50

10 20 40

Immersion time (days)

Fig 10 Joint efficiency of welded film immersed in liquid nitrogen.

influences described-above were exami­

ned by stu ding the orientation changes

obtained from the comparison of diffrac­

tion degree of X-ray diffraction photo­

graphs taken on the plain films, by

penetration method. In case of 6-nylon,

diffraction patterns of (200) (002) side are

observed relatively strong. X-ray test

conditions were as follows. Voltage: 55KV.,

Electric current: 10mA. Distance between

specimens: 28mm. irradiation time: 2hr. X-ray apparatus: SHIMAZU analysis

type X-ray apparatus GX-l. Fig. 9,Fig. 10 show the relations between strength of

each direction and elongation obtained from tension test on specimen. Photo. 1 shows

the X-ray photographs taken from Thru Edge and End side of specimen. Figs. 5-6

explain that on great differences were observed both in strength and in elongation

on the test of M. D., T. D. and a 45 degree angle direction. This clarifies that the

specimen is twice as strong as that of non-drawing. Diffraction pattern of Thru. in

photo. 1 is of ring shape and that of Edge is almost the same as that of End, which

is the (typical) characteristics of simultaneous two-axis drawing. Thus, the experi­

ments only on M. D. were to be done, and comparison of diffraction degree was to

be made using Edge X-ray diffraction photograph. Fig. 7 shows the result of prelim­

inary experiment on heat influence caused by welding. No remarkable changes were

observed in reference to strength and elongation, after 40sec. heating at 200°C, which

clarifies that the specimen still keeps the characteristic of simultaoeous two-axis

drawing film. Fig.8 shows the result of thermal fatigue, no low-temperature fatigues

(at -196°C-at+ 20°C) were observed but high-low temperature fatigues (at -196°C-....

at+200°C) were in existence and S-N curve was recorded in proportion to repeated

number. Comparing the fatigue of repeating number 10 (total heating time 150sec.)

and that of 200°C 160sec., it is observed that fracture stress is in existence around

each 11 kg/mm point. That is to say, high-low temprature fatigue is similar to simple

231

heating fatigue. Photo. 2 is the X- ray diffraction photograph of both simple heating

fatigue specimen and high- low temprature fatigue specimen (at - 196°C-at+ 200°C) ,

which deny the micro- influence. Fig. 10 examines the changes of joint strength by

Photo. 1 X-ra y d iffract ion patterns.

Heating time: 80sec. Heat ing time: 160sec . Times of r epet it ion: 40t im es .

Photo. 2 X-ray d iffraction patterns.

232

" 23O'e

Welding time

Fig. 11 Relation between welding condition and peel strength.

Welding pressure (kg/cm 2 )

°O~------~------~------~------~

Welding time (sec.)

Fig.13 Relation between welding condition and peel strength.

I I at

i I t--------------+---

~~=----~;J:~­,//--------r-- I-

'/~-'-" , " • " Welding time (sec.)

SOOf-- ~, r ~-O i---- - ----«>--- 10 -

o I ---<D-- 5

I ~' Weld~ng pressure (kg/em l )

Fig.15 Relation between welding conditions and peel strength.

Welding pressure

(kg/em2 }

---«)-- 10

----{])----

---.----0--

o~ ______ ~ ______ ~ ______ ~~ ____ ~

Fig. 12 Relation between welding condition and peel strength.

--<D-- I I

~ ~ , I

---e---"10 --0--- 10

I-----~···~~=-i~ I

I i I I ~

Fig.14 Relation between welding conditions and peel strength.

\\'elding pressure (kg/em l )

Fig. 16 Relation between welding conditions and peel strength.

dipping ultrasonic welding specimen in liquid nitrogen. Figs. 11---16 are the results of

peeling tests on specimen welded by type 1 heating plate. Specimens marked by ( • )

are ruptured in a welding boundary. From the experiments described above, follow­

ing conditions are proved to be required in getting sufficient welding. Welding

temperature: 250°C, heating time for welding: 5sec, Welding pressure: 10kg/cm2•

The order of conditions mentioned also indicates the order of importance in getting

sufficient welding. Photos. 3---5 are X-ray diffraction photograghs of peeling test

specimen. In reference to photo. 3 at 230°C, no remarkable changes of molecular

233

Welding pre ss ur e : 20kg/ em 2 , 5 kg / em2

, 20kg / em 2

Welding time: 5 see . , 15sec. , 15sec.

Welding te mperatur e : 230·C , 230·C, 230·C

P hoto . 3 X- r ay diffr act ion pattern s.

Welding pressure: lOkg / em2 , 2 kg / em 2

, 10kg/ em 2

We lding t ime: 2 see . , 5 see . , 5 see .

Welding temperature : 250·C, 250·C , 250·C

Ph oto. 4 X- r ay diffracti on patte rns.

Welding pres s ur e : lOkg/ em 2 , 2 kg / em 2

, lOkg / em2

Welding time: 2 sec . , 5 sec . , 5 sec.

We ldin g te mperature: 270·C, 270·C , 270·C

Ph oto . 5 X- ray diffra e ti on patterns .

234

orientation are observed, but in photo. 4, at 250°C, some are observed to keep

primary orientation while others being observed to proceed its change of orientation

according to the welding condition, and in photo. 5, at 270°C, most of molecular

orientations are dissolved except a few case of welding time being short (2sec) ,

welding pressure lOkg/ cm2, and in this 'case orientation tendency being observed.

Mierostructure under great peeling strength welding condition (250°C, 5se'c, lOkg/ cm2)

dissolves almost all molecular orientations and keeps a little original orientation

tendency. From those results, fine welding joint, making use of simultaneous two­

axis drawing nylon film, is considered to be possible. Further considerations being

made, comparing photos. 4 & 5 with others taken under the same welding condi­

tions except welding temperature, which brought forth the interesting facts stated as

follows X- ray diffraction photogragh got at 250°C for 2sec'. load of lOkg/ cm2 clearly

shows the primary molecular orientation while considerable dissolution can be

observed at 270°C under the same conditions. Photograph taken at 250°C for 5sec.

load of 2 kg! cm2 shows lowering tendancy of orientation, and total dissolution of

orientation can be observed at 270°C under the same conditions. Further more,

photograph obtaind at 250°C for 5sec-. load of lOkg/ cm2 slightly keeps the orientation

" ,. } llrl'j ~ 1m.' sec .

';el.! lng"rcssurp Ow cm 2

\

--«r -

Fig, 17 Relation between welding cond it ions and joint efficiency.

We lding press ure: 4 kg / cm2 ,

Welding time : 5 sec . ,

Welding temperature: 250·C,

Weld l nq pr essure (kq / cm l )

.~ _ lO

- - -{J)- - .

F ig. 18 Relat ion between welding conditions and joint efficiency.

4 kg / cm2

5 sec .

270·C

Photo . 6 X - ray diffra c ti on patte rn s.

235

but orientation cannot be observed by any means at 270°C. Figs. 17 & 18 show the

results of tension test on specimen welded by type 2 heating plate. Excellent welding

was obtained at 250°C welding temperature, for 5sec. welding time, 4 kg/cm2 welding pressure, which has proved 90% welding

jOint efficiency. In Comparison to the

results of peeling test, this excellency

seems to be explained by the difference

of shape of heating plate (the welding

conditions are same except welding

pressure). Photo. 6 is the X-ray diffraction

photograph of tension test specimen. Most

of the primary molecular orientations

are kept at 250°C while the disorder of

molecular orientation being observed at

270°C. This clarifies that the considerable

difference on weld microstructure is pro-

1400 1200 1000 800 650 Wave number (ern-I)

Fig. 20 IR diagram

A B

c D

E F

G

we ld ing time : 5 sec.

~ -~·250·C S 501--------!--____ ...... -<D-.... 270.C type 3 -

aa~----------~------______ ~ ____ ~ Welding pressure (k.g/emJ:)

Fig.19 Relation between joint efficiency and welding pressure applied by various types of heating plates.

Welding conditions

Heating Pressure Heating temp. (kg/ern" ) time

(.oC) (sec. )

270 10 5 2

250 10 5 2

230 20 15 5

BaSe material

236

duced only by 20°C temperature difference under the same ·conditions. What is more,

the disorder of molecular orientation is observed in X-rar diffra'ction photograph of

peeling spe'Cimen, while primary orientation is kept on tension test specimen, which

can be also considered due to the difference of shape. That is to say, type 1 is

considered to have a great heat accumulation effect and, therefore, to give a great

heat influence on specimen. Upon this, in order to make a sufficient welding on weld

parts with keeping the orientation to some extent, type 3 heating plate has been

contrived, making use of characteristics of both type 1 and type 2 and put into

experiments. Fig. 19 shows the experimental results of type 3, explaining that it

provides relatively stable welding of more than 80% welding joint efficiency. Fig. 20

is the result of heating influence of welding examined by IR. Changes of transmittance

can be pointed out at CONH of wave number 1030, 930 (cm- l ).

CONCLUSION

The folloWing summary can be made from the results of the present experiments.

Welding of simultaneous two-axis drawing nylon film can be possible without losing

its characteristic, by choosing the proper welding conditions.

ACKNOWLEDGMENTS

The authors would like to express sincere thanks to Yunichika Co. Ltd. for

preparing to base materials.

Part of this work was presented at the Meeting of the Textile Machinery Society

of Japan, Osaka, March 1971.

REFERENCES

1) Hiroshi KIMURA: Welding of Plastics (Nikkan Koogyo Press Co. Ltd), p.109 (1967)

2) Hiroshi KIMURA: Foundation for the Heating welding of Plastics (Sanpo Co. Ltd.) (1971)