The sensitizing effect of acrylates on radiation vulcanization of natural rubber latex

Phys. Chem. Vol. in Great Britain

Radiat. Printed

42, Nos

1-3,

pp.

121-124,

0146-5724/93

1993

THJ3sRNs~G

pew, I’di,

tan&~

chen&

Son6and

Hu, Pumin6

the Minis&y of Chemical Industry

Sichuan 610041 P.R. China

effect of acrylates on radiation vulcanization

indicate that ac value of crossllnking

of natural rubber latex was studied.

However,

depending

The noulb,

(Gc) will be higher ht the same radiation dose when a sensitizer etits,

and Oc value decreasea with the incriase of radiation dotie (D) conforming K and a are constants

Ltd

OF NATURAL. RURRRR LATJtX

Chen6du Silicone Research Centre, Chengdu,

+ 0.00

Press

ON RADIATION

EFFEXT OF ACRYLA~

VULCANIZA~ON

The

$6.00

Pergamon

on sensitizers.

The more aensitize~

to the formula Gc=KD’, added,

the viscosity of the natural rubber latex also increasea rapidly alon

the greater

whets

the Gc value.

with the increase of sensitizers

added.

Some sensitizens,

such as TMPTA, can decrease the optimum dose from about 200 kGy to approximately

kGy ac~~rding to our experiment. properties are comparable

The tensile -116th

of the film can reach round 20 MPa.

20

Other physical

to those of unsensitized.

Keywomb

Natural

rubber

latex,

Radiation

vulcanization,

Sensitizer,

Acrylate, ctra&&q

density,

0 value of

croWlinking.

Illtroductlon Much attention haa been paid to the radiation vulcanizlltion purity and low toxicity of its ptoducfzi. The aensitiz~ to enhance (Cheoguang,

efficiency

of RVNRL.

SC.ol. 1976, Minoura,

of natural rubber latex (RVNRL)

effect on RVNRL haa been widely invest&ation

Cabon tetrachloride

is amon

the aensitiznrs

invest&ation

in order

that were first developed

St. a6. 19611, but its USYis limited becauw of ibr toxicity.

sensitizers of another categorv which have been proved out to be efficient(Mnkuuchi, reporta a systematic

because of hi&

Acrylata

on sensitizing effect of acrylatee in RVNRL.

Rxperlment8

Centrifugally

concentrated

latex obudned from China was dih~ted to 50% with 1% of aqu0ou.sammonie 121

are

et.d. 1988). This paper

122

et al.

PENG PEILI

Tab. 1 Crosslinking parameters of acrylate-sensitized Sensitizer

1,6-HD

10. 9

1. 21

10. 6

1. 12

A-NPG

33. 5

3. 42

9. 1

0. 93

TRIEGDA

a. 9

0. 90

n-BA

10. 1

1. 03

TMPTA

22. 0

2. 30

HEMA

14. 0

1. 48

TMPTMA

24. 4

2. 50

9. 9

1. 02

None

a. a

0. 90

la. 1

1. 80

(Contrast)

DMAEMA EDA

before mixed with acrylates.

Some of the acrylates

others were synthesized at our laboratory. (MA ) , n -

Hexanediol (TRIEGDA)

Cc

Y(10”)

1. 26

n-BMA

methacrylate

Sensitizer

11.9 MA

acrylate

Cc

Y(1018)

RVNRL

Butyl

(HEMA), diacrylate

Acrytales

methacrylate

(n -

Dimethylaminoethyl ( 1,6 - HD)

, Trimethylolpropane

and other reagents were commercially in experiments:

BMA > , n -

methacrylate

available,

Methyl methacrylate

Butyl

(DMAEM)

acryiate

(n -

(MMA)

BA 1,

and the

, Methyl

Hydroxyethyl

, Etheyl diacrylate (EDA),

1, 6 -

, Neopentyl glycol diacrylate (A - NPG ) , Triethylene - glycol dicryiate Triacrylate

(TMPTA)

, Trimethylolpropane

Irradiation process was carried out at room temperature with Co-

trimethacrylate

(TMPTMA).

60 y ray or electronbeam.

properties

Physical properties were determined according to Chinese National Standards.

Crosslinking parameters were calculated based on swelling rate in benzene.

Results and diacdon

Various acrylates were individually added to the latex up to 5 phr. After hmdiation to a dose of 80 kGy, crosslinkmg

density (y)

and G value of crosslinking

(Cc)

shown in Tab. 1. Tab. 1 indicates that most of the acrylates among all acrylates investigated multifunctional A-NPG

and DMAEMA

the viscosity dramatically the latex’s

The results are

have certain sensitizing effect on RVNRL,

acrylates are the most efficient sensitizers.

etc. are of little significance because they decrease the latex’s or even making the latex coagulated.

TMPTA

and TMPTMA

however,

and

HEMA,

stability by enhancing have better effect on

stability while maintaining high sensitizing efficiency.

Our tests have proved out that Cc of sensitized RVNRL 1.

were calculated by swelling rate.

the

is a function of radiation dcee (D) ,as shown in Fig.

Fig. 1 indicates that Cc decreases with increase of D , and they have a linear relation on log - log plot,

conforming

to the formula Gc=KD-“,

It is generally

where K and a are constanta varried with sensitizers.

agreed that the sensitizing efficiency

rubber molecules and their radiation sensibility.

of acrylates

is determined by their compatibility

Generally speaking,

with

acrylates containing methyl groups are

8th International

o.st +-None,-

on Radiation

Processing

0

l

I

does In

Qc

123

1

3

Content

doBe D(kGy)

kdialioa

m effectof mdtatton

Fk.1

Meeting

Bensitizer.

Flg.2

4

6

5

of TYPTAtphr)

The.&ectdtit&ormtentonQc.

-II-BA,-+-HD

Radiation done, 2okQy

--o--CCL,-X-TMPTA

more hydrophobic

than those without methyl groups and thus have better compatibility

Radiation sensibility of acrylates is more complicated and needs further research. acrylates,

with rubber molecules.

As for the multifunctional

we can postulate that they are grafted on main chains of rubber first,

and then intermolecular

through double bones remained on the branched chains is introduced.

Because they posse&s more

crosslinking

reactive centrm (double bones),

they should be more efficient in sensitizing crosslinking than monofunctional

acrylates.

It is very obvious that the more acrylates added the greater enhancement

of Gc. Gc value of the latex with

TMPTA increases linearly with increase of amount of TMFTA added in the range of I-5phr to a dose of 20 kGy. This is shown in Fig. 2. However, Our tests indicates higher,

that viscosities

of most samples of NRL containing

and the more the acrylate

enhancement choosing

the acrylate

the enhancement

of viscosity with the amount of TMF’Th4A as an example

sensitizers,

efficiency.

added the greater

the effect on the latex’s

stability

after irradiation

it does not mean that the more acrylatt% the better. sensitizer

of viscosity. (irradiation

must be considered

dose 20 kGy).

optimum vulcanization demonstrated

after a sensitizer

of appropriate

physical properties

Because the

dose naturally will be lower than that required by RVNRL with no sensitizers,

RVNRL with 1 phr TMPTA,

So in

content is added to the NRL,

in Fig. 4. From fig. 4 we can see that the optimum vulcanization

The tensile strength

the

as well as on their sensitizing

The effects on toxicity and physical properties of the films are also important factors.

Gc value of RVNRL will be enhanced

will become

Fig. 3 shows

the

which is

dose is about 20 kGy for

which is smaller roughly by an order of magnitued than that with no sensitizers.

at the optimum

dosage is about 20 MPa and the elongation

of sensitized NRL of radiation

vulcanization

is about 1000%.

Other

are also very close to those of unsensitized

NRL of radiation vulcanization.

We also compared the RVNRL cured by electron beam irradiation with that by y-ray Irradiation

was carried out by electron

properties

of the latex and fihns

vulcanization

was approximately

utilized to RVNRL effectively. but requires well-designed

beam,

the Cc was influenced

were similar the same.

by some processing by y - ray,

This means that both accelerators

By comparision,

processing,

to those irradiated

irradiation.

When the

parameters.

The

and the mechanism

of

and y - ray sourcea can be

it is found that electron beam radiation has higher efficiency

while y-ray

radiation needs longer time but is IVESlimited by the

PENG PEILI et al.

124

1

1

3

4

6

Content of TMPTMA (pbr)

10

SO

20

100

300

Radiation

F&.4

600

1000

done My)

Thsefkstdmdiathdaea&¶kd papatiadRVNRL-X-WIthMsitiza mPTA(lphr)

,-o-without

mendthE

containers and processing.

Moat of the acrylates multifunctional

have certain sensitizing effect on radiation vulcanization

of natural rubber latex.

The

onea have h&her sensitizing effect among these acrylates.

The latex film’s

Gc value of radiation

radiation dose. And it conformed

The optimum radiation

vulcanization

with acrylatea decrensea along with the increasea of

to the formula of C+c==KD” in the range of 10 to 100 kOy.

dose of the natural

rubber latex containing

TMPTA( lphr)

is about 20 kOy,

and

physical properties of the film are the same as unsensitized

on the whole.

Chenguang and Jinexiang

of natural rubber latex. In t Radiation Chemistry,

(1976).

Radiation vulcanization

(Editor by Symposium Group) ,PP. 120Makuuchi,K.

and Tausima,

K. , (1988).

Society Rubber Industry Japan. -61,471Makuuchi,

K. and Tsushima, K. , (1988)

143. Atomic Eneygy Press,

Radiation vulcanization

Beijine(Chinese>.

of natural lubber latex with diacrylates. J. -

477

RVNRL mith monofunction

acrylic monomer. J. Society Rubber

Industry Japan,61,478-482. Minoura. Y. and Asao. M. , (1961)

Studies on the y-radiation

of natural rubber latex. J. Appl. Polymer Sci. ,

5,233-239. Minoura,Y.

and Asao,M.

, (1961)

Srudia, on the y-radiation

halogen compounds on cross-ltiing

by y-radiation.

of natural rubber latex.

The effect of organic

J. Appl. Polymer Sci. ,S, 401-

407.