Influence of water absorption on the mechanical properties of Polyamide 6 and Polyamide 4-6

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Influence of water absorption on the mechanical properties of

Polyamide 6 and Polyamide 4-6

Citation for published version (APA):

Hrachová, J., Govaert, L. E., & Meijer, H. E. H. (2010). Influence of water absorption on the mechanical properties of Polyamide 6 and Polyamide 4-6. Poster session presented at Mate Poster Award 2010 : 15th Annual Poster Contest.

Document status and date: Published: 01/01/2010 Document Version:

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Introduction

Influence of water absorption

on the mechanical properties

of Polyamide 6 and Polyamide 4-6

Polymer Technology

/ Department of Mechanical Engineering

Nylon is a generic name for a family of long-chain

polyamide engineering thermoplastics. The nylon family

members have recurring amide groups

[–CO–NH–]

as an

integral part of the main polymer chain and are named by

the number of carbon atoms in the monomers. Because of

the formation of hydrogen bonds between chains in

nylon crystals, nylons generally have higher melting

points than many other semi-crystalline polymers, high

affinity for water, and their physical and mechanical

properties are often significantly affected by the

absorption of moisture.

n

O

C

CH

₂

CH

₂

CH

₂

CH

₂

CH

₂

H

N

n

O

C

CH

₂

CH

₂

CH

₂

CH

₂

C

H

N

CH

₂

CH

₂

CH

₂

CH

₂

H

N

Polyamide 6 (Nylon 6)

Akulon F 223-D

Polyamide 4-6

(Nylon 4-6)

Stanyl TW 300

Vacuum oven

dry samples

Climate chamber

70 °C

, 62 % RH

2 weeks

_{Dist. H}

2 O

Lab. temp.,

100 % RH

Equilibrium

Dist. H

₂

O

NaBr

Silica-gel

100 % RH

~ 58 % RH

~ 17 % RH

PA 6

PA 4-6

Materials and conditioning

Results

Jana Hrachová, Leon E. Govaert, Han E. H. Meijer

The equilibrium water absorption depends on the relative

humidity (RH) of the surroundings and on the temperature

(Fig. 1).

The absorbed water in polyamides gives rise to the

presence of a lower endothermic peak at around 100 °C

on DSC curves (Fig. 2). Difference in the size and area of

water endothermic peaks are observed in dependence on

water content.

The existence of two distinct yield points in

semi-crystalline polymer is attributed to the deformation of the

amorphous phase for the first yield point and the

deformation of the crystalline phase for the second yield

point. At higher moisture level the double yielding

disappears displaying only a very broad yield, similar to

rubber-like deformation (Fig. 3).

Fig. 1 Water absorption of PA 6 and PA 4-6 as a function of time.

Fig. 2 DSC curves of PA 6 and PA 4-6 scanned at 10 °C/min in nitrogen atmosphere.

Fig. 3 Stress-strain curves of PA 6 and PA 4-6 at different humidity conditions and strain