Gardco PG-1 Panduan Pengguna - Halaman 9

Jelajahi secara online atau unduh pdf Panduan Pengguna untuk Peralatan Uji Gardco PG-1. Gardco PG-1 17 halaman. The pocket goniometer

The alternative methods for contact angle measurements described below may give contact

angle readings with increased precision depending on droplet shape. The following images

display the three typical droplet shapes:

A "flying saucer"?

Fig. 2.11 Droplet shape <90°

2.6.2 Contact Angles below 90 degrees

Figure 2.11 shows a droplet with a contact angle < 90 degrees. The

recommended way to measure the contact angle on a droplet shape

like this is to:

Rotate the protractor until centre line is at 90 degrees.

Locate the point of reflection on the droplet at the edge of the

contour (black circle in Figure 2.14).

Slide the specimen stage to the left until the point of reflection is

aligned with the centre line. PLEASE NOTE! It is important the

point of reflection to be positioned exactly at the centre line.

Rotate the protractor until the centre line is aligned with the

tangent at the point of reflection (Figure 2.15).

The centre line is now pointing at the contact angle for the

droplet. Take your reading on the scale avoiding parallax errors

(Section 2.5.1).

An "eight shape"?

Fig 2.12 Droplet shape >90°

Fig 2.13 Droplet shape is 90°

Fig 2.14 Point of reflection

Figure 2.15