Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

Abstract

The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.magnified image

Stabiliser diffusion in long-term pressure tested polypropylene pipes analysed by IR microscopy

“…11 shows a distinct local minimum of the stabiliser concentration in the centre of the pipe wall (x ¼ 5 mm). This is caused by the morphology of the pipe wall which results from the extrusion process and has been extensively described previously [9].…”

“…All measurements were carried out in transmission mode. The details of sample preparation have been described in our previous paper [9]. The stabilisers Irganox 1010, Irganox 1330 and degradation products of polypropylene were quantified according to the parameters listed in Table 3.…”

“…We have previously shown [9] that infrared (IR) microscopy offers a possibility to investigate the distribution of the phenolic antioxidant Irganox 1010 across the walls of unaged PP-R pipes. However, despite its widespread use in qualitative analysis only a few examples of quantitative IR microscopy exist [10][11][12].…”

“…x: real argument; m: integer; G(z): gamma function n ¼ À Dd=d Dl=l (9) n: Poisson's ratio; d: thickness; l: length; Dd ¼ d À d 0 3ðs; TÞ ¼ s EðTÞ þ aðTÞ,DT (10) 3: strain; s: hoop stress; T: temperature of water bath; DT ¼ T À T 0 , T 0 ¼ 0 C; E(T): Young's modulus; a(T): thermal expansion coefficient; E(T) and a(T) were taken from [33] y ¼ À0:374 þ 0:125e 109:3x (11) …”

Monitoring the effect of chlorine on the ageing of polypropylene pipes by infrared microscopy

“…IR microscopy (mFT-IR) which combines the optical information available from light microscopy with the chemical information from IR-spectroscopy has found entrance into material science in the early 1980s [13]. The high spatial resolution and reproducibility of results make mFT-IR an attractive analytical technique to study the effect of inner media on polyolefin pipes, and its scope in compiling information such as the distribution of additives or spectral crystallinity across the wall of PP pipes with high spatial resolution has been demonstrated recently [14].…”