Injection moulding is the most widely used technology for the manufacturing of plastic parts [
1]. The process is usually completely automated for the repeatable and reproducible production of parts that in general need no finishing. The first injection moulding machine was patented by the Hyatt brothers, John and Isaiah in 1872 [
2]. These first machines were quite primitive in comparison to contemporary systems. The technology was revitalized in the 1940s by the replacement of the plunger to inject the hot plastic in to the mould by an extrusion screw [
3]. The rotating screw gave the machine better control over the injection speed and consequently improved the quality of the plastic parts produced. The screw also allowed mixing of, for example, recycled materials with virgin materials due to the mixing action of the screw. The interaction of the screw with the solid pellet feed stock greatly contributes to the first stage process of melting or softening the plastic due to friction. The remaining heat comes from electrical band heaters. Screw machines now make up the vast majority of all injection moulding machines. Not long after the introduction of the screw extrusion injection mouding system, new high-quality thermoplastics including polyethylene, polypropylene, polystyrene and nylons became available [
4] and greatly helped the acceleration in the adoption of injection moulding of plastics as a manufacturing technology.
Injection moulding of plastics is a deceptively simple technology. Plastic feed stock usually in the form of mm sized pellets is heated in to the liquid state and then injected at high pressure in to a metallic mould to define the shape. The plastic cools and becomes solid after passing through a glass transition or crystallising to form a semi-crystalline solid. The solid part is then ejected from the mould. This work is focused on semi-crystalline polymers such as isotactic polypropylene, polyethylene, nylon and some biobased plastics such as polyhydroxybutyrate and polybutylene succinate. In these materials, the flow processes inherent to injection moulding and the rapid changes of temperature involved as the fluid plastics enters the mould have a profound impact on the structure and morphology which develops as the plastic solidifies and therefore on the properties of the part [
5]. Previous reports in the literature have focused on the post-processing characterisation of injection moulded parts and attempts have been made to reconstruct the history of the development of the structure and morphology during the injection moulding cycles [
6,
7]. There are a few exceptions to this, including experimental stages which approach industrial processing conditions. One of the earliest in-situ scattering studies was focused on Reaction Injection Moulding. This is a low-pressure process in which a reactive mixture is injected at low pressure in to a mould cavity. The low pressure used means that a variety of materials can be used to fabricate the mould. Elwell et al [
8,
9] used time-resolved small-angle X-ray scattering to study the microphase separation which takes place during the formation of the solid foam. Mateus et al [
10] used time-resolved scattering small-angle X-ray scattering to evaluate the microphase separation and showed that the rate of reaction of the components was slower that the time scale of forming the morphology. In Hamburg, Zachmanns group [
11] working on beamline A1 at HASYLAB were amongst the first to develop what can be seen as a realistic industrial manufacturing process, exploring fibre spinning. A more recent development involved polymer films which are blown using air pressure on extruded tubular films. This is a widely used process although it is a complex process with fast changing temperatures and different deformation geometries. Van Drongelen et al [
12] were probably the first to explore the film blowing process using time-resolving wide-angle X-ray scattering techniques. A limitation of this approach is that the preferred orientation of the chain folded-lamellar crystals is more difficult to evaluate using WAXS and later work included small-angle X-ray scattering measurements [
13]. Zhang et al [
14] mounted a film blowing system on a SAXS beamline [
15] to evaluate polyethylene films prepared in this manner, and used operando scattering to explore by adjusting the height of the extruder die with relationship to the incident beam. It was possible to evaluate different parts of the blown film at defined distances from the extruder die. The authors highlight how they were able to follow the network formation from the entangled melt through the formation of crystalline network points obtaining quantitative data which is able to inform on computational models of film blowing and the dependence of the process on the molecular parameters. Most other work reported more fell in to the realm of scientific studies but some recent work from Liao et al [
16] developed an operando X-ray scattering system for injection moulding using a metallic mould and diamonds as X-ray transparent windows. They used this system in conjunction with intense flux at the synchrotron beam-time BL19U2 [
13] at the Shanghai synchrotron radiation facility to determine the characteristics of the shish-kebab structures that are created during crystallization in he the micro-injection moulding. However, in the last year, a new major project at CDRSP has developed an industrially relevant injection moulding system which can be mounted on the NCD-SWEET beam at the ALBA Synchrotron light source to perform operando small-angle X-ray scattering measurements [
17]. X-ray scattering is a powerful tool for operando experiments. The bright sources of X-rays available via an undulator at a Synchrotron Light Source enable effective time-resolving measurements [
18]. The analysis of the data is largely unambiguous as the theory of X-ray diffraction physics is well understood and well developed and the optimum sample thickness of 1 - 2 mm is a practical industrial scale [
19]. Moreover, the samples need not be optically clear and can contain pigments and other nanofillers. Small-angle scattering which covers the important scale of ~10nm and provides critical information on the formation and the preferred orientation of chain folded lamellar crystals which are particularly important in determining the properties of the final part [
20].
The injection moulding system used in this work is designed and fabricated using industry standard materials and protocols, so that information gained in this work can be directly translated to industrial practice. The current work focuses on what can be achieved in terms of time and spatially resolved measurements using this new injection moulding system and the NCD-SWEET SAXS/WAXS beamline at the ALBA Synchrotron Light Source and the prospects for future developments and experimental work.