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Resins used in surface coatings are mostly polymers of one sort or another and although they differ in a number of ways from the high polymers used to make plastics and synthetic fibres, they nevertheless show some of those properties peculiar to polymers. One of the things that distinguishes polymers from ‘ordinary’ organic compounds is the fact that instead of all the molecules having the same characteristic molecular weight, the molecules present have a variety of molecular weights (because they contain different numbers of monomer units). Instead of talking about a polymer's ‘molecular weight’ therefore, we have to talk about its average molecular weight and its molecular weight distribution.

Bellens has reported the study of several types of alkyd resin using a Waters Associates chromatograph equipped with a duplicate set of four columns covering a porosity range of 0.485 to 105 nm and eluted with THF at ambient temperature. Automatic sample injection was employed and, during a four‐hour fractionation process, the eluent from the sample set of columns was monitored by a differential refractometer using the other set as reference. The detector signal was fed to the Y‐axis of an X‐Y recorder, on which the X‐axis was used to display eluent volume information. A generalised GPC curve is presented in which the author identifies the zones attributable to solvent, non‐polymerised materials, oligomers and polymers and shows the pseudomaxima that arise from the four individual columns. Molecular sizes are quoted for fatty acids (15 Å), phthalic‐glycerol monoester (15 Å), diphthalate glycerol monoester (26 Å), monoglycerides (34 Å), phthalic monoester monoglyceride (37 Å), diglycerides (51 Å) and triglycerides (67 Å), whilst the GPC traces for most alkyds are shown to have a peak in their molecular size distributions between 75 and 120 Å.

APPLICATION of the so‐called high energy liquid fuels and high energy liquid oxidizers to power plants based on the jet propulsion principle is receiving the increasing interest and attention of rocket propellant chemists and power plant engineers universally. The aspect of substantially increased—as much as 50 per cent— energy per pound of propellant load or per cubic foot of propellant tankage over today's propellants has whetted scientific appetites and justified probing the field of high energy chemicals to determine, as logically and as practically as we can at the present time, the gains, problems, limitations and applications of these higher energy chemicals. The object of this paper is, in a general way, to discuss the subject of chemical rocket propellants in such a way that the following five questions will be, in part at least, answered or recalled to the minds of this audience for additional deliberation.

Laser sintering kinetics and part reliability are critically dependent on the melt viscosity of materials, including polyamide 12 (PA‐12). The purpose of this paper is to characterise the viscosity of PA‐12 powders using alternative scientific methods: constrained boundary flows (capillary rheometry) and rotational rheometry.

Various PA‐12 powders were selected and characterised by both techniques. Measurement of molecular weight was also carried out to interpret the viscosity data.

Results demonstrate conventional pseudoplastic flow in all PA‐12 materials. Zero‐shear viscosity has been quantified by rotational rheometry; a notable observation is the striking difference between virgin/used PA‐12. This is interpreted in terms of molecular weight and chain structure modifications, arising from polycondensation of PA‐12 held at the bed temperature during laser sintering.

Accurate zero‐shear viscosity data provide scope for use in predictive computational models for laser sintering processes. Careful sample preparation and equipment operation are critical prerequisites for accurate rheological characterisation of PA‐12 powders.

Differences in flow behaviour and molecular structure allow prediction and deeper understanding of process‐property relationships in laser sintering, giving potential for further optimisation of material specification and in‐process machine parameter control.

This is believed to be the first time that techniques other than melt flow rate (MFR) have been reported to measure the viscosity of PA‐12 in a laser sintering context, noting the effects of pre‐drying and molecular weight, then predicting differences between virgin/used powders in practical sintering behaviour.

Additive manufacturing (AM) methods such as material extrusion (ME) are becoming widely used by engineers, designers and hobbyists alike for a wide variety of applications. Successfully manufacturing objects using ME three-dimensional printers can often require numerous iterations to attain predictable performance because the exact mechanical behavior of parts fabricated via additive processes are difficult to predict. One of that factors that contributes to this difficulty is the wide variety of ME feed stock materials currently available in the marketplace. These build materials are often sold based on their base polymer material such as acrylonitrile butadiene styrene or polylactic acid (PLA), but are produced by numerous different commercial suppliers in a wide variety of colors using typically undisclosed additive feed stocks and base polymer formulations. This paper aims to present the results from an experimental study concerned with quantifying how these sources of polymer variability can affect the mechanical behavior of three-dimensional printed objects. Specifically, the set of experiments conducted in this study focused on following: several different colors of PLA filament from a single commercial supplier to explore the effect of color additives and three filaments of the same color but produced by three different suppliers to account for potential variations in polymer formulation.

A set of five common mechanical and material characterization tests were performed on 11 commercially available PLA filaments in an effort to gain insight into the variations in mechanical response that stem from variances in filament manufacturer, feed stock polymer, additives and processing. Three black PLA filaments were purchased from three different commercial suppliers to consider the variations introduced by use of different feed stock polymers and filament processing by different manufacturers. An additional eight PLA filaments in varying colors were purchased from one of the three suppliers to focus on how color additives lead to property variations. Some tests were performed on unprocessed filament samples, while others were performed on objects three-dimensional printed from the various filaments. This study looked specifically at four mechanical properties (Young’s modulus, storage modulus, yield strength and toughness) as a function of numerous material properties (e.g. additive loading, molecular weight, molecular weight dispersity, enthalpy of melting and crystallinity).

For the 11 filaments tested the following mean values and standard deviations were observed for the material properties considered: p_a = 1.3 ± 0.9% (percent additives), M_w = 98.6 ± 16.4 kDa (molecular weight), Ð = 1.33 ± 0.1 (molecular weight dispersity), H_m = 37.4 ± 7.2 J/g (enthalpy of melting) and = 19.6 ± 2.1% (crystallinity). The corresponding mean values and standard deviations for the resulting mechanical behaviors were: E = 2,790 ± 145 MPa (Young’s modulus), E’ = 1,050 ± 125 MPa (storage modulus), S_y = 49.6 ± 4.93 MPa (yield strength) and U_t = 1.87 ± 0.354 MJ/m^³ (toughness). These variations were observed in filaments that were all manufactured from the same base polymer (e.g. PLA) and are only different in terms of the additives used by the manufacturers to produce different colors or different three-dimensional printing performance. Unfortunately, while the observed variations were significant, no definitive strong correlations were found between these observed variations in the mechanical behavior of the filaments studied and the considered material properties.

These variations in mechanical behavior and material properties could not be ascribed to any specific factor, but rather show that the mechanical of three-dimensional printed parts are potentially affected by variations in base polymer properties, additive usage and filament processing choices in complex ways that can be difficult to predict.

These results emphasize the need to take processing and thereby even filament color, into account when using ME printers, they emphasize the need for designers to use AM with caution when the mechanical behavior of a printed part is critical and they highlight the need for continued research in this important area. While all filaments used were marked as PLA, the feedstock materials, additives and processing conditions created significant differences in the mechanical behavior of the printed objects evaluated, but these differences could not be accurately and reliably predicted as function of the observed material properties that were the focus of this study.

The testing methods used in the study can be used by engineers and creators alike to better analyze the material properties of their filament printed objects, to increase success in print and mechanical design. Furthermore, the results clearly show that as AM continues to evolve and grow as a manufacturing method, standardization of feedstock processing conditions and additives would enable more reliable and repeatable printed objects and would better assist designers in effectively implementing AM methods.

Gel permeation chromatography is an analytical technique that separates molecules according to their size. The size of a molecule in solution depends upon its molecular weight and stereochemistry. Therefore, for solutions of highly‐polymerised materials of regular structure, the sizes are a direct indication of molecular weight. For solutions of low‐molecular‐weight species on the other hand, the size of the molecule will vary considerably to its chemical constituents and may also be affected by polar interactions with the solvent or between the individual molecules themselves.

The purpose of the present study is first to develop a hydroxyl-functionalized ketonic resin for coating applications and to establish a standard characterization protocol; second, to quantify the effects of various operating parameters on resin properties and to develop mathematical models to predict the product properties; and third, to carry out the compatibility study between the in-house developed resins and commercially available resins.

Self-polymerization reactions were conducted in a batch reactor. Effects of reaction time, temperature, catalyst concentration and reactor pressure on product properties have been studied. Hydroxyl value, iodine value, solubility, rheology, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and the X-ray diffraction (XRD) analysis were carried out to characterize the product properties. Mark–Houwink correlation was used to predict molecular weight of the resins.

The study shows that hydroxyl value and softening temperature (ST) of the product increased with the increase of reaction temperature, duration of reaction and alkali concentration. However, the solubility value of the resins decreased with the increase of temperature, time and alkali concentration. Regression models were developed to predict the optimum conditions for obtaining a desired quality of resin. The number-average molecular weight of the developed resins was in the range of 450-1150. The products are thermally stable up to around 200°C, and adequately soluble in many commercial solvents.

The ketonic resin can be used as a substitute of phenolic resins which are prepared from more hazardous materials monomers such as phenolic and aldehyde compounds.

The resin can be used as a substitute of more hazardous materials such as phenolic and aldehyde compounds.

This paper details the synthesis of ketonic resin from cyclohexanone and its compatibility. It also investigates the optimization of operating parameters to obtain a desire product.

This paper aims to establish an appropriate annealing method, which is necessary for shape stability and to evaluate their potential degradation performance of 1-, 3- and 5-layer material extruded polylactic-acid specimens by enhancing their thermal and mechanical properties.

The distortion of each layered printed specimen subjected to degradation was calculated in x- and y-direction. Each layered specimen was subjected to annealing at 70°C, 80°C and 90°C for 2 h and at 80°C for 1, 4, 8 and 16 h. Thermal, molecular weight and mechanical properties were calculated using, differential scanning calorimetry, gel permeation chromatography and tensile testing machine, respectively.

In the x-direction, distortion was 16.08 mm for one-layer non-annealed printed specimens and decreased by 73% and 83% for 3- and 5-layer, respectively, while each layered non-annealed specimen subjected to degradation at 37°C for one month. Within the outlined study, annealing treatment enhances properties such as the degree of crystallinity (%χ) up to 34%, Young’s modulus (E) by 30% and ultimate tensile strength by 20% compared to the non-annealed specimens.

The future research accomplishments will be concentrated on the design, development and optimisation of degraded biomedical implants using material extrusion thin films including drug delivery system and fixation plates.

The printed thin specimens subjected to degradation were investigated. This research developed a new understanding of the effect of the annealing temperature and time on the mechanical, thermal and molecular weight properties for each layered specimen.

The purpose of this paper is to develop hybrid copolymers through the copolymerisation of a novel low molecular weight oleic acid‐based macromer with methyl methacrylate (MMA), with the aim of combining the good properties of alkyd and acrylic binders.

The macromer was synthesised from phthalic anhydride, oleic acid and glycerol. It was copolymerised with MMA using a free radical initiator. The ratio of the macromer and MMA was varied and the glass transition temperature, molecular weight, thermal stability, and film properties of the copolymers were characterised.

Under similar conditions of temperature and reaction time, the lower macromer to MMA ratio has led to faster polymerisation rate, higher molecular weight and higher T_g of the copolymer. Generally, all the coatings showed excellent adhesion properties, while the coatings with the higher content of MMA exhibited better alkali and water resistance.

The macromer used in the present context was synthesised from oleic acid and glycerol supplied by a local palm oil oleochemicals manufacturer. Presumably the same raw materials from other vegetable oils could also be used. In addition, the macromer structure could be changed by varying the formulation so that it would have different molecular weight and functionality.

The method has managed to combine the properties of alkyd and acrylic, resulting in coatings that exhibit good mechanical and chemical properties, fast physical drying as well as excellent adhesion.

Oleic acid and glycerol are palm oil derivatives which are from natural resources and are sustainable raw materials. Although the macromer by itself cannot air‐dry due low iodine value, this could be overcome through copolymerisation with methyl methacrylate to find numerous applications in surface coating.

(b) Linear Homopolymers Linear poly(vinyl acetate) and polybutadiene samples were studied by Park and Graessley using GPC combined with capillary viscometry which provided both the distribution of hydrodynamic volumes and intrinsic viscosities of the samples. Their equipment comprised a Waters Associates Chromatograph (model 200) fitted with five Styragel columns of porosities 106, 105, 1.5 × 104, 104 and 3 and 103 mm eluted with THF at room temperature at a flow rate of 1 cm3 min−1. Samples of 2 cm3 nominal volume were injected at a concentration of 0.25 g per 100 cm3 and detection was by a differential refractometer coupled to a digital curve translator so that readings were digitised and fed to a teletype machine at one minute intervals. From the refractometer, the sample passed via a syphon device into an all glass viscometer of the Ubbelohde type and the whole of this equipment was totally immersed in a water bath whose volume was sufficient to smooth out minor temperature variations in the equipment. The viscometer discharge was detected photoelectrically and the time taken determined by an electronic timer which gave a signal that was also recorded on the teletype.