Moisture uptake of a polycarbonate blend exposed to hygrothermal aging

Synthesis and hygrothermal aging of polycarbonates containing a bisphenol fluorene moiety

This study aims to synthesize a specific type of polycarbonate with high refractive index, low birefringence, and resistance to hygrothermal aging by copolymerizing 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthyl (BNE) with 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF). Comparative analysis revealed that the copolymer synthesized from BNE and BPEF demonstrated superior hydrolytic stability relative to the bisphenol A-based polycarbonate. This augmented stability can be attributed to the monomers' higher pKa values, rendering acidic substances less capable of dissociating and thereby mitigating ester hydrolysis under hygrothermal conditions. Furthermore, the investigation probed into the phenomenon of physical aging in copolymerized polycarbonate when exposed to hygrothermal environments. It was discerned that the enthalpy loss, observable under both dry and hygrothermal conditions, could be linearly correlated with the difference between the aging temperature and the glass transition temperature (Tg), signifying a close correlation between the magnitude of physical aging and Tg. A lower Tg in the copolymerized polycarbonate led to more pronounced physical aging within the same timeframe, resulting in an augmentation of tensile strength and modulus, while higher Tg effectively mitigated the physical aging phenomenon.

The Influence of Moisture Absorption and Desorption by the ABS Filament on the Properties of Additively Manufactured Parts Using the Fused Deposition Modeling Method

This paper presents the results of research on the influence of the moisture content in a filament made of ABS polymer on the properties of products manufactured using FDM (fused deposition modeling). Tests were carried out on a standard printer, using the parameters recommended by the manufacturer and the literature on the subject. A special climatic chamber was used to condition the material. A negative impact of ABS filament moisture on the strength and dimensional accuracy of printed products and on the structure of their surface is demonstrated. When the range of the filament moisture is between 0.17% and 0.75%, the strength decreases by 25% and the sample thickness increases by 10%. It is also shown that this effect does not depend on the history of the polymer reaching a given moisture level, i.e., by absorbing moisture in the absorption process or releasing moisture in the desorption process.

Moisture Sorption and Degradation of Polymer Filaments Used in 3D Printing

Experimental research of the moisture sorption process of 12 typical filaments used for FFF was performed in atmospheres with a relative humidity from 16 to 97% at room temperature. Materials with high moisture sorption capacity were revealed. Fick's diffusion model was applied to all tested materials, and a set of sorption parameters was found. The solution of Fick's second equation for the two-dimensional cylinder was obtained in series form. Moisture sorption isotherms were obtained and classified. Moisture diffusivity dependence on relative humidity was evaluated. The diffusion coefficient was independent of the relative humidity of the atmosphere for six materials. It essentially decreased for four materials and grew for the other two. Swelling strain changed linearly with the moisture content of the materials and reached up to 0.5% for some of them. The degree of degradation of the elastic modulus and the strength of the filaments due to moisture absorption were estimated. All tested materials were classified as having a low (changes ca. 2-4% or less), moderate (5-9%), or high sensitivity to water (more than 10%) by their reduction in mechanical properties. This reduction in stiffness and strength with absorbed moisture should be considered for responsible applications.

The Natural Moisture of ABS Filament and Its Influence on the Quality of FFF Products

The article presents the results of research on the influence of the natural moisture of a filament made of acrylonitrile-butadiene-styrene terpolymer (ABS) on the mechanical properties and quality of products fabricated with fused filament fabrication (FFF). The concept of the natural moisture of the filament was defined, and the range of its variability was identified in reference to the range of the natural ambient humidity. It is shown that a change in the ambient humidity by 10% resulted in a change in filament moisture by about 0.05%. The results of the research on the moisture variability of an ABS filament stored in a package, an airtight container, or a container with a moisture absorber are also discussed. The last part of the article presents the results of the research on the impact of the moisture of the filament in its natural range of variability on select mechanical properties of filaments and products made using FFT. It is shown that this impact was significant and had a value of 1 MPa on 0.1% filament moisture.