1,720,973 research outputs found
Ant‐Nest Corrosion in Copper Pipes Triggered by Ethylene Vinyl Acetate‐Based Adhesive
Full text linkCorrosion of condenser circuits in refrigeration systems significantly impacts appliance reliability and longevity. This study investigates an unreported cause linked to changing adhesive materials during copper pipe assembly. Transitioning from a polyethylene‐based adhesive to one containing ethylene vinyl acetate caused unexpected perforation of copper coils within months. We hypothesized that even trace amounts of acetic acid, a byproduct of the latter adhesive, trigger a peculiar localized morphology known as “ant‐nest corrosion.” We propose using ethylene vinyl acetate‐free adhesives to prevent this issue in refrigeration systems
Failure investigation of a protective epoxy coating by means of crosscheck between infrared spectroscopy and thermal analysis
Full text linkThis paper reports the failure of an epoxy coating that was applied for corrosion prevention on the inner walls of a heat exchanger. The coating became brittle and detached from the walls of the exchanger after one year of service. An investigation was performed in order to evaluate the failure cause by means of thermal analysis, optical microscopy and infrared spectroscopy. Thermal analysis excluded an incomplete curing of the detached paint. Optical microscopy highlighted sediments, pores and cracks over the detached coating surface; infrared spectroscopy revealed vibrational bands associated with thermo-oxidative phenomena. A thermo-oxidative simulation was performed on fresh coating samples, pointing out that epoxy coating starts degrading around 100-120 °C. Taking into account the temporary malfunction of the cooling system reported by the user, the failure cause was identified in an overheating that induced a thermo-oxidative degradation of the coating and its subsequent embrittlement and detachment
Scleroglucan-Based Foam Incorporating Recycled Rigid Polyurethane Waste for Novel Insulation Material Production
Full text linkThis study details the synthesis and performance evaluation of a novel lightweight thermal and acoustic insulation material, resulting from the combination of a scleroglucan-based hydrogel and recycled rigid polyurethane waste powder. Through a sublimation-driven water-removal process, a porous three-dimensional network structure is formed, showcasing notable thermal and acoustic insulation properties. Experimental data are presented to highlight the material’s performance, including comparisons with commercially available mineral wool and polymeric foams. This material versatility is demonstrated through tunable mechanical, thermal and acoustic characteristics, achieved by strategically adjusting the concentration of the biopolymer and additives. This adaptability positions the material as a promising candidate for different insulation applications. Addressing environmental concerns related to rigid polyurethane waste disposal, the study contributes to the circular economy
The influence of consolidation and artificial weathering on all-PP composite behavior
No full textThe purpose of this work was to evaluate the effect of consolidation parameters on the mechanical properties of all-polypropylene composites. Consolidation time does not induce any significant influence, whereas processing temperature and in particular coextruded tape characteristics deeply affect laminate performance. The DSC analysis demonstrated that the proximity of copolymer and homopolymer melting points results in a reduction in the operating window. This suggests the implementation of a more effective temperature control during thermoforming to avoid reinforcement relaxation and localized melting. Artificial weathering was conducted under noon summer light condition to assess the effect of ultraviolet exposure on laminates. After 100 and 250 h, sample performance drops significantly, with overall strength and elongation reduction up to 70 and 88%, respectively. Low molecular weight by-products were identified using Raman spectroscopy on specimens surface, confirming the mechanical property decrement due to photo-oxidation process
The effect of artificial weathering on PP coextruded tape and laminate
Full text linkThe aim of this work was to analyse the influence of artificial weathering on polypropylene (PP) selfreinforced
composite both as fabric constituent (tape) and as laminate. Particular attention has been
focused on the interaction between radiation and material microstructural characteristics, especially
for the selective action that the former causes in PP amorphous regions. The evaluation of carbonyl index
performed by Fourier Transform Infrared (FT-IR) spectroscopy has highlighted that tapes are more prone
to degradation since their drawn structure induces internal stress. Differential scanning calorimetry
(DSC) measurements have denoted a shift towards lower temperature of PP melting peak. While crystallinity
determination performed by DSC and FT-IR spectroscopy has underlined an increasing trend
for laminate over exposure time due to the higher amount of amorphous phase, Raman spectroscopy
has revealed that photo-degradation induces a rise of the isomeric defect fraction, limiting chemicrystallisation
both for tapes and laminates
Impulse response method for defect detection in polymers: Description of the method and preliminary results
No full textThe major problem encountered in the application of polymer industrial products is the difficulty of effectively modelling and predicting material performance and service life according to applied loads and operating environmental conditions. Furthermore, the presence of defects such as voids or inclusions created during manufacturing may affect the final performance.
The aim of this study is to present and investigate the development of an innovative acoustic non-destructive technique (patent pending), able to verify defects into composite laminates.
The analysis was carried out in two steps: the first aims to verify if distinct phases can be recognized within a material, while the second has the purpose of testing the proposed method on defective materials ad hoc prepared
Time-depending performance of resilient layers under floating floors
No full textIn the floating floor system the performance of resilient layers, in terms of impact sound pressure level
reduction, is of paramount importance. In the present study in order to evaluate the time-depending performances,
a comprehensive characterization of twenty different layers was carried out, evaluating
dynamic stiffness, compressibility and compressive creep. The aim of this work was to find out a possible
correlation among these parameters and the effect of service time on mechanical and acoustical properties.
Results indicated that a general rule couldn’t be defined. Furthermore, the presence of a coating, as
well as different density and/or contact shape, has proved to influence the final acoustical performances
The morphological properties of PP coextruded tape fabrics
No full textIn the field of self-reinforced composites many researchers have focused their attention on the coextruded tapes composed of polypropylene core and PP/PE copolymer skin. Two similar commercial fabrics (P and T) have been compared in respect of their peel resistance. For both materials, peel resistance has a periodic trend that regularly follows fabric weave style. T has demonstrated an average peel resistance and a well-bonded area slightly greater than P. Skin/core interfacial properties have been investigated and a crosscheck between differential scanning calorimetry (DSC) and Raman spectroscopy has been adopted to understand the influence of skin structure on consolidated laminate. DSC curves exhibit three melting peaks during first heating for both fabrics, corresponding to copolymer, skin/core interface, and core melting. After consolidation at 140°C stretching-induced superstructure and PP crystallinity degree are preserved. The presence of PP/PE copolymer + PE blend only in fabric P has been pointed out and PE content has been calculated. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineer
Acoustic of lightweight timber buildings: A review
Full text linkThis paper presents a literature overview of the acoustic studies dedicated to lightweight wooden constructions. The reviewed articles contain prediction models, laboratory and field measurements, finite element or computational investigations as well as subjective survey describing the vibro-acoustic behaviour of a large range of wooden structures. The review analyses different type of timber constructions and investigates the acoustic research methodologies highlighting the following aspects: airborne sound insulation, impact noise reduction, flanking transmissions, human perceptions and pros and cons of the presented methods. Furthermore, an in-depth analysis of impact noise of bare floors focuses on how impact sound reduction could not be as efficient as in heavyweight constructions; the comparison between the different approaches on prediction of airborne sound insulation of multilayer timber partitions compared to traditional heavy building materials is shown. Finally a subjective method survey is provided, underlining the weakest point of timber buildings: low frequency sound insulation
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