High-pressure Laminates Research Articles

Retraction of "Assessing the Weathering Performance and Functionality of Nanoparticle-Enhanced High-Pressure Laminates for Building Facade Applications".

[This retracts the article DOI: 10.1021/acsomega.3c08443.].

Assessing the Weathering Performance and Functionality of Nanoparticle-Enhanced High-Pressure Laminates for Building Facade Applications.

High-pressure laminates (HPLs) are widely utilized in interior applications but may have potential as exterior building facade coatings if suitably enhanced for weatherability. Nanoparticle additives are a promising approach to improving the durability and functionality of HPLs. This study aims to evaluate titanium dioxide (TiO2) and silicon dioxide (SiO2) nanoparticles incorporated into HPLs to determine if they impart properties for durable, functional exterior facades. Methods: HPLs were fabricated with 3.75 wt % TiO2 and SiO2 nanoparticles in the surface overlay. Industry-standard EN 438 tests characterized the quality, optical properties, and accelerated aging, including UV radiation, weathering, and thermal shocks. Properties were measured before and after aging to compare versus a standard HPL without nanoparticles. Nanoparticles not only increased initial solar reflectance but also caused color changes. After aging tests, nanoparticles did not sufficiently enhance durability compared to the standard HPL. While initial reflectance improved with nanoparticles, overall weatherability did not, indicating a need to optimize fabrication and nanoparticle selection. Although TiO2 and SiO2 nanoparticles increased initial HPL reflectance, the feasibility of durable facade coatings was not conclusively demonstrated. Further research should focus on ideal fabrication methods, nanoparticle types and concentrations, and performance in real-world conditions to facilitate adoption in building facade applications.

The Effect of Borax Addition as Buffering Agent on Storage Stability of Melamine-Formaldehyde Resin in the Production of High-Pressure Laminates

High-pressure laminates (HPL) is one of the applications of thermosetting resins for wood-based materials as protective and decorative panels covering building furniture. Melamine-formaldehyde (MF) resin is one of the resins that play a role in the production of high-pressure laminates. This resin has low storage stability due to cross-linking between free melamine methylols accompanied by a decrease in pH during the storage process. This study aims to improve the storage stability of melamine-formaldehyde resin by adding borax as a buffering agent. Synthesis of MF resin was conducted by polymerization and condensation steps followed by the addition of borax at concentrations of 0, 0.5, 1, 1.5, and 2% when the endpoint was reached. The characterization of the resin includes the analysis of the physical and chemical parameters of the resin and the analysis of the functional groups of the resin by FT-IR. Storage stability study of MF resin was carried out by daily visual observation and determination of daily changes in pH and viscosity. MF resin was further used in the production of high-pressure laminates. High-pressure laminates characterization includes quality analysis based on SNIISO4586-7:2017 and analysis gloss level. In this study, 1.5% MF borax resin had the highest storage stability, namely 11 days. HPL quality analysis complies with SNIISO4586-7:2017 standards. High-pressure laminates of 1.5% borax MF resin has the highest gloss level, which is 115.

Microscale failure analysis of the ultra-high-performance polypropylene fibre reinforced concrete panel subjected to high thermal loading induced by fire exposure

To date, many buildings are prone to fire from non-structure systems like high-pressure laminates and insulated cladding systems. Ultra-high-performance concrete (UHPC) has been applied to the cladding systems due to its excellent mechanical properties at room temperature and non-flammable characteristic. To improve its mechanical properties under fire condition, different fibres like PP fibre have been employed to reinforce UHPC. The tensile strengths of these ultra-high-performance PP fibre reinforced concrete (UHPPFRC) panels vary due to the different orientations of internal PP fibres. However, few studies have been carried out on the internal stress and fire resistance of these claddings. Study on understanding the fire behaviours and failure process of the UHPPFRC panel is essential for developing claddings with better fire resistance and durability. In this study, a coupled hygro-thermal–mechanical model is developed to predict the internal stress and temperature distribution within the UHPPFRC panel. The microscopic failure process of PP fibre and porosity change within the panel during heating are all embodied in the model, and its accuracy has been validated. The initial and the residual tensile strengths of the UHPPFRC panel are considered to fluctuate between two extrema due to the random fiber orientation. Based on this, Program Evaluation and Review Technique (PERT) is applied to investigate the effects of fibre dosage and heating rate on retarding crack propagation and failure of the UHPPFRC panel under high temperature. Results from the numerical investigation indicate that 0.55% dosage of PP fibre can effectively postpone crack occurrence and propagation within the UHPPFRC panel at linear elastic phase, and faster heating rate can accelerate the pore pressure generation process. Also, internal fibre orientation is a significant factor affecting the fire endurance of the UHPPFRC panel subjected to elevated temperature, which should be considered for safety and reliability evaluation of the structure.

Paper-Based Laminates Impregnated with a Hybrid Lignin-Phenol-Formaldehyde Resin

In this study, high-pressure laminates (HPL) impregnated with phenol-formaldehyde (PF) resins enriched with kraft lignin were developed. Pulverised kraft lignin was added to the commercial PF resin in the amounts of 1% and 5% (solid to solid). Laminates were manufactured using pressure impregnation of the resins into the papers and using hot pressing of HPL in a laboratory press. Laminates with a lignin content of 1% (L-LPF-1) showed the highest bending strength (72.42 MPa) and Brinell hardness (9.41); they also exhibited the best moisture uptake (9.61) and thickness swelling after immersion in water (3.32%). Except for impact bending, laminates with a lignin content of 5% (L-LPF-5) had worse properties. However, the differences between the variants are mostly not statistically significant and are comparable with the results of commercial PF resin. Scanning electron microscopy confirmed the homogenous structure of produced laminates and the occurrence of cohesive failures in ruptured L-LPF-1 laminates, whereas in ruptured L-LPF-5 laminates adhesive failures were also observed. Based on the conducted research it can be said that the utilisation of kraft lignin as an additive to PF resin (in the amount of 1%) has a positive effect on the produced HPL.

Studies on RPC detectors operated with environmentally friendly gas mixtures in LHC-like conditions

Resistive Plate Chambers (RPC) are largely employed at CERN LHC experiments thanks to their excellent trigger and timing performances. High Pressure Laminates (HPL) RPCs are operated with a gas mixture made of about 95% of C2H2F4, 5% of i-C4H10 and 0.3% of SF6. Both C2H2F4 and SF6 are known to be Greenhouse Gases (GHG), with a global warming potential of 1430 and 22800 respectively. Due to leaks at the detector level, RPCs accounted for about 87% of total GHG emissions from particle detectors at CERN during LHC Run 2. CERN has elaborated several strategies to reduce its GHG emissions and align with the European regulation on fluorinated gases. One strategy consists in the study of alternatives gases for particle detectors, with a particular focus on alternatives to R-134a and SF6. An experimental setup was designed to study RPC performances with eco-friendly gas mixture first with cosmic muons, where several gas mixtures could be tested. Few gas mixtures were then selected and a dedicated setup was installed at the Gamma Irradiation Facility of CERN to characterize detector performance with LHC-like background radiation and muon beam. Results with RPCs operated with lower GWP gas mixtures are presented in this work.

Studies of the Cracking Behaviour of High-Pressure Laminates

The European standard EN 438-2 (2019) describes a method to assess the resistance to cracking of high-pressure laminate (HPL). In the EN 438-2 setup, the samples’ shrinkage at a temperature of 50 °C for 6 h is restrained by a metal clamp. The resulting tensile stress may lead to the cracking of the laminate. With the intention to gain additional insight into the parameters and influencing factors of the standard test, the resistance to cracking of 43 laminates was tested in accordance with the standard and with a prolonged testing time. Additionally, the tensile strength and shrinkage of the laminates were determined under the conditions of the standard test. The standard test uses free laminates (laminates not glued to a carrier board), so in order to correlate the results to applications that are close to real-life situations, four of the laminates were also tested when glued to carrier boards the size of furniture doors. In this full factorial test, particle board and gypsum board were used as carrier boards, UF and PVAc as adhesives, and the possible shrinkage of the laminates was adjusted by two moisture conditions of the laminates. The resistance to cracking in the standard test turned out to be mainly influenced by the composition of the laminate. Thin laminates with a pure paper backing were especially prone to cracking in the setup. Within the 6 h storage at 50 °C of the standard test, the laminates did not reach moisture equilibrium. Prolonged storage at 50 °C until equilibrium was reached (which took up to 10 days) allowed an improved differentiation of the cracking resistance, especially of thicker laminates. Four of the laminates were also tested on wooden and mineral-based carrier boards with either PVAc or UF as adhesive and two moisture contents of the laminates. The following parameters were identified as a critical combination for cracking: laminate with a low cracking resistance according to the EN 438-2 test in combination with a non-hygroscopic mineral-based carrier board, increased moisture of the laminate before being glued on the board, and the use of PVAc adhesive.

High-pressure laminates with fully embedded printed devices for healthcare applications

This article by the Portuguese research centre CeNTI reports on new furniture solutions comprised of disruptive products with integrated smart functionalities, such as printed sensors to monitor physical parameters that influence the quality of sleep and functional decorative features

Optimization of High-Pressure Laminate Manufacturing Process by Taguchi Method

The manufacturing process of High-Pressure Laminates was investigated using a strong optimization tool, the Taguchi method. High pressure laminates consist of various types. Each type has specific manufacturing process and uses. One of the utmost and crucial types of High-Pressure Laminate is Electrical Bakelite Sheet or industrial grade sheet. Electrical Bakelite Sheet is mainly used in Transformer as an insulated material. The Taguchi method was used to enhance the quality of the product and optimized the manufacturing process of Electrical Bakelite Sheet. Baking Time, Temperature, Resin Content, Pressure and Volatile Content are factors of industrial grade sheet manufacturing process and responses of these factors are electrical Insulation and thickness. Optimal value of these factors for the process are obtained through Taguchi method and found experimentally. As a result, the Taguchi technique is used to explore the effects of various electrical Bakelite Sheet parameters on responses such as electrical insulation and thickness. Pressure, Temperature, Volatile Content, Resin Content, and Baking Time are the factors which should be considered for the experiment. The Taguchi L27 orthogonal array is used for testing. The significant factors for responses of the electrical Bakelite Sheet are identified using analysis of variance (ANOVA). Determination of the significant factors value resulted in best achieving yield of the product.

High pressure laminates reinforced with electrospun cellulose acetate nanofibers

In the work, the non-woven cellulose acetate (CA) nanofiber mats were prepared via electrospinning, and CA nanofiber were incorporated into the core layer of the high-pressure laminates (HPLs). When the concentration of CA was 16 wt%, SEM images demonstrated that the morphology of the CA nanofiber mat was the best, with an average diameter of 654±246 nm. When CA nanofiber mats were incorporated into the core layer of HPLs, the mechanical properties of the resulted HPLs composites were significantly improved. Specifically, the tensile strength and elongation at break of the nanofiber mats reinforced HPLs composites increased remarkably to 40.8 ±1.1 MPa and 27.9 ± 0.9 %, respectively, which were nearly 6 times and 4.4 times higher than those of the pure HPLs. Furthermore, the incorporation of the CA nanofiber mats also significantly improved the flame retardancy of the HPLs, which was revealed from the thermogravimetric analysis (TGA) results.

Resin and volatile content of melamine-impregnated paper assessed by near infrared spectroscopy, a simulation of the industrial process using a laboratory-scale gantry

Melamine-impregnated paper is an important component in the production of high pressure laminates and melamine faced boards. The two most vital quality control parameters assessed during the production of impregnated paper are resin content and volatile content. This work explored the creation of near-infrared (NIR) reflectance models to assess these parameters. A laboratory scale computer-controlled high-precision table gantry was also tested for two reasons: to create an NIR profile of an impregnated paper sample, and to calibrate NIR models by moving the probe using the gantry while taking a spectrum. The NIR profile obtained using the gantry reveals that distinct spots on the surface of the paper have different NIR spectra. The use of the gantry for model creation shows similar or improved performance when compared to taking triplicate spectra of a sample on discrete areas. The time taken for sample analysis also was lower with the use of the gantry because only one spectrum was needed, instead of three. The gantry also enables the creation of models to be used at an industrial scale, allowing an increased range of reference values while not depending on the industrial process. The method can be used to improve reflectance NIR models of samples with heterogeneous or rough surfaces.

Impact of condensation degree of melamine-formaldehyde resins on their curing behavior and on the final properties of high-pressure laminates

Melamine-formaldehyde is the most common resin used in the production of high-pressure laminates and low-pressure laminates (melamine impregnated paper), due to its properties of durability, good fire, and heat resistance and good moisture resistance. High-pressure laminate is a common choice for horizontal and vertical applications in the construction and furniture industries, thanks to its durability and versatility. The manufacture of such laminates commonly starts with the impregnation of decorative and kraft papers with thermosetting resins and after a drying process, the impregnated paper sheets are bonded together by high pressure and temperature pressing. The aim of this work was to evaluate the influence of the melamine-formaldehyde resins condensation degree after synthesis on high-pressure laminates performance. For that purpose, melamine-formaldehyde resins with different condensation degree were synthetized and characterized. Fourier-transform infrared–attenuated total reflection spectroscopy and dynamic mechanical analysis were used to study the chemical and mechanical cure of melamine-formaldehyde resins. Melamine-formaldehyde condensation degree has shown to have influence on resin pot-life, on characteristic reaction temperatures, on the degree of cross-linking achieved, and finally on the surface quality of high-pressure laminates.

Fire performance evaluation of cladding wall assemblies using the 16‐ft high parallel panel test method of ANSI/FM 4880

SummaryCladding assemblies are façade systems made of cladding panels such as aluminum composite materials (ACMs) and high‐pressure laminates (HPLs), and layers of continuous insulation (CI) and weather resistive barrier (WRB). Recent incidents of catastrophic fires involving cladding assemblies have warranted efforts to understand their fire hazards and develop engineering risk mitigation guidelines for existing constructions. This research provides a comprehensive fire performance evaluation of cladding assemblies exposed to realistic fire scenarios. Twelve cladding assemblies, with a combination of four types of claddings, four types of CIs, and two WRBs are selected. The tests are conducted using the 16‐ft (4.9 m) high parallel panel test (16‐ft PPT) method of ANSI/FM 4880 standard; the method imparts realistic >100 kW/m2 heat flux to the wall assemblies. The results show that the chemical heat release rate (HRR) based evaluation criterion used in the 16‐ft PPT provides an objective and robust assessment of fire performance. The wall assemblies comprising of thermoplastic‐core ACMs demonstrated accelerated flame spread within a matter of a few minutes, regardless of the combustibility of the CI used. At low heat flux exposures, unlike severe fire scenarios of the 16‐ft PPT, it is shown that the thermoplastic‐core ACMs appear to perform favorably. The fire‐retardant ACM and HPL assemblies reveal limited flame spread, regardless of whether the CI used in the assembly was charring combustible or noncombustible. Lastly, for the assemblies evaluated, the flammability of claddings exhibits greater influence on the overall performance of the wall system, while the CI and WRB affect the system performance in a secondary manner.

Flammability trends for a comprehensive array of cladding materials

The flammability of materials is a key component of modern cladding fires. Vertical flame spread is a complex phenomenon which is, amongst others, a function of thermal inertia, ignition temperature, and heat release. The recently published Cladding Materials Library contains the needed flammability data to help engineers perform fire risk assessments on buildings. Cladding fire research has previously generally focused on expensive and time consuming full-scale testing, or on the chemical composition, with little regard to the flammability or other performance metrics. This research shows common trends in the ignition and burning behaviour for cladding materials in a systematic bench-scale study using the Cladding Materials Library. The organic content is shown to be a poor indicator of the fire performance, as represented by the heat release rate. A simple and highly conservative model indicates the relative behaviour of a diverse range of cladding materials. This analysis supports competent engineers to select which specific buildings require further investigation based on performance, and to aid development of remediation solutions. The differences within categories of materials, e.g. high-pressure laminates, are large and thus the performance should be tailored for the specific building material. This work complements but does not replace full-scale system testing.

Impregnated Paper-Based Decorative Laminates Prepared from Lignin-Substituted Phenolic Resins

High Pressure Laminates (HPL) panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde (PF) resins. An important requirement for such PFs is that they must rapidly penetrate and saturate the paper pores. Partially substituting phenol with bio-based phenolic chemicals like lignin changes the physico-chemical properties of the resin and affects its ability to penetrate the paper. In this study, PF formulations containing different proportions of lignosulfonate and kraft lignin were used to prepare paper-based laminates. The penetration of a Kraft paper sheet was characterized by a recently introduced, new device measuring the conductivity between both sides of the paper sheet after a drop of resin was placed on the surface and allowed to penetrate the sheet. The main target value measured was the time required for a specific resin to completely penetrate the defined paper sample (“penetration time”). This penetration time generally depends on the molecular weight distribution, the flow behavior and the polarity of the resin which in turn are dependent on the manufacturing conditions of the resin. In the present study, the influences of the three process factors: (1) type of lignin material used for substitution, (2) lignin modification by phenolation and (3) degree of phenol substitution on the penetration times of various lignin-phenolic hybrid impregnation resins were studied using a complete twolevel three-factorial experimental design. Thin laminates made with the resins diluted in methanol were mechanically tested in terms of tensile and flexural strains, and their cross-sections were studied by light microscopy.

Modified melamine-formaldehyde resins improve tensile strength along with antifouling and flame retardancy in impregnation of cellulose paper.

In this study, polyvinyl alcohol (PVA) and benzoguanamine (BG) modified melamine-formaldehyde (MF) resins were used to prepare two high-pressure laminates (HPLs) as well as a pure cellulose paper laminate and core sandwich laminates with the core material of aramid paper (AP) or polypropylene non-woven fabric (PPNF). The tensile strength, flame retardancy and antifouling properties of the modified MF resin laminates were studied and compared with the MF resin laminate. The tensile test results showed that the MF resins modified with BG and PVA improved the tensile strength of the impregnated paper. In comparison with pure kraft cellulose paper laminates, the aramid paper core laminates displayed comparatively higher tensile strength. Antifouling test results indicated that modified MF resin laminates had no obvious change while the MF resin laminate was stained. Thermal stability of the modified resins was investigated by thermogravimetric (TG) analysis and the results showed that the char yield of modified MF resin was higher than that of the unmodified MF resin due to the addition of BG. The modified MF resin laminates exhibited better flame retardancy properties through the analysis of limiting oxygen index (LOI), vertical burning and cone calorimetry (CONE) compared to the MF resin laminate. In addition, the flame retardancy of laminates was further enhanced when prepared with core materials of aramid paper. Scanning electron microscopy analysis of residue char after CONE tests showed that the AP-core laminate formed a dense and stable char layer compared with the loose char layer of the PPNF-core laminate. This study shows a new direction to develop sustainable high-performance flame retardant laminates for commercial decoration application.

Improving hydrophobic and oleophobic performances of high-pressure laminates

High-pressure laminates are decorative materials that are widely used in furnishing and building industries. One of their major handicaps, especially in the case of high gloss laminates, is the ease of staining by fingerprints. This problem can a priori be minimized by increasing the hydrophobicity and oleophobicity of the surface. To improve hydrophobicity, the chemical composition of the resin used for impregnation of the laminate’s top layer decorative paper was modified. A melamine-benzoguanamine-formaldehyde resin was used as starting point, and caprinoguanamine was added as a comonomer at different stages of the synthesis. Addition at the end of the synthesis process showed to be the most promising approach for achieving a water contact angle of 91.2°, while the contact angle for a commercial laminate, impregnated with a standard melamine–formaldehyde resin, is 58°. Regarding oleophobicity, several commercial additives were tested with the previously formulated resin. A fluorocarbon additive showed the best result, leading to contact angles of 114° for water and 76° for an artificial fingerprint liquid. In addition, it was shown that fingerprints were easier to clean from the modified laminate surface.

HPL-GEM: controlling High Pressure Laminates bulk resistivity with GEMs

We succeeded in modifying and controlling the electrical resistance of a standard High Pressure Laminate (HPL) panel through the use of a Gas Electron Multiplier (GEM) foil that has been embedded into the bulk of the HPL plate itself. Electrical characterizations were made and preliminary data show that this HPL-GEM embedded system can easily vary its bulk resistance by more than one order of magnitude. Data show that the bulk resistance change is exponential with the applied voltage to the embedded GEM.

Властивості личкованих деревинно-полімерних матеріалів плоского способу пресування

Досліджено процес личкування деревинно-полімерних матеріалів (ДПМ) плоского способу пресування. Личкування ДПМ здійснено одночасно з їх пресуванням. Для личкування використано декоративний ламінат високого тиску (HPL) товщиною 0,5 мм. Як клей для приклеювання HPL використано поліетиленову (ПЕ) плівку або вторинний поліетилен низької щільності (ВПЕ). Для порівняння виготовлено личковані ДПМ без використання клею для приклеювання HPL. Встановлено, що тип клею не має істотного впливу на механічні показники ДПМ. Межа міцності під час статичного згинання у разі використання ВПЕ зростає на 14%, а у разі використання ПЕ плівки – на 24%, порівняно із личкованими ДПМ без використання клею для приклеювання HPL. Аналогічні залежності спостережено і для модуля пружності під час статичного згинання. Тип клею для приклеювання HPL також не має визначального впливу на межу міцності під час розтягування перпендикулярно до площини плити. Набрякання за товщиною значно зменшується із використанням клею, особливо це проявляється під час занурення взірців у воду на 24 год. У разі використання ПЕ плівки та ВПЕ отримано практично однакові результати набрякання за товщиною, як за 2, так і за 24 год занурення.

Paper-based laminates produced with kraft lignin-rich phenol\u2013formaldehyde resoles meet requirements for outdoor usage

Suitability of lignin–phenol–formaldehyde (LPF) resoles was investigated for manufacturing paper-based high-pressure laminates. As lignin source, pine kraft lignin and spruce sodium lignosulfonate were compared, substituting 40 wt% of phenol by lignin in each case. The synthesized resins were characterized for their viscosity development, solid content, pH, free formaldehyde as well as free phenol content and B-time. Paper-based high-pressure laminates were manufactured using the two different resins. The laminates were exposed to different test climates and were compared for boiling water resistance, thickness swelling, bending properties and impact energy. The results indicate that pine kraft lignin performs superior to spruce sodium lignosulfonate for utilization in paper based laminates for outdoor usage due to a lower affinity of the pine kraft LPF laminates to water.