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Moisture-dominated cure adhesives (e.g., silicone sealant) are an important source of volatile organic compound (VOC) emissions indoors, particularly in newly decorated buildings. Understanding their emission behavior could aid in selecting better control strategies for acceptable indoor air quality. In this study, a one-dimensional emission model that can predict the entire VOC emission process from moisture-dominated cure adhesives was established. The model has distinct physical or chemical parameters; thus, the model can be readily scaled up and the effects of environmental factors, such as temperature and humidity, can be evaluated. The emission of a type of neutral silicone sealant was measured using an environmental chamber and the main emission VOC (2-butanone oxime, MEKO) was used to validate the model. The model parameters of neutral silicone were measured or estimated to predict the concentration in the chamber. The experimental data and model predictions agreed well. The study indicates that MEKO emission is strongly coupled with the curing process. The factors that can influence the cure reaction are also the main influencing factors on the MEKO emission process.

Silicone sealant is usually interposed between panels of precast facades. In ordinary cladding panel configurations, relative sliding between panels occurs under lateral actions. The shear drifts and consequent stresses arising in the silicone strips may lead to a significant increase of the load demand in the cladding panel connections and affect the seismic behaviour of the structural system. This paper presents the results of experimental tests and numerical analyses carried out to clarify the role of the silicone sealant on the seismic response of precast structures with cladding panels. An experimental campaign including monotonic and cyclic tests on both silicone strips applied to small concrete blocks and two panel sub-assembly sealed with silicone, has been developed at Politecnico di Milano. Furthermore, cyclic and seismic pseudo-dynamic tests on a full-scale prototype of precast building with cladding panels sealed with silicone, have been performed at the Joint Research Centre of the European Commission. The results of the experimental tests are presented and compared with the results of numerical simulations. Some recommendations for seismic design of precast frame structures with cladding panels, considering the effect of silicone sealant, are finally provided.

The paper presents results of research on emission profile of butan-2-one oxime (methyl ethyl ketoxime, MEKO) released from two types of commercially available neutral silicone sealants: silicone type ‘S’ and silicone type ‘T’. To determine the emissions from silicone samples, the system consists of a stationary emission chamber, and the thermal desorption-gas chromatography-mass spectrometry system was applied. First, the research aimed to describe the emission profile of butan-2-one oxime considering different methods of application of silicone caulk: separate strips, merged strips, and dotted. Silicone sealant was applied in these three different ways to produce varying surfaces. As a result, significant differences in the emission profile were observed for the different methods of silicone application. The greatest difference in the emission rate was found to be between those of the dot shape and those of the separate strips; the emission rate was approximately five times smaller for dot shape. Moreover, the studies focused on quantitative emissions of butan-2-one oxime over a set time period. The research results indicate that, in the emission process of butan-2-oxime from a neutral silicone sealant, there are three main stages of emission. The first stage is dynamic emission, occurring during the first few days after application. The second stage is declining emission, and the third stage is stable residual emission. Between the first and third stages, the amounts of emitted oxime differ significantly. The difference in the emissions of butan-2-one oxime between the first and last stages of emission ranged from factors of 100–1000.

With the aid of current sealant technologies, a double sealant comprising adjacent silicone and polyisobutylene sealants may be used to enhance the durability of buildings. The inner silicone sealant is quite durable owing to its intrinsic properties, and covering it with an outer polyisobutlylene sealant prevents fouling due to silicone sealant. This study indicates that the fatigue resistance of double sealant joints is strongly correlated with both the total sealant depth and the movement intervention of each sealant. Furthermore, the proposed section dimension factors enable the design of sealants with appropriate section sizes through better prediction of the fatigue resistance.

A novel sealant testing device was used to continuously monitor the mechanical properties of a one-part silicone sealant for movement cycles initiated from 10 to 168 h after sample creation. These cure times fall between the proposed RILEM TC-139 technical recommendation of 5 min and the ASTM C719 standard of 21 days. At 10 h of cure, enough crosslinking occurred before testing such that neither the overall movement history of the sample nor the deformation step shapes affected subsequent curing of the sealant. A critical parameter for sealant performance appears to be the extent of cure at the onset of movement. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

The use of blends of silicone sealant and methyl methacrylate adhesive as an impregnating composition allows increasing the strength characteristics and lifetime of electric heaters by two times. The modular design of the electric heaters allows easily regulating the maximum thermal capacity of the heater by connecting the required number of resistive sections. Metallization of CF at current supply contact sites decreases electric losses by 2.5 times. Use of basalt materials increases the insulating characteristics of an article by 1.5 times, which ensures its reliability and longevity.

Water uptake in different regions of the sweet cherry fruit (Prunus avium L. cv. Sam) was investigated following selective application of silicone sealant to the pedicel end, pedicel cavity, pedicel/fruit juncture, or stylar scar of detached fruit. The time course of water uptake was monitored gravimetrically during a 3-hour incubation period in deionized water (20 °C). Sealing the pedicel end and/or pedicel/fruit juncture significantly reduced rates and total amount (3 hours) of water uptake, but sealing the stylar scar had no effect. The amount of water penetrating via the pedicel/fruit juncture increased between 50 and 85 days after full bloom. During the same period the maximum force required to detach pedicels from fruit (fruit removal force) fell from 5.2 ± 0.5 to 2.1 ± 0.2 N. The amount of water penetrating via the pedicel/fruit juncture and the fruit removal force were negatively related. Nuclear magnetic resonance (NMR) imaging of mature fruit incubated in D2O indicated that D2O accumulated in the pedicel cavity region and the pedicel. Our data suggest that the pedicel end and pedicel/fruit juncture, but not the stylar scar, are regions of preferential water uptake in detached fruit. Chemical name used: deuterium oxide (D2O).

Glass beam-like elements are largely used in building structures in the form of primary load-bearing members. Large studies recently focused on specific structural behaviours under various loading and boundary conditions. Lateral-torsional buckling (LTB) of beams, in particular, has been largely investigated through experiments and simulations. Based on previous works of literature, the paper focuses on the strengthening effects of structural silicone joints on the global LTB response of glass beams. Analytical and numerical calculations are performed on various glass beams, in order to highlight the effects of continuous lateral restraints on their critical buckling moment. Shear tests are performed on small silicone sealant joints. Interesting correlations are found between joint properties and beams geometry.

We present 2 cases of men that have inserted silicone seal-ant into their urethras. One man had ingeniously tried to use the silicone to remove a urethral foreign body he had inserted some months earl

A method has been devised for measuring the diffusion coefficient D of additives that act as adhesion promoters and crosslinking agents in uncured silicone sealants. This has been used to measure D for tetra-t-butyltitanate (TBT) and isobutyltrimethoxysilane (BTMS) in a sealant at 25°C. The value of D for TBT was found to be constant but that for BTMS decreased with the duration of the experiment, possibly due to the interaction of the silane with the silica particles.

This paper reports on the state-of-the-art test methods and qualification procedures for ssg sealants currently applied in Europe and compares them to the ASTM C-24 proposal. The test data generated show that the 50°C water immersion required by some European building code authorities results in a much lower success rate in the adhesion test than the 1 week room-temperature immersion applied by silicone sealant manufacturers in the USA. The paper also describes the efforts to consolidate the different national test and requirement standards into one European standarrd and directive on structural glazing.

Finite element analysis (FEA) was used to predict stresses and strains in a 6 mm x 6 mm structural silicone joint on the edge of an overhead piece of glass. The project was undertaken because of a marketplace report that this particular type of joint was showing field leaks after 5--10 years of service. FEA was used to show the stresses and strains in the nominal joint design under negative wind uplifts. After a three dimensional FEA model of the skylight system was completed, the deformations in the model were used to load a series of two dimensional FEA models of the silicone bead. The two dimensional bead models were completed at repeated intervals down the span, providing a finer mesh for recovering stresses and strains. All stresses and strains in this model were shown to be well within the working range of the silicone sealant properties. It was concluded that the field leaks were not due to excessive strains and could possibly be due to installation issues, mechanical damage or improper joints resulting from construction tolerances.

Field-applied bridge or band-aid joints have had limited use for many years, and shop molded, preformed silicone sealants have been used on a very limited basis in the US for less than 10 years, primarily in remedial work. Two major sealant manufacturers have recently introduced preformed silicone sealant tape for application as bridge joints. These materials, though relatively expensive compared to typical wet-applied sealant joints, are well suited for use on many remedial projects. Several recent applications are discussed, and specific joint configurations are described. Advantages and disadvantages are presented, and recommendations for use and application are made.

The effects of heat ageing on the elongation at break and tensile strength are studied for ten commercially available, standard construction silicone sealants, based on acetoxy, alkoxy, aminoxy and oxime cure. Mechanical properties are measured on ISO 8339 tensile test joints after exposure to 100, 150, 180 and 200°C as well as room temperature (as a control) over a period of one, three and six months. The study show that the heat staibility of thos one-part silicone sealants investigated is influenced mainly by their cure chemistry and only to a lesser extent by their formulation. A relative ranking of the heat stability of the sealants is derived based on the percentage change of their mechanical properties.

Silicone sealant structural glazing, whether conducted in the field or the factory, requires good workmanship and quality materials. While the same basic construction steps are followed for both methods, the details of how the work is done vary. This paper discusses joint design, sealant selection, surface preparation, and quality testing for structural silicone glazing, comparing shop and field glazing at each step.

Industry-wide standards for the performance of silicone sealants need to be established to ensure the continued integrity of silicone sealant structurally glazed projects. The first step in establishing such standards is careful research into the behavior of silicone sealants under different conditions. This paper reports two major tests, one using mock-up panels and simulating field conditions, the other scrutinizing sealant properties in a laboratory setting. The results offer a greater understanding of silicone structural sealants and a foundation for developing standard test methods and setting industry performance standards for structural sealants.

Insulating glass silicone secondary sealants withstand the effects of temperature and sunlight to prolong the life of insulating glass units (IGUs). They also provide structural integrity for IGUs in silicone structural sealant glazing applications. Thorough testing by the sealant manufacturer establishes the high performance of silicone sealants in various IGU and structural applications. IGU fabricators promote the performance of quality silicone sealants through careful workmanship.

Silicone sealants have been used widely in the waterproofing industry because they resist deterioration. However, residue from silicone sealant (or from pre-formed silicone seals) can be difficult to remove from adjacent surfaces, if it contacts these surfaces inadvertently from improper application or fluid run-down. This article focuses on the challenge of removing silicone residue from window glass. Several of the likely sources of the silicone residue are discussed, along with the difficulty of measuring the presence of the colorless and odorless thin residue film. The testing used commercially available cleaners and digesters to attempt to remove the silicone residue. The results were mixed and largely inconclusive; however, the test methodology developed can be used for further study by additional laboratories.

Silicone sealants have a long history of successful use in high performance windows and curtainwalls, such as structural glazing systems. With the recent threat of terrorist attacks, there has been an increased use of windows designed to mitigate the impact of bomb blasts. Due to the high strength and durability characteristics of silicone sealants, structural silicone sealants have been utilized in new bomb blast mitigating window designs. Effective bomb blast mitigating window designs allow the window system to withstand a moderate bomb blast without causing significant injury to building occupants from the blast itself or flying glass shards. The occupants are protected because laminated or filmed glass, which can withstand the blast, is attached in the framing with a silicone sealant. Silicone sealants provide unique benefits to these window designs due to their strength properties and their ability to anchor the laminated glass in the framing during a blast situation. In this paper, three commercially available high strength structural silicone sealants are evaluated at applied load velocities (movement rates) up to 5.0 m/s. These elevated load velocities are intended to simulate loads encountered during a bomb blast. Sealant joints are fabricated to evaluate the sealant in tension, shear, and combined tension and shear loads. Sealants joints are also exposed to accelerated weathering (heat, water, and artificial light through glass). Results show that the sealant strength values increase substantially at elevated rates of applied load. The paper discusses the effect of joint configuration, load velocities, and accelerating weathering on the performance and durability of the silicone sealants tested.

The durability of silicone sealants is outstanding. This valuable behavior is a direct result of the unusual organic/inorganic hybrid nature of silicones and the consequent chemistry and physics of their interaction with the environment. Responses to a variety of environmental stresses are reviewed including those associated with weathering such as ozone and temperature extremes as well as electrical stresses such as corona discharge. The emphasis is on relating this behavior to the surface and bulk properties of silicones and particularly to the low intermolecular forces and high chain flexibility that are the fundamental consequence of the unique molecular architecture of silicones. Attention is paid to aspects such as the low surface energy and poor adhesion of silicone surfaces and to dynamic effects such as surface reorientation to changing environnments.