Provided is a sealant sheet that is handled as a laminate with a release liner and can be cured by photoirradiation through the release liner. The release-linered sealant sheet has a photo-curable sealant: sheet, and a release liner placed on at least one face of the sealant sheet. The release liner has a light transmittance of 20% or higher in the wavelength range from 350 nm to 450 non.

Provided is a sealing method that uses a photo-curable sealant sheet. The sealing method provided comprises, in the following order, a step of obtaining a photo-curable sealant sheet, a step of subj ecting the sealant sheet to photoirradiation, and a step of applying the sealant sheet to a target object.

A polythioether prepolymer including functional groups capable of being obtained by the reaction: of at least one compound T having a number f of thiol functional group number selected from 2, 3, 4 and 6, with at least one compound E having a number g of epoxy functional groups number selected from 2 and 3. Also, a method of preparation for this prepolymer, a composition including this prepolymer and an oligomer as well as its use as a mastic and a polythioether polymer obtained from this polythioether prepolymer with an oligomer.

Polysulfide compositions having a polyether synergist are disclosed. Polysulfide compositions that contain polyether synergists exhibit a rapid onset of cure and have acceptable final properties. The polysulfide compositions can be used as sealants.

Provided is a sealant sheet that shows reduced elongation during application to a target object. A laminate comprising a sealant sheet is provided. The laminate has a support layer satisfying the formula (1): E′×t≥1×10.sup.4 (N/m). In the formula (1), E′ is the support layer's modulus (MPa) and t is the support layer's thickness (μm).

Polythioether prepolymers that have a low nucleation temperature. The symmetry of the polythioether prepolymers is modified by including pendent groups extending from the backbone of the polythioether prepolymer chain and/or the symmetry is modified by including segments having a different number of —C(R).sub.2— groups between heteroatoms. The polythioether prepolymers are stable at low temperature storage conditions for an extended period of time. Compositions prepared using the low nucleation temperature polythioether prepolymers are useful as sealants.

Polythioether prepolymers that have a low nucleation temperature are disclosed. The polythioether prepolymers are stable at low temperature storage conditions for an extended period of time. Compositions prepared using the low nucleation temperature polythioether prepolymers are useful as sealants.

Urethane/urea-containing bis(alkenyl) ethers can be incorporated into the backbone of polythioether prepolymers and can be used as curing agents in thiol-terminated polythioether prepolymer compositions. Cured sealants prepared using compositions containing urethane/urea-containing bis(alkenyl) ether-containing polythioether prepolymers and/or urethane/urea-containing bis(alkenyl) ether curing agents exhibit improved physical properties suitable for use in aerospace sealant applications.

Improved polysulfide sealant formulations, application of such sealants, and methods for reducing the density of polysulfide sealant formulations are disclosed.

Hydroxyl-containing bis(alkenyl) ethers can be incorporated into the backbone of polythioether prepolymers and can be used as curing agents in thiol-terminated polythioether prepolymer compositions. Cured sealants prepared using compositions containing hydroxyl-containing bis(alkenyl) ether-containing polythioether prepolymers and/or hydroxyl-containing bis(alkenyl) ether curing agents exhibit improved physical properties such as rapid curing and compatibility with fillers suitable for use in aerospace sealant applications.