A pre-stressed pultruded glass fiber reinforced thermoplastic lumber suitable for demanding construction environments, particularly marine and outdoor applications, features a solid core composed of a thermoplastic, such as PVC, blended with 15% to 40% by weight of pelletized chopped strand glass fibers. Pre-tensioned elongated continuous fiber reinforcements are embedded within and coextensive with this core via pultrusion. The presence of pelletized and fragmented glass fibers within the core enhances the mechanical coupling between the core and the continuous reinforcements, facilitating the transfer of tensile stress to the core as compressive pre-stress. An outer co-extruded cap stock provides protection against UV and IR radiation and enhances impact resistance. The resulting lumber exhibits a high modulus of elasticity (exceeding 800,000 psi), at least 60% fiber length retention, improved durability, and resistance to common wood degradation factors without the use of toxic chemicals.

A synthetic resin skin material, including a base cloth and a vinyl chloride resin skin layer that is formed on the base cloth and that includes a vinyl chloride resin having a degree of polymerization of 1,600 to 3,000 and includes 3 parts by mass to 20 parts by mass of a silicon-acrylic copolymer with respect to 100 parts by mass of the vinyl chloride resin, and a manufacturing method thereof.

A method of manufacturing a product includes forming a first mixture of PVC fragments and cellulosic fragments, heating the first mixture at a temperature and duration sufficient to melt at least a portion of the PVC fragments, and cooling the first mixture until the melted PVC fragments resolidify.