How to Enhance Plain Weave Fiberglass Window Screens' Tearing Strength

Plain weave fiberglass window screens adopt single fiberglass yarn which is covered by vinyl resin are shaped after weaving and thermosetting. They have the advantages of good ventilation, anti-UV performance, environmental protection, easy to clean, long service life, heavy-duty corrosion protection and fire retardance, etc. Being quality products, plain weave window screens are widely used in living rooms, ecological agriculture, outdoor swimming pools, gardens, orchards, pastures and so forth to prevent insects, resist natural disasters and ultraviolet rays. In recent years, with the continuous improvement of the processing machinery and automation level of the downstream users of the window screen, users demand more of fiberglass plain weave window screens, such as thinner, harder and more environmentally friendly. However, many of plain weave window screens in the current market, have large color chromatic aberration and poor tear strength. In order to adapt to market demand, this thesis will discuss how do the fiberglass content, filament diameter and the adoption of coating materials influence the plain weave window screens' tearing strength.

PWFWS-01: Plain weave fiberglass window screens adopt single fiberglass yarn which is covered by vinyl resin

PWFWS-02: Plain weave window screens' tearing strength is influenced by many factors.

There are three main factors which influence plain weave window screens' tearing strength greatly: fiber reinforced materials, matrix materials and the combination of these two parts.

The impact of fiber reinforced materials on plain weave window screens' tearing strength

• Diameter of yarn and twist inserted
  Plain weave window screen with fine diameter, high twist inserted and high density, has poor permeability of coated PVC resin. On the contrary, low twist inserted which causes poor saturation will make the center position of the coated yarn be offset and have effect on coating. In order to improve the appearance and chromatic aberration of plain woven screen, many production enterprises generally increase the thickness of coated resin and reduce the number of fiber. By doing this, the content of fiberglass can be reduced and plain weave window screens' tearing strength can be enhanced.
• Size
  Fiberglass yarn with high solid content often become sticky in summer. Due to low technical level, some window screen production enterprises usually reduce the content of fiber size to solve this problem. Therefore, the lack of soft and lubricated parts of fiberglass yarn cause poor wear resistance and processing performance, thus, affecting plain weave window screens' tearing strength. In addition, the content of coupling agent in size directly influence interfacial strength, transfer effect and the combination of paste resin and fiberglass, then influence plain weave window screens' tearing strength.
• The impact of matrix materials on plain weave window screens' tearing strength
  • When not add or add little grease, paste resin has poor lubricity which damage the fiber during single coated processing. Besides, enterprises, in order to reduce costs or meet some functional needs, add a large variety of fillings and resin with large particle. In the shrinking space of molds, the reflux of fillings and resin with large particle will increase the friction and cutting force of fibers and molds and damage fibers directly, then influence plain weave window screens' tearing strength.
  • The quality of paste resin and added plasticizer influence plain weave window screens' tearing strength directly. Usually, low-grade resin and plasticizer will cause poor combination of paste film and fiber, which can not strengthen and protect fiber. Window screens should be kept in a closed environment, otherwise plastic will appear aging and micro-crack phenomenon and moisture will intrusion into fibers, causing tearing performance degradation.

Selection of filler and mixed resin

• Filler
  • Filler addition principle
    Abroad, plain weave window screens generally do not add filters, only if have requirements on some special characters, such as flame retardant, cover and harden. However, domestic window screen enterprises add some filters which play a role in covering and coloring, in order to reduce cost. The principle of filler addition is that do not choose the material damage the performance of paste and fiber, and there should not be angular, hard part and large particulate matters. Thus, it is better to choose nanometer material as filter.
  • Selection of filter
    • Titanium oxide: white pigments, refractive index is 2.76–2.55, good cover performance. Because of big friction and cutting effect, the tensile strength of fiberglass is significantly reduced. Thus, titanium oxide is not suitable as plastic coating for fiberglass window screens.
    • Zinc sulfide: white pigments, relatively soft, low friction. Zinc sulfide is suitable for plastic coated processing of fiberglass yarn and can be replaced by Zinc oxide.
    • Antimony oxide: white pigments, inflaming retarding.
    • Calcium carbonate: Mohs rating of 3, refractive index is 1.59. As a low-cost filter, calcium carbonate has slight whitening effect.
• Mixed resin
  Mixed resin is a kind of PVC resin which is used to replace partial paste resin. Adding a percentage of mixed resin to paste resin can efficiently reduce viscosity and expansion, improve the degassing performance and storage stability of plasticized paste and reduce cost.
  You'd better choose mixed resin whose average size of particles ranges from 15 to 25 μm. Generally, 100 g viscosity reducing resin can absorb plasticizing dose from 11 to 15 g, which is 50% lower than the common paste resin plasticizer demand. After swelling, the external diameter of partials can be controlled in 60 to 70 μm, while the friction of partials is not too big to block molds, damage fiber and affect the operation of the coated process

The key production control of plain weave window screens

• According to national standard and production requirement, fiberglass yarns which are used to single coated processing should reasonably control its diameter and thickness, in order to ensure good strength and folding resistance of window screens. Twist inserted is controlled in 35 to 50 twist to improve the performance of fiberglass and make it adapt to higher requirements.
• In order to meet requirements of tearing strength, the content of size and lubricant, film forming agent and coupling agent should be control. Commonly, the content of size in plastic coated window screens can not be less than 10%.
• The finer diameter of particles in size is better and nanometer are the best. Filter should be pre-activated to increased dispersion and mobility. Excessive filter will not only increase the cutting and friction to fiber but also influence paste's performance. The content of particle in paste should be strictly controlled in 10% to 20%, or it will influence paste's protection of fibers.
• Resin and plasticizer used to make paste must possess good film-forming properties and anti-aging requirement. Paste with certain lubrication components is propitious to reduce the wear of the mold. The diameter of the mixed resin particles should be controlled in 40 μm.

To enhance plain weave window screens' tearing strength efficiently, producers should control the content of fibers and improve the performance of fibers.