PU foaming body having double foaming function
PU foam product, its manufacturing process is very ripe, and its operation strategies widely, mainly contains following field:
Sponge and flexible package: belong to soft bubble, its density is generally 15-80 grams per liter;
Heat-insulation and heat-preservation: as refrigerator, refrigerator, freezer and thermal insulation tile etc., its hardness is between soft or hard bubble, and its density is generally 30-100 grams per liter;
Ornament materials: the ornament materials of various imitative wood, imitative stone continues to bring out in recent years;
Inner structure supporter before unsaturated-resin fibre is shaping: as ships and light boats and the shaping front inner structure of various fibre support, require that its density is generally 40-200 grams per liter in order to have hard bubbling of certain physical strength.
The auxiliary inner core of carbon fiber hot press form technology: carbon fiber epoxy prepreg cloth is wrapped in outside PU inner core, then enters mould heat pressure shaping.
In the moulding process that carbon fiber is many, the hot press forming technology of carbon fiber epoxy prepreg cloth has the highest fibre strength conversion ratio, and its manufactured goods have the incomparable intensity of other techniques.Therefore, as long as condition license (such as manufactured goods external form comparison rule and need mould is not very huge), generally select carbon fiber hot press forming technology.
Current most carbon fiber hot press forming technology is interior inflatable, if but the out-of-shape of manufactured goods outward appearance, then must first manufacture shaping inner core, then paste carbon fiber epoxy prepreg cloth outward at inner core, then it is shaping to enter mold heated.
Inner core material main at present and pluses and minuses as follows:
EPS (foamed styrene): cost is low, but the thawing that can bounce back after heating, therefore only help out, will overlap nylon tube inflation again outside it, it is typically used in bicycle frame of carbon fiber and wheel rim.
Traditional PU foaming: have slight expansion (less than 2%) after heating, available reluctantly, but effect is bad, can not do the high-precision article of high strength.
PMI (i.e. polymethyl acid imide foaming body): from German import (domestic immature), expensive, because of the restriction of cost, current uses in space flight and aviation and military supplies.
Above three kinds of materials are inner core foaming bodies the most frequently used at present, but still each own obvious shortcoming, object of the present invention is exactly develop the inner core made new advances, and solves the shortcoming of the shaping inner core of current carbon.The principle of its second time of foaming is as follows:
Assuming that the proportion of PU black and white material and foaming micro mist is all 1g/ml (reality is also similar), the foaming micro mist of 5% is added in the black and white material of PU foaming, after one step foaming, its proportion becomes 0.1g/ml (namely its volume of one step foaming amplifies 10 times); Again supposition foaming micro mist through heating post-expansion rate be 50 times (being generally 40-80 doubly), then the micro mist second time of foaming that foams to the contribution rate of whole volume after one step foaming is: 5%*50/10=25%.
In fact, for the inner core of size comparatively large (its unidirectional internal diameter size is more than 50mm), the frothing percentage of 10% can contribute the foaming size of 5mm, can obtain good effect to the carbon moulded products of external mold hot pressing; Its result of use of the frothing percentage of 25% is better, can reach the requirement of the hot-forming foaming inner core of external mold of any size.
Certainly, consider the facility of operation, cost and board mould bearing strength, the multiplying power of second time of foaming controls between 10-25% more satisfactory, and namely desirable second time of foaming micro mist addition is 2-5%.
Summary of the invention
The technical problem to be solved in the present invention is, for the defect on the molded inner core material of existing carbon fiber thermal, provides a kind of new foaming inner core, it is convenient that it has operation, manufactured goods weight is low and intensity is high, low cost and other advantages, has boundless utilization prospect.
The present invention adopts following technical scheme: in common PU foam raw material (containing white material and black material two component), add blowing agent, after blowing agent stirs in black material or white material, shaping through normal PU foam process one step foaming in mould.
Above-mentioned common its main component of PU foaming raw material is: polyurethane (being commonly called as black material) and polyalcohol (being commonly called as white material), the proportion after its one step foaming is generally 40-200 grams per liter.
Above-mentionedly evenly be mixed in blowing agent in a PU foaming body through heating post-foaming, blowing agent can be foaming micro mist or other blowing agents, and its blowing temperature is 80--250 DEG C; Expansion ratio 40-200 doubly.
The addition of above-mentioned foaming micro mist in whole system is 1-10%, and the multiplying power of the second time of foaming of its PU inner core is 4-50%.
Product of the present invention can be used as carbon fiber or the hot-forming inner core of glass fibre, for the machine-shaping of carbon fiber or glass fibre provides a kind of new technique, there is extremely wide utilization prospect, and it is convenient to have operation, manufactured goods weight is low and intensity is high, low cost and other advantages.