Fig.3 sample cavity pressure profile of VAIM (2Hz):(a)pressure at P1,(b)pressure at P2,and (c)pressure difference between P1 and P2

Vibration-Assisted Injection Molding Results. The addition of  vibration  to  the  otherwise  optimized  molding  conditions  gave rise  to  significant   product  strength  improvements.  The  effects  of npidual  vibration parameters  will  be  first   discussed,  followed by  the  presentation  of  the  best  strength  enhancements  realized through VAIM  processing.
Effects  of  Inpidual  Vibration  Related  Parameters. A representative sample of the observed effect of the delay time to begin vibration  on  product  strength  is  shown  in  Fig.  4.  The  data  in  the figure  is for a 50/50 blend exposed to vibration at various frequencies for a fixed  duration after the delay. From the figure,  it can be seen  that  a  maximum  strength  was  obtained  when  the  delay  time
 
Fig.  4 Effect  of  vibration  delay  time  on  product  strength  for
50Õ50 virginÕrecycled blend
 
Fig. 5 Effect of vibration duration time on product strength for
50 /50 virgin / recycled blend
was  0  s,  or,  in  other  words,  when  the  vibration  was  introduced immediately  upon  the  start  of  injection. This  same  trend  was  observed  for  both  the  75/25  blend  and  100%  virgin  PS.
Cavity pressure traces for the molding conditions of Fig. 4 (not shown ) indicate  that  melt  vibration  is  initiated  prior  to  the  cavity being filled.  Melt manipulation during fill  alters the flow  behavior during  this  portion  of  the  cycle,  supporting  the  concept  that  the shear  stress/strain  applied  to  the  melt  is  modified,   which  could alter  the  skin  formation  in  the  molded  parts.  Control  over  skin formation  within  the  mold  is  most  likely  more  effective  early  in the  process  when  relatively  low viscosity  levels  are  present  and the  polymer  is  more  easily  manipulated.
The  information  presented  in  Fig.  5  focuses  on  the  effects  of vibration  duration  on  resultant  product  tensile  strength.  Again,data  is  presented  for  a  50/50  blend  of  recycled  and  virgin  PS which was processed at various vibration frequencies for specified duration times. For the data shown, the delay time to begin vibration was 0 s and a duty cycle level of 1.0 was uniformly applied.As can be seen, a vibration duration time of 10 s led to the strongest  products  at  each  of  the  frequencies.  This  was  also  found for the cases of the 75/25 blend and 100% virgin PS materials,  which  were  processed  into  the  strongest  products  when  vibration  duration  levels  between  9  and  11  s  were  applied. Thus,  it was  concluded  that  a  critical  amount  of  exposure  to  the  applied oscillatory  energy ~in  the  present  case  10  s! is  necessary  to  optimally  affect  the  molecular  structure  within  products. Too  little  or too much exposure to the vibrational energy, however, can reduce the  beneficial   impacts. 回收塑料材料注射成型英文文献和中文翻译(7):http://www.youerw.com/fanyi/lunwen_17270.html